Laboratory Profile: Jefferson Lab Outlook (Nuclear Physics News)


The outlook for the next few years for the nuclear physics program at Jefferson Lab is quite clear. The final phase of the accelerator commissioning will be completed as quickly as possible, providing the full design current and developing the capability of delivering three simultaneous cw beams with the range of currents, polarization, and energies permitted by the machine's flexible architecture. Commissioning of the Hall A and B experimental equipment will take place in parallel, and the experimental program should be in full swing by the end of 1997. The extraordinary performance of the SRF cavities facilitates evolutionary upgrades of the accelerator that are expected to increase the maximum beam energy available to between 5 and 5.5 GeV; this will both enhance the laboratory's ability to carry out the approved research program and extend the physics "reach" of the facility.

The SRF cavity performance has also provided an opportunity for a "spin-off' effort -- the construction of high-average-power, wave length-tunable free-electron lasers (FELs). Since 1991, high-technology corporations (including DuPont, 3M, IBM, Lucent Technologies, Northrop Grumman, and Xerox) have become increasingly interested in working with the laboratory to develop FELs "driven" by electron beams from sub-GeV SRF linacs. These corporations believe that cost-effectively produced, selectable-wavelength, multi-kilowatt laser light, particularly in the deep ultraviolet, will be profitable for manufacturing uses such as material-surface processing and micromachining. Construction of an initial infrared FEL and of an associated development laboratory began in mid-1996 with a combination of U.S. Navy, state of Virginia, and industrial funding. The Navy will use this first FEL for research on shipboard defense, industrial participants will use it for laser processing technique development, and all participants will use it as a step in further FEL development. The FEL will also use technology derived from the laboratory's work in photocathode polarized electron sources to provide the very high charge, low-emittance bunches that are crucial for good FEL performance.

Over the next decade Jefferson Lab expects to upgrade the accelerator's maximum energy to the 8-10 GeV regime. The large radii of the recirculation arcs permit energies up to 16 GeV before synchrotron radiation fluctuations become important, and the space left in the linac tunnels from the design switch from four to five recirculations (done late in construction to reduce the number of cryo-modules required) allows the addition of five more cryomodules to each linac. These two features of the accelerator layout, together with anticipated evolutionary improvements in cryo-module performance, will lead to an energy of 8-10 GeV. A recent workshop at the laboratory identified many new research possibilities that these higher-energy beams could support, ranging from investigations of the pure quark-like structure of the nucleons and mesons via precise measurement of the quark structure functions to the study of the high-q2 behavior of baryon and meson transition form factors and investigations of hadronization in the duality regime.