Author: Li, L. B.
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TUA5 High Power Operation with SECRAL-II Ion Source 58
  • L.T. Sun, X. Fang, J.W. Guo, W. Huang, J.B. Li, L. B. Li, L. X. Li, W. Lu, H.Y. Ma, Z. Shen, Y. Yang, W.H. Zhang, X.Z. Zhang, H.W. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
  SECRAL-II ion source has been successfully developed with the experiences from SECRAL that is another superconducting ECR ion source in operation at IMP. Other than that, SECRAL-II has been intentionally optimized in structure so as to make it optimum for 28 GHz microwave operation. This ion source was available on the test bench in early 2016, and has been used for 28 GHz high microwave power commissioning and tests. With a maximum power 10 kW@28 GHz and 2 kW@18 GHz, very high microwave power density and dense hot plasma could be built in the 5-liter volume plasma chamber. Consequently very high current density ion beams of high charge states are achievable, which have already exceeded the performance the 24 GHz SECRAL had made couple of years ago. However, there is also the intractable issues stemmed from the hot dense electrons inside the plasma, such as plasma chamber cooling, dynamic heat load to the cryogenic system, and so on. This paper will present the recent results of SECRAL-II operated with high microwave power. The typical consequent issues during the high power course other than high intensity high charge state ion beam production will be discussed.  
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Perspective on High-Power Microwave Coupling in Gyrotron Frequency ECR Ion Sources  
  • J.W. Guo, X. Fang, Y.C. Feng, L. B. Li, L. X. Li, W. Lu, Z. Shen, L.T. Sun, W.H. Zhang, X.Z. Zhang, H.W. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
  Better understanding of microwave power coupling is a key issue to enhance the performance of an ECR ion source in terms of higher ion beam intensity yield and critical in the design of the next generation ECRIS. For this reason, we investigated the impact on highly charged ion production using different microwave coupling modes and waveguide calibers with superconducting ECR Ion Source SECRAL, and some very encouraging results were obtained. Based on the comparison of ion source performance working at different coupling schemes, analytical studies on microwave power launching efficiency and the characteristics of electric field power distribution inside the ECRIS chamber have been made and some preliminary conclusions will be given in this paper. This paper will also provide a 45 GHz microwave solution for the next generation ECR ion source FECR (a Fourth generation ECR ion source). After off-line tests of microwave transmission efficiency and mode purity, the 45 GHz gyrotron microwave system has been commissioned with SECRAL-II (a superconducting ECR ion source optimized for 28 GHz operation), and some preliminary results have been achieved and will be given in this paper.  
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Bremsstrahlung Measurements with SECRAL II Ion Source  
  • J.B. Li, J.W. Guo, L. B. Li, W. Lu, L.T. Sun, X.Z. Zhang, H.W. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
  To investigate the hot electrons in highly charged electron cyclotron resonance (ECR) plasma, the bremsstrahlung spectra for X-rays between 10 and 300 keV were measured from SECRAL- II, a third-generation ECRIS at the Institute of Modern Physics. We focused on how the external source parameters, especially the magnetic configuration affect the axial bremsstrahlung and the resulting spectral temperature Ts. The experimental results have shown that Ts appears to be dependent solely on the minimum magnetic field Bmin rather than (Bmin/BECR) and the microwave frequency '. In addition, this investigation has shown that Ts is not sensitive to HV, bias and gas pressure, which implies that a more careful consideration into the heating mechanism of ECRIS is needed.  
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