A Mixed-Signal Spectroscopic-Grade and High-Functionality CMOS Readout Cell for Semiconductor X- Ray Pixel Detectors
ABSTRACT We present a mixed-signal CMOS front-end cell designed for semiconductor pixel detectors for X-gamma ray imaging and spectroscopy. The readout pixel cell (RPC) comprises an analog and a digital section to accomplish all the functionality of a spectroscopic-grade signal readout. The analog section includes a low noise charge preamplifier, a two stage shaper amplifier with digitally selectable shaping times from 1 mus to 10 mus, a baseline restorer, a high precision peak stretcher and an output amplifier. The digital section includes an amplitude discriminator with coarse and fine digital control of the threshold level, a peak discriminator, a current-mode trigger generator, a logic circuit to accomplish the pulse pile-up rejection and the RPC reset after the A/D conversion, the disable functions of the preamplifier and of the discriminators. The RPC has been designed and manufactured in 0.35 mum CMOS technology with a size of 300 mumtimes300 mum. The full functionality of the RPC has been successfully tested. At room temperature, the intrinsic equivalent noise charge is 15.7 electrons r.m.s. at 3.3 mus and the minimum noise slope is 22 electrons/pF at 8 mus, the linearity error is between -1.4% and +1.2% within 1.9 fC input signal dynamic. The RPC has separate voltage supplies (+3.3 V) and grounds for the analog and digital sections and the total power consumption is 495 muW.
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ABSTRACT: We propose to perform a continuously scanning all-sky survey from 200 keV to 80 MeV achieving a sensitivity which is better by a factor of 40 or more compared to the previous missions in this energy range. The Gamma-Ray Imaging, Polarimetry and Spectroscopy (GRIPS) mission addresses fundamental questions in ESA's Cosmic Vision plan. Among the major themes of the strategic plan, GRIPS has its focus on the evolving, violent Universe, exploring a unique energy window. We propose to investigate $\gamma$-ray bursts and blazars, the mechanisms behind supernova explosions, nucleosynthesis and spallation, the enigmatic origin of positrons in our Galaxy, and the nature of radiation processes and particle acceleration in extreme cosmic sources including pulsars and magnetars. The natural energy scale for these non-thermal processes is of the order of MeV. Although they can be partially and indirectly studied using other methods, only the proposed GRIPS measurements will provide direct access to their primary photons. GRIPS will be a driver for the study of transient sources in the era of neutrino and gravitational wave observatories such as IceCUBE and LISA, establishing a new type of diagnostics in relativistic and nuclear astrophysics. This will support extrapolations to investigate star formation, galaxy evolution, and black hole formation at high redshifts.Experimental Astronomy 05/2011; · 2.97 Impact Factor
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ABSTRACT: We present the design of a readout system, comprising a charge sensitive amplifier and a pulse shaper, that directly interfaces a semiconductor scintillator. The designed amplifier quantifies optical response of a large-area epitaxial photodiode that registers luminescence produced by a scintillating semiconductor wafer when excited by ionizing radiation. The epitaxial photodiode is characterized by a capacitance of 50 pF and a dark current of 10 pA. The presented optimization procedure for the biasing and sizing the input transistor of the CSA directly relates the region of operation of the input transistor with the constraints on power, area and event rate of the readout system. Experimental results of the amplifier implemented in 0.5 μm CMOS technology, verify gain of 71 mV/fC, with the measured linearity of 1.3%. For the parameters of the photodiode, the measured equivalent noise charge (ENC) is 950 electrons with the measured time constant of the pulse shaper of 90 μs and the power consumption of 210 μW. The measured slope of the ENC dependence on the input capacitance is 18 e<sup>-</sup>/pF.IEEE Transactions on Nuclear Science 09/2011; · 1.22 Impact Factor
- IEEE Transactions on Nuclear Science 10/2013; · 1.22 Impact Factor