Muon Transport Channels with Longitudinal Magnetic Field

The Neutrino Factory (NF) concept includes several channels that treat muon beam to allow its capture into the accelerating part of the complex [1]. There must be a "drift" channel where pions decay generating muons. In this channel a correlation develops between muon energy and its position (mass separation). Due to a very high beam emittance and energy spread after the target, a high magnetic field and large channel bore are required to have a satisfactory beam transport efficiency. There must be a "phase rotation" channel, where the correlation developed in the "drift" channel is used to reduce muon beam energy spread. Electrical field of low-frequency RF cavities or induction sections accelerates or decelerates different parts of the beam changing its energy distribution. Both RF and LIA channels require longitudinal magnetic fields similar to that in the drift channel. Because the action principle of the induction section is similar to that of a Linear Induction Accelerator (LIA), we will call the channel with the induction sections a LIA channel. After the “phase rotation” channels reduce the energy spread, an additional "cooling" channel is needed to reduce the beam emittance. The ionizationcooling scheme is not finalized yet, but it is developed to the extent that allows a preliminary analysis of the channel magnetic system. One of the approaches to the cooling system makes use of an alternating magnetic field of high strength. This report discusses main features of the magnetic systems for the decay, phase rotating, and cooling channels of the NF version developed at FNAL.