Speaker
Description
In the accelerator of negative ion source, electrons are easily generated via stripping loss of negative ions, background gas ionization, and secondary electron emission from electrodes. Under the effect of electric and magnetic fields, these electrons acquire high energy and exhibit a large divergence angle. Once ejected from the ion source, the energetic electrons can directly strike on the downstream beamline components, and especially exert a fatal impact on the thermally sensitive cryopumps. To address this issue, actively cooled electron dumps have been designed in devices such as JT-60U, LHD, and ITER to intercept the ejected electrons.
Based on a multi-physics coupling model of the negative ion source accelerator, the ejected electrons from the CRAFT dual-driver and quad-driver negative ion sources are characterized. Several sets of electron dumps were designed and installed in the CANBE, one of the test stands of the CRAFT NNBI test facility. In recent negative ion beam acceleration and neutralization experiments on CANBE, the water flow calorimeter (WFC) and infrared camera were used to measure the total deposited power and two-dimensional temperature distribution on the electron dumps, respectively. The thermal deposition characteristics were analyzed under different experimental conditions. Furthermore, the multi-physics coupling model was used to simulate ejected electron transport and deposition under realistic operating conditions, including beam energy, beam current, beam profile and gas pressure. Through a comparative analysis of the peak position and spread of thermal deposition between simulations and experiments, the model was further calibrated and optimized.
| Email address | yuwen.yang@ipp.ac.cn |
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| Visitor's Visa | yes |
| Classification | H- and D- sources for fusion, accelerators and other applications |