Consorzio RFX personnel has participated to collaborative experiments carried out on the MTF facility up to 500 kV (3-stage configuration), long-pulse (100 s), high current (190 A/m2) at the QST lab in Naka, Ibaraki, Japan. The beam optics simulation models previously prepared by Consorzio RFX (beam optics with SLACCAD, OPERA, vacuum pressure profile with AVOCADO and COMSOL, power loads on grids with EAMCC) have been benchmarked against the MTF experimental results (currents and thermal power deposited on grids and IR image on CFC target) also using the models developed during the previous NITS joint experiments. A good agreement was found concerning the beam optics and the evaluation of additional beamlet deflection due to asymmetry of the extracted current density at the meniscus. Considerable improvements were also obtained in the accuracy of the numerical model describing the gas flow and the gas pressure profile in the accelerator. However, a comparison of thermal power deposited on grids, measured by water calorimetry during the experiments, indicated that the power load due to stripped electrons (and maybe also due to negative ions), is still considerably underestimated in the numerical models. Additional interpretations have been developed to explain this power mismatch, however a fully consistent explanation has not been found so far. In preparation of the HV insulation tests at 1 MV in the MITCA vessel in vacuum and in low-pressure gas, discussions have been held with QST experts concerning the HV test setup, the measurement equipment and the protection of the HV bushing from overvoltages in case of electric breakdown between the HV electrodes and the Beam Source Vessel during tests. The plan developed by Consorzio RFX for the HV insulation tests in vacuum and low-pressure gas in MITICA has been presented to QST and a review meeting has been proposed for discussing the most effective options with ITER IO and experts.
Report on joint experimental activities and simulations at QST laboratories 13 May - 19 July 2019
Agostinetti P;
2019
Abstract
Consorzio RFX personnel has participated to collaborative experiments carried out on the MTF facility up to 500 kV (3-stage configuration), long-pulse (100 s), high current (190 A/m2) at the QST lab in Naka, Ibaraki, Japan. The beam optics simulation models previously prepared by Consorzio RFX (beam optics with SLACCAD, OPERA, vacuum pressure profile with AVOCADO and COMSOL, power loads on grids with EAMCC) have been benchmarked against the MTF experimental results (currents and thermal power deposited on grids and IR image on CFC target) also using the models developed during the previous NITS joint experiments. A good agreement was found concerning the beam optics and the evaluation of additional beamlet deflection due to asymmetry of the extracted current density at the meniscus. Considerable improvements were also obtained in the accuracy of the numerical model describing the gas flow and the gas pressure profile in the accelerator. However, a comparison of thermal power deposited on grids, measured by water calorimetry during the experiments, indicated that the power load due to stripped electrons (and maybe also due to negative ions), is still considerably underestimated in the numerical models. Additional interpretations have been developed to explain this power mismatch, however a fully consistent explanation has not been found so far. In preparation of the HV insulation tests at 1 MV in the MITCA vessel in vacuum and in low-pressure gas, discussions have been held with QST experts concerning the HV test setup, the measurement equipment and the protection of the HV bushing from overvoltages in case of electric breakdown between the HV electrodes and the Beam Source Vessel during tests. The plan developed by Consorzio RFX for the HV insulation tests in vacuum and low-pressure gas in MITICA has been presented to QST and a review meeting has been proposed for discussing the most effective options with ITER IO and experts.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
