vacuum

Paper	Title	Other Keywords	Page
OPR02	Recent Experimental Results on Amorphous Carbon Coatings for Electron Cloud Mitigation	electron, dipole, cathode, proton	6
	C. Yin Vallgren, S. Calatroni, P. Chiggiato, P. Costa Pinto, H. Neupert, M. Taborelli, G. Rumolo, E. Shaposhnikova, W. Vollenberg CERN
	Amorphous carbon (a-C) thin films, produced in different coating configurations by using d.c magnetron sputtering, have been investigated in laboratory for low secondary electron yield (SEY) applications. After the coatings had shown a reliable low initial SEY, the a-C thin films have been applied in the SPS and tested with LHC type beams. Currently, we have used a-C thin film coated in so-called liner configuration for the electron cloud monitors as well as for a removable sample. In addition the vacuum chambers of three dipole magnets have been coated and inserted in the machine. After describing the different configurations used for the coatings, results of the tests in the machine and a summary of the analyses after extraction will be presented. Based on comparison between different coating configurations, a new series of coatings has been applied on three further dipole magnet vacuum chambers. They have been installed and will be tested in coming machine development runs.
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OPR03	Can Electron Multipacting Explain the Pressure Rise in the Cold Bore ANKA Superconducting Undulator?	electron, undulator, photon, simulation	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.
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MIT00	e-Cloud Activity of DLC and TiN Coated Chambers at KEKB Positron Ring	positron, electron, ion, synchrotron	37
	S. Kato, M. Nishiwaki KEK
	A copper chamber without coating and TiN and diamond like carbon (DLC) coated aluminum chambers were installed to an arc section of the KEKB positron ring to make comparisons of electron cloud activity as well as total pressure and residual gas components during the beam operation under the same condition. Recently a DLC coated aluminum chamber with high surface roughness that was obtained with cost-effective simple abrasive of the large grain before the coating was installed in the same arc section and exposed to the electron cloud until the KEKB shutdown. The measured electron cloud activity in the DLC coated chamber with smooth surface showed half and one-sixth of those in the TiN coated chamber and the copper chamber, respectively at the operation of around 1·103 Ah. Much more reduction of the e-cloud activity owing to the DLC on the roughed chamber surface was found, that is ,a reduction of one-fifth and one-tenth, respectively, in comparison with the DLC on non-roughed chamber and the TiN coating on non-roughed chamber at around 1·103 Ah. Preparation of the DLC coated chamber, characteristics of the DLC and measurements including the residual gas observation will be also reported in detail.
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MIT03	Experimental Efforts at LNF to Reduce Secondary Electron Yield in Particle Accelerators	electron, radiation, synchrotron, synchrotron-radiation	46
	R. Cimino, M. Commisso, T. Demma, D. Grosso INFN/LNF N. Mahne, A. Giglia CNR-IOM
	A common effort in most of the accelerator centers is to develop new technologies to produce and test beam pipe inner walls of particle accelerators with an as low as possible Secondary Electron Yield (SEY). This item, in fact, is crucial in controlling Electron Cloud formation and in reducing its effects, that are well known to be a potential bottle-neck to the performances obtainable from present and future accelerators. Frascati has a longstanding experience in qualifying materials in terms of surface parameters of interest to e-cloud issues. We are routinely measuring SEY, its dependence from electron energy, temperature and scrubbing and we are about to be ready to study not only Photo Electron Yield (PEY) by using synchrotron radiation beamlines in construction at DAΦNE, but more importantly, to characterize in situ the surface chemical composition and eventual modifications occurring during electron or photon irradiation. Such characterization effort is also suggesting ways to produce Low SEY materials. Some preliminary results will be here discussed.
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PST01	Implementation and Operation of Electron Cloud Diagnostics for CesrTA	diagnostics, electron, quadrupole, pick-up	83
	Y. Li, X. Liu, V. Medjidzade, J. Conway, M. Palmer Cornell University - CLASSE
	The vacuum system of Cornell Electron Storage Ring (CESR) was successfully reconfigured to support CesrTA physics programs, including electron cloud (EC) build-up and suppression studies. One of key features of the reconfigured CESR vacuum system is the flexibility for exchange of various vacuum chambers with minimized impact to the accelerator operations. This is achieved by creation of three short gate-valve isolated vacuum sections. Over the last three years, many vacuum chambers with various EC diagnostics (such as RFAs, shielded pickups, etc) were rotated through these short experimental sections. With these instrumented test chambers, EC build-up was studied in many magnetic field types, including dipoles, quadrupoles, wigglers and field-free drifts. EC suppression techniques by coating (TiN, NEG and a-C), surface textures (grooves) and clearing electrode are incorporated in these test chambers to evaluate their effectiveness. We present the implementation and operations of EC diagnostics.
PST08	Synrad3D Photon Propagation and Scattering Simulation	photon, site, scattering, radiation	118
	G. Dugan, D. Sagan Cornell University - CLASSE
	As part of the Bmad software library, a program called Synrad3d has been written to track synchrotron radiation photons generated in storage rings. The purpose of the program is primarily to estimate the intensity and distribution of photon absorption sites, which are critical inputs to codes which model the growth of electron clouds. Synrad3d includes scattering from the vacuum chamber walls using X-ray data from an LBNL database. Synrad3d can handle any planar lattice and a wide variety of vacuum chamber profiles. A description of the program will be given, together with some examples of results.
PST09	Electron Cloud Modeling Results for Time-Resolved Shielded Pickup Measurements at CesrTA	electron, pick-up, simulation, positron	123
	J. Crittenden, Y. Li, X. Liu, M. Palmer, J. Sikora Cornell University - CLASSE S. Calatroni, G. Rumolo CERN N. Omcikus University of California at Los Angeles
	The Cornell Electron Storage Ring Test Accelerator (CesrTA) program includes investigations into electron cloud buildup, applying various mitigation techniques in custom vacuum chambers. Among these are two 1.1-m-long sections located symmetrically in the east and west arc regions. These chambers are equipped with pickup detectors shielded against the direct beam-induced signal. They detect cloud electrons migrating through an 18-mm-diameter pattern of holes in the top of the chamber. A digitizing oscilloscope is used to record the signals, providing time-resolved information on cloud development. Carbon-coated, TiN-coated and uncoated aluminum chambers have been tested. Electron and positron beams of 2.1, 4.0 and 5.3 GeV with a variety of bunch populations and spacings in steps of 4 and 14 ns have been used. Here we report on results from the ECLOUD modeling code which highlight the sensitivity of these measurements to model parameters such as the photoelectron azimuthal and energy distributions at production, and the secondary yield parameters including the true secondary, rediffused, and elastic yield values. In particular, witness bunch studies exhibit high sensitivity to the elastic yield by providing information on cloud decay times.
PST12	In Situ SEY Measurements at CesrTA	electron, gun, radiation, controls	140
	J. Kim, J. Conway, S. Greenwald, Y. Li, T. Moore, M. Palmer, V. Medjidzade, D. Asner, C. Strohman Cornell University - CLASSE
	Measuring secondary electron yields (SEYs) on technical surfaces in accelerator vacuum systems provides essential information for many accelerator R&D projects, such as the ILC Damping Rings, regarding to electron cloud growth and suppression. As a part of CesrTA research program, we developed and deployed SEY in-situ measurement systems. Two such SEY systems were installed to expose samples with direct and scattered synchrotron radiation (SR), and the SEYs of the samples were measured as a function of SR dosages. In this poster, we describe the in-situ SEY measurement systems and the initial results on bare aluminum and TiN-coated aluminum samples.
DIA02	The Ecloud Measurement Setup in the Main Injector	electron, proton, simulation, antiproton	177
	C. Tan, R. Zwaska, M. Backfish Fermilab
	An ecloud measurement setup was installed in a straight section of the Main Injector in 2009. The goal of the setup was to compare the characteristics of different beam pipe coatings when subjected to proton beam. The setup consists of one coated and one uncoated beam pipe with the same physical dimensions installed at the same location. Four RFAs (retarding field analysers) and two BPMs (used for RF measurements) have been used to measure the ecloud densities. The RFAs have performed very well and have collected both the time evolution and energy distribution of the ecloud for bare and two types of beam pipe coatings.
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DIA04	Status of COLDDIAG: a Cold Vacuum Chamber for Diagnostics	electron, diagnostics, synchrotron, radiation	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.
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