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ABSTRACT: Fast counting applications with energy discrimination like X-ray absorption spectroscopy require an energy resolution of some hundred eV even at highest count rates and ask for small form factors. The development, fabrication and test of a small number of 7-cell Si-drift detectors have been successfully finished at DESY fitting these claims with a good cost-versus-performance tradeoff. The monolithic 7-cell sensor chip and a corresponding readout chip are the key components of the sensor head. The module's length and wrench size amounts to 21.2 and 1.6 cm, respectively. Its active area is ~ 7 times 7 mm<sup>2</sup> and main energy range is 2.5 to 18 keV. Between ~ 5 and 20 keV the nonlinearity in a six-modules setup is well within plusmn 2% and plusmn 0.5% when uncompensated and compensated, respectively. The Cu-K<sub>alpha</sub> line width is (271 plusmn 46) eV when operated at 10degC. With the best SDD chip we achieved (223 plusmn 7) eV at 10degC and (294 plusmn 10) eV at 24degC . By selection of the three best devices the spectral resolution reaches 400 and 600 eV at 10degC and a sum-count rate of 3.3middot10<sup>6</sup> s<sup>-1</sup> and 6.7middot10<sup>6</sup> s<sup>-1</sup>, respectively. XAFS measurements have shown that the peak shift and line-width variations remain below 5 eV and 17 eV, respectively.
IEEE Transactions on Nuclear Science 07/2009; · 1.45 Impact Factor
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ABSTRACT: This paper describes a mixed-signal seven-channel ASIC in 0.35-mum BiCMOS technology for the readout of Si-drift detectors used in X-ray spectroscopy. An integral count rate of more than four million pulses per second can be achieved. Count rate- and photon energy-related changes of the input pulse shape are compensated by a baseline-holding circuit, where the baseline instability remains below 1%. Within an input dynamic range between 1.9 mV and 7.2 mV a non-linearity below 1% can be reached. The equivalent input-noise voltage amounts to 31 muV<sub>rms</sub>. At maximum output voltage a channel-to-channel crosstalk of ~0.3% was measured. The power consumption of the readout chip is ~15 mW per channel. The functionalities of the main circuit blocks as well as experimental results are presented.
Solid State Circuits Conference, 2007. ESSCIRC 2007. 33rd European; 10/2007
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ABSTRACT: A compact detector module based on Si-drift detectors with integrated junction-field effect transistors has been developed. It has been set up for X-ray absorption spectroscopy and X-ray standing-wave technique, and is usable in vacuum environment. The modules' hexagonal shape with a wrench size of 16 mm allows small distances to the samples and a compact multi-module arrangement. The monolithic 7-cell sensor has an active area of ~50 mm<sup>2</sup> and a thickness of 450 mum. It provides a spectral resolution of some hundred eV in the soft X-ray regime at room temperature. A fully differential 7-channel BiCMOS readout chip has been developed to process the detector signals at a power dissipation of 15 mW per channel. First spectral measurements with energies up to 43 keV have been performed with the prototype module. A rate-dependent energy-peak shift remains below 3% at integral photon- count rates of more than 6 Mcts/s. The deviation from the linear regression is within plusmn2% in the energy range between 6 and 20 keV. The on-chip gain variations are below 3.4%.
Nuclear Science Symposium Conference Record, 2007. NSS '07. IEEE;
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IEEE Trans. Nucl. Sci. 56(2009)3,1666-1670.
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J. Synchrotron Rad. 16(2009),293-296.
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ABSTRACT: Ten detector modules based on monolithic 7-cell Si-drift detectors with integrated junction field effect transistors (JFETs) are currently under production. The modules’ hexagonal shape with a wrench size of 16 mm allows very small distances to the samples and a compact multi-module arrangement. The sensors have active areas of and a thickness of . A proper spectroscopy operation of all modules was obtained by five common supply voltages and a 6th voltage which must be individually adopted. Detector capacitances varied from 83 to 145 fF, where statistical spreading caused by device mismatch amounts to 0.4%. On-chip scattering of the JFET's transconductance and source potential in a source-follower configuration are around 1%. Their spreading caused by process variations and device mismatch remain below 8%. Typical spectral resolution and non-linearity is about 300 eV and below 1% between 4.5 and 18 keV, respectively. After irradiation with a total dose of the resolution decreases by ∼40%. By shielding the cell borders and JFETs from direct irradiation with usage of a Zr mask, a spectral peak-to-valley ratio of ∼1000 was achieved.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
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IEEE Trans. Nucl. Sci. 56(2009),1666-1670.
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33rd European Solid State Circuits Conference, 2007,Munich,Germany (2007),296 - 299.
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Nucl. Instrum. Methods A 585(2008)76-82,3.
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2007 Nuclear Science Symposium and Medical Imaging Conference,Honolulu,USA (2007),.
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ABSTRACT: A pixel-level 8-bit 5-MS/s digitizer for the DSSC X-ray imager utilizing the method of Wilkinson is presented. The timing information is generated column-wise by means of an 8-bit Gray-code counter. The 625-ps time stamps are distributed to the column pixels through 13-mm long shielded coplanar waveguides. Pixel-internal blocks comprise a sample-and-hold stage with current source for ramp generation, a temperature-compensated and supply voltage-stabilized reference circuitry, a comparator, a bank of eight receivers with latches for the time stamps, and control logic. These pixel-internal and global devices in 130-nm CMOS technology occupy 0.015 and 0.012 mm2, respectively. The power consumption amounts to at 1.2-V supply voltage. Taking the 0.8-V dynamic range into account, the simulated rms-noise voltage of about corresponds to a signal-to-noise ratio above 70 dB. The differential and integral nonlinearity is expected to remain below 0.4 LSB and 1 LSB, respectively. All results promise the compliance with underlying requirements.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
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Nucl. Instrum. Methods A 589(2008),250-258.
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ABSTRACT: A new Si-drift detector module for fast X-ray spectroscopy experiments was developed and realized. The Peltier-cooled module comprises a sensor with 7×7-mm2 active area, an integrated circuit for amplification, shaping and detection, storage, and derandomized readout of signal pulses in parallel, and amplifiers for line driving. The compactness and hexagonal shape of the module with a wrench size of 16 mm allow very short distances to the specimen and multi-module arrangements. The power dissipation is 186 mW. At a shaper peaking time of 190 ns and an integration time of 450 ns an electronic rms noise of ∼11 electrons was achieved. When operated at , FWHM line widths around 260 and 460 eV (Cu-Kα) were obtained at low rates and at sum-count rates of 1.7 MHz, respectively. The peak shift is below 1% for a broad range of count rates. At 1.7-MHz sum-count rate the throughput loss amounts to 30%.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
