ANL, Argonne, USA
Short-period superconducting undulators (SCUs) are presently being developed for the Advanced Photon Source. Field measurements of the SCUs will be performed at 4.2 K and near 300 K, so temperature-dependent calibration of the Hall probes is necessary. The sensitivity of the Hall probes has been measured at temperatures from 5 K to 320 K over a magnetic field range of ␣1.5 T. It was found that the sensitivity increased as the temperature decreased from 300 K to about 150 K. A specially designed probe assembly, with three Hall sensors for measuring both the horizontal and vertical field components, has been calibrated. The techniques for doing the calibration and the measurement results at various temperatures will be presented.
ANL, Argonne, USA
Purdue University, West Lafayette, Indiana, USA
The APS Upgrade calls for the development and commissioning of a superconducting undulator (SCU) at the Advanced Photon Source (APS), a 7-GeV electron synchrotron. Operation of an SCU at Angstromquelle Karlsruhe (ANKA), also an electron ring, suggests that electron multipacting is consistent with the observed heat load and pressure rise, but this effect is not predicted by an electron cloud generation code. At APS it was found that while the cloud code POSINST agreed fairly well with retarding field analyzer (RFA) data for a positron beam (operated 1996-98), the agreement was less satisfactory for the electron beam. The APS data suggest that the photoelectron model is not complete. Given that the heat load is a critical parameter in designing the cryosystem for the SCU and given the experience at ANKA, a study is underway to minimize the possible contribution to the heat load by the electron cloud at the APS, the photoelectrons in particular. In this talk, the results from POSINST are presented. Preliminary tracking of the photon flux using SYNRAD3D for the APS SCU chamber is presented, and possible ways to mitigate the photoelectrons are discussed.
ANL, Argonne, USA
BINP SB RAS, Novosibirsk, Russia
Short-period superconducting undulators are being developed as part of the Advanced Photon Source (APS) upgrade program. The first test device is in fabrication. Before installation into the storage ring, the magnetic performance of the undulators will be characterized. The magnetic measurement facility routinely used for measuring and tuning conventional undulators cannot be employed for superconducting devices, so a new measurement system is being designed and built. The system is mechanically mounted on the undulator cryostat and uses a heated tube in the cold undulator bore to guide a Hall probe or measuring coils. A specially designed three-Hall sensor assembly allows measurement of the vertical and horizontal components of the magnetic field and the determination of the height of the magnetic midplane. A set of measuring coils is mounted on carbon-fiber tubes that can be translated and rotated in the undulator bore to measure the field integrals and their multipole components. The design of the measurement system and its construction status is described in this paper.
ANL, Argonne, USA
A number of superconducting wigglers are installed and in operation worldwide. Superconducting undulators, with their shorter periods and more demanding field quality requirements, present additional challenges and are still under development. Superconducting technology can produce a higher magnetic field strength on the beam axis than can a permanent-magnet-based undulator. This makes shorter period undulators feasible – they will still reach high enough field to have a reasonable photon energy tuning range. The shorter period device gives higher photon brightness at higher photon energies, opening up new opportunities for photon-hungry applications that require higher photon energies. Many light sources are interested in having a superconducting undulator; a few, including the Advanced Photon Source, have ongoing projects and are making significant progress. The status of these projects will be discussed.
