Response of the imaging cameras to hard radiation during JET operation

Huber, A.; Sergienko, G.; Kinna, D.; Huber, V.; Milocco, Alberto; Mercadier, Laurent; Balboa, I.; Conroy, S.; Cramp, S.; Kiptily, V.; Kruezi, U.; Lambertz, H.T.; Linsmeier, Ch.; Matthews, G. F.; Popovichev, S.; Mertens, Philippe; Silburn, S.; Zastrow, K.‐D.

doi:10.1016/j.fusengdes.2017.03.167

Cited by 13 publications

(8 citation statements)

References 9 publications

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“…For example, one of the specks appearing in FY 2017 (indicated by a blue arrow) disappeared at the beginning in FY2018. This phenomenon can be explained by the so called self-annealing which was reported in the CCD camera mounted in the JET tokamak [10]. In LHD, this self-annealing is found in some pixels even in Fig.…”

Section: Investigation Of the Influence Of The Cumulative Radiation Flux On The Image Sensormentioning

confidence: 80%

Radiation Resistant Camera System for Monitoring Deuterium Plasma Discharges in the Large Helical Device

Shoji

2020

Plasma and Fusion Research

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Radiation resistant camera system was constructed for monitoring deuterium plasma discharges in the Large Helical Device (LHD). This system has contributed to safe operation during two experimental campaigns without serious problems due to radiation (neutrons and gamma-rays). The cameras steadily functioned even in the plasma discharge with the maximum neutron emission rate in FY 2017, though some bright specks temporarily appeared on the images. The cameras have been installed in shield boxes which consist of lead boxes covered with 10% borated polyethylene blocks in all directions. For optimizing the design of the shield box, the radiation flux distribution was calculated by MCNP-6 code, which reveals the reduction of the radiation flux and the change of the energy spectra in the shield box. Thanks to the optimization, significant extension of the lifetime of the cameras has been realized. Investigation of the influence of the radiation on the CCD image sensor shows that the number of bright specks generally increases with the radiation flux to the camera, which also indicates that some bright specks disappear by the self-annealing process on the image sensor. This phenomenon also highly contributes to the further extension of the lifetime of the radiation resistant cameras.

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Section: Investigation Of the Influence Of The Cumulative Radiation Flux On The Image Sensormentioning

confidence: 80%

Radiation Resistant Camera System for Monitoring Deuterium Plasma Discharges in the Large Helical Device

Shoji

2020

Plasma and Fusion Research

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“…whereas digital cameras show a strong response to hard radiation and neutrons due to failure of the camera digital electronics [16]. The drawback of analogue cameras is the rather low sensitivity around 1 μm wavelength (<10%) for silicon-based detectors and the low dynamic range of the uncooled CCD sensor (8bit) [17].…”

Section: Protection Camerasmentioning

confidence: 99%

“…For reliable operation of the imaging system in the hostile electro magnetic environment of JET-ILW, the protection cameras must meet the following main criteria of an undisturbed operation of CCD sensors and electronics in the presence of a magnetic field and acceptable resistance to neutrons and gamma radiation. Video cameras should operate without replacement at least one year, withstanding a neutron fluence of ~2 × 10 12 n cm −2 [16]. In contrast to a digital video camera, an analogue one can fulfil these criteria easily because of its robustness and stable operation under harsh electromagnetic as well as radiation conditions-features which are particularly desirable in protection systems.…”

Section: Protection Camerasmentioning

confidence: 99%

Real-time protection of the JET ITER-like wall based on near infrared imaging diagnostic systems

et al. 2018

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In JET with ITER-like wall (JET-ILW), the first wall was changed to metallic materials (tungsten and beryllium) [1] which require a reliable protection system to avoid damage of the plasma-facing components (PFCs) due to beryllium melting or cracking of tungsten owing to thermal fatigue. To address this issue, a protection system with real time control, based on imaging diagnostics, has been implemented on JET-ILW in 2011.

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“…In addition, g-rays produced through the neutron capture are emitted from plasma facing components and laboratory structural materials, which also create a huge background noise on the CCD. [10][11][12] These noises lower the CCD capability of measuring a high-quality spectrum, e.g. significant decrease in signal-to-noise ratio.…”

Section: Introductionmentioning

confidence: 99%

Effect of neutron and γ-ray on charge-coupled device for vacuum/extreme ultraviolet spectroscopy in deuterium discharges of large helical device

Liu

Morita

Oishi

et al. 2018

Review of Scientific Instruments

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Charge-coupled device (CCD) is widely used as a detector of vacuum spectrometers in fusion devices. Recently, a deuterium plasma experiment has been initiated in Large Helical Device (LHD). Totally 3.7´10 18 neutrons have been yielded with energies of 2.45 MeV (D-D) and 14.1 MeV (D-T) during the deuterium experiment over four months. Meanwhile, g-rays are radiated from plasma facing components and laboratory structural materials in a wide energy range, i.e., 0.01-12.0 MeV, through the neutron capture. It is well known that these neutrons and g-rays bring serious problems to the CCD system. Then, several CCDs of vacuum ultraviolet (VUV) / extreme ultraviolet (EUV) / X-ray spectrometers installed at different locations on LHD for measurements of spectra and spatial profiles of impurity emission lines are examined to study the effect of neutrons and g-rays. An additional CCD placed in a special shielding box made of 10 cm thick polyethylene contained 10% boron and 1.5 cm thick lead is also used for the detailed analysis. As a result, it is found that the CCD has no damage in the present neutron yield of LHD, while the background noise integrated for all pixels of CCD largely increases, i.e., 1-3 ´ 10 8 counts/s. The data analysis of CCD in the shielding box shows that the background noise caused by the g-ray is smaller than that caused by the neutron, i.e., 41% from g-rays and 59% from neutrons. It is also found that the noise can be partly removed by an accumulation of CCD frames or software programming.

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Response of the imaging cameras to hard radiation during JET operation

Cited by 13 publications

References 9 publications

Radiation Resistant Camera System for Monitoring Deuterium Plasma Discharges in the Large Helical Device

Radiation Resistant Camera System for Monitoring Deuterium Plasma Discharges in the Large Helical Device

Real-time protection of the JET ITER-like wall based on near infrared imaging diagnostic systems

Effect of neutron and γ-ray on charge-coupled device for vacuum/extreme ultraviolet spectroscopy in deuterium discharges of large helical device

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