Liquid hydrogen and helium targets for radioisotope beams at RIKEN

Compact liquid hydrogen, deuterium, and helium targets were constructed for radioisotope beam experiments at RIKEN. Hydrogen, deuterium, or helium gas is liquefied by a Gifford-McMahon cycle refrigerator instead of being supplied as a cryogenic liquid. The liquefied gas is accumulated in a target cell placed at the center of a γ-ray detector array. The targets were operated stably in several experiments.