1,355,782 research outputs found
How to derive the optimum filter in presence of arbitrary noises, time-domain constraints, and shaped input signals : a new method
No full textThe optimum filter constrained to finite width and other key features in the time domain, suitable for nuclear pulse spectrometry as well as for many other applications, is derived by means of a new method. A pattern of typical noise sources, including series and parallel Lorentzian packets, white and fn noises with n positive or negative integer are considered. Such a pattern permits also to treat the N-order fitting to an arbitrary spectral density of noise. The new method features a fast-convergence capability, and, in contrast to other methods, accepts either δ-like or arbitrarily shaped input signals. Flat tops, finite width, and/or zero-area constraints are met by a 'shift, sum and weigh' procedure, which uses as core function the non-flat-topped, non-time-limited minimum-noise weight function. This latter is determined, for all the specified input noises, in closed form. The optimum filter for the measurement of a DC signal is also provided as a by product of the method. A computer program, running in seconds in the Matlab environment, is available, and this demonstrates the effectiveness of the method
Impact of non-white noises in pulse amplitude measurements : a time-domain approach
No full textThe contribution of the 1/f-noise to the spectral line broadening in pulse amplitude measurements is derived with a time-domain analysis. The known time-domain relationships which provide the contributions of the series and parallel white noises are generalised for the case of 1/f and other typical non-white noises, by using the fractional derivative of either the system impulse response (time-invariant linear filters) or its weight function folded (time-variant linear filters). It is shown that a time-domain approach is also effective to determine the contribution of Lorentzian noises. A simple rule suitable to derive numerically the fractional derivative is given, which permits to calculate the effect of non-white noises even when the filter impulse response is not known analytically but only in sampled form. © 1998 Elsevier Science B.V. All rights reserved
The "switch off" baseline restorer for the 120 channel silicon detector system for EXAFS at NSLS
No full textA new circuit for high precision baseline restoration in multichannel nuclear pulse spectrometers is proposed. It has been designed for the 120 channel silicon detector system for EXAFS research at NSLS (National Synchrotron Light Source), Brookhaven National Laboratory, USA [L.R. Furenlid et al., Nucl. Instr. and Meth. A 319 (1992) 408], and is based on a current "switch off" mechanism self-triggered on the input signal pulses. No auxiliary gate signals are required, and, consequently, the network is particularly compact. As opposed to Robinson restorers, this restorer is not affected by undershoot, and it does not involve the significant complexity of gated solutions. The restorer has been tested with a 7 pole quasi-Gaussian filter permitting very high resolution X-ray spectroscopy (160 eV FWHM on pulser peak). The signal-to-noise degradation due to the restorer is about 7%. The BLR response to 18 μs large trapezoidal input pulses shows an undershoot which is about 0.3%. Baseline is correctly recovered for repetition rates of up to 5 × 104 trapezoidal signals/s, which corresponds to a duty cycle of 60%. The BLR has been layed out in SMT on a 0.8 in. × 0.8 in. area, which is suitable for multichannel applications where the circuit has to be largely used as the last stage of each individual unipolar shaping filter
Interfacing low-noise charge-sensitive preamplifiers to high-resolution flash ADCs
No full textA low-noise, low-power, high bandwidth circuit architecture is presented, suitable for interfacing highly segmented semiconductor detectors to high-speed high-resolution flash ADCs. The proposed circuit works as an optimized interface between the preamplifiers and the ADCs, and has many useful features, including: end termination for both differential-mode and common-mode components of the input signals, single-ended or differential-input mode, AC or DC coupling to the ADC, introduction of a preset common-mode voltage for differential ADC matching, introduction and remotely-controlled adjustment of differential DC offset for dynamic range maximization, remotely controlled range selection, test-pattern waveform multiplexed to the ADC for precise inter-channel time synchronization. The interface has been conceived for new-generation, highly-segmented, position-sensitive HPGe detectors for nuclear physics experiments, requiring digitization at 100 Ms/s 14bit or better, and is adequate for high-resolution gamma-spectroscopy and gamma-ray tracking
A low-noise preamplifier for gamma-ray sensors with add-on device for large-signal management
No full textA new charge-sensitive preamplifier for High Purity Germanium gamma-ray detectors has been built and tested. It comprises an over-load recovery device that reduces the dead time brought about by hits of energetic particles. The amplitude of the large signals is reconstructed from Time-Over-Threshold measurements performed along the reset transients. Using such a technol. an extremely wide energy range of 10 keV to 30 MeV, or 70 dB, is obtained. With a count rate of 6 kHz a resoln. of 1.1 keV fwhm is obtained on the 152Eu 122 keV line and of .apprx.5 perthousand on pulser lines in the energy range of 5-30 MeV
Resolution Limits of Silicon Detectors and Electronics for Soft X Ray Spectroscopy at non Cryogenic Temperatures
No full textThis paper deals with the limits of the resolution achievable in soft X-ray spectroscopy using silicon detectors of different dimensions (pad, pixel and drift detectors) operated at non-cryogenic temperatures. The role of the front-end electronics in achieving high resolution is examined with special care. It is found that in a common experimental setup the ultimate performance of the spectrometer is not limited by the thermal and shot white noises: the main contribution to the resolution performance arises from the non-white component of parallel noise due to the dielectric losses in the passive devices connected to the preamplifier input, especially when the detector leakage current is in the pA range. By using high quality feedback capacitors we have obtained significant improvements in the resolution performance. With a ceramic feedback capacitor and a commercial device as input transistor we have obtained' at room temperature an Equivalent Noise Charge as low as 15 electrons rms (130 eV FWHM). We discuss the ultimate limits and the perspectives for room temperature operation of silicon soft X-ray detectors
A Method for the Determination of the Noise Parameters in Preamplifying Systems for Semiconductor Radiation Detectors
No full textIn this paper a method for disentangling the various noise components in semiconductor radiation detector-amplifier systems is described and experimentally tested. A charge amplification scheme is adopted for the measurements. It is shown how an accurate estimate of the series and parallel white noise, 1/f series noise, and f parallel noise can be quickly obtained through a multiparameter least-squares interpolation of the equivalent noise charge data of the system
On the optimum area-balanced filters for nuclear spectroscopy.
No full textThe minimum noise Area-Balanced (A-B) filters for nuclear spectroscopy are disentangled in the sum of two optimized individual filters. The former is the unipolar finite cusp filter, used for pulse amplitude estimation but affected by baseline shift errors, the latter is a specific filter used for baseline estimation. Each of them is optimized so as to give the minimum noise in the estimation of the pulse amplitude or of its baseline level. It is shown that double optimisation produces an overall optimum filter exhibiting a total noise Vn2 equal to the sum of the noises Vn12 and Vn22 exhibited by each filter individually. This is a consequence of the orthogonality of the individual filter weight-functions in a function space where the norm is defined as √Vn2
Minimum-noise filter for baseline estimation in radiation detection systems.
No full textBaseline height estimation in nuclear pulse spectrometry can be optimized by using a proper weight-function. The minimum-noise function for baseline estimation in presence of series and parallel white noises, constrained to a finite duration, is theoretically derived in this paper. Baseline restoration can be subsequently performed by subtracting the minimum-noise baseline estimation to the output signal pulse. The overall signal-to-noise performance obtained using the minimum-noise baseline estimation for pulse height correction is compared to that obtained with routinely used Base Line Restorers. An improvement of up to 16% in the Equivalent Noise Charge, with respect to classic baseline restoration, can be theoretically achieved in case of a simple triangular pulse shaping. The minimum-noise baseline weight-function can be synthesized in practice by means of a digital processing unit
Optimum zero-area filter for nuclear signal sequences.
No full textA zero-area optimum filter for the processing of nuclear signal sequences is discussed in this paper. In contrast to known optimum filters (e.g. 'finite cusp' and Deighton filters), in which the weight function is entirely constrained to the finite time span available between three subsequent δ-pulses, we suggest that the filter weight function may be built along a larger packet of these time intervals. The proposed filter is basically the combination of an optimum filter for pulse-area estimation (finite cusp like) and an optimum multi-lobe filter for baseline subtraction. The left- and right-handed parts of the cusp-like filter, as each lobe of the baseline filter, are constrained to single inter-pulse time spans, but the overall filter has a time width which exceeds that between three subsequent pulses: the larger the number of lobes, the longer the overall filter duration. We show that the noise performance of the new filter tends to that of the finite-cusp filter as the number of lobes is increased: with a eight lobe weight function the signal-to-noise ratio is in typical situations 76-97% that of the finite cusp; whereas the low-frequency-disturbance rejection is by far better. The synthetized filter is to be regarded as a trade-off between the finite cusp filter (optimum signal-to-noise performance but no low-frequency-rejection capability) and the Deighton filter (excellent low-frequency rejection but relatively poor signal-to-noise performance)
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