OUTER-COUPLING SCHEMES AND CODE DEVELOPMENT FOR FREE-ELECTRON LASER OSCILLATORS

Description:

Please Note that a Letter of Intent is due Tuesday, September 05, 2017

PROGRAM AREA OVERVIEW: OFFICE OF BASIC ENERGY SCIENCES

Maximum Phase I Award Amount: $150,000

Maximum Phase II Award Amount: $1,000,000

Accepting SBIR Applications: YES

Accepting STTR Applications: YES

 

The Office of Basic Energy Sciences (BES), within the DOE’s Office of Science, is responsible for current and future user facilities including synchrotron radiation, free electron lasers (FELs), and the Spallation Neutron Source (SNS). This topic is specifically focused on the development of schemes for higher out-coupling efficiency for an X-ray free electron laser oscillator (XFELO) and development of a 3-dimensional simulation code for an XFELO. Grant applications that are not beyond the state-of-the-art nor do not fall within the topic will not be considered.

Grant applications are sought in the following subtopics:

a. Schemes for Higher Out-Coupling Efficiency for an X-ray FEL Oscillator

Self-amplified spontaneous emission (SASE) x-rays pulses are transporting x-ray photon sciences into the femtosecond domain at high-gain, single-pass FELs. An FEL based on a multi-GeV, Continuous-Wave (CW) superconducting RF linac can drastically increase the average brightness and widen the scientific opportunities [1]. A superconducting linac can also enable an X-ray FEL oscillator [2] to be added to the facility, with a minor incremental cost but major scientific benefits, producing 1010 photons of fully coherent pulses with high-spectral purity. The average brightness of an XFELO with 1 MHz bunch repetition rate will then be about 1026 in the standard units (photons /s /mm2 /mr2 /0.1 % BW). This is an order of magnitude higher than that of an SASE FEL from the same linac [3]. The XFELO will complement the SASE, providing opportunities for transformative sciences in inelastic X-ray scattering, x-ray nonlinear optics, X-ray photon correlation spectroscopy, nuclear resonance scattering, etc. [4]. The power density on the intra-cavity crystals in the above XFELO is about 15 kW/mm2. It was shown experimentally that high-purity diamond crystals survive without structural damage under such power level [5].

In the XFELO schemes considered so far, one of the x-ray cavity crystals is thin so that 4% of the intra-cavity x-ray power is extracted. The out-coupling efficiency is therefore 4%.

Since theoretical estimates of the damage threshold are higher by another two-to-three orders of magnitude, an XFELO brightness even higher than 1026 should be feasible at the same repetition rate [6]. This is an important possibility since a higher brightness will open up a wider scientific vista. A straightforward approach is to raise bunch charge, hence the intra-cavity power. The question is whether this can be accomplished without resulting in electron beam degradation and without reaching the damage threshold on diamond crystals.

It might also be possible to device an out-coupling schemes other than transmission through a thin crystal that gives rise to a higher out-coupling efficiency. Higher out-coupling efficiency is attractive since a higher output can be obtained with the same intra-cavity power. There are at least two possible schemes for higher out-coupling efficiency--the electron out-coupling [7] and the use of an unstable cavity for high-power laser [8]. The former was demonstrated for an infrared FEL and the latter is well-known for high-power atomic/molecular lasers.

Proposals are sought to develop practical out-coupling schemes of an XFELO with an efficiency significantly higher than 4%, including but not limited to the two schemes mentioned above—the electron beam out-coupling and the unstable cavity configuration.

Questions – Contact: Eliane Lessner, eliane.lessner@science.doe.gov

b. 3-D X-Ray FEL Oscillator Simulation Codes

High-gain X-ray FELs have been transforming the x-ray photon sciences by providing intense x-ray pulses of unprecedented brightness. Nevertheless, the range and breadth of experimental techniques would be vastly improved if the x-ray beams from the FEL were longitudinally coherent. Two of the most promising schemes for increasing the longitudinal coherence include self-seeding [1,2] and employing the FEL in an oscillator configuration (XFELO) [3], both of which employ certain x-ray optical elements along the FEL. Unfortunately, present FEL simulation codes are not equipped to simulate these optical elements in any real detail, so that the frequency response has to typically be added by an external code, while the angular response and any coupling of the longitudinal and transverse degrees of freedom are typically ignored entirely. This is a significant deficiency, since most recent advances in FEL performance have been supported by extensive simulation efforts that have helped guide further progress. We are looking for an advance that will bring x-ray modeling capabilities to FEL simulation.

Proposals are sought for developing a 3-D-XFELO simulation code that will seamlessly incorporate a wide range of x-ray optical elements, including the full frequency-angular response of Bragg crystals, zone plates, and compound refractive lenses, into a computationally parallel FEL simulation tool. Possible solutions may leverage existing FEL and/or x-ray optics software or employ entirely new platform(s), but must enable fast, efficient simulations of both amplifier and oscillator FEL configurations.

Questions – Contact: Eliane Lessner, eliane.lessner@science.doe.gov

c. Other

In addition to the specific subtopics listed above, the Department invites grant applications in other areas that fall within the scope of the topic description above.

Questions – Contact: Eliane Lessner, eliane.lessner@science.doe.gov

 

References: Subtopic a:

  1. U.S. Department of Energy, Raubenheimer, T., LCLS-II, 2016, LCLS-II-HE FEL Facility Overview, Workshop on Scientific Opportunities for Ultrafast Hard X-rays at High Rep. Rate, SLAC, p. 33. https://portal.slac.stanford.edu/sites/conf_public/lclsiihe2016/Documents/160926%20LCLS-II-HE%20Raubenheimer.pdf
  2. Kim, K.J., Shvyd'ko, Y., and Reiche, S., 2008, A Proposal for an X-ray Free-electron Laser Oscillator with an Energy-recovery Linac, Physical Review Letters, Vol. 100, 244802, p. 4. http://corona.physics.ucla.edu/docserver/paper/file/765/2008-XrayOscillator.pdf
  3. Kolodziej, T., and Maxwell, T., 2016, XFELO Scientific Opportunities Retreat, Synchrotron Radiation News, Vol. 29, Issue 6, pp. 31-33 http://dx.doi.org/10.1080/08940886.2016.1244466
  4. Kolodziej, T., et. al., 2017, Studies of Diamond Endurance to Irradiation with X-Ray Beams of Multi-kW/mm2 Power Density for XFELO Application, XOPT’17, Yokohama, Japan. http://xopt.opicon.jp/
  5. Medvedev, N., Jeschke, H.O., Ziaja, B., 2013, Nonthermal Phase Transitions in Semiconductors Induced by a Femtosecond Extreme Ultraviolet Laser Pulse, New Journal of Physics, Vol. 15, 015016. http://iopscience.iop.org/article/10.1088/1367-2630/15/1/015016/pdf
  6. Matveenko, A.N., et. al., 2007, Electron Outcoupling Scheme for the Novosibirsk FEL, Proceedings of FEL, pp. 204-206, TUAAU02. https://accelconf.web.cern.ch/accelconf/f07/PAPERS/TUAAU02.PDF
  7. Siegman, A.E., 1965, Unstable Optical Resonators for Laser Applications, Proceedings of IEEE, Vol. 53, Issue 3, pp. 277-287. https://www.researchgate.net/publication/2988264_Unstable_Optical_Resonators_for_Laser_Applications

 

References: Subtopic b:

  1. Amann, J., et al., 2012, Demonstration of Self-seeding in a Hard-x-ray Free-electron Laser, Nature Photonics, Vol. 6, pp. 693-698. http://www.nature.com/nphoton/journal/v6/n10/full/nphoton.2012.180.html
  2. Ratner, D., et al., 2015, Experimental Demonstration of a Soft X-ray Self-Seeded Free-electron Laser, Physical Review Letters, Vol. 114, Issue 5, 054801. http://slac.stanford.edu/pubs/slacpubs/16000/slac-pub-16214.pdf
  3. Kim, K-J., Shvyd'ko, Y., and Reiche, S., 2008, A Proposal for an X-ray Free-electron Laser Oscillator with an Energy-recovery Linac, Physical Review Letters, Vol. 100, Issue 24, 244802. https://www.ncbi.nlm.nih.gov/pubmed/18643591

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