Gamma ray spectrometry measurements at high detector counting rates (on the order of 107 s−1 and higher) are relevant for high-temperature plasma diagnostics for existing tokamaks and during the ...development of gamma ray diagnostic systems for the ITER tokamak under construction. At high loads, to obtain spectra without distortion and with a small amount of dead time, it is necessary to use advanced scintillation detector signal processing methods, which can resolve superimposed pulses. Two algorithms that can be used for digital signal processing of scintillation gamma ray detectors with many piled-up pulses are considered in this article, the fitting and deconvolution methods. These algorithms are compared with both one another and two less sophisticated pulse-height analysis algorithms (maximum height and total sum under the peak) in applications that process model and measured signals. Baseline detection algorithms are also considered, which are necessary when processing signals from detectors. The algorithms are applied to LaBr3(Ce) detector signal processing. For the modeled signals, the best results in terms of the number of resolved events and energy resolution at counting rates up to 2 × 107 s−1 of the LaBr3(Ce) detector are demonstrated by the fitting method. In the real gamma ray measurements at a loading of 5.1 106 s−1, the deconvolution method demonstrated the best energy resolution.
Two neutron spectrometers based on a BC-501A liquid organic scintillator were calibrated. The calibration procedure included obtaining the spectrometers’ response functions to monoenergetic neutron ...emissions and estimating the detectors’ efficiency and is described in this paper. A 9Be(α, nγ)12C nuclear reaction was used as the neutron source. Simultaneous registration of neutrons and gamma quanta with 4.44 MeV energy enabled the extraction of monoenergetic neutrons corresponding to the first excited state of a 12C nucleus. This process is the basis of the neutron–gamma coincidence method, which was applied in the present experiments. The experiments were conducted using the cyclotron at Ioffe Institute, where α particles were accelerated to energies of 2.06, 5.35, 6.05, and 10.08 MeV. The angular dependence of the energy of produced neutrons provided a wide energy range of monoenergetic neutron emission at the same energy of the incident α particle. The response functions of the BC-501A spectrometers on the monoenergetic neutrons were obtained at energies of 1.9 to 10.4 MeV. The neutron registration efficiency of both detectors was estimated in the same energy range as the responses.
Neutron diagnostic system at the Globus-M2 tokamak Iliasova, M.V.; Shevelev, A.E.; Khilkevitch, E.M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2022, Volume:
1029
Journal Article
Peer reviewed
A neutron diagnostic system was developed at the Ioffe Institute as part of the Globus-M2 tokamak to optimize NBI heating conditions and evaluate heating efficiency. The system contains two compact ...neutron spectrometers based on the liquid organic scintillator BC-501A and two gas-discharge counters based on a 10B isotope. The BC-501A spectrometers were calibrated by measuring neutron emission produced in a 9Be(α,n)12C nuclear reaction on the cyclotron facility at the Ioffe Institute. In addition, in situ calibrations of the system, including the neutron spectrometers and the gas-discharge counters, was carried out using an Am–Be neutron source to provide accurate measurements of the total neutron yield from the plasma of the Globus-M2 tokamak. During the plasma experiments at the Globus-M2 tokamak, a deuterium beam was injected into the deuterium plasma that causes a yield of the DD-neutrons with ∼2.45 MeV energy. The neutron spectrometry diagnostic system was used to provide neutron measurements and detect the DD-neutrons in these experiments. The neutron yield and the DD-reaction rate during plasma discharges were evaluated. The energy distributions of neutrons emitted from plasma during discharges with neutron beam injection were reconstructed from the measured neutron spectra.
We present the measured spectra of γ and neutron radiation generated in the
9
Be(
3
He,
p
γ)
11
B and
9
Be(
3
He,
n
γ)
11
C nuclear reactions at an energy of 2.57 MeV of
3
He ions using a BC-501A ...organic detector and an HPGe semiconductor spectrometer. Line shapes of 6.9-MeV γ-transitions from the
9
Be(
3
He,
n
γ)
11
C reaction and 8.92-MeV transitions from the
9
Be(
3
He,
p
γ)
11
B reaction, measured at angles of 0°, 30°, 60°, 90°, and 120° have been determined. The angular distribution of protons emitted when populating the 8.92-MeV level of the
11
B nucleus in
9
Be(
3
He,
p
γ)
11
B reaction, as well as the energy distribution of neutrons in
9
Be(
3
He,
n
γ)
11
C reaction, have been reconstructed.
A gamma-ray spectrometer based on LaBr3(Ce) scintillator has been used for measurements of hard X-ray emission generated by runaway electrons in the FT-2 tokamak plasmas. Using of the fast LaBr3(Ce) ...has allowed extending count rate range of the spectrometer by a factor of 10. A developed digital processing algorithm of the detector signal recorded with a digitizer sampling rate of 250MHz has provided a pulse height analysis at count rates up to 107s−1. A spectrum deconvolution code DeGaSum has been applied for inferring the energy distribution of runaway electrons escaping from the plasma and interacting with materials of the FT-2 limiter in the vacuum chamber. The developed digital signal processing technique for LaBr3(Ce) spectrometer has allowed studying the evolution of runaways energy distribution in the FT-2 plasma discharges with time resolution of 1–5ms.
The decomposition of aluminum hydride complexes with trimethylamine and N-heterocyclic carbene—1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2
H
-imidazol-2-ylidene was studied by a static tensimetric ...method with a membrane null-manometer. The AlH
3
·NMe
3
complex passes into vapor in the form of monomeric molecules and in unsaturated vapor slowly decomposes at 70‒80°С into solid aluminum, gaseous trimethylamine, and hydrogen. The decomposition is accompanied by an induction period, the duration of which decreases as temperature increases. The AlH
3
complex with carbene slowly decomposes at 170‒200°С with a rate practically independent of temperature.
The review presents the evolution of the static tensimetric method from Mendeleev to the present day. A description of a new-generation automatic tensimetric apparatus is given. The specific examples ...show application of the static method with a membrane null-manometer to the study of various processes involving inorganic and coordination compounds: homogeneous gas phase equilibria, heterogeneous condensed phase-vapor equilibria, and kinetics of amidoboranes decomposition.
The possibility of application of deconvolution methods to solving the problem of reconstruction of gamma-radiation spectra of thermonuclear plasma is demonstrated. The DEGAS code is created, which ...implements the modified algorithms of deconvolution. The results of the code application to the test spectra, the discrete spectra of radiation sources, and the gamma spectra measured during the experiments at the JET tokamak using methods for additional plasma heating are presented. The possibility of reconstruction of spectra with low statistics is shown.
