We performed impact experiments to observe patterns in an ejecta curtain with targets consisting of small sand particles and large inclusions comparable to or smaller than the size of the projectiles. The spatial intensity distributions in the ejecta at early stages of crater formation depend on the size of the inclusions. Our numerical simulations of radially spreading particles with different sizes support this result. Based on the results, we proposed a procedure for evaluating the subsurface structures of celestial bodies from the images of ejecta curtains obtained from space-impact experiments.

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A fast-cycling induction synchrotron was demonstrated. Ions with extremely low energies and mass-tocharge ratios (A=Q) in the range from 2 to 10 were injected, captured by barrier voltages, and accelerated to the end of the acceleration cycle of 50 ms by flat pulse voltages generated by pulse transformers referred to as induction cells. Induction acceleration in a wide dynamic frequency range of 56 kHz to 1 MHz was also demonstrated. This accelerator is expected as the next generation of a heavy ion driver for cancer therapy, where a large scale injector is not required. A wide variety of ions for ion energy implantation experiments needing novel materials will be delivered from this compact circular accelerator.

Longitudinal bunch shapes in the KEK proton synchrotron were measured by a fast bunch-monitor system, which showed the rapid growth of the instability at the frequency of ϳ1 GHz and significant beam loss just after transition energy. Temporal evolution of the microwave instability is explained for the first time with a proton-klystron model. [S0031-9007(96)02288-0] PACS numbers: 29.27.Bd

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