A Very Fast Ramping Muon Synchrotron for a Neutrino Factory

Historically synchrotrons have provided economical particle acceleration. Here we explore a very fast ramping muon synchrotron [1] for a neutrino factory [2]. The accelerated muons are stored in a racetrack to produce neutrino beams (μ− → e− νe νμ or μ → e νe νμ). Neutrino oscillations [3] have been observed at experiments [4] such as Homestake, Super–Kamiokande, SNO, and KamLAND. Further exploration using a neutrino factory could reveal CP violation in the lepton sector. This synchrotron must accelerate muons from 4 to 20 GeV/c with moderate decay loss (τμ± = 2.2 μS). Because synchrotron radiation goes as m, muons radiate two billion times ( (105.7/.511) ) less power than electrons for a given ring diameter and lepton energy. Grain oriented silicon steel (3% Si) is used to provide a high magnetic field with a high μ to minimize magnetic energy (B/2μ) stored in the yoke. Magnetic energy stored in the gap is minimized by reducing its size. Cool muons [5] with low beam emittance allow this. The voltage needed to drive a magnet is −Ldi/dt. Voltage is minimized by shrinking the volume of stored energy to reduce the inductance, L. Acceleration to 4 GeV/c might feature fixed field dogbone arcs [6] to minimize muon decay loss. Fast ramping synchrotrons [6, 7] might also accelerate cold muons to higher energies for a μ μ− collider [8]. We form arcs with sequences of combined function cells within continuous long magnets, whose poles are alternately shaped to give focusing gradients of each sign. A cell has been simulated using SYNCH [9]. Gradients alternate from positive 20 T/m gradient (2.24 m long), to zero gradient (.4 m long) to negative 20 T/m gradient (2.24 m) to zero gradient (0.4 m), etc. Details are given in Table 1. It is proposed to use 5 such arc cells to form an arc segment. These segments are alternated with straight sections containing RF. The phase advance through one arc segment is 5 x 72 = 360. This being so, dispersion suppression between straights and arcs can be omitted. With no dispersion