Mitglied der Helmholtz
-
Gemeinschaft
Lecture
9
PARTICLE DETECTORS
Detlev
Gotta
Institut für Kernphysik, Forschungszentrum Jülich / Universität zu Köln
GGSWBS'12
, Batumi, Georgia
5th Georgian
–
German School and Workshop in Basic Science
August 16, 2012
Folie
2
EXAMPLES OF COMBINED DETECTION SYSTEMS
HOW TO DETECT?
INTERACTION OF CHARGED PARTICLES WITH MATTER
“ MASSIVE NEUTRAL PARTICLES WITH MATTER
“ RADIATION WITH MATTER
DETECTOR PRINCIPLES
WHAT TO DETECT ?
Folie
3
WHAT TO DETECT ?
Folie
4
PARTICLES
Light
Heavy
p
article
detector
registration
Folie
5
PARTICLES
What
characterizes
a
particle
?
mass
M
charge
Q
Spin
intrinsic
angular
momentum
S
life
time
t
0
shape
(
for
extended
particles
)
<r
2
>
Folie
6
RADIATION
fluid
gas
„light“
fundamental
constant
: c =
speed
of
light in
vacuum
(
30⼠
湳
)
Folie
7
RADIATION
What
characterizes
waves
?
wave
propagation
velocity
c =
ln
睡we
汥湧瑨
l
晲煵敮ey
n
灡牴楣汥
灨祳楣i
usually
electromagnetic
radiation
wave
propagation
velocity
in
vacuum
c =
l n
†
“ “
“
in
medium
c‘
=
l
‘
n
<
c
index
of
refaction
n = c / c‘
Folie
8
CONSTITUENTS OF MATTER I
a
toms
10
-
10
m
atomic
shells
nucleus
electron
proton
neutron
e p n
Q
1
††††
⬠ㄠ†††††††0
††††††
M
††
M
p
/ 1836
M
p
M
p
size
<
10
-
18
m
0.8
10
-
15
m
life
time
t
0
> 10
26
y
> 10
29
y
886 s
decay
-
-
n
p e
n
Folie
9
CONSTITUENTS OF MATTER II
pions
kaons
many
more
p
K …
Q
0,
1
††††††††††
㈠
0
Ⱐ
1
M
M
p
/ 7
M
p
/ 2
size
0.6
10
-
15
m 0.6
10
-
15
m
life
time
t
0
p
26
10
-
9
s
K
12
10
-
9
s
p
0
8
10
-
17
s
K
0
S,L
9
10
-
10
/ 5
10
-
8
s
decay
p
m
n K
m
n,
…
p
0
g
g
K
0
p
+
p
,
p
0
p
0
,...
new
particles
–
unstable
being
free
Folie
10
PARAMETERS
total
energy
rest
mass
m
0
≠ 0
range
in matter
=
0
attenuation
in
matter
charge
Q ≠ 0
deflection
in
el
.
-
mag
fields
= 0
no
deflection
life
time
t
=
gt
0
decay
length
l = v
t
=
relativistic
factor
massive
particles
el
.
-
mag.
radiation
0
m
total
E
kin
E
2
c
0
m
4
c
2
0
m
2
c
2
p
total
E
+
γ
kin
E
h
pc
total
E
ν
c
v
lim
c
v
,
2
1
1
γ
β
β
γ
h
Planck
constant
= minimal
action
Folie
11
HOW TO DETECT ?
Folie
12
FORCES
•
nuclear
force
keeps
protons
and
neutrons
together
•
electromagnetic
force
keeps
electrons
around
the
nuclei
•
weak
force
makes
the
(
free
)
neutron
to
decay
•
gravitation
keeps
us
on
the
ground
strength
Standard Model
Folie
13
ELECTROMAGNETIC FORCE
a
force
is
mediated
classical
picture
quantum
world
by
field
around
a
source
field
quanta
=
particles
„light“
particles
=
photons
g
2
2
1
0
Coulomb
r
Q
Q
4
1
F
πε
electromagnetic
radiation
= E
and
B
fields
interacts
with
electric
charges
Folie
14
DEFLECTION OF CHARGED PARTICLES IN EL.
-
MAG. FIELDS
•
electric
field
•
magnetic
field
B
v
Q
x
m
F
E
Q
x
m
F
B =
const
.
circular
motion
B
plane
of
projection
T
2
B
M
Q
π
ω
ω
M
Q
r
B
Q
p
B
v
Q
r
/
mv
2
p
r
Folie
15
SIGNAL CREATION
•
via
electric
charges
•
measure
the
electric
current
I
or
voltage
U
resistor
R
U
I
c
apacitor
C
U
Q
Folie
16
INTERACTION OF
CHARGED PARTICLES
WITH MATTER
Folie
17
before
after
collision
1.
M
particle
1
>>
M
particle
2
2.
M
particle
1
=
M
particle
2
CHARGED PARTICLES
interaction
happens
by
collisions
of
particles
type 1
and
2
Folie
18
CHARGED PARTICLES I: ENERY LOSS BY COLLISIONS
1.
M
particle
>>
M
electron
e.g.
protons
,
deuterons
, …
2.
M
particle
=
M
electron
electrons
or
positrons
collisions
create
electron
ion
pairs
strongly
ionising
weakly
ionising
exponential
attenuation
with
depth
x
µ: material
dependent
attenuation
coefficient
%
3
1
R
R
Δ
for
all
elements
µx
e
)
x
(
N
no
defined
range
R!
Bragg
peak
well
defined
range
R!
Folie
19
CHARGED PARTICLES II: ENERY LOSS BY RADIATION
the
charge
polarizes
the
medium
emission
under
specific
angle
C
Radiation
if
v
particle
>
c
in
medium
Cerenkov 1930s
C
measures
the
velocity
of
the
particle
electrons
„
radiate
“
in
the
water
above
the
core
of
a
nuclear
power plant
cos
C
= 1 /
n
n =
index
of
refraction
(
small
)
dispersion
!
acoustics
analogue
: Mach‘s
cone
for
supersonic
source
„light“
blue
!
collision
x
E
radiation
C
x
E
<<
Δ
Δ
Δ
Δ
Folie
20
INTERACTION OF
MASSIVE NEUTRAL PARTICLES
WITH MATTER
Folie
21
n
eutrons
–
no
defined
range
detection
by
recoil
of
protons
(
from
hydrogen)
M
Proton
M
Neutron
i.e.
good
shieldings
are
water
concrete
(15%
water
)
paraffin
( (CH)
n
)
…
NEUTRONS
collisions
create
recoil
particles
maximum
energy
transfer
for
M
neutral
=
M
recoil
central
collision
all
energy
is
transferred
non
central
all
energies
according
to
scattering
angle
cloud
chamber
picture
neutrons
energy
transfer
D
䔠
p敲
捯llisin
D
䔠
pbability
Folie
22
INTERACTION OF
RADIATION WITH MATTER
Folie
23
RADIATION I : PHOTO
EFFECT
1.
photon
disappears
photo
electron
E
e
=
E
photon
-
E
B
2.
refilling
of
hole in
electron
shell
by
a)
emission
of
photon
or
b)
Auger
electron
emission
of
loosely
bound
outer
electron
E
Auger
B
detected
energy
E
photo
peak
E
=
E
photon
=
E
e
+
E
B
escape
peak
E =
E
photon
-
E
K
a
example
Argon
E
K
a
= 2.95
keV
photon
E
Photon
= 6.41
keV
photo
peak
escape
peak
requires
particle
nature
of
„light“
Einstein 1905
Energy
Folie
24
RADIATION II
:
COMPTON EFFECT
photon
does
not
disappear
recoil
electron
E
e
=
E
photon
–
E
photon
‘
†
捯c瑩t畯畳
†
獰散瑲畭
detected
energy
E
=
E
e
we
neglegt
E
B
of
the
electron
and
E
recoil
of
the
nucleus
because
usually
E
B
,
E
recoil
<<
E
e
proof
of
particle
nature
of
„light“
Compton 1922
billard
with
photons
and
„
quasifree
“
electrons
Δλ =λ (1−
cos
θ )
Compton
edge
=
maximum
energy
transfer
Folie
25
RADIATION III
:
BREMSSTRAHLUNG
bending
force
by
Coulomb potential
force
慣捥汥a慴楯n
†
any
distance
r
†
捯c瑩t畯畳
†
獰散瑲畭
accelerated
charged
particles
radiate
Hertz 1886
electromagnetic
waves
characteristic
X
-
rays
refilling
of
holes
in
inner
atomic
shells
a
recoil
partner
(
nucleus
)
is
needed
to
fulfil
energy
and
momentum
conservation
r
m
2
r
nucleus
Q
particle
Q
0
4
1
Coulomb
F
πε
Folie
26
RADIATION IV : PAIR
PRODUCTION
+Ze
E
p
hoton
= h
n
㸠㈠
m
electron
in general > 2
m
particles
at very high energies
el.
-
mag shower
e
+
e
–
g
-
casca摥
pair
production
and
Bremsstrahlung alternate
shower
may start with photon
or
electron
radiation length x
0
characteristic material dependent constant
depth, where about 2/3 of the incident energy is converted
proof
of
mass
-
energy
equivalence
Blackett 1948
conversion
of
energy
into
matter
magnetic
field
B
a
recoil
partner
(
nucleus
)
is
needed
to
fulfil
energy
and
momentum
conservation
Folie
27
CHARGED PARTICLES : SUMMARY I
Fractional energy
loss.
MIPs
minimum
ionsing
particles
ρ
Δ
Δ
1
x
E
dx
dE
2
M
0
...
v
1
x
E
2
collision
Δ
Δ
T < 2
M
0
stopping
power
Folie
28
CHARGED PARTICLES : SUMMARY II
Fractional energy loss per radiation length in lead as
a function
of electron or positron energy.
Folie
29
RADIATION: SUMMARY I
cross
section
s
Z
5
s
†
敡捴in
pbability
Folie
30
RADIATION: SUMMARY II
intensity
after
layer
thickness
x
attenuation
x
)
h
(
0
e
I
)
x
(
I
ν
μ
Lambert
-
Beer law
x
)
h
(
0
e
I
)
x
(
I
ν
μ
I
o
I
x
dx
transmission
)
h
(
)
h
(
i
i
ν
μ
ν
μ
sum
of
linear
attanuation
coeff
.
Folie
31
DETECTOR PRINCIPLES
Folie
32
(Wilson)
cloud
chamber
typical
Open Day
presentations
saturated
alcohol
vapor
a
-
particle
emitting
nuclide
overheated
LH
2
bubble
chamber
(D. Glaser noble
prize
1960)
+
magnetic
field
"
beer
"
inspired
!!!
among
others
discovery
of
the
weak
neutral
current
BEBC @ CERN 73 until 80ies
3.7 T, 35 m
3
LH
2
not only HISTORY
Folie
33
CHARGE
capacitor
voltage
generator
ionising
particle
current
or
voltage
detection
charge
created
by
charged
particles
or
by
„light“
is
collected
by
applying
a
voltage
by
means
of
a
curent
or
voltage
detection
Folie
34
SCINTILLATORS produce “LIGHT”
ionisation
caused
by
charged
particles
or
light
excitation
and
delayed
light
emission
usually
in
the
UV
range
anorganic
NaI
(
Tl
), CSI, BaF
2
, …
inorganic
doped
„
plastics
“
UV light
is
converted
to
charge
at
a
photo
cathode
and
multiplied
by
a
multi
stage
photo
„
multiplier
“
Folie
35
TIME
10
ns
Folie
36
WIRE CHAMBERS I
to control avalanche
quench gases, e.g. CO
2
, CH
4
, C
2
H
6
multiplication
avalanche
gain
10
5
-
10
6
wire
chambers
tutorial
:
F.
Sauli
CERN
yellow
report
99
-
07
electron
multiplication
around
anode
(fast)
drift
of
ions
(
slow
)
typical
ion
drift
velocity
:
1
-
10 cm/(µ
s
歖
)
䅲†⁃
4
Folie
37
WIRE CHAMBERS
II
many
wires
: MWPC =
multiwire
proportional
chamber
position
resolution
†
睩we
d楳瑡湣n
瑹t楣i汬l
2m
•
(
x,y
)
-
coordinate
per pair
of
frames
•
trajectory
from
MWPC
stacks
field
configuration
Folie
38
tracking
:
cut
on
fiducial
target
volume
example
:
p
-
3
He
灮p
or
dn
WIRE CHAMBERS
III
3
He
vesssel
pion
beam
beam
defining
counters
mainly
p
carbon
reactions
protons
deuterons
MWPC 1
MWPC 2
target
beam
defining
counters
good
bad
event
Folie
39
"simple" mechanics
10 MHz rate
inside magnetic field
ZEUS
-
DESY wedge
Type
-
2 module (520 ‘straws’)
ATLAS at the LHC
individual
counters
,
timing
20
ns
HV:
coat
,
ground
: sense
wire
(
~
kV
)
typical
size
:
length
1
-
2 m,
f
mm
-
cm
resistive read out
I
left
I
right
z
D
z < 1 mm
Monte Carlo
simulation
gas filling
e.g., Ar/C
2
H
6
wall: aluminised mylar foils
anode wire:
f
20 µm
STRAW TUBES
Folie
40
time
position
external time reference,
e.g.,
plastic scintillator
trick: choose field configuration,
which keeps the nonlinearity of
time
-
to
-
position relation small
position resolution
DRIFT CHAMBERS
I
20 µm
Folie
41
The wires are arranged in layers that
pass through the cylinder at three
different angles. The set of wires that
give a signal can be used to allow
computer reconstruction of the paths (or
tracks) of all the charged particles
through the chamber.
The "drift" in the name of this chamber refers to the time it takes electrons to drift to the
nearest sense wire from the place where the high
-
energy particle ionized an atom. Any three
sense wires are only nearby in one place so a set of "hits" on these three fix a particle track in
this region. By measuring the drift time, the location of the original track can be determined
much more precisely than the actual spacing between the wires.
improved position resolution by nearest 3 wires method
inclined wires
DRIFT CHAMBERS II
Folie
42
properties:
•
full 3
-
dimensional detector
•
constant drift velocity due to the collisions
in the gas mixture (typical a few cm/µs).
•
low occupancy even for high background (high rates)
•
large dE/dx due to large gas thickness (particle identification)
idea: avoid pile
-
up many MWPC planes (typical gas thickness of 1 cm)
principle: electrons produced follow the
constant
electric field lines to a single MPWC plane
located at one end of the volume ( x
-
y coordinates on this plane)
Third coordinate, z, from the drift time of the electrons to the anode plane
STAR TPC
-
RHIC, Brookhaven
TPC
-
time
projection
chamber
David
Nygren
, 1974
Folie
43
Single Track
Track Cluster
Pixel
Tracker
•
Pixel Size
•
Occupancy
•
Charge Sharing
•
S/N
•
ExB
Drift
•
Radiation
Damage
LHC
-
10
14
/cm
2
/
yr
v
ertex
r
esolution
(20
-
30
)
m
m
IP
& Trigger
Charge Sharing
charge center of gravity
high position resolution
Folie
44
+
+
charged
particle
principle
pn diode
as almost all
semiconductor detectors
miniaturisation
Readout Chip
Sensor
arrays of soldering dots
typical x
-
y (front
-
back)
arrangements
200 µm strips
layer thickness 300 µm
SILICON MICRO
-
STRIP DETECTORS I
Folie
45
CMS
-
LHC scheme
silicon µ
-
strip module
semiconductor telescope
65/300/300/5500 µm thick
double
-
sided Si
-
strip detectors
ANKE
-
COSY
•
inner tracker
•
vertex detection
•
recoils
•
polarisation (left
-
right asymmetry)
SILICON MICRO
-
STRIP DETECTORS
II
Folie
46
EXAMPLES
OF
COMBINED DETECTION SYSTEMS
Folie
47
focal
plane
particle identification by dE/dx
2
2
2
1
p
m
T
m
v
dx
dE
counter
number
1
16
FOCAL
PLANE SPECTROMETER
for
positively
charged
particles
ANKE@COSY I: SET
-
UP
aim
:
measure
simultanuously
positively
and
negatively
charged
particles
e.g.
, pp
†
灰K
+
K
Folie
48
ANKE@COSY II: FOCAL PLANE DETECTOR
Folie
49
WASA@COSY I: SET
-
UP
aim
:
measure
photons
from
neutral
particle
decay
in
coincidence
with
charged
particles
e.g.
,
dd
†
4
He
p
0
gg
photon
detector
:
calorimeter
charged
particle
detector
:
forward
hodoscope
Folie
50
WASA@COSY II:
CALORIMETER
Folie
51
WASA@COSY III: FORWARD HODOSCOPE
Folie
52
•
Silicon Vertex
Tracker
(SVT)
-
precise
position
information
on
charged
tracks
•
Drift
Chamber
(DCH)
-
the
main
momentum
measurements
for
charged
particles
and
helps
in
particle
identification
through
dE
/dx
measurements
•
Detector
of
Internally
Refected
Cerenkov
radiation
(DIRC
or
DRC)
-
charged
hadron
identification
•
Electromagnetic
Calorimeter
(EMC)
-
particle
identification
for
electrons
,
neutral
electromagnetic
particles
,
and
hadrons
•
Solenoid (not a
subdetector
)
–
high
magnetic
field
for
needed
for
charge
and
momentum
measurements
•
Instrumented
Flux
Return (IFR)
-
muon
and
neutral
hadron
identification
•
and
more
…
Todays
detectors
comprise
...
Folie
53
EXERCISES LECTURE 9: PARTICLE DETECTORS
1.
Derive
the
nonrelativistic
relation
between
kinetic
energy
and
momentum
from
the
relativistic
energy
-
momentum
relation
.
2.
By
which
process
charged
particles
loose
kinetic
energy
in matter?
3.
Which
process
dominates
–
depending
on
the
energy
of
the
radiation
–
the
attenuation
in matter?
4.
Which
processes
are
involved
in an X
-
ray
session
at
your
medical
doctor
having
an
apparatus
labeled
25
keV
?
5.
Which
is
the
minimum
velocity
(in
units
of
speed
of
light c)
for
particles
in
order
to
produce
Cerenkov light in
plastic
material
with
index
of
refraction
n = 1.5?
6.
Which
kind
of
detector
should
be
used
to
detect
neutral
pion
decays
?
7.
How
many
planes
of
MWPCs
are
needed
to
measure
the
trajectory
of
a
charged
particle
with
and
without
the
presence
of
a
magnetic
field
B.
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