Upgrading of a heavy ion 1 MeV RFQ accelerator

This paper presents new beam test results for O⁺ beam on high current Integral Split Ring Radio Frequency Quadruple (ISR RFQ) accelerator. After the upgrading, a new designed 2.45 GHz O⁺ ECR Ion Source can provide a beam with macro-pulse peak current of 4 mA at eh injection point behind a 15 mm diaphragm, whose O⁺ factor is 60%-80% varied with gas flow rate and the normalized rms emittance is less than 0.15 πmm·mrad. The accelerated O⁺ beam current goes up to 2 mA with the transmission of about 80% at 45 kW RF power with duty factor 1/6 (pulse duration of 1 ms and repetition frequency of 166 Hz). The upgraded RF power system includes low level RF pulse modulation amplifier, AGC, 3 W and 20 W preamplifiers, 1 kW driver and 30 kW final amplifier, which can output nearly 50 kW in pulsed mode. The vacuum has been improved, too. The upgraded 1 MeV ISR RFQ can be used as the beam injector of a new designed SFRFQ accelerating system, which is under the construction at Peking University, (authors)