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Title: Preparing the BESSY APPLE Undulators for Top-Up Operation

Abstract

BESSY plans to go to topping up operation in the near future. A high injection efficiency is essential to avoid particle losses inside the undulator magnets and to ensure a low radiation background in the beamlines. Dynamic and static multipoles of the insertion devices have to be minimized to accomplish this requirement. APPLE II devices show strong dynamic multipoles in the elliptical and vertical polarization mode. Measurements before and after shimming of these multipoles are presented. The static multipoles of the BESSY UE56-2 which are due to systematic block inhomgeneities have successfully been shimmed recovering the full dynamic aperture.

Authors:
; ; ;  [1]
  1. BESSY GmbH, Albert-Einstein-str. 15, 12489 Berlin (Germany)
Publication Date:
OSTI Identifier:
21043434
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 879; Journal Issue: 1; Conference: 9. international conference on synchrotron radiation instrumentation, Daegu (Korea, Republic of), 28 May - 2 Jun 2006; Other Information: DOI: 10.1063/1.2436063; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; APERTURES; BEAM INJECTION; BESSY STORAGE RING; EFFICIENCY; MULTIPOLES; OPERATION; PARTICLE LOSSES; POLARIZATION; WIGGLER MAGNETS

Citation Formats

Bahrdt, J., Frentrup, W., Gaupp, A., and Scheer, M. Preparing the BESSY APPLE Undulators for Top-Up Operation. United States: N. p., 2007. Web. doi:10.1063/1.2436063.
Bahrdt, J., Frentrup, W., Gaupp, A., & Scheer, M. Preparing the BESSY APPLE Undulators for Top-Up Operation. United States. doi:10.1063/1.2436063.
Bahrdt, J., Frentrup, W., Gaupp, A., and Scheer, M. Fri . "Preparing the BESSY APPLE Undulators for Top-Up Operation". United States. doi:10.1063/1.2436063.
@article{osti_21043434,
title = {Preparing the BESSY APPLE Undulators for Top-Up Operation},
author = {Bahrdt, J. and Frentrup, W. and Gaupp, A. and Scheer, M.},
abstractNote = {BESSY plans to go to topping up operation in the near future. A high injection efficiency is essential to avoid particle losses inside the undulator magnets and to ensure a low radiation background in the beamlines. Dynamic and static multipoles of the insertion devices have to be minimized to accomplish this requirement. APPLE II devices show strong dynamic multipoles in the elliptical and vertical polarization mode. Measurements before and after shimming of these multipoles are presented. The static multipoles of the BESSY UE56-2 which are due to systematic block inhomgeneities have successfully been shimmed recovering the full dynamic aperture.},
doi = {10.1063/1.2436063},
journal = {AIP Conference Proceedings},
number = 1,
volume = 879,
place = {United States},
year = {Fri Jan 19 00:00:00 EST 2007},
month = {Fri Jan 19 00:00:00 EST 2007}
}
  • BESSY plans to build a SASE-FEL facility for the energy range from 20 eV to 1000 eV. The energy range will be covered by three APPLE II type undulators with a magnetic length of about 60 m each. This paper summarizes the basic parameters of the FEL-undulators. The magnetic design will be presented. A modified APPLE II design will be discussed which provides higher fields at the expense of reduced horizontal access. GENESIS simulations give an estimate on the tolerances for the beam wander and for gap errors.
  • Top-up operation was successfully demonstrated at UVSOR-II, which will remove the short beam-lifetime problem caused by strong Touschek effect due to the small emittance, 27 nm-rad, and the low electron energy, 750 MeV. In these years, we have improved the accelerators, step by step, towards top-up operation. The radiation shielding wall was reconstructed. The energy of the booster synchrotron and the beam transport line were successfully upgraded from 600 MeV to 750 MeV, by replacing the magnet power supplies in 2006. Soon after, we succeeded in injecting the electron beam at the full energy. We improved the radiation safety systemmore » and constructed a injection control system. In autumn, 2008, we succeeded in operating the ring for 12 hours as keeping the beam current quasi-constant at 300 mA. Currently, we operated the ring in the top-up mode for 12 hours on every Thursday night, to check the effects on the users' experiments. In 2009, we have succeeded in the top-up operation in single bunch mode. Free electron laser oscillation with the top-up mode was also successfully demonstrated.« less
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  • After three years of upgrading work, the Pohang Light Source-II (PLS-II) is now successfully operating. The final quantitative goal of PLS-II is a top-up user-service operation with beam current of 400 mA to be completed by the end of 2014. During the beam store test up to 400 mA in the storage ring (SR), it was observed that the vacuum pressure around the radio frequency (RF) window of the superconducting cavity rapidly increases over the interlock level limiting the availability of the maximum beam current storing. Although available beam current is enhanced by setting a higher RF accelerating voltage, it is bettermore » to keep the RF accelerating voltage as low as possible in the long time top-up operation. We investigated the cause of the window vacuum pressure increment by studying the changes in the electric field distribution at the superconducting cavity and waveguide according to the beam current. In our simulation, an equivalent physical modeling was developed using a finite-difference time-domain code. The simulation revealed that the electric field amplitude at the RF window is exponentially increased as the beam current increases, thus this high electric field amplitude causes a RF breakdown at the RF window, which comes with the rapid increase of window vacuum pressure. The RF accelerating voltage of PLS-II RF system was set to 4.95 MV, which was estimated using the maximum available beam current that works as a function of RF voltage, and the top-up operation test with the beam current of 400 mA was successfully carried out.« less