Conceptual design of imaging bolometer for use of computed tomography in JT-60SA.

An InfraRed imaging Video Bolometer (IRVB) system in JT-60SA has been designed for the two-dimensional (2D) Computed Tomography (CT) analysis of radiation. To achieve complete viewing of the whole poloidal cross section for plasmas having a low aspect ratio, a new IRVB concept, which has two sets of pin-hole camera systems viewing two different directions, has been introduced. Fields of view of the IRVB have been successfully designed by moving apertures to be sufficient for CT use without installation in tangential ports. The size of the aperture, which determines the width of the sightline of the IRVB channels, has also been optimized with respect to the reconstruction error with well-established solvers of tomography. The optimization indicates that the 7 mm square aperture is the best for this system, and the CT measurement without this optimization can become degraded. A synthetic image using an estimated radiation profile shows that the signal to noise (S/N) ratio of the designed IRVB is large enough to identify the incident radiation power. The result indicates that the designed IRVB can be used for the 2D CT measurement of radiation in JT-60SA.