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SUMMARY:Method for polarization shaping at free-electron lasers
DTSTART;VALUE=DATE-TIME:20200713T131500Z
DTEND;VALUE=DATE-TIME:20200713T131600Z
DTSTAMP;VALUE=DATE-TIME:20260416T212301Z
UID:indico-contribution-1815@indico.inp.nsk.su
DESCRIPTION:Speakers: Andrei Trebushinin (Novosibirsk State University)\nX
 -ray free-electron lasers (FEL) deliver high-power\, ultra-short polarized
  X-ray pulses\, where the polarization state is determined by the electron
  beam trajectory in the FEL undulator. In this way\, the polarization stat
 e depends on the kind of a magnetic structure used\, and is fixed along th
 e entire pulse. However\, it would be beneficial to control the dependence
  of the polarization shape on time over the scale of one single pulse dura
 tion (about tens of femtoseconds). Such radiation may enable study of ultr
 afast molecular dynamics and magnetism.\nIn this contribution\, we discuss
  a new method to control the polarization state of a single FEL pulse long
 itudinally (in time) and/or transversely (spatially) on the scales of 100 
 femtoseconds and several micrometers respectively.\nWe propose to use a cr
 ossed-undulators setup consisting of a pair of two co-axial Apple-X undula
 tors. These undulators are scheduled for installation downstream the nomin
 al SASE3 undulator line of European XFEL and they may be tuned to emit rad
 iation pulses with two orthogonal polarization states\, e.g. linear (verti
 cal and horizontal) or circular (right and left). Both pulses upon reachin
 g the sample are overlapped both spatially and temporally with some phase 
 difference. Their interference yields polarization states\, circular or li
 near respectively\, with orientation that depends on that phase difference
 . If the frequency of one of the pulses is detuned\, polarization of the r
 esulting radiation will be shaped temporally. If the distance between the 
 undulator cells is considerable\, a difference between the wavefront curva
 tures allows shaping the resulting polarization spatially. We investigate 
 possibilities to maximize or minimize both effects with a focusing system 
 and demonstrate it with numerical simulations.\n\nhttps://indico.inp.nsk.s
 u/event/24/contributions/1815/
LOCATION:
URL:https://indico.inp.nsk.su/event/24/contributions/1815/
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