Sensitive 3D hydrogen microscopy using high energy protons at SNAKE

The new ion microprobe SNAKE (Superconducting Nanoscope for Applied nuclear (Kern-) physics Experiments) is a tool to focus, beside heavy ions, 4–28 MeV protons to submicron beam spot size. This facility establishes a sensitive 3D microscopy of hydrogen distributions by elastic proton proton scattering. The high proton energy enables analysis at a target thickness up to some 100 μm without significant reduction of the micrometer lateral resolution. The scattered projectile and recoiled target protons are detected in coincidence using an annular silicon strip detector. It covers scattering angles from 29° to 61° and a 2.3 sr solid angle of detection. The readout electronics with a 50 ns coincidence window allows an efficient reduction of accidental coincidence events even at some 10 kHz count rates. 3D hydrogen microscopy using 17 MeV proton proton scattering is tested successfully providing a ppm detection limit in a 55 μm thick diamond plate. First measurements on CVD grown diamond show the possibility to investigate such low hydrogen content of the bulk region with micrometer lateral resolution.