Performance with various diffraction gratings:

Outline Drawing

Select Publications

Simultaneous diagnostics of electron density and temperature in micoplasma reactor for scanning plasma etching

Abstract: Microplasma has been applied widely in micro fabrication. The diagnostics of microplasma generated in the scanning plasmas etching system is critical during the system operation. An experimental system is setup to investigate microplasma parameters of the dc-driven microplasmas reactor operating in CHF3 reactive gases at different gas pressure. The electron density and temperature was calculated from the optical emission spectral (OES) of the microplasmas based on Stark broadening of the Balmer lines of the hydrogen, Hβ and Hγ. The results of this paper may provide experimental verification for the optimized design of operative conditions of microplasmas reactor.

Hai Wang ; Sch. of Mech. & Automotive Eng., Anhui Polytech. Univ., Wuhu, China ; Zhou Xuan ; Li Han ; Wen Li

Development of two-grating spectrometer for the charge exchange spectroscopy system on KSTAR

Abstract: The charge exchange spectroscopy (CES) system on Korea Superconducting Tokamak Advanced Research (KSTAR) was installed last year and had been applied to measure the C VI ion temperature and rotation velocity profiles. The ion temperature and rotation velocity profiles had been estimated from the C VI 5290.5 Å (n = 8–7) charge-exchange spectrum signal measured by a Czerny-Turner type spectrometer and a thinned back-illuminated charge coupled device(CCD) camera. However, the Czerny-Turner type spectrometer used for the KSTAR CES system showed so low signal to noise ratio for KSTAR plasmas in the 2010 experimental campaign that the time resolution of the CES system had been limited to 100 ms due to the increased exposure time of the attached CCD camera. Then, new two-grating spectrometer had been developed in order to improve the time resolution of the CES system. The spectrometer consists of two gratings (1200 g/mm and 1800 g/mm each) with additive configuration, concave mirrors (f = 50 cm), and a cylindrical lens (f = 50 cm). The time resolution of the CES system increases by a factor of 2–4 with the two-grating spectrometer. The C VI ion temperature and rotation velocity profiles obtained by the two-grating spectrometer are compared to those by Czerny-Turner type spectrometer in this paper.

Hyungho Lee, Eun-ji Song, Young-dong Park, Soo-ghee Oh and Won-Ha Ko

Preliminary design of laser-induced breakdown spectroscopy for proto-Material Plasma Exposure eXperiment

Abstract: Laser-induced breakdown spectroscopy (LIBS) is a technique for measuring surface matter composition. LIBS is performed by focusing laser radiation onto a target surface, ablating the surface, forming a plasma, and analyzing the light produced. LIBS surface analysis is a possible diagnostic for characterizing plasma-facing materials in ITER. Oak Ridge National Laboratory has enabled the initial installation of a laser-induced breakdown spectroscopy diagnostic on the prototype Material-Plasma Exposure eXperiment (Proto-MPEX), which strives to mimic the conditions found at the surface of the ITER divertor. This paper will discuss the LIBS implementation on Proto-MPEX, preliminary design of the fiber optic LIBS collection probe, and the expected results.

G. Shaw, M. Z. Martin, R. Martin and T. M. Biewer

Line broadening in the neutral and ionized mercury spectra

Abstract: The neutral, singly, doubly and triply ionized mercury (Hg I–IV, respectively) spectral line shapes and line center positions have been investigated in the laboratory helium plasma at electron densities ranging between 9.3 × 1022 m−3 and 1.93 × 1023 m−3 and electron temperatures around 19,500 K, both interesting for astrophysics. The mercury (natural isotope composition) atoms were sputtered from the cylindrical amalgamated gold plates located in the homogenous part of the pulsed helium discharge operating at a pressure of 665 Pa in a flowing regime. The mercury spectral line profiles were recorded using the McPherson model 209 spectrograph and the Andor ICCD camera as the detection system. This research presents Stark broadening parameters, the width (W) and the shift (d), of one Hg I, 19 Hg II, 6 Hg III and 4 Hg IV lines, not investigated so far. Our experimental W values were compared with the data calculated applying various approaches. The shape and intensity of astrophysically important 398.4 nm Hg II spectral line was discussed taking into account the isotope shift, hyperfine structure and Penning effects. At the mentioned plasma parameters the Stark broadening is found to be a main line broadening mechanism of the lines (λ > 200 nm) in the Hg I–IV spectra.

M. Gavrilov, M. Skočić, M. Burger, S. Bukvić, , S. Djeniže

Measurement of the edge plasma rotation on J-TEXT tokamak

Abstract: A multi-channel high resolution spectrometer was developed for the measurement of the edge plasma rotation on J-TEXT tokamak. With the design of two opposite viewing directions, the poloidal and toroidal rotations can be measured simultaneously, and velocity accuracy is up to 1 km/s. The photon flux was enhanced by utilizing combined optical fiber. With this design, the time resolution reaches 3 ms. An assistant software “Spectra Assist” was developed for implementing the spectrometer control and data analysis automatically. A multi-channel monochromatic analyzer is designed to get the location of chosen ions simultaneously through the inversion analysis. Some preliminary experimental results about influence of plasma density, different magnetohydrodynamics behaviors, and applying of biased electrode are presented.

Z. F. Cheng, J. Luo, Z. J. Wang, Z. P. Zhang, X. L. Zhang, S. Y. Hou, C. Cheng and G. Zhuang

Latest Results from Proto-MPEX and the Future Plans for MPEX

Abstract: The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) is being used to qualify the plasma source and heating systems for the Material Plasma Exposure eXperiment (MPEX). The MPEX will address important and urgent research needs on plasma material interactions for future fusion reactors. In MPEX, plasma-facing components (nonirradiated and a priori neutron irradiated) will be exposed to plasma conditions as they are expected in future fusion reactors. The MPEX, a steady-state device enabled by superconducting magnets, will be able to break into new ground by assessing plasma-facing materials and components at an ion fluence level in the range of 1030 to 1031 m−2. To achieve the relevant plasma conditions, high-density plasmas (>4 × 1019 m−3) are produced with a high-power helicon source. The so-produced low-temperature helicon plasma is then additionally heated with waves in the ion cyclotron resonance frequency and electron cyclotron resonance frequency domains. Proto-MPEX has achieved all key parameters (source ne, source Te, source Ti, target Te, target Ti, target ion flux, and target heat flux) within a factor of 2 of the design requirements of MPEX, albeit not simultaneously. These parameters were achieved with a total installed heating power of 330 kW, which is less than half of the planned heating power in the MPEX (800 kW). An overview of the latest results from Proto-MPEX is given. These results are shown in relationship to the MPEX system goals. Remaining necessary research and development tasks are discussed. The MPEX is currently in the conceptual design phase. The status of the design and an overview of the system requirements are presented.

J. Rapp, A. Lumsdaine, C. J. Beers, T. M. Biewer, T. S. Bigelow, J. F. Caneses, J. B. O. Caughman, R. H. Goulding, N. Kafle, C. H. Lau, E. Lindquist, P. A. Piotrowicz, H. Ray,M. Showers & the MPEX Team

Rubidium D1 and D2 far wing line shapes induced by rare gases

Abstract: The far wing absorption cross-sections for the rubidium D1 (5 2S1/2–5 2P1/2) and D2 (5 2S1/2–5 2P3/2) transitions are observed at 10,000 Torr of 4He, 3He, Ne, Ar, Kr, and Xe with alkali densities of 3.3 × 1011 to 3.7 × 1015 molecules per cm3. Blue satellites are observed for the D2 transition, with shifts ranging from 782 cm−1 for helium to 319 cm−1 for Xe. The shifts vary inversely with product polarizability and the cross-section at the peak increases linearly with polarizablity. A red satellite is observed for the Xe broadened D1 line at 796.5 nm, consistent with a difference potential with well of 83 cm−1. The scaling of the cross-section with buffer gas pressure in the far wing suggest multi-body interactions contribute to these high pressure line shapes.

Christopher A Rice, Kevin Lapp, Anthony Rapp, Wooddy S.Miller, Glen P.Perram

Carbon nanotube generated electron beam produced plasmas

Abstract: A device using an energetic electron beam from a carbon nanotube electron emitter has been developed to generate plasmas at pressures near or below atmospheric. The low-pressure electron source region (10−6 mbar) and the higher pressure (up to 1 atmosphere) plasma generation region are separated by a 300 nm SiN x window/membrane. The energy of the electron beam is of the order of 10 kV with a current of 10 μA prior to passing through the window, with nearly 85% of the beam passing through the window to the plasma generation region with a 10% loss in energy. The device could be operated in one of two modes, closed or opened. Closed mode operation has been used to generate excimer emissions from XeI* and XeCl* at 253 nm and 308 nm, respectively, at pressures below atmospheric. Ambient air has been used in the open mode operation with and without a flow of argon or helium across the SiN x window. Optical emission spectroscopy revealed that the open mode operation yielded a variation of excited state species that was found to be dependent on the electron beam energy and the neutral gas flow in the reaction region.

N Masoud, K Martus, D Murnick

Hydronitrogen Molecular Assisted Recombination (HN-MAR) process in ammonia seeded deuterium plasmas

Abstract: Ammonia molecules, which will be formed in a nitrogen-seeded divertor plasma, show significant catalytic effects for volumetric recombination of hydrogen ions. This new Molecular Assisted Recombination (MAR), named the Hydronitrogen-MAR (HN-MAR), is based on the charge/ion exchange with NH3 and subsequent volumetric recombination of NH3+ and NH4+. In our PISCES-E RF plasma device, Ar is mixed with ND3/D2 gasses to realize a high electron density plasma [ne ∼ 1017 m−3] which allows us to see the importance of the dissociative recombination reactions which become comparable with wall loss reactions in our chamber. As increasing the plasma density, a calibrated Electrostatic Quadrupole Plasma analyzer measured dropping of ND4+ density fractions which can be explained reasonably by the existence of its dissociative recombination process in the plasma as a dominant reaction.

S.Abe, S. Chakraborty Thakur, R.P.Doerner, G.R.Tynan

Pre-launch Calibration of the Tiangong-2 Front-Azimuth Broadband Hyperspectrometer

Abstract: The Front-Azimuth Broadband Hyperspectrometer was launched on board the Tiangong-2 Space Laboratory on 15 Sep 2016 and had successfully measured spectral radiance of Earth limb atmosphere, to provide profiles of the volumetric concentration of ozone, nitrogen dioxide and other minor trace gases. In order to ensure the high accuracy and stability of data, The Front-Azimuth Broadband Hyperspectrometer was calibrated in laboratory and in orbit accurately. This paper mainly introduced the facility, method and results of the pre-launch calibration. Finally, the uncertainty of the calibration results was analyzed, and the results met the requirements of the data application.

Zhanfeng Li, Shurong Wang, Yu Huang, Qingjun Ma, Qingsheng Xue, Zhigang Li