Here are links to the BESAC subcommittee Agenda, and its Full Report which was unanimously accepted by the full BESAC on Feb. 25, 2003.

Section of the report that pertains to CIRCE:

Far Infrared (Terahertz ) Light Source Facilities

There is considerable scientific interest in high power, short-pulse radiation in the terahertz and far infrared region. This range is important for studying collective excitations in solids, molecular librations and rotations, protein conformational dynamics, superconductor bandgaps, and electronic and magnetic scattering. A facility that provides short pulsed and high average power radiation in this spectral region offers exciting opportunities for probing fast and ultra-fast chemical, physical and biological processes.

Two proposals for facilities that would produce terahertz and far infrared coherent synchrotron radiation in this region were presented. Lawrence Berkeley National Laboratory proposed a Coherent Infrared Center (CIRCE) at the ALS. Thomas Jefferson Laboratory proposed an IR/UV FEL user facility.

While each of these two groups has identified an exciting new potential user community, it is not yet clear whether the scientific communities that might use these facilities have embraced this new technology. The BESAC Subcommittee encourages the DOE to organize national workshops to explore the scientific advantages of research with terahertz radiation at user facilities. Further the BESAC Subcommittee notes that some of the parameters of these coherent synchrotron machines are only comparable to available table-top sources: the energy per pulse, full dc to terahertz coherence, and pulse durations are not much different. However, there are opportunities for significantly higher stability and average power in these machines. Some significant technical hurdles need to be explored more fully. The BESAC Subcommittee noted that trials at BESSY have explored coherent synchrotron radiation (CSR) instabilities in storage rings, but have not yet addressed the issue fully. Research to resolve this issue, as well as to develop the energy recovery technology needed for linac-based sources, must precede any full-scale commitment to a new facility.

The cost of these new light sources should be relatively modest, partly because the level of hazard and the amount of shielding required in this wavelength range is far less than with present sources. Therefore, it should be possible to develop these sources without the kind of full-scale new facilities requests needed for X-ray or neutron facilities. The BESAC Subcommittee recommends that issues related to instrument development and sample environment be more carefully examined to enhance the likelihood of success in this area. It is also important to more completely document the science demand for such a national user facility dedicated to this frequency range and to have the national community assist in deciding the type of facility that best serves its needs.

Report of the Comittee: Full report (PDF) LSCN-GE-02

Highlights of the report:

• "The group is to be commended for its excellent work in investigating coherence effects. It is a prime example of the quality and value of Laboratory Directed Research and Development (LDRD) funding."
• "Emphasis should be focused on the source operating in coherent mode."
• "There should be a concerted effort to ... exploit noise reduction afforded by synchronous detection."