H. Idei

K. Ohkubo

M. Sato

S. Kubo

T. Shimozuma

Y. Takita

National Institute for Fusion Science (NIFS-Repository)

§ 13. Installation of the 1 06G Hz Gyrotron Kubo, S., Idei, H., OhkuboK., SatoM., Shimozuma T., Taki ta, Y. Electron cyclotron heating (ECH) in CHS is one of the standard methods to produce and heat the plasma. The experiments conducted so far are limited in the relatively low density region due to the presence of the cutoff. To get rid of this limitation, and to extend the low collisional regime up to the high density region, 1060Hz 500kW gyrotron is installed in the CHS hall. Table 1 shows the cutoff density for 53.2 GHz and 106.4 GHz in the cases of fundamental and second harmonic operation. B (T) 53.2 GHz 106.4 GHz 0.95 2nd harmonic 4th harmonic X-mode not efficient 1.81 X 1019 m-3 heating 1.9 fundamental 2nd harmonic O-m ode X-mode 3.61 X 1019 m-3 7.22 X 1019 m-3 Table 1. Cutoff density for fundamental and second harmonic heating in CHS. The specification of this gyrotron output is 500kW at 106.4 GHz+0.4 GHz with up to lOOms pulse. In order to operate this gyrotron with presently operating gyrotron in parallel, operating beam voltage is set to 80 kV. The acceptance test is performed with the power supply for 53.2 GHz Russian gyrotron, since almost all troubles related to the power supply are already fixed and now reliable. The most important adjustment is alignment of the axis of gyrotron and magnetic field produced by the cryomagnet. This alignment is done by using the alignment tube which has completely the same outer shape but the fluorescent material is coated on the inner surface of collector and viewing window is settled at the top of the collector. The adjustment is done by screws set at both top and bottom of the cryomagnet bore so that the fluorescent light be axisymmetric on the collector. Figure 1 shows the photograph taken during the acceptance test. The matching optics unit (MOU) 222 is installed between gyrotron output and dummy load to absorb the non Gaussian beam content which is not only unnecessary but rather harmful for the environment. Attained output power measured after the MOU with water dummy load was 540 kW during 100 ms pulse. The output beam parameter which is important for designing the new transmission system was measured by the temperature rise on the absorber target using IR camera. In the Fig. 2 are shown the horizontal and vertical spot sizes as a function of the distance from the output of the MOU. Using the Gauss beam parameters obtained from these data, new additional transmission line is designed to connect presently operating 53.2 GHz transmission system. water du Fig. 1. 1060Hz Oyrotron after being installed on the cryomagnet during the acceptance test. The water dummy load and matching optics unit--are connected. 9 0 t-8 0 -e 7 0 -.§. Q) 6 0 -~ (/) 50 -0 g. 4 0 -----20~~~~·~~~~~~~~~~~~ 0 500 1000 z(mm) 1500 2000 Fig. 2. Output beam evolution along beam axis from MOU of 1060Hz gyrotron. 

Installation of the 106G Hz Gyrotron

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