S.H. Park

OK-4/DUKE STORAGE RING FEL LASING IN THE DEEP-UV

Abstract In this paper we present the result of the deep-UV lasing with the OK-4/Duke storage ring FEL. The OK-4 FEL was initially commissioned at Duke Free Electron Laboratory in November 1996 followed by a yearlong shutdown. After re-establishing the storage ring operation in early 1998, the OK-4 FEL lasing was demonstrated in the wavelength range of 226–256xa0nm in April 1998. The OK-4 FEL successfully lased from 217xa0nm to 235xa0nm in August 1998. A number of lasing modes with electron energies ranging from 300 to 750xa0MeV have been established to accommodate application researches. Starting September 1998, the coherent deep-UV radiation is used for applications in surgery, cell biology, surface physics, and nuclear physics.

FIRST UV/VISIBLE LASING WITH THE OK-4/DUKE STORAGE RING FEL

Abstract In this paper, we report first lasing results in the near-UV and visible spectral ranges with the OK-4/Duke storage ring – the first storage ring FEL operating in the United States. The OK-4/Duke FEL was commissioned in November 1996 and demonstrated lasing in the 345–413xa0nm range with extracted power of 0.15xa0W. In addition to lasing, the OK-4/Duke FEL generated a nearly monochromatic (1% FWHM) γ-ray beams. In this paper, we describe initial performance of the OK-4/Duke storage ring FEL and γ-ray source in this demonstration experiment. We briefly discuss the present status of the project and its future user program.

Duke storage ring UV/VUV FEL: status and prospects

Abstract A 1.1 GeV electron storage ring dedicated for UV-VUV FEL operation was commissioned last year at the Duke University Free Electron Laser Laboratory [V.N. Litvinenko et al., Commissioning of the Duke storage ring, Proc. 1995 Particle Accelerator Conf., Dallas, TX, May 1–5, 1995]. The XUV FEL project, based on the collaboration of the Duke FEL Laboratory and Budker Institute for Nuclear Physics (Novosibirsk, Russia) is described. The OK-4 UV FEL has arrived from Novosibirsk at the Duke FEL laboratory and is in the process of installation. The main parameters of the Duke Free Electron Laser Laboratory (DFELL) storage ring, the OK-4 optical klystron, and the experimental set-up are presented. The parameters of the UV-VUV FEL are given and possible future upgrades to this system are discussed. We have developed a new macro-particle code for storage ring simulation including all known mechanisms of storage ring FEL interaction. We confirm our expectations on the average and peak power for the OK-4. In addition we have studied a giant pulse mode of operation. A new mechanism of “super-pulse” generation was discovered during these studies. It allows the generation of peak power up to 10 GW using “phase-space” refreshment of the electron beam caused by synchrotron motion [V.N. Litvinenko, B. Burnham, J.M.J. Madey and Y. Wu, Nucl. Instr. and Meth. A 358 (1995) 334].

Commissioning of the Duke Storage Ring

The commissioning of the 1 GeV Duke Storage Ring began in November, 1994 with the demonstration of injection, storage and ramping to 1 GeV at the first attempt. The ring is now operational. The Duke project is unique in that the storage ring and linac were designed, constructed and commissioned by a small new University laboratory, operating on a low budget. The team is comprised of six accelerator physicists and graduate students, eight engineers, and fifteen technicians.

Spatial distribution and polarization of γ-rays generated via Compton backscattering in the Duke/OK-4 storage ring FEL

Abstract Beams of nearly monochromatic γ-rays are produced via intracavity Compton backscattering in the OK-4/Duke storage ring FEL, the high-intensity γ-ray source (HIγS). Presently, HIγS generates γ-ray beams with an energy tunable from 2 to 58xa0MeV and a maximum flux of 5×10 7 γ-rays per second. The γ-rays are linearly polarized with a degree of polarization close to 100% (V.N. Litvinenko, et al., Predictions and expected performance for the VUV OK-5/Duke Storage Ring FEL with variable polarization, Nucl. Instr. and Meth. A, to be published in this proceeding) and they are collimated to pencil-like semi-monoenergetic beams with RMS energy spreads as low as 0.2%. The detailed theoretical and experimental studies of the γ-ray beam quality were conducted during the last two years (S.H. Park, Thesis, Duke University, Durham, NC, USA, 2000). In this paper, we present the theoretical analysis and the experimental results on the spatial distribution and polarization of γ-rays from the HIγS facility.

Performance of the OK-4/Duke storage ring FEL☆

Abstract In this paper, we report measured parameters of the OK-4 FEL driven by the Duke storage ring. The OK-4 FEL was being operated continuously for 2xa0yr in the broad wavelength range for user applications utilising spontaneous and coherent XUV and UV radiation as well as Compton back-scattered γ-rays in the range of 2–58xa0MeV. During this time, the OK-4 FEL lased in the range from 193.7 to about 730xa0nm using five sets of mirrors and electron beam energies from 240 to 800xa0MeV. Our predictions for the OK-4 FEL are compared with measured performance, both in the CW and in the giant pulse mode. We discuss our future plans for the OK-4 FEL operation as well as the construction and commissioning of the OK-5 FEL with helical wigglers.

Power limitations in the OK-4/Duke storage ring FEL ☆

Abstract In this paper, we present results of our experimental and theoretical studies of average power in the OK-4/Duke storage ring FEL. Our theoretical studies are based on the 3D FEL macro-particle model, which includes the local interactions, diffusion, radiation damping and spontaneous radiation. The OK-4/Duke storage ring FEL is operational since 1996 and demonstrated lasing in a wavelength range from 193.7 to 730xa0nm using electron beam energies from 220 to 800xa0MeV. It operated in both CW and giant pulse modes. During this period of time we collected substantial amounts of data regarding the FEL power and electron beam dynamics. We compare selected results on CW lasing with our theoretical predictions based on the rigorous numerical model. We also discuss a number of simplified scaling laws for the FEL gain and power as functions of electron beam energy and current, as well as, the cavity losses.

Performance of achromatic lattice with combined function sextupoles at Duke Storage Ring

The 1 GeV Duke Storage Ring was very successfully commissioned with performance exceeding initial specifications. In this paper we present design and performance data of its unique achromatic lattice with combined function magnets in the ring arcs.

Fourier limited micro-pulses in the OK-4/Duke storage ring FEL.

Abstract The Super-modes are Fourier limited FEL micro-pulses predicted by Dattoli and Renieri in 1980. The OK-4 FEL at Duke, operating in the wavelength range from 193.7xa0nm to 730xa0nm, was the first to observe the Super-modes in a storage ring FEL in 1996. Since 1996, the up-graded diagnostics and improved control of the RF frequency allowed generation of Super-modes on a regular basis and systematic study of them. The Gaussian FEL micro-pulses with 1.3xa0ps RMS duration and Fourier limited RMS linewidth were generated in 1998–1999. In this paper we present the results of our studies and the comparison with theoretical predictions. We also present practical criteria for operating SR FELs with Super-modes.

System for the control and stabilizing of OK-4/Duke FEL optical cavity

The control system of an optical cavity is described. Usage of the piezoelectric actuators and position sensitive photodetectors in this system allows us to reach a resolution at a submicroradian level and to suppress mirror vibrations below 50 Hz.