Electron detectors for HAPPEX2 and He Design Tests with high E electrons PMT tests Installation in...
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Transcript of Electron detectors for HAPPEX2 and He Design Tests with high E electrons PMT tests Installation in...
Electron detectors
for HAPPEX2 and He
•Design•Tests with high E electrons•PMT tests•Installation in HRS
4
Focal plane Detector
= 65 Mhz Dose = 2 MRad
Geometry
Two segments geometry for HAPPEX2
Detector stack overlaps elastic line
100 x 600 mm
Mechanics
Brass-quartz stack
Light guide Filter box
5 inches PMT
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
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
-Bext <= 0.4 Gauss, r <=2
PFe < 10-5
-<AMoller> << 1 ppm
-Negligible contribution in the detector asymmetry.
Magnetic materials
Test with high energy electrons
h1 h2
Beam pipeMoeller dipole
Trigger scintillatorsHodoscope
Motorized rail
Selection of 2 e- of same energy
Resolution
•Ne/e- = 250
E/E = 18 %
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
PMT tests
•PMT burle 8854
•Need wide range in gain (10E3-106) :
• 2 bases available: - Happex - Resistive, low gain
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
Installation in HRS
Horizontal rails
Installation in HRS
Installation in HRS
10 cm vertical gap between VDC and detector for scanners
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
WEB
Eveything at:
www-dapnia.cea.fr/Phys/Sphn/Parity/