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Electron detectors for HAPPEX2 and He PowerPoint Presentation

Electron detectors for HAPPEX2 and He

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Electron detectors for HAPPEX2 and He

4

- Design
- Tests with high E electrons
- PMT tests
- Installation in HRS

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

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.

Magnetic materials

- -Bext <= 0.4 Gauss, mr <=2
- PFe < 10-5
-<AMoller> << 1 ppm

- -Negligible contribution in
- the detector asymmetry.

Test with high energy electrons

Moeller dipole

Beam pipe

h2

h1

Motorized rail

Trigger scintillators

Hodoscope

Selection of 2 e- of same energy

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%

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:

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

Installation in HRS

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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