The spectral distribution of the 1s2s {1}S{0}-->1s{2} 1S0 two-photon decay of He-like tin was measured using a novel approach at the gas-jet target of the ESR storage ring. Relativistic collisions of Li-like projectiles with low-density gaseous matter have been exploited to selectively populate the desired 1s2s state. Compared to conventional techniques, this approach results in a substantial gain in statistical and systematic accuracy, which allowed us to achieve for the first time a sensitivity to relativistic effects on the two-photon decay spectral shape as well as to discriminate the measured spectrum for Sn from theoretical shapes for different elements along the He-isoelectronic sequence.

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Electron cyclotron resonance (ECR) ion sources produce low-energy, highly charged ions. A new 14.5 GHz ECR-based low-energy ion accelerator facility has been developed. The ion source involves a plasma chamber ('supernanogan') surrounded by permanent magnets that provide a suitable magnetic field. The entire assembly including the ion source and the analyzing magnet is mounted on a 400 kV deck. A LabVIEW-based command and control system has been developed for the beamline. In addition, wireless communication has been installed to operate the machine in high voltage. The charge state distribution of several ions (He, N 2 , O 2 , Ne, Ar and Xe) has been measured. For Ar and Xe, the maximum charge states measured were 16 + and 29 + , respectively. A direct x-ray measurement for plasma diagnostics was also initiated.

The x-ray bremsstrahlung spectrum emitted by the electron population in a 14.5 GHz ECR plasma source has been measured using a NaI(Tl) detector, and hence the electron temperature of the higher energy electron population in the plasma has been determined. The x-ray spectra for Ne and Ar gases have been systematically studied as a function of inlet gas pressure from 7 × 10(-7) mbar to 7 × 10(-5) mbar and for input microwave power ∼1 W to ∼300 W. At the highest input power and optimum pressure conditions, the end point bremsstrahlung energies are seen to reach ∼700 keV. The estimated electron temperatures (T(e)) were found to be in the range 20 keV-80 keV. The T(e) is found to be peaking at a pressure of 1 × 10(-5) mbar for both gases. The T(e) is seen to increase with increasing input power in the intermediate power region, i.e., between 100 and 200 W, but shows different behaviour for different gases in the low and high power regions. Both gases show very weak dependence of electron temperature on inlet gas pressure, but the trends in each gas are different.

EC-shell-ionization cross sections for Na, Mg, Al, Si, Cl, K, Ca, and Ti by protons in the energy range 0.5 -2.5 MeV have been measured using thin targets. Measurements have also been performed for thin targets of Fe, Ni, and Cu at a few energies. The energy range of protons for these targets corresponds to the reduced velocity {U1/U2&) range 0.2-1.1, in which the cross sections are very sensitive to the increased binding energy and the Coulomb-deflection effects. The measured ionization cross sections are compared with the predictions of the theory based on the perturbed-stationary-state approach including the Coulomb-deflection, energy-loss, and relativistic corrections. The data have been scaled according to various scaling laws to test the validity of the universal nature of the various Coulomb ionization theories based on the plane-wave Born approximation, the binary-encounter approximation, and the simplified semiclassical approximation model as given by La:gsgaard, Andersen, and Lund [in Proceed ings of the Tenth International Conference on the Physics ofElectronic and Atomic Collisions, edited by G. Watel (North-Holland, Amsterdam, 1978), p. 353]. The measured data have also been compared with the calculations of Montenegro and Siguad [J. Phys. B 18, 299 (1985)] based on the theory of lscr molecular-orbital ionization.