Evaluation of Si(Li) detectors for use in Compton telescopes

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Accelerators, spectrometers, detectors and associated equipment, 2003-06, Vol.505 (1-2), p.130-135
• Main Authors: Tindall, C., Hau, I.D., Luke, P.N.
• Format: Article
• Language: English
• Subjects: Advanced Compton telescope; Gamma-ray spectroscopy; Lithium-drifted silicon; Si(Li) detectors; Si(Li) strip detectors
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/S0168-9002(03)01035-0

Si(Li) detectors are currently being developed for use in large Compton telescopes. A major advantage of silicon when compared with germanium is its ability to operate at significantly higher temperatures. To determine the feasibility of using Si(Li) detectors in a Compton telescope, their performance as a function of temperature has been studied. We present leakage current, noise data and gamma-ray spectral performance at various temperatures for single 6-mm-thick planar devices. It has been determined that for detectors without a guard ring, the noise began to rise significantly around 210K. Adding a guard ring improved the leakage current by about an order of magnitude and reduced the total noise (detector plus electronics) by about 25%. The noise of the detectors with ∼130mm2 area and a guard ring did not exceed our performance goal of 2keV FWHM until the temperature was approximately 240K. For 122keV gamma rays, no evidence of ballistic deficit was seen at 8μs peaking time and bias voltages corresponding to an internal electric field of ∼1150V/cm. Some evidence of ballistic deficit was seen for 662keV gamma rays at temperatures above 220K.