SlidesLaboratoryII

Calorimetry I
Electromagnetic Calorimeters
Electromagnetic Showers
6.1 Allgemeine Grundlagen
Funktionsprinzip – 1
! Introduction
In der Hochenergiephysik versteht man unter einem Kalorimeter einen
Detektor, welcher die zu analysierenden Teilchen vollständig absorbiert. Da
durch kann die Einfallsenergie des betreffenden Teilchens gemessen werde
Calorimeter:
! Die allermeisten Kalorimeter sind überdies positionssensitiv ausgeführt, um
Detector for energy measurement via total absorption of particles ...
die Energiedeposition ortsabhängig zu messen und sie beim gleichzeitigen
Also: most calorimeters
are position
sensitive
to measure
energy depositions
Durchgang
von mehreren
Teilchen
den
individuellen
Teilchen zuzuordnen.
depending on their location ...
! Ein einfallendes Teilchen initiiert innerhalb des Kalorimeters einen TeilchenPrinciple of(eine
operation:
schauer
Teilchenkaskade) aus Sekundärteilchen und gibt so sukzessi
seine
ganze
Energie
diesen
Schauer
ab.
Incoming
particle
initiatesand
particle
shower
...
Shower
Composition and shower dimensions
depend
on
Die
Zusammensetzung
und die
Ausdehnung
eines solchen Schauers
hänge
Schematic of
particle type and detector material ...
calorimeter principle
von
der Art des einfallenden Teilchens ab (e±, Photon oder
Hadron).
Energy deposited in form of: heat, ionization,
excitation of atoms, Cherenkov light ...
Different calorimeter types use different kinds of
Bild
rechts:
Grobes
Schema
these
signals
to measure
total energy
...
eines Teilchenschauers in
Important:
particle cascade (shower)
incident particle
einem (homogenen) Kalorimeter
Signal ~ total deposited energy
[Proportionality factor determined by calibration]
detector volume
Introduction
Energy vs. momentum measurement:
Calorimeter:
[see below]
1
⇠p
E
E
E
e.g. ATLAS:
Gas detector:
[see above]
p
p
⇠p
e.g. ATLAS:
0.1
⇡p
E
E
p
i.e. σE/E = 1% @ 100 GeV
i.e. σp/p = 5% @ 100 GeV
E
p
5 · 10
4
· pt
At very high energies one has to switch to calorimeters because their
resolution improves while those of a magnetic spectrometer decreases with E ...
Shower depth:
Calorimeter:
[see below]
E
L ⇠ ln
Ec
[Ec: critical energy]
Shower depth nearly energy independent
i.e. calorimeters can be compact ...
Compare with magnetic spectrometer: p/p ⇠ p/L2
Detector size has to grow quadratically to maintain resolution
Introduction
Further calorimeter features:
Calorimeters can be built as 4π-detectors, i.e. they can detect
particles over almost the full solid angle
2
large
for small θ
2
Magnetic spectrometer: anisotropy due to magnetic field; remember: (⇥p/p) = (⇥pt/pt ) + (⇥ /sin )
2
Calorimeters can provide fast timing signal (1 to 10 ns); can
be used for triggering [e.g. ATLAS L1 Calorimeter Trigger]
Calorimeters can measure the energy of both, charged and neutral particles,
if they interact via electromagnetic or strong forces [e.g.: γ, μ, Κ0, ...]
Magnetic spectrometer: only charged particles!
Segmentation in depth allows separation of hadrons (p,n,π±), from
particles which only interact electromagnetically (γ,e) ...
...
Electromagnetic Showers
Reminder:
Dominant processes
at high energies ...
Photons : Pair production
Electrons : Bremsstrahlung
Pair production:
◆
✓
7
183
2 2
⇥pair ⇡
4 re Z ln 1
9
Z3
7 A
=
9 NA X0
Absorption
coefficient:
µ = n⇥ =
[X0: radiation length]
[in cm or g/cm2]
X0
Bremsstrahlung:
dE
E
dE
Z2 2
183
= 4 NA
re · E ln 1 =
X0
dx
A
3
Zdx
➛ E = E0 e
NA
7
· ⇥pair =
A
9 X0
x/X0
After passage of one X0 electron
has only (1/e)th of its primary energy ...
[i.e. 37%]
10 PeV
0
Electromagnetic Showers
0
0.25
0.5
0.75
y = k/E
1
Figure 27.11: The normalized bremsstrahlung cross section k dσLP M /dk
lead versus the fractional photon energy y = k/E. The vertical axis has un
of photons per radiation length.
200
dE
(Ec )
dx
Brems
dE
=
(Ec )
dx
Ion
✓
dE
dx
Brems
30
E
✓
dE
dx
EcSol/Liq
◆
Ion
10
610 MeV
=
Z + 1.24
Z ·E
800 MeV
2
5
10
20
50
Electron energy (MeV)
Transverse size of EM shower given by
radiation length via Molière radius
100
200
Figure 27.12: Two definitions of the critical energy Ec .
with:
incomplete, dE
and near y =
divergence is removed b
dE the infrared
E 0, where
Ec
=
⇡
=
const.
& amplitudes from nearby scattering cent
the interference
dx of bremsstrahlung
X
dx
X
Brems
0
Ion
February 2, 2010
[see also later]
lu
ng
Ionization
Brems = ionization
710 MeV
=
Z + 0.92
◆
Rossi:
Ionization per X0
= electron energy
50
40
20
Approximations:
EcGas
l
ta
o
T
70
ss
tr
ah
Critical Energy [see above]:
Br
dE /dx × X0 (MeV)
100
em
Ex
s≈
ac
tb
re
m
Further basics:
Copper
X0 = 12.86 g cm−2
Ec = 19.63 MeV
RM
21 MeV
=
X0
Ec
0
15:55
RM : Moliere radius
Ec : Critical Energy [Rossi]
X0 : Radiation length
Electromagnetic Showers
Typical values for X0, Ec and RM of materials
used in calorimeter
X0 [cm]
Ec [MeV]
RM [cm]
Pb
0.56
7.2
1.6
Scintillator (Sz)
34.7
80
9.1
Fe
1.76
21
1.8
14
31
9.5
BGO
1.12
10.1
2.3
Sz/Pb
3.1
12.6
5.2
PB glass (SF5)
2.4
11.8
4.3
Ar (liquid)
S
rlo
Ca
te
on
(M
rs
ue
ha
Sc
en
sch
−
eti
e
gn
+ +
ma
e
γ
tro
+
lek
K
e+
se
+
→
d
K
ine
ng
ge
K
→
hlu
+
lun
γ
K
tra
ick
s
+
tw
ms
e
e
En
Br
).
.2:
E0
rch
ern
se
g8
u
s
K
e
2
d
−
=
oz
=
o
Pr
1
se
K
E
(
a
ie
ev
d
i
igt
rd
rg
rt
t
e
ne
Nu
ich
rli
s
e
E
v
eE
ck
i
rü
,d
X0
=
be
X0
ke
en
E±
ch
rec
t
na
rd
we
f
Au
Analytic Shower Model
rS
de
Simple shower model:
[from Heitler]
Only two dominant interactions:
Pair production and Bremsstrahlung ...
γ + Nucleus ➛ Nucleus + e+ + e−
[Photons absorbed via pair production]
ert
isi
ial
e + Nucleus ➛ Nucleus + e + γ
Electromagnetic Shower
[Monte Carlo Simulation]
[Energy loss of electrons via Bremsstrahlung]
Shower development governed by X0 ...
Use
Simplification:
After a distance X0 electrons remain with
only (1/e)th of their primary energy ...
[Ee looses half the energy]
Photon produces e+e−-pair after 9/7X0 ≈ X0 ...
Ee ≈ E0/2
Assume:
E > Ec : no energy loss by ionization/excitation
du
E < Ec : energy loss only via ionization/excitation
Eγ = Ee ≈ E0/2
[Energy shared by e+/e–]
... with initial particle energy E0
rch
us assume that the energy is symmetrically shared between the part
Analytic Shower Model
Sketch of simple
shower development
E0
Simple shower model:
[continued]
/
/
/
/
1
2
3
4
E 0 2 E 0 4 E 0 8 E 0 16
Shower characterized by:
0
Number of particles in shower
Location of shower maximum
Longitudinal shower distribution
Transverse shower distribution
Number of shower particles
after depth t:
N (t) = 2
7
... use:
t1
=2
Number of shower particles
at shower maximum:
t
8
t [X0 ]
Fig. 8.1. Sketch of a simple model for shower parametrisation.
Longitudinal components;
measured in radiation length ...
N (E0 , E1 ) = 2
Energy per particle
after depth t:
➛ t = log2 (E0/E)
6
x
t=
X0
Total number of shower particles
with energy E1:
t
E0
E=
= E0 · 2
N (t)
5
N (E0 , Ec ) = Nmax
Shower maximum at:
tmax / ln(E0/Ec )
log2 (E0/E1 )
E0
=
E1
E0
=2
=
Ec
N (E0 , E1 ) / E0
tmax
Analytic Shower Model
Simple shower model:
[continued]
Longitudinal shower distribution increases only logarithmically with the
primary energy of the incident particle ...
Some numbers: Ec ≈ 10 MeV, E0 = 1 GeV
➛ tmax = ln 100 ≈ 4.5; Nmax = 100
E0 = 100 GeV ➛ tmax = ln 10000 ≈ 9.2; Nmax =10000
Relevant for energy measurement (e.g. via scintillation light):
total integrated track length of all charged particles ...
tmax
T = X0
X1
2µ + t0 · Nmax · X0
µ=0
tmax
As only electrons
contribute ...
E0
= X0 · (2
1) + t0 ·
X0
Ec
E0
log2 E0/Ec
= X0 · (2
1) + t0 ·
X0
Ec
E0
T =
· X0 · F
Ec
[ with
F < 1]
with t0: range of electron with energy Ec
[given in units of X0]
E0
(1 + t0 ) ·
X0 ⇥ E0
Ec
Energy proportional
to track length ...
27. Passage of particles through matter
16
Eq. (27.14) describes scattering from a single material, while the usual problem
involves the multiple scattering of a particle traversing many different layers and
mixtures. Since it is from a fit to a Moli`
ere distribution, it is incorrect to add the
individual θ0 contributions in quadrature; the result is systematically too small. I
is much more accurate to apply Eq. (27.14) once, after finding x and X0 for the
combined scatterer.
Lynch and Dahl have extended this phenomenological approach, fitting
Gaussian distributions to a variable fraction of the Moli`
ere distribution for
arbitrary scatterers [35], and achieve accuracies of 2% or better.
Analytic Shower Model
Transverse shower development ...
Multiple
coulomb scattering
Opening angle
for bremsstrahlung and pair production
2
h i⇡
2
(m/E )
=
1/
x
2
x /2
Small contribution as me/Ec = 0.05
Multiple scattering
splane
deflection angle in 2-dimensional plane ...
h k2 i =
k
X
m=1
2
m
= kh 2 i
r
p
x
13.6 MeV/c
2
h i⇡
p
X0
In 3-dimensions extra factor √2:
p
19.2 MeV/c
2
h i3d ⇡
p
Ψplane
yplane
θplane
Figure 27.9: Quantities used to describe multiple Coulomb scattering. The
particle is incident in the plane of the figure.
Assuming the approximate range of electrons
The[β
nonprojected
(space)
projected (plane) angular distributions
are given
⋅X0 ...
= 1]
to be Xand
0 yields lateral extension: R =〈θ〉
approximately by [33]
⎧ 2
⎫
21MeV
θ
⎪
1
space ⎪
⎪
⎪
⎪
⎪
RM =2 ⇥exp⇤x=X
X0
(27.15
r
⎩− 0 2· X
⎭0dΩ ,
2π
θ
2θ
EC
0
0
x
Molière Radius;
X0 [β = 1]
characterizes
⎧
⎫ lateral shower spread ...
2
θplane ⎪
⎪
1
⎪
⎪
⎪
⎪
√
exp ⎩−
(27.16
2 ⎭ dθplane ,
Insertion – Multiple Scattering
M,v
Reminder:
τ = 2b/v
[Derivation of energy loss ...]
2Zze2
pt =
bv
pt
pt
2Zze2 1
⇡
⇡
=
pk
p
b pv
Atom
h k2 i =
2
m
m=1
✓~k2 =
k
X
m=1
~✓m
!2
=
k
X
m=1
}b
Coulomb
scattering
θk
= kh 2 i
Proof:
θ
Atomic number: Z
As θ ~ Z ➛ main influence from nucleus;
contribution due to electrons negligible ...
k
X
pt
Multiple
Coulomb scattering
✓~m2 + 2
X
i6=j
✓~i ~✓j =
k
X
✓~m2
m=1
Here, the term ∑θiθj vanishes as successive interactions
are statistically independent; to calculate θk one needs to average ...
Insertion – Multiple Scattering
n
:
dx, x :
db, b :
N(b) :
N
:
Probability for a single collision
with impact parameter b:
N (b)
1
P (b) db =
=
· 2 b db dx · n
N
N
2
N⇥
=N·
N
N
Z
2
⇥=N·
bmax
bmin
Z
0
x
Z
1
with
2
P (b) [ (b)] db
Estimation of bmin, bmax:
✓
2Zze
bpv
2
◆2
=
me c
2 2
1
2
·
x
z
·
2
2
p v
"
Z
2
✓
N (b)db
Atomic radius for bmax : bmax = aB ⋅Z–⅓
Nuclear size for bmin : bmin ~ A⅓ ~ Z⅓
db dx
➛ bmax/bmin ~ Z–⅔
Also:
Es =
r
4⇥
m e c2
e2
1
X0 =
, re =
m e c2
4 n Z 2 re2 ln(183/Z 1/3 )
Z 2 z 2 e4 bmax
= 8 nx 2 2 ln
p v
bmin
4⇤
N (b) = 2Z b db dx · n
N=
0
2 b·n
particle density
layer thickness
impact parameter
average number of collisions
total number of collisions
2
e
m e c2
◆2
⇥
n ln 1/3
Z
#
=
Es2
✓
1
pv
◆2
x
z
X0
2
Analytic Shower Model
Transverse shower development ...
R
[continued]
θ
x
Deflection angle:
Lateral extension: R = x⋅tan θ ≈ x⋅ θ, if θ small ...
[Molière-Theory]
1
x
2
· 2 2 ·z ·
⇥=
with Es =
p v
X0
r
x
21.2 MeV
➛ h i=
Ee
X0 [β = 1, c = 1, z = 1]
2
Es2
r
4⇥
(me c2 ) = 21.2 MeV
[Scale Energy]
Lateral shower spread:
Main contribution must come from low energy electrons as〈θ〉~ 1/Ee, i.e. for electrons with E = Ec ...
Assuming the approximate range of electrons to be X0 yields〈θ〉≈ 21 MeV/Ee ➛ lateral extension: R =〈θ〉⋅X0 ...
Molière Radius:
RM
21 MeV
=
X0
Ec
Lateral shower spread
characterized by RM !
On average 90% of the shower energy contained
in cylinder with radius RM around shower axis ...
Electromagnetic Shower Profile
8.1 Electromagnetic calorimeters
Longitudinal profile
600
5000 MeV
Parametrization:
dE
= E0 t e
dt
d E / d t [MeV/X0]
[Longo 1975]
⇥t
α,β : free parameters
tα : at small depth number of
secondaries increases ...
e–βt : at larger depth absorption
dominates ...
400
2000 MeV
200
1000 MeV
500 MeV
Numbers for E = 2 GeV (approximate):
α = 2, β = 0.5, tmax = α/β
0
5
0
More exact
[Longo 1985]
[Γ: Gamma function]
⇥t
➛ tmax =
1
⇥
= ln
✓
◆
E0
+ Ce
Ec 10
[MeV/X0]
(⇥t) 1 e
dE
= E0 · ⇥ ·
dt
( )
100
1
10
t [X0]
15
with:
Ce =
0.5
[γ-induced]
Ce =
1.0
[e-induced]
lead
iron
aluminium
20
Electromagnetic Shower Profile
Transverse profile
z/X0
Abbildung 8.4: Longitudinalverteilung der Energiedeposition in einem elektr
energy
deposit
Schauer für zwei Prim
ärenergien
der Elektronen
[arbitrary unites]
Parametrization:
dE
= e
dr
r/R
M
+ ⇥e
r/
min
α,β : free parameters
RM : Molière radius
λmin : range of low energetic
photons ...
Inner part: coulomb scattering ...
Electrons and positrons move away
from shower axis due to multiple scattering ...
Outer part: low energy photons ...
r/ R
r/RM
r/R
MM
Photons (and electrons) produced in isotropic
processes (Compton scattering,
photo-electric
move away from
Abbildung
8.5: effect)
Transversalverteilung
der Energie in einem elektromagnetisch
shower axis; predominant beyond shower maximum, particularly in high-Z absorber media...
unterschiedlichen Tiefen gemessen
Shower gets wider at larger depth ...
159
Elektromagnetische Schauer
Longitudinale und transversale Schauerentwicklung einer durch 6!GeV/c Elek
ausgelösten elektromagn
etischen Kas
kade in einem Absorber aus Blei.
Electromagnetic
Shower
Profile
2 s: lineare Skala.
– link
rprofil
Bild
– Bild rechts: hablogarithmische Skala
Longitudinal and transversal shower profile
6!GeV/c Elektronen
udinale und transversale Schauerentwicklung
for a einer
6 GeVdurch
electron in lead absorber ...
r aus Blei.
Absorbe
östen elektromagnetischen Kaskade in einem
[left: linear
scale; right: logarithmic scale]
energy deposit
unites]
Skala. – Bild rechts: hablogarithmische Skala
lineare
ks:[arbitrary
energy deposit
[arbitrary unites]
[X
pth
0]
e
d
gitu
n
lo
sh
l
a
n
rd
we
o
i
lateral shower width [X0]
ho
r
we
ls
ina
de
pth
]
[X 0
d
Quelle: C . Grup en, Teilchendetektoren, B.I. W issen
gitu schaftsverlag, 1993
M. Krammer: Detektoren, SS 05
lon
lateral shower width [X0]
Longitudinalshower
Showerprofiles
Shape (longitudinal)
ctromagnetic
Energy deposit per cm [%]
Depth [X0]
Energy deposit of electrons as a function of depth in a
block of copper; integrals normalized to same value
[EGS4* calculation]
Depth of shower maximum increases
logarithmically with energy
tmax / ln(E0/Ec )
Depth [cm]
*EGS = Electron Gamma Shower
Longitudinal Shower Shape
Scaling is NOT perfect
Energy deposit per cm [%]
10 GeV electrons
Lead
Iron
Aluminum
Approximate scaling ....
Energy deposit of electrons as a function
of depth for different materials
[EGS4* calculation]
Depth [X0]
Pb Z = 8
Fe Z = 26
Al Z = 13
Longitudinal Shower Shape
Photons
Z
Photons:
Photo-electric effect ...
/ Z 5, E
3
Compton scattering ...
/ Z, E
Electrons
1
Pair production ...
increases with E, Z
asymptotic at ⇠ 1 GeV
Electrons:
Critical energy ...
1
Ec /
Z
In high Z materials
particle multiplication ...
... down to lower energies
➛ longer showers
[with respect to X0]
Lateral
profile
Transversal Shower Shape
Transverse profile
at different shower depths ....
Up to shower maximum broadening
mainly due to multiple scattering ...
Characterized by RM:
[90% shower energy within RM]
RM =
21 MeV
X0
Ec
Energy deposit [a.u.]
Molière Radii
Beyond shower maximum broadening
mainly due to low energy photons ...
Radial distributions of the energy deposited
by 10 GeV electron showers in Copper
[Results of EGS4 simulations]
Distance from shower axis [RM]
16
Lateral profile
Material dependence:
Scaling almost perfect at low radii ...
Most striking difference seen in
slope of 'tail' or 'halo' ...
Slope considerably steeper for high-Z
material due to smaller mean free path
for low-energy photons ...
Energy deposit [%]
Transversal Shower Shape
10
1
Halo
0.1
Radial energy deposit profiles for
10 GeV electrons showering in Al, Cu and Pb
[Results of EGS4 calculations]
Remark:
Even though calorimeters are intended
to measure GeV, TeV their performance
is determined by low energy particles ...
0.01
0
1
2
3
4
5
Distance from shower axis [RM]
15
Some Useful 'Rules of Thumbs'
Radiation length:
180A g
X0 =
Z 2 cm2
Critical energy:
550 MeV
Ec =
Z
[Attention: Definition of Rossi used]
Shower maximum:
Longitudinal
energy containment:
Transverse
Energy containment:
tmax
E
= ln
Ec
Problem:
Calculate how much Pb, Fe or Cu
is needed to stop a 10 GeV electron.
Pb : Z = 82 , A = 207, ρ = 11.34 g/cm3
Fe : Z = 26 , A = 56, ρ = 7.87 g/cm3
Cu : Z = 29 , A = 63, ρ = 8.92 g/cm3
1.0
1.0
0.5
{
e– induced shower
γ induced shower
L(95%) = tmax + 0.08Z + 9.6 [X0 ]
R(90%) = RM
R(95%) = 2RM
It's not good having only one output signal--> we have a
shower produced and also a radiation lenght
Homogeneous Calorimeters
So we have to divided it into di!erent Layers in a way of
being more precise
★
In a homogeneous calorimeter the whole detector volume is filled by a
high-density material which simultaneously serves as absorber as well
Active in the sense that gives signal--> and also in
as as active medium ...principle
we can follow the development of the shower if i have
di!erent layers--> we know that the maximum is related to the energy
Signal
Material
Scintillation light
BGO, BaF2, CeF3, ...
Inorganic because of the higher Z
Cherenkov light
Lead Glass
Ionization signal
Liquid nobel gases (Ar, Kr, Xe)
★
Advantage: homogenous calorimeters provide optimal energy resolution
★
Disadvantage: very expensive
★
Homogenous calorimeters are exclusively used for electromagnetic
calorimeter, i.e. energy measurement of electrons and photons
Sampling Calorimeters
-It doesn't measure the whole shower but only sample of it
-passive and active layers--> in the active I have the measurement of the
particles produced in the passive layer
-the development of the electromagnetic shower it linked to the radiation
length--> when we know the number of radiation length we need to
produce a certain shower--> I will have the linear dimension of the
calorimeters
-radiation length it proportional to the inverse of Z
Scheme of a
sandwich calorimeter
Principle:
passive absorber
shower (cascade of secondaries)
Alternating layers of absorber and
active material [sandwich calorimeter]
Simple shower model
Absorber materials:
passive material
incoming particle
[high density]
Iron (Fe)
Lead
(Pb)Bremsstrahlung
Consider
only
Uranium (U)
production
and (symmetric) pair
active layers
Thickness -> at least one radiation lenght
[For compensation ...]
Active
Assume
X0materials:
! !pair
Plastic scintillators --> easier
Plastic scintillator
After t XSilicon
0:
detectors
Liquid tionization chamber
!
N(t)
=
2
Gas detectors
E(t)/particle = E /2
the ratio between Active/Passive Material-->
t few percent--> 10% too much
!
0
Electromagnetic shower
A
A
A
A
A
Sampling Calorimeters
A A
A A
A
A
P
P
P
P
P
P
P
P
10%<A/P--> to not have to much fluctuations
★
Advantages:
By separating passive and active layers the different layer materials
can be optimally adapted to the corresponding requirements ...
By freely choosing high-density material for the absorbers one can
built very compact calorimeters ...
Sampling calorimeters are simpler with more passive material and
thus cheaper than homogeneous calorimeters ...
★
Disadvantages:
Only part of the deposited particle energy is actually detected in the
So the fluctuations will be more important --> due to the passing through the passive and the active material
active layers; typically a few percent [for gas detectors even only ~10-5] ...
Due to this sampling-fluctuations typically result in a reduced energy
resolution for sampling calorimeters ...
A
A
Sampling Calorimeters
Possible setups
Scintillators as active layer;
signal readout via photo multipliers
Absorber
Scintillator
Light guide
Photo detector
Scintillators as active
layer; wave length shifter
to convert light
Scintillator
(blue light)
Wavelength shifter
Charge amplifier
Absorber as
electrodes
HV
Ionization chambers
between absorber
plates
Argon
Active medium: LAr; absorber
embedded in liquid serve as electrods
Electrodes
Analogue
signal
Sampling Calorimeters
Example:
ATLAS Liquid Argon Calorimeter
Argon not so common--> in the simulation better use something
else(?)
Calorimiters--> not only to measure energy and descriminate particles
but also to recostruct the shower
Sampling Calorimeters
Example:
H1 SpaCal
Sampling calorimiter--> Passive--> lead/Active-->scintillators
Lead-Fibre Matrix
[Front view]
[Spaghetti Calorimeter]
4 SpaCal Supermodules
Lead matrix ...
[Technical drawing]
Example: CALICE Electromagnetic
Calorimeter
:;<=:9.642)1-
Sampling Calorimeters
‘Alveolar Structure’
Tungsten
frame
?4
Sensors
+ r/o electonics
>45?34232.53.
Detector
slabs
max.: 1.6 m
Tungsten
layer
/84.:;
Homogeneous vs. Sampling Calorimeters
28. Detectors at accelerators 57
Table 28.8:
Resolution of typical electromagnetic calorimeters. E is in GeV.
Energy resolution
Date
NaI(Tl) (Crystal Ball)
20X0
1983
Bi4 Ge3 O12 (BGO) (L3)
22X0
1993
[E is in GeV]
CsI (KTeV)
27X0
CsI(Tl) (BaBar)
2.7%/E1/4
√
2%/ E ⊕ 0.7%
√
2%/ E ⊕ 0.45%
Resolution of typical
electromagnetic calorimeter
16–18X0 2.3%/E 1/4 ⊕ 1.4%
1999
PbWO4 (PWO) (CMS)
25X0
1997
Lead glass (OPAL)
20.5X0
Liquid Kr (NA48)
27X0
Scintillator/depleted U
(ZEUS)
Scintillator/Pb (CDF)
20–30X0
CsI(Tl) (BELLE)
16X0
18X0
15X0
Liquid Ar/Pb (NA31)
27X0
Liquid Ar/Pb (SLD)
21X0
Liquid Ar/Pb (H1)
20–30X0
Liquid Ar/depl. U (DØ)
20.5X0
Liquid Ar/Pb accordion
(ATLAS)
25X0
√
13.5%/ E
√
5.7%/ E ⊕ 0.6%
√
7.5%/ E ⊕ 0.5% ⊕ 0.1/E
√
8%/ E
√
12%/ E ⊕ 1%
√
16%/ E ⊕ 0.3% ⊕ 0.3/E
√
10%/ E ⊕ 0.4% ⊕ 0.3/E
1998
1990
1998
1988
1988
1995
1988
1993
1998
1993
1996
Sampling
Scintillator fiber/Pb
spaghetti (KLOE)
1.7% for Eγ > 3.5 GeV
√
3%/ E ⊕ 0.5% ⊕ 0.2/E
√
5%/ E
√
3.2%/ E⊕ 0.42% ⊕ 0.09/E
√
18%/ E
1996
Homogeneous
Technology (Experiment) Depth
10GeV e-
Energy Resolution
t(X0)
Calorimeter energy resolution determined by fluctuations ...
Homogeneous calorimeters:
Shower fluctuations
Quantum fluctuations
Photo-electron statistics
I have to measure the shower of a particle I want to contain the whole shower--> I have to add
Shower leakage -->If
to much material just to contain few percentage of the shower--> so when I lose some parts of the
shower
Instrumental effects
(noise, light attenuation, non-uniformity)
In addition for
Sampling calorimeters:
Sampling fluctuations
Landau fluctuations
Track length fluctuations
a
=p
E
E
E
b
E
c
p
Quantum fluctuations
Electronic noise
Shower leakage*
⇠ 1/ E
⇠ 1/E
= const
⇡
Sampling fluctuations
Landau fluctuations
Track length fluctuations
⇠ 1/ E
p
1
⇠ /pE
⇠ 1/ E
See the next slides
*
p
Different for longitudinal and lateral leakage ...
Complicated; small energy dependence ...
Energy Resolution
Shower fluctuations:
[intrinsic resolution]
Ideal (homogeneous) calorimeter without leakage: energy resolution limited
only by statistical fluctuations of the number N of shower particles ...
i.e.:
p
1
N
/
⇡
= p
E
N
N
N
r
W
E
/
E
E
N
E
with
E
N=
W
Resolution improves due to correlations
between fluctuations (Fano factor; see above) ...
E
E
/
r
FW
E
[F: Fano factor]
E : energy of primary particle
W : mean energy required to
produce 'signal quantum'
Examples:
Silicon detectors :
Gas detectors
:
Plastic scintillator :
W ≈ 3.6 eV
W ≈ 30 eV
W ≈ 100 eV
Energy Resolution
Photo-electron statistics:
For detectors for which the deposited energy is measured via light detection
inefficiencies converting photons into a detectable electrical signal (e.g. photo
electrons) contribute to the measurement uncertainty ...
i.e.:
E
E
/
Npe
Npe
1
⇡p
Npe
Npe : number of photo electrons
This contribution is present for calorimeters based on detecting scintillation
or Cherenkov light; important in this context are quantum efficiency and gain
of the used photo detectors (e.g. Photomultiplier, Avalanche Photodiodes ...)
Also important: losses in light guides and wavelength shifters ....
Einfluß longitudinaler und transversaler Leckverluste auf die Energieauflösung. (15!GeV e–, Marmor-Kalo
rimeter der CHARM-Kollaboration)
Marmor Calorimeter
Fluctuations due to finite size
of calorimeter; shower not
fully
contained
...
unter
Berücksichtigung
ösung
r Leakage-Effekte:
Lateral leakage: limited influence
Longitudinal leakage: strong influence
expression
$" (ETypical
'
) including leakage effects:
when
#&
* [1 + 2f E ]
)
% E (f = 0 ⇣ ⌘
h
⇥
E
E
E
E
f =0
· 1 + 2f E
[CHARM Collaboration]
Energy resolution σ/E [%]
rimeter haben klarerweise nur
es Volumen.
Dadurch kann es
Energy Resolution
n, daß die entstandene
skade nicht vollständig im
Shower leakage:
nthalten ist.
Electrons 15 GeV
i
[ f : average fraction of shower leakage]
eil der longitudinal verlorenen Energie
Remark: other parameterizations exist ...
Leakage [%]
Quelle: C . Grup en, Teilchendetektoren,
Energy Resolution
Sampling fluctuations:
Additional contribution to energy resolution in sampling calorimeters due
to fluctuations of the number of (low-energy) electrons crossing active layer ...
Increases linearly with energy of incident particle and fineness of the
sampling ...
Nch
Nch
Nmax
tabs
E
/
Ec tabs
Reasoning: Energy deposition dominantly due to low energy electrons;
range of these electrons smaller than absorber thickness tabs;
only few electrons reach active layer ...
Fraction f ~ 1/tabs reaches the active medium ...
Resulting
energy resolution:
E
E
/
Nch
Nch
/
: charged particles reaching active layer
: total number of particles = E/Ec
: absorber thickness in X0
r
Semi-empirical:
Ec tabs
E
Choose: Ec small (large Z)
tabs small (fine sampling)
E
E
s
= 3.2%
Ec [MeV] · tabs
F · E [GeV]
where F takes detector threshold
effects into account ...
Energy Resolution
Measure energy resolution
of a sampling calorimeter for
different absorber thicknesses
..
Kanale
GeV
Sampling
contribution:
E
E
s
= 3.2%
Ec [MeV] · tabs
F · E [GeV]
Sampling
SamplingFluktuationen
Fluctuations
Photo-electron
Statistics
+ Leakage
Photoelektron−Statistik
+ Leakage
D [mm]
Ab
s erste Folge dieses Sachverhaltes ergibt sich, daß sich die von den
ilchen durchquerten Distanzen von den Absorberdicken bzw. den Dicken
r Detektorschichten unterscheiden. Man muß daher in den Formeln für die
Energy
amplingund dieResolution
Landau-Fluktuationen effektive Schichtdicken einsetzen:
tabs!!!tabs/cos!.
Track length fluctuations:
passive absorber
arüber hinaus variiert der tatsächDue
to multiple
scattering particles
he Winkel
zur
Kalorimeterachse
traverse absorber
at different angles ...
n Schauerteilchen
zu SchauerDifferent
effective absorber
lchen.➛D.h.
die zurückgelegten
incident particles
thickness: bzw. Absorberege im Detektor
tabs !
tabs / cos zu
aterial sind von
Teilchen
[Enters sampling (and Landau) fluctuations]
ilchen verschieden. Dies ist die
active layers; detectors
sache für die eigentlichen
Illustration der verschiedenen WeglänLandau fluctuations:
purlängenfluktuationen.
gen unterschiedlicher Schauerteilchen.
Asymmetric distribution of energy deposits in thin active layers yields
correction
:
er: Detektoren,
SS 05[Landau instead of Gaussian distribution]Kalorimeter
⇥E
=
E
1
3
·
Nch ln(k · )
[semi-empirical]
with:
k : constant; k = 1.3⋅104 if δ measured in MeV
δ : average energy loss in active layer ('thickness')
18
Sampling-, Landau- und Spurlängenfluktuationen zur relativen
Energy Resolution
m. Kalorimeters
aus 1!mm dicken Bleiplatten und 5!mm
amtdicke: 12.5!Strahlungslängen):
Calculated contributions
from
Track Length fluctuations
Sampling fluctuations
Landau fluctuations
Calorimeter:
1 mm lead absorber
5 mm scintillator
Total thickness: 12.5 X0
Hadronic Showers
Die Kernverdampfung
folgt
in einem
In Absorbern aus schweren Elementen,
z.B. 238U, kann es
nach
einer Kalorimeter typis
prozess aufoder
einenach
Spallation.
Spallation mit einhergehender Kernanregung
dem Einfang eines
langsamen Neutrons durch einen Targetkern zu einer Kernspaltung kommen.
Nuclear
Dabei zerfällt der Kern unter Energiefreisetzung in 2evaporation
(sehr selten auch 3)
annähernd gleich große Kernbruchstücke. Zusätzlich werden dabei typischerweise außerdem Photonen und Neutronen emittiert. Haben die Kernbruchstücke nach der Spaltung noch hohe Anregungsenergien, so können sie auch
andere Hadronen emittieren.
C
Hadronic Showers
Hadronic interaction:
Elastic:
p + Nucleus ! p + Nucleus
Inelastic: Bild rechts: Schematische
Illustration
p + Nucleus
! der Kernspaltung
mit
Emission
+ anschließender
+
+ 0 + . . . + Nucleus⇤
von Hadronen und Photonen.
⇤
Nucleus ! Nucleus A + n, p, , ...
Nucleus⇤ ! Nucleus B + 5p, n, , ...
! Nuclear fission
B
Bild oben: Schematische Illustration der Kernverdampfung. H
verlierenFission
typischerweise innerhalb von !"10-18"s einen Großt
durch die Emission von Kernbausteinen.
M. Krammer: Detektoren, SS 05
Heavy Nucleus (e.g. U)
M. Krammer: Detektoren, SS 05
Kalorimeter
Kalorimeter
44
Incoming
hadron
Ionization loss
A
Ionization loss
Intranuclear cascade
(Spallation 10-22 s)
Inter- and
intranuclear cascade
Intranuclear cascade
(Spallation 10-22 s)
Internuclear cascade
Hadron
shower
KL
Hadronic Showers
μ
KS
ν
π0
Shower development:
N
1. p + Nucleus ➛ Pions + N* + ...
π0
2. Secondary particles ...
ν
undergo further inelastic collisions until they
fall below pion production threshold
Mean number of
secondaries: ~ ln E
3. Sequential decays ...
π0 ➛ γγ: yields electromagnetic shower
Fission fragments ➛ β-decay, γ-decay
Neutron capture ➛ fission
Spallation ...
n
μ
Typical transverse
momentum: pt ~ 350 MeV/c
Cascade energy distribution:
Substantial
electromagnetic fraction
fem ~ ln E
[variations significant]
[Example: 5 GeV proton in lead-scintillator calorimeter]
Ionization energy of charged particles (p,π,μ)
Electromagnetic shower (π0,η0,e)
Neutrons
Photons from nuclear de-excitation
Non-detectable energy (nuclear binding, neutrinos)
1980 MeV [40%]
760 MeV [15%]
520 MeV [10%]
310 MeV [ 6%]
1430 MeV [29%]
5000 MeV [29%]
Hadronic Showers
Comparison
20
hadronic vs. electromagnetic shower ...
250 GeV
proton
altitude above sea level [km]
[Simulated air showers]
250 GeV
photon
15
10
5
0
lateral shower width [km]
0
lateral shower width [km]
+5
Hadronic Showers
12
40. Plots of cross sections and related quantities
Hadronic interaction:
Cross Section:
tot
=
el
+
!"#$$%$&'()#*%+,-.
at high energies
also diffractive contribution
inel
For substantial energies
σinel dominates:
⇡ 10 mb
2/3
[geometrical cross section]
inel / A
tot
=
tot (pA)
tot (pp)
2
total
⇓
pp
elastic
10
el
∴
10
Plab GeV/c
10
2/3
·A
-1
1
10
10
2
10
3
10
4
10
5
10
6
10
7
10
8
√s GeV
1.9
[σtot slightly grows with √s]
2
10
10
2
10
3
10
4
Total proton-proton cross section
[similar for p+n in 1-100 GeV range]
int
=
which yields:
1
⇤tot · n
=
A
1
⇤pp A2/3 · NA ⇥
A /3
1/3
35 g/cm2 · A
N (x) = N0 exp( x/
!"#$$%$&'()#*%+,-.
Hadronic interaction length:
10
2
⇓
[for √s ≈ 1 – 100
GeV]
total
−
pp
Interaction length characterizes both,
elastic
longitudinal
and transverse profile of
hadronic showers ...
P
10
int )
a
Remark: In principle one should distinguish between collision
length λW ~ 1/σtot and interaction length λint ~ 1/σinel where
the latter considers inelastic processes only (absorption) ...
lab
10
-1
1
10
10
2
10
3
10
4
10
5
10
6
10
7
GeV/c
10
8
Figure 40.11: Total and elastic cross sections for pp and pp collisions as a function of laboratory beam momentum and total center-of-mass
energy. Corresponding computer-readable data files may be found at http://pdg.lbl.gov/current/xsect/. (Courtesy of the COMPAS group,
IHEP, Protvino, August 2005)
Hadronic Showers
Some numerical values for materials
typical used in hadron calorimeters
Hadronic vs. electromagnetic
interaction length:
A
X0 ⇠ 2
Z
int
int
1/3
⇠A
➛
int
X0
λint [cm]
X0 [cm]
Szint.
79.4
42.2
LAr
83.7
14.0
Fe
16.8
1.76
Pb
17.1
0.56
U
10.5
0.32
C
38.1
18.8
4/3
⇠A
LambdaInt is much larger than
X0--> radiation length
X0 a
[λint/X0 > 30 possible; see below]
Typical
Longitudinal size: 6 ... 9 λint
[EM: 15-20 X0]
[95% containment]
Typical
Transverse size: one λint
[95% containment]
[EM: 2 RM; compact]
Hadronic calorimeter need more depth
than electromagnetic calorimeter ...
Hadronic Showers
Hadronic shower development:
But:
[estimate similar to e.m. case]
Only rough estimate as ...
Depth (in units of λint):
t=
energy sharing between shower particles
fluctuates strongly ...
x
part of the energy is not detectable (neutrinos,
binding energy); partial compensation possible
(n-capture & fission)
int
Energy in depth t:
E
E(t) =
& E(tmax ) = Ethr
t
hni
[with Ethr ≈ 290 MeV]
E
Ethr =
hnitmax
Shower maximum:
tmax
hni
tmax
E
=
Ethr
ln (E/Ethr )
=
lnhni
Number of particles
lower by factor Ethr/Ec
compared to e.m. shower ...
Intrinsic resolution:
worse by factor √Ethr/Ec
spatial distribution varies strongly; different
range of e.g. π± and π0 ...
electromagnetic fraction, i.e. fraction of energy
deposited by π0 ➛ γγ increases with energy ...
fem ⇡ f
0
⇠ ln E/(1 GeV)
Explanation: charged hadron contribute to electromagnetic
fraction via π–p ➛ π0n; the opposite happens only rarely as
π0 travel only 0.2 μm before its decay ('one-way street') ...
At energies below 1 GeV hadrons loose their
energy via ionization only ...
Thus: need Monte Carlo (GEISHA, CALOR, ...)
to describe shower development correctly ...
Number of nuclei [arbitrary units]
Hadronic Showers
Longitudinal shower
development:
Strong peak near λint ...
followed by exponential decrease ....
Shower depth:
tmax ⇡ 0.2 ln(E/GeV) + 0.7
15
L95 = tmax + 2.5
att
with
att
⇡ (E/GeV )0.3
Example: 300 GeV pion ...
tmax = 1.85; L95 = 1.85 + 5.5 ≈ 7.4
10
[95% within 8λint; 99% within 11 λint]
5
95% on
average
because it costs too
much in terms of length
Longitudinal shower profile for 300 GeV π– interactions in a block
of uranium measured from the induced 99Mo radioactivity ...
0
1
2
3
4
5
6
7
8
9
10
Depth [λint]
Particles Identification
Charged particle identification
! Identification of charged particles based on
mass determination requires the simultaneous
measurement of at least two quantities
! First observable is typically the particle
momentum determined via tracking in
magnetic field
! Need second observable:
o Velocity:
Time-of flight
Cherenkov angle
Transition radiation
o Energy loss:
Bethe-Bloch
with p, γ,"β,"calculate
the particle mass
o Total energy: Calorimeter
Genova, 28/2/2017
Lecture 2: Particle Identification
14
Used to quantify
usability
of a technique
Detector length vs momentum
Express as e.g. a 3\sigma
separation of K vs \pi
n_\sigma=(R_A-R_B)/<\sigma_A,B>
R is detector response for certain particle type
<\sigma_A,B> is average of standard deviation of the two measured
responses
Compare differebt PID techniques--> dE/dx, TOF, Cherenkov
Muon Identification
High energy proton for example
Possible to have haidronic shower also in the electromagnetic calorimeter--> it depends on the
attenuation length that it have
By analyzing the way they interact - mainly lepton and photons
Ts & Magnetic:
- charge and momentum
-\gamma-->e+e- (if this happens)
-kink of charged kaon decay
Calorimeters
- Electrons - TS and EM (energy has to match momentum)
-Photons-EM (no track)
-Neutrals-EM and hadron
-Charged hadrons - TS, EM and Hadron
-Only \mu and \ni
Muon System
-Track in TS, EM, hadron and muon system
Introduction
Special signatures for neutrals:
Photons
:
Total energy deposited in electromagnetic shower; use
energy measurement, shower shape and information on
neutrality (e.g. no track) ...
Neutrons :
Energy in calorimeter or scintillator (Li, B, 3He) and
information on neutrality (e.g. no track) ...
K0, Λ, ...
Reconstruction of invariant masses ...
:
Neutrinos :
Identify products of charged and neutral current
interactions ...
Muons:
Minimum ionizing particles; penetrates thick absorbers; measure signal
behind complete detector ...
(2
2(7&70&>($<-:0($4/:'5(2?$:-7*$4:-*2&'(0(2$@3(802*37A
80$:--$70*<,7&.3:-7$&30*$%BC$$@0&'(,0*,1&.&0:-$4*3>(20(2A$6&0/$
$+2*'
$D5(:'D$*2$D&30(2:40&*3D
Time-of-Flight
Method
Key point of the techniques is the time resolution
Scintillator I
Basic idea:
If the rise time is fast--> good resolution
Measure signal time difference between
two detectors with good time resolution
[start and stop counter; also: beam-timing & stop counter]
particle
Scintillator II
Typical detectors:
Scintillation counter
Resistive Plate Chamber (RPC)
PMT
Coincidence setup or TDC measurement
with common start/stop from interaction time
PMT
Analog signal
Output only if the signal is higher than a threshold --> background
Start
Digital signal
Quadratic Wave
multichannel
analyzer
Like a Gaussian
TDC
Stop
Time to digital converter
Discriminators
Introduzione ai rivelatori di particelle
Identificazione con tempo di volo (TOF)
• TOF
L=base di volo
t=TOF
t+ t
t
L
L
pc 2
= βc =
= c2
Δt
E
Δt 1
=
L c
p
p 2c 2 + m 2c 4
=c
p
p 2 + m 2c 2
p 2 + m 2c 2 1
m 2c 2
=
1+ 2
p2
c
p
m 2c 2
m 2c 2
m 2c 2
per
<< 1 vale 1 + 2 ≈ 1 +
p2
p
2 p2
– se ho due particelle con lo stesso momento e
masse diverse m1 e m2 ottengo:
L ⎛ m12c 2
m2 2c 2 ⎞
Δt1 − Δt 2 = ⎜1 +
− 1−
⎟
c⎝
2 p2
2 p2 ⎠
Δt1 − Δt 2 =
(
Lc
2
2
2 m1 − m 2
2p
)
– Il tempo di volo dipende dalla differenza dei
quadrati delle masse
AA 2008/2009
Cesare Voci - Roberto Carlin
3
Time-of-Flight Method
σt
σt
σt
Difference in
time-of-flight in σt ...
[L = 2 m]
4σt
Determine m by measuring t and p (and L)
m=(p/c)\sqrt((c^2t^2/L^2)-1)
\betha = v/c=L/tc
Particle separation for 3 time resolutions
For particles A and B with different mass, and p>>mc:
n_\sigma_TF=(|t_A-t_B|)/\sigma_TOF=(Lc/2p^2\sigma_TOF)|m^2_A-m^2_B|
Mis-ID for high momenta --> t_TOF ≈ \sima_TOF
IMPORTANT
We consider the TOF between two detector--> differences between two masses
Time-of-Flight Method
No
Distinguishing particles with ToF:
Particle 1
Particle 2
[particles have same momentum p]
t=L
t=
✓
1
v1
L
(E1
2
pc
1
v2
◆
L
=
c
✓
1
1
2
✓q
L
p2 c2 + m21 c4
E2 ) = 2
pc

L
m21 c4
t ⇡ 2 (pc +
)
pc
2pc
m22 c4
(pc +
)
2pc
[mK ≈ 500 MeV, mπ ≈ 140 MeV]
Assume:
p = 1 GeV , L = 2 m ...
distance between ToF counters
◆
q
p2 c2 + m22 c4
For L = 2 m:
Requiring Δt ≳ 4σt K/π separation possible
up to p = 1 GeV if σt ≈ 200 ps ...
m22
Cherenkov counter, RPC : σt ≈ 40 ps ...
Scintillator counter
: σt ≈ 80 ps ...
Example:
Pion/Kaon separation ...
Distance L :
velocity v1, β1; mass m1, energy E1
velocity v2, β2; mass m2, energy E2
m i c2 :
Relativistic particles, E ' pc
Lc
t = 2 m21
2p
1
◆
:
:
➛
t⇥
2 m·c
2
500
2 (1000)2 MeV2 /c2
⇡ 800 ps
1402 MeV2 /c4
Problem:
We want to know the distance where I have to put a counter that has a
time resolution of σ=200ps to distinguish with 90% of confidence level
that means around 3σ, pion and kaon with the same momentum of 1GeV.
Δt≈3σ≈750ps
[[Δt2p^2]c/(m_1^2-m_2^2)]x2=L= 1.95 x 2=3.9m
Time-of-Flight Method
No
Mass resolution ...
p = ⇥m
✓
1
m2 = p 2
2
➛
(m ) = 2p p
2
1
✓
◆
2
⇥
L2
= p2
✓
2
⇥
L2
➛
(m ) = 2 m
4
p
p
◆2
Usually:
L
p
⇥
⌧
⌧
L
p
⇥
➛
2
)
1
[c = 1]
* p2 2
2
2
2
=
m
+
p
=
E
L2
L 2 2
2 3p ⇥
L
use *
a
p
2 ⇥
= 2m
+ 2E
p
⇥
2
◆
p2
1 + 2⇥ ⇥ 2
L
L
2E
L
2
✓
1
◆
m2/p2
"
= L/⇥
= (1
Use:
2
+E
4
⇣
⇥
⌘2
+E
(m2 ) = 2E 2
⇣
4
⌧
⇥
L
L
⌘2
#1/2
Uncertainty in time
measurement dominates ...
If I measure dE/dx with a gaseous detector->I have to know thw momwntum--> I can draw the different curves as in the next slide
Specific Energy Loss
Average energy loss in
a 1 cm layer of argon-methane
Use relativistic rise of dE/dx
for particle identification ...
μ/π separation impossible, but
π/Κ/p generally be achievable
Key problem: Landau fluctuations
normalized dE/dx
Probability
Need to make many dE/dx measurements
and truncate large energy-loss values ...
[determination of 'truncated mean']
0.3
K
π
0.2
e
1.6
π
µ
1.4
p = 50 GeV
K
1.2
Energy loss distribution;
50 GeV pions and kaons ...
p
0.1
[1 cm layer Ar/Methane]
0
1.0
2
3
5
4
Energy loss [keV]
0.1
1.0
10
100
momentum p [GeV]
I have to build a detector with small resolution and small dE/dx--> separate particles with a good confidence level
TPC Signal [a.u.]
Specific Energy Loss
180
Measured
energy loss
140
[ALICE TPC, 2009]
100
60
Bethe-Bloch
Remember:
dE/dx depends on β!
20
0.1 0.2
1
2
Momentum [GeV]
dE/dx discrimination power
The PEP4/9-TPC (SLAC) energy deposit measurements
(185 samples, 8.5 atm Ar-CH4 80:20).
Solution:
Perform multiple measurements of
energy loss in low density absorbers
[gaseous detectors, trackers]
Compute average of energy loss in
different layers to increase statistical
precision
Apply truncation method: knock out
large energy losses to suppress effects
of the Landau tail
[keep values in the lowest 40-60% of measured values]
Genova, 2/4/15
Lecture 2: Particle Identification
21
Gaseous detectors are the best than liquid and solid one for particles identification
Multiple dE/dx measurements
Multiple measurements of energy loss are used to improve the resolution
on this observables
For a particle crossing a material of thickness L where N measurements of
Experimental resolution of energy-loss measurements (FWHM/mean) for
dE/dx are performed
N gas counters of thickness T=L/N.The gas is argon at STP
if L/N is kept fixed:
σr ∝
1
N
σr ∝
1
L
if L is fixed, there is an optimal number
measurements
Genova, 2/4/15
Lecture 2: Particle Identification
N of
22
Multiple dE/dx measurements
The natural choice detectors to perform multiple ionization measurements
are gas counters used for charged particle tracking, where the multiple
measurements are used to determine the particle trajectory
In first approximation, the relative
resolution improves for increasing gas
pressure:
1
p = gas Pressure
σr ∝
p
Experimental resolution of energy-loss measurements (FWHM/mean) for
N gas counters of thickness T=L/N.The gas is argon at STP
The effect is partially suppressed by
the saturation of dE/dx at large speed
due to the density effect which
compensated the relativistic rise
Genova, 2/4/15
50% rise
0.05 atm
1.00 atm
3.13 atm
The best one is 0.05 atm --> that means that we can have better particles identification-->steeper log rise--> more
there is a difference between particles
Lecture 2: Particle Identification
23
The contribution
of Cherenkov
radiation
to the
Cherenkov
radiation
amounts to
less than
1% en
o
compared
to that from
ionisation
minimum-ionising
particles.
For and
lightexcitation,
gases (He,Eq
H
minimum-ionising
For gases with Z ≥ 7 t
to about 5% [21,particles.
22].
Cherenkov radiation amounts to less than 1% of the
minimum-ionising particles. For light gases (He, H) thi
to about 5% [21, 22].
Cherenkov Radiation
See: Lecture 3
A
Reminder:
B
Polarization effect ...
Cherenkov photons emitted if v > c/n ...
Cherenkov angle:
parti
1
cos ⇥c =
n
c
vv<<n
c/n
wavefront
C
c/n⋅t
θ
fast particle
A
Simple
Geometric derivation:
B
βc⋅t
light
v > nc
c
c
<n
Fig. 5.39. vIllustration
of the Cherenkov
vv >> nc/n effect [1
determination of the Cherenkov angle.
A : vIllustration
< c/n
Fig. 5.39.
of the Cherenkov effect [140,
determination
the Cherenkov
angle.
Inducedofdipoles
symmetrically
arranged
around particle path; no net dipole moment;
no Cherenkov radiation
AB = βc⋅t
B : v > c/n
AC = c/n⋅t
Symmetry is broken as particle faster the
electromagnetic waves; non-vanishing
dipole moment; radiation of Cherenkov photons
cos θ = AC / AB = c/n⋅t/(βc⋅t)
= 1/nβ
Lezione 19
Contatori Čerenkov a soglia
Un grosso Čerenkov
Sopra soglia per
pioni e K di 6,10 e
14 GeV/c
Riempito di propano
a pressione
Rivelatori di Particelle
12
Lezione 19
Contatori Čerenkov a soglia
Il contatore
più grande
riempito di
CO2 a
pressione
atmosferica,s
opra soglia
solo per pioni
Rivelatori di Particelle
13
Threshold Cerenkov counters
does not use Cherenkov angle but threshold effect
Genova, 15/4/15
Lecture 4: Particle Identification - Cerenkov Detectors
13
Contatori a soglia
Nella forma piu’ semplice => decisione si/no a seconda che
la parIcella sia sopra o soCo la soglia in velocita’ βt=1/n.
Il numero di fotoni emessi dipende da θC , l’emissione e’ maggiore
per parIcelle molto sopra soglia. A parita’ di impulso raggiungono i
soglia prima gli e+‐, poi i π,K,p
C.Voena
Pagina 13
If the emission of the theta cherenkov is in a given range--> the radiation pass through the photomultipliers
Cherenkov Radiation – Application
Differential Cherenkov detectors:
Selection of narrow velocity interval
for actual measurement ...
Radiator
Al-Mirror
θ
particle track
Threshold velocity:
[cos θ = 1]
min
=
1
n
Cherenkov angle limited
by total reflection
Maximum velocity:
[θ = θmax = θt]
sin
t
= 1/nq
cos ⇥max =
max
1
= p
n2
1
sin2 ⇥t = 1/n
max
1
PMT
Example:
Diamond, n = 2.42 ➛ βmin = 0.413, βmax = 0.454,
i.e. velocity window of Δβ = 0.04 ...
Suitable optic allows Δβ/β ≈
air light
guide
Very good precision
10-7
Working principle of a
differential Cherenkov counter
Lezione 19
Contatori Čerenkov differenziali
Attenzione al di sopra di 20-30 GeV, se non voglio avere dei Čerenkov troppo
lunghi, conviene misurare l’angolo di Čerenkov.
è
Contatori differenziali o DISC (una via di mezzo fra contatori a soglia e per la
misura dell’angolo )
Principio di funzionamento
specchio
q
Guida di luce in aria
radiatore
Accetta solo particelle in una finestra di velocità (b). Tutte le
particelle che hanno una velocità > bmin=1/n sono sopra soglia. Al
crescere di b aumenta l’angolo di Čerenkov fino a raggiungere
l’angolo di riflessione totale èla luce non entra nella guida di luce.
L’angolo di riflessione totale può essere calcolato dalla legge di
Snell (sin(qt)=1/n) e siccome cosq=1/bn àbmax=(n2-1)-1/2. è solo
particelle in una finestra di velocità possono essere rivelate (piccola
accettanza).
Fotomoltiplicatore
Se il DISC è ottimizzato otticamente (e.g. con dei prismi per le
aberrazioni cromatiche) si possono ottenere Db/b~10-7
Rivelatori di Particelle
16
Differential Cherenkov Detectors
I can select a given theta
good resolution only if I put diaphragm in the focal plane
At the end we see a circumference on the plane
Plane here
Focal Plane
With a Gas radiator
If I have a plane near the focal plane
We want to avoid diffraction--> so diafram should be small,
but not too small
Cherenkov selecting a range of theta
15
Differential Cherenkov Detectors
if I know the refracting index both outside and inside, the momentum of the beam --> I know the theta
Refracting index--> from n1 to n2
refracting index of quartz ≈ 1.5
With Solid (quartz) radiator
Ø Discovery of anti-proton
in 1955 by Chamberlain,
Segre et. al. at Berkeley.
Ø Nobel Prize in 1959
14
Threshold!Cherenkov!Detector!
!!
To!get!a!wider!momentum!range!!for!
particle!identification,!use!more!than!one!
radiator.!!
!
Assume!
!A!radiator:!!n=1.0024!
!B!radiator:!!n=1.0003!
!
!Positive!particle!identification:!
A gas Cherenkov counter
as used to tag particles
in the secondary beams
Apr 1963 Photo number:
CERN-IT-6304088
E. Fiandrini Rivelatori di Particelle 1516
19
I can put some optics that do the opposite of the dispertion-->And this is
called the corretted differential Cherenkov
Lezione 19
Contatori differenziali
Contatori differenziali e DISC
■ solo particelle in una finestra di b. è accettanza limitata
■ Funzionano solo se le particelle incidenti sono // all’asse ottico ènon utilizzabili ai Collider
■ Prismi correggono le aberrazioni cromatiche ( n = n (l ) )
Why we insists so much on having a good resolution on betha and so on theta?
Because the smaller is the delta beta the smaller is the delta theta--> so if I have a good resolution for that
I can also have a good discrimination between the masses
Rivelatori di Particelle
17
The basic idea to identify particles is this Kind of arrangement. The production of particles is not in a point
but in a region--> where the two beams are colliding but we can simplify that they are produced in a point-->
here we have a spherical detector
Lezione 19
Contatori RICH
v
Apparati focalizzanti
Emission of Cherenkov light
Il sistema funziona bene solo per
piccoli parametri d’impatto xi<<RM e
piccoli angoli di Čerenkov. Inoltre
apparati piatti sono più facili da
costruire.
Photodetector
θ_cherenkov=θ_D2=θ_c
focal plane of that mirror
L’ errore sull’angolo di emissione del
fotone è ridotto (di molto) è
possibile costruire radiatori lunghi
(ed avere quindi più fotoni)
Lunghezza focale di uno specchio sferico f=RM/2=RD.
Raggio cerchio Čerenkov r=fqc=(RM/2)qc=RDqc è b
We have to immagine that this is a cone
We have to remeber what is a focal plane-->Any plane
to the axis of a lens or mirror. 23
Rivelatori di perpendicular
Particelle
All the photons in principle are focused here--> in
principle plane with no thickness
Ring Imaging Cerenkov detectors
Seguinot and Ypsilantis, NIM 142 (1977) 377
Genova, 15/4/15
Lecture 4: Particle Identification - Cerenkov Detectors
21
Introduzione ai rivelatori di particelle
Imaging Cherenkov
• RICH (Ring Imaging Cherenkov)
• si ricostruisce la posizione dei singoli fotoni
emessi
• dal raggio del cerchio e dalla distanza dal
radiatore si risale all’angolo e quindi alla
R1
1
1
2
2
R2
l
radiatore Cherenkov sottile
cosθC =
l
l +R
2
1
β=
=
n cosθC
2
=
1
nβ
rivelatore di fotoni sensibile
alla posizione
l2 + R2
ln
• proximity focusing: radiatore deve essere
relativamente sottile per produrre un cerchio
focalizzato The radiator has to be very very small
– piccolo numero di fotoni (tenendo conto anche
dell’efficienza quantica del rivelatore
– possibile confusione tra i cerchi se la densità di
particelle è alta
Use in situations where I have a relatively high rate of particles
AA 2008/2009
Cesare Voci - Roberto Carlin
13
Cherenkov Radiation – Application
See: Lecture 3
Measurement of Cherenkov angle:
Use medium with known refractive index n ➛ β
Principle of:
RICH (Ring Imaging Cherenkov Counter)
DIRC (Detection of Internally Reflected Cherenkov Light)
DISC (special DIRC; e.g. Panda)
Differential counter--> with the correction for the dispersion of light
LHCb RICH Event
[December 2009]
LHCb RICH
RICH Detectors
Critical aspects:
! Large area photodectors
with high granularity (good
spatial resolution)
! Complex optics with small
uncertainties
! Uniform radiators with
small chromatic dispersion
Genova, 15/4/15
! Proximity focusing RICH
! The LHCb RICH detector
Lecture 4: Particle Identification - Cerenkov Detectors
22
LHCb – RICH 1
! Vertical optical layout
! Double set of mirrors:
o 4 spherical mirrors in carbon
fiber (R=270 cm, < 6 Kg/m2)
o 16 plane glass mirrors (R> 600
m)
o Mirror coating: Al+MgF2 for
carbon fiber mirrors and Al
+SiO2+HfO2 for glass mirrors
! Photon detectors located outside
the detector acceptance
! Total material budget: 8% X0
Genova, 15/4/15
Lecture 4: Particle Identification - Cerenkov Detectors
31
Transition Radiation
See: Lecture 3
Transition radiation occurs if a relativist particle (large γ) passes the
$34,+,($@4/($
+B$ $'8,C/$'8,5+$9DDD$/.*+$EF&'1
boundary between two media
with different refraction indices ...
8'8*7*+1$,&-/&$9G$
+&*6$6,()+'(+$*(+,$'(,+4/&=$3&,
[predicted by Ginzburg and Frank
1946; experimental confirmation 70ies]
Number of Events
Effect can be explained by
rearrangement of electric field ...
transition
radiation
n1
n2
Rearrangement of electric field
yields transition radiation
Energy loss distribution for 15 GeV
pions and electrons in a TRD ...
Energy deposit [keV]
ALICE TRD
cathode pads
pion
electron
amplification
region
anode
wires
cathode
wires
drift
region
Drift
Chamber
primary
clusters
entrance
window
x
Radiator
z
pion
TR photon
electron
Transition Radiation [TR]
for charged Particles with γ > 1000
ALICE TRD
cathode pads
pion
electron
amplification
region
anode
wires
cathode
wires
drift
region
Drift
Chamber
primary
clusters
entrance
window
x
Radiator
Avalanche
near anode wires
[high field]
z
TR-Signal
Gas: Xenon
[High γ-absorption]
pion
TR photon
electron
Transition Radiation [TR]
for charged Particles with γ > 1000
Particle ID – Comparison
π/K Separation
[Comparison of different PID methods
RICH Cherenkov
Threshold Cherenkov Counter
Time-of-Flight
dE/dx
0.1
DISC
Multiple dE/dx
1
10
Transition Radiation
102
103
104
Momentum p [GeV]
MOMENTUM MEASUREMENT
Good tracking detector--> knowing the magnetic field I can measure the momentum of the
particle -->p=mβγc
Momentum measurement
B
B
CERN Summer Student Lectures 2003
Particle Detectors
Christian Joram
I/18
Introduzione ai rivelatori di particelle
misure di quantità di moto
p
qB
con p in GeV/c e carica unitaria
R=
• Curvatura in campo
magnetico
– costante, ortogonale
alla velocità
10 9 ⋅1.6 ⋅10 −19
p = p [ GeV c ] ×
3 ⋅10 8
10 9 ⋅1.6 ⋅10 −19
p⋅
8
10 p
3
⋅10
R=
=
1.6 ⋅10 −19 ⋅ B
3 B
p ≈ 0.3RB
L ≈ Rθ per angoli non troppo grandi
L
BL
θ = = 0.3
R
p
0.3
θ=
Bdl (se B non è uniforme)
p ∫
0.3
p=
Bdl
θ ∫
σ ( p) σ (θ )
p
=
=
σ (θ )
p
θ
0.3∫ Bdl
• Il valore di p si può ricavare dall’angolo di
deviazione
• a parità di errore sull’angolo (p)/p aumenta
linearmente con p
AA 2008/2009
Cesare Voci - Roberto Carlin
3
I want tracking detector with a good position resolution in a way
having a better resolution for the momentum p
Introduzione ai rivelatori di particelle
misura della deflessione
In reality Never use two
points at least 4
•
B
•
la misura di bending
richiede due misure di
direzione
almeno due punti prima e
dopo il magnete
x 2 − x1
d
1
2
σ (θ ) =
σ 2 ( x1 ) + σ 2 ( x 2 ) =
σ ( x)
d
d
θ bending = θ1 − θ 2
θ≈
x2
x1
(
d
)
σ θ bending = 2σ (θ ) =
2
σ ( x)
d
σ ( p)
p
2p
=
σ (θ ) =
σ ( x)
p
0.3∫ Bdl
0.3d ∫ Bdl
Esempi
∫ B dl = 1Tm
d = 1m
σ ( p)
= 1.3 ⋅10 −3 p
p
σ ( x ) = 200 µ m
con p in GeV /c
p = 1GeV / c → σ ( p ) p =1.3 ⋅10 −3 ≈ 0.1%
p = 10GeV / c → σ ( p ) p =1.3 ⋅10 −2 ≈ 1%
p = 100GeV / c → σ ( p ) p =1.3 ⋅10 −1 ≈ 10%
AA 2008/2009
Cesare Voci - Roberto Carlin
4
Gaseous detector--> higher momentum particle --> good position
resolution
What can I do to reduce the momentum error?
- Increase the magnetic field--> not often
- decrease the resolution of the position
Introduzione ai rivelatori di particelle
misura della deflessione
• misura di momento attraverso la deflessione
– adatta a misure di fasci
– misure in esperimenti a bersaglio fisso
– misure di muoni
• misure multiple di bending in ferro magnetizzato
• alternativa
– misura della sagitta
AA 2008/2009
Cesare Voci - Roberto Carlin
5
Introduzione ai rivelatori di particelle
misura della sagitta
R
/2
s
L ≈ Rθ
L
L2
θ2
s : L 2 = L 2 : (2R − s) → s ≈
=R
8R
8
BL2
s = 0.3
(se B è uniforme, p in GeV/c)
8p
σ (p) σ (s) 8σ (s)
=
=
2 p
p
s
0.3BL
• di nuovo
(p)/p cresce con p
– misura della traccia all’interno del
campo magnetico
– si può migliorare l’errore misurando in
più punti
• oltre che, ovviamente, aumentando B, L e la
risoluzione del singolo punto
AA 2008/2009
Cesare Voci - Roberto Carlin
6
Introduzione ai rivelatori di particelle
misura della sagitta
• La misura della sagitta deve essere fatta
con almeno 3 punti
x + x3
s = x1 − 2
s=x2-(x1+x3)/2
2 x
σ ( s) =
x2
x3
1
3
σ ( x)
3
σ (p) σ (s)
2
σ ( x) →
=
=
p
2
p
s
0.3BL2
8
3/2--> because I'm measuring 3 points
• Se si misura con più punti la traccia all’interno del
campo magnetico, si arriva alla seguente relazione:
σ (p)
σ (x)
= 720 /(N + 4)
2 ⋅p
p
0.3BL
Esempi
B = 1.4T L = 1.5m σ ( x ) = 200µm N = 100
σ ( p)
= 5.6 ⋅10 −4 p
p
con p in GeV/c
p = 2GeV /c → σ ( p) p =1.1⋅10 −3 ≈ 0.1%
p = 20GeV /c → σ ( p) p =1.1⋅10 −2 ≈ 1%
p = 200GeV /c → σ ( p) p =1.1⋅10 −1 ≈ 10%
σ ( p) p =100% → p ≈ 2TeV
AA 2008/2009
Cesare Voci - Roberto Carlin
7
Momentum measurement
Momentum measurement
mv 2
L
r
x
B
s
= q (v ´ B ) ®
pT (GeV c) = 0.3Br
y
pT = qBr
(T × m)
L
0.3L × B
= sin q 2 » q 2 ® q »
2r
pT
r
q2
0.3 L2 B
s = r (1 - cosq 2 ) » r
»
8
8 pT
q
the sagitta s is determined by 3 measurements with
error s(x):
s = x2 - 12 ( x1 + x3 )
s ( pT )
meas.
=
pT
s (s)
s
3
s ( x)
2
=
s
=
3
s ( x) × 8 pT
2
2
0.3 × BL
for N equidistant measurements, one obtains
(R.L. Gluckstern, NIM 24 (1963) 381)
s ( pT )
meas.
=
pT
s ( x) × pT
2
0.3 × BL
720 /( N + 4)
(for N ³ »10)
ex: pT=1 GeV/c, L=1m, B=1T, s(x)=200µm, N=10
s ( pT )
pT
meas.
» 0.5%
CERN Summer Student Lectures 2003
Particle Detectors
(s » 3.75 cm)
Christian Joram
I/19
Multiple Scattering
Scattering
An incoming particle with charge z interacts with
a target of nuclear charge Z. The cross-section
for this e.m. process is
2
æm cö
ds
1
= 4 zZre2 çç e ÷÷
4
dW
è bp ø sin q 2
Rutherford formula
ds/dW
scattering angle q = 0
u Cross-section for q ® 0 infnite !
u Average
q
Multiple Scattering
Sufficiently thick material layer
® the particle will undergo multiple scattering.
L
ian
Gauss
P
rplane
sin -4(q
/2)
qplane
q0
0
RMS
q 0 = q plane
=
CERN Summer Student Lectures 2003
Particle Detectors
q plane 2 =
Christian Joram
qplane
1 RMS
q space
2
I/20
Multiple scattering
A charged particle traversing a medium is deflected by many small-angle scatters,
mostly due to Coulomb scattering from nuclei as described by the Rutherford cross
section
! For many small-angle scatters the net
scattering and displacement distributions
are Gaussian via the central limit theorem
! Less frequent “hard” scatters produce
non-Gaussian tails
! x/X0 is the thickness of the scattering
medium in radiation lengths
! Parameterization accurate to 11% or
better for 10 3 < x/X0 < 100
Genova, 31/1/2017
Lecture 2: Interaction of particles in matter
38
Multiple scattering effect
Momentum measurement
q0 µ
Approximation
1
p
L
X0
X0 is radiation length of the medium (discuss later)
Back to momentum measurements:
What is the contribution of multiple scattering to
remember
s ( p)
pT
?
µ s ( x) × pT
pT
s ( x)
s ( p)
s ( p)
MS
1
µ q0 µ
p
pT
Text
More precisely:
s ( p)
pT
MS
= 0.045
MS
= constant
independent
of p !
1
B LX 0
s(p)/p
total error
s(p)/p
meas.
s(p)/p
MS
p
• ex: Ar (X0=110m), L=1m, B=1T
CERN Summer Student Lectures 2003
Particle Detectors
Christian Joram
s ( p)
pT
MS
» 0.5%
I/21
Radiation Protection
There is no direct evidence
of radiation-induced genetic effects in
humans, even at high doses. Various
analyses indicate that the rate of
genetic disorders produced in
humans is expected to be extremely
low, on the order of a few disorders
per million live born per rem of
parental exposure.
The potential biological effects and damages caused by
radiation depend on the conditions of the radiation exposure.
E' meglio essere esposti a neutroni o a fotoni?
Basta pesare a che tipo di interazioni hanno le due
particelle con la materia
It is determined by:
quality of radiation
quantity of radiation
FOTONI --> pair, Compton... che produce
elettroni di bassa energia i quali perdono energia con BB
NEUTRONI-->nucleo che segue la BB
Un nucleo perderà invece molta energia in poca
unità di lunghezza
received dose of radiation
exposure conditions (spatial distribution)
The different kinds of radiation have different energy loss effects LET.
Energy loss effects depends on nature and probability of interaction
between radiation particle and body material.
Particles with high energy loss effects cause typically greater damage.
To normalize these effects as an empirical parameter the
Relative Biological Effectiveness RBE of radiation for producing a
given biological effect is introduced:
The RBE for different kinds of radiation can be expressed in terms of
energy loss effects LET.
For low LET radiation, Þ RBE µ LET, for higher LET the RBE
increases to a maximum, the subsequent drop is caused by the overkill
effect.
RBE--> how much a particle can be dangerous
Alpha particle --> smallest nucleus--> the relative biological effect
higher than the on of a proton or of a photon
These high energies are sufficient to kill more cells than actually available!
Radiation can cause immediate effects (radiation
sickness), but also long term effects which may occur many
years (cancer) or several generations later (genetic effects).
Biological effects of radiation result from both direct and
indirect action of radiation.
Direct action is based on direct interaction between
radiation particles and complex body cell molecules, (for
example direct break-up of DNA molecules)
Indirect action is more complex and depends heavily on the
energy loss effects of radiation in the body tissue and the subsequent
chemistry.
1. Radiation deposits energy into the body tissue by energy
loss effects
compton scattering, photo-excitation for g- and X-rays
scattering and ionization processes for a-, p, n-particles (LET)
2. Energy loss causes ionization and break-up of simple body
molecules:
H2O ® H+ + OH3. OH- radical attacks DNA-molecule.
4. Resulting biological damage depends on the kind of alteration and
can cause cancer or long-term genetic alterations.
The time scales for the short and long term effects of radiation are
symbolized in the figure and listed in the table
Skin Effects
The first evidence
of biological effects of
radiation exposure appears
on the exposed skin.
The different stages
depend on the dose and on
the location of the exposure.
The first (prodomal) symptoms show up after » 6 hours
These symptoms subside during the
latent period, which lasts between one
(high doses) and four weeks (low doses)
and is considered an incubation period
during which the organ damage is
progressing
The latent period ends with the onset of
the clinical expression of the biological
damage, the manifest illness stage, which
lasts two to three weeks
Survival of the manifest illness stage practically guaranties full recovery
of the patient
The severity and the timescale for the acute radiation syndrome
depends on the maximum delivered dose.
The first symptoms show up after » 6 hours
If the whole body exposure exceeds a critical threshold rate of
50 -100 rad the symptoms show up more rapidly and
drastically.
An Alpha particle of few MeV can be dangerous?? yes
because they can be inhaled and so be dangerous!!
GLOSSARY
Radiation:
In the context of this talk on radiation effects,
radiation: The transfer of energy by means of a
quantum (particle or photon).
Note: electromagnetic radiations with energy below the
X-ray band are not included here. Excluded: UV,
visible, thermal, microwave and radio-wave radiations.
Quanta:
wave behavior → particle behavior
UV
energy
RADIATION: ubiquitous,
problem, hazard, tool
NATURAL human
environment (all of us)
EXTENDED NATURAL
environment
• natural radioactivity of • satellites (various
materials
orbits)
• sea level cosmics
• deep space missions
• shuttle
• high altitude avionics
ARTIFICIAL environment
• HEP experiments
(collider halls)
• radiation therapy
facilities
• industrial accelerators
and sources
• nuclear plants
accelerator environments
SCIENCE
• High Energy Physics
• structure of matter
(synchrotron facilities)
• materials science
• ...
MEDICINE
INDUSTRIAL
• diagnostics (X-rays, PET)
• artificial isotopes
• oncologic treatment
• plastics
• composite materials
• semiconductors
• sterilization
• ecology
• ...
cartoon active volume and surroundings
primary
induced
radioactivity
active volume
the behaviour
of active
volumes may be
perturbed by
radiation
delayed
emission
secondaries
delta rays
(electrons)
natural
radioactivity
surrounding material
Radiation:
• natural (radioactivity of materials, geological, technological history)
• prompt (directly associated with accelerated beam or exposure; ON/OFF)
• induced (residual activation with beam off due to previous exposure; half-life)
TID,DDD,SEE
radiation damage of electronics
depends on technology used
Depending on particle type and energy, in a given detector or system,
macroscopic effects of radiation
can be classified into THREE MAIN GROUPS:
GROUPS
cumulative effects
TID (total ionization dose, surface damage)
DDD (displacement damage dose, bulk damage)
transient effects
SEE (single event effects)
Radiation Effects in the time domain
cumulative dose effects:
effects that change with continuity (gradually) with increased exposure
to radiation. Damage/deterioration can be monitored until it goes too far.
Predictable.
• tell-tale concepts and words:
• small energy transfers,
• accumulation of effects,
• gradual parameter shifts (thresholds, leakage currents, type inversion,...)
• fluence
• Dose
• ...
Single Event Effects:
effects that occur stochastically (suddenly).
Not predictable on event to event basis. One speaks of PROBABILITIES
• tell-tale concepts and words: sudden anomalous signal; catastrophic consequences of a
rare event; sooner or later; a matter of time; stochastic; probabilities; cross-sections; flux
(luminosity); evaluation of risk; redundancy (backup); should have know better; bad luck;
voodoo...
in perspective
Particle Radiation Effects in
Scientific Equipment
Particle
radiation
Charging
• Biasing of
instrument
readings
• Pulsing
Ionizing &
Non-Ionizing
Dose
Single
Event
Effects
Degradation of:
• μ-electronics
•Data
corruption
• silicon sensors
•Noisy
Images
• Power
drains
• solar cells
•System
shutdowns
• Physical
damage
• optical
components
•Circuit
damage
direct effects in electronics
material
Surface
degradation
Erosion
Degradation of:
• thermal,
electrical, optical
properties
• structural
integrity
Victor Hess discovered
cosmic rays in 1912
in balloon excursions
A dangerous discipline!
but full of treasures
• fundamental role of
cosmic ray research
in history
particle physics
• discoveries
• techniques
• theory
• discoveries
• techniques
• theory
Most
visual techniques
need trigger!
Even in normal human activities
things are not completely “safe”!
extensive
air shower
15 km altitude
max density of
ionizing particles
(Pfotzer 1936)
Under 20 km altitude neutrons dominate as
cause of SEE in avionic systems!
In mountains and even at sea level there
are enough neutrons to be a concern for
electronics that play vital roles (e.g. pace
makers in CMOS electronics; power
devices for train locomotives)
NOTE: neutron flux at sea (ground) level
105 neutrons/cm2-year with E>20 MeV
which may cause SEE in electronics
Harsh Environment above Earth’s Atmosphere
physical qualities
and quantities
NEED TO
understand/define
• types of particles (p, e, γ, n, π, K, ions,...)
quality and
quantity
of radiation
• energy of particles
• how many particles (flux/fluence)
• chances of certain effects occurring (cross-sections;
thresholds)
• effects predictable (total dose) or stochastic (bad luck)
• sources predictable or stochastic
properties
of target
• material (silicon, plastic, water...)
• active devices (memories, diodes,..., living cells )
• active volumes (different sensitivities, how many,
where, ...)
Words that need to be
understood
• flux, fluence, exposure
• activity, luminosity
• dose
• stopping power = (dE/dx)ele + (dE/dx)nucl
• LET
• NIEL
• Single Event Effect cross-section
physical quantities
basic radiation damage
measurement quantities
• Flux (φ) is no. of particles per unit area and per unit time:
Formula
Measurement Unit
φ = Particles/(Area×Time)
Particles/(cm2×s)
• Fluence (Φ) is no. of particles per unit area
(time integral of the flux):
Formula
Φ = ∫φ dt = Particles/Area
Measurement Unit
Particles/cm2
Dose(D)
(D)isisenergy
energydeposited
deposited by
by radiation
radiation per
per unit
unit mass:
mass:
••Dose
Formula
Formula
MeasurementUnit
Unit
Measurement
D=E/M
D=E/M
J/kg
J/kg
physical quantities
!
activity
Unit: 1 bequerel (Bq) = 1 disintegration/s
1 curie (Ci) = 3.7 × 1010 Bq
typical activity of Co60 source for radiotherapy ∼ 1 kCi
geological sample activity ∼ 0.1 Bq/s
!
Luminosity
N1, N2 number of particles
A interaction area (size of beam)
ν collision frequency
N1 N 2
L=
×ν
A
R = ∑ Ri = ∑σ i L = Lσ tot
i
R particle production rate = activity
σi cross-section of ith channel
i
GLOSSARY
parameter
radioactivity
Absorbed dose
(D)
Dose equivalent
(DE=D × Quality)
Q=1 for photons;
Q=20 for alpha
Exposure
[in air]
(for X-rays
and gamma
only)
energy
Definition
Rate of
radiation
emission
(transformation
or
disintegration)
Energy delivered
by radiation per
unit mass of
irradiated
material
Dose in terms of
biological effect
Expresses
ability to ionize
air and create
charges that
can be collected
and measured
Capacity to
do work
Common
units
symbol
curie (Ci)
Rad
rem
roentgen (R)
joule (J)
1Ci = 37 GBq
(a large amount)
1 rad = 100 erg/g
1 rad = 0.01 Gy
becquerel (Bq)
gray (Gy)
sievert (Sv)
coulomb/kg
electonvolts
(eV)
1 Bq = 1 event
of
disintegration
per second
(a very small
amount)
1 Gy = 100 rad
1 Gy = 1 J/kg
1 Sv = 100 rem
(a large dose)
1 R = 2.58×10-4
C/kg
International
units (SI),
symbol
1 Gy air dose
equivalent = 0.7 Sv
1R ≅ 10 mSv of
tissue dose
1 eV = 1.6×10-19 J
1 keV
1 MeV
1 GeV
1 TeV
dose
Effects of typical Ionising Radiation Doses
ionising dose =
• radiobiological doses
energy imparted by ionising radiation
mass of target
1 J/kg = 1 Gray (Gy) = 100 rad
• < 5 mGy: typical annual dose of human in civilized culture
• 50 mGy: allowable annual dose for radiation worker
• 1 Gy: common dose of X-ray treatment
• 2.5 Gy: total-body lethal dose for humans and many mammals
• 60 Gy: localized dose for full cancer therapy
•
technological/industrial doses
• < 1 kGy: Teflon structurally unstable
• 15-35 kGy: sterilization
• 20 kGy (2 Mrad): curing of polyester resins
• 100-200 kGy (10-20 Mrad): curing of epoxy resins
• 200 kGy: natural rubber unusable
• 1000 kGy (100 Mrad): polyvinylchloride (PVC) unusable
• 50-100 MGy: polyimide degraded significantly
industrial process:
cross-linking of polymers
30-50 kGy
Esercizio
Qual'è la dose che un corpo di 60 kg riceve se per 30 secondi è esposto a una sorgente radioattiva di 8 gr
di Co60?Assumendo che solo l'1% dei gamma raggiungono il soggetto.
Per la geometria e l'angolo solido --> specificare la percentuale
dose
1 mGy
Typical
exposure
Dose of 1 chest X-ray
or 1 year of natural
background
Number of electron-hole pairs
and typical effect
1012 e-h pairs/cm3
• effects in insulators (charge trapping),
• minor risks in biological cells,
4×1015 e-h pairs/cm3
• transitory effects in semi-conductors,
• 50% chance death after 1 month
4 Gy
10-20 Gy
delivered to tumor in radiotherapy
10-100 Gy
Annual dose received by a satellite
100 Gy
1 MGy
• Voltage shift induced in threshold of power MOSFET.
• The current gain of a BJT may be cut down by a factor 10.
Dose in sub-detectors
of HEP experiments.
• Mechanical properties of materials
are altered.
Per radiologia --> si usa CCD
The conventional RT
The photon (and e-) beams are the most
common in RT. Cheap, small, and reliable.
The energy release is not
suitable to release dose
in a deep tumor.
But the use of
sophisticated imaging
(CT), superposition of
several beams, computed
optimization, multi-leaves
collimators and >40 year
of R&D make IMRT
effective and widespread
Dose-depth relation for γ and e-
Depth&(mm)&
Particle therapy vs Photon RT
The highest dose released at the end of the
track, sparing the normal tissue
•
•
•
Beam penetration in tissue
function of the beam energy
Dose decrease rapidly after
the BP.
Accurate conformal dose to
tumor with Spread Out Bragg
Peak (active scanning!)
Mostly&proton&
and&few&&12C&
beams&
Photons vs Particle saga…
Particle therapy
can easily show
better selectivity
wrt photon
techniques…
IMRT
Yet, randomized
clinical trials seem
the only commonly
accepted method to
assess eventual
superiority of PT
technique !
Particle therapy
Radiosurgery
Particle therapy
Charged Particle Therapy in the world
March&2014:&44&proton/7&heavy&ion&centers&
Under&construcCon:&&25&proton/4&heavy&ion&centers&
Only&in&USA&27&new&centers&expected&&by&2017&&
~2014:&122499&treated&paCents:&105743&with&p,&mainly&in&USA,&53532&
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&13119&with&12C,&mainly&in&Japan,&10993;&&
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&+&46,000&in&the&past&5&years&≈&10,000&paCents&per&year&
Yet&a&
minimal&
fracCon&of&
photon&RT&
Which is the right beam for therapy?
Beam lateral deflection
As far as money is
the main concern..
protons win easily!
If we come to
effectiveness, the
landscape can
change.
For instance,
concerning the beam
selectivity,
comparing lateral
deflection heavier
ions have less
multiple scattering
Th.$Haberer,$GSI$Report$94409,$1994$
Heavier than proton? Maybe yes (RBE..)
M.Kramer&et&al.&JoP&373&(2012),&&
•
•
TRAX&
code&
The heavier ions are much better at
killing the tumur cells with respect to
the X rays (and p) for a given !high RBE
Heavier ions have better plateau/peak
ratio (less dose to the healthy tissue in a
treatment) wrt to proton beams
Heavier is better?
Fragmentation!
Dose release in healthy tissues
with possible long term side
effects, in particular in treatment
of young patients !must&be&
carefully&taken&into&account&in&the&
Treatment&Planning&System
" Mitigation
and
attenuation of the
primary beam
" Different biological
effectiveness of the
fragments wrt the
beam
12C
"
"
Production of fragments with
higher range vs primary ions
Production of fragment with
different direction vs
primary ions
(400 MeV/u) on water
Bragg-Peak
Exp.%Data%(points)%from%Hae4ner%et%al,%Rad.%Prot.%Dos.%2006%
Simula?on:%A.%Mairani%PhD%Thesis,%2007,%Nuovo%Cimento%C,%31,%2008%
Dose beyond
the Bragg Peak :
p ~ 1-2 %
C ~ 15 %
Ne ~ 30 %
Courtesy of Andrea
Mairani
The abrasion-ablation paradigm
v
b&
Quasi^target&fragments&&
Quasi^projecCle&decay&
Cme&
• Fragments from quasi-projectile have Vfrag~Vbeam and
narrow emission angle. Longer range then beam
• The other fragments have wider angular distribution but
lower energy. Usually light particles (p,d,He)
• The dose beyond the distal part comes from the quasi
projectile contribution. Wide angular halo from the rest of
the process
Fragments from 12C beam
(Ekin=400 AMeV) on 12C
400 MeV/nucl 12C on 12C
The Z>2 produced fragments
approximately have the same
velocity of the 12C beam and are
collimated in the forward direction
The protons are the most abundant
fragments with a wide β spectrum
0<β<0.6 and with a wide angular
distribution with long tail
The Z=2 fragment are all emitted
within 200 of angular aperture
The dE/dx released by the fragment
spans from ~2 to ~100 m.i.p.
Do&not&trust&MC&too&much!&
FLUKA&
Kinetic energy (MeV/nucl)
400 MeV/nucl 12C on 12C
FLUKA&
Emission angle (Deg)
What we still miss to know about
light ions fragmentation in 2015?
Data exist at 00 or on thick target. But we need to know, for any
beam of interest and on thin target:
• Production yields of Z=0,1,2,3,4,5 fragments
# d2σ/dθdE wrt angle and energy, with large angular acceptance
# For any beam energy of interest (100-300 AMeV)
# Thin target measurement of all materials crossed by beam
ρ,A,Z
Abeam, E
Not possible a
complete DB of
measurements
X,Ex,θx,φx
Abeam , E'
ρ',A',Z'
Abeam = 12C,16O,4He,…
Y,Ey,θy,φy
We need to train a
nuclear interaction
model with the
measurements!!
Recent thin target, Double Diff
Cross Section C-C measurements
The community is
exploring the interesting
region for therapeutic
application, in particular
for the 12C beam.
Yet there is a lot of
energy range to explore in
the range 150-350 AMeV
( i.e. 5-17 cm of range…)
LNS&62AMev&C&beam&
See&M.&De&Napoli&talk&
in&this&session&(2009)&
GANIL&95AMev&C&
beam&^&E600&
collaboraCon&(2011)&
GSI&400Mev&C&beam&
FIRST&experiment&&
(2011^>??)&
12C
beam
400 AMeV
FIRST
setup @GSI
The FIRST
apparatus
Start Counter (SC): thin scintillator. NC, start of ToF and trigger
Beam Monitor (BM): drift chamber for beam direction and impact point measurements
Target (TG): A 0.5 mm gold target (4,5 M events) and a 8 mm composite target
(C/O/Cr/La/P/Ca) = (35/47/8/7/2/1)% (24 M events)
Vertex Detector (VTX): pixel silicon detector. Tracks direction θ (±40°), φ (2π)
Proton Tagger (PT): plastic scint. and scint. fibers. Position, ToF, dE/dX for θ>5° H & He
ToF Wall (TW): two layers of plastic scint. Impact position (x, y, z), Z_ID, ToF for trks θ < 5°
z
~ 70 cm
~6m
TW
x
12
TPC
BM TG
C
VTX
SC
PT
Magnet
NOT TO SCALE
The TPC didn't work
during the data
acquisition
8
Direct measurements strategy
For RBE exploitation dσ/dE is compulsory !!
• The fragments travel few µm in the target->
difficult to directly detect them, even for very thin
target (10 µm?)
• The energy loss of the fragment in the target
would be substantial and would be a severe
systematic to be evaluated
• Such a very thin target produces very few events ->
very careful control of the background.
• Possible solution from JET target techniques,
where the target is a focused flux of gas crossing
the beam in vacuum: difficult and expensive
Inverse kinematic strategy
Since shooting a proton with a given β (Ekin=200 MeV !
β=0.6) on a patient (C,O,N nuclei) at rest gives no
detection opportunity… let’s shoot a β=0.6 patient (C,O,N
nuclei) on a proton at rest and measure how it fragments!!
Then if we measure the X-section, provide we apply an
inverse velocity transformation, the result should be the
same.
• Use (as patient) beams N, O, C ions with β= 0.6 ! Ekin/
nucl=200MeV.
• Use a target made of H… but this is difficult! (I will
come to this…)
The heavy fragment (all but p,d,t,He) has ~200MeV/
nucleon kinetic energy and are forward peaked
Inverse kinematics and the target
The target can be thick as few mm, since the fragment
range is larger than several cm.
The H target could be a Liquid Hydrogen, but with little non
H material on the beam path!criogenics?
A possible solution is to use twin targets: C and
hydrocarbons. The fragmentation cross section can be
obtained by subtraction.
Simultaneous double target data
taking can to minimize systematic,
if the setup has good vertexing
C& C2H6&
capability along beam line
Heavy fragment are forward
peaked, must be separated by the
beam: very good PID capability
Dark matter
What is Dark Matter?
- By definition, dark matter is all that weakly interacts with electromagnetic
radiation
-That is, dark matter does not emit or absorb light
- Evidence of the presence of dark matter in the universe are from different
sources.
The ’invisibles’
Measurement of dark matter
Indications from Cosmology and Astronomy
No clear measurement yet
Goal: determine its mass and interaction strength with matter
Neutrinophysics
Neutrino: well establised particle
Some parameters not yet measured
Neutrino astronomy possible
Teresa Marrodán Undagoitia (MPIK)
Detection Techniques - L1
Murten, 06/2017
2 / 61
Dark matter: indications from Astronomy
Expectation: decrease of rotation velocity with radius
Measurement: almost constant velocity
Hypothesis: dark matter sphere accompanying the Galaxy
How to measure rotation velocities?
→ doppler shift of the 21 cm hydrogen line
Microwave line measured with radio antennas
Teresa Marrodán Undagoitia (MPIK)
Detection Techniques - L1
Murten, 06/2017
3 / 61
Gravitational lensing → matter distribution
Photon trajectories are curved around massive objects
The matter distribution between the source and the observer
can be reconstructed
Gravitational lensing was proposed already in 1936 by Einstein
Teresa Marrodán Undagoitia (MPIK)
Detection Techniques - L1
Murten, 06/2017
4 / 61
Galaxy-clusters collisions
Bullet cluster, D. Clowe et al. 2004
MACSJ0025 cluster, Bradac et al. arXiv:0806.2320
→ Collision of two galaxy clusters
Baryonic matter: X-ray production from the gas collision
Matter distribution: reconstructed using gravitational lensing
Teresa Marrodán Undagoitia (MPIK)
Detection Techniques - L1
Murten, 06/2017
5 / 61
Indications from Cosmology
→ Cosmic microwave background
First measurement of 2.7 K
radiation in 1964 using
telecommunications horn
antennas
Anisotropies (10−5 K) measured
by the Planck satellite
Two instruments:
low and high frequency regions
Planck Collaboration, arXiv:1502.01589
Luminous matter 5%
27% is dark matter
→ Further hit: structure formation
Teresa Marrodán Undagoitia (MPIK)
Detection Techniques - L1
Murten, 06/2017
6 / 61
… and it dominates the Universe Matter budget
Marco Selvi
Alla ricerca della Materia Oscura
Incontri di Fisica, 12th October 2018, LNF
8
What is dark matter?
An elementary particle?
Massive → explain gravitational effects
Neutral → no EM interaction & Weakly interacting at most
Stable or long-lived → not to have decayed by now
Cold (moving non-relativistically) or warm → structure formation
In the standard model of particle physics:
Neutrino fulfil most
but it is a hot dark matter candidate
→ Models beyond SM typically predict NEW particles
Neutralino in Supersymmetry, gravitino, Axion, LKP in extra dimensions,
Sterile neutrino, Super-heavy dark matter and many others
Teresa Marrodán Undagoitia (MPIK)
Detection Techniques - L1
Murten, 06/2017
7 / 61
WIMP and its production mechanism
Well motivated theoretical approach:
WIMP
(Weakly Interacting Massive Particle)
relic--> particle that where created at the beginning of the universe
In the early Universe particles are in
thermal equilibrium:
creation ↔ annihilation
¯ ↔ e+ e− , µ+ µ− , q q̄, W + W − , ZZ ...
When annihilation rate � Universe
expansion rate → ’freeze out’
Correct relic density for an annihilation
rate ∼ weak scale
→ This lecture will mainly talk about detectors for WIMPs
Teresa Marrodán Undagoitia (MPIK)
Detection Techniques - L1
Murten, 06/2017
8 / 61
The WIMP hypothesis
Weakly Interacting Massive particle
Marco Selvi - The XENON Project
Korea-Italy Bilateral Symposium
1st October 2018
6
Dark matter searches
Production at LHC
p+p→
+ a lot
Teresa Marrodán Undagoitia (MPIK)
Indirect detection
→
Direct detection
We want to detect the
interaction of the wmp
, qq, ...
Detection Techniques - L1
N→
N
Murten, 06/2017
9 / 61
A collider detector ,
The ATLAS Detector
Teresa Marrodán Undagoitia (MPIK)
Detection Techniques - L1
Murten, 06/2017
10 / 61
Indirect dark matter detection
Where? → location
Galactic center, galactic halo
Subhaloes, dwarf spheroidals, the Sun ..
Into what? → particles produced
→ , Z, H
→ qq, W + W − fragmentation into → e+ e− , pp, ⌫’s
How measured? → detector technology
Satellites or balloons measuring charged particles, ’s or X-rays
Cherenkov telescopes and large neutrino observatories
Expected particle flux:
d p < A v > dNp
=
⋅
⋅ J( ⌦),
dE
4⇡2m2 dE
J( ⌦) = � d⌦ � ⇢2 (`)d`
with ` the coordinate along the line of sight
Teresa Marrodán Undagoitia (MPIK)
Detection Techniques - L1
Murten, 06/2017
12 / 61
Direct dark matter detection
WIMP
R proportional to N_t ρ_0/m_χ σ<v>
Teresa Marrodán Undagoitia (MPIK)
ER ∼ O(10 keV)
Detection Techniques - L1
Murten, 06/2017
18 / 61
Expected interaction rates in a detector
dR
dE (E, t)
=
⇢0
m ⋅mA
d
⋅ ∫ v ⋅ f (v, t) ⋅ dE
(E, v ) d3 v
Astrophysical parameters:
⇢0 = local density of the dark matter in the Milky Way
f (v, t) = WIMP velocity distribution
No but usefull
Parameters of interest:
m = WIMP mass (∼ 100 GeV/c 2 )
= WIMP-nucleus elastic scattering cross section
Spin-independent interactions: coupling to nuclear mass
Spin-dependent interactions: coupling to nuclear spin
Teresa Marrodán Undagoitia (MPIK)
Detection Techniques - L1
Murten, 06/2017
19 / 61
Direct Dark Matter Detection
Marco Selvi
Review of direct Dark Matter searches
Preparing for DM discovery, 12th June 2018, Göteborg
8
Nuclear Recoil Energy Spectrum
Marco Selvi
Review of direct Dark Matter searches
Preparing for DM discovery, 12th June 2018, Göteborg
14
Xenon properties
Ø High A: large number of SI interactions
Ø Self shielding: high Z=54 and and high
density ρ=2.83 kg/l
Ø Scalability: possibility to build compact
detectors, scalable to larger dimensions
18 evts/100-kg/year
Eth = 5 keVnr
8 evts/100-kg/year
Eth = 15 keVnr
Ø Odd-nucleon isotopes: high A=131 with
~50% of odd isotopes. Good for SD.
Ø Wavelength 178 nm: no need for a wavelength shifter
Ø Intrinsically pure: 136Xe has very small
decay rate; Kr can be removed to <
~ppt
Ø Charge & light: highest yield among the
noble liquids
Ø “Easy” cryogenics: -100 °C
Marco Selvi - The XENON Project
Korea-Italy Bilateral Symposium
6
1st October 2018
10
Detector requirements and signatures
Marco Selvi
Review of direct Dark Matter searches
Preparing for DM discovery, 12th June 2018, Göteborg
15
Signature: spectral shape
mW = 50 GeV
Marco Selvi
Review of direct Dark Matter searches
Preparing for DM discovery, 12th June 2018, Göteborg
16
Backgrounds: Electron & Nuclear Recoils
NUCLEUS
RECOIL EVENTS
We have already
seen the nucleus
recoil when we
studied the
neutrons--> worst
background to
WIMPS detections
interaction of photons
and electron->ELECTRON
RECOIL
First basic background
Importance of detecting also the background --> find a way to
recognize the signal and the background --> measurements
that can tell us what is the signal and what is the
Background even if they seem the same thing
Marco Selvi
Review of direct Dark Matter searches
Preparing for DM discovery, 12th June 2018, Göteborg
19
WIMP direct detection
Marco Selvi - The XENON Project
Korea-Italy Bilateral Symposium
1st October 2018
7
Direct Detection of WIMPs
WIMP
• Elastic collision with atomic nuclei
• The recoil energy of the nucleus is:
!2
q
µ2 v 2
ER =
=
(1 ! cos" )
2 mN
mN
ER
!2
• q = momentum transfer q = 2 µ 2 v 2 (1 ! cos" )
• µ = reduced mass (mN = nucleus mass; m! = WIMP mass)
µ=
m! m N
m! + m N
• v = mean WIMP-velocity relative to the target
WIMP
• " = scattering angle in the center of mass system
3
Backgrounds: external sources
Marco Selvi
Review of direct Dark Matter searches
FV= fiducial volume
Preparing for DM discovery, 12th June 2018, Göteborg
20
Natural Radioactivity
Marco Selvi
Alla ricerca della Materia Oscura
Incontri di Fisica, 12th October 2018, LNF
34
Underground laboratories
Marco Selvi
Alla ricerca della Materia Oscura
Incontri di Fisica, 12th October 2018, LNF
35
Backgrounds: internal and surface sources
, distillation, dust removal
Marco Selvi
Alla ricerca della Materia Oscura
Incontri di Fisica, 12th October 2018, LNF
37
Detector Calibration
Marco Selvi
Alla ricerca della Materia Oscura
Incontri di Fisica, 12th October 2018, LNF
39
Detector Calibration: Signal & Background
Marco Selvi
Alla ricerca della Materia Oscura
Incontri di Fisica, 12th October 2018, LNF
40
Sensitivity plot in direct DM experiments
Marco Selvi
Alla ricerca della Materia Oscura
Incontri di Fisica, 12th October 2018, LNF
41
Double Phase LXe/GXe
Programma Lab I
1. Elementary particles interaction with matter. Energy loss. Bethe-Bloch formula. The "range" of
particles. Bremsstrahlung.
Photons: photoeletticr effect, Compton scattering, pair production.
Single and multiple scattering. Neutron interactions.
2.General features of particle detectors. Sensitivity, energy resolution, efficiency of a detector.
3. Scintillators detectors. Organic and inorganic scintillators. Working principles. Light guide.
Photomultipliers. (The scintillator detectors used as trigger system, Time of Flight and event veto).
4. Ionization detectors. Ionization phenomenology and gas transport. The proportional counter- The
MWPC. The drift chamber. The TPC and TEC. The RPC's
5.The cherenkov detectors
Analysis of the signal not done but if we are curious present on the Knoll book