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A world-wide comparison of gauge block measurement by interferometry, decided on by the Comite Consultatif pour la Definition du Metre (CCDM), has been carried out. Four national metrology institutes, each representing one of the regional metrology organizations EUROMET, NORAMET, COOMET and APMP, measured a set of seven rectangular gauge blocks of steel with nominal lengths between 1 mm and 100 mm. This paper reports on the results of the comparison and draws conclusions with respect to the execution of future CCDM (now CCL) key comparisons.

A set of seven gauge blocks was circulated and calibrated by ten European national metrology institutes and one accredited laboratory. Measurements were made of central length, variation in length, flatness and, where possible, of the coefficient of thermal expansion. Agreement on the measurement results for the central length is excellent. It lies roughly within ±20 nm and seems to depend less on length than on the quality of the measurement faces, their wringing capability and the skill of the operator. The measurements of flatness and variation in length, on the other hand, differ substantially from one to another. A comparison of these results is difficult, however, since in practical measurements, the border zone defined by the standard is not quantitatively implemented. The few reported measurements of the thermal expansion coefficient are in good agreement. The comparison reflects the state of the art of gauge block calibration in Western European national metrology institutes. It also raises the question of whether the tolerances for flatness and variation in length can be checked interferometrically with reasonable effort.

The magnetic field component Bz generated in a magnetized plasma cylinder was measured at frequencies reaching from well below the first magnetoacoustic resonance up to the lower hybrid resonance. In this spectrum between 1 MHz and 100 MHz the first, second and even the third magnetoacoustic resonance have been identified. Investigation of the radial and axial dependence of Bz at different plasma parameters shows the typical field distribution for geometric resonances. In the upper part of the spectrum, between the third magnetoacoustic resonance and the lower hybrid resonance, a sharp minimum has been observed.

Magnetic field penetration into a cool, collisional, magnetized plasma has been investigated in Tormac V. Magnetic probe and laser interferometer studies reveal anomalous penetration of the applied toroidal field into a plasma with an initial parallel bias toroidal field. The applied poloidal field, however, formed a well‐defined magnetic front which was effective at sweeping up particles. Strong shear in the vacuum magnetic field does not inhibit the apparent decoupling of the applied toroidal field from the applied poloidal field.

Tormac (Toroidal Magnetic Cusp) is a plasma confinement concept combining the favorable MHD stability properties of a cusp geometry with the good particle confinement inherent to closed field geometry, A Tormac plasma has two regions: an interior region in which a toroidal bias or studding field is embedded, and an exterior or surface region confined by mirror trapping along open field lines. The combination of these two regions is expected to lead to a configuration having confinement substantially superior to that of a mirror. and to allow the plasma to be stable at high {beta}. The Tormac V experiment is an attempt to establish such a configuration and to investigate characteristic behavior of the Tormac plasma. In this paper we describe the Tormac concept. the Tormac V experimental set-up. and the results obtained.