1. Electron Detection for Compton Polarimetry Michael McDonald Outline -Compton Effect -Polarimetry -Detectors -Diamond Results

2. What Is the Compton Effect? Describes the interaction of photons with matter Incoming photon scatters off electron Compton Scattering

3. Compton Effect con’t Can relate incoming and outgoing wavelengths using conservation of energy and momentum

4. Compton Polarimetry Used to determine polarization of a beam of electrons Necessary in experiments to know polarization accurately e.g Qweak Non-invasive technique (beam is preserved)

5. Polarimetry con't Polarization in beam determined from asymmetry in number of events detected before and after reversal of laser polarization

6. Qweak Polarimeter Typical bend angle 2.3 deg Free drift dist. 4.11m 5mm from detector edge to beam

7. Detectors Device to sense the presence of high energy radiation Gas detector -> incoming radiation ionizes gas, produces current Scintillator-> atomic excitation produces light Silicon (semiconductor) ->e - h pairs produced, collected

8. Diamond Detector

9. Why Diamond? Advantages over Silicon DiamondSilicon Atomic number614 Resistivity>10 11 ohm-cm2.3x10 5 ohm-cm Band Gap5.45 eV1.1 eV Displacement Energy43 eV/atom13-20 eV/atom Electron mobility1800 cm 2 V -1 s -1` 1350 cm 2 V -1 s -1` e-h creation energy13 eV3.6 eV

10. Diamond Detector Gold electroplated __micron thickness PCVD diamond

11. Experimental Setup Initial setup Final Setup

12. Silicon Results

13. Initial Diamond Hysteresis effect?

14. Addition of trigger scintillator A peak is found From silicon calibration, peak corresponds to approx __ eV Energy deposited

15. Cable Length Tests

16. Summary and Future Test setup created, diamond tested Diamond is found to function well as a detector Tests run to characterize performance under different conditions Next steps: apply strips to diamond