Linac-augmented light sources : an incremental concept for enhancing the capabilities of existing 3rd-generation storage rings.

Abstract

Planned and proposed 4th-generation x-ray sources, such as energy-recovery linacs (ERLs) and single-pass x-ray free-electron lasers (X-FELs) offer a number of potential advantages, including small source size, higher peak brightness, ultrashort pulses, and potentially temporally and transversely coherent pulses. While offering unique capabilities, such facilities will also offer several important limitations, including limited numbers of user beamlines (for FELs) and a pulse-repetition rate that may be too high for many dynamics experiments (ERLs). In addition, there are many technical challenges associated with both types of facilities. A third type of facility, exemplified by the Short Pulse Photon Source (SPPS) at SLAC [1], would support neither a large number of users simultaneously nor generate coherent pulses, but would generate very intense, short x-ray pulses. Such a facility could serve as the starting point for either an ERL or an X-FEL, or a combined, hybrid machine. For the foreseeable future, however, existing 3rd-generation light source storage rings, such as the Advanced Photon Source, will continue to play important roles in supporting scientific research utilizing high-brightness x-rays. Existing facilities offer the powerful combination of a large number of user beamlines, efficient use of electron beam energy, and established user communities, and a program of incremental investment in, and improvements to, these facilities should continue to pay dividends into the future. This document discusses potential upgrade paths based on the Advanced Photon Source (APS) as a model 3rd-generation facility. If existing 3rd-generation facilities are to remain centers of excellence for light source-based research into the future, they must not only maintain and enhance their support of their existing user base, but also seek to expand their capabilities to support additional classes of users. There are several paths available toward this goal. The APS is already committed to providing enhanced technical and operational support to its resident users and beamlines, and this is expected to continue into the future. Given that this work will also include such topics as optimization of x-ray beamline optics and improvements in data acquisition software, additional gains in effective performance will be driven by the performance of the accelerator itself, and by additional capabilities which could be added to the APS accelerator complex.