Planar LAAPDs: temperature dependence, performance, and application in low-energy X-ray spectroscopy

Abstract

An experiment measuring the 2S Lamb shift in muonic hydrogen (m À p) was performed at the Paul Scherrer Institute, Switzerland. It required small and compact detectors for 1.9 keV X-rays (2P-1S transition) with an energy resolution around 25% at 2 keV, a time resolution better than 100 ns, a large solid angle coverage, and insensitivity to a 5 T magnetic field. We chose Large Area Avalanche Photodiodes (LAAPDs) from Radiation Monitoring Devices as X-ray detectors, and they were used during the last data taking period in 2003. For X-ray spectroscopy applications, these LAAPDs have to be cooled in order to suppress the dark current noise; hence, a series of tests were performed to choose the optimal operation temperature. Specifically, the temperature dependence of gain, energy resolution, dark current,

Investigation of a continuous crystal PSAPD-based gamma camera

“…Experimental estimations of F suggested that it increases linearly with the gain and that it is approximately independent of temperature [9]- [11]. For instance, Solovov et al [9] found that F = k F M + F 0 with k F = 0.00239 ± 0.00008 and F 0 =1.87±0.02 for M > 100.…”

Improved x-ray detection and particle identification with avalanche photodiodes

“…This was the case in our previous measurement. 13 Also the large average angle of incidence in our setup increases this effect significantly. Separate averaging of both individual data sets allows to produce standard traces that accurately describe all x-ray traces between 2 keV and 10 keV.…”

“…This deteriorated the performance in our previous measurements [14][15][16] where we used Rutherford Appleton Laboratory (RAL) 108A preamplifiers with µs-long integration times (see Ref. 13, Fig. 16).…”

“…Previous tests of these APDs found 40% detection efficiency for 8.2 keV x-rays and an average energy resolution of 16% (FWHM) after calibration. 13 Our x-ray detection setup consists of two linear arrays of 10 LAAPDs each, in which each LAAPD is mounted on a separate titanium piece for efficient cooling and easy replacement. 3,13 The detector arrays are mounted inside a vacuum around 10 −5 hPa and inside a 5 Tesla magnetic field, above and below the x-ray source.…”

“…Both LAAPD/preamplifier assemblies are cooled using an external ethanol circulation system and are actively temperature stabilized at around −30 on their operating temperature. 3,13 Bias voltages were chosen to provide the best energy resolution per APD and ranged from 1.61 kV up to 1.69 kV, approximately 50 V below the breakdown voltage. The pre-amplifiers with two bipolar input transistors in cascode configuration (BFR 182 npn, BFT 92 pnp) have been used for the generation of a fast response from the large capacitance (120 pF) of the LAAPD.…”