Liepeng Sun

Decomposition of metastable phase and formation of amorphous silicon in Pd77.5Au6Si16.5 alloy

chinese acad sci,int ctr mat phys,shenyang 110015,peoples r china.;sun, l (reprint author), chinese acad sci,inst phys,pob 603,beijing 100080,peoples r china

High power acceleration of an HSC type injector for cancer therapy

A hybrid single cavity（HSC） linac, which is formed by combining a radio frequency quadrupole（RFQ）and a drift tube（DT） structure into one interdigital-H（IH） cavity, is fabricated and assembled as a proof of principle injector for cancer therapy synchrotron, based on the culmination of several years of research. The HSC linac adopts a direct plasma injection scheme（DPIS）, which can inject a high intensity heavy ion beam produced by a laser ion source（LIS）. The input beam current of the HSC is designed to be 20 m A C6+ ions. According to numerical simulations, the HSC linac can accelerate a 6-m AC6+ beam, which meets the requirement of the needed particle number for cancer therapy（108-9ions/pulse）. The HSC injector with the DPIS method makes the existing multiturn injection system and stripping system unnecessary, and can also bring down the size of the beam pipe in existing synchrotron magnets, which could reduce the whole cost of synchrotron. The radio frequency（rf） measurements show excellent rf properties for the resonator, with a measured Q equal to 91% of the simulated value. AC6+ ion beam extracted from the LIS was used for the HSC commissioning. In beam testing, we found the measured beam parameters agreed with simulations. More details of the measurements and the results of the high power test are reported in this paper.A hybrid single cavity (HSC) linac, which is formed by combining a radio frequency quadrupole (RFQ) and a drift tube (DT) structure into one interdigital-H (IH) cavity, is fabricated and assembled as a proof of principle injector for cancer therapy synchrotron, based on the culmination of several years of research. The HSC linac adopts a direct plasma injection scheme (DPIS), which can inject a high intensity heavy ion beam produced by a laser ion source (LIS). The input beam current of the HSC is designed to be 20 mA C6+ ions. According to numerical simulations, the HSC linac can accelerate a 6-mA C6+beam, which meets the requirement of the needed particle number for cancer therapy (108–9 ions/pulse). The HSC injector with the DPIS method makes the existing multi-turn injection system and stripping system unnecessary, and can also bring down the size of the beam pipe in existing synchrotron magnets, which could reduce the whole cost of synchrotron. The radio frequency (rf) measurements show excellent rf properties for the resonator, with a measured Q equal to 91% of the simulated value. A C6+ ion beam extracted from the LIS was used for the HSC commissioning. In beam testing, we found the measured beam parameters agreed with simulations. More details of the measurements and the results of the high power test are reported in this paper.

Development and test of ADS injector II RFQ accelerator

The injector II RFQ accelerator of ADS is used to accelerate protons of 10 mA from 35 keV to 2.1 MeV. The cavity structure of the RFQ is the same as that of the SNS RFQ which has a square cross section, and it adopts π-mode rods to enhance the RF (radio frequency) stability of the cavity. Low power tests show that the flatness of the cavity is better than ±0.01 and the unloaded Q value is 13000. CW (continuous wave) working condition was realized after a long time conditioning of the cavity. Beam tests were conducted with a current of 10 mA in pulse mode and CW mode, respectively, and it indicates that the transmission efficiency is 95.3%, output energy is 2.165 MeV, energy spread is 1.9%, and the transverse and longitudinal emittances are all 0.33 πmm·mrad. ©, 2015, Atomic Energy Press. All right reserved.

Study of influence of radial matcher section end shape on RFQ cavity frequency

To investigate the feasibility of using a form cutter to machine the Radial Matcher Section (RMS) of the Radio Frequency Quadrupole (RFQ) for the Accelerator Driven System (ADS) project at Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS), the influence of RMS end shape on the RFQ cavity frequency is studied. The results indicate that using a form cutter to machine the RMS of an RFQ will indeed influence the cavity frequency. The RMS end shape will give more influence to a shorter RFQ cavity. For the 4.2 m ADS RFQ, the influence is negligible, which means that a form cutter can be used to machine the RMS.

Design study of the SSC-LINAC re-buncher

A re-buncher with spiral arms for a heavy ion linear accelerator named as SSC-LINAC at HIRFL (the heavy ion research facility of Lanzhou) has been constructed. The re-buncher, which is used for beam longitudinal modulation and matching between the RFQ and DTL, is designed to be operated in continuous wave (CW) mode at the Medium-Energy Beam-Transport (MEBT) line to maintain the beam intensity and quality. Because of the longitudinal space limitation, the re-buncher has to be very compact and will be built with four gaps. We determined the key parameters of the re-buncher cavity from the simulations using Microwave Studio software, such as the resonant frequency, the quality factor Q and the shunt impedance. The detailed design of a 53.667 MHz spiral cavity and measurement results of its prototype will be presented.

Preliminary study of a niobium quarter-wave prototype cavity for a heavy-ion superconducting linac

Superconducting quarter-wave resonators, due to their compactness and their convenient shape for tuning and coupling, are very attractive for low-β beam acceleration. In this paper, two types of cavities with different geometry have been numerically simulated: the first type with larger capacitive load in the beam line and the second type of lollipop-shape for 100 MHz, β=0.06 beams; then the relative electromagnetic parameters and geometric sizes have been compared. It is found that the second type, whose structural design is optimized with the conical stem and shaping drift-tube, can support the better accelerating performance. At the end of the paper, some structural deformation effects on frequency shifts and appropriate solutions have been discussed.