Benchmarking of measurement and simulation of transverse rms-emittance growth

Abstract

Transverse emittance growth along the Alvarez drift tube linac (DTL) section is a major concern with respect to the preservation of beam quality of high current beams at the GSI UNILAC. In order to define measures to reduce this growth, appropriate tools to simulate the beam dynamics are indispensable. This paper is about the benchmarking of three beam dynamics simulation codes, i.e. DYNAMION, PARMILA, and PARTRAN against systematic measurements of beam emittances for different transverse phase advances along the DTL. Special emphasis is put on the modeling of the initial distribution for the simulations. The concept of rms equivalence is expanded from full intensity to fractions of less than 100% of the beam. The experimental setup, data reduction, preparation of the simulations, and the evaluation of the simulations are described. In the experiments and in the simulations, a minimum of the rms-emittance growth was observed at zero current phase advances of about 60. In general, good agreement was found between simulations and experiment for the mean values of horizontal and vertical emittances at the DTL exit.

Fourth order resonance of a high intensity linear accelerator

“…For instance, x ¼ 90 corresponds to x;o ¼ 109:4 and y ¼ 90 to y;o ¼ 105:6 . Simulations were done for the real UNILAC machine lattice and the same realistic 7.1 emA 40 Ar þ10 beam with 199 K macroparticles used for the previous benchmarking effort [14]. This input beam was obtained by reconstructing from the emittance measurement conducted before the UNILAC Tank 1.…”

Experimental Evidence of the 90° Stop Band in the GSI UNILAC

“…An important condition enabling the current study has been the successful termination of a benchmarking experiment at the UNILAC supported by the European Commission [9] in the years 2006-2008, which led to a visible improvement in mismatch control and confidence in diagnostics [10]. In the course of this benchmarking simulations it turned out that at the UNILAC a measurement of the 4th-order resonance might be feasible [11].…”

“…In order to provide for a 6d-matched injection into the periodically focusing DTL lattice, the setting of the matching section was adapted to each 0 individually. The matching procedure is described in detail in [10]. 0 was varied from 60 to 130 , and for each value of 0 horizontal and vertical phase space distributions were measured at the DTL exit.…”

Concept for controlled transverse emittance transfer within a linac ion beam

“…[mrad] more complex beam lines even with strong space charge [20,21]. The beam moments at the doublet entrance also can be measured if a pepper-pot device will be installed right behind the last singulet.…”

“…: ¼ cosðKLÞ; S : ¼ sinðKLÞ;: ¼ 2KL;(20) K from Eq (16),. and L as distance from the effective longitudinal field edge to the foil.…”