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) B ext at focal plane b) r Mean Moeller asymmetry -> numerical calculations. FA = M(Fe) x P(Fe) x False asymmetry B ext Polarized electrons N+N-N- Fe

-B ext <= 0.4 Gauss, r <=2 P Fe < << 1 ppm -Negligible contribution in the detector asymmetry. Magnetic materials

Test with high energy electrons h1 h2 Beam pipe Moeller dipole Trigger scintillators Hodoscope Motorized rail Selection of 2 e- of same energy

Resolution N e/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/I Anode correlations Running conditions: 40 MHz, Filter 1/10 25 e/e I=1 A with G=10 4 Preliminary results: -Happex Base G/G 1170V -Resistive base: G/G= 1420V

Installation in HRS Horizontal rails

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/