High-Brightness Beam Technology Development for a Future Dynamic Mesoscale Materials Science Capability

Abstract

A future capability in dynamic mesoscale materials science is needed to study the limitations of materials under irreversible and extreme conditions, where these limitations are caused by nonuniformities and defects in the mesoscale. This capability gap could potentially be closed with an X-ray free-electron laser (XFEL), producing 5 × 1010 photons with an energy of 42 keV, known as the Matter–Radiation Interactions in Extremes (MaRIE) XFEL. Over the last few years, researchers at the Los Alamos National Laboratory have developed a preconceptual design for a MaRIE-class XFEL based on existing high-brightness beam technologies, including superconducting L-band cryomodules. However, the performance of a MaRIE-class XFEL can be improved and the risk of its operation reduced by investing in emerging high-brightness beam technologies, such as the development of high-gradient normal conducting radio frequency (RF) structures. Additionally, an alternative XFEL architecture, which generates a series of high-current microbunches instead of a single bunch with uniformly high current along it, may suppress the most important emittance degradation effects in the accelerator and in the XFEL undulator. In this paper, we describe the needed dynamic mesoscale materials science capability, a MaRIE-class XFEL, and the proposed microbunched XFEL accelerator architecture in detail.

Versatile, high brightness, cryogenic photoinjector electron source

“…As such, this project would benefit greatly from an enhancement of the beam brightness at the source, as was demonstrated by the work reported in Ref. [5].…”

“…Unsurprisingly, these innovations in the use of high-brightness beams present a concomitant challenge, to strongly increase the beam brightness produced by the source. In regard to XFEL applications, two recent initiatives indicate a necessity for beams which far exceed the current stateof-the-art: the ultra-compact XFEL [4] and the MaRIE XFEL [5]. The first, pioneered by a UCLA-centered collaboration, is an ultra-compact XFEL (UC-XFEL), which promises lasing, initially at soft x-ray wavelengths, with a total footprint under 40 m in length.…”

Towards an ultra-compact x-ray free-electron laser (Conference Presentation)

“…We explore this process in detail, identifying a compact (total length <10 m) two-stage compression scheme: the first is a compact chicane that yields I = 400 A [24]; the second is an optical micro-bunching technique that utilizes the inverse free-electron laser (IFEL) mechanism [25,26]. The advantages of such an approach, which have been discussed in several recent works [24,27], are manifold. If one does not attempt to compress the beam into a single pulse, but instead organizes the beam into a pulse train on the scale of a laser wavelength λ L , then the bending and accompanying longitudinal motion is limited.…”

“…As the gap used in the undulator scales with λ u , the material boundaries in mm-period undulators are only 100's of µm away, and serious issues may arise from resistive wall wakefields. Use of micro-bunches can strongly mitigate this issue [30,27,26], and this aspect of XFEL design is therefore attractive in our case.…”

“…Further, the use of coatings such as graphene and silicon oxynitride [48] is now under study for mitigation of field emission. These efforts, while not critical to the vision of the UC-XFEL presented here, are directed towards large long-term projects such as compact linear colliders [44,49] and next generation full-scale XFELs such as MaRIE [27].…”