B. Walch

Developments on the KSU-CRYEBIS, a user facility for low energy, highly charged ions

The KSU-CRYEBIS, a CRYogenic electron beam ion source, supplies experiments with low-energy, highly charged ions of numerous species. The supplied charge states cover the range from 1+ to 52+, with typical beam currents of a nA for low charge states and a few pA for the highest charge states. The ion energies cover the range from 0.3 to 165 keV per charge. This is an unusually broad range of final ion energies and hence requires an unusual dynamic ion transport system. This paper presents advances made with respect to the CRYEBIS ion beam transport, diagnostics, and identification. In addition, an update on the developments of ion beams with very high duty cycles is given.

Gain of windowless electron multipliers 226EM and EMI 9643/2B for highly charged Ta ions

The gain of windowless electron multipliers 226EM and EMI 9643/2B with BeCu dynodes was measured for Taq+ ions (12⩽q⩽49) with kinetic energies ranging from 8 to 164 keV/q. A Faraday cup was used as a standard ion-current detector. The comparison of the anode current of an electron multiplier (EM) with the Faraday cup current initiated by impact of ions indicates effects of their charge state as well as the velocity for response of both the EMs. The current gain of both the EMs has been found to monotonously increase with increasing charge state for ion energy per charge up to 24 keV/q but has a minimum for higher energy. The analog particle gain derived from the measured current gain increases with increasing charge state for all the accelerating voltages applied. The analog particle gain of 226EM increases with increasing ion energy per charge for q less than ∼27 but decreases with ion energy for higher q. For EMI 9643/2B the particle gain increases with increasing velocity up to charge state 49 where it...

Absolute measurements of characteristics of tantalum ion current from laser-produced plasma

The work presents results of absolute measurements of the energy distribution of ions, the ion current density, and the number of ions emitted from a tantalum laser-produced plasma. The results were obtained using two types of calibrated windowless electron multipliers. The number of ions with the individual charge state in the range z=37–42 was about 2.5×108 ions/cm2 and the maximum ion current density was about 0.5 mA/cm2 at the distance of 174 cm from the target. Moreover, the ion signals, the one measured by means of an ion collector and that reconstructed on the basis of measurements performed with an electrostatic ion energy analyzer, are also compared as well the influence of the secondary electron emission effect on the ion collector signal applied in the experiment is estimated.

Calibration of the Galileo microchannel plates with the Xe2+–Xe13+ and C2+–C6+ ions in the energy range from 0.5 to 150 keV/q (abstract)

The procedure of calibration of the detector assembly consisting of the two Galileo microchannel plates (MCPs) operated in a chevron configuration is described. The current gains and the analog particle gains of MCPs for Xe ions with charge states from q=3+ to q=13+ and C ions, with charge states from q=1+ to q=6+ and ion impact energies to charge state ratios from 0.5 to 150 keV/q have been measured. These results were compared to the earlier results obtained of calibration of this detector assembly with Xe ions with the charge states from q=7+ to q=43+ and ion impact energies to charge state ratios from 2 to 154 keV/q. We have shown the areas of ion parameters in which the secondary ion-electron emission coefficient of the investigated MCPs was dominated by kinetic or potential emission.

New improvements on the Kansas State University cryogenic electron beam ion source, a user facility for low energy, highly charged ions

The Kansas State University cryogenic electron beam ion source supplies low energy ion beams to users of the Department of Energy user facility for highly charged ions. The ions escape the source with an initial energy between 1.6 and 5 kV per charge and are analyzed in a 90° dipole magnet located on the high voltage platform. When leaving the platform the ions can be accelerated by up to 160 kV per charge or can be decelerated to about 20% of their initial energy, covering 2.5 orders of magnitude. We are in the process of adding another order of magnitude to the range of available ion energies as a newly installed lens allows for deceleration down to a very few percent of the initial energy. In addition we present the current microbunching and chopping system which has been substantially improved over the past 2 yr.