UW-Madison/SRC, Madison, Wisconsin
MIT, Cambridge, Massachusetts
Funding: Work supported by the University of Wisconsin - Madison. SRC is supported by the U.S. National Science Foundation under Award No. DMR-0537588.
The University of Wisconsin-Madison/Synchrotron Radiation Center and MIT are developing a design for a seeded VUV/soft X-ray Free Electron Laser serving multiple simultaneous users. The present design uses an L-band CW superconducting 2.2 GeV electron linac to deliver 200 pC bunches to multiple FELs operating at repetition rates from kHz to MHz. The FEL output will be fully coherent both longitudinally and transversely, with tunable pulse energy, cover the 5-900 eV photon range, and have variable polarization. We have proposed a program of R&D to address the most critical aspects of the project. The five components of the R&D program are:
- Prototyping of a CW superconducting RF photoinjector operating in the self-inflating bunch mode.
- Development of conventional laser systems for MHz seeding of the FEL, and femtosecond timing and synchronization.
- Address thermal distortion and surface contamination issues on the photon optics.
- Investigate advanced undulator concepts to help reduce facility cost and/or extend performance.
- Perform detailed modeling of all aspects of the FEL, as part of production of a Conceptual Design Report for the FEL facility.
MIT, Cambridge, Massachusetts
UW-Madison/SRC, Madison, Wisconsin
The seeded FEL performance of a number of Wisconsin FEL (WiFEL) undulator lines is described. The experimental design requirements include coverage of a broad wavelength range, rapid wavelength tuning, variable polarization, and variable pulse energy. The beam parameters allow experiments ranging from those requiring low peak power with high average spectral flux to those that need high peak power and short pulse lengths in the femtosecond range. The FELs must also be stable in timing, power, and energy while satisfying constraints on electron beam quality and fluctuations, undulator technologies, and seed laser capabilities. Modeling results are presented that illustrate the design performance over the full wavelength range of the facility.
UW-Madison/SRC, Madison, Wisconsin
SLAC, Menlo Park, California
The microbunching gain of a free-electron laser (FEL) driver is affected by the beam spreader that distributes bunches to the FEL beam lines. For the Wisconsin FEL (WiFEL), analytic formulas and tracking simulations indicate that a beam spreader design with a low value of R56 has little effect upon the gain.
UW-Madison/SRC, Madison, Wisconsin
SLAC, Menlo Park, California
The microbunching gain of the driver for the Wisconsin FEL (WiFEL) is reduced by more than an order of magnitude by using a single-stage bunch compressor rather than a two-stage design. This allows compression of a bunch with lower energy spread for improved FEL performance.