ANL, Argonne, Illinois
SLAC, Menlo Park, California
In recent years, we have explored application to the Advanced Photon Source (APS) of Zholents'* crab-cavity-based scheme for production of short x-ray pulses. Work concentrated on using superconducting (SC) cavities in order to have a continuous stream of crabbed bunches and flexibility of operating modes. The challenges of the SC approach are related to the size, cost, and development time of the cavities and associated systems. A good case can be made for a pulsed system** using room-temperature cavities. APS has elected to pursue such a system in the near term, with the SC-based system planned for a later date. This paper describes the motivation for the pulsed system and gives an overview of the planned implementation and issues. Among these are overall configuration options and constraints, cavity design options, frequency choice, cavity design challenges, tolerances, instability issues, and diagnostics plans.
*A. Zholents et al., NIM A 425, 385 (1999).**P. Anfinrud, private communication.
ANL, Argonne, Illinois
Metalex Manufacturing, Cincinnati, Ohio
Hi-Tech Manufacturing, Schiller Park, Illinois
Design and construction of the undulators for the Linac Coherent Light Source (LCLS) is the responsibility of Argonne National Laboratory. A prototype undulator* was constructed in-house and was extensively tested. The device was tunable to well within the LCLS requirements and was stable over a period of several years. Experience constructing the prototype undulator led us to conclude that with appropriate engineering design and detailed assembly procedures, precision undulators can be constructed by qualified vendors without previous undulator-construction experience. Our detailed technological knowledge and experience were transferred to the successful bidders who have produced outstanding undulators. Our production concept for the 40 3.4 m long, fixed-gap, planar-hybrid undulators with a 30 mm period is presented. Manufacturing, quality assurance, and acceptance testing details are also presented.
*LCLS Prototype Undulator Report, Argonne National Laboratory Report ANL/APS/TB-48, January 2004, R. Dejus, Editor.
ANL, Argonne, Illinois
A normal-conducting deflecting cavity is being designed at the Advanced Photon Source (APS) as a part of the short x-ray pulse project intended to provide users with approximately 2 picosecond x-rays. The system will use two pairs of 3-cell cavities in sectors 6ID and 7ID for the generation of the x-ray pulse in the 7ID beamline. The 3-cell cavities are designed to provide the desired beam deflection while absorbing in excess of 4 kW of power from a pulsed rf system and up to 2.6 kW in the damper system of high-order mode (HOM) and low-order mode (LOM) waveguides. Since the cavity frequency is very sensitive to thermal expansion, the cooling water system is designed so that it is able to control cavity temperature to within 0.1?C. This paper describes the optimization of the thermomechanical design of the cavity based on calculation of thermal stresses and displacement caused by the generated heat loads, and presents the design of a cooling water system required for the proper operation of the cavities.
ANL, Argonne, Illinois
UGA, Athens, Georgia
Long-term pointing stability at synchrotron light sources using conventional rf-based particle beam position monitoring is limited by the mechanical stability of the pickup electrode assembly. Photoemission-based photon beam position monitors for insertion device beams suffer from stray radiation backgrounds and other gap-dependent systematic errors. To achieve the goal of 500-nanoradian peak-to-peak pointing stability over a one-week period, the development of a photon beam position detector sensitive only to hard x-rays (> several keV) using copper x-ray fluorescence has been initiated. Initial results and future plans are presented.