A prototype segmented planar high purity germanium detector using wraparound lithium diffusion electrode and amorphous germanium blocking contact

Purpose Segmented high purity germanium (HPGe) detectors have been used in many experiments to measure the position and energy deposition of gamma ray interactions. Significant efforts have been made to optimize the design and simplify the fabrication process. Amorphous germanium (aGe) coating is a desirable method to realize blocking contact and facilitate the segmentation.
Method In this study, a prototype segmented planar HPGe detector is fabricated using a wraparound lithium diffusion electrode for bias voltage applying and reliable mechanical mounting. A low leakage current design is realized based on conventional chemical polishing and aGe blocking. A guard ring (GR) is used to protect the metal strip electrodes within it from the surface leakage current. The GR and strip electrodes are coated onto the aGe layer. A multichannel charge sensitive preamplifier is connected to the strip electrodes, and the signal waveforms are digitized using a multichannel 100 MS/s analog-to-digital converter.
Results and conclusion The charge collection time and amplitude are analyzed. An average energy resolution of 2 keV (full width at half maximum, FWHM) is realized at 662 keV. Charge collection is simulated via a Monte Carlo program. The spatial resolution is also estimated using the program. The front-end response and measured noise level are considered. According to the simulation results, sub-millimeter (FWHM at 122 keV) resolution can be achieved at the current noise level.