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Due to high neutron and gamma‐ray yields and large size plasmas many future fusion reactor plasma parameters such as fusion power, fusion power density, ion temperature, fuel mixture, fast ion energy and spatial distributions can be well measured by various fusion product diagnostics. Neutron diagnostics provide information on fusion reaction rate, which indicates how close is the plasma to the ultimate goal of nuclear fusion and fusion power distribution in the plasma core, which is crucial for optimization of plasma breakeven and burn. Depending on the plasma conditions neutron and gamma‐ray diagnostics can provide important information, namely about dynamics of fast ion energy and spatial distributions during neutral beam injection, ion cyclotron heating and generated by fast ions MHD instabilities. The influence of the fast particle population on the 2‐D neutron source profile was clearly demonstrated in JET experiments. 2‐D neutron and gamma‐ray source measurements could be important for driven plasma heating profile optimization in fusion reactors. To meat the measurement requirements in ITER the planned set of neutron and gamma ray diagnostics includes radial and vertical neutron and gamma cameras, neutron flux monitors, neutron activation systems and neutron spectrometers. The necessity of using massive radiation shielding strongly influences the diagnostic designs in fusion reactor, determines angular fields of view of neutron and gamma‐ray cameras and spectrometers and gives rise to unavoidable difficulties in the absolute calibration. The development, testing in existing tokomaks and a possible engineering integration of neuron and gamma‐ray diagnostic systems into ITER are presented.

The absolute measurement of neutron emission rate from the whole plasma is a very important diagnostics as a fusion power monitor in fusion experimental devices with D‐T or D‐T operations. Here measurement techniques of time‐resolved and time‐integrated absolute neutron emission on the present tokamaks and ITER are reviewed. In the present tokamaks, fission chamber installed outside the vacuum vessel are very popular in the absolute neutron emission rate measurement. As well as conventional neutron monitors installed outside the vacuum vessel, in‐vessel neutron monitors using micro fission chamber are proposed for the absolute neutron emission rate measurement in ITER. The neutron activation system provides time‐integrated measurements of the total neutron yield with high accuracy by using well known neutron reaction cross sections, which is useful to maintain a robust measure of fusion energy production with stability and wide dynamic range. The calibration of the relation between the neutron emission ra...

As a large‐scale plasma experimental device is planned and designed, the importance of investigations on irradiation effect of 14 MeV neutron increases and an experimental database is desired to be piled up. Recently, intense streaming of fast neutron from ports are reported and degradation of superconducting magnet performance is anticipated. To investigate the pure neutron effect on superconducting magnet materials, a cryogenic target system was newly developed and installed at Fusion Neutronics Source in Japan Atomic Energy Research Institute. Although production rate of 14 MeV neutron is not large, only 14 MeV neutron can be supplied to irradiation test without gamma ray. Copper wires, superconducting wires, glass fiber reinforced composites are irradiated and the irradiation effects are characterized. At the same time, sensors for measuring temperature and magnetic field are irradiated and their performance was investigated after irradiation. This paper presents outline of the cryogenic target system and some irradiation test results.

Design activity of International Thermonuclear Experimental Reactor clarifies intense neutron streaming from ports for neutral beam injectors. Energy spectrum of the streaming is very wide and 14 MeV neutron and gamma ray are the typical radiations. Large amount of glass fiber reinforced plastics will be used in a superconducting magnet system as an electric insulation material and a support structure, for such organic material is easy to manufacture, and light and cheap. In this report, effects of 14 MeV neutron and gamma ray irradiation on interlaminar shear strength and fracture mode are investigated using G‐10CR small specimen of which configuration was proposed as a standard for evaluation of the interlaminar shear strength. A short beam test under three point bending was conducted at room temperature and 77 K. Neutron fluence of 3.91 × 1019 n/m2 was irradiated and the specimens did not show clear degradation of the strength. On the other hand, gamma ray irradiation of 1 MGy made the specimen weaker ...

Activation cross sections for the (n, n′) reaction were measured by means of the activation method at the neutron energies of 3.1 and 2.54 MeV by using a pulsed neutron beam. Target nuclei were 79Br, 90Zr, 197Au, and 207Pb, whose half‐lives were between 0.8 and 8 s. The cross section for the 90Zr (n, n′) 90mZr reaction was obtained for the first time in this energy range. The d‐D neutrons were generated by bombarding a deuterated titanium target with a 350‐keV d+ beam at the 80‐degree beam line of the Fusion Neutronics Source at the Japan Atomic Energy Research Institute. In order to obtain reliable activation cross sections, careful attention was paid to correct the efficiency for a volume source, and the self‐absorption of gamma rays in an irradiated sample. The systematics of the (n, n′) reaction at the neutron energy of 3.1 MeV, which could be predicted within an accuracy of 50%, was proposed on the basis of our data.

Activation cross sections for deuteron‐induced reactions on aluminum, copper, and tungsten were measured by using a stacked‐foil method. The stacked foils were irradiated with deuteron beam at the AVF cyclotron in the TIARA facility, JAERI. We obtained the activation cross sections for 27Al(d,2p)27Mg, 27Al(d,x)24Na, natCu(d,x)62,63Zn, 61,64Cu, and natW(d,x)181–184,186Re, 187W in the 22–40 MeV region. These cross sections were compared with other experimental ones and the data in the ACSELAM library calculated by the ALICE‐F code.

The current status of nuclear data evaluations for fusion technologies is reviewed. Well‐qualified data are available for neutronics and activation calculations of fusion power reactors and the next‐step device ITER, the International Thermonuclear Experimental Reactor. Major challenges for the further development of fusion nuclear data arise from the needs of the long‐term fusion programme. In particular, co‐variance data are required for uncertainty assessments of nuclear responses. Further, the nuclear data libraries need to be extended to higher energies above 20 MeV to enable neutronics and activation calculations of IFMIF, the International Fusion Material Irradiation Facility. A significant experimental effort is required in this field to provide a reliable and sound database for the evaluation of cross‐section data in the higher energy range.

A new spectrometer has been developed, including a pencil‐beam 14‐MeV neutron source and a telescope system with two SSDs of ΔE and E, in order to measure double differential charged‐particle emission cross sections (DDXs). The spectrometer can supply quite good performance, i.e., low minimum measurable energy of below 2 MeV for alpha particles and a very high S/N ratio over 10. Highly accurate charged‐particle emission DDX data can thus be expected to be measured by this spectrometer. From the test measurement for aluminum, the validity was confirmed by comparing the angular differential cross section (ADX) and the total charged‐particle emission cross section with other data. Also, the measurement for beryllium has been carried out. From the result of the measurement, the acceptable agreement with the evaluation was confirmed in the energy spectrum. The precise branching ratio of the breakup nuclear reaction of beryllium is now being analyzed from the obtained DDX data.

200 keV polarized electron source with load‐lock system has been constructed to produce a beam with high peak current and low emittance that are required by a future linear collider. GaAs photocathode was cleaned by atomic hydrogen and dark currents between the electrodes of the gun that degrade an NEA (Negative Electron Affinity) surface of photocathode could be reduced to less than 1 nA at 200 kV. Recent data on photocathode preparation and dark current measurement are reported in this paper.

In order to produce the lower emittance electron beam, the higher field gradient must be used for the gun. From this point of view, we try to develop both of a polarized DC‐gun and RF‐gun. In case of a 200 keV polarized DC‐gun at Nagoya University, the accelerating gradient at the photocathode surface was designed to be 3 MV/m, and the dark current emitted from the SUS electrodes was suppressed below 1 nA. To increase the gradient, we tested the property of pure Titanium as a new electrode material. The tested electrode showed small dark current (∼1 nA) even at field gradient of 88 MV/m, which is as twice as higher than that of SUS electrode. Concerning the feasibility of a polarized RF‐gun, it seems difficult for the NEA surface to survive in high field gradient of 100 MV/m. Therefore, we proposed a new type of polarized electron source using two‐photon excitation method, for which it is not necessary to use the NEA surface to extract electrons into vacuum. For this method, the polarization higher than 9...

Parametric decay waves were observed during second harmonic ICRF heating experiments in JT‐60. The parametric decay process is probably that the pump wave decays into ion Bernstein waves (IBW) and ion cyclotron quasi‐modes. Because the decay wave frequency at a toroidal magnetic field of 3.3–4.5 T agreed with the predicted frequency of IBW which was assumed to be excited parametrically near the ICRF antennas. The decay wave intensity decreased with increasing toroidal magnetic field. Increase in radiation loss induced by ICRF heating at the plasma current of 1 MA was not proportional to the pump wave power. Those results suggest that the parametric decay wave was one of the sources of the impurity production during the second harmonic ICRF heating experiments.