Casalbuoni, S.

Paper	Title	Page
OPR03	Can Electron Multipacting Explain the Pressure Rise in the Cold Bore ANKA Superconducting Undulator?	12
	S. Casalbuoni, S. Schleede, M. Hagelstein, D. Saez de Jauregui, P. Tavares Karlsruhe Institute of Technology
	Preliminary studies performed with the cold bore superconducting undulator installed in the ANKA (Angstrom source Karlsruhe) storage ring suggest that the beam heat load is mainly due to the electron wall bombardment. Electron bombardment can both heat the cold vacuum chamber and induce an increase in the pressure because of gas desorption. In this contribution we compare the measurements of the pressure in a cold bore performed in the electron storage ring ANKA with the predictions obtained using the equations of gas dynamic balance in a cold vacuum chamber exposed to synchrotron radiation and electron bombardment. The balance results from two competing effects: the photon and electron stimulated desorption of the gas contained in the surface layer of the chamber wall and of the gas cryosorbed, and the cryopumping by the cold surface. We show that photodesorption alone cannot explain the experimental results and that electron multipacting is needed to reproduce the observed pressure rise. Electron bombardment can at the same time explain the observed beam heat load.
	Slides
MOD00	Electron Cloud Issues for the APS Superconducting Undulator
	K. Harkay, Y. Ivanyushenkov, R. Kustom, E. Moog, R. Rosenberg, E. Trakhtenberg Argonne National Laboratory A. Garfinkel, L. Boon Purdue University S. Casalbuoni Karlsruhe Institute of Technology
	The APS Upgrade calls for the development and commissioning of a superconducting undulator (SCU) at the Advanced Photon Source (APS), a 7-GeV electron synchrotron. Operation of an SCU at ANKA, also an electron ring, suggests that electron multipacting may in part be responsible for the observed heat load and pressure rise, but this effect is not predicted by an electron cloud generation code. It was found at APS that while the cloud code POSINST agreed fairly well with Retarding Field Analyzer (RFA) data for a positron beam (operated 1996-98), the agreement was less satisfactory for the electron beam. The APS data suggest that the photoelectron model is not complete. Given that the heat load is a critical parameter in designing the cryosystem for the SCU and given the experience at ANKA, a study is underway to minimize the possible contribution to the heat load by the electron cloud at APS, the photoelectrons in particular. In this talk, the results from POSINST are presented. Preliminary tracking of the photon flux using SYNRAD3D for the APS SCU chamber is presented, and possible ways to mitigate the photoelectrons are discussed.
	Slides
DIA04	Status of COLDDIAG: a Cold Vacuum Chamber for Diagnostics	190
	S. Gerstl, T. Baumbach, S. Casalbuoni, A. Grau, M. Hagelstein, D. Saez de Jauregui Karlsruhe Institute of Technology R. Cimino, M. Commisso, B. Spataro, A. Mostacci INFN/LNF J. Clarke, D. Scott Science and Technology Facilities Council (STFC/DL/ASTeC) Daresbury Laboratory Accelerator Science and Technology Centre M. Cox, J. Schouten Diamond Light Source Ltd (Diamond) R. Jones, I. Shinton Cockcroft Institute E. Wallen Lund University - MAX-Lab R. Weigel Max-Planck Institute for Metal Research, Stuttgart V. Baglin CERN C. Boffo, G. Sikler Babcock Noell GmbH (BNG) T. Bradshaw Science and Technology Facilities Council (STFC/RAL) Rutherford Appleton Laboratory
	One of the still open issues for the development of superconducting insertion devices is the understanding of the heat load induced by the beam passage. With the aim of measuring the beam heat load to a cold bore and in order to gain a deeper understanding in the beam heat load mechanisms, a cold vacuum chamber for diagnostics is under construction. We plan to have access with the same set-up to a number of different diagnostics, so we are implementing: i) retarding field analyzers to measure the electron flux, ii) temperature sensors to measure the total heat load, iii) pressure gauges, iv) and mass spectrometers to measure the gas content. The inner vacuum chamber will be removable in order to test different geometries and materials. COLDDIAG is built to fit in a short straight section at ANKA, but we are proposing its installation in different synchrotron light sources with different energies and beam characteristics. A first installation in DIAMOND is planned in June 2011. Here we describe the technical design report of this device and the planned measurements with beam.
	Slides