InterdigitalH-mode drift-tube linac design with alternative phase focusing for muon linac

M Otani,R Kitamura,T Mibe,K Hasegawa,N Hayashizaki,Y Kondo,Y Iwashita,M Yoshida,N Saito,Y Iwata

doi:10.1103/physrevaccelbeams.19.040101

Abstract

We have developed an interdigital H-mode (IH) drift-tube linac (DTL) design with an alternative phase focusing (APF) scheme for a muon linac, in order to measure the anomalous magnetic moment and electric dipole moment (EDM) of muons at the Japan Proton Accelerator Research Complex (J-PARC). The IH-DTL accelerates muons from $\ensuremath{\beta}=v/c=0.08$ to 0.28 at an operational frequency of 324 MHz. The output beam emittances are calculated as $0.315\ensuremath{\pi}$ and $0.195\ensuremath{\pi}\text{ }\text{ }\mathrm{mm}\text{ }\mathrm{mrad}$ in the horizontal and vertical directions, respectively, which satisfies the experimental requirement.

Highlights

The design of an interdigital H-mode (IH) drift-tube linac (DTL) for the acceleration of low-velocity protons was first proposed in 1956 [1], and this concept has been studied throughout the intervening decades [2,3]
We describe the design of the alternating phase focusing (APF) IH-DTL for the Japan Proton Accelerator Research Complex (J-PARC) experiment in detail
The transverse emittance growths were calculated to be approximately 0.02π mm mrad, and are considered to be due to the nonlinear focusing generated by the APF scheme

Summary

INTRODUCTION

The design of an interdigital H-mode (IH) drift-tube linac (DTL) for the acceleration of low-velocity protons was first proposed in 1956 [1], and this concept has been studied throughout the intervening decades [2,3]. This paper describes the first attempt to adopt the APF IH-DTL for a low-emittance muon beam. We are developing a muon linac for the ðg − 2Þμ experiment at the Japan Proton Accelerator Research Complex (J-PARC) [13], in order to realize a low-emittance muon beam. One solution involves the use of an H-mode accelerating structure with permanent-magnet quadrupole (PMQ) magnets in the drift tubes [23] This setup provides sufficient transverse focusing, the production cost is increased. As a sufficient focusing force and a reduced production cost are desirable, APF is the dominant candidate; in this approach, the transverse and longitudinal focusing are achieved with the rf field only, and no additional focusing element is necessary.

APF IH-DTL DESIGN

Synchronous phase array optimization

IH cavity optimization

Particle tracking

RESULTS AND DISCUSSION

CONCLUSION