Temperature and Lifetime Measurements in the SSX Wind Tunnel

Kaur, Manjit; Gelber, Kaitlin; Light, Adam; Brown, M. R.

doi:10.3390/plasma1020020

Cited by 6 publications

(1 citation statement)

References 24 publications

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“…The electron temperature (T e ) measured using vacuum ultraviolet (VUV) spectroscopy is $10 eV and remains nearly constant. 23 The ion temperature (T i ) varies from 10 to 40 eV and the magnetic field (B) embedded in the Taylor state is $2000 G. For these plasma parameters, the ion gyroradius and the Alfv en speed are $2 mm and $100 km/s, respectively and the plasma b varies from 0.1 to 1.…”

Section: Experimental Setup and Diagnosticsmentioning

confidence: 99%

Magnetothermodynamics: An experimental study of the equations of state applicable to a magnetized plasma

2019

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Measuring the equations of state of a compressed magnetized plasma is important for both advancing fusion experiments and understanding natural systems such as stellar winds. In this paper, we present results from our experiments on the thermodynamics of compressed magnetized plasmas; we call these studies "magnetothermodynamics." In these experiments, we generate parcels of relaxed, magnetized plasma at one end of the linear Swarthmore Spheromak eXperimental device and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. Instances of ion heating during compression are identified by constructing a pressure-volume diagram using the measured density, temperature, and volume of the magnetized plasma. An axial scan of the ion temperature at upstream locations suggests that the increase in ion temperature arises due to the compression of the magnetized plasma in the conducting boundary. The theoretically predicted magnetohydrodynamic (MHD) and double adiabatic equations of state are compared with experimental measurements to estimate the adiabatic nature of the compressed plasma. The equilibrium of our magnetized plasmas is well-described by magnetohydrodynamics; however, we find that the MHD equation of state is not supported by our data. Our results are more consistent with the parallel Chew-Goldberger-Low equation of state, suggesting that there is significant anisotropy in the ion distribution function.

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Section: Experimental Setup and Diagnosticsmentioning

confidence: 99%

Magnetothermodynamics: An experimental study of the equations of state applicable to a magnetized plasma

2019

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Retrospective of the ARPA-E ALPHA Fusion Program

et al. 2019

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This paper provides a retrospective of the ALPHA (Accelerating Low-cost Plasma Heating and Assembly) fusion program of the Advanced Research Projects Agency-Energy (ARPA-E) of the U.S. Department of Energy. ALPHA's objective was to catalyze research and development efforts to enable substantially lower-cost pathways to economical fusion power. To do this in a targeted, focused program, ALPHA focused on advancing the science and technology of pulsed, intermediate-density fusion approaches, including magneto-inertial fusion and Z-pinch variants, that have the potential to scale to commercially viable fusion power plants. The paper includes a discussion of the origins and framing of the ALPHA program, a summary of project status and outcomes, a description of associated technology-transition activities, and thoughts on a potential follow-on ARPA-E fusion program. Introduction:In 2014 the Advanced Research Projects Agency-Energy (ARPA-E) of the U.S. Department of Energy (DOE) launched a new research program on low-cost approaches to fusion-energy development [1]. The "Accelerating Low-Cost Plasma Heating and Assembly" (ALPHA) program set out to enable more rapid progress towards fusion energy by establishing a wider range of technological options that could be pursued with smaller, lower-cost experiments, short development and construction times, and high experimental throughput. Mainstream fusion research generally refers to magnetically or inertially confined fusion, both of which require expensive facilities for reasons briefly described below and explored in more detail in several books[2] [3]. ALPHA focused on magneto-inertial fusion (MIF), a class of pulsed fusion approaches with fuel densities in between those of magnetic and inertial fusion[4], [5] [6]. This paper presents a brief background on the origins of the ALPHA program, the results achieved by ALPHA-funded teams, and a look ahead to potential next steps for low-cost fusion development. OriginsARPA-E's mission is to develop transformational new energy technologies [7]. While DOE has pursued fusion energy as a potentially transformational opportunity for decades, ARPA-E had not supported any work in fusion prior to the ALPHA program. This was in part due to a perception that fusion was inherently the realm of "big science" and that ARPA-E, which runs relatively small, targeted, short-term programs across a wide spectrum of energy technologies-did not have a role to play in that development. In launching ALPHA, ARPA-E sought to change this dynamic and bring new players into the field -both in terms of the kinds of teams doing fusion development (e.g., smaller groups and private startups), and in terms of the sources of funding (e.g., private investors). The ALPHA program

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Magnetothermodynamics in SSX: Measuring the Equations of State of a Compressible Magnetized Plasma

Brown

Kaur

2019

Fusion Science and Technology

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Magnetothermodynamics (MTD) is the study of compression and expansion of magnetized plasma with an eye towards identifying equations of state for magneto-inertial fusion experiments.We present recent results from SSX experiments on the thermodynamics of compressed magnetized plasmas. In these experiments, we generate twisted flux ropes of magnetized, relaxed plasma accelerated from one end of a 1.5 m long copper flux conserver, and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. The instances of ion heating during compression are identified by constructing a PV diagram using measured density, temperature, and volume of the magnetized plasma.The theoretically predicted MHD and double adiabatic (CGL) equations of state are compared to experimental measurements to estimate the adiabatic nature of the compressed plasma. Since our magnetized plasmas relax to an equilibrium described by magnetohydrodynamics, one might expect their thermodynamics to be governed by the corresponding equation of state. However, we find that the magnetohydrodynamic equation of state is not supported by our data. Our results are more consistent with the parallel CGL equation of state suggesting that these weakly collisional plasmas have most of their proton energy in the direction parallel to the magnetic field.

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Temperature and Lifetime Measurements in the SSX Wind Tunnel

Cited by 6 publications

References 24 publications

Magnetothermodynamics: An experimental study of the equations of state applicable to a magnetized plasma

Magnetothermodynamics: An experimental study of the equations of state applicable to a magnetized plasma

Retrospective of the ARPA-E ALPHA Fusion Program

Magnetothermodynamics in SSX: Measuring the Equations of State of a Compressible Magnetized Plasma

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