First results from the Thomson scattering diagnostic on proto-MPEX

Biewer, T. M.; Meitner, S. J.; Rapp, J.; Ray, H.; Shaw, G.C.

doi:10.1063/1.4959163

Cited by 15 publications

(5 citation statements)

References 5 publications

(3 reference statements)

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“…An expansive diagnostic suite is installed on Proto-MPEX, providing plasma measurements along the axis of the machine. Diagnostics include infrared (IR) cameras [10], thermocouples (TCs), fluoroptic probes (FPs), double Langmuir probes (LPs) [11], Mach probes (MPs), Thomson scattering (TS) [12,13], and filterscopes [14,15].…”

Section: Experimental Apparatusmentioning

confidence: 99%

Power accounting of plasma discharges in the linear device Proto-MPEX

Showers

Piotrowicz

Beers

et al. 2018

Plasma Phys. Control. Fusion

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Plasma material interaction (PMI) studies are crucial to the successful development of future fusion reactors. Prototype Material Plasma Exposure eXperiment (Proto-MPEX) is a prototype design for the MPEX, a steady-state linear device being developed to study PMI. The primary purpose of Proto-MPEX is developing the plasma heating source concepts for MPEX. A power accounting study of Proto-MPEX works to identify machine operating parameters that could improve its performance, thereby increasing its PMI research capabilities, potentially impacting the MPEX design concept. To build a comprehensive power balance, an analysis of the helicon region has been performed implementing a diagnostic suite and software modeling to identify mechanisms and locations of heat loss from the main plasma. Of the 106.3 kW of input power, up to 90.5% of the power has been accounted for in the helicon region. When the analysis was extended to encompass the device to its end plates, 49.2% of the input power was accounted for and verified diagnostically. Areas requiring further diagnostic analysis are identified. The required improvements will be implemented in future work. The data acquisition and analysis processes will be streamlined to form a working model for future power balance studies of Proto-MPEX.

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Section: Experimental Apparatusmentioning

confidence: 99%

Power accounting of plasma discharges in the linear device Proto-MPEX

Showers

Piotrowicz

Beers

et al. 2018

Plasma Phys. Control. Fusion

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“…Thomson scattering (TS) is a well-established technique to measure electron density and temperature in plasmas, including those sustained by helicon waves (Seo et al 2013;Biewer & Shaw 2014;Biewer et al 2016;Bozhenkov et al 2017). It is routinely used in tokamak research to obtain electron density and temperature profiles in the plasma core where the density reaches approximately 2 × 10 20 m −3 and the temperature several keV (Pasqualotto et al 2004;Pitzschke 2011).…”

Section: Introductionmentioning

confidence: 99%

Application of Thomson scattering to helicon plasma sources

et al. 2020

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The possibility of performing electron density and temperature measurements in a high power helicon plasma is a crucial issue in the framework of the AWAKE (Advanced WAKefield Experiment) project, which demonstrates acceleration of particles using $\text{GeV}~\text{m}^{-1}$ electric fields in plasmas. For AWAKE, a helicon is currently envisaged as a candidate plasma source due to its capability for low electron and ion temperature, high electron density and production of an elongated plasma column. A plasma diagnostic to accurately determine the electron density in AWAKE regimes would be a valuable supporting tool. A demonstration Thomson scattering (TS) diagnostic was installed and successfully tested on the resonant antenna ion device (RAID) at the Swiss Plasma Center of Ecole Polytechnique Fédérale de Lausanne. RAID produces a helicon plasma column with characteristics similar to those of the AWAKE helicon source, and is therefore an optimal testbed for application to the AWAKE device. The spectrometer employed in RAID is based on polychromators which collect the light scattered by plasma electrons in spectrally filtered wavelength regions. Results from TS on RAID demonstrate conditions of electron density and temperature respectively of $n_{e}=1.10\,(\pm 0.19)\times 10^{19}~\text{m}^{-3}$ and $T_{e}=2.3\,(\pm 0.6)~\text{eV}$ in a steady-state discharge in an Ar plasma with 5 kW of RF power. If the same polychromator system is used for AWAKE, where the electron density attained is $2\times 10^{20}~\text{m}^{-3}$ , the contribution to measurement error due to coherent scattering is ${\sim}2.5\,\%$ . Presented here are details of the TS diagnostic and the first tests in RAID, and the expectations for the system when employed on the AWAKE device.

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“…Double Langmuir Probes are being used to measure n e and T e at different axial locations (Probe A, B, C in figure 3). Thomson scattering [14] is used to determine the plasma parameters in front of the target. IR thermography is used at the target and dump plate to determine the power fluxes to the target [15].…”

Section: Results From the Prototype-materials Plasma Exposure Experim...mentioning

confidence: 99%

Developing the science and technology for the Material Plasma Exposure eXperiment

et al. 2017

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Linear plasma generators are cost effective facilities to simulate divertor plasma conditions of present and future fusion reactors. They are used to address important R&D gaps in the science of plasma material interactions and towards viable plasma facing components for fusion reactors. Next generation plasma generators have to be able to access the plasma conditions expected on the divertor targets in ITER and future devices. The steady-state linear plasma device MPEX will address this regime with electron temperatures of 1 -10 eV and electron densities of 10 21 -10 20 m -3 . The resulting heat fluxes are about 10 MW/m 2 . MPEX is designed to deliver those plasma conditions with a novel Radio Frequency plasma source able to produce high density plasmas and heat electron and ions separately with Electron Bernstein Wave (EBW) heating and Ion Cyclotron Resonance Heating (ICRH) with a total installed power of 800 kW. The linear device Proto-MPEX, forerunner of MPEX consisting of 12 water-cooled copper coils, is operational since May 2014. Its helicon antenna (100 kW, 13.56 MHz) and EC heating systems (200 kW, 28 GHz) have been commissioned. The operational space was expanded in the last year considerably. 12 MW/m 2 was delivered on target. Furthermore electron temperatures of about 20 eV have been achieved in combined helicon and ECH/EBW heating schemes at low electron densities. Overdense heating with Electron Bernstein Waves was achieved at low heating powers. The operational space of the density production by the helicon antenna was pushed up to 8 x 10 19 m -3 at high magnetic fields of ~1.0 T at the target. Proto-MPEX has been prepared to allow for first material sample exposures, albeit for short pulse duration. The experimental results from Proto-MPEX will be used for code validation to enable predictions of the source and heating performance for MPEX. MPEX, in its last phase, will be capable to expose neutron-irradiated samples. In this concept, targets will be irradiated in ORNL's High Flux Isotope Reactor and then subsequently exposed to fusion reactor relevant plasmas in MPEX. The current state of the MPEX pre-conceptual design and unique technologies already developed, including the concept of handling irradiated samples, are presented.

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First results from the Thomson scattering diagnostic on proto-MPEX

Cited by 15 publications

References 5 publications

Power accounting of plasma discharges in the linear device Proto-MPEX

Power accounting of plasma discharges in the linear device Proto-MPEX

Application of Thomson scattering to helicon plasma sources

Developing the science and technology for the Material Plasma Exposure eXperiment

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