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
Development of a new fast-switching Electromagnetic Variably Polarizing Undulator (EMVPU) is underway at the Advanced Photon Source (APS). The EMVPU can produce x-rays with left- and right-handed circular polarizations and horizontal and vertical linear polarizations in the energy range 400-2000 eV. The undulator will be able to switch between left- and right-handed circular polarization at 10 Hz, fast enough to allow for magnetic circular dichroism studies that rely on lock-in amplifier techniques. The handedness switch will be accomplished by switching only the vertical component of the field while the horizontal component stays constant. Details of the EMVPU and its initial experimental test models are presented.
ANL, Argonne, USA
An electromagnetic variably polarizing quasi-periodic undulator was installed in the Advanced Photon Source (APS) storage ring in April 2012 and has been successfully commissioned with stored beam. This device is identified as the Intermediate Energy X-ray (IEX) undulator. The IEX undulator takes its name from the IEX beamline where it is installed. The IEX undulator is able to produce a variety of polarizations: linear vertical, linear horizontal, and right- or left-handed elliptical or circular. Ten pairs of poles, distributed quasi-periodically along the undulator length, are powered separately, allowing the field strength of the quasi-periodic poles to be adjusted. This adjustability allows the user to seek a balance between the suppression of the higher harmonics and the loss of flux in the fundamental that best suits the measurement being made. The IEX undulator has a 12.5-cm period and can achieve photon energies as low as 250 eV in horizontal polarization and 440 eV in vertical polarization. A description of the IEX undulator will be presented.
ANL, Argonne, USA
The design process for a short-period planar undulator is described. This is a conventional planar design based on Nd-Fe-B magnets and vanadium permendur poles. The period length was driven by the users’ request for a high flux of photons at 23.7 keV, with minimal tuning range. A shorter period gives higher flux; 17.2 mm was the shortest value consistent with the gap limitations of the vacuum chamber and with reaching the desired photon energy. Details of the design, especially the various chamfers of edges of the magnet and pole, were examined more closely than has been the standard past practice in order to minimize the period length.
Purdue University, West Lafayette, Indiana, USA
ANL, Argonne, USA
Synchrotron radiation can potentially introduce large heat loads on the beam chamber of the superconducting undulator (SCU) at the Advanced Photon Source (APS). With the photon absorber mask, a well-aligned centered beam in the upstream bending magnet allows only a small amount of radiation power, less than 1 W, to intercept the walls of the beam vacuum chamber in the cryostat assuming no photon scattering. But beams with vertical orbit errors, especially, can deposit much higher heat loads on the beam chamber, above 100 W. An analysis was carried out to calculate the power on the vacuum chamber when the beam has an orbit error through the upstream bending magnet. This paper presents these analytical results compared to simulations that were performed using a 3D photon tracking code, Synrad3d.