H. Matsuura

H. Takeda

H. Ueda

K. Hosoi

K. Ichimura

K. Nagaoka

M. Sakamoto

M. Shoji

Y. Nakashima

National Institute for Fusion Science (NIFS-Repository)

In the GAMMA 10 tandem mirror, high heat-ﬂuxgeneration experiments (E-divertor) with high-powerplasma heating systems have been started. In 2011FYexperiment, plasma heat ﬂux was estimated with calori-metric method based on Lumped-Heat-Capacity systemapproximation. Total heat load from plasma is estimatedas the product of heat content of the calorimeter target(see Fig. 1) and temperature jump at plasma discharge.But this method can not give us information on timeevolution of heat ﬂux. Moreover, sampling speed of therecorder for TC data of the calorimeter was too slow tocatch the transient heat pulse propagation in the target,and temperature peak value might be underestimated,since the thermal diﬀusion time of the target is the or-der of 1[s] for thermal diﬀusivity of probe tip material(Cu).For 2012FY experiment, a new calorimeter tar-get was designed and constructed. Figure 2 shows theschematic diﬀerence of two calorimeter head. While TCof the old sensor was connected to backside of the target,TC connection point of this new sensor is moved throughthe left tube shown in the ﬁgure to x = 2 mm positionapart from the irradiation surface and thermal diﬀusiontime is expected to be smaller than an old one by a factorof 25.Figure 3 shows comparison of raw signal of thesecalorimeters. Data recorder used here is GL900(GRAPHTEC Corporation), whose sampling interval is1[ms]. The TC signal of an old calorimeter sensor isfound to needs 30[s] or more to reach the maximum valueof the sensor temperature. The maximum of the new sen-sor shown in Fig. 2 appears at t < 1[s]. Both signal havelarge noise at the beginning of sampling.When TC signal during and just after plasma dis-charge is observed in detail, this noise can be categorizeinto two types1). One is a large positive spike whichappears during plasma discharge and disappear in noplasma production shot. So its origin is thought to beRF power device. Another noise is negative pulses seenaround t ∼ 700[ms] and observed even in only magneticcoil operation without plasma production. At this tim-ing, the coil current for conﬁnement magnetic ﬁeld is re-duced to zero. If the TC signal for no plasma dischargeis subtracted from those for normal discharge, this noiseis compensated fairly.Fig. 1: Constructed calorimeter head.Fig. 2: Schematic drawing of the old calorimeter head(left ﬁgure) and the new one (right).0 20000 4000001020Old sensorNew sensorGAMMA10 CM data(2012f)time[ms]Temp.[deg.]Fig. 3: Comparison of raw signal of calorimeters. TheTC signal of an old calorimeter sensor needs 30[s] toreach the maximum value. The maximum of the newsensor shown in Fig. 2 appears at t < 1[s].1) H.Matsuura et al.: OS2012/PMIF2012, (Tsukuba,2011 Aug.) O-19.516§17. Experimental Study on Heat Flux of Divertor Plasma (Measurement of Sheath Heat Flux on the Surface of Gamma 10 Divertor Plates)Matsuura, H. (Osaka Pref. Univ.), Nakashima, Y.,  Sakamoto, M., Hosoi, K., Takeda, H.,  Ichimura, K., Ueda, H. (Tsukuba Univ.),  Nagaoka, K., Shoji, M.

Experimental Study on Heat Flux of Divertor Plasma (Measurement of Sheath Heat Flux on the Surface of Gamma 10 Divertor Plates)

Experimental Study on Heat Flux of Divertor Plasma (Measurement of Sheath Heat Flux on the Surface of Gamma 10 Divertor Plates)

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