Response of SBDs to MeV protons, tritons, and alphas: Evidence that the charged‐particle sensitive depth is not generally the depletion depth

As part of an on‐going effort to develop diagnostics for energetic charged particles from laboratory and space experiments, we examined the possibility that particle identification could be expedited by varying the applied bias voltage on silicon surface barrier detectors (SBDs). Using MeV protons, tritons, and alphas, we performed spectroscopy experiments whereby we observed changes of the energy spectrum as a function of the bias voltage. These particles were either generated via a Cockcroft–Walton linac as fusion products, or emitted from radioisotopes. The results indicate that, contrary to commonly held belief, the detector sensitive depth is not generally the depletion depth. Indeed for partially depleted SBDs the performance is not greatly degraded even for zero bias.