Electromagnetic and beam dynamics studies of a high current drift tube linac for LEHIPA

Abstract

We have performed detailed electromagnetic and beamdynamics studies of a 352.21 MHz drift-tube linac (DTL) that will acceleratea 30 mA CW proton beam from 3 to 20 MeV. At such high currents space chargeeffects are important, and therefore the effect of linear as well asnon-linear space charge has been studied (corresponding to uniform andGaussian initial beam distributions), in order to avoid space chargeinstabilities. To validate the electromagnetic simulations, a 1.2 m longprototype of the DTL was fabricated. RF measurements performed on theprototype were in good agreement with the simulations. A detailed simulationstudy of beam halos was also performed, which showed that beyond a currentof 10 mA, significant longitudinal beam halos are excited even for aperfectly matched beam, whereas for a mis-matched beam transverse beam halosare also excited. However, these do not lead to any beam loss within theDTL.