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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]

We report the successful operation of an inexpensive, simple, and reliable 2.856 GHz radio frequency photoinjector using a rugged LaB6 cathode and a nitrogen drive laser operating at a wavelength of 337 nm. The cathode was operated at a vacuum of ≈10−8 Torr, and produced excellent beam quality. The device produces a 1 ns long pulse containing 0.1 nC of charge. The photoelectrons have been accelerated to 270 MeV in traveling-wave linear accelerator.

The Duke FEL Lab. requires no less than ten additional 30 mega-watt S-Band RF modulators to satisfy requirements for the storage ring and future linac projects. Ideas focusing on economy of cost and space utilization will be presented along with their current status. These ideas range from rebuilding old SLAC klystrons with commercially available dispenser cathodes, using inexpensive industrial PLC technology for modulator instrumentation and control, to a proposed modulator driving twin klystrons. This last item is especially applicable to reducing cost and space requirements.

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.

RF photoinjectors have gained acceptance as the source of choice for high-brightness electron accelerators, but have been quite expensive to build and difficult to operate. In this paper we describe the successful operation of an inexpensive, simple and reliable RF photoinjector suitable for single bunch injection into storage rings.

This paper documents the repair and reconditioning of an ITT 2960 klystron that had been at atmospheric pressure for eight months due to a leak in the compression seal for the waveguide window. All work was done in the Duke FEL Vacuum Shop by laboratory staff without any external purchases. The reconditioned klystron is currently being operated at full power on the injection linac for the electron storage ring 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.

Since the last Particle Accelerator Conference, the Experimental Physics and Industrial Control System (EPICS) has been utilized for control system development and implementation on several accelerators that have recently been commissioned at the Free Electron Laser Laboratory which is operated under the auspices of the Physics Department at Duke University. The historic Mark III infrared free electron laser formerly located at Stanford University, a recently designed and constructed 280 MeV electron linear accelerator and a 1 GeV storage ring synchrotron are now operating under EPICS control. Commissioning of the new injection linac and the storage ring has gone extremely well. The authors feel that through the employment of a standard controls development environment such as EPICS, considerable amounts of resources, both financial and human, have been saved. The authors note generally positive experiences with EPICS. The highlights of these experiences, as well as some suggestions for future improvements are presented in the body of this report.

A cost effective injection kicker has been developed for the electron storage ring at Duke. Magnet components and driver circuitry are integrated in a modular format that has resulted in a low cost, highly maintainable and upgradeable development system. The driver and magnet can be easily reconfigured from a simple LRC circuit (parallel or series) that provides a pulse approximating a half sinusoid to one utilizing a pulse forming line to provide a more trapezoidal pulse shape. The modular development platform has permitted the kicker to evolve with the storage ring in a way that minimizes further expenditures of time and materials.

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.

Summary Santa Fe Energy Co. (SFEC) installed a double-alkali sulfur dioxide absorber at its Kern River field near Bakersfield, CA. The flue gas desulfurization (FGD) system is designed to remove 95% of the sulfur dioxide from the exhaust of eight oil-fired steam generators when 1.5 wt% sulfur fuel oil is burned. The chemistry of the double-alkali process and the results of compliance and performance emissions testing are presented. Sulfur dioxide emission results are analyzed. Performance tests showed that total outlet sulfur dioxide emissions were 28.7 lbm/hr (0.00363 kg/s). If offset emissions are included, the net sulfur dioxide emissions were 0.22 lbm/hr (0.00003 kg/s). Introduction In Dec. 1977, SFEC contracted with FMC Corp. to install a double-alkali sulfur dioxide absorber serving a group of eight generators consisting of five 62.5-MMBtu/hr (18.44-MW) new steam generators, one 25-MMBtu/hr (7.33-MW) new steam generator, and two 25-MMBtu/hr (7.33-MW) existing steam generators. The absorber was guaranteed to reduce sulfur dioxide emissions to 28.1 lbm/hr (0.00355 kg/s), which wouldcomply with U.S. Environmental Protection Agency (EPA) permitting requirements of 28.14 lbm/hr (0.00355 kg/s) for sulfur dioxide emissions, andcomply with the Kern County Air Pollution Control Dist. permitting requirements of 15 lbm/hr (0.00190 kg/s) when sulfur dioxide emission offsets were included. This paper discusses the double-alkali process, its chemistry, and the results of the performance and compliance emission tests that were conducted in May 1980. Process Chemistry and Equipment Description SFEC, at its Kern River oil field steam drive project, installed eight steam generators with a total maximum rated heat output of 310 MMBtu/hr (90.85 MW). In partial fulfillment of Authority to Construct Air Permits, SFEC contracted with FMC to design and install a double-alkali sulfur dioxide absorber. A description of the double-alkali process and the equipment installed follows. Process Overview The overall process schematic of the double-alkali process is shown in Fig. 1. Flue gas from the steam generators passes through a disk and doughnut-type absorber. Sulfur dioxide is absorbed by a sodium sulfite solution in the absorber. The sodium sulfite is converted to sodium bisulfite. A portion of the solution then is bled from the absorber to a lime reactor tank. Hydrated lime, calcium hydroxide, reacts with sodium bisulfite in the stream from the absorber, forming calcium sulfite and sodium sulfite. Sodium sulfite and calcium sulfite then flow into a thickener tank, where calcium sulfite precipitates. Sodium sulfite solution overflows into a surge tank and then is returned to the sulfur dioxide absorber vessel. The calcium sulfite precipitate is pumped to a rotary vacuum filter where excess moisture is removed, producing a semidry solid filter cake. This semidry filter cake then is disposed in a solid waste disposal site. The two additional vessels shown in the schematic are for chemical storage. One vessel is a pebble lime (CaO) storage silo. Pebble lime is air-blown to a lime slaker where calcium hydroxide is formed. Calcium hydroxide flows into the lime reactor tank. The other vessel shown is a sodium carbonate (Na2CO3) storage tank. JPT P. 2630^