Closed divertor experiments on JFT-2M

In order to control divertor plasma independently on the main plasma, the divertor configuration of JFT-2M had been modified to be able to operate open to closed configuration. The neutral behavior in the divertor was measured by using the Penning gauge and divertor spectrometer. From this experiment, following results were obtained; 1. The electron density in the divertor plasma is a key for increasing the compression of the neutral particle on the divertor chamber. 2. New divertor spectrometer is operating now and observed the movement of the ionization front toward the main plasma. (author)