A few weeks ago, I wrote about a recent report from the Subcommittee on Future X-ray Light Sources of the Basic Energy Sciences Advisory Committee (BESAC). The report strongly endorsed the science that can be facilitated by X-ray free electron lasers and called for a facility that could provide beams with both high per pulse energy and high repetition rate to allow for the exploration of revolutionary new science. As I wrote, we were asked by the Department of Energy's Office of Science to explore how we might incorporate the report's recommendations into our plans for the upgrade to the Linac Coherent Light Source (LCLS). We developed a modified plan on how we could accomplish this.
Today, I want to give you more details on this plan for meeting BESAC's recommendations. Let me first caution that what I'm explaining here is just a proposal. No decisions or funding commitments have been made. However, we are beginning to work more closely with the Office of Science and partner with other national laboratories to assess the feasibility, cost and schedule of this proposal, so I want to make sure all of you at SLAC are kept as up to date as possible.
To meet BESAC's recommendations, we have proposed constructing a 4 GeV superconducting linear accelerator in the first third of our existing linac tunnel. Rather than building a new undulator tunnel as was called for in the original design for LCLS-II, we now propose placing two variable-gap undulators in the existing undulator tunnel: a new soft X-ray undulator and a hard X-ray undulator that would replace the existing LCLS undulator. The existing LCLS instruments would be upgraded to take advantage of the new configuration. The undulators, when fed by the superconducting linac, would enable a new class of experiments making full use of the high repetition rate and lower intensity pulses, such as high resolution and multi-dimensional X-ray spectroscopy. It will still be possible to feed the new hard X-ray undulator with electrons from the existing linac to provide pulses with high energy, high intensity and very short duration. The new plan would allow us to incorporate all the capabilities called for in the BESAC subcommittee report and help the U.S. maintain its world leadership in light sources and LCLS to continue to set the standard for cutting-edge scientific discovery.
If the proposal is approved and funded, we will need the help of a number of partners to help make it a reality as soon as possible. We have begun discussions with other national laboratories that have expertise in areas such as superconducting radio frequency, high repetition rate injectors and undulators to explore how we may work together.
We have worked closely with the Office of Science on this proposal but as I said, there is a ways to go before any decisions are made with regard to whether we move forward with these modifications. We need to remain mindful that we continue to live in a very constrained funding environment. Until and unless our response to BESAC’s recommendations moves beyond the proposal stage, it is too early to discuss timing or schedules for this modified plan. However, we strongly agree that the opportunities for exciting science laid out in the BESAC report with such an instrument are unprecedented.
As the report said, such a revolutionary new X-ray facility "will enable world-leading experiments in chemistry, physics, biology, and materials science – experiments that will expand the science frontiers and advance energy science resulting in broad economic and societal benefits." It’s incumbent on us to work with the DOE and with our partners. We have to be prepared if we are given the opportunity to carry out such an exciting project which will transform SLAC as a site and as a laboratory. I will continue to keep you informed as things progress.