GB1482433A - Standing-wave linear accelerator - Google Patents

Abstract

1482433 Linear particle accelerators VARIAN ASSOCIATES Inc 28 Nov 1974 [30 Nov 1973] 51684/74 Heading HID A standing wave charged particle acceleration formed by a sequence of accelerating cavities 11 to 21 having aligned beam passage apertures 51 to 62, has its cavities divided into sets such that successive cavities of a set are non-adjacent, being separated by a cavity of a different set, and are coupled by coupling cavities 21 to 29 displaced from the beam path, one cavity of each set being driven by a source of electromagnetic wave energy; the arrangement permits control of the relative phase of the wave in adjacent acvities while dispensing with the use of drift tubes. In the accelerator shown, the accelerating cavities are divided into two sets, coupled by cavities 21, 23 ... 29 and 22, 24 ... 28 respectively, arranged in orthogonal planes about the beam axis 10. Magnetic coupling apertures 62, 62<SP>1</SP>... 71, 711 may be provided to compensate for the coupling which occurs between adjacent accelerating cavities via the beam passage apertures 51 ... 62, although for electrons the latter may be sufficiently small to obviate the need for compensation. Internally projecting posts in the coupling cavities are dimensioned to ensure that the coupling cavities and the accelerating cavities have substantially the same resonant frequency. The two sets of accelerating cavities may, as shown, be independently energized at respectively opposite ends of the structure, not necessarily at the same frequency, or only one set may be fed from an external source, the wave being thereafter fed to the other set with a suitable phase shift produced by a dielectric element (126, Fig. 5, not shown). The beam passage openings 51 to 62 have rounded edges to reduce the field gradient and risk of breakdown. The energy of the output beam may be varied by adjustment of the relative phase of the waves in the two sets of accelerating cavities.