Research On ITER Soft X - Ray Camera

In this thesis the soft x-ray camera which will be mounted onto ITER tokamak was studied. Soft x-ray camera is a normal diagnostic in current tokamak device with its improving technique. As the ITER tokamak in which this camera will be operated i s high performance parameter designed.The camera will face harsh ITER physical env ironment. In this case, the design of this camera became very complicated. The back-ground of ITER tokamak and its physical environment were briefly reviewed to under stand the background of the design of ITER soft x-ray camera and to present its influe nce. Soft x-ray radiation and neutron radiation were also introduced. The author introd uced several soft x-ray cameras on other tokamak devices, the technique of which was significant for the design of ITER soft x-ray camera. The function of silicon semicon ductor photodiode was introduced which was chosen to be the detector of the camera. Two advanced detector GEM and PVD were also introduced because they were altern ative detectors for the upgrading of the soft x-ray camera performing during D-T phas e.Neutron shielding was one of the key points during camera design. Too much ne utron dose rate would damage the detector, while the neutron shielding beam path slot for neutron shielding would cause low signal intensity, low SRN, high-gain amplifier amplification, alignment difficulty and etc. Design and analysis were performed to sat isfy the requirements, and at last the camera structure got a balance between the consi derations above. And the structure could meet the neutron leakage requirement,meanwhile the detectors could can be operated during the whole D-D phase with out detector replacement. The structure analysis (gravity analysis, seismic analysis, el ectro-magnetic analysis and load combinations) claimed that in the worst condition ca se, even the maximum stress was still less than allowable stress. This means that the c amera will be usable and safe. The beam path slot will limit the signal intensity of the camera. The introduction of the beam width effect quantized quantizes such limit, wi th almost60%blocking rate of the external camera and nearly25%of the internal ca mera compared with the situation that the first wall does not block beam pathis under no shielding. Calculation claimed that signal intensity of the camera which is of order of10nA during ITER operation. Analysis results of the camera function showed that t he camera can be applied to measure not only MHD but also plasma radiation profile, impurity density profile, plasma position and shape as well as runaway electron.Camera cooling and detector usage were considered during the design and optim ization of the camera. During baking and operation of ITER, cooling of detectors mou nted in the internal camera was will be necessary. Heat load estimation of internal ca mera was conducted on for various heat-shielding methods, according to which, three cooling methods (conducting-cooling, water-cooling and air-cooling) were compared. The result showed that water coolingcan meet cooling requirements under all cases, a nd gas coolingcan meet cooling requirements only when the internal camera was well heat-shielded. Blind channel concept was applied in the detector usage design to dete ct the background and heat drift. And two channels overlapping of adjacent detector ar ray made the camera acquire allow for the radial position tolerance error of2.83mm r adial tolerance of for the internal camera and4mm perpendicular position tolerance o f4mm of for the external camera.Be window is also one of the key technique during the design. Itis difficult to iso late the vacuum using a thin Be foil which was will also be used forto beam filtering. Two set of Be window designs and testing results were introduced. As the result show ed, both designs using80μm Be foilenabled the and60mm×25mm optical area and en ableboth sides bear the pressure difference of one atmospheric pressure atmosphere.. Studies on calibration system, alignment structure and water cooling system wer e performed, to test the practicalities of the design. Testing results showed that these s ystems and structures can meet the function requirement of the camera. Calibration sy stem can be applied to select detectors. Alignment structure testing result showed that the machining precision meet the design requirement. Water cooling system on EAST up port worked well enough to keep the detector working in room temperature enviro nment.Physical observation of runaway electron during sawtooth crash on HT-7tokam ak and inversed inverted sawtooth on EAST tokamak partly provided the evidences fo r the practicability of the camera’s physical function design, especially the physical ob servation of runaway electron.