Low emittance 0.8A K(sup +) ion source for the LBL Induction Linac System Experiment (ILSE).

摘要

A high current injector for heavy ion fusion presently under construction at Lawrence Berkeley Laboratory requires large sources of up to 17 cm in diameter and total potassium ion current of 790 mA with a low normalized transverse emittance of less than 0.5 mm-mr. A 1 in. diameter hot alumina silicate (zeolite) source was fabricated and tested in the injector setup of SBTE, an existing facility at LBL. Initial measurements showed a maximum space charge limited ion current of 95 mA. The corresponding density of 19 mA/cm(sup 2) was limited by the source diode optics and not be the source emission. The density required for the high current injector is 4 mA/cm(sup 2). The normalized emittance was measured to be 0.06 mm-mrad, corresponding to a transverse temperature of 0.2 eV. Non-destructive life tests showed that the source can be operated under continuous operating conditions of the high current injector for more than a month (twenty eight-hour days, with 1 (mu)s long pulses at 1 Hz). D.C. destructive life tests showed that (approximately)30% of the total stored K can be ionized and extracted, allowing, in principle, for years of operation for the high current injector. Furthermore, we shall describe the extension of the fabricating technique to large diameter sources (up to 17 cm) and report on measured ion emission performance, measured surface temperature uniformity and heating power considerations.