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. 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 hrs

Horizontal rails

Installation in HRS



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


WEB

Eveything at:

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


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