1
|
Liu JH, Li SJ, Li HY, Xie QF, Bai RH, Bo XK, Deng BH. A high-power long lifetime beam dump for the Thomson scattering diagnostic system in the XuanLong-50 experiment. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:093505. [PMID: 36182501 DOI: 10.1063/5.0100158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Accepted: 08/15/2022] [Indexed: 06/16/2023]
Abstract
The Energy iNNovation's XuanLong-50 is a spherical torus experiment with up to 10 s plasma operation duration. A 3 J/50 Hz pulsed laser is used in the Thomson scattering diagnostic system that is developed to measure the time evolutions of plasma electron temperature and density profiles. The expected laser pulse number is about 7.5 × 106/year with a power load of 150 W. To meet at least 1-year lifetime requirement, a Chevron type beam dump with polished molybdenum plates is designed and fabricated, which absorbs the laser beam energy in a 3D structure to reduce the laser fluence deposited on the material surface. To prevent the backscattered stray light from interfering with the Thomson scattering measurements, a 7.5 m beam path with folding mirrors is set between the beam dump and the plasma scattering volumes. Details of the beam dump design procedure including the laser beam profile control, multi-pulse laser damage threshold, heat dissipation, Zemax modeling, folding mirror selection, and beam path enclosure are presented together with the testing results.
Collapse
Affiliation(s)
- J H Liu
- Hebei Key Laboratory of Compact Fusion, Langfang 065001, China and ENN Science and Technology Development Co., Ltd., Langfang 065001, China
| | - S J Li
- Hebei Key Laboratory of Compact Fusion, Langfang 065001, China and ENN Science and Technology Development Co., Ltd., Langfang 065001, China
| | - H Y Li
- Hebei Key Laboratory of Compact Fusion, Langfang 065001, China and ENN Science and Technology Development Co., Ltd., Langfang 065001, China
| | - Q F Xie
- Hebei Key Laboratory of Compact Fusion, Langfang 065001, China and ENN Science and Technology Development Co., Ltd., Langfang 065001, China
| | - R H Bai
- Hebei Key Laboratory of Compact Fusion, Langfang 065001, China and ENN Science and Technology Development Co., Ltd., Langfang 065001, China
| | - X K Bo
- Hebei Key Laboratory of Compact Fusion, Langfang 065001, China and ENN Science and Technology Development Co., Ltd., Langfang 065001, China
| | - B H Deng
- Hebei Key Laboratory of Compact Fusion, Langfang 065001, China and ENN Science and Technology Development Co., Ltd., Langfang 065001, China
| |
Collapse
|
2
|
Feng D, Diallo A, Shneider MN. Two-color scattering for the measurement of neutrals at the edge of fusion devices. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:063515. [PMID: 34243505 DOI: 10.1063/5.0027481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 05/26/2021] [Indexed: 06/13/2023]
Abstract
Laser two-color scattering (TCS) is proposed to detect the neutral species in the edge of fusion devices, namely, tokamaks. TCS uses two wavelengths to probe both the laser Rayleigh scattering and Thomson scattering of the neutral-electron bath, with emphasis on neutral density measurements such as that of hydrogen and deuterium. Modeling of the Rayleigh scattering of tokamak neutral species under various plasma conditions (electron density and temperature) shows that, with an appropriate filtering of the Thomson signal and by going to ultraviolet-region wavelengths, identification of the Rayleigh signal can be achieved. Photon count and signal fractions are calculated in two test cases, one in the midplane region of the National Spherical Torus Experiment and one in the divertor region of DIII-D. An uncertainty analysis and discussion of the feasibility of the TCS diagnostic is also presented.
Collapse
Affiliation(s)
- David Feng
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Ahmed Diallo
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08544, USA
| | - Mikhail N Shneider
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
| |
Collapse
|
3
|
Optical Properties of Thomson Scattering Diagnostics Lower Window Glass under Laser Irradiation. MATERIALS 2021; 14:ma14112702. [PMID: 34063820 PMCID: PMC8196587 DOI: 10.3390/ma14112702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 05/15/2021] [Accepted: 05/18/2021] [Indexed: 11/17/2022]
Abstract
Tokamak diagnostic window glass is an indispensable optical medium in fusion research. The transmittance of the device affects the optical performance and accuracy of the diagnostic system. Especially, the window glass serves as the entrance of the light source while performing the sealing function for the active diagnosis method represented by Thomson scattering diagnostics. In this work, we studied the influence of the laser irradiation and tokamak discharge on the EAST (Experimental Advanced Superconducting Tokamak) Thomson scattering diagnostic borosilicate glass window. Using X-ray photoelectron spectroscopy (XPS) and Raman scattering, we found that carbon-based impurities in the device aggravated the film damage due to laser irradiation, reducing the performance of the coating of the glass. Besides, the laser and the various rays of tokamak discharge generated many point defects in the glass, increasing the light absorption of the glass. These two factors caused the glass transmittance to drop significantly (from 99.99% to 77.62%). In addition, the long-term laser irradiation primarily reduced the transmittance, while environmental rays had a minor impact on the same. This work provides valuable insights into the selection and effective use of glass in optics-based diagnostics.
Collapse
|
4
|
Liu CH, Huang Y, Hou ZP, Wang YQ, Feng Z, Zhai WY. Simulation of stray laser light of Thomson scattering systems in the HL-2M tokamak. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:043542. [PMID: 34243412 DOI: 10.1063/5.0043666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Accepted: 04/02/2021] [Indexed: 06/13/2023]
Abstract
Stray laser light is a serious problem that interrupts the measurement of electron temperature and density in Thomson scattering (TS) systems. This paper presents a ray-tracing simulation of stray laser light in HL-2M TS systems. A model including (i) a simplified laser-beam injection system, (ii) the scattered-light collection systems for central-point TS (CPTS) and edge TS (ETS), and (iii) the HL-2M vessel is built using the TracePro and CATIA software packages based on measurements of the bidirectional scattering distribution function at a wavelength of 532 nm. The simulation results show that no stray laser light reaches the injection surface of the collection lens of the CPTS system, and only a few stray laser rays of all the rays reaching the injection surface of the collection lens of the ETS system can be collected when the energy threshold per ray is 1 × 10-16. The stray laser rays that reach the scattered-light collection systems are mainly from the first and second parts of the slides of the beam dump, so decreasing the roughness of those parts could be effective in reducing the level of stray laser light.
Collapse
Affiliation(s)
- C H Liu
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Y Huang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z P Hou
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Y Q Wang
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - Z Feng
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| | - W Y Zhai
- Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041, China
| |
Collapse
|
5
|
Hu Q, Qiu Z, Hong J, Chen D. New light trap design for stray light reduction for a polarized scanning nephelometer. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2019; 90:035113. [PMID: 30927789 DOI: 10.1063/1.5055672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Accepted: 02/07/2019] [Indexed: 06/09/2023]
Abstract
Light scattering is an important tool for gathering information about the structure and origin of atmospheric aerosols. We build a polarized scanning nephelometer to measure the properties of aerosol particles. However, the accuracy of the backward-scattered light measurements is limited by stray forward-scattered light reflected back into the collection optics. We briefly analyze this stray light. A new form of light trap with multiple hollow cones is introduced to suppress backward-scattered stray light. To evaluate the effect of the light trap on suppressing stray light for our nephelometer, a simulation model with and without the light trap was analyzed. Our results show that without the light trap, the percentage of backward-scattered stray light can be more than 50% for some kinds of particles. With the light trap with multiple hollow cones, the percentage of stray light with a backward-scattered angle can be less than 0.7%, which remains stable over different angles. Our results indicate that this structure could be particularly suitable for a light trap with a very large aperture but limited space.
Collapse
Affiliation(s)
- Qiang Hu
- Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
| | - Zhenwei Qiu
- Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
| | - Jin Hong
- Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
| | - Dihu Chen
- Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
| |
Collapse
|