The Jefferson Lab 1 kW IR FEL

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2000

Recently, the JAERI superconducting RF linac based FEL has been successfully lased to produce 0.36 kW of FEL light using a 100 kW electron beam in quasi-continuous wave operation. A 1 kW class laser is our present program goal, and will be achieved by improving the optical out coupling in the FEL optical resonator, the electron gun, and the electron beam optics in the JAERI FEL driver. Our next 5-year program goal is to produce a 100 kW-class FEL laser and multi-MW class electron beam in average, quasi-continuous wave operation. Conceptual and engineering design options needed for such a very high-power operation will be discussed to improve and to upgrade the existing facility. 2000 Elsevier Science B.V. All rights reserved.

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), 2003

The use of energy recovery provides a potentially powerful new paradigm for generation of the charged particle beams used in synchrotron radiation sources, high-energy electron cooling devices, electron-ion colliders, and other applications in photon science and nuclear and high-energy physics. Energy-recovering electron linear accelerators (called energy-recovering linacs, or ERLs) share many characteristics with ordinary linacs, as their six-dimensional beam phase space is largely determined by electron source properties. However, in common with classic storage rings, ERLs possess a high average-current-carrying capability enabled by the energy recovery process, and thus promise similar efficiencies. We discuss the concept of energy recovery and its technical challenges and describe the Jefferson Lab (JLab) Infrared Demonstration Free-Electron Laser (IR Demo FEL), originally driven by a 35-48-MeV, 5-mA superconducting radiofrequency (srf) ERL, which provided the most substantial demonstration of energy recovery to date: a beam of 250 kW average power. We present an overview of envisioned ERL applications and a development path to achieving the required performance. We use experimental data obtained at the JLab IR Demo FEL and recent experimental results from CEBAF-ERa GeV-scale, comparatively low-current energy-recovery demonstration at JLab-to evaluate the feasibility of the new applications of high-current ERLs, as well as ERLs' limitations and ultimate performance.

Japanese Journal of Applied Physics, 2002

A Free Electron Laser (FEL) called the IR Demo is operational as a user facility at Thomas Jefferson National Accelerator Facility in Newport News, Virginia, USA. It utilizes a 48 MeV superconducting accelerator that not only accelerates the beam but also recovers about 80% of the electron−beam power that remains after the FEL interaction. Utilizing this recirculation loop the machine has recovered cw average currents up to 5 mA, and has lased cw above 2 kW output at 3.1 microns. It is capable of output in the 1 to 6 micron range and can produce ~0.7 ps pulses in a continuous train at ~75 MHz. This pulse length has been shown to be nearly optimal for deposition of energy in materials at the surface. Upgrades under construction will extend operation beyond 10 kW average power in the near IR and produce multi-kilowatt levels of power from 0.3 to 25 microns. This talk will cover the performance measurements of this groundbreaking laser, scaling in near-term planned upgrades, and highlight some of the user activities at the facility.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011

Jefferson Lab operates a pair of oscillator-based continuous-wave Free Electron Lasers (FELs) as a linac-based next generation light source with pulse repetition rates up to 75 MHz. The facility uses an energy recovered linac design for efficiency of operation. Recent advances in superconducting technology have been implemented to produce higher acceleration gradients in the linac to produce higher electron beam energies that result in higher photon energies. Thus, while the system originally operated only in the IR, it now covers the photon energy range from the UV to THz, with harmonics upwards of 10 eV with an average spectral flux that is calculated to be 5 × 10 17 photons/sec/0.1%BW. Pulse lengths are in the sub-picosecond regime, and the 14 fully coherent nature of the source, both transversely and longitudinally, results in peak and 15

Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366)

The driver for Jefferson Lab's kW-level infrared free-electron laser (FEL) is a superconducting, recirculating accelerator that recovers about 75% of the electron-beam power and converts it to radiofrequency power. In achieving first lasing, the accelerator operated "straight-ahead" to deliver 38 MeV, 1.1 mA cw current through the wiggler for lasing at wavelengths in the vicinity of 5 µm. Just prior to first lasing, measured rms beam properties at the wiggler were 7.5 ±1.5 mm-mr normalized transverse emittance,26±7 keV-deg longitudinal emittance, and 0.4±0.1 ps bunch length which yielded a peak current of 60±15 A. The waste beam was then sent directly to a dump, bypassing the recirculation loop. Stable operation at up to 311 W cw was achieved in this mode. Commissioning the recirculation loop then proceeded. As of this Conference, the machine has recirculated cw average current up to 4 mA, and has lased cw with energy recovery up to 710 W.

arXiv (Cornell University), 2000

An upgrade of the Jefferson Lab IR FEL [1] is now under construction. It will provide 10 kW output light power in a wavelength range of 2-10 µm. The FEL will be driven by a modest sized 80-210 MeV, 10 mA energy-recovering CW superconducting RF (SRF) linac. Stringent phase space requirements at the wiggler, low beam energy, and high beam current subject the design to numerous constraints. These are imposed by the need for both transverse and longitudinal phase space management, the potential impact of collective phenomena (space charge, wakefields, beam break-up (BBU), and coherent synchrotron radiation (CSR)), and interactions between the FEL and the accelerator RF system. This report addresses these issues and presents an accelerator design solution meeting the requirements imposed by physical phenomena and operational necessities.

1992

The CEBAF superconducting linac is capable of accelerating electron beams suitable for driving high-power free-electron lasers. The 45 MeV injector linac with a 6 cm period wiggler can produce kilowatt output powers ,of infrared light (3.6-17 #Lm), while the 400 MeV north linac can produce ultraviolet light ('" 200 nm) at similar powers. The FELs require the addition of a high-peak intensity electron source ('" 60 A peak current) and extraction beam lines to wigglers with appropriate electron and photon optics. FEL operation is compatible with simultaneous baseline CEBAF nuclear physics operation. A design for a CEBAF-based FEL facility has been developed. The current status of the FEL project is reported.

Le Centre pour la Communication Scientifique Directe - HAL - memSIC, 2022

In this paper we'll describe the status of the FAST-GREENS experimental program where a 4 meter long strongly tapered helical undulator with a seeded prebuncher is used in the high gain TESSA regime to convert a significant fraction (up to 10%) of energy from the 220 MeV electron beam from the FAST linac to coherent 515 nm radiation. We'll also discuss the longer term plans for the setup where by embedding the undulator in an optical cavity matched with the high repetition rate from the superconducting accelerator (3 MHz or 9 MHz), a very high average power laser source can be obtained. Eventually, the laser pulses can be redirected onto the relativistic electrons to generate by inverse compton scattering a very high flux of circularly polarized gamma rays for polarized positron production.

Reviews of Modern Physics, 2002

Free-electron-laser (FEL) oscillators have only recently achieved their original promise as producers of high-power, short-wavelength, tunable radiation. Room-temperature accelerator systems have generally had limited duty factor due to excessive Ohmic losses on cavity walls. The application of superconducting radio-frequency (SRF) technology has now permitted an increase by more than two orders of magnitude in FEL average power due just to increased duty factor in continuous-wave operation. A concurrent technical development that leveraged the high efficiency of SRF linacs was the demonstration of beam energy recovery while lasing. This leads to high overall efficiency and scales favorably to systems with even higher average power. This paper will discuss the issues relating to high-average-power light sources. The planned and demonstrated performance of several FEL facilities will illustrate the sizable advantages that superconducting radio frequency offers for high average flux and output multiplexing for several simultaneous users. An important new class of light sources, energy-recovering linacs, will be introduced. I.

Journal of Physics: Conference Series, 2013

Jefferson Lab operates a superconducting energy recovered linac which is operated with CW RF and which powers oscillator-based IR and UV Free-Electron Lasers (FELs) with diffraction limited sub-picosecond pulses with >10 13 photons per pulse (1.0%BW) at pulse repetition frequencies up to 75 MHz. Useful harmonics extend into the vacuum ultraviolet (VUV). Based on FEL model calculations validated using this facility, we have designed both an oscillator-based VUV-FEL that would produce 6 10 12 coherent (0.5% BW) 100 eV photons per pulse at multi-MHz repetition rates in the fundamental, and a dual FEL configuration that would allow simultaneous lasing lasing at THz and UV wavelengths. The VUV-FEL would utilize a novel high gain, low Q cavity, while the THz source would be an FEL oscillator with a short wiggler providing diffraction limited pulses with pulse energy exceeding 50 microJoules. The THz source would use the exhaust beam from a UV FEL. Such multiphoton capabilities would provide unique opportunities for out of equilibrium dynamical studies at time-scales down to 50 fs. The fully coherent nature of all these sources results in peak and average brightness values that are many orders of magnitude higher than storage rings.