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We have developed a new scintillator-based optical soft x-ray (OSXR) diagnostic system for KSTAR. By utilizing fiber optic faceplates, mm-size lens arrays, and fiber bundles, we have successfully constructed a novel optical system for scintillator-based soft x-ray detection to overcome the limited vacuum-port conditions in KSTAR. P47 (Y2SiO5), which has a fast rise (∼7 ns) and decay (∼100 ns) time sufficient for detecting plasma instabilities observed in the kHz–MHz spectral range, was selected as the scintillator material for the KSTAR OSXR system. Scintillation toward each detection channel is collected by the lens arrays coupled to optical fiber cores, which are connected to the photodetector system. Initial results obtained during the 2022 KSTAR experimental campaign support the validity of the OSXR data through the consistency of OSXR measurement results with other diagnostics. We also observe that the OSXR system can capture magnetohydrodynamic activities, such as sawtooth oscillations, and provide valuable information for disruption mitigation studies using shattered pellet injection. [ABSTRACT FROM AUTHOR]

A new broad-energy, high-resolution gamma ray spectrometer (GRS) with Compton suppression function has been developed recently in the HL-2A tokamak to obtain the gamma ray information in the energy range of 0.1–10 MeV. This is the first time to develop an anti-Compton GRS for a magnetic confinement fusion device. The anticoincidence detector consists of a large-volume high purity germanium (HPGe) crystal (Φ63 × 63 mm2) as the primary detector and eight trapezoidal bismuth germinate (BGO) scintillators (trapezoid crystal with 30 mm thickness) as the secondary detector. The anti-coincidence data processing is implemented by a digital-based data acquisition system with fast digitization and software signal processing technology. Using radioisotope gamma ray sources and Monte Carlo N-Particle code, the energy and efficiency of the spectrometer have been calibrated and quantitatively tested. The Compton continuum suppression factor reaches 4.2, and the energy resolution (Full Width at Half Maximum) of the 1.332 MeV full energy peak for 60Co is 2.1 keV. Measurements of gamma ray spectra with Compton suppression using the spectrometer have been successfully performed during HL-2A discharges with different conditions. The performance of the spectrometer and the first experimental results are presented in this paper. [ABSTRACT FROM AUTHOR]

Dedicated nuclear diagnostics have been designed, developed, and built within EUROFUSION enhancement programs in the last ten years for installation at the Joint European Torus and capable of operation in high power Deuterium–Tritium (DT) plasmas. The recent DT Experiment campaign, called DTE2, has been successfully carried out in the second half of 2021 and provides a unique opportunity to evaluate the performance of the new nuclear diagnostics and for an understanding of their behavior in the record high 14 MeV neutron yields (up to 4.7 × 1018 n/s) and total number of neutrons (up to 2 × 1019 n) achieved on a tokamak. In this work, we will focus on the 14 MeV high resolution neutron spectrometers based on artificial diamonds which, for the first time, have extensively been used to measure 14 MeV DT neutron spectra with unprecedented energy resolution (Full Width at Half Maximum of ≈1% at 14 MeV). The work will describe their long-term stability and operation over the DTE2 campaign as well as their performance as neutron spectrometers in terms of achieved energy resolution and high rate capability. This important experience will be used to outline the concept of a spectroscopic neutron camera for the SPARC tokamak. The proposed neutron camera will be the first one to feature the dual capability to measure (i) the 2.5 and 14 MeV neutron emissivity profile via the conventional neutron detectors based on liquid or plastics scintillators and (ii) the 14 MeV neutron spectral emission via the use of high-resolution diamond-based spectrometers. The new opportunities opened by the spectroscopic neutron camera to measure plasma parameters will be discussed. [ABSTRACT FROM AUTHOR]

A hard x-ray spectrometer based on a φ25 × 25 mm2 LaBr3 scintillator has been developed to measure the runaway electron bremsstrahlung. Simulation results by GEANT4 show that x rays with an energy of 15 MeV can be effectively detected. In order to tolerate a high count rate, a self-made fast shaping amplifier is used to process the detector output into a fast bipolar pulse. The tested energy resolution, which was 3.4% for Cs-137 662 keV gamma rays, shows that the shaping amplifier does not significantly degrade the energy resolution. The results of the HL-2A discharge show that the maximum count rate can reach 2 MHz, and the time resolution of the spectrometer can reach the millisecond level. [ABSTRACT FROM AUTHOR]

Scintillators, which are more tolerant of neutrons or γ-rays than semiconductors, are a promising candidate for soft X-ray (SX) diagnostics in high neutron flux environments such as JT-60SA or ITER. Although scintillators are tolerant of radiations, neutrons and γ-rays can cause scintillation light and become noise on SX signals. Therefore, a method to estimate the temporal effect by the radiations on SX signals and an appropriate design of the radiation shield based on the estimation are required. In previous studies, it has been proposed for estimating the effect by the radiations to calculate the absorption powers due to SXs, neutrons, and γ-rays in scintillators assuming that amplitudes of scintillation light are proportional to the absorption powers. In this study, an experimental examination of this proposal is conducted in the Experimental Advanced Superconducting Tokamak (EAST). It is shown that the proposal may be valid in the examination of EAST. In addition to results in EAST, initial results of a multi-channel scintillator-based SX diagnostic in the Large Helical Device (LHD) are introduced. Although a scintillator-based SX diagnostic in LHD observes oscillations of SXs by magnetohydrodynamic (MHD) phenomena successfully, the observed temporal effect on SX signals by neutrons or γ-rays is more significant than the expected effect, which is estimated by calculating the absorption powers. One of the possible reasons for the contradiction between the results in EAST and LHD is unexpected γ-rays around the scintillators in LHD. Although the temporal effect by the radiations is significant in the current system of LHD, the degradation of amplitudes of SX signals after the deuterium plasma experiments is not observed with the current level of the fluence. The scintillator-based SX diagnostic in LHD may work as a diagnostic to research MHD instabilities in deuterium plasma experiments without additional maintenance during an experimental campaign by making the pinhole larger or setting an additional radiation shield. [ABSTRACT FROM AUTHOR]

A new time-of-flight neutron spectrometer TOFED has been constructed for installation at Experimental Advanced Superconducting Tokamak. A data acquisition system combining measurements of flight time and energy from the interaction of neutrons with the TOFED scintillators has been developed. The data acquisition system can provide a digitizing resolution better than 1.5% (to be compared with the >10% resolution of the recoil particle energy in the plastic scintillators) and a time resolution <1 ns. At the same time, it is compatible with high count rate event recording, which is an essential feature to investigate phenomena occurring on time scales faster than the slowing down time (≈100 ms) of the beam ions in the plasma. Implications of these results on the TOFED capability to resolve fast ion signatures in the neutron spectrum from EAST plasmas are discussed. [ABSTRACT FROM AUTHOR]

A new scintillator-based fast ion loss detector (FILD) has been installed on Experimental Advanced Superconducting Tokamak (EAST) to investigate the fast ion loss behavior in high performance plasma with neutral beam injection (NBI) and ion cyclotron resonance heating (ICRH). A two dimensional 40 mm × 40 mm scintillator-coated (ZnS:Ag) stainless plate is mounted in the front of the detector, capturing the escaping fast ions. Photons from the scintillator plate are imaged with a Phantom V2010 CCD camera. The lost fast ions can be measured with the pitch angle from 60◦ to 120◦ and the gyroradius from 10 mm to 180 mm. This paper will describe the details of FILD diagnostic on EAST and describe preliminary measurements during NBI and ICRH heating. Published by AIP Publishing. [ABSTRACT FROM AUTHOR]

Gamma ray diagnostics has been developed in the EAST tokamak recently. Six BGO scintillator detectors are arranged on the down-half cross-section and pointed at the up-half cross-section of plasma, with space resolution about 15 cm and energy range from 0.3 MeV to 6 MeV. Three main gamma ray peaks in the energy spectra have been observed and are identified as the results of nuclear reactions 207Pb(n,n')207mPb, H(n,γ)D, and D(p,γ)3He, respectively. Upgrading of the system is in progress by using LaBr3(Ce) scintillator, fast photo-multiplier tubes, and a fully digital data acquisition system based on high sample frequency digitizers with digital pulse processing algorithms. [ABSTRACT FROM AUTHOR]

A new scintillator-based lost fast-ion probe (SLIP) has been developed and operated in the HL-2A tokamak [L. W. Yan, X. R. Duan, X. T. Ding, J. Q. Dong, Q. W. Yang, Yi Liu, X. L. Zou, D. Q. Liu, W. M. Xuan, L. Y. Chen, J. Rao, X. M. Song, Y. Huang, W. C. Mao, Q. M. Wang, Q. Li, Z. Cao, B. Li, J. Y. Cao, G. J. Lei, J. H. Zhang, X. D. Li, W. Chen, J. Chen, C. H. Cui, Z. Y. Cui, Z. C. Deng, Y. B. Dong, B. B. Feng, Q. D. Gao, X. Y. Han, W. Y. Hong, M. Huang, X. Q. Ji, Z. H. Kang, D. F. Kong, T. Lan, G. S. Li, H. J. Li, Qing Li, W. Li, Y. G. Li, A. D. Liu, Z. T. Liu, C. W. Luo, X. H. Mao, Y. D. Pan, J. F. Peng, Z. B. Shi, S. D. Song, X. Y. Song, H. J. Sun, A. K. Wang, M. X. Wang, Y. Q. Wang, W W. Xiao, Y. F. Xie, L. H. Yao, D. L. Yu, B. S. Yuan, K. J. Zhao, G. W Zhong, J. Zhou, J. C. Yan, C. X. Yu, C. H. Pan, Y. Liu, and the HL-2A Team, Nucl. Fusion 51, 094016 (2011) to measure the losses of neutral beam ions. The design of the probe is based on the concept of the α-particle detectors on Tokamak Fusion Test Reactor (TFTR) using scintillator plates. The probe is capable of traveling across an equatorial plane port and sweeping the aperture angle rotationally with respect to the axis of the probe shaft by two step motors, in order to optimize the radial position and the collimator angle. The energy and the pitch angle of the lost fast ions can be simultaneously measured if the two-dimensional image of scintillation light intensity due to the impact of the lost fast ions is detected. Measurements of the fast-ion losses using the probe have been performed during HL-2A neutral beam injection discharges. The clear experimental evidence of enhanced losses of beam ions during disruptions has been obtained by means of the SLIP system. A detailed description of the probe system and the first experimental results are reported. [ABSTRACT FROM AUTHOR]

We present details of a new bismuth germanate [Bi4Ge3O12 (BGO)] scintillator array used to diagnose the transport and energy behavior of runaway electrons (REs) in DIII-D. BGO exhibits important properties for these compact detectors including high light yield which sufficiently excites photodiode detectors (8500 photons/MeV), high density and atomic numbers of constituent materials which maximizes sensitivity, and relative neutron blindness which minimizes complications in data interpretation. The detectors observe primarily hard x-ray radiation emitted in a forward beamed pattern by RE when they strike first wall materials or bulk ions and neutrals in the plasma, although we also address photoneutron signals. The arrangement of the array enables time resolved location of x-ray emission and associated asymmetries which help identify instabilities and confinement properties of RE. By shielding a subset of detectors with different thicknesses of lead, and with interpretative support of the code EGSNRC, we also measure RE energy, although due to the often distributed nature of RE strike points and the forward beamed character of emitted hard x-rays, we restrict interpretation as a lower bound for RE energy. [ABSTRACT FROM AUTHOR]

Notwithstanding the advances of the past decades, significant developments are still needed to satisfactorily diagnose 'burning plasmas.' D-T plasmas indeed require a series of additional measurements for the optimization and control of the configuration: the 14 MeV neutrons, the isotopic composition of the main plasma, the helium ash, and the redistribution and losses of the alpha particles. Moreover a burning plasma environment is in general much more hostile for diagnostics than purely deuterium plasmas. Therefore, in addition to the development and refinement of new measuring techniques, technological advances are also indispensable for the proper characterization of the next generation of devices. On JET an integrated program of diagnostic developments, for JET future and in preparation for ITER, has been pursued and many new results are now available. In the field of neutron detection, the neutron spectra are now routinely measured in the energy range of 1-18 MeV by a time of flight spectrometer and they have allowed studying the effects of rf heating on the fast ions. A new analysis method for the interpretation of the neutron cameras measurements has been refined and applied to the data of the last trace tritium campaign (TTE). With regard to technological upgrades, chemical vapor deposition diamond detectors have been qualified both as neutron counters and as neutron spectrometers, with a potential energy resolution of about one percent. The in situ calibration of the neutron diagnostics, in preparation for the operation with the ITER-like wall, is also promoting important technological developments. With regard to the fast particles, for the first time the temperature of the fast particle tails has been obtained with a new high purity Germanium detector measuring the gamma emission spectrum from the plasma. The effects of toroidal Alfven eigenmodes modes and various MHD instabilities on the confinement of the fast particles have been determined with a combination of gamma ray cameras, neutral particle analyzers, scintillator probe, and Faraday cups. From a more technological perspective, various neutron filters have been tested to allow measurement of the gamma ray emission also at high level of neutron yield. [ABSTRACT FROM AUTHOR]

A scintillator based detector for fast-ion losses has been designed and installed on the ASDEX upgrade (AUG) tokamak [A. Herrmann and O. Gruber, Fusion Sci. Technol. 44, 569 (2003)]. The detector resolves in time the energy and pitch angle of fast-ion losses induced by magnetohydrodynamics (MHD) fluctuations. The use of a novel scintillator material with a very short decay time and high quantum efficiency allows to identify the MHD fluctuations responsible for the ion losses through Fourier analysis. A Faraday cup (secondary scintillator plate) has been embedded behind the scintillator plate for an absolute calibration of the detector. The detector is mounted on a manipulator to vary its radial position with respect to the plasma. A thermocouple on the inner side of the graphite protection enables the safety search for the most adequate radial position. To align the scintillator light pattern with the light detectors a system composed by a lens and a vacuum-compatible halogen lamp has been allocated within the detector head. In this paper, the design of the scintillator probe, as well as the new technique used to analyze the data through spectrograms will be described. A last section is devoted to discuss the diagnosis prospects of this method for ITER [M. Shimada et al., Nucl. Fusion 47, S1 (2007)]. [ABSTRACT FROM AUTHOR]

A thermographic camera and four hard x-ray detectors have been developed to measure the runaway electrons in the HT-7 tokamak. The synchrotron radiation originated from the runaway electrons was measured by an infrared (IR) camera working in the wavelength ranges of 7.5–13 μm. With a tangential viewing into the plasma in the direction of the electron approach on the equatorial plane, the synchrotron radiation from the runaway electrons was measured in a full poloidal cross section. Three NaI scintillators are used to monitor the hard x-ray radiation (HXR) in the energy ranges of 0.5–7 MeV, and a CdTe detector is used to monitor the low-energy HXR in the energy ranges of 0.3–1.2 MeV. The combination of infrared camera and hard x-ray detectors provides a powerful tool to investigate the runaway electron dynamics in HT-7. Runaways in the core and edge regions are monitored simultaneously. The parameters of runaway beam in the core are deduced from the IR pictures. The interaction of runway electrons with toroidal magnetic field ripple is monitored from the HXR emission. [ABSTRACT FROM AUTHOR]

We have developed and installed a new, second escaping fast ion probe for the small major radius side of the compact helical system. This is a Tokamak Fusion Test Reactor type scintillator-based probe and is intended to detect unconfined helically trapped fast ions whose orbits largely deviate from magnetic flux surfaces. We observed a localized light spot on the scintillator screen in neutral beam-heated discharges and it was confirmed to be a true fast ion signal. The analysis suggests that the probe detects partially thermalized, pitch angle scattered beam ions. [ABSTRACT FROM AUTHOR]

Documents the calibration procedure for neutron counters and scintillators used to measure the neutron emission produced by the DIII-D tokamak. Detectors and calibration; Detector comparisons; Comparison with other diagnostics.

A four-channel scintillation detector capable of measuring tritons, protons, and alphas escaping from a tokamak plasma was operated during the 1986 run period of the Tokamak Fusion Test Reactor (TFTR). Signals consistent with the expected 1-MeV triton behavior have been observed during deuterium operation. Backgrounds associated with neutrons/gammas and soft x rays have been evaluated in situ and are shown to be at the ≈ 10%-20% level for the present detector. Such a detector is capable of measuring escaping alphas in deuterium-tritium-fueled tokamaks such as TFTR. [ABSTRACT FROM AUTHOR]

A digital pulse shape discrimination system (DPSD) has been used in conjunction with collimated NE213 scintillators for neutron spectroscopic measurements at high count rates (MHz range) in Joint European Torus discharges (DD and DT fueled, neutral beam injection and rf heated). The system, developed at ENEA-Frascati, is based on a commercial 200 MHz 12-bit analog to digital transient recorder card, which digitizes the direct output signal from the anode of a photomultiplier. Among the unique features of this DPSD system are the possibility of postexperiment data reprocessing, high count rate operation, and simultaneous neutron and gamma (γ) spectroscopy. Separation between γ and neutron (n) events is performed by means of dedicated software exploiting the charge comparison method; separate n and γ pulse height distributions are obtained and an example of neutron spectrum unfolding is shown. Implications of the DPSD in future neutron diagnostic systems on large and next step tokamaks are discussed. [ABSTRACT FROM AUTHOR]

Good confinement of alpha particles in a large magnetic fusion device is a precondition for building a magnetic fusion reactor. The direct measurement of alpha particle losses is of particular interest. Appropriate diagnostics are now being prepared for the Joint European Torus tokamak: a scintillator probe and a set of Faraday cups. Both systems are capable of measuring charged fusion products and ion cyclotron resonance heating tail ions. The design of the lost alpha particle scintillator probe is in the scope of this article. It will allow the detection of particles with a gyroradius between 20 and 140 mm (15% resolution) and a pitch angle between 30° and 86° (5% resolution). As scintillating material P56 will be used. The light emitted by the scintillator caused by charged particles that pass the collimator and hit the scintillator will be detected via a set of optical lenses and a coherent image fiber bundle with a charge coupled device camera and a photomultiplier array. In the following the present design of the scintillator probe with emphasis on the performance of the system, structural resistance against plasma disruptions, and the requirements on the heat protection against plasma and neutral beam induced thermal loads will be described. [ABSTRACT FROM AUTHOR]

The light output of ZnS scintillators used to detect escaping fusion products in the TFTR Tokamak is studied with 3.5-MeV alpha and 3-MeV proton beams. The emitted light first increases linearly with beam current and then saturates. In all cases investigated, the saturations start at a fairly constant absorbed power density of about 1 mW/cm². The scintillators have adequate time response up to 50-100 kHz. [ABSTRACT FROM AUTHOR]

This paper reviews the operating experiences obtained with a set of scintillator-based escaping fast ion detectors which have been used successfully for several years on the TFTR tokamak. There have been several operational problems which need to be resolved before these detectors are used to measure 3.5 MeV DT alphas in 1993. The main problem has been overheating by edge plasma heat flux for large major radius plasmas, when the detectors were not shadowed by the adjacent limiter. Other problems have been due to runaway electron-induced x-ray flux and scintillator and foil damage. [ABSTRACT FROM AUTHOR]

A two-dimensional, tangentially viewing, soft-x-ray pinhole camera has been fabricated to provide internal shape measurements on the PBX-M tokamak. It consists of a scintillator at the focal plane of a foil-filtered pinhole camera, which is, in turn, fiber-optically coupled to an intensified framing video camera (Δ t ≥ 3 ms). Automated data acquisition is performed on a stand-alone image processing system, and data archiving and retrieval take place on an optical disk video recorder. The derivation of the poloidal emission distribution from the measured image is done by fitting to model profiles. [ABSTRACT FROM AUTHOR]

A diagnostic for escaping charged fusion products is presently being tested on tokamak fusion test reactor (TFTR). It consists of a 1 × 1-in. ZnS scintillator screen located inside a movable probe at the bottom of the TFTR vacuum vessel. The alphas or tritons hit the scintillator screen where they create visible light pulses which are fiber-optically coupled to photomultiplier tubes and/or an intensified video camera for recording and analysis. [ABSTRACT FROM AUTHOR]

Measurements of fluctuations in the neutron yield are made on the tokamak fusion test reactor (TFTR) with plastic scintillators. Light from the scintillators is coupled through acrylic rods or fiber-optic cables to photomultipliers operated in current mode. Discrimination against hard x rays is accomplished through comparison with the signal from a ZnS([sup 6]Li) scintillator. These measurements are useful in studies of deuterium pellet deposition, of the acceleration of beam ions during major radial compression, and of MHD instabilities. Techniques for measuring the neutral beam density profile and Q[sup equv, sub dt], using neutron fluctuation measurements during pellet injection also have been proposed. [ABSTRACT FROM AUTHOR]