A bolometer system for the evaluation of the total of radiation power from the plasma and its spatial distribution will be prepared. The radiation power is also used for real-time feedback control of the plasma. In JT-60SA a 4-channel resistive bolometer system is applied to the radiation power measurement. Two types of bolometer heads are installed at P18 upper and horizontal port, and P16 lower diagnostic slit: one is the head with a thinner absorber for lower energy radiation from the plasma with the electron temperature <7.9 keV and the other is with a thicker absorber for higher energy radiation from the plasma with higher electron temperature <13.5 keV such as Scenario #2. The specifications of the bolometer system are summarized in Table 1.

Figure 1 (a) and (b) show viewing chords of the total radiation power and the radiation power distribution measurement for lower energy radiation, respectively. Total and distribution of the radiation power are independently evaluated by different detectors. The viewing chords are bundled into five detectors using multi-aperture type bolometer system (3 in horizontal port and 2 in diagnostic slit), as can be seen in the different colors in Figure 1 (a). The rest of detectors are divided into the radiation power distribution measurement as shown by each line in Figure 1 (b). Figure 1 (c) and (d) show viewing chords of the total radiation power and the radiation power distribution measurement for higher energy radiation, respectively.

12 bolometer channels (6 channels are for redundancy) which are specialized for an accurate measurement of the total radiated power with a method of weighted summation will be installed. The specialized bolometer channels are designed to minimize the error of the measurement of the total radiated power with few number of bolometer channels and viewing angle. The specialized bolometer channels are designed to bundle multiple sight lines into a bolometer detector. This specialization is based on uniform etendue by different aperture size among bundled lines of sight and uniform viewing volume per unit length of lines of sight by optimization of installation position. With this specialized bolometer, the total radiated power can be evaluated with less than 10 % error.