E. Crosbie

FEL development at the Advanced Photon Source

Construction of a single-pass free-electron laser (FEL) based on the self-amplified spontaneous emission (SASE) mode of operation is nearing completion at the Advanced Photon Source (APS) with initial experiments imminent. The APS SASE FEL is a proof-of-principle fourth-generation light source. As of January 1999 the undulator hall, end-station building, necessary transfer lines, electron and optical diagnostics, injectors, and initial undulators have been constructed and, with the exception of the undulators, installed. All preliminary code development and simulations have also been completed. The undulator hall is now ready to accept first beam for characterization of the output radiation. It is the project goal to push towards full FEL saturation, initially in the visible, but ultimately to UV and VUV, wavelengths.

Injection and Acceleration of Protons in the Zero Gradient Synchrotron (ZGS) by Stripping H Ions

The booster injector program for the ZGS requires the stripping of H ions at 50 MeV as the source of protons in the booster accelerator. 1, 2 Using the former Cornell 2. 2 GeV electron synchrotron as a prototype booster, the injection of protons by stripping negative hydrogen ions in a poly-paraxylene thin film has already been demonstrated at the ZGS. 3 A brightness multiplication factor of 100 has been achieved. The limiting factor is the scattering of the circulating protons in the stripping foil.

A 1500-MeV Fixed-Field Alternating-Gradient Synchrotron for a Pulsed-Spallation Neutron Source

The first conceptual design of the FFAG for ASPUN was an 1100-MeV, 20-sector machine with an injection radius of 17.5 m and an extraction radius of 18.75 m. The conceptual design currently under study has a higher extraction energy, a larger average radius, but still has 20 sectors. The current interest in higher extraction energy is stimulated by calculations that indicate that the useful neutron production per incident proton is still increasing proportionally up to 1500 MeV. The larger radius also matches existing buildings at Argonne that could be made available for the facility. 11 refs., 4 figs., 3 tabs.

The Design of the Zero Gradient Synchrotron Booster-II Lattice

A 500 MeV booster has been designed at the Argonne National Laboratory to increase the beam intensity from the Zero Gradient Synchrotron (ZGS). Many turns of H ions from the 50 MeV lirac will be injected into the booster and stripped to H so that the ring will contain the maximum useful charge in each booster pulse. Several booster pulses will be injected into the ZGS to form one ZGS pulse. This machine is now under construction.

Effects of errors on the dynamic aperture of the Advanced Photon Source storage ring

The individual tolerance limits for alignment errors and magnet fabrication errors in the 7-GeV Advanced Photon Source storage ring are determined by computer-simulated tracking. Limits are established for dipole strength and roll errors, quadrupole strength and alignment errors, sextupole strength and alignment errors, as well as higher-order multipole strengths in dipole and quadrupole magnets. The effects of girder misalignments on the dynamic aperture are also studied. Computer simulations are obtained with the tracking program RACETRACK, with errors introduced from a user-defined Gaussian distribution, truncated at +or-5 standard deviation units.<<ETX>>

Nonlinear resonance studies at the synchrotron radiation center, Stoughton, Wisconsin

A single bunch is stored in ALADDIN at 800 MeV. The coherent oscillations produced by a fast kicker are recorded for each turn at two horizontal position detectors separated by pi /2 in phase. Displaying the recorded positions on horizontal and vertical axes produces a phase plot of the coherent motion. Resonances are produced by adding a controlled amount of sextupole field. The results are compared with computer simulations. To adequately describe the behavior near unstable fixed points the finite size of the beam must be taken into account.<<ETX>>

Effect of Synchrotron Radiation in the Proposed 4-GeV Argonne Microtron

Synchrotron radiation in the sector magnets of the 4 GeV microtron designed at the Argonne National Laboratory produces a small but noticeable distortion of the closed orbits of the system and a very significant growth of the horizontal and longitudinal phase space emittances. Because of the small apertures in the three 25 meter linacs, it is important that the expected growth of the beam be calculated as accurately as possible. The dynamical problem has been solved using a computer program which follows the motions of individual electrons in the four dimensional horizontal and longitudinal phase space as they are accelerated in the system. In this paper the authors call attention to the fact that there are 3 long 28 m linac sections separated by sector magnets from 3 dispersion sections where the orbits for different energies are separated. The interaction of the linac rf systems with the synchrotron energy loss in the sector magnets produces different orbit effects in the downstream and upstream linac sector magnets. The average synchrotron radiation energy loss per sector magnet is given.

High Energy Polarized Deuterons at the Argonne National Laboratory Zero Gradient Synchrotron

Modifications made on the ZGS to allow the acceleration of polarized deuterons and the operational experiences with the first production run with this beam are described.

Computer-Based Visualization and Manipulation of Orbit Warps in the Zero Gradient Synchrotron (ZGS)

The low energy orbit warps in the ZGS are corrected by eight current-regulated single-turn kicker windings. The currents regulated in these coils can be set individually by the operators through a central digital control system. Since large first harmonic warps are produced by small current changes in single coils, blind, individual adjustment of the eight currents is seldom productive. This paper describes a computer program and interactive graphic display system which allow accelerator operators to visualize the effects of single or multiple kicker coil current changes. The display provides numeric as well as graphic representation of the orbit warp produced. Localized orbit bumps can be inserted by specifying location and size. The program can be used for offline visualization purposes only, or optionally the desired currents can be introduced immediately by the computer.

Effects of construction and alignment errors on the orbit functions of the Advanced Photon Source Storage Ring

The orbit functions for the Advanced Photon Source storage ring have been studied using the simulation code RACETRACK. Nonlinear elements are substituted into the storage ring lattice to simulate the effects of construction and alignment errors in the quadrupole, dipole, and sextupole magnets. The effects of these errors on the orbit distortion, dispersion, and beta functions are then graphically analyzed to show the RMS spread of the functions across several machines. The studies show that the most significant error is displacement of the quadrupole magnets. Further studies using a three-bump correction routine show that these errors can be corrected to acceptable levels.<<ETX>>