Electron detectors for HAPPEX2 and He
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Transcript of Electron detectors for HAPPEX2 and He
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Electron detectors
for HAPPEX2 and He
•Design•Tests with high E electrons•PMT tests•Installation in HRS
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Focal plane Detector
= 65 Mhz Dose = 2 MRad
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Geometry
Two segments geometry for HAPPEX2
Detector stack overlaps elastic line
100 x 600 mm
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Mechanics
Brass-quartz stack
Light guide Filter box
5 inches PMT
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Fused quartz
•Radiation hard (Babar, CMS, E158)
•Optical polished (15-20 Angstr)
• 92% transmission in the range [350,550] tested with optical bench and with cosmic rays
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Magnetic materials
M(Fe) -> specified ~ 1%
P(Fe) -> a) Bext at focal plane b) r
<A> Mean Moeller asymmetry -> numerical calculations.
FA = M(Fe) x P(Fe) x <A>
False asymmetry
Bext
Polarized electronsN+ N-
Fe
Fe
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-Bext <= 0.4 Gauss, r <=2
PFe < 10-5
-<AMoller> << 1 ppm
-Negligible contribution in the detector asymmetry.
Magnetic materials
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Test with high energy electrons
h1 h2
Beam pipeMoeller dipole
Trigger scintillatorsHodoscope
Motorized rail
Selection of 2 e- of same energy
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Resolution
•Ne/e- = 250
E/E = 18 %
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Edge Effects
100 x600 mm
E/E=90%
E/E=20%
•Larger resolution balanced by extra statistics.•Need to correct for correlations between two segments for final result.
Real data to be analyzed
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PMT tests
•PMT burle 8854
•Need wide range in gain (10E3-106) :
• 2 bases available: - Happex - Resistive, low gain
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PMT test
Gain/IAnode correlations
Running conditions:
40 MHz, Filter 1/10 25 e/e I=1A with G=104
Preliminary results:
-Happex Base G/G =5% @ 1170V
-Resistive base: G/G= 2%@ 1420V
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Installation in HRS
Horizontal rails
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Installation in HRS
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Installation in HRS
10 cm vertical gap between VDC and detector for scanners
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Detector Change
•Remove 1 segment in each spectro. ~4h
•Start installation of previously prepared “L” detector.
•Assembly of the 2 removed segments for the 2nd “L” ~8h
•Installation of the 2nd “L” ~6h
Could be done within 1 day Man power : 5
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WEB
Eveything at:
www-dapnia.cea.fr/Phys/Sphn/Parity/