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Fusion product measurements planned for ITER are reviewed from the viewpoint of alpha particle-related physics studies. Recent advances in fusion plasma physics have extended the desirable measurement requirements to the megahertz region for neutron emission rate, better resolution of neutron profiles for the study of internal transport barriers (ITBs), etc. Employing threshold counters and/or scintillation detectors confers megahertz capability on neutron emission rate measurement. The changes in the neutron/alpha particle birth profile due to the formation of ITB and its deviation from uniformity on the magnetic flux surface can be measured by addition of eight viewing chords in an equatorial port plug and seven viewing chords from the divertor to the original radial neutron camera. On the other hand, it is still difficult to measure the distributions of confined and escaping alpha particles. Several proposals to resolve these difficulties are currently under investigation.

The effect of the sawtooth instability on the 2.5 MeV neutron emission in the PLT [Plasma Physics Controlled Nuclear Fusion Research, 1976 (IAEA, Vienna, 1977), Vol. I, p. 21], DIII-D [Plasma Physics Controlled Nuclear Fusion Research, 1986 (IAEA, Vienna, 1987), Vol. 1, p. 159], and TFTR [Plasma Physics Controlled Nuclear Fusion Research, 1984 (IAEA, Vienna, 1985), Vol. I, p. 29] tokamaks is studied. In thermonuclear plasmas, the instability typically results in a 20% reduction in emission. The time evolution of the thermonuclear neutron signal suggests that the sawtooth crash consists of four phases. First, the electron density profile flattens rapidly (in approximately 30 μsec on PLT) but, in some cases, there is little associated change in neutron emission, suggesting that most reacting ions remain confined in the sawtooth region but do not completely mix. After the electron sawtooth, the ions continue to mix, resulting in an approximate 10% reduction in neutron emission in about 0.5 msec. The emission then decays more slowly during the final two phases. Thermalization of reacting ions on an approximate 3τii time scale accounts for only about 20% of the slow drop. Most of the slow drop seems to be caused by loss of ion energy from the mixing region (an ion heat pulse). [ABSTRACT FROM AUTHOR]