Criteria of choice of the front-end transistor for low-noise preamplification of detector signals at sub-microsecond shaping times for X- and γ-ray spectroscopy

Whitaker

Barnett

2017

Two GaAs p þ -i-n þ mesa X-ray photodiodes were characterized for their electrical and photon counting X-ray spectroscopic performance over the temperature range of 100 C to -20 C. The devices had 10 lm thick i layers with different diameters: 200 lm (D1) and 400 lm (D2). The electrical characterization included dark current and capacitance measurements at internal electric field strengths of up to 50 kV/cm. The determined properties of the two devices were compared with previously reported results that were made with a view to informing the future development of photon counting X-ray spectrometers for harsh environments, e.g., X-ray fluorescence spectroscopy of planetary surfaces in high temperature environments. The best energy resolution obtained (Full Width at Half Maximum at 5.9 keV) decreased from 2.00 keV at 100 C to 0.66 keV at -20 C for the spectrometer with D1, and from 2.71 keV at 100 C to 0.71 keV at -20 C for the spectrometer with D2. Dielectric noise was found to be the dominant source of noise in the spectra, apart from at high temperatures and long shaping times, where the main source of photopeak broadening was found to be the white parallel noise.

Section: B Noise Analysismentioning

confidence: 88%

High temperature GaAs X-ray detectors

Whitaker

Barnett

2017

“…The electronic noise consists of parallel white noise, series white noise, 1/f noise, and dielectric noise. 32,33 The parallel white noise takes into account the leakage currents of the detector and input junction field-effect transistor (JFET) of the preamplifier, whilst the series white noise takes into account the capacitances of the detector and input JFET of the preamplifier. The parallel white noise, series white noise, and 1/f noise were calculated for the reported detectors.…”

Section: B X-ray Spectroscopy and Noise Analysismentioning

confidence: 99%

Characterisation of Al0.52In0.48P mesa p-i-n photodiodes for X-ray photon counting spectroscopy

Butera

Krysa

et al. 2016

Results characterising the performance of thin (2 μm i-layer) Al0.52In0.48P p+-i-n+ mesa photodiodes for X-ray photon counting spectroscopy are reported at room temperature. Two 200 μm diameter and two 400 μm diameter Al0.52In0.48P p+-i-n+ mesa photodiodes were studied. Dark current results as a function of applied reverse bias are shown; dark current densities <3 nA/cm2 were observed at 30 V (150 kV/cm) for all the devices analysed. Capacitance measurements as a function of applied reverse bias are also reported. X-ray spectra were collected using 10 μs shaping time, with the device illuminated by an 55Fe radioisotope X-ray source. Experimental results showed that the best energy resolution (FWHM) achieved at 5.9 keV was 930 eV for the 200 μm Al0.52In0.48P diameter devices, when reverse biased at 15 V. System noise analysis was also carried out, and the different noise contributions were computed.

“…The FWHM at 5.9 keV experimentally observed at 20 °C was greater than the Fano limited resolution, this highlighted that there was a significant contribution from at least one of the other noise sources. The electronic noise, due to the Al0.52In0.48P photodiode and the preamplifier, consists of parallel white noise, series white noise, induced gate current noise, 1/f noise and dielectric noise [25,27,28]. The parallel white noise takes into account the leakage currents of the detector and input JFET of the preamplifier, it is directly proportional to the shaping time.…”

Section: B X-ray Spectroscopy and Noise Analysismentioning

confidence: 99%

“…The series white noise power spectral density can be approximated to the thermal noise of the JFET drain current when stray resistance in series with the JFET gate is negligible. The series white noise was calculated using the capacitance and was adjusted for induced gate current noise [25,27]. 1/f noise is instead independent from the shaping time.…”

Section: B X-ray Spectroscopy and Noise Analysismentioning

confidence: 99%

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Temperature study of Al0.52In0.48P detector photon counting X-ray spectrometer

Butera

Gohil

et al. 2016

A prototype 200 μm diameter Al0.52In0.48P p+-i-n+ mesa photodiode (2 μm i-layer) was characterised at temperatures from 100 °C to −20 °C for the development of a temperature tolerant photon counting X-ray spectrometer. At each temperature, X-ray spectra were accumulated with the AlInP detector reverse biased at 0 V, 5 V, 10 V, and 15 V and using different shaping times. The detector was illuminated by an 55Fe radioisotope X-ray source. The best energy resolution, as quantified by the full width at half maximum (FWHM) at 5.9 keV, was observed at 15 V for all the temperatures studied; at 100 °C, a FWHM of 1.57 keV was achieved, and this value improved to 770 eV FWHM at −20 °C. System noise analysis was also carried out, and the different noise contributions were computed as functions of temperature. The results are the first demonstration of AlInP's suitability for photon counting X-ray spectroscopy at temperatures other than ≈20 °C.