Current-sensitive Preamplifiers Research Articles

A Method for Calculating Characteristic Value to Characterize the Induced Charge in Electrostatic Tomography

Electrostatic tomography (EST) is a technology that uses the induced charge on the electrode surface to reconstruct the parameter distribution of gas-solid two-phase flow. The induced signal is dynamic, whereas the induced charge required in the image reconstruction theory is static. Therefore, it is necessary to calculate the characteristic value of the signal to characterize the induced charge before image reconstruction. However, the calculation methods of characteristic value are different at present, and there is a lack of unified understanding. For the above problem, this article analyzes the mechanism of signal induced by the charged single particle, compares the differences between the charge-sensitive and current-sensitive preamplifiers, and comes to the conclusion that the current-sensitive preamplifier is more suitable for the measurement of induced charge. By further studying the output signal of the conditioning circuit with the current-sensitive preamplifier, root mean square of charge (RMSCE) is proposed to characterize the induced charge. Simulation and experimental results show that RMSCE has stronger characterization ability for the induced charge and can be used in EST system to obtain high-quality reconstructed images.

Design of charge-sensitive and current-sensitive preamplifiers for electrostatic sensor

In this paper, the signal shape similarity degree is defined as quantitative criteria to distinguish charge-sensitive or current-sensitive preamplifier of electrostatic sensor. To establish the relationship between the similarity degree and the preamplifier, the rate (k) of the cutoff frequency of the preamplifier to the highest frequency of the induced current signal is presented. It is found that there are monotonic relationships between the similarity degree and k, which are built and used to design charge-sensitive and current-sensitive preamplifiers with different requirements. The results of the single particle free-fall experiment verify the effectiveness of this method.

Signal formation in THGEM-like detectors

Numerical simulations were used to study signal formation in a Thick Gaseous Electron Multiplier (THGEM) and in THGEM-based Thick-WELL (THWELL) and Resistive-Plate WELL (RPWELL) detectors. The signal shapes were simulated in mixtures of Argon and Neon with 5% Methane under irradiation with soft x-rays and muons. Anode-induced raw signals were convoluted with the response functions of charge-sensitive and current-sensitive pre-amplifiers. The simulation toolkit was validated by the good agreement reached between the simulated and measured response, with different pre-amplifiers. It indicates that our simulations framework provides valid insight into the inherent complex dynamical processes of the various detectors.

Particle identification with time-of-flight and pulse-shape discrimination in neutron-transmutation-doped silicon detectors

A method for the identification of energetic charged particles has been investigated based on the employment of pulse-shape discrimination (PSD) in a silicon detector in addition to conventional time-of-flight (ToF) techniques. The method makes use of the fact that, at fixed energy, the particle's velocity, or ToF, is a measure of the particle's mass A while the time structure of the current pulse in a silicon energy detector, used as the ToF stop, permits identification of nuclear charges Z. In the measurements presented here, ToF and PSD methods were applied simultaneously. We used micro-channel plate (MCP) detectors as fast time pick-offs and surface-barrier (SB) n-type Si detectors made from homogeneously neutron-transmutation-doped (n-TD) silicon. As the particles, products from the reactions of a 400 MeV 20Ne beam impinging on 12C, 27Al and 208Pb targets were employed. With using fast current-sensitive pre-amplifiers for the 250 and 800 μ m SB detectors a major progress in particle identification with respect to both, mass A and charge Z was achieved. In addition, using a stack of two closely mounted n-TD SB detectors, a timing measurement between the two detectors permitted to study PSD in the rear detector with the time trigger derived from the foremost one. Finally, the internal PSD method was implemented which determines pulse rise-time in single detectors from analyzing differentiated preamplifier timing signals.

Charge and current-sensitive preamplifiers for pulse shape discrimination techniques with silicon detectors

New charge- and current-sensitive preamplifiers coupled to silicon detectors and devoted to studies in nuclear structure and dynamics have been developed and tested. For the first time shapes of current pulses from light charged particles and carbon ions are presented. Capabilities for pulse shape discrimination techniques are demonstrated.

Simple charge division readouts for imaging scintillator arrays using a multi-channel PMT

Three simple charge division circuits were assembled and tested as 2-D position encoding readouts for multi-channel photomultiplier tubes (MC-PMT). They were evaluated with an 8/spl times/8 array of individual scintillators (2/spl times/2/spl times/10 mm BGO) coupled to a 64 channel MC-PMT (Philips XP1722) via 25 cm long, 2 mm diameter, double clad, optical fibers (Kuraray). This type of gamma-ray imaging detector has many potential applications in medical and industrial imaging. Though independent channel readout would allow for the discrimination of scatter within the array, and higher count rates, it would also require an excessive amount of supporting electronics. This is especially true for systems comprised of many MC-PMTs. In this study, the number of channels being read out was reduced from 64 to 4 using three different simple resistor networks. These circuits take advantage of the discretized nature of the scintillator array, the low interchannel crosstalk of the MC-PMT and low input impedance current-sensitive preamplifiers. For each circuit, the scintillator identification accuracy was compared. The identification accuracy as a function of deposited energy was also determined by exposure to various gamma-ray emitters. It was found that the preamplifier circuit noise contributed the most to the degradation of the detector's spatial response so several low noise op amps were evaluated. It was also determined that keeping the preamplifier input impedance small was necessary for accurate positioning. The coincidence timing resolution of the detector (15 ns) is only slightly degraded by the readout circuit.

Monolithic cryogenic preamplifiers based on large gate-area GaAs MESFETs

Monolithic preamplifiers using large gate-area Gallium-Arsenide Metal-Semiconductor Field-Effect Transistors (GaAs MESFETs) at the input have been designed and fabricated using an ion-implanted GaAs process. Large gate-area is necessary to obtain low series noise. A differential voltage-sensitive preamplifier has at the input two MESFETs with a gate width W=6000 /spl mu/m, it is fully DC coupled, has a large common-mode rejection ratio (CMRR) and dissipates low power at 4 K. Dual current-sensitive preamplifiers using at the input MESFETs with W=24000 /spl mu/m, designed for the readout of noble liquid calorimeters, have been integrated in a single chip. Recent tests with a LAr calorimeter prototype demonstrated strong noise reduction compared to previous state-of-the-art hybrid readout circuits. Radiation damage tests have been performed at cold on the current-sensitive preamplifier chips. >

Monolithic current-sensitive preamplifier for the Accordion LAr calorimeter

Monolithic current-sensitive preamplifiers matching large detector capacitances, suitable for the Accordion LAr calorimeter prototype, have been designed and fabricated in an ion-implanted GaAs MESFET process. After pulse shaping with an CR-RC2 filter, the equivalent noise charge is at least a factor of 2 lower than the value reached so far with existing hybrids circuits, without increasing the power dissipation. This preamplifier has a fast response and large dynamic range. Results show that it is still possible to further reduce the noise and extend the dynamic range; this is likely to be obtained in a new version presently being developed.

Light-particle detection with plastic scintillators coupled to a photodiode readout system

The response to alpha particles (between 13 and 20 MeV) and protons (between 3 and 12 MeV) of a large area photodiode coupled to plastic scintillators was measured with both charge- and current-sensitive preamplifiers. The results for the measurements with the charge-sensitive preamplifier are compared with data on other scintillators coupled to photodiode readout systems. These measurements were part of a study in which the possibility of constructing a light-particle detector consisting of a plastic phoswich scintillator and a photodiode was investigated.

Neutron ionization chambers

One of the first particles on neutron detectors bears the title: Ionization of gases by neutrons 1). Neutrons are neutral, a fact that the author was aware of. Still, he, as well as others 2) in their first attempt to investigate neutrons, chose to take the full step from a neutron to the output signal. They did indeed record a signal and proved that a measurement device could be made: a current caused by neutrons flowed through the chamber. Several years elapsed before the ion chamber was explored as a neutron detector. Much more information about the neutron was gained from another device, the cloud chamber, which became popular at the expense of the development of the ion chamber. Any radiation detector may be used as a neutron detector if it contains or can be complemented by a material giving a conversion process, which transfers the information of interest to a charged particle. The recoil nucleus in a neutron scattering, the reaction products in a nuclear reaction, or the fission fragments in a nuclear fission may be used for the detection of the primary neutron. The devices used as detectors were often tubes. They were given the name “radiation counter tubes”, abbreviated as “counters’, which for neutron detection gave the combination “neutron counters”. A more general term is “neutron chambers”. The neutron chamber might be a neutron counter or a neutron spectrometer. Pure neutron counters to be described here are the boron-lined neutron chamber, the boron-trifluoride chamber and the fission chamber. Proton-recoil chambers and helium-3 chambers can be used as counters or spectrometers. Teh slowing-down neutron detectors are systems which include one of the above chamber types. By chamber we mean here a detector using a gas for the next step in the detection chain, the detection of the charged particles. The ion-chamber, proportionality, corona-discharge and Geiger-Müller range have all been used for neutron sensitive chambers. Ion-chambers are used both in pulse counting systems and in current measuring systems. The electron-ion pair clouds created in the chamber are in pulse detection systems sensed by voltage, charge or current sensitive preamplifiers. The current-pulse detection method has recently been popular for fission chambers because of their high signal-to-noise ratio and short pulse length. They are often referred to in the literature as current detectors, but should not be confused with the chamber systems which use the mean current as the information carrier.

Semiconductor radiation detectors used with current-sensitive preamplifiers

The utilization of short current pulses given by L- and U-type semiconductor radiation detectors was investigated. The maximum amplitude and minimum length of the current pulses from silicon detectors were calculated and plotted against resistivity for L detectors and voltage for U detectors respectively. By using a low input impedance, fast transistor current-sensitive preamplifier, L-detector exponential current waveforms (for 4 MeV protons, 5–15 MeV alpha particles and fission fragments) were verified. The possibility to employ current pulses for heavy charged particle spectrometry and to obtain simultaneously fast and slow pulses from the same detector were also checked experimentally.