Design of 7 MeV drift tube linac as injector of proton accelerator for cancer therapy
A 324 MHz drift-tube linac(DTL) is designed for proton cancer therapy.The design demands low power dissipation and short tank.The DTL accelerates beam from 2.5 MeV to 7 MeV,with RF power of 265 kW and total length of 1.9 m.The DTL uses permanent-quadrupole magnet(PQM) inside the drift tubes arranged in an FODO lattice.A new matching method is designed.In stead of the traditional beam transport line,the first four cells in DTL are designed as matching section.It causes the beam ellipse from radio-frequency quadrupole linac(RFQ) to satisfy conditions specified by the DTL periodic structure.The dynamics simulation was performed with PARMILA,and almost no emittance growth has been found.