High-Resolution High-Count-Rate X-ray Spectroscopy with State-of-the-Art Silicon Detectors

Abstract

For the European X-ray multi-mirror (XMM) satellite mission and the German X-ray satellite ABRIXAS, fully depleted pn-CCDs have been fabricated, enabling high-speed low-noise positionresolving X-ray spectroscopy. The detector was designed and fabricated with a homogeneously sensitive area of 36 cm 2 . At 150 K it has a noise of 4 e À r.m.s., with a readout time of the total focal plane array of 4 ms. The maximum count rate for single-photon counting was 10 5 counts s À1 under at-®eld conditions. In the integration mode more than 10 9 counts s À1 can be detected at 6 keV. Its position resolution is of the order of 100 mm. The quantum ef®ciency is higher than 90% from carbon K X-rays (277 eV) up to 10 keV. New cylindrical silicon drift detectors have been designed, fabricated and tested. They comprise an integrated on-chip ampli®er system with continuous reset, on-chip voltage divider, electron accumulation layer stabilizer, large area, homogeneous radiation entrance window and a drain for surface-generated leakage current. At count rates as high as 2 Â 10 6 counts cm À2 s À1 , they still show excellent spectroscopic behaviour at room-temperature operation in single-photon detection mode. The energy resolution at room temperature is 220 eV at 6 keV X-ray energy and 140 eV at 253 K, being achieved with Peltier coolers. These systems were operated at synchrotron light sources (ESRF, HASYLAB and NLS) as X-ray¯uorescence spectrometers in scanning electron microscopes and as ultra low noise photodiodes. The operation of a multi-channel silicon drift detector system is already foreseen at synchrotron light sources for X-ray holography experiments. All systems are fabricated in planar technology having the detector and ampli®ers monolithically integrated on high-resistivity silicon.

Advanced detection systems for X-ray fluorescence excitation spectroscopy

“…The EXAFS spectra were shown to be still contaminated by a weak signal anticorrelated with the Ce L II -edge XANES signature, in full agreement with earlier predictions made by Goulon et al (1982). Apparently, a 39cell Si drift-detector, still with on-chip electronics, featuring a total active area of 195 mm 2 , was also designed (Stru È der et al , 1998 but, regrettably, ESRF was never offered the opportunity to investigate its performances for real XAS applications.…”

“…Advanced technologies now make it possible to integrate the input J.FET directly on the anode of Si drift-diodes. Pioneering works in the past decade (Radeka et al, 1989;Bertuccio, Gatti et al, 1992;Pinotti et al, 1993;Sampietro, Fasoli et al, 1995;Matsuura & Nishida, 1998;Sonsky et al, 2000) resulted in the emergence of a new generation of X-ray detectors (Stru È der et al, 1997(Stru È der et al, , 1998. Current efforts now focus on the minimization of the reset noise: this led Sampietro and his colleagues to propose a new concept of continuous reset that should result in an improved stability and a better linearity at high count rates (Guazzoni et al, 2000; Sampietro et al, 2000).…”

“…By the same time and as part of a joint EEC project, ESRF has ®nancially contributed to the design and to the evaluation on beamline ID12 of a six-element Si drift-diode with on-chip electronics (Gauthier et al, 1996(Gauthier et al, , 1997Stru È der et al 1997Stru È der et al , 1998. With a sensitive area per channel of 3.5 mm 2 , the total active area of the whole detector was only 21 mm 2 , which is quite small in view of the solid angle required by most ESRF XAS experiments.…”

Current advances in synchrotron radiation instrumentation for MX experiments

“…By monitoring the element specific fluorescence line of a heavy atom scatterer while scanning the monochromator across its absorption edge, the exact position of the peak and inflection points of the edge can be determined using a program like CHOOCH (Evans & Pettifer, 2001), to optimize the anomalous signal. The most common form of detector in use is a silicon drift detector (Struder et al , 1998) which permits input count rates of up to 10 6 photons/s. To avoid detector saturation the beam intensity must therefore be carefully optimized to keep the detector dead time below values around 10–15%.…”

Silicon drift detectors as a tool for time-resolved fluorescence XAFS on low-concentrated samples in catalysis

“…Silicon drift detectors (SDD) with an integrated junction ®eld effect transistor (JFET) can handle high count rates (Stru È der et al, 1997;Stru È der, Fiorini et al, 1998). These detectors can be operated at several hundred thousand counts per second with an appropriate energy resolution (< 300 eV), while Ge-based detectors usually show less energy resolution at these count rates [e.g.…”