A NEW UHV SETUP FOR INVESTIGATIONS OF NARROW NUCLEAR RESONANCES WITH HIGH-ENERGY RESOLUTION ION-BEAMS

A cryogenic target system has been built to study yield curves of narr ow nuclear resonances. The crucial part of the UHV set-up is a liquid helium cooled sample holder mounted on a goniometer, allowing the use of gas and solid targets in the temperature range 10-600 K. Particle d etectors and gamma-ray detectors can be installed in close geometry to the target to achieve large solid angles. With this target system nuc lear resonances in Ne-21(p,gamma)Na-22 and O-18(p,alpha)N-15 have been investigated with high ion beam energy resolution. Effects of electro nic excitation processes are clearly visible in the shape of yield cur ves of the 272 keV resonance in Ne-21(p,gamma)Na-22 obtained at a temp erature of approximate to 12 K. The width of the 151 keV resonance in O-18(p,alpha)N-15 was measured, where the data are significantly influ enced by interference effects.