1. Electron detectors for HAPPEX2 and He Design Tests with high E electrons PMT tests Installation in HRS 4

2. Focal plane Detector = 65 Mhz Dose = 2 MRad

3. Geometry Two segments geometry for HAPPEX2 Detector stack overlaps elastic line 100 x 600 mm

4. Mechanics Brass-quartz stack Light guide Filter box 5 inches PMT

5. 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

6. 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

7. -B ext <= 0.4 Gauss, r <=2 P Fe < 10 -5 - << 1 ppm -Negligible contribution in the detector asymmetry. Magnetic materials

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

9. Resolution N e/e- = 250 E/E = 18 %

10. 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

11. PMT tests PMT burle 8854 Need wide range in gain (10E3-106) : 2 bases available: - Happex - Resistive, low gain

12. 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 =5% @ 1170V -Resistive base: G/G= 2%@ 1420V

13. Installation in HRS Horizontal rails

14. Installation in HRS

15. 10 cm vertical gap between VDC and detector for scanners

16. 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

17. WEB Eveything at: www-dapnia.cea.fr/Phys/Sphn/Parity/