Interdigital accelerating H structure in the multicharged ion linac

Abstract

Two modifications of the interdigital accelerating H structure forming the basis for upgrading both the main and prestripper sections of the Kharkov multicharged ion linac (MILAC) are described. Possible application of this type of structure to heavy ion accelerator is discussed. It is shown that the use of the interdigital H structure in this particular case has enabled three major problems to be solved, namely: (i) to increase the operating wavelength from 2.1 m of the previously used Alvarez structure up to 6.3 m, (ii) to double the acceleration rate, and (iii) to increase the shunt impedance by 2–4 times. New methods and designs are described for tuning the cavities at an operating frequency and transforming the sinusoidal field distribution, peculiar to the H mode, into the homogeneously distributed field along the structure axis, with varying period lengths. Characteristics of the MILAC main and prestripper sections are given.

Interdigital Structures of Heavy Ions Linear Accelerators: Their Tuning, Beams Focusing and Use (Review)

“…4). It was essentially new approach to adjustment such interdigital H structures [5]. The further development of IHAS design for the purpose of MILAC new basic section making was the decision to establish a drift tube of one parity on the general plate bracket (comb) by means of short stems while drift tubes of other parity are fixed on adjusting stems with two additional stems (Fig.…”

“…Constructively they represent the quarter wave resonant vibrators formed on the ends of the plate bracket with the help undercuts it from the side of a resonator wall and shorten at the expense of capacity of drift tubes placed on them (Fig. 6) [8,9]. If adjustment current-carrying stems was local on each cell separately, but EREA tuning had global character.…”

“…The calculation strong-focusing variant PSS and modelling have shown that at a wave length of 12.6 m the quantity of drift tubes must be 37 (of them 18 with quadrupole lenses) in the resonator length 8,66 m and diameter 1.3 m. Thus in an initial part are used cells with alternating multiplicity of drift. The section is calculated on acceleration of ions with A/q = 22 and is structurally similar BS [12].…”

“…Reduction of all drift tubes diameters (unlike quadrupole focusings) which there should be 51 pieces in the resonator length 8.2 m and diameter 1.4 m, raises shunt resistance. New variant of the IHAS [13] in which odd drift tubes are located on longitudinal bearing electrodes, and the adjusting stems established symmetrically and uniformly on length, connect them with a lateral surface of the resonator is developed for this section. For increase in a range of adjustment and from constructive reasons it is offered to shift an axis of structure concerning a resonator axis.…”

“…The design of accelerating structure is similar to grid variant of the PSS MILAC, the same resonator length 6 m and diameter 1.5 m (quantity of drift tubes 36) was thus used. As the sizes of the resonator are already set, adjustment for the set frequency was spent, mainly, by means of additional stems [14].…”