Imaging low-energy positron beams in real-time with unprecedented resolution

Particle beams focused to micrometer-sized spots play a crucial role in forefront research using low-energy positrons. Their expedient and wide application, however, requires highly-resolved, fast beam diagnostics. We have developed two different methods to modify a commercial imaging sensor to make it sensitive to low-energy positrons. The first method consists in removing the micro-lens array and Bayer filter from the sensor surface and depositing a phosphor layer in their place. This procedure results in a detector capable of imaging positron beams with energies down to a few tens of eV, or an intensity as low as 35 particles/s/mm2 when the beam energy exceeds 10keV. The second approach omits the phosphor deposition; with the resulting device we succeeded in detecting single positrons with energies upwards of 6 keV and efficiency up to 93%. The achieved spatial resolution of 0.97 micrometers is unprecedented for real-time positron detectors.