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SUMMARY:Generation and use of coherent X-ray beams at future SKIF storage 
 ring
DTSTART;VALUE=DATE-TIME:20200715T070000Z
DTEND;VALUE=DATE-TIME:20200715T072000Z
DTSTAMP;VALUE=DATE-TIME:20260419T153336Z
UID:indico-contribution-1860@indico.inp.nsk.su
DESCRIPTION:Speakers: Sergey Rashchenko (Novosibirsk State University)\nIn
  1990s\, the emergence of the 3rd generation synchrotron user facilities e
 quipped with undulator sources\, stimulated pioneering works on interactio
 n of coherent X-ray beams with matter (Brauer et al. 1995)\, resulted in t
 he development of X-ray photon correlation spectroscopy (XPCS) technique\,
  capable to probe nanoscale fluctuations up to kHz frequencies using dynam
 ics of speckle pattern given by scattering of coherent X-ray beam from the
  sample. More recently (and highly aided by the development of modern high
 -throughput data analysis algorithms)\, coherent X-ray diffraction imaging
  (CXDI)\, also known as lensless imaging\, revolutionized the field of X-r
 ay microscopy\, finally bringing users the possibility of non-destructive 
 2D and 3D imaging of complex structures with unprecedented ~10 nm resoluti
 on. However\, strict requirements to transverse coherence of X-ray probe p
 ut serious limits on further development of CXDI-based techniques at the 3
 rd generation facilities\, where coherent flux after spatial filtering bec
 omes unacceptably small at energies above ~20 keV. At the same time\, the 
 latter was used as one of the strongest arguments of the user community fo
 r push towards construction of MBA-based 4th generation of storage rings w
 ith ultra-low-emittance.\nSince coherent flux can be simply expressed as $
 F_{coh}={\\lambda^2\\over4}B$\, where $\\lambda$ is X-ray wavelength\, and
  *B* – source brightness\, the demand for higher coherent flux is often 
 translated as demand for higher brightness – a recognizable motto for bo
 th accelerator and user communities. From the same relationship one can al
 so easily see that even more brightness is needed to obtain the same coher
 ent flux at shorter wavelengths / higher energies. Another expression $F_{
 coh}={\\lambda^2\\over 16\\pi^2}F/\\varepsilon_{tot}$\, where *F* is total
  flux\, and $\\varepsilon_{tot}$ – 4D phase volume of X-ray beam\, illus
 trates that it is the phase volume of the undulator X-ray source that shou
 ld be minimized in order to deliver a maximum number of coherent photons t
 o end-user (given total flux has already reached its limit imposed by mach
 ine current and undulator technology). Whereas at the 3rd generation facil
 ities the phase volume of undulator source was dominated by electron beam 
 emittance with negligible influence of other factors\, the estimation and 
 minimization of undulator source phase volume at 4th generation facilities
  requires more elaborate approach taking into account electron beam energy
  spread\, undulator phase error\, and matching of phase-space ellipses bet
 ween electron and X-ray beams.\nIn our contribution we will present estima
 tions of coherent flux at different energies available for future users of
  ultra-low-emittance SKIF storage ring (to be commissioned in 2023) and di
 scuss ways of its optimization\, as well as future scientific program of u
 ser experiments with diffraction-limited X-ray beams.\n\nBrauer\, S.\, Ste
 phenson\, G.B.\, Sutton\, M.\, Brüning\, R.\, Dufresne\, E.\, Mochrie\, S
 .G.J.\, Grübel\, G.\, Als-Nielsen\, J.\, and Abernathy\, D.L. (1995) X-Ra
 y Intensity Fluctuation Spectroscopy Observations of Critical Dynamics in 
 F${\\mathrm{e}}_{3}$Al. Physical Review Letters\, 74\, 2010–2013.\n\nhtt
 ps://indico.inp.nsk.su/event/24/contributions/1860/
LOCATION: Zoom 890 9721 5207
URL:https://indico.inp.nsk.su/event/24/contributions/1860/
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