Transition radiation in metal-metal multilayer nanostructures as a medical source of hard x-ray radiation

Abstract

We show that a periodic metal-metal multilayer nanostructure can serve as an efficient source of hard x-ray transition radiation. Our research effort is aimed at developing an x-ray source for medical applications, which is based on using low-energy relativistic electrons. The approach toward choosing radiator-spacer couples for the generation of hard x-ray resonant transition radiation by few-MeV electrons traversing solid multilayer structures for the energies of interest to medicine (30–50keV) changes dramatically compared with that for soft x-ray radiation. We show that one of the main factors in achieving the required resonant line is the absence of the contrast of the refractive indices between the spacer and the radiator at the far wings of the radiation line; for that purpose, the optimal spacer, as a rule, should have a higher atomic number than the radiator. Having experimental goals in mind, we have considered also the unwanted effects due to bremsstrahlung radiation, absorption and scattering of radiated photons, detector-related issues, and inhibited coherence of transition radiation due to random deviation of spacing between the layers. Choosing as a model example a Mo–Ag radiator-spacer pair of materials, we demonstrate that the x-ray transition radiation line can be well resolved with the use of spatial and frequency filtering.

Metallic nanolayers: a sub-visible wonderland of optical properties [Invited]

“…Further into X-ray domain, the number of free electrons undergoes large jumplike increases as photon energy increases near so called K, L, M , and N absorption edges, which are due to reso-nant photo-ionization of bound electrons from respective shells into conduction state [32][33][34]. These jumps would affect the optical constants of metal surface, and may be used for various applications, in particular for narrow-line transition radiation by electron beams traversing a multilayer, super-lattice structure of metallic layers generating almost coherent radiation in soft [35] and hard X-ray [36] domains. In this paper we limit our consideration only to the quasi-static, i. e. SV spectral domain.…”

Novel Laser-Based Hyper-Short Pulse Sources and Single Particle Devices

“…The entire research effor t is aimed at the exper imental verification of pioneering theoretical results of this PI'sg roup (including Dr.S hkolnikov), on X-ray transition radiation generated byM eV electrons in multilayers olid targets,which, if successful, will become a basis for a practical, low-cost X-ray source,inpar ticular for medical applications.I ti sc ontinuation/extention of the theoretical research on the novele ffect of atomic-edges related resonant transition radiation done some while ago [24] by this PI and his group under the AFOSR support. At the moment, both exper imental and theoretical effor t on that project are in the progress; the most recent publication (in print) is to appear [21].…”

“…The PI and his group continue this resaerch and develop newd irection of resaerch under new, current AFOSR grant in pubications partofwhich is cited here [19][20][21][22].…”

“…The spectral lines of ∆ε (k) have unfamiliar shapes,i nvolving terms like ln (k − k sh ), k sh = cE sh / h, E sh is the absorption edge energy,a nd different for different shells [24,21]. In the water window, the spectral linewidths of ∆ε (ω ) are about three orders of magnitude larger The L 3 -shell lines of all elements under consideration except for nitrogen are broaden due to a contr ibution of the nearby( higher) L 2 -shell.…”

“…The major field of research interests of this PI can be loosely described as extreme nonlinear optics targeting var ious phenomena and their applications at the edge of capabilities of contemperar y science and technology: the interaction of super-powerful lasers (petawatt and beyond) and super-intense laser fields (up to 10 21 …”