Modifying CERN SPS cavities and amplifiers for use in RHIC

A system of ten rf cavities operating at 197 MHZ will provide longitudinal focusing during beam storage in the Relativistic Heavy Ion Collider (RHIC). The cavities and tetrode amplifiers are from CERN where they had been used in the Super Proton Synchrotron to accelerate leptons for injection into LEP. The amplifier-cavity system had an impedance pole about 3 MHz below cavity resonance which was a possible source of oscillation with rf feedback. This was not a problem at CERN because the cavities were operated without feedback. The impedance pole was moved lower in frequency by extending the length of the drive line. When this was done it was no longer possible to tune the amplifier to give a good match to the drive loop resulting in about 50% anode efficiency. In the class of operation we are using, an efficiency of 65%-70% is expected. A good match was achieved by increasing the loop coupling from 16{Omega} to 19{Omega}

Magnetic measurements on an in-vacuum undulator for the NSLS x-ray ring

Magnetic measurements have been performed on the In-Vacuum Undulator (IVUN), built jointly by BNL and SPring-8 for the NSLS X-ray Ring. The IVUN magnet has a Halback-type, pure-permanent magnet structure with a period of 11 mm and a minimum gap of 2 mm. Results of magnetic measurements utilizing Hall probe, moving wire and pulsed wire techniques will be presented and compared

VISA Undulator Fiducialization and Alignment

As part of the R&D program towards a fourth generation light source, a Self-Amplified Spontaneous Emission (SASE) demonstration is being prepared. The Visible-Infrared SASE Amplifier (VISA) undulator will be installed at Brookhaven National Laboratory by the end of the year. The VISA undulator is an in-vacuum, 4-meter long, 1.8 cm period, pure-permanent magnet device, with a novel, strong focusing, permanent magnet FODO array included within the fixed, 6 mm undulator gap. The undulator is constructed of 99 cm long segments. To attain maximum SASE gain requires establishing overlap of electron and photon beams to within 50 µm rms. This imposes challenging tolerances on mechanical fabrication and magnetic field quality, and necessitates use of laser straightness interferometry for calibration and alignment of the magnetic axes of the undulator segments. This paper describes the magnetic centerline determination, and the fiducialization and alignment processes which were performed to meet the tolerance goal.