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SUMMARY:Status of the studies of thermal stresses and deformations in mate
 rials caused by pulsed heat loads in BINP
DTSTART;VALUE=DATE-TIME:20200714T082000Z
DTEND;VALUE=DATE-TIME:20200714T084000Z
DTSTAMP;VALUE=DATE-TIME:20260419T054206Z
UID:indico-contribution-1842@indico.inp.nsk.su
DESCRIPTION:Speakers: Aleksey Arakcheev ()\nThe operation of fusion reacto
 r on the base of tokamak geometry of magnetic field is expected to be acco
 mpanied by pulsed heat loads to divertor. The loads lead to formation of p
 lastic deformations and residual mechanical stresses. The stresses may res
 ult in mechanical destruction of tungsten armor of divertor. Typically it 
 appears as a crack formation. The cracks decreases the heat removal from t
 he surface\, spoils the geometry of plasma flow to divertor\, make easier 
 the formation and ejection of micro particles\, etc. The optical and X-ray
  diagnostics are applied to studies of the stresses and deformations in tu
 ngsten caused by pulsed heat loads in Budker Institute.\nThe optical diagn
 ostics are applied at the facility BETA (Beam of Electrons for material Te
 st Application). The measuring of thermal radiation and scattered on the s
 urface laser radiation during pulsed heating gives information about the s
 urface temperature\, roughness and curvature of the surface\, etc. Among t
 he most significant discoveries made using these diagnostics\, we can note
  the detection of a delay between the end of the pulse heating and the for
 mation of cracks by several orders of magnitude compared to the expected v
 alues. Recently\, a new optical diagnostic has been developed\, which allo
 ws determining the radius of curvature of the surface by changing the foca
 l length. The results of the diagnostics confirmed the previous results on
  the delay. In addition\, measuring the dynamics of surface curvature allo
 ws calculating the distribution of deformations and stresses along the dep
 th of the sample. Of course\, the results of such calculations depend on t
 he applied strain models.\nThe more direct methods for measuring residual 
 stresses are used at stations of X-ray scattering «Precision diffractomet
 ry and anomalous scattering» and «Diffraction "movie"» at the VEPP-3 so
 urce of synchrotron radiation. The residual stresses may be calculated usi
 ng the dependence of the scattering angle on the inclination of the sample
 . The station «Precision diffractometry and anomalous scattering» was us
 ed to make measurements of residual stresses with the spatial distribution
 s. The decreasing of residual stress during slow heating simulating the re
 sult of continual heating of divertor was measured at the station «Diffra
 ction "movie"».\nThe station of X-ray radiation «Plasma» at the VEPP-4 
 source of synchrotron radiation is oriented to measurements of deformation
 s and mechanical stresses in during pulsed heating simulating by laser rad
 iation. The previous experiments demonstrated the possibility of the measu
 rements of the depth distribution of deformations in single-crystal tungst
 en with the time resolution about 10 μs. The first demonstrative experime
 nts on the measurements of the diffraction on polycrystall tungsten were c
 arried out. The acceptable magnitude of signal were measured with the whol
 e exposure 150 ms. The time resolution is admissible for  measurements of 
 the dynamic of the stress between the pulsed heating and crack formation.\
 n\nhttps://indico.inp.nsk.su/event/24/contributions/1842/
LOCATION: Zoom 890 9721 5207
URL:https://indico.inp.nsk.su/event/24/contributions/1842/
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