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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
Electron detectors for HAPPEX2 and He

4

  • Design
  • Tests with high E electrons
  • PMT tests
  • Installation in HRS
focal plane detector
Focal plane Detector

t = 65 Mhz

Dose = 2 MRad

geometry

100 x 600 mm

Geometry

Detector stack overlaps elastic line

Two segments geometry for

HAPPEX2

mechanics
Mechanics

5 inches PMT

Brass-quartz stack

Light guide

Filter box

fused quartz
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
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 materials1
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
Test with high energy electrons

Moeller dipole

Beam pipe

h2

h1

Motorized rail

Trigger scintillators

Hodoscope

Selection of 2 e- of same energy

resolution
Resolution
  • Nge/e- = 250

DE/E = 18 %

edge effects

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%

pmt tests
PMT tests
  • PMT burle 8854
  • Need wide range in gain
  • (10E3-106) :
  • 2 bases available:
  • - Happex
  • - Resistive, low gain
pmt test
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 hrs2
Installation in HRS

10 cm vertical gap between

VDC and detector for scanners

detector change
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

slide17
WEB

Eveything at:

www-dapnia.cea.fr/Phys/Sphn/Parity/

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