150 MeV pulse stretcher at Sendai

High duty cycle beams are inevitable for new electron accelerators due to the rapid development of nuclear physics. After considering several types of accelerators to deliver continuous beams, a conventional-type 1.2 GeV linac together with a pulse stretcher has been chosen at Sendai because of its existing technology and adaptabilities for various research. A 150 MeV pulse stretcher, a test ring for the proposed plan, has been completed at the end of the last year, and is now under test operation. The ring stores a pulsed beam whose energy range is from 100 MeV to 150 MeV and produces a continuous beam. It increases the duty cycle up to 90%. A pulsed beam is bent from the present linac beam line to the ring by two bending magnets (M9,M10). An extracted continuous beam returns to the initial direction towards the electron spectrometer. The circumference of the ring is 15.47 m. In the case of a two turn injection, a pulsed beam of 100 nsec is injected from the linac with the repetition rate of 300 pps and the peak current of 100 mA. The intensity of an extracted continuous beam is expected to be around 3 μA