BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Development of an approach to minimize the effects of x-ray glitch es DTSTART;VALUE=DATE-TIME:20200713T134600Z DTEND;VALUE=DATE-TIME:20200713T134700Z DTSTAMP;VALUE=DATE-TIME:20261008T194031Z UID:indico-contribution-1892@indico.inp.nsk.su DESCRIPTION:Speakers: Nataliya Klimova (Immanuel Kant Baltic Federal Univ ersity\, 236041 Kaliningrad\, Russia)\nThe construction of 4th generation synchrotron sources will make it possible to obtain a fully coherent high- energy x-ray beam with extremely low emittance and high brightness. The us e of effective refractive optics already at the radiation output (front-en d) is necessary to realize all the possibilities and fully reveal the pote ntial of new diffraction-limited sources.\nX-ray refractive lenses (herein after CRL) [1] satisfy the above requirements. Monocrystalline diamond is considered to be an ideal material for CRL\, mainly because of its stabili ty in flow and high reflectivity in the hard X-ray range. Being universal for a wide range of applications\, diamond СRL\, nevertheless\, have a fe ature for application in spectroscopic experiments\, which was noted in a recently published article [2]\, which reported on the observation of inte nsity modulation at certain energies in the transmission spectrum.\nThis i ssue is well known in X-ray spectroscopy and is called “diffraction loss ” or “glitch” [3]. In paper [2\, 4] X-rays were propagating through lenses\, while the transmitted intensity was measured at different energie s. Use of compound refractive lenses\, that were perfectly aligned by stac king in a single plate\, gave us strong diffraction losses\, reducing the outgoing signal by maximal value of 40%. The magnitude of the effect was t hen minimized down to ~ 10% by use of CRLs compiled from individual lenses with different crystallographic orientation. At the same time\, X-ray gli tches did not affect any focal spot’s size or shape while only arousing the darkening of the focal spot at exact energies of X-ray glitches [4]. D espite X-ray glitches\, monocrystalline X-ray optical materials are prefer able than polycrystalline ones. While single crystals only uniformly reduc e the outgoing intensity (i.e.\, gain factor of the lens)\, polycrystallin e materials introduce speckles and distortions to the transmitted wave fro nt. Such negative influence of the inner material limits the resolution an d optical efficiency of X-ray lenses.\nIn [5-6]\, it was found that the sp atial position of the incident X-ray beam (relative to the lens aperture) most strongly affects the intensity and position of the glitches. The valu e of the glitch intensity strongly depends on the thickness of the materia l of the test sample\, which is associated with the effect of attenuation (extinction) i.e. as the thickness of the material increases\, the fractio n of incident radiation diffracts\, which causes a decrease in the intensi ty passing through the lens. Glitches become more pronounced with increasi ng thickness of the material through which the x-rays pass.\nAlthough glit ches are always present in the transmission spectrum of single-crystal mat erials\, based on the data obtained above\, attempts were made to develop approaches to minimize or\, ideally\, get rid of glitches in the spectrum of single-crystal optical elements.\nAn important result of the proposed w ork is a theoretical model\, which was confirmed by the experimental resul ts and which allows predicting the position and strength (intensity) of gl itches if the crystallographic orientation relative to the x-ray beam is k nown with sufficient accuracy. Therefore\, performing calculations for a p recisely positioned single-crystal lens with a known crystallographic orie ntation\, it is possible to choose specific energy intervals where the eff ect of glitches will have a minimal effect.\nThe results and assumptions m ade it possible to start developing a method of getting rid of glitches at each energy using a small lens flap\, which is calculated on the basis of a program that can determine the lens orientation solely from the spectru m of glitches and on the basis of an analytical approach that allows you t o refine the orientation of the crystal and\, probably \, will allow the u se of crystalline lenses for experiments in which it is necessary to chang e the energy of the incident beam.\nHow to avoid glitches (practical guida nce). First current orientation and cell parameter of the lens has to be d etermined. For this energy of several glitches (at least 3) have to be mea sured with high precision. Then the found energies can be fitted using pro posed approach (by tilting possible K0 directions and comparing the result ing spectrum to the measured one). This will allow to assign hkl indexes t o the observed glitches. Next step is to calculate analytically the exact direction of the incident beam and cell parameter\nThis will allow to pred ict with high precision all glitches for current orientation. Next multipl e glitches spectra for different small tilts can be calculated\, so for ea ch energy a tilt with no glitches at that energy can be selected. During t he energy scan the lens has to be tilt into precomputed orientations.\nThe glitches are rather sharp\, so the tilt required to shift a glitch is sma ll. Therefore the efficiency of the lens shouldn’t suffer. The method mi ght require small increase in the lenses thickness to have possibility to tilt the lenses.\nThus\, by performing the sequence of actions indicated i n the developed approach\, the negative impact of glitches can be avoided. \nThis research was supported by the Russian Science Foundation (Project No. 19-72-30009).\nReferences: \n [1] Snigirev A. V. Kohn\, I. Snigireva a nd B. Lengeler\, A compound refractive lens for focusing high-energy X-ray s //Nature. – 1996. – Т. 384. – №. 6604. – С. 49.\n[2] M. Poli karpov\, H. Emerich\, N. Klimova. I. Snigireva and A. Snigirev Diffraction losses in monocrystalline X-ray refractive lenses // Proceedings of SPIE – 2017. – Vol.10235\, – P. 102350H-2.\n[3] G. Turiyanskii\, S. S. Gi zha\, V. M. Senkov\, I. V. Pirshin\, Y. M. Stanishevskii\, Band reject fil tration of the excitation spectrum at energy dispersive X-ray spectroscopy of weak signals // JETP Lett. – 2016\, – Vol. 104\, – P. 417.\n[4] M. Polikarpov\, H. Emerich\, N. Klimova\, I. Snigireva\, V. Savin and A. S nigirev Spectral X-ray glitches in monocrystalline diamond refractive lens es // Physica Status Solidi B – 2018. – Vol.255 – P. 1700229.\n[5] Q. Zhang\, M. Polikarpov\, N. Klimova\, H. B. Larsen\, R. Mathiesen\, Herm ann Emerich\, G. Thorkildsen\, I. Snigireva and A. Snigirev\, Investigatio n of glitches induced by single-crystal diamond compound refractive lenses based on crystal orientation//AIP Conference Proceedings. – 2019. - Vol . 2054. - P. 060007 \n[6] Q. Zhang\, M. Polikarpov\, N. Klimova\, H. B. La rsen\, R. Mathiesen\, H.Emerich\, G. Thorkildsen\, I. Snigireva and A. Sni girev\, Investigation of ‘glitches’ in the energy spectrum induced by single-crystal diamond compound X-ray refractive lenses // Journal of Sync hrotron Radiation. - 2019. – Vol. 26(1). – P. 109-118.\n\n\n---------- \n\nhttps://indico.inp.nsk.su/event/24/contributions/1892/ LOCATION: URL:https://indico.inp.nsk.su/event/24/contributions/1892/ END:VEVENT END:VCALENDAR