Beam Diagnostics through

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Beam Diagnostics through Beamstrahlung
Status report
Marko Ternick Achim Stahl DESY Zeuthen
ECFA DESY Workshop Prague Nov 2002
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Pairs in the BeamCal
LumiCal
Substantial Fraction of the pairs are scattered
into the BeamCal Use them to measure beam
parameters
BeamCal
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5 Potential Technologies

• Sandwich Silicon/Tungsten
• Sandwich Diamond/Tungsten
• Sandwich Passive Gas Gaps/Tungsten
• Crystals Thin Photo Diodes
• Crystals Fiber Read Out

RD Project to investigate technologies
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BeamCal Two Tasks
Tagged Electrons
Measure Beamstrahlung
serious background VETO EVENTS
beam diagnostics
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Beamstrahlung
expected energy distribution nominal beam
parameters
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Beamstrahlung
nominal
sx 553 nm ? 830 nm
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Beam Strahlung
nominal
bunch tilted by 0.2 deg
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Math. Formalism
Observables Oj
Beam Parameters xi
guinea pig
O1 a11 a12 . a1i x1 O2
a21 a22 . a2i x2
. .
Oj aj1 aj2 . aji xi
Moore Penrose Inverse dx (AT A)-1 AT O or dx
AT (A AT)-1 O

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Example

• 3 Observables
• mean particle energy
• mean radius on BeamCal
• mean time of arrival

• 2 Parameters
• bunch length sz
• bunch width sx

Input sz 250 µm sx 600 nm
Measured sz 242 /- 8 µm sx 597 /- 16 nm
Nominal sz 300 µm sx 553 nm
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More Realistic Finite Granularity
GeV
Finite Granularity Ideal Resolution 16 Observables
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Observables Example
Angular Distribution
nominal
beam tilted by 0.2 deg
U
U
R
R
L
L
D
D
O7 (L R) / (U D) O8 U /D
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Transfer Matrix A
arsz
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Transfer Matrix A
aEsz
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Results 1
6 parameter test
nominal input measured
sx left 553 nm 600 nm 614 nm
sx right 553 nm 600 nm 574 nm
sy left 5 nm 12 nm 15 nm
sy right 5 nm 8 nm -3.4 nm
sz left 300 µm 280 µm 303 µm
sz right 300 µm 250 µm 221 µm
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Results 2
6 parameter test
nominal input measured
sx both 553 nm 600 nm 614 nm
sy both 5 nm 8 nm 5.2 nm
sz both 300 µm 250 µm 227 µm
tilt x 0 µrad -700 µrad 1088µrad
tilt y 0 µrad 10 µrad 24 µrad
F 0 µrad -5.0 µrad -2.9 µrad
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Conclusions

• Possible to measure most beam parameters
• Accuracy limited by bunch to bunch fluctuations
  still to be determined more
  precisely Integrate over
  several (10?) BX
• Possible to distinguish left from right beam
• Observables still have to be optimized
• Detector resolution not included
• Real Time Analysis possible?