Characterisation of the charge collection properties in a segmented planar HPGe detector

Gamma-ray imaging performance of the GRI+ Compton camera

“…It is electronically segmented by 26 orthogonal strip contacts, 13 AC (p-type) vertical and 13 DC (n-type) horizontal strips on each face of the detector, which provide gamma-ray interaction-position information. Each strip has a pitch of 5.5 mm, which results in a voxelization of (5.5 × 5.5 × 8) mm 3 for each gamma-ray interaction position. This volume is reduced towards the edges of the crystal where the pitch is not uniform along the length of the strips.…”

“…The detector is electronically segmented into 24 orthogonal strips, 12 AC (p-type) vertical and 12 DC (n-type) horizontal, each with a pitch of 5 mm, as shown in figure 4. The position resolution provided from the voxelization localises a gamma-ray interaction to a volume of (5 × 5 × 20) mm 3 . The crystal has a depletion voltage of -1300 V and is operated at an applied bias of -1800 V. Each strip is connected to a PSC823C Canberra charge-sensitive preamplifier in a warm FET configuration housed inside the cryostat, which provides a gain of 200 mV/MeV measured at 1 MΩ impedance.…”

“…The crystal has a depletion voltage of -1300 V and is operated at an applied bias of -1800 V. Each strip is connected to a PSC823C Canberra charge-sensitive preamplifier in a warm FET configuration housed inside the cryostat, which provides a gain of 200 mV/MeV measured at 1 MΩ impedance. This detector has also undergone characterisation at the University of Liverpool [3].Each planar detector is housed in an aluminium cryostat of dimensions (5 × 33 × 33) cm 3 . The custom-built frame allows the cryostat separation to be manually adjusted.…”

“…Signals are upsampled using linear interpolation to 500 MHz from the 100 MHz digitiser sampling rate to provide a finer gradient for measuring rise time, which is defined as the time it takes for a signal to reach a set fraction of its maximum height from baseline. Rise time values are required for later comparison with the known rise time response of the planar HPGe detector as part of implemented PSA algorithms [3]. Rise times of 10% (t10), 50% (t50) and 90% (t90) of the signal height are identified for each preamplifier signal representing a gamma-ray interaction.…”

“…Each tier offers excellent energy resolution and Pulse Shape Analysis (PSA) algorithms improve the attainable position resolution of both planar detectors. XY-PSA methods improve the lateral position resolution of the front planar detector up to (1.1 × 1.1) mm 2 and the central planar detector up to (1 × 1) mm 2 , whilst a Z-PSA method determines the depth of an interaction within the central tier to within a millimetre, with good accuracy [3]. The device is sensitive to a wide range of gamma-ray energies (120 keV-5 MeV) and aims to produce higher resolution images than competing products, whilst remaining manoeuvrable and easily-operable for non-technical workers.…”