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W. Morse GamCal3 RDR: Luminosity Feedback Detectors BeamCal and GamCal
Citation preview
W. Morse GamCal 1
GamCal: a Beam-strahlung Gamma Detector for Beam
Diagnostics
William M. MorseBrookhaven National Lab
W. Morse GamCal 2
GamCal Detector
• W. Morse (BNL): Coordinator• M. Ohlerich et al. (Zeuthen): beam-
strahlung simulations• B. Parker (BNL): Machine interface issues• M. Zeller, G. Atoian, V. Issakov, A.
Poblaguev (Yale): GamCal detector design
• Y. Nosochkov (SLAC): Extraction line issues
W. Morse GamCal 3
RDR: Luminosity Feedback Detectors BeamCal and GamCal
W. Morse GamCal 4
Beam-strahlung Gammas
• F = e(E + cB)• E = 0, Bmax 1KT• P 2% Pe 0.3MW• N 1.5Ne 31010 /BX
mcFrP
32 220
yzx
xycNeB
0
W. Morse GamCal 5
Beam-strahlung Pairs
• Bethe-Heitler: e → e e+e-
BH 38 mb• <E> 1GeV• Landau-Lifshitz: ee → ee e+e-
LL 19 mb• <E> 0.15GeV
W. Morse GamCal 6
Beam-strahlung Pairs
0.1m low Z
W. Morse GamCal 7
Bethe-Heitler Pairs
e → e e+e-
oy
ox
oe
oBH
ee
NNN
o
yox
oeBHee N
NN
For left and right detectors separately: N+/xy and N-/xy.
oy
ox
oo NNL
W. Morse GamCal 8
Vertical Offset E_pairs (BCAL) and E_photon
0
20
40
60
80
100
120
140
160
180
200
-300 -200 -100 0 100 200 300
offset_y/2 (nm)
E_pa
irs
(BC
AL,
TeV)
0
2
4
6
8
10
12
14
16
E_ph
oton
(MTe
V)
Ratio of Energies (BCAL)
0
0,02
0,04
0,06
0,08
0,1
0,12
0,14
-300 -200 -100 0 100 200 300
offset_y/2 (nm)E_
pairs
(BCAL)
/E_g
amm
a (1
0̂-6
)
0
0,5
1
1,5
2
Lum
inos
ity (1
0̂34
cm̂
-2/
s)
M.Ohlerich
complementary information from1. total photon energy vs
offset_y2. BeamCal pair energy vs
offset_y
ratio of E_pairs/E_gam vs offset_y is proportional to the luminosity
similar behaviour for angle_y, waist_y …see also: EUROTeV-Memo-2006-011
W. Morse GamCal 9
GamCal and BeamCal
• Measuring the beam-strahlung pairs and gammas provides robust complementary information
• Ratio of pairs to gammas is largely proportional to the instantaneous luminosity
W. Morse GamCal 10
BeamCal
• .003 < < .02 rad3.5m from IR• Pairs curl in the magnetic field• Measure the 104 beam-strahlung e+e-
pairs/BX for beam diagnostics• The distribution of the pairs on the
BeamCal contains rich information on the beam parameters of the collision (beam sizes, emittances, etc.)
W. Morse GamCal 11
GamCal Detector 180m from IR 10-4 X0 to convert beam-strahlung gammas into
e+e- pairs• Converter could be gas jet or a thin solid
converter• Dipole magnet with PT kick 0.25 GeV/c separates
the pairs from beam electrons• Calorimeters outside vacuum after magnet
measure the 1-10 GeV positrons
W. Morse GamCal 12
Statistical Error for BXN pairs and gammas full intensity
0.E+00
2.E+03
4.E+03
6.E+03
8.E+03
0 20 40 60 80 100
y angle (urad)
pairs
3.E+05
4.E+05
5.E+05
6.E+05
gam
mas
BeamCal
GamCal
W. Morse GamCal 13
Start-up?10% beam intensities
0
5
10
15
20
25
0 20 40 60 80 100
y angle (urad)
pairs
3.E+03
4.E+03
5.E+03
6.E+03
gam
mas
BeamCal
GamCal
W. Morse GamCal 14
Beam-strahlung Ze+e-Z
0
5
10
15
20
0 2 4 6 8 10 12 14 16 18 20
E (GeV)
E dN
/dE
W. Morse GamCal 15
GamCal Backgrounds from Beam Electrons
Process Background/signal
Bremsstrahlung <1%
Delta rays <1%
Landau-Lifshitz 6%
production <0.1%
W. Morse GamCal 16
Ratio of ZeeZ vs. eZ eZee
0
7
14
21
-1 0 1
log_10 (E)
Ratio
W. Morse GamCal 17
W. Morse GamCal 18
Yale IBS Design
W. Morse GamCal 19
Beam Diagnostics Detectors Conclusions
• BeamCal and GamCal provide robust complimentary information.
• GamCal backgrounds look OK – needs simulations.• Can measure, and then subtract, the GamCal
background by accelerating only one beam. • Ratio of the beamstrahlung pairs (BeamCal) to gammas
(GamCal) is largely proportional to the instantaneous luminosity.
• There is much rich information from pair distributions on BeamCal and IBS camera, which we are studying.
W. Morse GamCal 20
Extra Slides
W. Morse GamCal 21
Feed-back with Luminosity Detectors
P.N. Burrows GDE/MDI Vancouver 19/7/06
Intra-train y + y’ IP feedback simulations
0 100 200 300 400 500 6000
1
2
3x 10
34
Bunch #
Lum
inos
ity /
cm-2s-1
y position FB:restore collisionswithin 100 bunches
1 seed:
post-BBA
+ GM
+ wakes
y position scan:optimise signal in pair monitor
y angle scan
OPTIMALLUMINOSITY
W. Morse GamCal 22
BNL Magnet Division Position Stability
W. Morse GamCal 23
Achieving the ILC Luminosity Will Be a Challenge
• Bunch P- (t) {N, x, y, z, xy, x, y}• Bunch P+(t) {N, x, y, z, xy, x, y}• Instantaneous Luminosity:
oy
ox
oo NNtL
)(
x
y
W. Morse GamCal 24
IBS Camera
W. Morse GamCal 25
IBS Camera
W. Morse GamCal 26
1 2
0
21
yE
0
21
yB
+ -
0
221
212
01
2
eyeyF
y
z
W. Morse GamCal 27
Perfect Collisions
zx
NE 2
2
zyx
eeNE
3
3
W. Morse GamCal 28
Bunch width
0
100
200
300
400
500
600
400 500 600 700 800 900
Bunch width (nm)
Ener
gy in
gam
mas
(MTe
V)O
0
10
20
30
40
50
60
gammas
pairs
W. Morse GamCal 29
Bunch Width
0
5
10
15
20
25
30
400 500 600 700 800 900
Bunch width (nm)
Lum
inos
ity (1
0^33
cm
^-2/
s)
0
0.02
0.04
0.06
0.08
0.1
0.12
Lum
R
W. Morse GamCal 30
GamCal Backgrounds
Gammas
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1.E+09
-2 -1 0 1 2
log(E)
dN/d
log(
E)
BeamstBrem
1
10
100
1000
-2 -1 0 1 2log(E)
dN/d
log(
E) Delta RaysBeamst e
W. Morse GamCal 31
ZeeZ vs. eZ eZee
• Electron carries virtual gammas• Landau Lifshitz conversion of virtual
gammas
211.1ln12
minbc
ddN
W. Morse GamCal 32
Production Compared to ee
p eep 10 mbp N 0.5 mb on peak of Δ
resonancep N 0.1 mb E > 4GeV• ep e N 10-3 mb • Thus ep e N is negligible