MHz Count Rate Research Articles

In-beam test results of the Super-FRS GEM-TPC detector prototype with relativistic uranium ion beam

As an essential part of the Super-FRS particle identification, the GEM-TPC detector in a twin field-cage configuration will provide position information at up to 1 MHz counting rate with a spatial resolution < 1 mm and with tracking efficiency >95 %. This detector is designed to provide particle-beam tracking information of projectiles ranging from protons to uranium. The performance of the GEM-TPC detector in a single field-cage configuration and newly integrated AWAGS readout electronics with a differential output was studied at the FRS for the response to the uranium beam at 850 MeV/u with intensity up to 1000 ions/spill. The result shows that a clusterization algorithm developed for this analysis works properly. The spatial resolution of 0.74–0.81 mm, a detection efficiency >99 %, and a tracking efficiency >96 % were found. This work describes the methodology used to achieve such results in detail.

High rate neutron and gamma ray spectroscopy of magnetic confinement fusion plasmas

An important instrumental development work has been done in the last two decades in the field of neutron and gamma ray spectroscopic measurements of magnetic confinement plasmas. Starting from the present state of the art instrumentation installed at JET, this paper reviews the recent development that has been carried out within the EUROFUSION programme for the forthcoming high power JET D and DT campaign. This development was dedicated to the realization of new compact neutron and gamma-ray spectrometers which combine very high energy resolution (typically better than 5%) and MHz counting rate capabilities allowing for time resolution in the 10 ms time scale. One of the advantages offered by the compact dimensions of these spectrometers is to make possible their use in multiple sight-line camera configurations, such as for future burning plasma reactors (ITER and DEMO). New compact neutron spectrometers based on single crystal diamond detectors have been developed and installed at JET for measurements of the 14 MeV neutron spectrum. Measurements on a portable DT neutron generator have shown that neutron spectroscopy of the accelerated beam ions at unprecedented energy resolution (∼1% at 14 MeV) is possible, which opens up new opportunities for diagnosing DT plasmas. For what concerns gamma ray measurements, the JET gamma ray camera has been recently upgraded with new compact spectrometers based on a LaBr3 scintillator coupled to Silicon Photomultiplier with the dual aim to improve the spectroscopic and rate capabilities of the detectors. The upgrade camera system will reconstruct the spatial gamma ray emissivity from the plasma in the MeV energy range at MHz counting rates and energy resolution in the 2–4% range. This will allow physics studies of gamma rays produced by the interaction of fast ions with impurities in the plasma and bremsstrahlung emission from runaway electrons.

The large helical device vertical neutron camera operating in the MHz counting rate range.

In the currently performed neutral beam (NB) -heated deuterium plasma experiments, neutrons are mainly produced by a beam-plasma reaction. Therefore, time-resolved measurement of the neutron emission profile can enhance the understanding of the classical and/or anomalous transport of beam ions. To measure radial neutron emission profiles as a function of time, the vertical neutron camera (VNC) capable of operation with a counting rate in the MHz range was newly installed on the Large Helical Device (LHD). This is the world's first neutron camera for stellarator/heliotron devices. The VNC consists of a multichannel collimator, eleven fast-neutron detectors, and the digital-signal-processing-based data acquisition system (DAQ). The multichannel collimator having little cross talk was made from hematite-doped heavy concrete, which has a high shielding performance against both neutrons and gamma-rays. A stilbene crystal coupled with a photomultiplier having high-gain-stability in the high-count rate regime was utilized as a fast-neutron scintillation detector because it has a high neutron-gamma discrimination capability at high count rates. The DAQ system equipped with a field programmable logic controller was developed to obtain the waveform acquired with a 1 GHz sampling rate and the shaping parameter of each pulse simultaneously at up to 106 cps (counts per second). Neutron emission profiles were successfully obtained in the first deuterium campaign of LHD in 2017. The neutron emission profile was measured in tangentially co-injected NB-heated plasma with different magnetic axes (R ax). The neutron counts became larger in the inward-shifted configuration, which was consistent with the total neutron rate measured by the neutron flux monitor. The radial peak position of the line-integrated neutron profile which changed according to R ax showed that the VNC worked successfully as designed. The VNC demonstrated the expected performance conducive to extending energetic-particle physics studies in LHD.

Design of gamma-ray spectrometers optimized for fast particle studies at ITER.

A set of gamma ray spectrometers has been designed for ITER within the Radial Gamma Ray Spectrometer (RGRS) project. The aim of this project is designing a system, integrated with the ITER radial neutron camera, which is able to measure the gamma-rays emitted from the plasma with a good energy resolution (about 1.5% at 4.44 MeV) and at high counting rates (in excess of 1 MHz). The RGRS will be able to operate both in the D phase and in the full-power DT phase and will measure gamma rays from (i) reactions between fast ions, such as α particles, and light impurities and (ii) bremsstrahlung emission generated by runaway electron interactions with both plasma bulk and tokamak walls. The RGRS detectors are arranged in nine lines of sights (able to cover a radial region with r < a/3), each featuring a large LaBr3 scintillator crystal. Due to the high neutron flux and magnetic field, several solutions have been adopted to guarantee a good signal to background ratio and MHz counting rate capabilities. The RGRS is capable to combine space and energy distribution measurements of α particles and runaway electrons, which will help the study of the fast particle physics in a burning plasma.

Note: Fully integrated active quenching circuit achieving 100 MHz count rate with custom technology single photon avalanche diodes.

The minimization of Single Photon Avalanche Diodes (SPADs) dead time is a key factor to speed up photon counting and timing measurements. We present a fully integrated Active Quenching Circuit (AQC) able to provide a count rate as high as 100 MHz with custom technology SPAD detectors. The AQC can also operate the new red enhanced SPAD and provide the timing information with a timing jitter Full Width at Half Maximum (FWHM) as low as 160 ps.

Gamma-ray spectroscopy at MHz counting rates with a compact LaBr3 detector and silicon photomultipliers for fusion plasma applications.

Gamma-ray spectroscopy measurements at MHz counting rates have been carried out, for the first time, with a compact spectrometer based on a LaBr3 scintillator and silicon photomultipliers. The instrument, which is also insensitive to magnetic fields, has been developed in view of the upgrade of the gamma-ray camera diagnostic for α particle measurements in deuterium-tritium plasmas of the Joint European Torus. Spectra were measured up to 2.9 MHz with a projected energy resolution of 3%-4% in the 3-5 MeV range, of interest for fast ion physics studies in fusion plasmas. The results reported here pave the way to first time measurements of the confined α particle profile in high power plasmas of the next deuterium-tritium campaign at the Joint European Torus.

High Resolution Gamma Ray Spectroscopy at MHz Counting Rates With LaBr&lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$_{3}$&lt;/tex&gt; &lt;/formula&gt; Scintillators for Fusion Plasma Applications

High resolution γ-ray spectroscopy measurements at MHz counting rates were carried out at nuclear accelerators, combining a LaBr 3(Ce) detector with dedicated hardware and software solutions based on digitization and off-line analysis. Spectra were measured at counting rates up to 4 MHz, with little or no degradation of the energy resolution, adopting a pile up rejection algorithm. The reported results represent a step forward towards the final goal of high resolution γ-ray spectroscopy measurements on a burning plasma device.

Very fast front end ASIC associated with multi-anode PMTs for a scintillating-fibre beam hodoscope

For developing a scintillating-fibre beam monitor, wehave designed a front-end 16-Channel readout chip (version 2) to beassociated with Multi-anode photomultipliers Ma-PMTs (Hamamatsu H8500) in a0.35 μm BiCMOS process. Each channel of the ASIC consists of one inputcurrent conveyor driving separately a current comparator for signal eventdetection and a charge-sensitive amplifier (CSA) for signal chargemeasurement. The ASIC has brought significant improvements compared to itsprevious version: larger input dynamic range (53 dB against 33 dB), lowerpower consumption (11 mW/channel instead of 22 mW/channel under a 3.3-Vsupply), lower noise (4 fC versus 19 fC in Equivalent input Noise Charge, orENC) and a better phase margin for optimizing stability and speed. Thisdedicated chip had been used in a beam test at HIT (Heidelberg Ion-BeamTherapy Center). System testing has shown achievements of 1 mm spatialresolution (size of the scintillating fibers) and a 4 MHz count rate. Themain limitation comes from the Ma-PMTs which saturates at such a frequency.The ASIC operates normally with satisfied performances.

An integrated readout circuit for personal dosimetry with phase-shift compensation technique to improve stability

In this paper an integrated CMOS readout circuit for a radiation detector in a personal dosimeter is presented. High counting rate and low power requirements make the stability of the conventional high-pass pulse shaper a big problem. A novel phase-shift compensation method is proposed to improve the phase margin. The principle of the compensation circuit and its influence on noise performance are analyzed theoretically. A readout chip with two channels of conventional structure and one channel of the proposed structure has been implemented in a 0.35μm CMOS technology. It occupies an area of 2.113×0.81mm2. Measurement results show that the proposed channel can process up to 1MHz counting rate and provide a conversion gain of about 170mV/fC at a power dissipation of 330μW with a 3.3V power supply. Ac-coupled to a silicon PIN detector, it successfully detects β-rays.

Ultrathin NbN film superconducting single-photon detector array

We report on the fabrication process of the 2 × 2 superconducting single-photon detector (SSPD) array. The SSPD array is made from ultrathin NbN film and is operated at liquid helium temperatures. Each detector is a nanowire-based structure patterned by electron beam lithography process. The advances in fabrication technology allowed us to produce highly uniform strips and preserve superconducting properties of the unpatterned film. SSPD exhibit up to 30% quantum efficiency in near infrared and up to 1% at 5-μm wavelength. Due to 120 MHz counting rate and 18 ps jitter, the time-domain multiplexing read-out is proposed for large scale SSPD arrays. Single-pixel SSPD has already found a practical application in non-invasive testing of semiconductor very-large scale integrated circuits. The SSPD significantly outperformed traditional single-photon counting avalanche diodes.

Development of a High Resolution X-Ray Imaging Crystal Spectrometer for Measurement of Ion-Temperature and Rotation-Velocity Profiles in Fusion Energy Research Plasmas

A new imaging high resolution x-ray crystal spectrometer (XCS) has been developed to measure continuous profiles of ion temperature and rotation velocity in fusion plasmas. Following proof-of-principle tests on the Alcator C-Mod tokamak and the NSTX spherical tokamak, and successful testing of a new silicon, pixilated detector with 1 MHz count rate capability per pixel, an imaging XCS is being designed to measure full profiles of Ti and vφ on C-Mod. The imaging XCS design has also been adopted for ITER. Ion-temperature uncertainty and minimum measurable rotation velocity are calculated for the C-Mod spectrometer. The affects of x-ray and uclear-radiation background on the measurement uncertainties are calculated to predict performance on ITER.

Cryogenic thermoelectric (QVD) detectors: Emerging technique for fast single-photon counting and non-dispersive energy characterization

”QVD”detectors are based on thermoelectric heat-to-voltage (Q V) conversion and digital (V D) readout. We have devised and analyzed the performance of QVD detectors with several different sensor designs that enable use of high thermoelectric figure of merit samples, be they of thin film, bulk crystal, or whisker form. Our first QVD devices had the well-studied material Au-Fe as thin film sensors. More recently, we have confirmed the literature reports of substantially higher Seebeck coefficient at cryogenic temperatures in lanthanum (cerium) hexaborides. We have also investigated the kinetic properties of La(Ce)B6 crystals with different La – Ce ratios. Currently we are exploring prototype devices based on bulk single-crystalline sensors. These include a successfully tested candidate with a sharpend hexaboride sensor and small-size bismuth absorber – a whisker prototype. In theory, QVD sensors are competitive with superconducting tunnel junction (STJ) and transition edge sensor (TES) devices in energy resolution ability. However, QVD sensors ought to be able to respond at very much faster rates than these competitors; the lanthanum-cerium hexaboride sensors are expected to reach rates of 100 MHz counting rates for UV/optical photons. In addition to traditional astrophysical applications, these detectors can be applied to the tasks of quantum computing and communication.

Toward ultimate performance limits of thermoelectric (QVD) detectors

‘QVD’ detectors are based on thermoelectric heat-to-voltage (Q→V) conversion and digital (V→D) readout. In theory, they are competitive with superconducting tunnel junction detectors and transition edge sensor devices. We analyze the performance of the QVD detectors with different design architectures. It is concluded that the detectors with lanthanum–cerium hexaboride sensors can be very fast: up to 100MHz counting rates for UV photons. In addition to traditional astrophysical applications, these detectors can be applied to the tasks of quantum computing and communication.

The development of a fast imaging electron detector based on the CODACON concept

A fast imaging electron detector is being developed as part of the Toroidal Energy- and Angle-Resolved Electron Spectrometer (TEARES), a high-resolution electron spectrometer for use on synchrotron sources. The analysed solid angle of TEARES is about 100 times greater than that of a conventional hemispherical analyser of similar radius and entrance slit sizes. A ‘typical’ solid sample at a third-generation synchrotron source would yield count rates in excess of 1 GHz, >10 3 times the capability of available imaging electron detectors. We describe a prototype detector based on low-resistance microchannel plates and an adaptation of the cartesian two-dimensional CODACON encoder that aims to achieve a relatively modest 2 MHz counting rate with 32 by 128 simultaneous energy and angle channels. The encoder pattern has been optimised for the output electron distribution of TEARES and directly generates a binary address for each event using simple electronics and the minimum number of signal channels.

Characterisation of a single photon counting pixel detector

The Large Area Detector is a photon counting detector based on pixel readout ASICs with 64×64 arrays of 150 μm square pixels bump bonded to a 300 μm thick Si detector. It is designed for X-ray diffraction studies and is capable of up to 1 MHz count rate per pixel. A prototype has been tested at the synchrotron radiation source in Daresbury in a 19.5 keV X-ray beam. This paper focuses on the spatial resolution and noise performance. The calculation of modulation transfer functions leads to analytical formulae allowing the determination of the theoretical spatial resolution.

Photon counting hybrid pixel detector for X-ray imaging

We have designed and built prototype modules of a large area photon counting hybrid pixel detector. The detector consists of modules each with seven Aladin readout chips solder bump bonded to a silicon pixel detector. Each Aladin chip has 64×64 pixels together with logic to readout the whole array in 400 μs. It is intended to tile an area of 2000×2000 pixels, each of 150 μm×150 μm and capable of up to 1 MHz count rate per pixel. This paper describes the design and operation of the detector and the performance of the existing modules. The measurements demonstrate that the detector can image 19 keV photons at 200 kHz photons per pixel with 3 keV FWHM noise. The detector is intended for X-ray diffraction studies with data capture speeds up to 1000 images per second, independent of the image size.

A Unique Radiation Detection Concept for a Miniature Particle Spectrometer

A three-channel particle spectrometer employing charge multiplying semiconductor detectors and tunnel diode discriminators has been constructed, environmentally tested and calibrated to detect low energy protons. The three channels have been calibrated to detect protons > 0.5 MeV, >1.5 MeV, and >45 MeV. The instrument is five orders of magnitude more sensitive to protons than to electrons above 500 KeV which ensures successful operation in the midst of electrons injected into the earth's radiation belt from the starfish experiment. The unique features of this instrument are: (1) Discriminates uniquely against a low energy photon background. (2) Electrical noise immunity due to the integration of the detector to the discriminator to give a high signal level output to the binary counter. (3) Thermally generated noise does not compete with the detected signal at the discriminator. The miniature instrument is a result of simple detection circuitry and the use of microelectronic elements in the data compressor. The data compressor consists of three binary counters having a storage capability of 218-1 bits. Each counter has a thin film network to octally encode the binary counts into an analog voltage. The counters have a 1 MHz count rate. This paper describes the instrument design and its characteristics which reflect the design constraints of the flight vehicle. The calibration of the instrument for a small half-angle cone of low energy protons from a Van De Graaff accelerator is discussed.