Improvement of Infrared Imaging Video Bolometer Systems in LHD

Plasma Phys. Control. Fusion

et al. 2018

Modeling of impurity-seeded plasma in Large Helical Device (LHD) is presented for the first time by using the three-dimensional transport code EMC3-EIRENE. High and low recycling coefficients for impurity ions are assumed to include low and high absorption rates on wall surfaces due to low and high chemical activity of neon and nitrogen, respectively. Radiation power measured by two bolometer systems and particle flux measured by divertor probes installed in multiple toroidal sections are utilized to determine impurity amount in the plasma. The toroidal uniformity and the non-uniformity of a divertor flux reduction observed experimentally for neon and nitrogen seeding, respectively, are reproduced by the model. Validations by measurements and deviations between the model and the experiment are discussed.

“…We used two bolometer systems at the upper port of the section 6.5, namely 6.5-U, and the outer port of the section 3, namely 3-O [29,30,31], as shown in Fig. 1(a).…”

Section: Configuration Of the Device And The Measurementsmentioning

confidence: 99%

Three-dimensional impurity transport modeling of neon-seeded and nitrogen-seeded LHD plasmas

Kawamura

Tanaka

Plasma Phys. Control. Fusion

et al. 2018

“…InfraRed imaging Video Bolometer (IRVB) is a useful diagnostic for multi-dimensional measurement of the plasma radiation. IRVB has been developed and installed in the Large Helical Device (LHD) [1][2][3]. Recently, IRVBs have been installed in KSTAR [4] and Alcator C-mod [5].…”

Section: Introductionmentioning

confidence: 99%

Neutron Shielding Design of Infrared Imaging Video Bolometer for LHD Deuterium Experiment

IEEE Trans. Plasma Sci.

Nishitani

Ogawa

et al. 2019

Self Cite

InfraRed imaging Video Bolometer (IRVB) is a powerful diagnostic for the plasma radiation measurement. Study on plasma radiation phenomena, e.g., plasma detachment is one of the crucial issues to realize a fusion reactor. In order to apply the IRVB to such a study, a shielding is required to protect an IR camera from neutron irradiation. In the Large Helical Device (LHD) deuterium experiment has started in 2017. Then, the shielding was designed using MCNP6 code with the threedimensional modelling of LHD. The guideline of the neutron flux for the design was determined by the operational experience in JT-60U tokamak and by the result of the irradiation in OKTAVIAN. The strong neutron flux due to the location close to the vacuum vessel and the influx through the lens hole were reduced sufficiently. The designed shielding was applied to the LHD deuterium experiments and the IRVB with the shielding could be operated successfully without any dead pixels in the neutron emission rate up to 3.3 × 10 15 n×s -1 , which is the maximum rate in the first experimental campaign, and in the total neutron emission of 3.6 × 10 18 n. These correspond to the neutron emission rate of 2.9 × 10 7 n×s -1 and the total neutron emission of 3.2 × 10 10 n at around the IR camera.

“…The IRVB has been developed in the Large Helical Device (LHD). 1,2 The IRVB has a combined structure of a pinhole camera with a metal foil absorber and an InfraRed (IR) camera. Plasma radiation through a pinhole is projected onto the foil absorber.…”

Section: Introductionmentioning

confidence: 99%

“…In LHD, the size of the platinum (Pt) absorber is 130 mm × 100 mm × 2.5 µm (thickness) and the absorber is divided into the bolometer pixel with the size of 10 mm × 10 mm in the numerical analysis. The IRVB has been installed in LHD, 1,2 JT-60U, 3 KSTAR, 4 HL-2A, 5 and Alcator C-mod. 6 The IRVB plays an important role in investigating the plasma radiation phenomena, i.e., plasma detachment and radiation collapse.…”

Section: Introductionmentioning

confidence: 99%

Improvement of infrared imaging video bolometer for application to deuterium experiment on the large helical device

Review of Scientific Instruments

Abe

Peterson

et al. 2018

An infrared imaging video bolometer was improved for application to a neutron environment in fusion plasma devices, i.e., the Large Helical Device (LHD). In order to calibrate the thermal characteristics of the activated foil absorber inside the plasma vacuum vessel, the remote-controlled in situ calibration system was improved with high-surface-flatness mirrors. Furthermore, the carbon coating method was improved by introducing a vacuum evaporation technique instead of the conventional spray technique to realize the coating on both sides of the absorber with reproducibility and uniformity. The optimal thickness of the coating was also determined. Owing to these coating improvements, the reproducibility of the effective emissivity on both sides especially was improved. Finally, the variation with the neutron irradiation of the thermal characteristics of the foil absorber was investigated. It was found that the effect was not significant for the total neutron emission of 3.6 × 10 18 on LHD.