Slide 1

Electron Detection for Compton Polarimetry Michael McDonald Outline -Compton Effect -Polarimetry -Detectors -Diamond Results Slide 2 What Is the Compton Effect? Describes the interaction of photons with matter Incoming photon scatters off electron Compton Scattering Slide 3 Compton Effect cont Can relate incoming and outgoing wavelengths using conservation of energy and momentum Slide 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) Slide 5 Polarimetry con't Polarization in beam determined from asymmetry in number of events detected before and after reversal of laser polarization Slide 6 Qweak Polarimeter Typical bend angle 2.3 deg Free drift dist. 4.11m 5mm from detector edge to beam Slide 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 Slide 8 Diamond Detector Slide 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 Slide 10 Diamond Detector Gold electroplated __micron thickness PCVD diamond Slide 11 Experimental Setup Initial setup Final Setup Slide 12 Silicon Results Slide 13 Initial Diamond Hysteresis effect? Slide 14 Addition of trigger scintillator A peak is found From silicon calibration, peak corresponds to approx __ eV Energy deposited Slide 15 Cable Length Tests Slide 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