ABSOLUTELY CALIBRATED ATOMIC-HYDROGEN CELL FOR HIGH-ENERGY ATOMIC-COLLISIONS

A gaseous cell to study heavy-ion collisions with atomic hydrogen was made with the aim of investigating charge-exchange collisions in the i ntermediate-to-high velocity regime. The method of thermal-dissociatio n in a tungsten-tube furnace was used. The operating characteristics o f the partially dissociated hydrogen target, which depend not only on the design of the furnace but also on the collision-chamber geometry a nd pumping system, are described. The absolute calibration of the targ et cell was performed using double capture of C3+ at 1.1 MeV and elast ic scattering of the He-0 at 1.0 MeV in the mixture of H and H-2. At t emperatures of about 2600 K, a degree of dissociation of 80% was obtai ned with the tungsten filament lasting typically more than 300 h of op eration. (C) 1997 Elsevier Science B.V.