Imitation of effects of a fusion reactor environment on optical properties of metallic mirrors

Plasma Devices and Operations

Vukolov

2007

2007) First mirrors for diagnostic systems of an experimental fusion reactor I. Simulation mirror tests under neutron and ion bombardment, Plasma Devices and Operations, 15:1, 33-75To link to this article: http://dx.Among the diagnostic systems planned for use in the International Thermonuclear Experimental Reactor to control the reactor operation, a large number of these systems have to use the mirrors to input or output the electromagnetic radiation to or from the burning plasma in different parts of the spectrum. The mirrors placed inside the vacuum vessel will be subjected to the impact of several factors, resulting in degradation in their optical characteristics. The most critical factors are erosion under the bombardment with a flux of high-energy particles, deuterons and tritons, and the deposition of the products of erosion of the in-vessel components. The first part of this review presents the results of the simulation experiments studying the effect of sputtering and deposition of contaminants on the optical properties of mirrors fabricated from different materials. In the second part of the review, the results of mirror testing on the operating large-scale fusion devices are considered.

Section: Downloaded By [New York University] At 15:55 24 June 2015mentioning

confidence: 71%

Section: 313mentioning

confidence: 93%

First mirrors for diagnostic systems of an experimental fusion reactor I. Simulation mirror tests under neutron and ion bombardment

Orlinski

Plasma Devices and Operations

Vukolov

2007

“…Results obtained with heavy ions ͑by Whitten, 36 and references therein͒ cannot be utilized because of the different ratio between rates of sputtering and defect accumulation near the surface. 37 Recently, Voitsenya et al 38 at the Kharkov Institute of Physics and Technology made measurements of the longterm sputtering effects of light ions on the optical properties of metal mirrors. Mirror samples were bombarded with ions from a hydrogen or deuterium plasma.…”

Section: Effect Of Sputteringmentioning

confidence: 99%

Materials selection for the in situ mirrors of laser diagnostics in fusion devices

Review of Scientific Instruments

Konovalov

Becker

et al. 1999

When mirrors for the laser scattering diagnostic for large fusion devices need to be inside the vacuum chamber, they are subjected to irradiation by multiple high-energy laser pulses and bombardment by charge exchange atoms. Both of these assaults are known to degrade and eventually damage metal laser mirrors given sufficient time and flux. Our aim in this article is to use current data on these damage mechanisms to make design selections of metal mirror materials for application in fusion device diagnostics. We identify tradeoffs between low sputtering rates and multipulse laser damage resistance in candidate metals. The data for multipulse laser damage are incomplete and extend to a maximum of only 10 4 shots for a few metals. However, there is a clear trend of decreasing laser-damage threshold with increasing number of shots, and damage threshold fluences can fall to 10% of the single-pulse damaging laser fluence. Further experiments up to 10 6 or 10 8 laser shots need to be conducted on the likely mirror candidate metals for use in new plasma devices. We define a figure-of-merit based on current laser damage data and employ it in our analysis. Recent data on the sputtering yield and reflectance degradation of metal mirrors give a different priority ranking of candidate metals. Overall, the preferred material selection depends on the number of laser shots and the number of plasma pulses that the mirror must endure before replacement is allowed. For example, we find that for conditions typical of the LHD ͑10 s plasma pulses with a 10 Hz laser PRF͒, Au, Ag, and Cu are candidate materials if mirrors are replaced after 10 3 plasma pulses; Au and Rh are candidates if the replacement interval is 10 4 pulses; and if the replacement interval is further increased to 10 5 plasma pulses, then Mo is the candidate material. Other materials might also be candidates but the data on them are still insufficient.

“…Previously such effect was examined for copper and stainless steel mirrors [1,2] irradiated with high energy (1-3 MeV) Cu + and Cr + ions for simulating neutron irradiation. It was found that degradation of these mirrors under long term sputtering with hydrogen plasma occurs with approximately similar rate as that for the mirrors not preliminary bombarded with high energy metal ions.…”

Section: Introductionmentioning

confidence: 99%

Effect of sputtering on self-damaged recrystallized W mirror specimens

Journal of Nuclear Materials

Balden

Belyaeva

et al. 2013

Self Cite

The effect of heavy sputtering and of neutron irradiation simulated by displacement damaging with of 20 MeV W 6+ ions on the optical properties of tungsten mirrors was studied. Ar + ions with 600 eV of energy were used as imitation of charge exchange atoms ejected from fusion plasma. The ion fluence dependence of the surface topography and the optical properties of polycrystalline, recrystallized tungsten (grain size 20 -100 µm) were studied by optical microscopy, interferometry, reflectrometry and ellipsometry. Furthermore, after sputtering in total a layer of 3.9 μm in thickness, the orientation and the thickness of the eroded layer of many individual grains was determined by electron backscattering diffraction and confocal laser scanning microscopy. Concluding from the obtained data the neutron irradiation, at least at the damage level would be achieved in ITER, has not to make an additional contribution in the processes developing under impact of charge exchange atoms only.