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Title: Effect of surface segregation and mobility on erosion of plasma-facing materials in magnetic fusion systems

Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
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Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 458; Journal Issue: C; Related Information: CHORUS Timestamp: 2016-09-04 17:41:25; Journal ID: ISSN 0022-3115
Country of Publication:

Citation Formats

Sizyuk, Tatyana, and Hassanein, Ahmed. Effect of surface segregation and mobility on erosion of plasma-facing materials in magnetic fusion systems. Netherlands: N. p., 2015. Web. doi:10.1016/j.jnucmat.2014.12.105.
Sizyuk, Tatyana, & Hassanein, Ahmed. Effect of surface segregation and mobility on erosion of plasma-facing materials in magnetic fusion systems. Netherlands. doi:10.1016/j.jnucmat.2014.12.105.
Sizyuk, Tatyana, and Hassanein, Ahmed. 2015. "Effect of surface segregation and mobility on erosion of plasma-facing materials in magnetic fusion systems". Netherlands. doi:10.1016/j.jnucmat.2014.12.105.
title = {Effect of surface segregation and mobility on erosion of plasma-facing materials in magnetic fusion systems},
author = {Sizyuk, Tatyana and Hassanein, Ahmed},
abstractNote = {},
doi = {10.1016/j.jnucmat.2014.12.105},
journal = {Journal of Nuclear Materials},
number = C,
volume = 458,
place = {Netherlands},
year = 2015,
month = 3

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.jnucmat.2014.12.105

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Cited by: 1work
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  • This paper will report on the proof-of-principle (POP) experiments conducted to demonstrate reduced wall recycling, using a laboratory-scale test unit, constructed based on the concept of moving-surface plasma-facing component (MS-PFC). In this concept, the moving-surface exposed to edge plasmas in steady state magnetic fusion devices is continuously deposited ex-situ with a getter material, so that particle trapping capabilities can be regenerated prior to the subsequent exposure. In our previous paper, the construction details of the MS-PFC test unit and the first results in the case of titanium gettering was reported, but in the present paper preliminary results in the casemore » of lithium gettering will be presented for comparison. Results indicate that the H{sub {alpha}} light intensity used as the measure of hydrogen recycling is reduced by {approx}6% due to titanium gettering and by {approx}12% due to lithium gettering, both at steady state.« less
  • In our previous work, the first proof-of-principle experiments were successfully conducted on the particle control capability based on the concept of moving-surface plasma-facing component (MS-PFC). Over a continuously titanium-gettered rotating drum, hydrogen recycling was found to be reduced down to levels around 94% even at steady state. These experiments on the MS-PFC concept have now been extended to the second stage where lithium is employed as the getter material, while using the same rotating drum. These experiments are intended to pilot the potential use of lithium as a flowing liquid facing the edge plasmas in steady state reactors beyond ITER.more » Reported in this paper are rather dramatic findings that hydrogen recycling is reduced down to levels around 76% and 86% at steady state over the rotating drum at the lithium deposition rates of 9.5 A/s and 7.3 A/s, respectively. These steady state recycling data have been nicely reproduced by a simple zero-dimensional particle balance model.« less
  • For the lifetime evaluation of plasma facing materials in fusion experimental machines, it is essential to investigate their surface behavior and their temperature responses during an off-normal event such as the plasma disruptions. An infrared thermometer with a sampling speed as fast as 1{times}10{sup {minus}6} s/data, namely, the high-speed infrared thermometer (HSIR), has been developed by the National Research Laboratory of Metrology in Japan. To evaluate an applicability of the newly developed HSIR on the surface temperature measurement of plasma facing materials, high heat flux beam irradiation experiments have been performed with three different materials under the surface heat fluxesmore » up to 170 MW/m{sup 2} for 0.04 s in a hydrogen ion beam test facility at the Japan Atomic Energy Research Institute. As for the results, HSIR can be applicable for measuring the surface temperature responses of the armor tile materials with a little modification. It is also confirmed that surface temperatures measured with the HSIR thermometer show good agreement with the analytical results for stainless steel and carbon based materials at a temperature range of up to 2500{degree}C. However, for aluminum the HSIR could measure the temperature of the high dense vapor cloud which was produced during the heating due to lower melting temperature. Based on the result, a multichannel arrayed HSIR thermometer has been designed and fabricated. {copyright} {ital 1996 American Institute of Physics.}« less
  • This paper describes the results of a study of the properties affecting the performance of carbon--carbon composites as plasma-facing materials in magnetic fusion reactors. A composite has already been chosen for the protective limiter of the rf antenna in the Tokamak Fusion Test Reactor and composites are being considered for divertor applications in the Compact Ignition Tokamak. In direct comparison with results for POCO AXF-5Q graphite, the composites were able to survive more severe high heat flux conditions, released less water vapor and gases during the thermal outgassing tests, and retained less tritium during exposure to tritium gas and plasma.
  • The chemical erosion behavior of graphite materials preexposed in the Tokamak Fusion Test Reactor (TFTR) as the bumper limiter has been investigated spectroscopically under deuterium plasma bombardment in the Plasma Interactive Surface Component Experimental Station-A (PISCES-A) facility. The deuterium plasma bombardment conditions are ion bombarding energy of 300 eV, ion flux of 1.7{times}10{sup 18} ions s{sup {minus}1} cm{sup {minus}2}, plasma density of 1.4{times}10{sup 12} cm{sup {minus}3}, electron temperature of 11 eV, and neutral pressure of 3{times}10{sup {minus}4} Torr. The chemical erosion yield is measured with calibrated CD-band spectroscopy during the temperaure ramp from 100 to 900 {degree}C at an averagemore » rate of {similar to}5 K/s. The materials used include virgin POCO graphite and graphite tile pieces from the redeposited and eroded areas of the bumper limiter of TFTR. The deuterocarbon formation rate from TFTR redeposits maximizes at {similar to}500 {degree}C. Essentially the same chemical erosion behavior is observed for TFTR-eroded and virgin graphites and is characterized by the compound peak, indicative of two erosion yield maxima at around 575 and 700 {degree}C. The maximum erosion yield for TFTR redeposits is found to be {similar to}15% higher than those of TFTR-eroded and virgin POCO graphites which is attributed to deuterium incorporated in the redeposited material. In addition, the removal behavior of redeposits by helium plasma bombardment has been studied. The removal rate is evaluated to be similar to the physical sputtering yield of carbon by helium. The surface morphology and surface composition have been analyzed with scanning electron microscopy and electron microprobe analysis along with these erosion yield measurements.« less