ANL, Argonne, USA
Presently, APS utilizes one simple canting scheme to separate radiation generated by two insertion devices (IDs) located in the same ID straight section. This scheme is based on triangular horizontal orbit bump with one corrector located between the IDs and orbit distortion limited to the ID straight section only. However, this scheme does not allow for switching between the upstream and downstream devices, nor does it allow for one beamline to accept the combined radiation of both devices. Yet these capabilities are being requested for the future APS Upgrade. In this paper, we describe more advanced canting schemes that allow for these capabilities. The main complication here is that the orbit distortion is required to go through the storage ring magnets thus generating optics errors, which have to be corrected.
ANL, Argonne, USA
Insertion devices (IDs) in light sources generally produce small dipole perturbations on the stored beam of a storage ring light source, which is usually compensated by orbit correction. Tougher orbit stability requirements for the Advanced Photon Source Upgrade have led us to revisit the requirements of these magnetic-field errors. When including the effect of orbit correction (including fast orbit feedback), we realized that the field-error requirements change from a limit in absolute values of magnetic-field error integrals to that of rates of change in magnetic-field error integrals. Some modeling of the combined effect of ramping the strength of an ID with orbit correction will be presented. This new thinking has the potential of greatly alleviating the tuning requirements of insertion devices of all types.
ANL, Argonne, USA
One of the unique features of the Advanced Photon Source is operation with a small number of intense bunches – standard operating mode has twenty four 16-nC bunches, while in a special operating mode one of the bunches has a charge of 60 nC. Such high single bunch currents are achieved by a combination of high operational chromaticity and transverse bunch-by-bunch feedback. In the near future, more narrow-gap insertion device vacuum chambers will be installed, which will increase impedance of the storage ring and make operation with high single-bunch current more problematic. Simulations exist that quantify the effect of increased impedance on the APS single-bunch accumulation limit; however, no experimental verification has been performed yet. In this paper, we will present our first measurement of the single-bunch accumulation limit as a function of effective impedance. Different impedance values were achieved by changing storage ring beta functions.
ANL, Argonne, USA
A multi-bend-achromat (MBA) extreme low-emittance lattice has been proposed for the future APS Upgrade. Due to its small dynamic aperture, the traditional injection scheme must be replaced with bunch train swap-out scheme. Several options were considered for the creation of a high-charge bunch train from the injector, and we selected an option that builds the bunch train in the particle accumulator ring (PAR). This option enables both single-bunch mode, which is necessary to support current APS operation, and bunch-train mode. This report provides a description of the injection process, simulation results, and specifications of injector timing, kicker, and rf subsystems.
ANL, Argonne, USA
Purdue University, West Lafayette, Indiana, USA
The first prototype superconducting undulator (SCU0) was successfully installed and commissioned at the Advanced Photon Source (APS) and is delivering photons for user science. All the requirements before operating the SCU0 in the storage ring were satisfied during a short but detailed beam commissioning. The cryogenic system performed very well in the presence of the beam. The total beam-induced heat load on the SCU0 agreed well with the predictions, and the SCU0 is protected from excessive heat loads through a combination of orbit control and SCU0 alignment. When powered, the field integral measured with the beam agreed well with the magnet measurements. An induced quench caused very little beam motion, and did not cause loss of the beam. The device was found to quench during unintentional beam dumps, but quench recovery is transparent to storage ring operation. There were no beam chamber vacuum pressure issues and no negative effect observed on the beam. Finally, the SCU0 was operated well beyond its design requirements, and no significant issues were identified. The beam commissioning results are described in this paper.
ANL, Argonne, USA
Purdue University, West Lafayette, Indiana, USA
The first prototype superconducting undulator (SCU0) was successfully installed and commissioned at the Advanced Photon Source (APS) and is delivering photons for user science. The cryosystem was designed to handle a beam-induced heat load of up to 40 W. Prior to operations, detailed predictions of this heat load were made, including that produced by resistive wall heating by the image current, geometric wakefields, synchrotron radiation, electron cloud, and beam losses. The dominant cw source is the resistive wall heat load. The heat load predictions for standard 100 mA user operation were benchmarked using thermal sensors that measure temperatures at various locations in the SCU0 cryostat and along the electron beam chamber. Thermal analysis using the predicted heat loads from the electron beam, using three independent methods, agrees well with the observed measurements.
ANL, Argonne, USA
Purdue University, West Lafayette, Indiana, USA
The first prototype superconducting undulator (SCU0) was successfully installed and commissioned at the Advanced Photon Source (APS) and is delivering photons for user science. The magnet cores are mounted on but thermally isolated from the beam vacuum chamber. Protecting the SCU0 from high beam-induced heat loads was an important requirement before operating the SCU0 in the storage ring. Precise alignment of the beam vacuum chamber with respect to both the electron beam orbit as well as the synchrotron radiation generated in the upstream dipole magnet was therefore extremely important. The beam vacuum chamber was instrumented with nine thermal sensors. Using the sensors, the chamber alignment was determined with a 100-micron precision. This precision is more than 10 times higher than in a standard aperture scan. Other advantages of the thermal sensor-based alignment method include isolating the SCU0 alignment from other components in the orbit bump and providing good longitudinal spatial resolution. The chamber temperatures agreed well the predicted heat load and dependence on steering. This novel beam-based alignment method and results will be presented.
ANL, Argonne, USA
The APS Upgrade project includes adding more insertion devices (IDs) to the APS storage ring. Perturbations from IDs have been reviewed, and the most significant sources are coming from the IDs that generate circular polarized light. To address this issue, we measured non-linear effects from the existing circular polarized undulator (CPU) and intermediate-energy x-ray (IEX). Measurement results have been compared with the simulation work. Correction schemes have been proposed and tested through experiments.