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Electron detectors for HAPPEX2 and He

Electron detectors for HAPPEX2 and He. 4. Design Tests with high E electrons PMT tests Installation in HRS. Focal plane Detector. t = 65 Mhz Dose = 2 MRad. 100 x 600 mm. Geometry. Detector stack overlaps elastic line. Two segments geometry for HAPPEX2. Mechanics.

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Electron detectors for HAPPEX2 and He

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

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

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

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

  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 Bext False asymmetry Fe Fe N+ N- FA= M(Fe) x P(Fe) x <A> Polarized electrons M(Fe) -> specified ~ 1% P(Fe) -> a) Bext at focal plane b) mr <A> Mean Moeller asymmetry -> numerical calculations.

  7. Magnetic materials • -Bext <= 0.4 Gauss, mr <=2 • PFe < 10-5 -<AMoller> << 1 ppm • -Negligible contribution in • the detector asymmetry.

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

  9. Resolution • Nge/e- = 250 DE/E = 18 %

  10. 100 x600 mm Edge Effects DE/E=20% • Larger resolution balanced • by extra statistics. • Need to correct for • correlations between two • segments for final result. Real data to be analyzed DE/E=90%

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

  12. PMT test Gain/IAnode correlations Running conditions: Preliminary results: 40 MHz, Filter 1/10 25 ge/e  I=1mA with G=104 -Happex Base DG/G =5% @ 1170V -Resistive base: DG/G= 2%@ 1420V

  13. Horizontal rails Installation in HRS

  14. Installation in HRS

  15. Installation in HRS 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/

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