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.
Highlights
An important emerging materials science frontier is in mesoscale science, and especially its time-dependence or dynamics
There are two specific emerging high-brightness beam technologies we have considered to improve the performance of Matter–Radiation Interactions in Extremes (MaRIE)-class X-ray free-electron laser (XFEL): (1) High-gradient cyrocooled normal conducting radio frequency (RF); and (2) an alternative accelerator architecture generating a microbunched beam instead of a single, high-current electron bunch
The key trade-off between the enhanced self-amplified spontaneous emission (eSASE) and laser assisted bunch compression (LABC) conditions is that a flatter bunch with more total trapped charge for the same compression ratio can be achieved with the LABC condition, but at the cost of a higher required laser modulation which will lead to a higher final beam energy spread
Summary
An important emerging materials science frontier is in mesoscale science, and especially its time-dependence or dynamics. For medium-Z elements, such an XFEL would have to produce photon energy of 42 keV and above to penetrate samples of material up to a hundred microns (see Figure 2). An XFEL with these parameters is positioned to fill a critical gap in materials testing, with a length scale between the macroscale of LANL’s Dual-Axis Radiographic Hydro Test (DARHT) [4] and the atomic scale of the Lawrence Livermore National Laboratory’s National Ignition Facility (NIF) [5], see Figure 3. There are two specific emerging high-brightness beam technologies we have considered to improve the performance of MaRIE-class XFELs: (1) High-gradient cyrocooled normal conducting RF; and (2) an alternative accelerator architecture generating a microbunched beam instead of a single, high-current electron bunch. Blown apart when imaged, allowing for multiple views during dynamic events
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