Vapor shielding and erosion of surfaces exposed to a high heat load in an electrothermal accelerator

Bourham, Mohamed; Hankins, O.E.; Auciello, O.; Stock, J.; Wehring, B.W.; Mohanti, R.; Gilligan, J.G.

doi:10.1109/27.32246

Cited by 44 publications

(8 citation statements)

References 6 publications

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“…This vapour layer may shield the surface from some of the plasma heat flux by radiation, resulting in a lower heat flux to the target. While a vapour cloud is predicted by modelling [17] and supported by some experimental results which indicate shielding of the surface to have occurred [18,19] it is currently unclear as to its efficacy in improving divertor performance, and whether it will stably remain in front of the liquid surface on longer time scales. Therefore it is important to generate a greater understanding of the dynamics of the region of the plasma close to the liquid surface and the interaction between the two.…”

Section: Power Handlingmentioning

confidence: 93%

Interaction of a tin-based capillary porous structure with ITER/DEMO relevant plasma conditions

Morgan

Bekerom

Temmerman

2015

Journal of Nuclear Materials

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a b s t r a c tSn filled capillary porous structures were exposed to high flux low temperature plasma conditions at the Pilot-PSI linear device. Enhanced erosion above that expected classically was investigated via spectroscopic observation of Sn 0 emission from the plasma in front of the target surface while the surface temperature was monitored by both thermography and pyrometry. An anomalous erosion flux was observed as temperature increases, with onset for this occurrence varying strongly between different ion species. The results appear incompatible with existing 'adatom' models for the anomalous erosion flux. Further targets were exposed in turn to increasing heat fluxes and the heat removed determined from cooling water calorimetry, which was then compared to a solid Mo reference target. At high powers the total energy of the cooling water is reduced, indicating a shielding of the surface from the plasma heat flux by the vapour cloud in front.

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Section: Power Handlingmentioning

confidence: 93%

Interaction of a tin-based capillary porous structure with ITER/DEMO relevant plasma conditions

Morgan

Bekerom

Temmerman

2015

Journal of Nuclear Materials

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“…The experimental device SIRENS [6] has been used to study the erosion of candidate plasma-facing components under pulsed high heat loading conditions and to examine the fundamental mechanisms of energy transport through the plasma region immediately adjacent to the surface of such components. SIRENS produces high density (>lo25 m-3), low temperature (14 eV) plasmas by the ablation of the insulator (Lexan) with currents of up to 120 kA and energies of 1 to 7 kJ over pulse lengths of 100 ps in the source.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Visible light emission measurements from a dense electrothermal launcher plasma

et al. 1993

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A bstrocf-Measurements of the visible light obtaining quantitative data difficult. In this paper, we discuss emission from dense, weakly non-ideal Plasmas efforts to measure the average plasma temperature by using have been Performed On the the relative line ratio method. The results using this electrothermal launcher device "SIRENS". The technique are with the results o~conduc~vity, h a plasma is created by the ablation of a Lexan insulator in the source, which then flows through a flux, and mass loss methods for deducing temperature. cylindrical barrel which serves as the material sample. Visible light emission spectra have been observed both in-bore and from the muzzle flash of the barrel, and from the flash of the source.Due to high plasma opacity (the plasma emits as a near blackbody) and absorption by the molecular components of the vapor shield, the hotter core of the arc has been difficult to observe. Recent measurements along the axis of the device indicate time-averaged plasma temperatures in the barrel of about 1 eV for lower energy shots, which agree with experimental measurements of the average heat flux and plasma conductivity along the barrel. Measurements of visible emission from the source indicate time averaged temperatures of 1 to 2 eV which agree with the theoretical estimates derived from ablated mass measurements and calculated estimates derived from plasma conductivity measurements.

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“…Although there have been a series of theoretical and computational research attempts, however, the work reported here forms part of the continuous investigation into high heat flux carried out by electrothermal plasma sources [6][7][8][9][10][11]. As previously discussed in earlier research, the vapor shield mechanism was suggested to provide a protection to an exposed surface due to the large absorption fraction of the incident energy in the vapor boundary layer [4,6,9,10].…”

Section: Introductionmentioning

confidence: 99%

“…However, this is not the case and the heat flux does not reach the surface in full due to the shielding mechanism of the vapor cloud that absorbs a fraction of the incident energy. This has been explained in previous work as a vapor shield mechanism to evaluate the performance of plasma-facing components in future fusion tokamak reactors and the relevant applications of electrothermal plasma sources [7][8][9][10][11][12][13][14].…”

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confidence: 97%

Radiative Heat Transport through Vapor Plasma for Fusion Heat Flux Studies and Electrothermal Plasma Sources Applications

Bourham¹

2014

J Nucl Ene Sci Power Generat Technol

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High heat fluxes of up to 100 GW/m 2 and greater over a discharge period of 100 to 1000 µs can be generated from electrothermal (ET) plasma sources from the confined arc discharge. Sources with input energy of 10 kJ in a miniature capillary (4 mm radius and 9 cm length) are capable of producing 88.33 GW/m 2 heat flux inside the capillary, higher heat fluxes can be generated for higher input energies. Such high heat fluxes are adequate to simulate the energy deposition during hard disruptions in future fusion tokamak reactors, which result in erosion and thermal deformation of the surfaces of the critical internal components of the reactor. Calculation of the eroded mass due to intensive transient radiative heat transport to the surfaces is very critical in terms of the determination of the performance, durability and the life time of these components. Short intense high heat flux causes surface melting and vaporization. The vapor boundary layer absorbs a fraction of the incident heat flux which results in reducing the overall erosion. The transmitted fraction has a strong dependence on the energy input to the electrothermal source, which is used as a simulator for high heat flux deposition of plasma facing materials. The ETFLOW code models the plasma formation and calculates the plasma parameters for corresponding values of the transmission factor. Comparing experimental measurements to the computationally calculated mass erosion of the ET source material has verified the partial deposition of the incident heat flux. The energy transmission factor through the vapor boundary layer is found to be between 20% -60% for discharge current above 30 kA and between 60% -80% for less than 30 kA. The time of peak discharge current is set to be the time at which the transmission factor is evaluated.applications of such sources as mass accelerators, space minithrusters, propulsions and as high heat flux sources [1][2][3][4]. The heat fluxes generated in electrothermal sources can vary from as low as 5 GW/m 2 to as high as 100 GW/m 2 and greater, making such devices excellent simulators to study high heat flux erosion of plasma-facing components in fusion tokamak reactors [4,5].

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Vapor shielding and erosion of surfaces exposed to a high heat load in an electrothermal accelerator

Cited by 44 publications

References 6 publications

Interaction of a tin-based capillary porous structure with ITER/DEMO relevant plasma conditions

Interaction of a tin-based capillary porous structure with ITER/DEMO relevant plasma conditions

Visible light emission measurements from a dense electrothermal launcher plasma

Radiative Heat Transport through Vapor Plasma for Fusion Heat Flux Studies and Electrothermal Plasma Sources Applications

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