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Fast ions play a crucial role in plasma heating, and their behavior in the plasma must be accurately understood. A diagnostics method based on charge exchange emission from the n = 4 − 3 transition (λ0 = 468.6 nm) of energetic 3He produced by the deuteron–deuteron reaction has been proposed as a for fast deuterons with energies in the order of MeV. The proposed method has the following advantages: No beam emission interferes with the spectra, the direction of the measuring line of sight, and the injection angle of the diagnostic beam can be freely determined. In previous studies, due to competing bremsstrahlung, it was expected that the proposed method will not be practical in the case of high electron density operation. This paper makes the proposed method available for measurement even at high electron densities by optimizing the measurement line of sight direction and the diagnostic beam incidence angle. This allows an electron density five times larger than the range of applications shown in previous studies. This result will contribute to measure of DT alpha in ITER. [ABSTRACT FROM AUTHOR]

The fast deuteron (non-Maxwellian component) diagnostic method, which is based on the higher resolution optical spectroscopic measurement, has been developed as a powerful tool. Owing to a decrease in the D–H charge-exchange cross section, the diagnostic ability of conventional optical diagnostic methods should be improved for ∼MeV energy deuterons. Because the 3He–H charge-exchange cross section is much larger than that of D–H in the ∼MeV energy range, the visible light (VIS) spectrum of 3He produced by the dueteron–dueteron (DD) reaction may be a useful tool. Although the density of 3He is small because it is produced via the DD reaction, improvement of the emissivity of the VIS spectrum of 3He can be expected by using a high-energy beam. We evaluate the VIS spectrum of 3He for the cases when a fast deuteron tail is formed and not formed in the ITER-like beam injected deuterium plasma. Even when the beam energy is in the MeV energy range, a large change appears in the half width at half maximum of the VIS spectrum. The emissivity of the VIS spectrum of 3He and the emissivity of bremsstrahlung are compared, and the measurable VIS spectrum is obtained. It is shown that the VIS spectrum of 3He is a useful tool for the MeV beam deuteron tail diagnostics. [ABSTRACT FROM AUTHOR]

Fusion gamma rays were measured in D–[sup 3]He experiments using negative ion-based neutral beam injection (N-NBI) in reverse shear plasmas of the JT-60 tokamak. [sup 3]He gas was puffed at plasma initiation and just before N-NB injection. The D–[sup 3]He reaction produces 3.6 MeV alphas and 14.7 MeV protons, but there is also a small branch which provides [sup 5]Li and 16.7 MeV gamma rays. The total D–[sup 3]He reaction rate can be evaluated from measurement of gamma rays of the [sup 3]He (d,γ) [sup 5]Li reactions using a 3 in. diam by 3 in. long Bi[sub 4]Ge[sub 3]O[sub 12] scintillator. The gamma-ray detector was located 17 m below the plasma center and measured the gamma-rays in a vertical line of sight. The detector was mounted inside a heavy collimator with polyethylene and lead shielding. The floor penetration, a 4×8 cm[sup 2] hole, was used as a precollimator. Energy calibration of the detector was done with photopeaks for neutron capture gamma rays from the structural materials in D–D discharges. The detection efficiency was calculated with Monte Carlo code MCNP-4B for 16.7 MeV gammas. The pulse height analysis of the gamma rays resulted in the D–[sup 3]He fusion power of 110±30 kW in this experiment. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Analyzes the expected performance of several neutron camera arrangements for the International Thermonuclear Experimental Reactor. Examination of proposed cameras wherein neutron fluxes are inferred from [sup 16]N decay gammas in dedicated flowing water loops; Accuracy of the measurements; Sufficiency of the spatial sampling provided by the reference designs.

Discusses neutron diagnostic techniques for the control and evaluation of thermonuclear plasmas in an ignition device to test engineering concepts, the International Thermonuclear Experimental Reactor (ITER). Principal features of the ITER design; Neutron flux monitors; Neutron activation system; Radial and vertical neutron cameras.

Design considerations and experimental results are described for a charge exchange neutral particle mass and energy analyzer for JT-60, which analyzes H, D, and He simultaneously up to a maximum energy of 110 keV. The analyzer has separately a 180° deflection magnet for momentum analysis and an electrostatic deflector for mass analysis. The way to control the effect of the electric fringe fields in order to expand the detectable energy range is studied by numerical simulation. The deflector is then designed, made of two triangular plates and three additional electrodes for the control of the fringe fields. The effect of the deflector is demonstrated experimentally. Energy and mass resolution and the relation between the incident ion energy and the magnetic field strength are measured. The results of the calibration experiments agree with the designed value. [ABSTRACT FROM AUTHOR]

The possibility of measurement of fuel ratio from the DT/DD reaction ratio with a neutron spectrometer in the International Thermonuclear Experimental Reactor was studied. The results of neutron transport calculations using the Monte Carlo N-particle [MCNP, a general Monte Carlo N-particle transport code, version 4C, LA-13709, edited by J. F. Briesmeister, Los Alamos National Laboratory, 2000] code system indicated the possibility of DD spectrum separation from the scattered/energy-degraded neutrons derived from DT neutrons by selection of the measurement location and collimator design. A time-of-flight spectrometer was used in this study. An experiment using DD and DT neutrons from an accelerator was conducted at the Japan Atomic Energy Agency Fusion Neutronics Source facility. Using a sophisticated circuit with three discriminators for the first detector, separation of DD and DT neutron components of the spectrum in the megahertz region was confirmed experimentally. [ABSTRACT FROM AUTHOR]

For fusion neutron profile monitoring, we propose to use a new position sensitive fast neutron detector (PSFND). We have considered an applicability of the present PSFND to two types of fusion neutron camera; a pinhole camera and a double crystal time-of-flight camera. [ABSTRACT FROM AUTHOR]

A ³He ionization chamber was used to measure neutron spectra on TFTR during 1987. The ion temperature was deduced for one set of Ohmically heated plasmas and agreed within 20% with that measured by other diagnostics. The absolute efficiency was calibrated using a d-d neutron generator. [ABSTRACT FROM AUTHOR]

Radiation losses from the main plasma of the JAERI Tokamak-60 (JT-60) were measured by a 15-channel bolometer array and those from divertor chambers in the ion and electron drift sides were each measured by two bolometers. The bolometric detector consisting of three layers (5-µmthick gold absorber, 7-µm-thick polyimide foil, and 0.1-µm-thick gold resistor grid) was developed for this measurement. In typical diverted discharges with NB heating, the ratios of power radiated from the main and divertor chambers to the absorbed power were approximately 10% and 20%, respectively. Intense poloidal asymmetries of radiated power localized near the X point outside the torus were observed in diverted discharges. The profiles of the radiated power were reconstructed by an Abel inversion with an asymmetric term. On the other hand, a poloidally asymmetric radiation band localized near the inner wall, "marfe," was observed for dense plasmas in limiter discharges with neutral beam heating. [ABSTRACT FROM AUTHOR]

For the diagnosis of confined alpha particles in D-T plasma, we propose the observation of 2.186 MeV gamma ray produced by D(α,γ)6Li reaction. However, there are few nuclear data of the D(α,γ)6Li reaction rate. Therefore, we carried out the experimental verification of the gamma ray diagnostics technique by using an accelerator. Helium ions in the energy range of 2–4 MeV were bombarded into a thick deuterated polyethylene, where the gamma ray spectrum was measured with a Ge detector. Photopeak of the 2.186 MeV gamma ray was clearly observed. From our experiment, the emission rate of the 2.186 MeV gamma ray from the D(α,γ)6Li reaction is estimated to be 1012–1013 s-1 in the ITER typical plasma condition. So we obtained a good prospect of the gamma ray measurement as the confined alpha particle diagnostics by using a high efficiency detector. [ABSTRACT FROM AUTHOR]

Examines the irradiation effects on potential diagnostic materials and components of the International Thermonuclear Experimental Reactor. Radiation-induced electrical damage and conductivity in potential insulators; Radiation-induced absorption and radio luminescence in potential optic materials; Changes to reflectivity and surface properties of bulk metal mirrors.

The fast deuteron (non-Maxwellian component) diagnostic method, which is based on the higher resolution optical spectroscopic measurement, has been developed as a powerful tool. Owing to a decrease in the D-H charge-exchange cross section, the diagnostic ability of conventional optical diagnostic methods should be improved for ∼MeV energy deuterons. Because the 3 He-H charge-exchange cross section is much larger than that of D-H in the ∼MeV energy range, the visible light (VIS) spectrum of 3 He produced by the dueteron-dueteron (DD) reaction may be a useful tool. Although the density of 3 He is small because it is produced via the DD reaction, improvement of the emissivity of the VIS spectrum of 3 He can be expected by using a high-energy beam. We evaluate the VIS spectrum of 3 He for the cases when a fast deuteron tail is formed and not formed in the ITER-like beam injected deuterium plasma. Even when the beam energy is in the MeV energy range, a large change appears in the half width at half maximum of the VIS spectrum. The emissivity of the VIS spectrum of 3 He and the emissivity of bremsstrahlung are compared, and the measurable VIS spectrum is obtained. It is shown that the VIS spectrum of 3 He is a useful tool for the MeV beam deuteron tail diagnostics.