G. Swift

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.

Commissioning of the booster injector synchrotron for the HIGS facility at duke university

A booster synchrotron (Duke booster) has been built and recently commissioned at Duke University Free Electron Laser Laboratory (DFELL) as part of the High Intensity Gamma-ray Source (HIGS) facility upgrade. HIGS is collaboration between the DFELL and Triangle Universities Nuclear Laboratory (TUNL). The booster provides top-off injection into the Duke FEL storage ring in the energy range of 0.24 -1.2 GeV. When operating the Duke storage ring to produce high energy Compton gamma ray beams above 20 MeV, continuous electron beam loss occurs. The lost electrons are replenished by the booster injector operating in the top-off mode. The present operational injection and extraction rate of the machine allows us to routinely replenish up to 5-108 electrons per second. The compactness of the booster posed a challenge for its development and commissioning. The booster has been successfully commissioned in 2006. This paper reports experience of commissioning and initial operation of the booster.

Project of Booster synchrotron for Duke FEL storage ring

In this paper we present a project of a Booster-injector for the Duke FEL storage ring. The Booster will provide full energy injection into the storage ring at energy from 0.25 to 1.2 GeV. The Duke storage ring FEL (SR FEL) operates in lasing mode with 193-700 nm wavelength range. This range will be extended into VUV in near future. The geometry of the Duke SR FEL provides for head-on collision of e-beam and FEL photons. This mode of operation is used for High Intensity /spl gamma/-ray Source (HI/spl gamma/S facility) generating intense beams of /spl gamma/-rays from 1 MeV to about 200 MeV (currently from 2 MeV to 58 MeV). Generation of /spl gamma/-rays with energy exceeding 20 MeV causes the loss of electrons, which will be replaced by new electrons from the Booster, operating in a top-up mode. The Booster has a robust FODO lattice. In this paper we present the design of the Booster and its magnetic elements. For 2D and 3D magnet design of the magnetic elements we used MERMAID 2D/3D code.

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.

Status of the booster synchrotron for Duke FEL storage ring

In this paper we present current status of the Booster Synchrotron for the Duke FEL storage ring. The Booster which is recently under design, fabrication and construction, will provide full energy injection into the storage ring at energy from 0.3 to 1.2 GeV. The Duke storage ring FEL (SR FEL) operates in lasing mode with 193-700 nm wavelength range. The geometry of the Duke SR FEL provides for interacting head-on collision of e-beam and FEL photons. This mode of operation is used to generate intense beams of /spl gamma/-rays from 2 MeV to about 200 MeV (currently from 2 MeV to 58 MeV). Generation of /spl gamma/-rays with energy exceeding 20 MeV causes the loss of electrons, which will be replaced by injection from the Booster operating in a top-off mode. The paper presents design and status for elements of magnetic system and vacuum system, as well as design and parameters of fast extraction kicker with 11 nS pulse duration. All these element are designed and will be fabricated by Budker Institute of Nuclear Physics, Novosibirsk, Russia.

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.

Status of Mark III FEL

Current status of Mark III free electron laser and its upgrades are presented.