M. J. Boland

Compton Scattering from the Deuteron and Extracted Neutron Polarizabilities

Differential cross sections for Compton scattering from the deuteron were measured at MAX-Lab for incident photon energies of 55 and 66 MeV at nominal laboratory angles of 45 degrees, 125 degrees, and 135 degrees. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and the difference of the isospin-averaged nucleon polarizabilities, alpha(N)+beta(N)=17.4+/-3.7 and alpha(N)-beta(N)=6.4+/-2.4 (in units of 10(-4) fm(3)), have been determined. By combining the latter with the global-averaged value for alpha(p)-beta(p) and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of alpha(n)=8.8+/-2.4(total)+/-3.0(model) and beta(n)=6.5-/+2.4(total)-/+3.0(model), respectively.

Near-threshold measurement of the He-4(gamma,n) reaction

A near-threshold He-4(gamma, n) cross-section measurement has been performed at MAX-lab. Tagged photons from 23 < Ey < 42 MeV were directed toward a liquid He-4 target, and neutrons were detected by time-of-flight in two liquid-scintillator arrays. Seven-point angular distributions were measured for eight photon energies. The results are compared to experimental data measured at comparable energies and Recoil-Corrected Continuum Shell Model, Resonating Group Method, and recent Hyperspherical-Harmonic Expansion calculations. The angle-integrated cross-section data are peaked at a photon energy of about 28 MeV, in disagreement with the value recommended by Calarco, Berman, and Donnelly in 1983.

Success and failure of dead-time models as applied to hybrid pixel detectors in high-flux applications

Detector response functionals are found to have useful but also limited application to synchrotron studies where bunched fills are becoming common. By matching the detector response function to the source temporal structure, substantial improvements in efficiency, count rate and linearity are possible.

Applying Frequency Map Analysis to the Australian Synchrotron Storage Ring

The technique of frequency map analysis has been applied to study the transverse dynamic aperture of the Australian Synchrotron Storage Ring. The results have been used to set the strengths of sextupoles to optimise the dynamic aperture. The effects of the allowed harmonics in the quadrupoles and dipole edge effects are discussed.

LOCO at the Australian Synchrotron

LOCO has been used during the commissioning of the Australian Synchrotron storage ring with a number of benefits. The LOCO (linear optics from close orbits) method compares a model response matrix to the real machine response matrix. Using this approach we are able to adjust the machine to match the ideal model. Results presented here show that LOCO has provided a high degree of control over a wide range of machine parameters.

Storage ring turn-by-turn BPMS at the Australian Synchrotron

The Australian synchrotrons Storage Ring is equipped with a full compliment of 98 Libera electron beam position processors from I-tech (EBPPs) [1]. The EBPPs are capable of measuring beam position data at turn-by-turn (TBT) rates and have long history buffers. TBT data from the EBPPs has been used to determine the linear optics of the storage ring lattice using techniques developed at other facilities. This is a useful complement to other methods of determining the linear optics such as LOCO. Characteristics of the EBPPs such as beam current dependence have been studied during commissioning and will also be presented.

Final commissioning results from the injection system for the Australian Synchrotron project

Danfysik has delivered a full-energy turn-key injection system for the Australian Synchrotron. The system consists of a 100 MeV linac, a low-energy transfer beamline, a 130 m circumference 3-GeV booster, and a high energy transfer beamline. The booster lattice was designed to have many cells with combined-function magnets (dipole, quadrupole and sextupole fields) in order to reach a very small emittance. The injection system has been commissioned and shown to deliver a beam with an emittance of less than 30 nm, and currents in single- and multi-bunch mode in excess of 0.5 and 5 mA, respectively, fulfilling the performance specifications. The repetition frequency is 1 Hz. Results from the commissioning of the system will be presented.

Lifetime contribution measurements at the Australian Synchrotron

There are always a number of factors that contribute to the lifetime of a stored particle beam. Measurements presented here show the relative importance of these effects during the commissioning of the Australian synchrotron storage ring.

Preliminary studies for top-up operations at the Australian Synchrotron

The Australian Synchrotron is now a fully commissioned synchrotron light source providing beam for users [1]. With the facility now fully operational, the next major advancement in machine operations will be top-up mode. The advantages of running in a dynamic top-up mode are well documented by other third generation light sources (see for examples references [2, 3, 4]) ; in broad terms it leads to a better quality beam for some users, and better experimental results. An overview will be given of the top-up runs that have been conducted and the instrumentation that was used. It has been demonstrated that top-up operation is possible, however improvements in injection efficiency and beam stability during injection are required before this can become a routine mode of operation.

Measurements of impedance and beam instabilities at the Australian Synchrotron

In this paper we present the first measurements of machine impedance and observed beam instabilities at the Australian Synchrotron. Impedance measurements are made by studying the single bunch behaviour with beam current, using optical and X-ray diagnostic beamlines. An observed coupled-bunch instability, its cause and cure is also discussed.