On the development of a 15 mA direct current H− multicusp source

Abstract

A 15 mA dc H Ϫ multicusp source has been developed for injection into a TR30 cyclotron. This source is also used with a 900 kV tandem accelerator to obtain 10 mA protons at 1.8 MeV. The program is an extension of the 5-7 mA dc H Ϫ cusp source developed at TRIUMF during [1989][1990]. Major efforts include the search for the optimal filament materials, shape, and location; comparison of cusp line confinement and magnetic filtering of electrons at the extraction region; optimization of extraction lense configuration; and upgrading of vacuum and power systems capability. The source is noncesiated and the maximum arc power available is only 5 kW. After the H Ϫ beams pass through an electron suppression grid and a 20 mm collimator, we obtained 15 mA with 0.66 mm mrad 4 rms normalized emittance. At this output the e/H ratio was about 4. The best normalized emittance occurs around 5-7 mA, having a value of 0.37 mm mrad. Further development in the near future is planned using cesium and multiple apertures in the hope of increasing dc H Ϫ currents to 30 mA while holding the normalized emittance below 0.75 mm mrad.

Photoelectron emission from metal surfaces induced by VUV-emission of filament driven hydrogen arc discharge plasma

“…The line-of-sight plasma volume was limited by the 9.5 mm diameter puller electrode aperture and the (6 mm / 8 mm diameter) collimator between the target and the plasma. The target materials used in this study are metals which are typically found in negative hydrogen ion sources as chamber materials (Al, Cu, SS) [8,9,10], filament materials (Ta) [7,11], plasma grid materials (Mo) [12] or so-called collar materials (SS, Mo) [13,14]. The effect of Al, Cu and SS wall materials and Ta covered walls on the volume production of negative hydrogen ions has been studied in [3,15,16].…”

Forty-five years with cesiated surface plasma sources

“…Control and diagnostics of cesiation was improved [51]. However, Cesium-less hot cathode discharge NIS with low energy and gas efficiency are used for internal and external cyclotron injection [52]. In high energy heavy ion tandem implanters are used charge exchange NIS with Mg targets [53].…”

Direct Production of 99mTc via 100Mo(p,2n) on Small Medical Cyclotrons

“…One way to increase the accelerated beam intensity with an internal PIG ion source is to increase the usage efficiency of the ions extracted from the ion source. Our simulation studies [44] done for benchmarking the existing design in preparation for a more radical change described in the next section, showed that the present Central Region is far from being fully optimized. There is considerable loss on different CR components during the first accelerating turn.…”