Linear envelope model for multicharge state linac

Abstract

The traditional linear envelope model is widely used in linac design and on-line tuning. However, for the simultaneous acceleration of multicharge states, the associated transfer matrix acts differently on each species with different charge to mass ratios and the traditional linear envelope model cannot be utilized. A direct way to handle multicharge state acceleration is by using multiparticle tracking, which can be high in model detail, but is typically lacking in computational efficiency to the extent where it is not suitable for on-line beam tuning of a linac. In this paper, a new approach of adapting a conventional linear envelope model to multicharge state acceleration is developed. The lattice of the proposed Facility for Rare Isotope Beams (FRIB) is used to test this technique in both the linac and the bend/folding segments of the machine. Results are benchmarked with the multiparticle tracking code IMPACT to both verify the accuracy of the model and clarify improvements in computational efficiency.

Heavy ion beam acceleration in the first three cryomodules at the Facility for Rare Isotope Beams at Michigan State University

“…The fitting and optimization capability of the simulation code, TRACK, was enhanced using a PYTHON environment. We found very good agreement of the beam rms parameters simulated by TRACK multiparticle code and FLAME "envelope" code [6] for single component ion beams. In most cases, the fitting and optimization of single-component ion beam rms parameters and beam optics settings were performed with the fast FLAME code.…”

Beam commissioning in the first superconducting segment of the Facility for Rare Isotope Beams

“…The cold section of the linac contains 39 SC solenoids, which were set to provide ∼60°phase advance of transverse betatron oscillations in each focusing period. Because of the irregular focusing period length, the exact values of phase advances are slightly different as follows from the computer simulations with the FLAME code [2] (see Fig. 2).…”

“…To avoid beam losses during the scans, a procedure was developed that includes an optimization of quadrupole fields in downstream quadrupoles to restore the beam matching. Beam rms envelopes during a typical quadrupole scan procedure calculated by the FLAME code [2] are shown in Fig. 3.…”

“…Since the lithium stripper is not yet available in the tunnel, thin carbon foils were utilized for charge stripping of 20.3 MeV=u Ne, Ar, Kr, and Xe ion beams in our experiments. By fitting with the FLAME code [2], a very small beam size, with a 0.5 mm rms radius, can be created on the stripping foil as shown in Fig. 8.…”

The fast linear accelerator modeling engine for FRIB online model service

“…, where σ is the whole beam RMS envelope size, and σ i is the RMS beam envelope size for each charge state. The method and the benchmark have been thoroughly discussed in [22].…”