G. Mavrogenes

High Charge Picosecond Pulses with a Double Gap Subharmonic Buncher

A new improved bunching system was designed in 1976 and installed in 1981 in the Argonne Electron Linac to replace the one installed in 1972. In the new bunching system, a spiral loaded double gap 12th subharmonic buncher is replacing the previous single gap 6th subharmonic buncher and a one wavelength fundamental frequency traveling wave prebuncher has replaced the previous two wavelength prebuncher. Individual pulses of picosecond (25 to 36) duration and up to 40 ¿ Coulomb in charge, with ¿E/E < ± 0.5% at FWHM over the energy range of 4 to 22 MeV, and a repetition rate from one to 1000 p psec are available to the experimenter on a routine basis. The design and the microwave properties of the cavity are discussed along with the general design of the injector and the results achieved.

A Source for Multiply-Charged Ions

A hot cathode oscillatory discharge source was investigated for d.c. operation to determine the charge-state yield of ions for carbon, nitrogen, oxygen, neon and argon gases and to determine the parameters that effected these yields and source stability. Source principles and construction are similar to that reported by Morosov, Papineau, and Basile.

Conceptual Design of the Argonne 6-GeV Synchrotron Light Source

The Argonne National Laboratory Synchrotron Light Source Storage Ring is designed to have a natural emittance of 6.5 × 10-9 m for circulating 6-GeV positrons. Thirty of the 32 long straight sections, each 6.5-m long, will be available for synchrotron light insertion devices. A circulating positron current of 300 mA can be injected in about 8 min. from a booster synchrotron operating with a repetition time of 1.2 sec. The booster synchrotron will contain two different rf systems. The lower frequency system (38.97 MHz) will accept positrons from a 360-MeV linac and will accelerate them to 2.25 GeV. The higher frequency system (350.76 MHz) will accelerate the positrons to 6 GeV. The positrons will be produced from a 300-MeV electron beam on a tungsten target. A conceptual layout is shown in Fig. 1. Related papers on the Argonne Synchrotron Light Source may be found in references 1-3.

Coaxial Cavities with Beam Interaction

This report considers the use of conventional center conductor gap type cavities as well as the characteristics of several other novel cavities of transverse and crossed coaxial type. The study presents electron orbits for their design and electrical parameters.

Beam-Cavity Interaction Measurements in a DAW Structure

Mode excitations induced by relativistic electron beams have been measured in a disk-and-washer (DAW) structure. The structure had three washers, each with four radial support stems, and half-disk end terminations. The design DAW operating frequency was 1300 MHz, the same as that used to accelerate the electron beam. Both short-pulse (35-ps, 800-Hz, 17-nC/pulse) and long-pulse (10-¿s, 2-A average) conditions were used in the beam-excitation experiments. Mode spectra were measured and identified using low-power techniques employed after the high-power beam measurements. Mode frequency calculations for the complete three-washer geometry were performed using URMEL for up to m = 7. Calculated results are compared with data determined from low-power and beam-driven excitation of the DAW structure.

The Design of the Argonne Double-Sided Microtron

The design study of a double-sided microtron is presented. The result of beam optic calculations in several sector magnet configurations is described. Current limitation by beam backup is discussed.

Investigation of the Disc-and-Washer Structure

About 1971 a proposed accelerating structure was described by the radiotechnical Institute, Moscow, which was intended for proton acceleration in a planned meson factory linac. The structure has several quite useful features and has been subsequently investigated by AECL (Chalk River, Canada), LASL (UC Los Alamos, NM) and Argonne National Laboratory. A sketch of the structure is shown which reveals the origin of the name disc-and-washer structure (DAW). The origin and development of the concept upon which the structure is founded is provided from considerations of a chain of individual TM-01 cavities designed to produce kinetic energy gain to a bunched beam transiting their common axis. It is assumed the cavities are individually excited without inter-coupling; so that for maximum energy gain there is a specific phasing requirement based on the transit time from the previous cavity. Such a system would be very complex to operate and would only be considered in the special case of a few cavities as, for example, the LASL PHERMEX.

Design Study for a 2-GeV Double-Sided Microtron

A design study is presented for a double-sided (two linacs) microtron to accelerate a continuous beam of electrons to energies up to 2-GeV. The external beam can be continuously varied from 500 MeV to 2-GeV. The bunch length is of the order of 2.5 psec and the energy spread is ±100 keV. Preliminary beam blow-up calculations indicate that, using a feedback damping system, an average current of 300 μA can be obtained.

Proposed High Intensity, High Energy Cyclotron for Light and Heavy Ions

Since ions with small charge are produced more copiously from ion sources than are highly charged particles, it is proposed to construct a sector-focused cyclotron of large diameter to obtain heavy ions in much greater number and at higher energies than are available from existing cyclotrons or linacs. In addition, the machine will produce protons at 120 MeV and other light ions in excess of 120 MeV.

A Conceptual Design of a Linac-Stretcher Ring to Obtain a 2-GeV Continuous Electron Beam

In order to obtain a high duty factor, > 100 ¿A 2-GeV electron beam, we have designed a linac-stretcher ring system. The system is an attractive option because it draws heavily on the existing accelerator technology. The linac-stretcher ring consists of a 2-GeV SLAC-type pulsed linac which injects into a storage ring. In between linac pulses, the stored electron beam is to extract resonantly. This design differs from those discussed recently in several important respects. The storage ring includes an RF system whose purpose is to control the beam orbit and rate of extraction from the ring. With an RF system in the ring, the injection scheme consists of a few turns of synchronous transfers of beam between the linac and storage ring.