Liangting Sun

Effects of magnetic configuration on hot electrons in highly charged ECR plasma

To investigate the hot electrons in highly charged electron cyclotron resonance (ECR) plasma, Bremsstrahlung radiations were measured on two ECR ion sources at the Institute of Modern Physics. Used as a comparative index of the mean energy of the hot electrons, a spectral temperature, Tspe, is derived through a linear fitting of the spectra in a semi-logarithmic representation. The influences of the external source parameters, especially the magnetic configuration, on the hot electrons are studied systematically. This study has experimentally demonstrated the importance of high microwave frequency and high magnetic field in the electron resonance heating to produce a high density of hot electrons, which is consistent with the empirical ECR scaling laws. The experimental results have again shown that a good compromise is needed between the ion extraction and the plasma confinement for an efficient production of highly charged ion beams. In addition, this investigation has shown that the correlation between the mean energy of the hot electrons and the magnetic field gradient at the ECR is well in agreement with the theoretical models.

The study of helicon plasma source

Helicon plasma source is known as efficient generator of uniform and high density plasma. A helicon plasma source was developed for investigation of plasma neutralization and plasma lens in the Institute of Modern Physics in China. In this paper, the characteristics of helicon plasma have been studied by using Langmuir four-probe and a high argon plasma density up to 3.9x10(13) cm(-3) have been achieved with the Nagoya type III antenna at the conditions of the magnetic intensity of 200 G, working gas pressure of 2.8x10(-3) Pa, and rf power of 1200 W with a frequency of 27.12 MHz. In the experiment, the important phenomena have been found: for a given magnetic induction intensity, the plasma density became greater with the increase in rf power and tended to saturation, and the helicon mode appeared at the rf power between 200 and 400 W.

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.