Ioffe Physico-Technical Institute Research Articles

60 Years of neutral particle analysis: from early tokamaks to ITER

Academician A. D. Sakharov’s idea concerning the emission of atomic flux from hot plasma (1951) inspired scientists of A. F. Ioffe Physico-Technical Institute to create the first in the world instrument called Neutral Atom Analyzer in 1960 and then in 1961 to use it successfully on the Alpha device (USSR, 1958–1963). Now the analysis of fluxes of fast atoms referred to as Neutral Particle Analysis (NPA) is one of the main diagnostic methods for the ion component of plasma in tokamaks, stellarators, and other devices. NPA provides a unique opportunity for studying the ion distribution functions, ion temperatures and hydrogen isotope ratio in hot plasma. Neutral particle analyzers developed at the Ioffe Institute were widely used in the USSR until the late 1970s, and afterwards began to be employed worldwide. Since then, most of the information on the ion distribution functions and the behavior of fast ions in fusion plasma is obtained from NPA measurements on all leading magnetic confinement fusion systems worldwide. The specialized complex of atom analyzers currently being created at the Ioffe Institute is included in the primary list of ITER diagnostics. The integration of this complex on ITER is expected to begin in 2025.

Chronology of the Ioffe Institute’s Century in Documents from the Archive of the Ioffe Physico-Technical Institute. The Beginning

Chronology of the Ioffe Institute’s Century in Documents from the Archive of the Ioffe Physico-Technical Institute. The Beginning

Prospects for solar energy in Russia

Solar energy is one of the most promising industries of renewable power engineering. In Russia, the large-scale development of solar engineering is related to the launch of the production of thin-film solar modules based on amorphous silicon at Hevel LLC in February 2015. This company is qualified to create a full-fledged high-tech solar energy industry as an alternative to traditional power sources. Its activity is aimed at improving the efficiency, reducing the production cost, and expanding the scope of application of solar modules. In order to support and develop this industry, the Research and Development Center for Thin-Film Technologies started to operate under the Ioffe Physicotechnical Institute in 2012, its main goal being to improve the key parameters of solar modules based on amorphous silicon in the interests of Hevel LLC.

The Blue LED Nobel Prize: Historical context, current scientific understanding, human benefit

The Blue LED Nobel Prize: Historical context, current scientific understanding, human benefit

Benchmark of coupling codes (ALOHA, TOPLHA and GRILL3D) with ITER-relevant Lower Hybrid antenna

In order to assist the design of the future ITER Lower Hybrid launcher, coupling codes ALOHA, from CEA/IRFM, TOPLHA, from Politecnico di Torino, and GRILL3D, developed by Dr. Mikhail Irzak (A.F. Ioffe Physico-Technical Institute, St. Petersburg, Russia) and operated by ENEA Frascati, have been compared with the updated (six modules with four active waveguides per module) Passive-Active Multi-junction (PAM) Lower Hybrid antennas. Both ALOHA and GRILL3D formulate the problem in terms of rectangular waveguides modes, while TOPLHA is based on boundary-value problem with the adoption of a triangular cell-mesh to represent the relevant waveguides surfaces. Several plasma profiles, with varying edge density and density increase, have been adopted to provide a complete description of the simulated launcher in terms of reflection coefficient, computed at the beginning of each LH module, and of power spectra. Good agreement can be observed among codes for all the simulated profiles.

A 16 × 16 hybrid matrix array detector for visualizing XUV plasma radiation

A prototype of a hybrid matrix detector for ultrafast plasma visualization is designed. It uses silicon XUV photodiodes made by the unique technology of the Ioffe Physicotechnical Institute, Russian Academy of Sciences. The principal 16 × 16-format hybrid module consists of eight submodules with 2 × 16-format linear matrices integrated with a 32-channel preamplifier and four fast multiplexers with eight channels. The module is designed to ensure the possibility of integrating into large-format matrices. The data acquisition system consists of eight synchronous 12-bit 4-channel analog-to-digital converter modules with a 40-MHz maximal digitization frequency and reads a complete frame for <1 μs. Each channel has a 64-Mb vehicle-borne memory limiting the data accumulation period to a 0.8-s value, when the rate is at maximum.

Preliminary characterization of semiconductor detectors in the soft X-ray range using synchrotron radiation from the VEPP-4 storage ring

A photodiode developed at the Ioffe Physico-Tech nical Institute (St. Petersburg) and referred to in the literature as the SPD has been preliminarily calibrated by the primary-detector-based method. The possibility of application of SPD photodiodes as radiometric detectors has been investigated. The AXUV-100 photodiode (IRD Inc., United States) was used as a primary detector. The radiation strength of both detectors has been tested. It was revealed that, being more radiation-resistant, the SPD had radiometry characteristics that were not worse than those of the AXUIV-100.

Neutral atom analyzers for diagnosing hot plasmas: A review of research at the ioffe physicotechnical institute

Research on neutral particle diagnostics of thermonuclear plasmas that has been carried out in recent years at the Ioffe Physicotechnical Institute of the Russian Academy of Sciences (St. Petersburg, Russia) is reviewed. Work on the creation and improvement of neutral atom analyzers was done in two directions: for potential applications (in particular, on the International Thermonuclear Experimental Reactor, which is now under construction at Cadarache in France) and for investigation of the ion plasma component in various devices (in particular, in the largest tokamaks, such as JET, TFTR, and JT-60). Neutral atom analyzers are the main tool for studying the behavior of hydrogen ions and isotopes in magnetic confinement systems. They make it possible to determine energy spectra, to perform the isotope analysis of atom fluxes from the plasma, to measure the absolute intensity of the fluxes, and to record how these parameters vary with time. A comparative description of the analyzers developed in recent years at the Ioffe Institute is given. These are ACORD-12/24 analyzers for recording 0.2–100-keV hydrogen and deuterium atoms with a tunable range of simultaneously measured energies, CNPA compact analyzers for a fixed energy gain in the ranges 80–1000 eV and 0.8–100 keV, an ISEP analyzer for simultaneously recording the atoms of all the three hydrogen isotopes (H, D, and T) in the energy range 5–700 keV, and GEMMA analyzers for recording atom fluxes of hydrogen and helium isotopes in the range 0.1–4 MeV. The scintillating detectors of the ISEP and GEMMA analyzers have a lowered sensitivity to neutrons and thus can operate without additional shielding in neutron fields of up to 109 n/(cm2 s). These two types of analyzers, intended to operate under deuterium-tritium plasma conditions, are prototypes of atom analyzers created at the Ioffe Institute for use in the International Thermonuclear Experimental Reactor. With these analyzers, a number of new results have been obtained in recent years in various devices. Some results are presented from investigation of ions in the Globus-M spherical tokamak, the W7-AS stellarator, and the JET tokamak by means of the analyzers developed at the Ioffe Institute. Challenges and opportunities for applying these diagnostics in the International Thermonuclear Experimental Reactor project are discussed.

Experimental and numerical investigation into the supersonic flow of a weakly ionized plasma around a dihedral angle: Magnetohydrodynamic control of the flow pattern and heat fluxes toward the wall

The results of experimental and numerical investigations into magnetohydrodynamic actions on the supersonic flow of a weakly ionized xenon plasma around a wedge are presented. The conditions of numerical simulation correspond to the conditions of experiments carried out on the Bol’shaya shock tube at the Ioffe Physicotechnical Institute.

Holographic diagnostics of the plasma: A review

A review of works concerning holographic diagnostics of the plasma that have been conducted in the laboratory of plasma optics at the Ioffe Physico-Technical Institute since 1966 is presented. The potential and features of holographic diagnostics as applied to different plasma objects are discussed. The results of investigations into the laser-induced spark in gases and current sheets forming in 2D and 3D magnetic fields with X lines are reported.

Testing the neutron attenuator based on 6LiH for γ-ray diagnostics of plasmas in the JET tokamak

A 6LiH attenuator of a neutron flux incident on a detector is used to reduce the γ-ray background induced by neutrons in the detector material. This attenuator has been tested during experiments with deuterium (DD) plasmas on the JET tokamak. A specimen of the neutron attenuator with dimensions of ⊘30 × 300 mm has been developed by the Russian Academy of Sciences’ Ioffe Physico-Technical Institute and inserted into a vertical collimator used for γ spectrometry of plasmas. To compare γ-ray spectra recorded with and without the 6LiH attenuator being mounted, identical discharges with heating of the DD plasma by a neutral particle beam have been selected. For γ rays with energies of 3 MeV can be attributed to the transparency of the 6LiH attenuator for γ rays. This portion of the spectrum is due to γ radiation of the plasma and γ rays induced by neutrons in the constructional materials of the tokamak. To estimate the efficiency of the 6LiH attenuators as a mandatory component of the ITER γ-ray diagnostic system, it is necessary that measurements be taken in deuterium-tritium (DT) discharges.

Development of a technique for high-speed γ-ray spectrometry

A technique for high-speed γ-ray spectrometry was developed for γ-ray diagnostic experiments on the ITER tokamak and tested at the Ioffe Physico-Technical Institute on the cyclotron and the GLOBUS-M and TUMAN-3M tokamaks. This technique was used to upgrade the γ-ray diagnostic system of the JET tokamak. It was shown by the tests that the new technique compares favorably to the traditional one in that it allows the limiting counting rate of the spectrometer to be increased by at least an order of magnitude without noticeable deterioration of its energy resolution.

Monte carlo simulation and optimization of three-axis neutron spectrometer for the PIK reactor

Mathematical modeling of estimated parameters for optimization of the three-axis neutron spectrometer developed at the Ioffe Physicotechnical Institute for the PIK reactor have been performed. The expected intensities and spatial distributions of neutron fluxes at the points of location of spectrometer units are reported. The spectrometer resolution function is calculated.

Acoustooptic interaction in science and applications

Main results of acousto-optic investigations in physical acoustics of solids obtained in Ioffe Physico-Technical Institute during recent yeas are presented. Both monocrystals, and glass alloys of different compositions were used as objects of researches. The studies were fulfilled in wide ranges of optical wavelengths (0.63–10.6 mkm), temperatures (77–400 K) and frequencies (10–1800 MHz) of bulk and surface acoustic waves.

Effect of SiO/sub 2/ passivating layer in segmented silicon planar detectors on the detector response

Silicon detectors with a fine segmentation (micropixel and microstrip) are the main type of detectors used in the inner trackers of Large Hadron Collider (LHC) experiments. Due to the high luminosity of the LHC machines they are required to have a fast response to fit the short shaping time of 20 ns and to be radiation hard. Evaluation of silicon microstrip detectors developed for the ATLAS silicon tracker and carried out under collaboration of CERN and Ioffe Physico-Technical Institute has shown the reversal of the pulse polarity in the detector response to short-range radiation. Since the negative signal is of about 30%-60% of the maximal positive one, the effect strongly reduces the charge collection efficiency even in nonirradiated detectors. The investigation presents the consideration of the origin of a negative response in Si microstrip detectors and the experimental proof of the model. The study of the effect has been carried out using "baby" strip detectors with a special design: each strip has a window in a metallization, which covers the p/sup +/ implant. The scan of a laser across the strips clearly shows that the negative response is observed along the scan in the interstrip gap. As soon as the light spot is placed on the strip p/sup +/ implant the negative response disappears and the value of the charge collected by the active strip proportionally increases. A phenomenological model considers the origin of the negative response as the effect of carrier trapping at the Si-SiO/sub 2/ interface between the strips.

Computer-Aided Processing of Optical Measurements in Aeroballistic Experiment

The idea of semiautomatic computer-aided processing of photos as applied to the problem of external ballistics, namely, determination of aerodynamic characteristics of flying objects from trajectory data, is put forward. The impetus to write this article is the development of an original software product that was used to advantage in processing data of full-scale experiments with the aim of creating a photo database of ballistic experiments performed at the Ioffe Physicotechnical Institute. This software is integrated into the Arkhimed information-retrieval system used to control this database. The advantages of the semiautomatic approach over “manual” measurements and the fully automatic version are indicated.

Preface

Preface

Magnetic field control of a supersonic nitrogen flow

Magnetohydrodynamic impact on a cold supersonic nitrogen flow with external magnetic field was realized in an experimental complex based on the Big Shock Tube at the Ioffe Physicotechnical Institute. A pulsed supersonic flow with a Mach number of M=4 and steady phase duration of about 1.5 ms was created by expansion of the shock-heated nitrogen flow from a supersonic nozzle. The gas was ionized by pulsed discharge between two electrodes mounted on the nozzle wall so that an electric current of up to ∼500 A passed in the direction perpendicular to the gas flow at the dielectric wall. External magnetic field ∼0.3 T was perpendicular to the gas flow and the current direction. It is established that the magnetic field significantly modifies the shock wave structure in the flow.

FULLSPECTRUM: A new PV wave of more efficient use of the solar spectrum

The purpose of this paper is to present to the Russian scientific community a research program that, with the cooperation of one of its institutional members, the Ioffe Physicotechnical Institute, has been presented and sponsored by the European Commission (EC) in order to provide a long-term basis for the development of the photovoltaic conversion of solar energy. This program constitutes what in the EC is known as an integrated project: it is called FULLSPECTRUM for short, as in the title of this paper, and involves 19 research centers in eight different countries with a grant of 8.4 million euros for five years.

On the possibility of the long-term forecast of solar activity using radiocarbon sunspot proxy

Ioffe Physico-Technical Institute, Russian Academy of Sciences, Politekhnicheskaya str. 26,194021 St.Petersburg, Russia e-mail: Maxim.Ogurtsov@mail.ioffe.ruAbstract. The reconstruction of sunspot numbers from the decadal radiocarbon series wasmade for the time interval 8005 B.C. - 1945 A.D using five-box carbon exchange model. Analysesshowed apparent persistency in the reconstructed Wolf number series. It indicates the existenceof long-term memory in solar activity. Nonlinear forecast of the mean value of Wolf number ismade for the next 40 years using obtained radiocarbon proxy. Comparison of the results withthe long -term forecasts of the other authors was performed.