such a facility would provide information on whether additional user facilities might be needed subsequently. Two relevant issues that should then be considered are the quality of the proposed science that cannot be accommodated by a single facility and the existence of alternative infrared sources such as laboratory-sized far-infrared FELs.
Free electron lasers already exist in the far-infrared region, even as user facilities, and therefore uncertainty about the technical requirements and cost of establishing a far-infrared free electron laser facility is relatively low. The relatively modest accelerator and undulator requirements mean that a user facility might be built for several million dollars using existing technology.
There is some promise that further development will lead to a significantly less expensive free electron laser that could be used by a single academic department or perhaps an individual investigator.
A photocathode electron source may increase the utility of a user facility both because of the free electron laser's improved performance and because the laser used to excite the photocathode could also serve as a second, synchronous photon source for pump-probe experiments.
A far-infrared free electron laser user facility capable of producing picosecond pulses should be established. Such a facility could be a new construction or a modification of an existing facility. The committee believes that the scientific opportunity justifies the establishment of such a facility.
Such a facility should have a means of synchronizing a second tunable laser with the free electron laser for use in pump-probe experiments as well as a means for selecting single picosecond pulses from the free electron laser. One method of doing this involves using a photocathode electron gun.
The current research and development directed toward the production of a compact free electron laser that could be purchased and operated by a single academic department or individual investigator should be continued.
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