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SUMMARY:Status of dynamic diagnostics of plasma material interaction based
  on synchrotron radiation scattering at the VEPP-4 beamline 8
DTSTART;VALUE=DATE-TIME:20160706T070000Z
DTEND;VALUE=DATE-TIME:20160706T074000Z
DTSTAMP;VALUE=DATE-TIME:20260513T215620Z
UID:indico-contribution-1226@indico.inp.nsk.su
DESCRIPTION:Speakers: Aleksey Arakcheev (Budker INP)\nThe residual mechani
 cal deformation and stress were measured in the preliminary experiments ca
 rried out at synchrotron radiation (SR) scattering stations at VEPP-3 in t
 he Siberian Center of Synchrotron and Terahertz Radiation (“Precision di
 ffractometry and anomalous scattering”\, “Diffractometry in hard X-ray
 s”). The deformation and stress were calculated on the basis of the depe
 ndence of the scattering angle on the inclination of the irradiated tungst
 en sample. Significant changes in the SR diffraction are found as the resu
 lt of material recrystallization or irradiation of the material by plasma.
  It implies that the SR scattering diagnostics may be an informative instr
 ument for in-situ observations of the state of the plasma facing component
 s.\n\n\n\nThe next stage of the SR scattering diagnostics development at t
 he VEPP-4 beamline 8 is the dynamic measurements during pulsed heat loads.
  Currently a 1J Nd:YAG laser is used for the 0.2ms heat load simulation an
 d a 100J laser is under development. The parameters of the heating are suf
 ficient for simulation of the expected pulsed heat load in ITER. The destr
 uctive effect of pulsed heat loads is caused by mechanical stresses that o
 ccurs in highly non-uniformly heated materials. The main aim of the curren
 t development of diagnostics based on SR scattering is the dynamic measure
 ments of the mechanical deformation and stress dependences on the depth be
 low the surface. It looks like the rotation of crystallographic planes due
  to mechanical deformations is the dominant effect in the SR scattering. S
 o the deformation and stress distributions may be calculated using measure
 ments of the diffraction peak parameters of SR passed through the sample. 
 The set of requirements (the pass through material\, dynamical measurement
 s of pulsed processes) determines restrictions on SR brightness and energy
 . The SR from VEPP-4 with energy 69keV will be used for experiments with t
 ungsten. Also a single crystal samples are necessary for increasing of the
  diffraction peak brightness. Currently\, the one-dimensional gas X-ray de
 tector DIMEX is used for measurements. The development of the silicon dete
 ctor for increasing of the sensitivity is in progress.\n\n\nThe first dyna
 mical measurements of the diffraction peak of SR passed through the 250µm
  thick single crystal tungsten were carried using the one-dimensional dete
 ctor. The inclination of the sample to the initial SR beam was about 45° 
 in order to result in the diffraction peak shift. The change of the SR sca
 ttering angle about 0.1° during the laser irradiation and the subsequent 
 fast return during the comparable time were found out. The behavior could 
 be explained by the bending of the initially plane sample. The bending mom
 ent is proportional to the difference of the temperature at the heated and
  opposite sides. The moment disappears while the temperature distribution 
 flattens across the thin sample. Conversely the temperature propagation al
 ong the sample surface takes more time. Thus the expected effect of the cr
 ystal planes rotation could be estimated as the diffraction peak shift aft
 er the temperature flattening across the sample. The measured shift was ab
 out 0.03°. The measurements of deformation and stress distributions acros
 s the sample requires the analysis of the diffraction peak shape during th
 e laser irradiation.\n\nhttps://indico.inp.nsk.su/event/3/contributions/12
 26/
LOCATION:Budker INP Conference Hall
URL:https://indico.inp.nsk.su/event/3/contributions/1226/
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