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Radiation Materials for Hall-A Polarized $^3$He Target

Xiaochao Zheng,

December 7, 2001

This document summarizes thickness and radiation length for materials crossed by incident and scattered electrons for Hall-A Polarized $^3$He experiments. Information listed here can be used for radiation effect caused by internal and external bremsstrahlung, and energy losses due to ionization for incident and scattered particles.

Figure 1: Radiation materials for hall A polarized $^3$He target

  1. exit window of beam pipe, 16 mils $^a$ Be;
  2. 5cm air;
  3. entrance window of scattering chamber, 15 mils Al;
  4. target cell window, $\sim$ 130 $\mathrm{\mu}$$^b$ glass;
  5. $\sim$ 10 atm $^3$He, 1/2 of target cell length $^c$;
  6. $\sim$ 10 atm $^3$He, $(r-x_{tg})/sin\theta$, where r$\sim$1cm is target cell radius, $x_{tg}$ is x position of scattering point in hall coordinates, $\theta$ is scattering angle;
  7. target cell wall, $\sim$ 1.3mm glass $^d$;
  8. $^4$He inside target enclosure, 45.7 cm;
  9. target enclosure exit window, 16 mil Al $^e$;
  10. air gap between target enclosure and HRS, 65.1 cm for left arm and 64.2 cm for right arm;
  11. spectrometer entrance window, 14 mils Kapton;
  12. spectrometer exit window, 4 mils Ti.

material $X_0$ (g/cm$^2$) (cm) density
air 36.66 30420 1.205 g/l  $^f$
$^4$He 94.32 755164 0.1249 g/l
$^3$He 67.42 -  
Be 65.19 35.28 1.848 g/cm$^3$
Al 24.01 8.9 2.70 g/cm$^3$
Kapton 40.56 28.6 1.42 g/cm$^3$
Ti 16.17 3.56 4.54 g/cm$^3$
glass 19.5 7.04 use GE180, 2.77 g/cm$^3$

a. 1 mil=2.54 $\times 10^{-3}$cm
b. depends on cell geometry
c. depends on target chamber density in beam, 1 amg=1.25 $\times 10^{-4}$g/cm$^3$
d. depends on cell geometry
e. for E94010 it was 10 mil
f. density for gases are evaluated at 20$^\circ$ C, 1 atm

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Xiaochao Zheng 2001-12-19