The Australian Synchrotron light Source has 3 variable gap in-vacuum undulators (IVUs) in the storage ring. Since installation, these devices have been the source of strong beam instabilities. These instabilities seem to behave as trapped resonant modes of very high Q and high frequency, although a definite source has not been identified. The presence of these instabilities has necessitated operating at unusually high chromaticity for much of the light source’s operations. More recently transverse feedback has been able to control the instabilities and recent developments in diagnostics have allowed some investigation of the frequency and mode response of these resonances. The results of this investigation will be presented in this paper. IN VACUUM UNDULATORS The Australian Synchrotron storage ring contains two 3-metre long In-Vacuum Undulators (IVUs) (IVU03 and IVU13) that close down to a 6.6 mm pole gap and one 2 metre undulator (IVU05) that closes to 6 mm, supplied in 2006 by NEOMAX Co., Ltd. The undulator period is 22mm in all devices, with 89 and 134 periods in the 2m and 3m devices respectively. The transition taper is a single piece of flexible copper sheet, fixed at each end so that it flexes as the pole gap is altered. Figure 1 shows the general geometry of the magnet array inside the vacuum chamber and Figure 2 is a photo of the transition taper at minimum gap on IVU05.

The Australian Synchrotron light source has recently put in operation its transverse bunch-by-bunch feedback system during user beam mode. Getting to the stage of stable operation has been a long road and this paper will outline the many difficulties that were encountered. Chief among these are the apparent strong, high frequency, vertical resonances that appear when the storage ring’s three in-vacuum undulators are closed to specific gaps. The behaviour of these resonances and their effects on achieving stable feedback operation will be explored in detail.

Preliminary plans are presented for a sub-Angstrom wavelength XFEL at the Australian Synchrotron light source site. The design is based around a 6 GeV x-band linac from the CLIC Project. One of the motivationsfor the design is to have an XFEL co-located on the site with existing storage ring based synchrotron light source. The desire and ability of the Australian photon science community to win beamtime on existing XFELs has lead to this design study to plan for a future machine in Australia. The technology choice is also driven by the Australian participation in the CLIC collaboration and the local HEP community.

In June 2012 the Australian Synchrotron commenced Top-Up Operations for User beamtime. The facility was designed for top-up from the start with a full energy 3 GeV injection system, however top-up only became a priority once the beamline user community had established itself at the new facility in operation since April 2007. New beam diagnostic and equipment protections systems were implemented as part of the move to top-up, including a new injection efficiency monitoring system. The effect of top-up on the beamline data was also tested with each beamline prior to engaging top-up during user runs. Top-up has now been running successfully for one year and the performance statistics from this period will be presented. Top-up operations is a very popular standard mode for user beam and falling into decay mode is now treated almost as a beam dump. MOTIVATION Top-up operations have been shown to improve the performance of beamline due to the stabilisation of heat load on the x-ray optics. Several test runs using top-up were performed to ensure there was unintended degradation of the machine or beamline performance [1]. The thermal shock on the beamline components have been shown to cause shifts in the calibration of the beamline, leading to requirement of time consuming re-tuning of the experiments. During the test runs the injection accelerators also showed an improvement in performance with systems being left in standby mode rather than off for 8 hours at a time. EQUIPMENT PROTECTION AND BEAM DIAGNOSTICS During the planning phase of the top-up operation mode (see also Ref. [2]), several equipment protection and beam diagnostic systems were identified as being necessary for the smooth running of top-up mode. The key conditions were; • injection efficiency above 50%; • energy defining slits in the booster-to-storage ring (BTS) transfer line; • storage ring beam lifetime > 20%; • storage ring beam current > 50 mA; • storage ring magnets within acceptable range; and • storage ring scrapers protecting IDs from beam losses. Injection Efficiency In order to safely perform top-up the injection efficiency has be be above 50%. The injection efficiency is defined as the ratio of the charge measured at the end of the BTS transfer line to the the charge increase measured in the storage ring after several damping times. The BTS measurement is made with a fast current transformer and the storage ring measurement is made with a DCCT. The system monitors the transmission efficiency of the beam all the way through the injection system and into the storage ring and is described in more detail elsewhere [3]. If the injection efficiency falls below the 50% level, top-up operations is suspended and the storage ring defaults back into decay mode. The injection system can then be tested up to the point of extraction from the booster in order to identify any faults and attempt to enter back in to top-up mode. If required the photon shutters can be closed and a fill-on-fill injection attempted to return to above 50% injection efficiency. The injection efficiency became more stabilised after a cycling routine for the BTS magnets was introduced prior to each top-up run. Storage Magnet Settings During the testing phase of top-up mode tolerances of the storage ring magnets were established to find a safe operating range for injecting. The operational settings were based on achieving the correct parameters in the storage rings such as the betatron tunes, orbit, energy acceptance, chromaticity and coupling. These tolerances were also used in the particle tracking procedure in the storage ring lattice model to ensure the beam trajectory during top-up was within specification. A dedicated magnet monitoring system (see Fig. 1) was designed and installed on each sector of the storage ring that would disable injection should the magnet settings fall out of tolerance. Storage Ring Scrapers In order to protect the IDs from lost electron radiation that damages the permanent magnet material, the vertical scrapers in the storage ring were set to be the smallest aperture in the ring. Concentrating the losses at this point where there is additional shielding installed absorbs both stray electrons that are not captured during injection and the beam tails that are lost from the stored beam. MOPEA001 Proceedings of IPAC2013, Shanghai, China ISBN 978-3-95450-122-9 58 C op yr ig ht c ○ 20 13 by JA C oW — cc C re at iv e C om m on sA tt ri bu tio n 3. 0 (C C -B Y3. 0) 02 Synchrotron Light Sources and FELs A05 Synchrotron Radiation Facilities Figure 1: GUI for the top-up interlock and magnet monitoring system.

Small errors in magnet alignment can be a significant source of transverse coupling in a storage ring. Beam offsets in the quadrupole and sextupole magnets at the Australian Synchrotron Light Source were measured using a LOCO based orbit response matrix analysis. The results were used to obtain an estimate of the offset in each magnet and these were then used to guide mechanical alignment efforts. A significant reduction in the uncorrected beam coupling was observed after these corrections, with a corresponding reduction in corrected coupling.

The Australian Synchrotron Light Source (ASLS) uses a 100 MeV linac as the start of the acceleration chain for the injector. The two main accelerating structures of linac are normally fed by independentpulsed klystrons. A recent upgrade to the waveguide system has allowed for a single klystron to power both accelerating structures. While this operation mode delivers a reduced total beam energy, the operation of only a single klystron results in less wear and enhanced robustness against klystron breakdown. Commissioning results of single klystron operation of the linac are shown and future benefits are detailed.

This paper reports the results of an advanced algorithm for the optimization of electron beam parameters in Free Electron Laser (FEL) Linacs. In the novel approach presented in this paper, the system uses state of the art developments in video games to mimic an operator's decisions to perform an optimization task when no prior knowledge, other than constraints on the actuators is available. The system was tested for the simultaneous optimization of the energy spread and the transmission of the Australian Synchrotron Linac. The proposed system successfully increased the transmission of the machine from 90% to 97% and decreased the energy spread of the beam from 1.04% to 0.91%. Results of a control experiment performed at the new FERMI@Elettra FEL is also reported, suggesting the adaptability of the scheme for beam-based control.

The Australian Synchrotron Light Source has enjoyed several years of stable operations with a high degree of availability. It is now time to move towards top-up operations to improve the stability and integrated flux of the photon beam. This paper describes the steps that have been taken and what remains to be done in order to implement top-up injection as the normal operation mode.

Investigations into producing an electron beam with ultralow vertical emittance have been conducted using the Australian Synchrotron 3 GeV storage ring. A method of tuning the emittance coupling (epsilon(y)/epsilon(x)) has been developed using a machine model calibrated through the linear optics from closed orbits method. Direct measurements of the beam emittance have not been possible due to diagnostic limitations, however two independent indirect measurements both indicate a vertical emittance of 1.2-1.3 pm rad (epsilon(y)/epsilon(x) = 0.01%). Other indirect measurements support the validity of these results. This result is the smallest vertical emittance currently achieved in a storage ring.

This paper describes the results of an advanced control algorithm for the stabilization of electron beam energy in a Linac. The approach combines a conventional Proportional–Integral (PI) controller with a neural network (NNET) feed forward algorithm; it utilizes the robustness of PI control and the ability of a feed forward system in order to exert control over a wider range of frequencies. The NNET is trained to recognize jitter occurring in the phase and voltage of one of the klystrons, based on a record of these parameters, and predicts future energy deviations. A systematic approach is developed to determine the optimal NNET parameters that are then applied to the Australian Synchrotron Linac. The system's capability to fully cancel multi-frequency jitter is demonstrated. The NNET system is then augmented with the PI algorithm, and further jitter attenuation is achieved when the NNET is not operating optimally.

This paper describes the results of an advanced control algorithm for the stabilization of electron beam energy in a Linac. The approach combines a conventional Proportional-Integral (PI) controller with a neural network (NNET) feed forward algorithm; it utilizes the robustness of PI control and the ability of a feed forward system in order to exert control over a wider range of frequencies. The NNET is trained to recognize jitter occurring in the phase and voltage of one of the klystrons, based on a record of these parameters, and predicts future energy deviations. A systematic approach is developed to determine the optimal NNET parameters that are then applied to the Australian Synchrotron Linac. The system's capability to fully cancel multi-frequency jitter is demonstrated. The NNET system is then augmented with the PI algorithm, and further jitter attenuation is achieved when the NNET is not operating optimally.

This paper describes the implementation of a neural network hybrid controller for energy stabilization at the Australian Synchrotron Linac. The structure of the controller consists of a neural network (NNET) feed forward control, augmented by a conventional Proportional-Integral (PI) feedback controller to ensure stability of the system. The system is provided with past states of the machine in order to predict its future state, and therefore apply appropriate feed forward control. The NNET is able to cancel multiple frequency jitter in real-time. When it is not performing optimally due to jitter changes, the system can successfully be augmented by the PI controller to attenuate the remaining perturbations. With a view to control the energy and bunch length at the FERMI{at}Elettra Free Electron Laser (FEL), the present study considers a neural network hybrid feed forward-feedback type of control to rectify limitations related to feedback systems, such as poor response for high jitter frequencies or limited bandwidth, while ensuring robustness of control. The Australian Synchrotron Linac is equipped with a beam position monitor (BPM), that was provided by Sincrotrone Trieste from a former transport line thus allowing energy measurements and energy control experiments. The present study will consequently focus on correcting energymore » jitter induced by variations in klystron phase and voltage.« less

This paper describes how the Australian Synchrotron Linac transmission was increased from 42%, up to 85% by adjustment of only the focusing elements along the machine. The systematic approach based on transmission scans as a function of focusing element current combinations, as well as intermediate optimization results is described. The construction of a preliminary PARMELA model is presented. A phase study performed when implementing the model led to a potential transmission increase up to 92% by phase adjustments of the RF elements. This paper gives the systematic approaches that can be used to rapidly increase transmission along a machine containing a series of focusing elements and or, a bunching section. This paper also highlights the importance of diagnostics. Improved diagnostics would help in the optimization and in confirming the model.

Studies using a single high charge electron bunch have been conducted at the Australian Synchrotron to characterise the impedance of the machine at various stages of commissioning and insertion device configuration. This paper will present the results of these studies and show the time evolution of machine impedance with increasing number of insertion devices.

This paper will describe the design features and status of the storage ring RF system for the Australian Synchrotron. The Australian synchrotron completed commissioning in March 2007 and has successfully stored its design beam current of 200mA. An overview of the RF system design and operation parameters will be given, with descriptions of the various control and feedback loops. Performance of the system during commissioning will be described, including some beam based measurements and operational experience.

The Australian Synchrotron(AS) timing system is based on a hybrid design: an Event Generator-Event Receiver (EVG-EVR) system creates the injection trigger and var- ious clocks, while a network of digital delay generators ad- justs pulse delays and widths. This architecture, combined with a storage ring fill pattern monitor, allows the targeting of injection into specific buckets in the storage ring. Never- theless, more demanding needs from the machine and the beamlines require an upgrade of the system. Delay gener- ators will be removed and replaced by EVRs. This will al- low fixed or variable frequencyclocks to be made available to beamlines or to trigger diagnostic hardware in a flexible way, while reducing jitters to below 100 ps.