• S. Chunjarean
  SLRI, Nakhon Ratchasima
• C.-S. Hwang, J.C. Jan, F.-Y. Lin, P.H. Lin
  NSRRC, Hsinchu

Highest photon beam brightnesses are achieved in radiation from undulators. Very short period length and high fields, reached only in superconducting undulators, are desired to produce hard X-rays. In lower energy storage rings this is not enough, but radiation at higher harmonics(7th and up) are desirable. This is possible only if the undulator fields and periods are near perfect. Shimming methods as applied for room temperature permanent magnet undulators cannot be used for such superconducting magnets. The effect of field and period tolerances on higher harmonics photon beam brightnesses will be presented and limiting tolerances will be discussed. A variety of different field optimization techniques together with some measurements on test magnets will be discussed and evaluated to their usefulness as a high photon energy and high brightness radiation source.

• C. Kwankasem, S. Chunjarean
  SLRI, Nakhon Ratchasima

For the SIAM Photon Source, we propose to establish a storage ring model based on quadrupole fitting of the measured betatron functions. By fitting of quadrupole field strength parameters to measured values of the betatron function, a series of problems at the SIAM Photon Source could be determined. For example, the problem of turn-to turn electrical coil shorts was detected and solved by replacing the new quadrupole coils. Subsequently, we could identify a quadrupole calibration error due to conflicting information on the number of turns per coil. Other causes regarding the beam dynamics model such as high field saturation effects, power supply calibration error, and proximity to nearby magnets have been taken into account to establish accurate quadrupole calibration factors. The establishment of an accurate model is essential for beam dynamics predictions, closed orbit correction, response matrix determination for LOCO, low emittance operation, and optics correction for high filed insertion devices.