Optimized capture section for a muon accelerator front end

Abstract

In a muon accelerator complex, a target is bombarded by a multi-MW proton beam to produce pions, which decay into the muons which are thereafter bunched, cooled, and accelerated. The front end of the complex captures those pions, then manipulates their phase space, and that of the muons into which they decay, to maximize the number of muons within the acceptance of the downstream systems. The secondary pion beam produced at the target is captured by a high field target solenoid that tapers down to a constant field throughout the rest of the front end. In this study we enhance the useful muon flux by introducing a new design of the longitudinal profile of the solenoid field at, and downstream of, the target. We find that the useful muon flux exiting the front end is larger when the field at the target is higher, the distance over which the field tapers down is shorter, and the field at the end of the taper is higher. We describe how the solenoid field profile impacts the transverse and longitudinal phase space of the beam and thereby leads to these dependencies.

High field – low energy muon ionization cooling channel

“…The strength of the focusing field and the matching coils are optimized for each stage individually. At the initial stages where the transverse emittance is large ∼300 μm-rad we would like to avoid the longitudinal emittance growth from the amplitude dependent transit time effect [6]. The field integral is minimized to provide the required focusing for reducing the ϵ equ and match the length of the absorber.…”

“…It is desired to limit the field integral to avoid unnecessary increase in the bunch length due to transverselongitudinal coupling in the high field solenoids [6]. The on-axis field profile for each stage was optimized to meet these two requirements.…”

“…The design has five major components; the high power target for pion production [6], the rf bunching, the 6D cooling, the fast acceleration, and finally the injection into the collider ring. The muon collider design starts with the muon front end, consisting of the pion production target and the bunching channel [6][7][8][9] that yields bunch trains of both muon signs.…”

High intensity muon beam source for neutrino beam experiments

“…When protons hit the target material, the nucleon-nucleon interactions are responsible for pions production. The pion production is dominated by the single and double production processes given by (1). Later pions decay into muons and neutrinos.…”

“…Figs. 1 and 2 show schematic drawings of the target station and the front end [1,2]. Although each of the mentioned systems has a complex design which is optimized for the best performance with its own set of local objectives, the integration of all of them into one overall system requires a global optimization to ensure the effectiveness of the local objectives and overall performance.…”