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Generation current margin is found to be limited not only by minimum current but also by maximum current. The generator maximum current I Gmax is measured for a 64 Kbit bubble memory chip with a 3 micron bubble. The chip temperature range was from 0 °C to 70 °C. A considerable loss of current margin is found at high current and high temperatures. This is considered to result from the generation of extra bubbles. I Gmax and its decay are observed to strongly depend on the shape of the generation pulse. A properly selected pulse shape increases I Gmax by 100 mA for a margin decay of less than -4 mA/decade and generate operation becomes possible in wide temperature range without compensation. Design combinations of generator and transfer gate or generator and replicator are proposed to give a more reliable generator port.

Performance of the LHD cryogenic system in the first year's operation was described making importance on the recovery process after the normal transition of the helical coils. During the excitation tests of the LHD superconducting coils up to 2.75 T, the normal zone propagation was observed in the helical coil and the emergency shut-off of the coil power supplies was carried out. 2,700 l of liquid helium evaporated from the helical coils. The coils and the helium refrigerator were separated automatically and the helium refrigerator could keep its steady state operation. After the pressure and flow rate of the recovery gas from the helical coils were settled down to the normal state, the coils were connected to the helium refrigerator and the cooling was restarted. The system could return to the steady state in which coil excitation is enabling, by only three and a half hours.