Status of the 36 MHz linac cavities for the GSI high current injector

The new 1.4 MeV/u prestripper linac at GSI will provide intense ion beams to fill the synchrotron SIS to the space charge limit for all elements up to uranium. The design mass to charge ratio A/q is 65, the effective acceleration voltage of the 30 m long linac is up to 91 MV. The design beam current in emA is 0.25·A/q, i.e. 15 mA of U⁴⁺. This linac will replace the 27 MHz Unilac Wideroe section which was designed for A/q-values below 24. All cavities of the new linac are operated in the H₁₁₀-mode. The 9.2 m long IH-RFQ with an energy profile from 2.2 keV/u to 120 keV/u has been completed and RF tuned. RF power tests were performed successfully on 2 out of 10 tank modules. The drift tube linac consists of two 42 MV IH cavities. The `Combined Zero Degree Structure´ KONUS allows to accelerate the beam by a total number of 99 gaps with only 5 quadrupole triplet lenses for transverse focusing. The experience from the construction and from the RF tuning of all cavities is reported as well as the measured quality and shunt impedance values. The running in of the new prestripper linac is scheduled from April to September 1999