Abstract
The production, storage and charge-changing reactions of low-energy, highly charged recoil neon ions in a Penning-type ion trap are described. Factors affecting the design and operating characteristics of the ion trap are discussed in detail. Charge transfer rate constants are obtained from measurement of the ion storage time constant and the pressure of the reactant gas. Application of ion storage techniques to the study of accelerator-produced target recoil ions represents a powerful new technique in the study of charge transfer to multi-charged ions. The Oak Ridge National Laboratory EN Tandem Van de Graaf accelerator was used as the source of (TURNEQ) 35 MeV Cl projectile ions to produce by collision with neon atoms electron-volt energy neon ions. Charge states ranging from +2e to +8e were stored for study. The recoil ions were produced from residual neon gas inside the Penning trap at pressures near 1 x 10('-7) torr. Trapped ions oscillate at characteristic frequencies dependent on their charge-to-mass ratio (i.e., q/m), and the detected signal strength for any particular q/m species is proportional to the number of ions. Ion storage time was dictated by charge-changing binary collisions with the neutral neon production gas. The population losses were characterized by simple exponential decays with characteristic lifetimes varying from 10's of msec to seconds. The measurement of mean ion storage time as a function of neutral gas pressure allowed the direct determination of total rate constants for charge transfer. The results for neon ions charge-changing with neutral neon gas, for charge states ranging from +3e to +6e, are 0.5, 3.4, 4.1, and 5.0 x 10('-9) cm('3)/sec, respectively for mean ion energies (TURNEQ) 1.5q eV. The trapping parameters in the Penning trap were varied to investigate the velocity of distribution of recoiling ions, and the results are presented. The mean trapped ion energy is estimated to be (TURNEQ) 0.5q eV, and the number of trapped ions with a particular charge saturates when an axial potential well 5 volts deep is maintained.
Burns, William Stee (1983). Charge transfer measurements on neon recoil ions in a penning trap. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -589342.