ANL, Lemont, Illinois, USA
The fast orbit feedback (FOFB) bandwidth for Advanced photon source upgrade (APS-U) will be DC-1 kHz and the synchrotron frequency will be between 100-560 Hz. This frequency overlap places coupled bunch mode 0 (CBM0) induced horizontal orbit motion inside the orbit feedback bandwidth, potentially affecting our ability to achieve beam stability goals. Longitudinal feedback kicker is not strong enough to damp CBM0 oscillations. We developed new beam-based feedback method to suppress CBM0 oscillations with low level RF phase as actuator. It uses existent FOFB framework with no changes to the feedback algorithm. Effectiveness of this method is verified using present APS operations lattice where synchrotron frequency is outside orbit feedback bandwidth*. In the present work, low alpha lattice is created to emulate APS-U setting where synchrotron frequency is inside the orbit feedback bandwidth. Experiments with this lattice successfully demonstrated CBM0 correction within FOFB bandwidth. Combined operation of orbit feedback and CBM0 correction is stable, and CBM0 oscillations are damped. We achieved better orbit motion suppression and corrector drive efforts are reduced as well.
* P. Kallakuri et al., ’Coupled bunch mode zero correction using orbit measurements and RF system phase feedback’, doi:10.1103/PhysRevAccelBeams.25.082801
ANL, Lemont, Illinois, USA
We report on measurements of beams from thermionic cathode (TC) rf guns in the Advanced Photon Source S-Band Linac. These measurements include the macropulse out of both new and existing TC guns as well as the observation of microbunching within the micropulses of these beams. A gun chopper limits the macropulse FWHM duration to the 10-ns range. Our objectives were to analyse the new TC gun and investigate microbunching within a TC-rf-gun-generated beam. Our diagnostics elucidated longitudinal beam structures from the ns to the fs time scales. Coherent transition radiation (CTR) interferometers responding to far-infrared wavelengths were employed after each compression stage to provide the autocorrelations of the sub-ps micropulse durations. The first compression stage is an alpha magnet and the second a chicane. A CCD camera was used to image the beam via optical transition radiation from an Al screen at the end of the linac and also employed to measure coherent optical transition radiation (COTR) in the visible range. The COTR diagnostic observations, implying microbunching on a fs time scale, are presented and compared with a longitudinal space-charge impedance model.
ANL, Lemont, Illinois, USA
RadiaSoft LLC, Boulder, Colorado, USA
UCSC, Santa Cruz, California, USA
We present results from a recent collimator irradiation experiment conducted in the Advanced Photon Source (APS) storage ring. This experiment is the third in a series of studies to examine the effects of high-intensity electron beams on potential collimator material for the APS-Upgrade (APS-U). The intent here is to determine if a fan-out kicker can sufficiently reduce e-beam power density to protect horizontal collimators planned for the APS-U storage-ring. The fan-out kicker (FOK) spreads the bunched-beam vertically allowing it to grow in transverse dimensions prior to striking the collimator. In the present experiment, one of the two collimator test pieces is fabricated from oxygen-free copper; the other from 6061-T6 aluminum. As in past studies, diagnostics include turn-by-turn BPMs, a diagnostic image system, fast beam loss monitors, a pin-hole camera, and a current monitor. Post-irradiation analyses employ microscopy and metallurgy. To avoid confusion from multiple strikes, only three beam aborts are carried out on each of the collimator pieces; two with the FOK on and the other with it off. Observed hydrodynamic behavior will be compared with coupled codes.
ANL, Lemont, Illinois, USA
BNL, Upton, New York, USA
The Advanced Photon Source upgrade (APS-U) Multi-Bend Acromat (MBA) storage ring utilizes on-axis swap-out injection requiring up to 20nC charge per electron bunch. Enforcement of radiation safety limits for the new storage ring will be accomplished by a new beam charge monitor interlock that accumulates beam charge measurements in the Booster-to-Storage ring (BTS) transfer line and disables injection when the charge limit over a preset time period is exceeded. The new interlock is based on the existing APS Beam Shut-Off Current Monitor (BESOCM), and incorporates significant improvements over the existing system. New features include use of direct digitization and FPGA processing, extensive remote monitoring capabilities, expanded self-test and fail-safe functions, and the ability to adjust settings and monitor status remotely via EPICS. The new device integrates a test pulse (self-check) feature that verifies the integrity of the integrating beam current transformer (ICT) and cable system used to detect the beam signal. This paper describes the new BTS interlock (BESOCM) design and presents results of bench test and in-machine evaluation of the prototype and production units.
ANL, Lemont, Illinois, USA
A new synchrotron light monitor has been tested for the booster synchrotron of the Advanced Photon Source. Visible light synchrotron radiation is collected by a mirror on a path tangential to the electron beam orbit, and directed to an optical imaging system and camera. This is planned to be a non-intercepting, transverse beam-size monitor even with the higher stored beam charges (~17 nC) needed for the Advanced Photon Source Upgrade. In the present work, we describe the present synchrotron radiation diagnostic layout. An analysis of the synchrotron radiation power on the mirror, the optical layout with components, and features of the control system will be presented.
ANL, Lemont, Illinois, USA
Time domain photon diagnostics are proposed for electron beam characterisation and operation of the Advanced Photon Source Upgrade storage ring. In the present work, we present updated status on the time-domain X-ray and visible photon diagnostic beamline for the Advanced Photon Source Upgrade. We outline design influences leading to the proposed beamline layout, in particular long-term maintenance and commonality with other beamlines at the Advanced Photon Source.
ANL, Lemont, Illinois, USA
The Linac Extension Area has been developed into a beamline area for testing accelerator components and techniques. Beginning commissioning activities in February 2023, we have delivered the first electron beam to the Linac Extension Area at the Advanced Photon Source at 425 MeV. In the present work, we outline the stages of re-commissioning the electron beamline. We summarise measurements of the electron beam transport through the accelerator. We outline scenarios used to verify the adequacy of radiation shielding of the beamline, and measured shielding performance.