1,720,997 research outputs found
Design and optimization of low-noise wide-bandwidth charge preamplifiers for high purity germanium detectors
No full textDesign criteria for low-noise wide-bandwidth charge-sensitive preamplifiers for highly-segmented HPGe detectors are presented. The attention is focused on the optimization of the preamplifier noise, long-term gain stability, and bandwidth. The charge-sensitive preamplifiers of AGATA, i.e., the Advanced GAmma Tracking Array detector for next generation nuclear physics experiments, have been designed, realized and optimized using the proposed techniques. The circuit, in conjunction with the detector, provided an Equivalent Noise Charge of 101 electrons r.m.s., a rise time of similar to 8.3 ns, no appreciable line shift in long term acquisitions, a dynamic range of as much as 92 dB. An analytical study of the circuit is made. Computer simulations and experimental results are shown and critically discussed
An advanced preamplifier for highly segmented germanium detectors
Get PDFWe present a fast low-noise hybrid charge-sensitive preamplifier for germanium position-sensitive gamma-ray detectors. In conjunction with a bulky 36-fold segmented detector it provided an excellent resolution of 1.71/1.77 keV fwhm on the 1.17/1.33 MeV 60Co lines. The preamplifier rise time, as measured at the test bench, is as fast as 7.5 ns, with a detector capacitance of 21 pF and with a 5 m 50 ohm twisted-pair cable connected at its output. The dynamic range of the preamplifier input stage is as large as 92 dB, ranging from 0.275 fC to 9.9 pC, i.e., from 5 keV to 180 MeV in terms of photon energy. On signals larger than 2 MeV a fast reset (about 10 MeV/us) is enforced to reduce the system dead time. An estimate of the amplitude of such large signals is derived from the reset time, still obtaining a high resolution. Using this technique we achieved an energy resolution of 0.3% at 16.7 MeV
A versatile low-noise wide-range charge-sensitive preamplifier for HPGe detectors
No full textA fast low-noise hybrid charge-sensitive preamplifier for HPGe detectors, has been designed for the new array detector 'GALILEO' under construction at INFN Legnaro National Laboratory (Italy). The preamplifier includes an over-threshold fast-reset circuitry that greatly reduces the dead time due to preamplifier and/or ADC saturation. A 1-bit digital output signal is provided in LVDS or CMOS format, whose width yields an indirect precise measurement of the large over-threshold signals. Combining the under- and over-threshold working modes an unprecedented spectroscopic dynamic range is obtained of 10^5, from 0.1 fC to 10 pC, i.e. from ∼2 keV to 180 MeV of equivalent energy in germanium. A fast analogue signal is optionally provided as a trigger for ancillary detectors. The preamplifier is optimized to feature low noise, fast rise time and wide amplitude range when connected to anode detector electrodes. It includes a fast differential buffer for low-noise signal transmission to a remote ADC, with a preset common-mode DC component, that can be adjusted to match the ADC requirement. The rise time, as measured at the test bench, is as fast as 7.5 ns, with a detector capacitance of 23 pF and with a 5m 50ohm twisted-pair cable connecting the preamplifier to the ADC. With its input transistor working at 150K the preamplifier features an intrinsic noise of ∼90 electrons r.m.s., i.e. ∼600eV fwhm in germanium, and a noise slope of 8eV/pF
Extending the dynamic range of nuclear pulse spectrometers
Get PDFUsing an innovative time-varying front-end electronics in conjunction with a bulky coaxial high-purity germanium detector, we were able to extend the range of the radionuclide spectra well beyond the analog to digital converter (ADC) saturation point. The electronics automatically conditions the signal for digital-filtering optimization if it is in the ADC voltage range and for time-over-threshold analysis if it exceeds the ADC range. A high spectroscopic resolution has been achieved in both operation ranges. An unprecedented wide energy range from 5 keV to 150 MeV of equivalent energy, or 90 dB, has been obtained using a single acquisition chain, while maintaining a high-energy resolution in the whole spectrum. For example, with an ADC range of 3 MeV a resolution has been obtained of 1.3/2.2 keV full width at half maximum on the 122/1332 keV gamma-ray lines of Co-57 and Co-60, and of <0.4% in the time-over-threshold region, or for energy deposits beyond 3 MeV. (C) 2008 American Institute of Physics
A Time-over-Threshold technique for wide dynamic range gamma-ray spectroscopy with the AGATA detector
No full textWide-range energy measurements have been carried out with an encapsulated 36-fold segmented germanium detector of AGATA (Advanced GAmma-ray Tracking Array). An unprecedented equivalent energy range of 5 keV to 180 MeV, or similar to 90 dB, has been obtained using a single acquisition chain, while maintaining a high energy resolution in the whole spectrum. For energies larger than 3 MeV the pulse-height is obtained with a Time-over-Threshold (ToT) technique. The measured resolution in all the tested range from 3 to 50 MeV is of <0.4%. The ToT technique has been demonstrated using a Am-241 + Be source with Ni target generating high-energy gamma photons by neutron capture reactions. A remarkable resolution of 0.21% has been obtained on the Ni spectrum line at the energy of 8.998 MeV
Low noise, dual gain preamplifier with built in spectroscopic pulser for highly segmented high-purity germanium detectors
No full textWe present a fast and very low noise hybrid front-end electronic device consisting of a complex charge sensitive preamplifier with a built in fast reset circuitry and a very accurate spectroscopy pulser. The front-end electronics was developed for the central electrode of 36-fold segmented, high purity germanium detectors in the frame of AGATA array of detectors. The intrinsic energy resolution in conjunction with a highly segmented detector is less then 900 eV for central electrode with a detector capacity of ∼ 47 pF. The dynamic range of the central charge sensitive stage is as large as 100 dB, ranging from 0.1 fC to 10 pC, i.e. from ∼2 keV to 180 MeV in terms of photon energy. To achieve such an unprecedented wide dynamic range, we split the whole spectroscopic range in four sub-ranges, namely 0-5 MeV, 0-20 MeV, 5-180 MeV and 20-180MeV, respectively. The first two ranges are measured with standard pulse-high spectroscopy techniques. Thereto, the analog electronics was designed with two conversions gains, 200 mV/MeV and 50mV/ MeV, respectively to match the 1 V input dynamic range of the very fast pipe line ADC used by the digitizer units. To extend the pulse-height spectroscopy range well beyond the fast ADC analog input range, a new method was implemented and at a certain threshold we are switching from a standard pulse height analysis method to a time over threshold technique TOT. In order to achieve that, adjacently to the pole-zero cancellation circuit, a fast-reset circuit controlled by a fast comparator and an accurate zero crossing detector has been developed. Using this technique we can achieve an energy resolution of 0.04% at equivalent gamma energies of 180MeV. A programmable spectroscopic pulser has been designed and implemented in the central electrode (core) front-end electronic to achieve 'self-calibration standards' in both time and amplitude domain, which was needed to characterize such a complex, highly segmented high purity solid state detector
Ultra-fast low-noise preamplifier for bulky HPGe gamma-ray sensors
No full textWe present a fast low-noise hybrid charge-sensitive preamplifier for germanium position-sensitive gamma-ray detectors. In conjunction with a bulky 36-fold segmented detector it provided a record resolution of 1.71/1.77 keV fwhm on the 1.17/1.33 MeV 60Co lines. The preamplifier rise time, as measured at the test bench, is as fast as 7.5 ns, with a detector capacitance of 23 pF and with a 5m 50ohm twisted-pair cable connected at its output. The dynamic range of the preamplifier input stage is as large as 92 dB, ranging from 0.275 fC to 9.9 pC, i.e. from 5 keV to 180 MeV in terms of photon energy. On signals larger than 2 MeV a fast reset (~10 MeV/μs) is enforced to reduce the system dead time. An estimate of the amplitude of such large signals can be derived from the reset time, still obtaining a high resolution. Using this technique we achieved an energy resolution of 0.3% at 16.7 MeV
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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