Synchrotron Radiation Center

Iowa State Undulator Installed

An electromagnetic undulator, the first of two new insertion devices intended for SRC, was installed on the Aladdin storage ring on November 6, 1993. Initial tests of the undulator after delivery by Maxwell- Brobeck Division have demonstrated that the device can be run over its entire design magnetic field range without impact on the electron beam orbit.

 

The Iowa State Undulator, placed on Aladdin in the straight section LSS-4, was designed for very high resolution over the specific energy range from 15 to 30 eV. Cost and complexity were minimized, and efficiency was maximized, by limiting the long period, low-K undulator to this very important energy region.

 

By optimizing the entire beamline, from undulator to detector, over a small energy range, researchers will see an improvement of a factor of four over the best achievable result on a bending magnet. Dr. Clifford Olson, who, with Dr. David Lynch, designed the undulator, commented on this increase in resolution: "We've given up the versatility and what we've gained is performance."

Dr. Olson anticipates that the majority of the work done with the undulator's beamline will involve high temperature superconductors, although increased resolution is important for study of more conventional materials as well, such as studies of epitaxial overlayers with large unit cells.

The specifications of the undulator and beamline were handled by Olson and Lynch in cooperation with SRC, which participated in the joint discussions with industry and ISU/Ames Laboratory on the design and procurement of the device. The SRC team contributed flux performance specifications, as well as input into the structuring, content, and review of the bid document submitted to industry. The design phase culminated in a proposal for a 16 period, 2.4 meter long undulator, with electromagnetic coils for ease of change of photon energy. Funding was primarily provided by the National Science Foundation, with a major contribution from Iowa State University.

Preparation for installation of the undulator upon delivery was handled by Bill Winter, engineering group leader at SRC. About five months ahead of delivery, the engineering team started their preparation for the undulator, including:

  • fabrication of a new section of vacuum chamber for Aladdin
  • completion of a cooling system as well as electrical and water hookups to the undulator
  • construction of a kinematic translation plate, complete with retractable undercarriage support to allow for unimpaired storage ring injection.

Greg Rogers of SRC was responsible for shielding the undulator, preventing radiation problems, and aligning the undulator to the beam.

Walt Trzeciak, Ed Rowe and Mike Green, senior scientists in accelerator development at SRC, have assisted from the beginning of the project in order to assure smooth adaptation of the undulator into the ring environment. The main concern for the SRC with the installation of a new insertion device was that Aladdin's performance, and therefore users' beamlines, was disrupted as little as possible. According to Green, testing after installation has revealed an almost negligible shift in tune, and, as expected, absence of any coupling contribution which could affect either vertical beam size or horizontal/vertical beam rotation.

SRC, Olson and Lynch specified magnetic parameters such that the device will not interfere with operation and usage of Aladdin by other users, even when the undulator's excitation is changed dynamically. The electromagnetic design of the ISU undulator also allows the undulator to be "shut off" during Aladdin's injections to eliminate interference.

Trzeciak explained that for initially, and for the near future, the SRC operators will have complete control over all undulator parameters. Each user will have the undulator set in a specific operation mode for the duration of their beam time. In the future, the beamline user will be able to change the undulator wavelength from the beamline with no impact on other users.