Photon spectrum characteristics and magnetic field performance of the prototype hybrid symmetry undulator magnet in SRRC

Abstract

A prototype Halbach hybrid magnet structure undulator with period of 10 cm was used to achieve a high magnetic field. A nearly sinusoidal magnetic field strength of 0.964 Tesla at 24 mm gap was achieved. The magnetic field was also designed and calculated using the magneto-static 3-D code of ''TOSCA''. According to those results, the field uniformity was better than 0.1% in the field rolloff range of x = +/-10 mm at 24 mm gap. The real field profile was measured to find the magnetic field behavior and the photon energy spectrum characteristics. In addition, field distributions obtained from the field measurement and simulation were used to calculate the photon spectrum characteristic. After the multipole and spectrum shimming, the good field region was controlled within 100 G.cm in the range of -2 cm less than or equal to x less than or equal to 2 cm to increase the dynamic aperture. A maximum phase error around 5.5 degrees was achieved and then maintained a high flux in the higher harmonic spectrum. The photon flux intensity is very close to the value of the ideal field simulation, which is about 10(15) photons/sec/100mA/0.1%BW. The energy range of the first harmonic ranges from 5.2 to 220 eV and the higher harmonic energy can reach 1 KeV. The electron trajectory deviation was controlled to within 5 mu m to maintain a constant optical axis and satisfy the beam dynamic requirements.