Development of Infrared Imaging Video Bolometer for the ADITYA Tokamak

Abstract

The Infrared Imaging Video Bolometer (IRVB) is one of the modern plasma imaging diagnostics which provides the measurement of the temporally as well as spatially resolved (2-D/3-D) power profile radiated from plasma devices. The technique has successfully been tested on a large size tokamak (JT-60U) and the same technique is for the first time being utilized for the medium size tokamak ADITYA (R = 75 cm, a = 25 cm, I p = 80 kA, T e (0) ∼ 350 eV, N e ∼ 1.5 × 10 13 cm 3 , B T = 0.7 T), where the plasma shot duration is ∼ 100 ms and radiated power brightness level is ∼ 2 W/cm 2 . The diagnostic is utilizing a 6.4 cm × 6.4 cm size and 2.5 µm thick, free standing Platinum foil. A square aperture 0.7 × 0.7 cm 2 of pinhole camera geometry can provide 9 × 9 bolometer pixel arrays (81 channels) and ∼ 7 cm of spatial resolution at plasma mid-plane with a 45• × 45• wide field of view. This wide field of view covers two semi-tangential views, on either side of the radial view in the tokamak along with a poloidal view. A medium wave infrared camera having 320 × 240 focal plane array, 200 Hz frame rate, noise equivalent temperature difference ∼ 20 mK is used and 10 ms of optimal temporal resolution is experimentally achieved. The present paper discusses the design, development and calibration of the system. The performance of the IRVB system for its time response is experimentally investigated and has also been reported here.

Design Considerations for an Infrared Imaging Video Bolometer for Observation of 3D Radiation Structures of Detached LHD Plasmas

“…The reflective cassegrain configuration on the other hand can be designed with two mirrors, each having a reflection > 95% and a few lens elements having a transmission ∼ 85% would result in a system having a throughput > 65%. The sensitivity of the IRVB is directly proportional to the transmission throughput of the optics [14]. The use of a reflective cassegrain configuration would result in an 85% more sensitive IRVB as compared to the refractive counterpart.…”