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内容記述 |
The Linear IFMIF Prototype Accelerator (LIPAc) is a 125mA-CW deuteron accelerator facility to validate the key technologies for the design of the neutron source for the test of materials test to be used in fusion reactors. The study of the first acceleration from 100 keV to 5.0 MeV by the 9.8 m long RFQ in LIPAc is important to understand the formation dynamics of the charged particles from the continuous to the discrete structure, especially for future high-current machines. The RFQ-RF system consists of 8 feeds amplified up to 200 kW per line. Because one resonator is driven by multiple inputs, the White Rabbit system is used to realize their synchronization. During conditioning of the RFQ, we reached 80 percent of the design vane voltage (132 kV) in CW. The multipacting in the RF input couplers led an interruption of the operations. The beam commissioning is ongoing with a limitation on the maximum duty cycle to 10%. In preparation for the operation of the superconducting RF (SRF) Linac, we are studying the limitation to RFQ operational conditions. The beam simulations predict unacceptable losses in the SRF from 6 % less RFQ voltage than the design value. Thus, we studied the RFQ voltage dependency in the present beam commissioning before SRF Linac installation. According to the simulations, there are RFQ voltage dependencies of losses in the beam transport around 4m downstream from the RFQ exit (position-1) and further downstream, just after a bending magnet (position-2). The losses tendency measured using plastic scintillators agree with simulations. It was also possible to distinguish 1% differences of the cavity voltages in the energy measurements. Both methods suggest a miss-calibration of voltage of roughly 4%. As the discrepancy for the position-1 could come from the meandering motion of the initial transient part, gated measurement will be performed. |
