Thermal/structural analysis and frequency shift studies for the Spallation Neutron Source (SNS) drift tube linac

The drift tube linac of the Spallation Neutron Source accelerates the beam from 2.5 MeV to 20 MeV at the operating frequency of 402.5 MHz. This pulsed operating linac is about 9 meters long and consists of 84 cells with 83 permanent magnet quadrupole drift tubes. The DTL relies on the cooling system to zero out the frequency shift caused by RF heating on the cavity walls. Thermal expansion and frequency shift studies for three individual cells at a 3/spl times/10/sup 6/ V/m accelerating gradient are performed via numerical simulations to help guide the design of the cooling channels.