Enhanced Versatility of Table‐Top X‐Rays from Van der Waals Structures

Abstract

Van der Waals (vdW) materials have attracted much interest for their myriad unique electronic, mechanical and thermal properties. In particular, they are promising candidates for monochromatic, table-top X-ray sources. This work reveals that the versatility of the table-top vdW X-ray source goes beyond what has been demonstrated so far. By introducing a tilt angle between the vdW structure and the incident electron beam, it is theoretically and experimentally shown that the accessible photon energy range is more than doubled. This allows for greater versatility in real-time tuning of the vdW X-ray source. Furthermore, this work shows that the accessible photon energy range is maximized by simultaneously controlling both the electron energy and the vdW structure tilt. These results should pave the way for highly tunable, compact X-ray sources, with potential applications including hyperspectral X-ray fluoroscopy and X-ray quantum optics.

Multicolor x-rays from free electron–driven van der Waals heterostructures

“…The peak energy of the output PCB x-rays generated from a vdW material is given as ( 13 )Epk=ℏcnormalβzfalse^0.25em⋅false(Ufalse^bold-italicg0false)1−timesboldβ⋅kfalse^where ℏ is the reduced Plank constant, c is the speed of light in free space, β ≡ ∣ β ∣ = ∣ v / c ∣ ( v being the electron velocity), kfalse^=false(sinnormalθobscosnormalϕobs,sinnormalθobssinnormalϕobs,cosnormalθobsfalse) is the unit vector of the emitted photon wave vector, θ obs is the polar angle of the observation direction, i.e., the angle between the incident electron beam and the observation direction, ϕ obs is the azimuth angle of the observation direction, g 0 is the reciprocal lattice vector of the crystal in the unrotated frame, zfalse^0.25em⋅false(Ufalse^bold-italicg0false)=−false(sinnormalϕtilcosnormalθtilfalse)g0x+false(sinnormalϕ...…”

Enhancing Large-Area Scintillator Detection with Photonic Crystal Cavities

“…One-dimensional (1D) PhC structures are made of periodically alternating layers. Featuring periods typically of several hundreds of nanometers, 1D PhCs have shown the ability to tailor visible light emission, such as that generated from free electron radiation. − Our use of a 1D model makes our theory valid only for devices whose transverse dimensions are much larger than their thickness, which include many types of large-area detectors . These large-area detectors are widely used in many scintillation fields, including medical X-ray imaging, security scanning, dark matter detection, and neutrino detection. − ,, In this work, the Purcell effect enabled by external PhC cavities allows us to mold the scintillator emission pattern beyond what is possible by just using external structures as reflective/transmissive media.…”

Coherent free-electron light sources

“…As a light source that can be tuned, SPR can generate microwave to X-ray frequencies. The SPR effect has been investigated extensively [62,63] and utilized extensively in investigations of particle identification [64,65] , particle acceleration [66] , and free-electron stimulated radiation [67] , among other applications. Similar to CR, SPR is the spontaneous emission of CR as Bloch photons in a periodic medium.…”