Abstract
Efficiencies of a microchannel plate detector for medium energy helium and carbon ions were determined using a recently developed time of flight technique for near surface analysis by medium energy ion scattering. This technique utilizes a pulsed beam of singly charged helium-4 or carbon- 1 2 ions with energies in the 60-140 keV range to provide enhanced energy resolution (1.2% to 2.3%) when compared to conventional Rutherford backscattering techniques using solid state detectors (around 6.5% for helium). Beam pulses having I-2 ns duration were produced by sweeping the ion beam across a 1/8 inch collimator. The microchannel plate detector was mounted at the end of a I meter flight tube. Thin (2 jig/cm'), carbon screening foils mounted on the face of the microchannel plate detector were employed to prevent the low energy component of scattered ions from reaching the detector. The depth resolution for this detector unit was found to be 14-20 A for helium in silicon and 16-22 A for carbon in silicon. The detection efficiency ranged between 24.8% to 27.2% for helium beams and 21.9% to 23.8% for carbon over the energy range examined.
Thompson, Kelly (1994). Characterization of a pulsed beam Time-of-Flight system for medium energy He+ and C+ backscattering spectrometry. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1994 -THESIS -T4734.