SLAC, Menlo Park, California
ANL, Argonne
Funding: Work supported by U.S. Department of Energy under Contract Nos. DE-AC02-06CH11357 and DE-AC02-76SF00515.
We present the performance of the cavity beam position monitor (BPM) system for the LCLS undulator. The construction and installation phase of 34 BPMs for the undulator and 2 for the transport line have been completed. The X-band cavity BPM employs a TM010 monopole reference cavity and a TM110 dipole cavity designed to operate at a center frequency of 11.384 GHz. The signal processing electronics features a low-noise single-stage three-channel heterodyne receiver that has selectable gain and a phase locking local oscillator. The approximately 40 MHz IF is digitized by a 120M sample/second four-channel 16-bit digitizer. System requirements include sub-micron position resolution for a single-bunch beam charge of 200 pC. We discuss the system specifications and commissioning results.
ANL, Argonne
Funding: U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Work is underway to improve the reilability and power handling capability of input couplers used in the Advanced Photon Source single-cell and five-cell cavities. Coupler performance during conditioning in a test cavity suggests that ceramic material defects and field enhancement caused by a mechanical gap in the coupler design may be responsible for past coupler failures at high power. Simulation results and high-power test data will be discussed.
ANL, Argonne
Funding: U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An investigation into development of a 200-kW CW solid state rf power system design to replace the existing klystron-based 352-MHz rf systems at the Advanced Photon Source has been started. The baseline 352-MHz solid state system design will consist of multiple 1-kW CW modules combined to produce a total output capability of 200-kW CW, sufficient to drive one single-cell storage ring cavity. A description of the 1-kW CW module building block of the solid state power sistem will be presented, along with results from hardware evaluation tests at the 1-kW CW level.
ANL, Argonne
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The redesign, construction, and high-power testing of a 95-kV DC, 2MW water-cooled resistive load has been completed. This load was built and installed to test and troubleshoot the Advanced Photon Source (APS) 352-MHz high –voltage klystron power supplies. The original resistive load*,** was modified to enhance and improve the load performance .In this paper, we describe the redesign of the DC load, report on the recent test results, and discuss it’s performance improvements.
*D. Horan et al., “A 2-Megawatt Load for Testing High Voltage DC Power Supplies”.
** D. Horan et al., “Performance of a 2-Megawatt High Voltage test Load”.
ANL, Argonne
JLAB, Newport News, Virginia
Funding: * Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A superconducting multi-cell cavity for the production of short x-ray pulses at the Advanced Photon Source (APS) has been explored as an alternative to a single-cell cavity design in order to improve the packing factor and potentially reduce the number of high-power RF systems and low-level RF controls required. The cavity will operate at 2815 MHz in the APS storage ring and will require heavy damping of parasitic modes to maintain stable beam operation. Novel on-cell dampers, attached directly to the cavity body, have been utilized by taking advantage of the magnetic field null on the equatorial plane in order to enhance damping. Design issues and simulation results will be discussed.
JLAB, Newport News, Virginia
ANL, Argonne
Funding: This manuscript has been authored by Jefferson Science Associates, LLC and by UChicago Argonne, LLC under U.S. DOE Contract numbers DE-AC05-06OR23177 and DE-AC02-06CH11357.
After design optimization of a squashed elliptical single-cell crab cavity at 2.8 GHz, a copper prototype has been bench measured in order to determine its rf properties and the effectiveness of waveguide damping of parasitic modes, especially the low-order mode (LOM)*. We also present detailed results of the RF cold test at 2K on niobium single-cell and two-cell prototype cavities operating either in the zero or pi mode. Further progress will be discussed on the design of high-order mode (HOM) waveguide damping, the analysis of the Lorenz force detuning simulations by ANSYS, and the prototype of on-cell damping in which a waveguide port is attached directly on the cavity’s long equator. Details of LOM/HOM impedance calculations and experimental bench measurements will be reported and compared to strict requirements for satisfying the APS impedance budget.
*J. Shi et. al., “Superconducting RF Deflecting Cavity Design and Prototype for Short X-ray Pulse Generation”, EPAC 2008, paper MOPP155.