N. Hower

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.

Giant high-peak power pulses in the UV OK-4/Duke storage ring FEL using the gain modulator ☆

Abstract 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.

Beam position monitors for Duke FEL storage ring

The Duke FEL storage ring is a 1 GeV electron ring, which is designed for driving UV-VUV free electron lasers. The ring has been in operation since November of 1994 but the beam position monitors (BPMs) were connected and operated just recently. The BPM pick-ups are 4 stripline electrodes. In order to reduce the higher-order-mode loss excited by the stored beam at the BPM pick-up area, the BPM vacuum chamber is designed with 4 grounding strips between the electrodes that have the same diameters as the electrode. This design allows the electron beam to see a much smoother vacuum chamber at the BPM area. The pick-up signals are processed by Bergozs electronic modules, which give X/Y outputs directly. Each BPM has its own process module and 34 modules have been connected to the EPICS control system. The beam orbit now can be displayed and corrected through EPICS in the control room. The system performance and the test data are presented in this paper.

First UV/visible lasing with the OK-4/Duke storage-ring FEL: design and initial performance

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.

Specific features of magnet design for the Duke FEL storage ring

The 1 GeV Duke FEL storage ring is dedicated to drive UV and VUV free electron laser devices. The high brightness and low emittance electron beams needed for these devices demand high performance and tight tolerances on the storage ring magnet lattice. Tight tolerances include close spacing of magnetic elements. We show how combined function magnets are used to eliminate discrete elements and odd shaped end pieces which cause magnetic coupling, saturation and severe undesirable field nonlinearities. Using this scheme we are able to achieve desirable ring dynamic aperture with only minor modification of existing hardware. Also included is a discussion of a non-standard septum magnet with stray field compensation which will be employed by this storage ring. The design, testing procedures, and preliminary results are outlined for this magnet.<<ETX>>

Duke storage ring tune measurements system using razor blade and photomultiplier

We present in this paper the description of the Duke storage ring tune measurements system. An unusual feature of this system is the use of synchrotron radiation to sense oscillation of the electron beam. This system includes a lens, a razor blade placed at the focus and a photomultiplier. Our experience shows that this system can operate on -70 dBm level and detect electron beam oscillations as small as one micron.

Accelerator archeology-the resurrection of the Stanford Mark III electron linac at Duke

In the early 1960s, the Mark III accelerator at the Stanford High Energy Physics Laboratory was used as the prototype test-bed for the SLAC two-mile accelerator. In the mid 1980s, the accelerator was dismantled and a large part of it was transported to the Duke University Free-Electron Laser Laboratory to form the basis of the injector for the 1-GeV Duke Storage Ring. The plan was to use the original accelerator sections and some RF equipment with new magnetic optics, vacuum system, gun and a modern control system. The first 295-MeV portion of the linac is now operational at Duke. The linac currently consists of eleven sections from the old linac with a single-cell RF gun. Our guiding principal has been one of economy and simplicity. We have not attempted to restore the accelerator to its original form, but have added modem components where necessary. We discuss some of the more interesting features of the linac, and how we have given new life to this venerable machine here at Duke.

Critical systems for high peak power storage ring FEL

The Duke storage ring is a facility dedicated for the deep UV free electron laser (FEL) development. It is especially designed for high peak power applications, having a long optical cavity and large energy acceptance. In this paper we describe a FEL gain modulator and optical cavity control system, which are essential for obtaining maximal peak power.

Short-wavelength light sources at Duke storage ring

A 1.1 GeV electron storage ring is now fully operational at the Duke University Free Electron Laser Laboratory. This ring is dedicated to drive a variety of very high brightness short- wavelength sources ranging from UV to gamma-rays. In this paper we present overview of short-wavelength radiation sources including THE OK-4 (XUV FEL, wiggler radiation and inverse Compton (gamma) -rays), X-ray bend-magnets synchrotron radiation, soft X-ray NIST undulator radiation and hard X-ray inverse Compton source. We also describe status of the sources and our short-term and long-term plans.

Unique features of the OK-4/Duke storage ring XUV FEL and monochromatic /spl gamma/-ray source

The OK-4 is the first storage ring FEL operating in the United States. It was commissioned in November, 1996 and demonstrated lasing in the near UV and visible ranges (345-413 nm) with extracted power of 0.15 W. In addition to lasing, the OK-4/Duke FEL generated a nearly monochromatic (1% FWHM) /spl gamma/-ray beam. In this paper we describe the initial performance of the OK-4/Duke storage ring FEL and /spl gamma/-ray source.