APS undulator radiation—first results

Abstract

The first undulator radiation has been extracted from the Advanced Photon Source ( A P S ) .The results from the characterization of this radiation are very satisfactory. With the undulator set at a gap of 15.8 mm (K=1.61), harmonics as high as the 17th were observed using a crystal spectrometer. The angular distribution of the third-harmonic radiation was measured, and the source was imaged using a zone plate to determine the particle beam emittance. The horizontal beam emittance was found to be 6.9k1.0 nm-rad, and the vertical emittance coupling was found to be less than 3%. The absolute spectral flux was measured over a wide range of photon energies, and it agrees remarkably well with the theoretical calculations based on the measured undulator magnetic field profile and the measured beam emittance. These results indicate that both the emittance of the electron beam and the undulator magnetic field quality exceed the original specifications.

Undulator a magnetic properties and spectral performance.

“…The first undulator beam at the APS was observed on August 9, 1995 [5], and a summary of the first results was given by Cai et al [6]. Based on the characterization of the device that included magnetic measurements, absolute spectral flux measurements with a gas-scattering spectrometer, and crystal spectrometer measurements of the spectrum (up to the 17 th harmonic), it was concluded that the undulator had exceeded the demanding magnetic requirements that were specified in the design.…”

“…There was no specification on B peak . 6) Derived from the effective K value at 10.5 mm (zero emittance calculation). 7) On the average, the specified value for the rms peak magnetic field error was met.…”

Undulator A diagnostics at the Advanced Photon Source

“…The undulator diagnostics setup included a pinhole slit assembly to reduce the incident power and to define the angular acceptance and a crystal spectrometer for absolute spectral flux measurements [2]. All components were mounted on a standard APS optical table with five degrees of freedom, so that the setup axis could be adjusted to the axis of the undulator radiation and transverse scans could be performed.…”

Experimental Characterization of APS Undulator A at High Photon Energies (50–200 keV)

“…The recent commencement of operation of the APS storage ring offered the opportunity to characterize experimentally the performance of undulator A, the primary insertion device of interest. Low-energyregime (<50 keV) diagnostics of undulator A, along with emittance measurement methods; are described elsewhere (Cai et al, 1996). The present paper describes the measured performance of undulator A at 50-200 keV, a pho- …”