GB882366A - Improvements in ion sources - Google Patents

Abstract

882,366. Ion sources. COMMISSARIAT A L'ENERGIE ATOMIQUE. April 29, 1959 [May 3, 1958], No. 14653/59. Class 39(1) [Also in Group XL(c)] In an ion source for producing beams of ionised particles for use in particle accelerators, mass spectrometers and isotopic separation systems, comprising a glass tube 1 between the ends of which is maintained a high direct potential difference, the gas (e.g. hydrogen, deuterium, helium or nitrogen) or vapour (e.g. lithium or sodium) to be ionised enters the tube 1 at end 5 and tube 1 is situated along the axis of a cylindrical resonant cavity R, coupled to a high frequency source, in which there is a zone of intense high frequency field; near the vapour outlet end 24 of the tube 1 is an enlarged portion in the form of a flat bulb 2 of small volume located in the concentrated electric field. The resonant cavity comprises a central tubular conductor 7 and a cylindrical envelope 6 coaxial with tube 1, the tube 7 being capacitatively connected at three points to an oscillator (housed in casing 23) by means of a mica plate 36 situated between pairs of metal plates 12, 18 and 16 separating pairs of connecting wires 20, 37 and 22, 44 and 21, 43 respectively. Energisation of the resonant cavity produces a concentrated high frequency electric field between end 45 of conductor 7 and plate 8 so that gas or vapour located in the bulb will be highly ionised. In operation gas or vapour it fed into the device through inlet tube 5, it passes through a chamber T containing a quartz disc 30 which serves to increase the potential difference in the gaseous medium inside the ion source, and then passes through tube 1 into bulb region 2 where it becomes ionised and leaves the tube in the direction of arrow f. The end plate 8 of resonator is spaced from end wall 25 of the device by toroidal rubber joint 33, a similar joint 32 spaces the plate 8 from the flat bulb 2. A narrow passageway end plate 25 connects a pump P to the outlet end of the ion source and this is used to maintain a gas pressure of from 10<SP>-3</SP> to 10<SP>-4</SP> mm of mercury in the tube 1.