Download TrainingSummerStudents2007 - SBA

BEAM PHYSICS INTRODUCTION
L.Gatignon / AB-ATB-EA
• Optics principles, optics drawings
• Momentum definition
• Collimation
• Particle production
• Passage of particles through material
• Targets, converters and absorbers
• Electron, hadron and muon beams
• Beam instrumentation and their underlying ‘physics’
• The H6 beam line
Qualitative rather than quantitative !!!
Summer 2007
Summer Student Workshop
Layout
8 beams running at the
same time
 15 test facilities
 5 installed experiments
 6.3 km of beam lines
 4 Experimental halls

Nevertheless, as the West Area beams were short and simple,
we will sometimes use one of them as an example.
Summer 2007
Summer Student Workshop
Summer 2007
Summer Student Workshop
PARTICLES IN A MAGNETIC FIELD
F
In a magnetic field, the force is perpendicular
to the velocity of the particle and to the field:
F=qvxB
B
In a uniform magnetic field the deflection of a particle depends on
the product of field B and length L of the magnet:
q [rad] = 0.3 q BL [Tm] / p [GeV/c]
BL [Tm]
For a given magnet, the length is fixed but the
field B (and hence the BL) can be controlled
via its current I.
In the experimental areas the
current is constant over the spill !
Summer 2007
Summer Student Workshop
Io
I [A]
BENDs and TRIMs
q = 0.3
BL
p
A dipole acts
like a prism:
400 GeV
350 GeV
300 GeV
250 GeV
200 GeV
Together with a collimator, a dipole
can be used to define a momentum p
The Dp depends on the gap width
Bends have a nominal deflection of the beam axis,
Trims are correctors only (nominal field is 0).
Big spectrometer magnets in the experiments are also called bends!
Summer 2007
Summer Student Workshop
QUADRUPOLES
N
S
S
N
B ~ field line density
Focus in Horizontal plane
Defocus in Vertical plane
B-field lines
or vice versa
N
S
S
N
Magnetic force
B, F, Gradient
Like an optical lense !
Distance from axis
Summer 2007
f
Summer Student Workshop
Basic optics principles
To focus in both planes one needs at least two quadrupoles (doublet)
but horizontal and vertical magnification are rather different
and there are no degrees of freedom (apart from H-V flip)
A triplet can also focus in both planes, but also:
Mx and My can be equal
Mx and My can be tuned
In the optics diagrams shown, the lines can be understood in two ways:
•
Trajectories of specific particles (with e.g. Xo = 0 or X’o = 0)
•
Drawings of transfer matrix elements
Summer 2007
Summer Student Workshop
Summer 2007
Summer Student Workshop
Summer 2007
Summer Student Workshop
Matrix elements
Xo
X1
Some optics elements
Xo’
X1’
Transfer matrix R
X1
X1’
=
R11
R12
Xo
R21
R22
Xo’
R11 Xo + R12 Xo’
=
R21 Xo + R22 Xo’
1 L
e.g. : Drift space L:
0 1
1
Quadrupole:
0
-1/f 1
(f = focal length)
Summer 2007
Summer Student Workshop
Generalisation to real systems
The matrix of a system is the product of the individual matrices:
Q2
Q1
Horiz
But also include:
Y-coordinates
Momentum p
Vert
1 L3
0 1
1 0
1/
f2 1
1 L2
0 1
1
0
1
- /f1 1
1 L1
0 1
Xo
Xo’
Doublet optics
X
X’
Y
Y’
L
6x6 matrices !
Dp/p
TRANSPORT RUN25/02/03
POSITION TYPE
METERS
STRENGTH *
H O R I Z O N T A L
*
V E R T I C A L
*
D I S P E R S I O N
T*M,T/M*M *
R11
R12
R21
R22 *
R33
R34
R43
R44 *
R16
R26
R36
R46
T/M**2*M *
MM/MM
MM/MR
MR/MM
MR/MR *
MM/MM
MM/MR
MR/MM
MR/MR *
MM/PC
MR/PC
MM/PC
MR/PC
************************************************************************************************************************************
0.000 3 TARGET
*
1.000
0.000
0.000
1.000 *
1.000
0.000
0.000
1.000 *
0.000
0.000
0.000
0.000
9.000 3
*
1.000
9.000
0.000
1.000 *
1.000
9.000
0.000
1.000 *
0.000
0.000
0.000
0.000
11.000 5 Q1
61.9865 *
0.820
9.257 -0.175 -0.751 *
1.192 12.851
0.198
2.970 *
0.000
0.000
0.000
0.000
19.000 3
*
-0.576
3.250 -0.175 -0.751 *
2.772 36.609
0.198
2.970 *
0.000
0.000
0.000
0.000
21.000 5 Q2
-61.9865 *
-1.058
2.276 -0.322 -0.253 *
2.644 35.592 -0.322 -3.955 *
0.000
0.000
0.000
0.000
30.000 3
*
-3.955
0.000 -0.322 -0.253 *
-0.253
0.000 -0.322 -3.955 *
0.000
0.000
0.000
0.000
30.000 3 FOCUS
*
-3.955
0.000 -0.322 -0.253 *
-0.253
0.000 -0.322 -3.955 *
0.000
0.000
0.000
0.000
Summer 2007
Summer Student Workshop
DISPERSION
Dispersion is necessary in secondary (tertiary) beams to define the momentum:
Momentum slit
However, for good beam performance you must:
• optimise momentum resolution
 focus at momentum slit
• get rid of dispersion at the end of the beam line  field lense
Focus at momentum slit
B1
Field lense
B2
Either B1 or B2 is the momentum reference
Summer 2007
Summer Student Workshop
Optics – general observations
• Beams
are normally small in a focus
Except when the dispersion is very large at the focus or in m beam
• Experimental
targets are normally in a focus
They want a small spot
Less sensitive to changes of angle at primary target
•A
Trim (or Bend) in a focus will NOT affect the position
of the beam at the next focus (e.g. at the experiment)
But it will affect the angle and it may improve transmission.
Trims in a parallel section have the maximum steering effect.
• Material on the beam has less effect if in a focus
Even if scattered, it particle come back to the same point
Summer 2007
Summer Student Workshop
Optics calculations
Optics drawings can be interpreted as
1. matrix element representations
2. trajectories of specific particles
For optics design the matrix element approach must be used
The TRANSPORT program calculates transfer matrix elements and adjusts
the individual parameters (f, L, etcetera) to fit the optics requirements.
The result is a TABLE with transfer matrix elements and an optics drawing.
The effect of aperture limitations (e.g. collimators) and material on the beam
can only be evaluated in the trajectory approach.
The DECAY TURTLE program is used to track individual particles though
the beam line and to provide plots of particle properties, such as positions,
angles and momenta, as well as a table of particle losses along the beam.
Summer 2007
Summer Student Workshop
TRANSPORT TABLE:
X5 DEVELOPMENT FOR 250 GEV VERSION - LGA 090490
TRANSPORT RUN 4/09/02
POSITION TYPE
METERS
STRENGTH *
H O R I Z O N T A L
*
V E R T I C A L
*
D I S P E R S I O N
T*M,T/M*M *
R11
R12
R21
R22 *
R33
R34
R43
R44 *
R16
R26
R36
R46
T/M**2*M *
MM/MM
MM/MR
MR/MM
MR/MR *
MM/MM
MM/MR
MR/MM
MR/MR *
MM/PC
MR/PC
MM/PC
MR/PC
************************************************************************************************************************************
0.000 3 X5TG
*
1.000
0.000
0.000
1.000 *
1.000
0.000
0.000
1.000 *
0.000
0.000
0.000
0.000
14.500 3
*
1.000 14.500
0.000
1.000 *
1.000 14.500
0.000
1.000 *
0.000
0.000
0.000
0.000
17.448 5 Q1
23.4981 *
0.915 16.127 -0.057
0.088 *
1.088 18.807
0.060
1.964 *
0.000
0.000
0.000
0.000
18.300 3
*
0.866 16.202 -0.057
0.088 *
1.139 20.480
0.060
1.964 *
0.000
0.000
0.000
0.000
21.248 5 Q2
23.4981 *
0.629 15.072 -0.102 -0.844 *
1.423 28.235
0.135
3.373 *
0.000
0.000
0.000
0.000
26.946 3
*
0.050 10.265 -0.102 -0.844 *
2.189 47.457
0.135
3.373 *
0.000
0.000
0.000
0.000
29.894 5 Q3
-16.4899 *
-0.252
8.357 -0.106 -0.464 *
2.446 54.349
0.038
1.255 *
0.000
0.000
0.000
0.000
30.746 3
*
-0.342
7.962 -0.106 -0.464 *
2.479 55.418
0.038
1.255 *
0.000
0.000
0.000
0.000
33.694 5 Q4
-16.4899 *
-0.681
7.055 -0.127 -0.158 *
2.440 55.712 -0.064 -1.058 *
0.000
0.000
0.000
0.000
38.496 3
*
-1.289
6.298 -0.127 -0.158 *
2.131 50.633 -0.064 -1.058 *
0.000
0.000
0.000
0.000
41.496 4 B1
2.3679 *
-1.668
5.825 -0.127 -0.158 *
1.938 47.460 -0.064 -1.058 *
0.089
0.059
0.000
0.000
42.196 3
*
-1.757
5.715 -0.127 -0.158 *
1.893 46.720 -0.064 -1.058 *
0.130
0.059
0.000
0.000
45.196 4 B1
2.3679 *
-2.136
5.241 -0.126 -0.158 *
1.701 43.547 -0.064 -1.058 *
0.396
0.118
0.000
0.000
45.896 3
*
-2.225
5.131 -0.126 -0.158 *
1.656 42.807 -0.064 -1.058 *
0.479
0.118
0.000
0.000
48.896 4 B1
2.3679 *
-2.604
4.658 -0.126 -0.158 *
1.463 39.634 -0.064 -1.058 *
0.923
0.177
0.000
0.000
49.596 3
*
-2.693
4.547 -0.126 -0.158 *
1.418 38.894 -0.064 -1.058 *
1.047
0.177
0.000
0.000
52.596 4 B1
2.3679 *
-3.072
4.074 -0.126 -0.158 *
1.225 35.721 -0.064 -1.058 *
1.668
0.237
0.000
0.000
53.296 3
*
-3.161
3.963 -0.126 -0.158 *
1.180 34.981 -0.064 -1.058 *
1.834
0.237
0.000
0.000
56.296 4 B1
2.3679 *
-3.540
3.489 -0.126 -0.158 *
0.987 31.808 -0.064 -1.058 *
2.632
0.296
0.000
0.000
56.996 3
*
-3.628
3.379 -0.126 -0.158 *
0.942 31.068 -0.064 -1.058 *
2.839
0.296
0.000
0.000
59.996 4 B1
2.3679 *
-4.007
2.905 -0.126 -0.158 *
0.749 27.895 -0.064 -1.058 *
3.815
0.355
0.000
0.000
67.771 3
*
-4.990
1.677 -0.126 -0.158 *
0.250 19.672 -0.064 -1.058 *
6.574
0.355
0.000
0.000
70.719 5 Q5
21.1651 *
-4.969
1.094
0.140 -0.232 *
0.075 18.026 -0.056 -0.074 *
7.087 -0.011
0.000
0.000
71.201 3
*
-4.901
0.982
0.140 -0.232 *
0.048 17.990 -0.056 -0.074 *
7.082 -0.011
0.000
0.000
74.149 5 Q5
21.1651 *
-4.121
0.240
0.382 -0.265 *
-0.117 19.188 -0.058
0.897 *
6.505 -0.375
0.000
0.000
75.055 3
*
-3.775
0.000
0.382 -0.265 *
-0.169 20.000 -0.058
0.897 *
6.166 -0.375
0.000
0.000
75.055 3 C1C2
*
-3.775
0.000
0.382 -0.265 *
-0.169 20.000 -0.058
0.897 *
6.166 -0.375
0.000
0.000
83.357 3
*
-0.603 -2.199
0.382 -0.265 *
-0.647 27.444 -0.058
0.897 *
3.052 -0.375
0.000
0.000
88.357 4 B2
5.0134 *
1.308 -3.524
0.382 -0.265 *
-0.935 31.927 -0.058
0.897 *
1.489 -0.250
0.000
0.000
89.017 3
*
1.560 -3.699
0.382 -0.265 *
-0.973 32.519 -0.058
0.897 *
1.324 -0.250
0.000
0.000
94.017 4 B3
5.0134 *
3.470 -5.023
0.382 -0.265 *
-1.261 37.002 -0.058
0.897 *
0.388 -0.125
0.000
0.000
94.677 3
*
3.722 -5.197
0.382 -0.265 *
-1.299 37.594 -0.058
0.897 *
0.306 -0.125
0.000
0.000
99.677 4 B2
5.0134 *
5.632 -6.520
0.382 -0.265 *
-1.586 42.077 -0.058
0.897 *
-0.004
0.001
0.000
0.000
107.457 3
*
8.602 -8.578
0.382 -0.265 *
-2.034 49.053 -0.058
0.897 *
0.000
0.001
0.000
0.000
110.405 5 Q6
-27.6117 *
10.656 -10.272
1.035 -0.904 *
-1.995 46.704
0.084 -2.463 *
0.002
0.001
0.000
0.000
117.905 3
*
18.419 -17.051
1.035 -0.904 *
-1.366 28.230
0.084 -2.463 *
0.007
0.001
0.000
0.000
120.853 5 Q7
24.0089 *
19.777 -18.152 -0.128
0.168 *
-1.235 23.285
0.007 -0.941 *
0.008
0.000
0.000
0.000
121.324 3
*
19.717 -18.073 -0.128
0.168 *
-1.231 22.842
0.007 -0.941 *
0.008
0.000
0.000
0.000
122.124 5 Q7
6.5153 *
19.487 -17.822 -0.447
0.460 *
-1.234 22.237 -0.013 -0.574 *
0.008
0.000
0.000
0.000
160.853 3
*
2.173
0.000 -0.447
0.460 *
-1.742
0.000 -0.013 -0.574 *
0.011
0.000
0.000
0.000
Summer 2007
Summer Student Workshop
Summer 2007
Summer Student Workshop
COLLIMATION
• Collimation is as important for beam quality as optics
• Optics and collimation are very much correlated
Basically we consider 4 different types of collimators:
1.
2.
3.
4.
Dump collimators (TAX)
Momentum slits
Acceptance collimators
Cleaning collimators
Sometimes individual collimators can share several functions
Summer 2007
Summer Student Workshop
1. Dump collimators (TAX)
TAX stands for Target Attenuator eXperimental areas
A TAX serves to stop the primary beam (e.g. in case of access)
or to define the beam acceptance or limit its rate (by attenuation)
primary
beam
Target
Acceptance defined by TAX
A TAX is a 1.6 m long water-cooled table with Cu, Al and Fe blocks
This table is motorised in the vertical plane
Through those blocks some holes of different diameters are drilled
Some holes contain 40 – 120 cm of Beryllium (for attenuation)
One position (+ 140 mm) is fully plugged (DUMP)
The range of the movement is interlocked (EA safe – Chain 9)
TAX are also safety elements in the Access system
Summer 2007
Summer Student Workshop
2. Momentum slit
Normally located at a dispersive focus.
The center of the gap should be at the nominal beam axis.
The aperture is proportional to the accepted momentum band,
The rate is normally also proportional to the gap.
However, the DP/p cannot be smaller than the intrinsic resolution.
Hence the need (in general) to have a rather sharp focus.
3. Acceptance collimator
Located where the beam is large (ideally even parallel),
Allows to define the angular aperture of the beam,
Affects therefore the rate as well, however non-linearly.
4. Cleaning collimator
A repetition of an earlier (acceptance) collimator.
Cleans up particles scattered on the edge of the
earlier collimator
Summer 2007
Summer Student Workshop
Intensities in a secondary beam
Secondary
primary
proton beam
x . 1012 ppp
beam
< 108 ppp
Primary
Target
x . 64 kJ
Summer 2007
Tertiary
beam
< 104 ppp
Secondary
Target
few J
Summer Student Workshop
mJ
WHAT HAPPENS TO PARTICLES IN MATTER ?
Hadronic showers (p, n, K, p, L, …)
Typical length scale: Lint
po
p, p
m
Electromagnetic showers (g, e+, e-)
Typical length scale: Xo
Muons are produced mainly via pion decay.
They traverse many metres of material with minimum energy loss: 2 GeV / m Iron)
Summer 2007
Material
Xo
Lint
Xo/Lint
Beryllium
Copper
Lead
35.3 cm
1.50 cm
0.56 cm
40.7 cm
15.0 cm
17.1 cm
0.87
0.10
0.03
Summer Student Workshop
Primary targets
Primary beam
Secondary beam
400 GeV protons
Typically p, e
Typically you want to produce:
• Protons (target serves as attenuator)
• Pions, produced in hadronic interactions
Need about 1 Lint
• Electrons, produced in electromagnetic processes
The more Xo, the lower the e+ energy coming out
Need about 1 Xo
• As few muons as possible
Put shielding (TAX) before pions decay into muons
Longer target:
• More production
• More re-absorption
Optimum around 40-50 cm
etarget
0.4
0.2
Target material with large Xo/Lint: Beryllium
Summer 2007
Summer Student Workshop
Ltgt
0
0
20
40
60
80 100 cm
Secondary beam composition
at 0 mrad production angle
The secondary particle composition
depends on the beam momentum
and on the production angle.
In the plots on the right hand side
the production angle has been fixed
at 0 milliradians.
These plots are calculated using
the partprod applet on the Web:
cern.ch/gatignon/partprod.html
The curves on the right hand side
do not take into account electrons.
At -120 GeV/c electrons are about
6-7% of the beam flux, assuming a
primary proton momentum of
400 GeV/c.
They are valid for thin Be targets.
Summer 2007
Summer Student Workshop
Particle production formula
Hadron beam intensity calculations are based on a parametrisation
of data taken by the NA20 experiment, many years ago.
A simple formula gives absolute intensities for protons, pions and kaons.
These are expressed as particles per interacting proton and per steradian.
Note that normally the beam acceptance is of the order of microsteradians:
Acceptance = p qx qy
Where qx,y are the half openings of the beam acceptance in radians.
A web interface (applet) is available to calculate the rates:
http://cern.ch/gatignon/partprod.html
These calculations are quite precise for 60 GeV/c and above.
Summer 2007
Summer Student Workshop
SECONDARY TARGETS
Example: X7 tertiary beam (now dismounted)
Secondary beam
X7 beam
-120 GeV
90% p-, 10% e1) 4 mm thick Lead target
5 – 100 GeV/c, e or p
 1 Xo ,  0 Lint
Almost all pions fly through at -120 GeV/c,
Electrons loose energy due to Bremsstrahlung
Many low-energy electrons are produced
2) 40 cm Copper target
Pure electrons
 30 Xo ,  3 Lint
Electrons are essentially absorbed
Pions have time to interact and produce low-energy pions
3)
40 cm Beryllium target
 1 Xo ,  1 Lint
Produces both pions and electrons
Summer 2007
Hadrons
Summer Student Workshop
Mixed beam
OTHER WAYS TO PRODUCE ELECTRONS
1. Electron Wobbling
g
Target
p
B3T
Large I
e-
Lead
converter
In the target, charged and neutrals are produced.
Sweep away all the charged by a strong field.
The photons fly though and convert in a lead sheet.
The produce electron-positron pairs.
Either electrons or positrons can be transported
by the beam line.
2. Use synchrotron radiation
E-loss in H3 (GeV)
30
At high energy, electrons loose energy
along the beam (like in LEP), whereas pions
do not due to their higher mass.
Therefore they follow increasingly different
trajectories, until the pions (or electrons)
can be stopped by well chosen collimation.
The currents must take the energy loss into account.
Summer 2007
Summer Student Workshop
20
10
100
200
300
Eo
Muons from pion decay
•Pion decay in p center of mass:
mp2 – mm2
p* =
= 30 MeV/c
2 mp
E* =
mp2
mm2
+
2 mp
m (p*, E*)
q*
n
= 110 MeV/c
m
• Boost to laboratory frame:
Em = gp (E* + bp p* cos q*) with bp  1
• Limiting cases:
cos q = +1 → Emax = 1.0 Ep
cos q = -1 → Emin = 0.57 Ep
Summer 2007
Summer Student Workshop
0.57 < Em / Ep < 1
SCINTILLATORS
Scintllator
Scintillating material (some plastics) produce light when traversed
by charged particles.
Light is transmitted to photomultiplier by light guide.
In the photomultiplier the light is converted into an electrical pulse.
After discrimination these pulses are counted by scalers
and the count rates are transmitted to the control system.
HV
Light
guide
PM
SIGNAL
Individual particles are counted as a function of beam conditions. Useful for monitoring,
beam tuning and as a timing signal (T0) for more complicated detectors (XCET, Cedar, XDWC).
Strobing of complicated detectors:
Cerenkov counters
XCET
XTRI
XDWC's
XTRI
XTRI
Limited to ≈ 107 particles per second.
Examples:
Summer 2007
XTRI,XTRS
FISCS
Spectrometers
X
DW
C's
BEND
XTRI
Big scintillators to count full beam
Narrow, mobile scintillators to scan through beam
Summer Student Workshop
WIRE CHAMBERS
0V
Gas
Charged particles ionise the gas.
The electrons drift to the anode wire, where the field increases,
due the extremely small radius → Gas amplification.
An electrical pulse is produced, discriminated and sent to DAQ.
The positive ions drift slowly to the cathode plane → slow detectors.
2-3 kV
Ø-20 mm
0V
d
Due to well chosen geometry each wire corresponds to a cell, electrically insulated from its neighbour.
The wire hit gives an indication about the position of the particle, resolution ±0.5 d.
Examples:
Wire chamber
XWCA
XWCD
XDWC
SPECTRO
Summer 2007
Each hit gives x±d/2 for the particle measured, limited to ≈ 107 particles per burst.
Integrate charge deposited on each wire over the burst. Depends on HV!
No information about individual particles, but profiles for 104 to 1010 ppp.
The time between the signal on the wire and the time of particle
passage (XTRI, XTRS) measures the distance between particle and wire.
Improves the resolution to about 100 mm. Rates ≤ 107 ppp.
Idem but use a simple delay line for readout. Easy to use, but ≤ 104 - 105 ppp
Measure 2 positions before and 2 after a bend.
Obtain q for the particle. As the BL of the bend is known,
the momentum of each individual particle can be measured to a few permille
Summer Student Workshop
Mirror
Threshold Cerenkov counters
light
In a medium (e.g. He or N2 gas):
particle: v/c = p/√(p2+m2)
light:
Ø
Gas
v/c = 1/n
If a charged particle goes faster than light in a medium,
it emits Cerenkov light in a cone with half-opening angle f:
f2 = 2kP - m2 /p2
HV
PM
Signal
where k depends on the gas, P=pressure.
Light is thus only emitted when Ø2 ≥ 0 !!!
The # g’s ~ Ø2 and increases from 0 at threshold to ≈ 100% at very high pressures.
Efficiency
p
p
e
P (bar)
By selecting the right operating pressure,
one type of particle has good efficiency and
the other gives no signal.
By making a coincidence with scintillator signals,
particle identification can be made.
XCET counters are better at low momenta,
CEDARS allow good separation at
high momenta (300 GeV/c),
but are more complicated and need careful tuning.
For e/p separation
XCET’s are usually operated with Helium or Nitrogen at pressures between 20 mbar and 3 bar.
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Summer Student Workshop
CEDAR Cerenkov counters
Use that Cerenkov light is emitted at a fixed angle for given p and m
Protect the 8 PM’s with a
diaphragm that lets through
only the light emitted at a
given angle (for the wanted
particle type).
Needs a very parallel beam (i.e. only for hadron and electron beams).
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Simulated light spot at PM plane:
Accept event if coincidence
in at least 6, 7 or 8 PM’s
(depending on requirements
on purity and efficiency)
E.g. p/K separation
at 75 GeV/c in West
type Cedar:
Diaphragm
PMT’s
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Summer Student Workshop
Experimental scalers
Rather than reading our instruments, the NIM signal from
any detector in an experiment can be connected to a BI scaler.
This allows to count the rate in that detector as a function of beam settings.
This is very useful for beam tuning, as it is the end user who counts!
•
•
The final beam definition for the experiment must come
from the experiment
Often experiments take rates that are too high for a
single counter. They can make logical combinations
of several counters locally (and fast) and send
a pre-scaled signal to our EXPT scaler.
For small test areas, there are 4 scalers per barrack
For big experiments, there are up to 20 scalers (NA48, NA60)
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Summer Student Workshop
CALORIMETER
HV
Principle:
Computer
Beam
Particles shower in the lead-glass block. At the end of the shower, the small
energy quanta remaining deposit their energy in the form of light.
The light is captured by a photomultiplier that transforms it into an electrical pulse.
The amount of light (thus the electrical signal) is proportional to the deposited energy.
As the energy is deposited in N quanta, the relative precision of the measurement
is limited by statistical fluctuations on N, i.e. :
s(E)/E ~ 1/E
Normally a calorimeter is used for energy measurements,
But in our case its main use is for particle identification.
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Summer Student Workshop
Electron shower:
Regular
Fully contained:
Hadron shower:
Irregular,
Partly contained:
Muon shower:
dE/dx
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Only dE/dx
Constant, small
Summer Student Workshop
Particle identification via:
Ebeam
Muons
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Hadrons
Summer Student Workshop
Electrons
Access to areas
PPX
Area
PPE
Whenever persons enter the beam area, the beam must be switched off.
In the case of the X7A this guaranteed by switching off all bends.
Instead of following the beam axis, all particles go straight, ‘miss the bend’
and are absorbed in a fixed iron beam dump (2.4 metres of iron).
In order to enter the area, each person must take a key at the PPE door.
As long as a key is missing from the door, the magnets cannot be switched on.
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Summer Student Workshop
The workshop will take place in the H6 beam:
This is a high-energy hadron, electron and muon test beam
Properties of the H6 beam:
Parameter
Value
Maximum beam momentum [GeV/c]
Maximum momentum band
±1.3%
Momentum resolution
Acceptance (mrad) – Horizontal
Vertical
< 0.1%
± 1.1
± 1.3
Maximum flux per SPS cycle:
**) Extreme radioprotection limit
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< 108
**)
Secondary target
H6 optics - test beam mode
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The H6 beam line is located in EHN1, building 887:
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Seen from the sky:
EHN1
NA48, NA60
≈ 550 meters
H6
Compass
CCC
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During the workshop you will be working in the CCC (i.e. the new
CERN Control Center) in building 874.
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Summer Student Workshop
Thanks to:
Edda Gschwendtner
EA physicist
Ilias Efthymiopoulos
“
Bruno Chauchaix
“
Olav Ullaland – Workshop coordinator, bus
These slides can be found at:
http://cern.ch/gatignon/TrainingSummerStudents2007.ppt
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Summer Student Workshop