Yaw-Ren Tan

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.

Differences in Current Dependent Tune Shifts Measured by Direct or ORM Based Methods

The change in the tunes as a function of total beam current is a well documented effect and has been attributed to quadrupole like self induced wakefields. Theoretical models presented by others have utilised direct methods (spectrum analyser) to measure the tunes in the analysis. In this report we shall present observations that show the ORM method, Linear Optics from Closed Optics (LOCO), and direct methods have significantly different tune gradients. The different tune gradients is attributed to the static (ORM) and dynamic (direct) nature of the measurements where in the static case the vacuum chamber is to be considered as a thin wall while in the dynamic case the vacuum chamber wall is to be considered as a thick wall. INTRODUCTION A common method of calibrating storage rings is by the technique of linear optics from closed optics (LOCO) [1] that uses an orbit response matrix (ORM) and dispersion measurements as inputs. The method has been proven as a reliable method of determining the linear optics of a storage ring. During a study using LOCO to measure the impedance effect of the in-vacuum undulators (IVUs), the tune gradients from LOCO based analysis were different to the measured tune gradients and could not be explained. This difference in gradient is shown Figure 1. When three of the IVUs were closed to a gap of 7 mm both the measure and LOCO derived tune gradients change, indicating that both are measuring the impedance effect resulting from closing the IVU gap. To resolve the discrepancy we compared three different tune measurements: swept spectrum analyser (SA) connected to a stripline to excite the beam and a button beam position monitor (BPM) to measure the response, Fourier analysis of turn-by-turn (TbT) data from the BPM system after a fast kicker excites the beam and measuring the notch in the beam spectrum with the bunch-by-bunch (BbB) feedback system in operation. The three different tune measurements were in agreement to within the resolution of the tunes (σνx/y = 1.5 × 10−4). With LOCO we tried: ORMs with different amplitudes, unipolar vs bipolar excitation, changed the chromaticity, changed the weighting of the dispersion function in LOCO, disabled the BbB feedback system, reviewed the model, changed fit parameters. At the conclusion, the investigations indicated that both measurements are valid results. LASLETT TUNE SHIFT MODEL In electron storage rings, self-induced wakefields do result in tune shifts that are dependent on the average beam ∗ eugene.tan@synchrotron.org.au 0 50 100 150 200 Current (mA) 0.286 0.287 0.288 0.289 0.29 0.291