The measurement of impurity distribution in the divertor region of tokamaks is key to studying edge impurity transport.Therefore,a space-resolved vacuum-ultraviolet(VUV)spectrometer is designed to measure impurity emi...The measurement of impurity distribution in the divertor region of tokamaks is key to studying edge impurity transport.Therefore,a space-resolved vacuum-ultraviolet(VUV)spectrometer is designed to measure impurity emission in the divertor region on EAST.For good spectral resolution,an eagle-type VUV spectrometer with 1 m long focal length with spherical holograph grating is used in the system.For light collection,a collimating mirror is installed between the EAST plasma and the VUV spectrometer to extend the observing range to cover the upper divertor region.Two types of detectors,i.e.a back-illuminated charge-coupled device detector and a photomultiplier-tube detector,are adopted for the spectral measurement and high-frequency intensity measurement for feedback control,respectively.The angle between the entrance and exit optical axis is fixed at 15°.The detector can be moved along the exit axis to maintain a good focusing position when the wavelength is scanned by rotating the grating.The profile of impurity emissions is projected through the space-resolved slit,which is set horizontally.The spectrometer is equipped with two gratings with 2400 grooves/mm and2160 grooves/mm,respectively.The overall aberration of the system is reduced by accurate detector positioning.As a result,the total spectral broadening can be reduced to about 0.013 nm.The simulated performance of the system is found to satisfy the requirement of measurement of impurity emissions from the divertor area of the EAST tokamak.展开更多
We demonstrate that the methodology of frequency-resolved optical gating(FROG) is applicable to time-resolved reflection spectroscopy of a plasma mirror in the vacuum-ultraviolet(VUV) region. Our recent study [R. Itak...We demonstrate that the methodology of frequency-resolved optical gating(FROG) is applicable to time-resolved reflection spectroscopy of a plasma mirror in the vacuum-ultraviolet(VUV) region. Our recent study [R. Itakura et al. Opt. Express 23, 10914(2015)] has shown that a VUV waveform can be retrieved from a VUV reflection spectrogram of a plasma mirror formed on a fused silica(FS) surface by irradiation with an intense femtosecond laser pulse. Simultaneously, the increase in the reflectivity with respect to the Fresnel reflection of the unexcited FS surface can be obtained as a time-dependent reflectivity of the plasma mirror. In this study, we update the FROG analysis procedure using the least-square generalized projections algorithm. This procedure can reach convergence much faster than the previous one and has no aliasing problem. It is demonstrated that a significantly chirped VUV pulse as long as 1 ps can be precisely characterized.展开更多
基金the National Magnetic Confinement Fusion Science Program of China(Nos.2017YFE0301300,2019YFE03030002 and 2018YFE0303103)National Natural Science Foundation of China(No.12175278)+7 种基金Anhui Province Key Research and Development Program(No.202104a06020021)ASIPP Science and Research Grant(No.DSJJ-2020-02)Anhui Provincial Natural Science Foundation(No.1908085J01)Distinguished Young Scholar of Anhui Provincial Natural Science Foundation(No.2008085QA39)Instrument Developing Project of the Chinese Academy of Sciences(No.YJKYYQ20180013)the Comprehensive Research Facility for Fusion Technology Program of China(No.2018-000052-73-01-001228)the University Synergy Innovation Program of Anhui Province(No.GXXT-2021-029)CAS President’s International Fellowship Initiative(No.2022VMB0007)。
文摘The measurement of impurity distribution in the divertor region of tokamaks is key to studying edge impurity transport.Therefore,a space-resolved vacuum-ultraviolet(VUV)spectrometer is designed to measure impurity emission in the divertor region on EAST.For good spectral resolution,an eagle-type VUV spectrometer with 1 m long focal length with spherical holograph grating is used in the system.For light collection,a collimating mirror is installed between the EAST plasma and the VUV spectrometer to extend the observing range to cover the upper divertor region.Two types of detectors,i.e.a back-illuminated charge-coupled device detector and a photomultiplier-tube detector,are adopted for the spectral measurement and high-frequency intensity measurement for feedback control,respectively.The angle between the entrance and exit optical axis is fixed at 15°.The detector can be moved along the exit axis to maintain a good focusing position when the wavelength is scanned by rotating the grating.The profile of impurity emissions is projected through the space-resolved slit,which is set horizontally.The spectrometer is equipped with two gratings with 2400 grooves/mm and2160 grooves/mm,respectively.The overall aberration of the system is reduced by accurate detector positioning.As a result,the total spectral broadening can be reduced to about 0.013 nm.The simulated performance of the system is found to satisfy the requirement of measurement of impurity emissions from the divertor area of the EAST tokamak.
基金This work is supported by the National Natural Science Foundation of China(No.21973100 and No.22103090)the Program for Young Outstanding Scientists of Institute of Chemistry,Chinese Academy of Science,and Beijing National Laboratory for Molecular Sciences+1 种基金Hong Gao is also supported by the K.C.Wong Education FoundationPan Jiang is supported by the China Postdoctoral Science Foundation(No.2020TQ0324).
基金partly supported by the Consortium for Photon Science and Technology programmed by MEXT of JapanJSPS KAKENHI(Grant No.26288013)the Joint Usage/Research Program on Zero-Emission Energy Research,Institute of Advanced Energy,Kyoto University(Grant No.ZE26B-27)
文摘We demonstrate that the methodology of frequency-resolved optical gating(FROG) is applicable to time-resolved reflection spectroscopy of a plasma mirror in the vacuum-ultraviolet(VUV) region. Our recent study [R. Itakura et al. Opt. Express 23, 10914(2015)] has shown that a VUV waveform can be retrieved from a VUV reflection spectrogram of a plasma mirror formed on a fused silica(FS) surface by irradiation with an intense femtosecond laser pulse. Simultaneously, the increase in the reflectivity with respect to the Fresnel reflection of the unexcited FS surface can be obtained as a time-dependent reflectivity of the plasma mirror. In this study, we update the FROG analysis procedure using the least-square generalized projections algorithm. This procedure can reach convergence much faster than the previous one and has no aliasing problem. It is demonstrated that a significantly chirped VUV pulse as long as 1 ps can be precisely characterized.
