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Solenoids are frequently used for focusing low-energy beams. In this paper, we show how they can serve as multipurpose diagnostics tools to measure various beam parameters, including energy, emittance, the second moments of the transverse distribution, and the beam position and angle with respect to the solenoid’s axis. The energy measurement is based on rotation of the plane of the transverse motion, as opposed to generating dispersion with a dipole. Measurement of the beam trajectory with respect to the solenoid axis is done by analyzing the beam orbit downstream of the solenoid while varying its current. The second moments are calculated by analyzing the beam image on a profile monitor while accounting for the beam rotation caused by the solenoid. We describe in detail the corresponding procedures and the experimental results of these measurements.

Continuous-wave photoinjectors operating at high accelerating gradients promise to revolutionize many areas of science and applications. They can establish the basis for a new generation of monochromatic x-ray free electron lasers, high-brightness hadron beams, or a new generation of microchip production. In this Letter we report on the record-performing superconducting rf electron gun with CsK_{2}Sb photocathode. The gun is generating high charge electron bunches (up to 10 nC/bunch) and low transverse emittances, while operating for months with a single photocathode. This achievement opens a new era in generating high-power beams with a very high average brightness.

A high-current high-brightness electron accelerator for low-energy RHIC electron cooling (LEReC) was successfully commissioned at Brookhaven National Laboratory. The LEReC accelerator includes a dc photoemission gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a superconducting rf booster cavity, and a set of normal conducting rf cavities to provide enough flexibility to tune the beam in the longitudinal phase space. Cooling with nonmagnetized rf accelerated electron beams requires longitudinal corrections to obtain a small momentum spread while preserving the transverse emittances. Electron beams with kinetic energies of 1.6 and 2.0 MeV with a beam quality suitable for cooling were successfully propagated through 100 m of beam lines, including dispersion sections, maintained through both cooling sections in RHIC and used for cooling ions in both RHIC rings simultaneously. The beam quality suitable for cooling RHIC beams was achieved in 2018, which led to the first experimental demonstration of bunched beam electron cooling of hadron beams in 2019.

A fast steering magnet (gain modulator) allows redistribution of free electron laser (FEL) power into a series of high peak power pulses. In this paper, we report experimental study of properties of giant pulses depending on the FEL settings and pulse repetition rate. Localized growth of the electron energy spread, caused by the interaction of the electron beam and the optical pulse, is experimentally demonstrated.

A new method to eliminate beam-uncorrelated background in photonuclear experiments has been developed at the High Intensity Gamma-Ray Source (HIγS). Background suppression of over 3 orders-of-magnitude has been achieved by using a gain modulation technique to generate giant high-peak power (GHPP) pulses in the OK-4/ Duke storage ring FEL. The time structure of these laser pulses was tuned so that their duration was ∼100 μs , repeated every 50 ms . The associated FEL photons were backscattered from 780 MeV electrons to produce linearly polarized 40 MeV γ -rays having the same time structure as the FEL pulses. As an initial test of the technique, a nearly background-free measurement of the analyzing power in the Compton scattering reaction 16 O ( γ → , γ ) 16 O was performed.

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 730 nm using electron beam energies from 220 to 800 MeV. 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.

For a number of years the wavelength of 200 nm was a psychological barrier for FEL oscillators. The progress towards short wavelength was marginal since the OK-4/VEPP-3 storage ring FEL lased at 240 nm in 1988. After 10 years, in 1998, the OK-4/Duke FEL and the NIJI-IV FEL group moved the limit to 217 and 212 nm, respectively. Improvements of the OK-4/Duke storage ring FEL gain above 10% and the use of custom manufactured mirror coatings brought the success in August 1999. The OK-4 FEL lased in the range from 193.7 to 209.8 nm using electron energies from 500 to 800 MeV. In this paper, we present the description of the OK-4/Duke FEL up-grades and the lasing results below 200 nm obtained in August and October of 1999.

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 193.7 nm to 730 nm, 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 1.3 ps 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.

We use the gain modulation technique to generate giant pulses in the OK-4/Duke storage ring FEL for applications requiring high peak power. This technique provides the increase of the peak power by several orders of magnitude. It is also very reliable, predictable and reproducible. The design, the parameters and the gain modulator performance are described. Comparison of expected and measured pulse forms is presented. Application of gain modulator for future harmonic generation experiments is also discussed.

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 2 yr 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 2–58 MeV. During this time, the OK-4 FEL lased in the range from 193.7 to about 730 nm using five sets of mirrors and electron beam energies from 240 to 800 MeV. 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.

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 226–256 nm in April 1998. The OK-4 FEL successfully lased from 217 nm to 235 nm in August 1998. A number of lasing modes with electron energies ranging from 300 to 750 MeV 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.

We report first results from our effort to couple a high resolution photoemission electron microscope (PEEM) to the OK-4 ultraviolet free electron laser at Duke University (OK-4/Duke UV FEL). The OK-4/Duke UV FEL is a high intensity source of tunable monochromatic photons in the 3–10 eV energy range. This tunability is unique and allows us to operate near the photoemission threshold of any samples and thus maximize sample contrast while keeping chromatic berrations in the PEEM minimal. We have recorded first images from a variety of samples using spontaneous radiation from the OK-4/ Duke UV FEL in the photon energy range of 4.0–6.5 eV. Due to different photothreshold emission from different sample areas, emission from these areas could be turned on (or off) selectively. We have also observed relative intensity reversal with changes in photon energy which are interpreted as density-of-state contrast. Usable image quality has been achieved, even though the output power of the FEL in spontaneous emission mode was several orders of magnitude lower than the anticipated full laser power. The PEEM has achieved a spatial resolution of 12 nm.

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 345–413 nm range with extracted power of 0.15 W. 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.

A beam of nearly monochromatic γ-rays was produced via intracavity Compton backscattering in the OK-4/Duke storage ring FEL. The OK-4 FEL operated in the near-UV range (345–413 nm) with electron energies of 260–550 MeV. The energy of the produced γ-rays varied from 3 to 16 MeV. In the near future we plan to increase the energy of the γ-rays to 50 MeV by increasing the electron energy and reducing FEL wavelength. Results from direct measurements of the γ-ray flux and energy resolution (using a 3 mm diameter lead collimator) (Litvinenko et al., Phys. Rev. Lett. 78 (1997) 4569) are very close to our theoretical predictions. The energy resolution of the γ-rays was ∼1%. In this paper we present a comparison of our measurements with theoretical predictions and our plans for future improvements. We discuss upgrades of our system to attain an energy resolution down to 0.1% and to increase the flux. A brief description of the experimental program utilizing the OK-4/Duke monochromatic γ-ray source is presented.

A nearly monochromatic beam of 100% linearly polarized g rays has been produced via Compton backscattering inside a free electron laser optical cavity. The beam of 12.2 MeV g rays was obtained by backscattering 379.4 nm free-electron laser photons from 500 MeV electrons circulating in a storage ring. A detailed description of the g-ray beam and the outlook for future improvements are presented. [S0031-9007(97)03322-X]

The high power infrared free electron laser is under construction at the Novosibirsk Scientific Centre. The goal of this project is to provide a user facility for Siberian Centre of Photochemical Researches. The features of the installation and its status are described.

The NSLS-II Storage Ring provides ultrabright radiation sources with extra-small sizes of the circulating electron beam. The beam dimensions will be monitored with a pinhole camera. In this paper they discuss the possible design and ultimate achievable resolution of the system. Modeling is based on the SRW code as well as numerical calculations using MATLAB.

Coherent radiation from a relativistic electron beam is a valuable way to overcome the present limitations of conventional lasers and synchrotron radiation light sources. The typical scheme has electrons, directly from a linac, in a single-pass interaction with a laser pulse in the presence of a static undulator magnetic field. We demonstrate that a storage-ring free-electron laser can also achieve harmonic generation (down to 36.5 nm), presenting both experimental and theoretical results, and offer a reliable interpretation of the peculiar underlying physical processes involved.

The NSLS-II light source which is a proposed facility to be built at Brookhaven National Laboratory utilizes two synchrotron accelerator rings: the booster and the storage ring (SR). Designing the NSLS-II injector we considered two options for the booster layout, where the rings either a) share the same tunnel, but placed at different horizontal planes or b) booster is located in a separate building. The booster which accepts beam from the linac, accelerates the electron beam to an energy of 3.0 GeV and the beam is extracted to the booster to storage ring (BtS) transport line which transports the beam and injects it into the SR ring. The design procedure for each of the two options of the BtS line and other details about the optics and the magnetic elements of the line are presented in this paper.

We present the design and implementation of the synchrotron light monitor for the NSLS booster, which expands diagnostics capabilities. The system allows measurement of the orbit, beam sizes and coupling of the electron beam along the ramp.

Using a fast steering magnet allowed us to redistribute the average power of a storage ring free electron laser in a series of short pulses with a high peak power. The theory of the operational and experimental results are presented. Good agreement was found between the measured and predicted parameters.

This paper describes project of high brightness cw photoinjector for a powerful IR FEL based on a microtron-recuperator.

At the Duke Free Electron Laser (FEL) Laboratory, there are two FEL machines: the Mark III infrared FEL and the OK-4/Storage Ring, which produces an UV and XUV laser beam as well as gamma rays via Compton backscattering. The recent status of Mark-III machine is described in another paper. Here we will concentrate on the new development of the OK-4/Storage Ring FEL and its performance and capabilities. A brief history of this machine and the future plan are also given in this paper.

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.

The OK-4/Duke storage ring free electron laser (FEL) was commissioned in November, 1996 and demonstrated lasing in the near UV and visible ranges. During one month of operation we performed preliminary measurements of the main parameters of the OK-4 FEL: its gain, lasing power and temporal structure. In addition to lasing, the OK-4/Duke FEL generated a nearly monochromatic 12.2 MeV (gamma) -ray beam. In this paper we describe the status of the main subsystems including the injector system and the ring itself, and discus future and in-progress upgrades to these systems. We also describe the parameters measured to date of the injector, the storage ring, the generated optical laser beams, and the backscattered (gamma) -ray beam.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The OK-4/Duke storage ring FEL was commissioned in November 1996 and demonstrated lasing in the near UV and visible ranges (345 - 413 nm). The OK-4 is the first storage ring FEL with the shortest wavelength and highest power for UV FELs operating in the United States. During one month of operation we have performed preliminary measurements of the main parameters of the OK-4 FEL: its gain, lasing power and temporal structure. In addition to lasing, the OK-4/Duke FEL generated a nearly monochromatic (1% FWHM) 12.2 MeV gamma-ray beam. In this paper we describe the design and initial performance of the OK-4/Duke storage ring FEL. We compare our predictions with lasing results. Our attempt to lase in the deep UV range (around 193 nm) is discussed. The OK-4 diagnostic systems and performance of its optical cavity are briefly described.

A method of extracting radiation from the optical cavity of a free electron laser using an insignificant bend of the electron beam is discussed, noting that the modulation of its longitudinal density needs to be conserved. Modernization of the optical klystron magnetic system of the VEPP-3 storage ring has made it possible to realize an achromatic bend of electrons between two undulators. In such a case the mutual coherence of the radiation from the undulators has been demonstrated by means of Young's interference experiment. The experimental results confirm the possibility of implementing the suggested technique for radiation extraction.

Transverse modes are excited in an optical cavity consisting of two mirrors; these are examined by externally injecting a beam, which is somewhat misaligned with respect to the optical axis of the cavity. By modulating the amplitude of the external radiation at a frequency close to the difference between the transverse modes frequencies of an open optical cavity, a resonance of the intensity amplitude of the radiation stored in the cavity can be observed. Measurements of the amplitude versus frequency dependency allows one to determine the radius of curvature and the reflection losses of the mirrors in use. Measurements performed employing the mirrors for the confocal cavity in the optical klystron on the VEPP-3 storage ring are discussed.

Since 1979, experiments on the storage ring VEPP‐3 with an optical klystron (OK) have been performed at the INP Academy of Sciences of the USSR. In 1979, 1981, and 1983, three different OK magnetic systems based on SmCo permanent magnets undulators were installed at the VEPP‐3 straight section at 6300‐A wavelength. The following gains per pass have been obtained: 0.5% in 1980, 1% in 1982, and 2%–2.5% in 1984. In late 1985, we decided to improve the storage ring VEPP‐3 and develop a dc bypass, a special straight section dedicated for OK operation. The bypass allowed us to install an OK magnetic system of 7.8 m length and significantly increase the gain per pass in March of 1988. The bypass was installed at the storage ring VEPP‐3 on 3 June 1988. We obtained lasing in the red and yellow light spectral range from 5800 to 6900 A with 5%–10% gain per pass. After changing mirrors for new ones with minimum losses at 4150 A, lasing in the violet and near UV spectral range with 3%–6% gain per pass from 4500 to 375...