EPAC08 - List of Keywords (background)

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background

Paper	Title	Other Keywords	Page
MOPC046	Femtoslicing at BESSY - Detecting More Photons	laser, photon, single-bunch, electron	172
	T. Quast, K. Holldack BESSY GmbH, Berlin S. Khan Uni HH, Hamburg R. Mitzner Universität Muenster, Physikalisches Institut, Muenster
	The BESSY femtoslicing facility is now well established* and has proven its succesful operation for femtosecond laser-pump and x-ray-probe experiments*. However, many interesting physical phenomena cannot be addressed with the presently available comparably low number of photons detected at the sample. The most direct way to increase the photon flux is to increase the laser repetition rate. In order to preserve the excellent fs-signal to ps-background ratio special storage ring fill patterns and corresponding laser synchronisation schemes have been studied. We present calculations showing the influence of a dedicated new radiator promising better flux and polarisation properties. Recent results from a new beamline based on high transmission reflection zone plates will be presented. A new avalanche photo diode-array-based detection system has been successfully tested. This allows a parallel detection in the dispersion plane behind the monochomator. The status of these improvements will be presented. S. Khan et al. Phys. Rev. Lett, (97), 074801 (2006). **C. Stamm et al. Nature Mater. 6, 740 (2007).

MOPC050	Ground Motion Studies at NSLS II	site, ground-motion, storage-ring, scattering	184
	N. Simos, M. Fallier BNL, Upton, Long Island, New York H. Amick Colin Gordon, Associates, San Bruno
	In 3rd generation light sources such as the 3 GeV NSLS II under design at BNL, strict requirements associated with vibration on the storage ring floor are imposed in order to minimize the jitter in the electron beam. Spectral characteristics storage ring vibration and dynamic properties of the ring lattice are controlling parameters. Ground motion at the NSLS-II site is characterized by a complex spectrum consisting of fast and slow motions stemming from natural and cultural sources. Cultural noise with frequencies higher than a few Hz has the potential of dramatically affecting the accelerator performance. In this study, an array of vibration measurements at the undisturbed NSLS II site has been made in order to establish the “green-field” vibration environment and its spectral characteristics. Its interaction with the NSLS II accelerator structure and the quantification of the storage ring vibration, both in terms of amplitude and spectral content have been assessed through a state-of-the-art wave propagation and scattering analysis. This paper focuses primarily on the wave propagation and scattering aspect as well as on the filtering effects of accelerator structural parameters. Work performed under the auspices of the US DOE.

MOPC128	J-PARC Accelerator Scheme for Muon to Electron Conversion Search	extraction, proton, emittance, kicker	367
	M. Tomizawa KEK, Ibaraki M. Aoki, I. Itahashi Osaka University, Osaka
	The searching for coherent neutrino-less conversion of a muon to an electron (COMET) at sensitivity of 10?16 has been proposed as an experiment using the J-PARC Nuclear and Particle Experimental (NP) Hall. The experiment is planned to utilize a 56 kW, 8 GeV-bunched proton beam slowly extracted from the J-PARC main ring. The 1 MHz beam pulsing with an extremely low bunch to bunch gap background is needed to eliminate beam-related background events and keep an experimental sensitivity as high as possible. The 8 GeV extraction energy is rather lower than an ordinary energy. The beam size must be less than apertures of the extracted orbit in the ring and the transport line to the NP Hall. Accelerator scheme to satisfy above requirements will be reported in this paper.

MOPP006	Machine Induced Backgrounds for FP420	proton, simulation, scattering, betatron	559
	R. Appleby, K. M. Potter, F. Roncarolo, G. J. Sellers UMAN, Manchester I. Azhgirey, I. Baishev, I. L. Kurochkin, V. Talanov IHEP Protvino, Protvino, Moscow Region M. Ruspa INFN-Torino, Torino
	The LHC FP420 collaboration is assessing the feasibility of installing forward proton detectors at 420m from the ATLAS and/or CMS interaction points. Such detectors aim at measuring diffracted protons, which lost less than 2% of their longitudinal momentum. The success of this measurement requires a very good understanding of the charged and neutral particle environment in the detector region in order to avoid the signal being swamped as well as for detector survivability. This background receives contributions from beam-gas interactions, halo particles surviving from the Betatron and momentum cleaning systems and secondary showers produced by particles from the 14TeV collision region striking the beampipe upstream of the FP420 detectors. In this paper, such background sources are reviewed, and the expected background rates calculated.

MOPP024	Depolarization and Beam-beam Effects at the Linear Collider	polarization, photon, positron, linear-collider	598
	G. A. Moortgat-Pick, S. Hesselbach Durham University, Durham I. R. Bailey, G. A. Moortgat-Pick, B. J.A. Shepherd Cockcroft Institute, Warrington, Cheshire D. P. Barber DESY, Hamburg E. Baynham, T. W. Bradshaw, F. S. Carr, J. Rochford STFC/RAL/ASTeC, Chilton, Didcot, Oxon A. J. Brummitt, A. J. Lintern STFC/RAL, Chilton, Didcot, Oxon A. Bungau UMAN, Manchester J. A. Clarke, O. B. Malyshev, N. C. Ryder, D. J. Scott STFC/DL/ASTeC, Daresbury, Warrington, Cheshire J. B. Dainton, K. M. Hock, L. J. Jenner, L. I. Malysheva, L. Zang Liverpool University, Science Faculty, Liverpool A. F. Hartin OXFORDphysics, Oxford, Oxon
	The clean environment at the interaction point of a lepton linear collider allows high-precision measurements for physics analyses. In order to exploit this potential, precise knowledge about the polarization state of the beams is also required. In this paper we concentrate on depolarization effects caused by the intense beam-beam interaction, which is expected to be the dominant source of depolarization. Higher-order effects, as well as critical analyses of the theoretical assumptions used in the past and theoretical improvements in the derivation of suitable equations, are given. Updates on existing simulation programs are reported. Numerical results for the design of the International Linear Collider (ILC) are discussed.

MOPP071	Intense Stopping Muon Beams	dipole, target, proton, scattering	712
	M. A.C. Cummings, R. J. Abrams, R. P. Johnson, C. Y. Yoshikawa Muons, Inc, Batavia C. M. Ankenbrandt, M. A. Martens, D. V. Neuffer, K. Yonehara Fermilab, Batavia, Illinois
	The study of rare processes using stopping muon beams provides access to new physics that cannot be addressed at energy frontier machines. The flux of muons into a small stopping target is limited by the kinematics of the production process and by stochastic processes in the material used to slow the particles. Innovative muon beam cooling techniques are being applied to the design of stopping muon beams in order to increase the event rates in such experiments. Such intense stopping beams will also aid the development of applications such as muon spin resonance and muon-catalyzed fusion.

MOPP106	Study of Radiation From RF Cavities	photon, electron, radiation, acceleration	805
	R. Sandstrom DPNC, Genève D. Huang IIT, Chicago, Illinois J. Norem ANL, Argonne, Illinois
	Essential for muon accelerators such as neutrino factories or muon colliders, ionization cooling channels use RF cavities to restore the energy lost in liquid hydrogen absorbers. One major limitation in cooling comes from electrons emitted from the cavities which can cause breakdowns or unacceptable thermal load to the liquid hydrogen vessels. In the Muon Ionization Cooling Experiment MICE, these electrons also cause background in the detectors. This paper presents simulations related to these dark currents, and analysis of data from a direct measurement of this radiation in the MuCool Test Area (MTA).

MOPP148	Design of a Magnetic Shield Internal to the Helium Vessel of SRF Cavities	shielding, linac, superconductivity, controls	898
	P. Pierini, S. Barbanotti, L. Monaco, N. Panzeri INFN/LASA, Segrate (MI)
	The TRASCO elliptical cavities for intermediate velocity protons (β=0.47) employ a coaxial cold tuner of the blade type. To meet the perfomance goals of the 700 MHz cavities in the foreseen horizontal cryostat tests, the cavities are being equipped with a magnetic shield which lies internally to the cavity helium vessel and has a simple mechanical design and assembly procedure.

TUOCM01	First Measurements of the Longitudinal Bunch Profile at SLAC Using Coherent Smith-Purcell Radiation at 28GeV	radiation, diagnostics, linear-collider, collider	1026
	V. Blackmore, G. Doucas, B. Ottewell, C. Perry OXFORDphysics, Oxford, Oxon R. Arnold, S. Molloy, M. Woods SLAC, Menlo Park, California M. F. Kimmitt University of Essex, Physics Centre, Colchester
	Coherent Smith-Purcell radiation has been demonstrated as a technique for measuring the longitudinal profile of charged particles bunches in the low to intermediate energy range. However, with the advent of the International Linear Collider, the need has arisen for a non-invasive method of measuring the bunch profile at extremely high energies. Smith-Purcell radiation has been used for the first time in the multi-GeV regime to measure the longitudinal profile of the 28GeV SLAC beam. The experiment has both successfully determined the bunch length, and has also demonstrated its sensitivity to bunch profile changes. The challenges associated with this technique, and its prospects as a diagnostic tool are reported here.
	Slides

TUPC005	Simulation Study of Laser-wires as a Post-linac Diagnostic for CLIC and ILC	linac, dipole, electron, simulation	1047
	G. A. Blair, L. Deacon, S. Malton Royal Holloway, University of London, Surrey I. V. Agapov, A. Latina, D. Schulte CERN, Geneva
	Realistic CLIC and ILC bunch trains are simulated in the linac, including intra-train collective effects, and then analysed via a realistic simulation of a laser-wire system, including effects of laser-wire signal extraction, detection and deconvolution. Implications are drawn for the use of laser-wires as a post-linac machine diagnostic.

TUPC018	New Experimental Results with Optical Diffraction Radiation Diagnostics	radiation, electron, target, shielding	1083
	E. Chiadroni, M. Castellano INFN/LNF, Frascati (Roma) A. Cianchi INFN-Roma II, Roma K. Honkavaara, G. Kube DESY, Hamburg
	The characterization of the transverse phase space for high charge density and high energy electron beams is demanding for the successful development of the next generation light sources and linear colliders. The interest in a non-invasive and non-intercepting beam diagnostics is increasingly high due to the stringent features of such beams. Optical Diffraction Radiation (ODR) is considered as one of the most promising candidates to measure the transverse beam size and angular divergence, i.e. the transverse emittance. An experiment, based on the detection of the ODR angular distribution, has been set up at DESY FLASH Facility to measure the electron beam transverse parameters. In this paper we report the recent results on the incoherent diffraction radiation produced by a 1 GeV energy electron beam going through a rectangular slit.

TUPC033	IP BPM Position Error at CLIC due to Secondary Emission from Beam-beam Backgrounds	simulation, feedback, extraction, luminosity	1122
	A. F. Hartin, R. Apsimon, P. Burrows, C. I. Clarke, C. Perry, C. Swinson OXFORDphysics, Oxford, Oxon G. B. Christian ATOMKI, Debrecen B. Constance, H. Dabiri Khah JAI, Oxford A. Kalinin STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
	Beam-beam background impacts on the IP BPM are studied for the CLIC machine. The large number of coherent pairs ( 1.8×10⁸ charges per BPM strip per bunch crossing) for the CLIC-G default parameter set, potentially leads to a large secondary emission in the BPM strips. Detailed GuineaPig++ and Geant studies reveal, however, that the coherent pairs travel down the extraction line without significant secondary showering. Geant studies of the CLIC incoherent pairs show a flux of secondary emission two orders of magnitude less than that expected for the ILC 1 TeV high luminosity scheme. Since previous studies showed that FONT IP BPM signal distortion for the ILC was of no concern, then it can also be neglected at CLIC.

TUPC057	Improving the ISIS Emittance Scanner Software	emittance, ion-source, ion, controls	1185
	S. R. Lawrie, D. C. Faircloth, A. P. Letchford STFC/RAL/ISIS, Chilton, Didcot, Oxon
	The software to drive the slit-slit emittance scanners at ISIS is re-written in C#. The scanner driver routine is enhanced to improve accuracy, and to allow real-time monitoring of the scanning procedure. A multiple document interface allows quick comparison with other measurements and with data from particle tracking codes. Integrated data processing and emittance calculation removes the need to transfer data between multiple software packages, making experimental work more efficient. A user-friendly and robust interface allows easy scanning and generates publication quality emittance plots for presentations.

TUPC058	Laser-based Ion Beam Diagnostics for the Front End Test Stand at RAL	laser, electron, ion, vacuum	1188
	D. A. Lee, J. K. Pozimski Imperial College of Science and Technology, Department of Physics, London C. Gabor STFC/RAL/ASTeC, Chilton, Didcot, Oxon
	The RAL Front End Test Stand is being constructed to demonstrate that a chopped H^- beam of 60 mA at 3 MeV with 50 pps and sufficiently high beam quality as required for future high-power proton accelerators can be produced. Because of the high beam power and a preference for online beam monitoring non-intrusive, non-destructive beam diagnostics are desirable. Two novel instruments, based on the photo-detachment of the outer electron of the H^- ions with a laser, are being developed to precisely determine the transverse beam density distribution and the beam emittance at full beam power. This paper discusses the proposed experimental layout of the devices and the progress that has been made towards realizing them. The design of the optical system is presented along with measurements of the laser beam propagation for the beam density distribution experiment. Investigations of the influence of laser beam misalignment along with measurements of the positioning accuracy of movable stages that will be used are given in light of the total expected errors.

TUPC060	A Counting Module for an Advanced Ionization Profile Monitor	photon, controls, synchrotron, extraction	1194
	D. A. Liakin, S. V. Barabin, A. Y. Orlov ITEP, Moscow P. Forck, T. Giacomini GSI, Darmstadt
	A new multi-channel counting module has been developed for advanced Ionization Profile Monitor applications. The module's maximal performance concerning time resolution is about 10 beam profile measurements per microsecond at the cost of a slightly reduced spatial resolution with 80% accuracy (or better). Module architecture, basic modes of operation and the user interface are discussed. The results of the first test in laboratory and first beam profile measurements are also presented.

TUPC065	Luminosity Measurement at DAΦNE for Crab Waist Scheme	luminosity, simulation, interaction-region, controls	1203
	M. Boscolo, F. Bossi, B. Buonomo, G. Mazzitelli, F. Murtas, P. Raimondi, G. Sensolini INFN/LNF, Frascati (Roma) N. Arnaud, D. Breton, A. Stocchi, V. Variola, B. F. Viaud LAL, Orsay P. Branchini roma3, Rome F. Iacoangeli, P. Valente INFN-Roma, Roma M. Schioppa INFN Gruppo di Cosenza, Arcavacata di Rende (Cosenza)
	Since the beginning of 2008 the DAΦNE complex started to test the "crabbed scheme" to improve the luminosity performance of the accelerator. In order to ensure a fast, accurate and absolute measurement of the luminosity and to fully understand the background conditions, the new interaction region has been equipped with three different luminosity monitors: a Bhabha calorimeter, a Bhabha GEM tracker and a gamma bremsstrahlung proportional counter. The detectors design, construction, and performance, as well as the first measurements performed at DAΦNE during the crab waist commissioning are here presented. Data are also compared with the Monte Carlo simulations of the full setup. First results acquired during the SIDDHARTA run are supposed to be presented.

TUPC089	Robust Emittance Evaluation from Complex Transverse Phase Spaces	emittance, electron, damping, booster	1263
	A. R. Rossi, A. Bacci INFN-Milano, Milano
	We present a novel procedure to analyze the transverse phase space of low energy electron bunches, close to a beam waist, in order to retrieve a sound estimate of its emittance. The procedure consist in a genetic code and a non linear fit applied in cascade, the first feeding the parameters starting values of the former. This allows us to cleanse the phase space from noise, separate the core charge from the halos and distinguish between bunch components undergoing different dynamics, such as cross over or the double emittance minima effect. Our procedure performs a rough longitudinal beam tomography, based on dynamical considerations, using transverse data. The application of the procedure to some experimental data is shown.

TUPC096	Development of Beam Loss Monitor for the SPring-8 Storage Ring	beam-losses, injection, electron, target	1284
	Y. Shimosaki, K. Kobayashi, M. Oishi, M. Shoji, K. Soutome, Y. Taniuchi JASRI/SPring-8, Hyogo-ken
	A beam loss monitor using PIN photodiodes has been developed. To check its performance, we installed it at an in-vacuum insertion device and at the injection section in the SPring-8 storage ring. Information on the beam loss at these points will be useful for examining demagnetization of permanent magnets of insertion devices and for studying a mechanism of beam loss. A noise level at these points is however high due to stray synchrotron radiation, an induction voltage generated by pulsed injection magnets, etc. The beam loss signal is then picked up under a high noise condition. Experimental results with its countermeasure will be reported.

TUPC110	Bunch Diagnostics with Coherent Infrared Undulator Radiation at FLASH	undulator, radiation, electron, diagnostics	1320
	A. Willner, H. Delsim-Hashemi, O. Grimm, J. Rossbach Uni HH, Hamburg B. Schmidt DESY, Hamburg
	The operation of the FLASH free electron laser at DESY, Hamburg, requires a high electron beam quality, one important parameter being the longitudinal charge distribution. As a new tool for investigations using coherent radiation techniques, FLASH has been equipped with an electromagnetic undulator. The device is tunable up to a maximum K-Value of 44, corresponding to 200 um wavelength at an electron energy of 500 MeV. The emitted radiation has been characterized in a first measurement campaign using a dispersive spectrometer based on reflective blazed gratings and a pyroelectric detector, operated in a Nitrogen-purged atmosphere. This paper will summarize the measurements and the results obtained from a longitudinal diagnostics analysis.

TUPD022	Electron Beam Polarimetry at the S-DALINAC	electron, scattering, polarization, target	1476
	R. Barday, U. Bonnes, C. Eckardt, R. Eichhorn, J. Enders, C. Heßler, J. Kalben, Y. Poltoratska TU Darmstadt, Darmstadt W. F.O. Müller, B. Steiner, T. Weiland TEMF, Darmstadt
	It is planned to carry out experiments at the Superconducting Darmstadt Linear Accelerator S-DALINAC with both polarized electron and photon beams at the energy of the electron beam between 10 and 130 MeV. In order to extract asymmetry from these experiments the absolute degree of the electron beam polarization needs to be known. We present the existing and planned polarimeters at the source of polarized electrons and the experimental sites, especially a 100 keV Mott polarimeter and Möller polarimeter for 15-130 MeV electrons.

TUPD033	Fabrication of Crystals for Channelling of Particles in Accelerators	collider, proton, hadron, collimation	1497
	A. Mazzolari, S. Baricordi, V. Guidi, G. Martinelli, D. Vincenzi UNIFE, Ferrara
	Channelling in bent crystals is used for beam extraction, focusing, collimation in accelerators machines, studies related to emission of coherent electromagnetic radiation and other topics. Distinctive features of performance increase is the availability of new techniques to manufacture the crystals within which channeling takes place. We propose a method to fabricate crystals through micromachining techniques, i.e., photolithography and anisotropic chemical etching. Patterning of a Si wafer with silicon nitride allows selective erosion of uncovered areas along specific atomic planes, resulting in a technique to dice Si wafers to the needed dimensions solely through chemical methods. Thus, it results in no damage to the crystal quality due to the dicing process. As was demonstrated by electron microscopy investigation, the crystal exhibits ultra flat lateral surfaces and simultaneously no amorphous layer at the entry face of the crystal with respect to the beam. The crystals were positively tested at the external line H8 of the SPS with 400 GeV protons for investigation on axial channeling and on single and multiple volume reflection experiments by the H8-RD22 collaboration.

TUPP036	"Scrubbing" Process of Cu Surfaces Induced by Electron Bombardment	electron, vacuum, simulation, target	1619
	D. R. Grosso, P. Barone, A. Bonanno, M. Camarca, M. Commisso, A. Oliva, F. Xu INFN Gruppo di Cosenza, Arcavacata di Rende (Cosenza) R. Cimino INFN/LNF, Frascati (Roma)
	Energy distribution curves of electrons emitted from accelerator used metal surfaces have been measured for electron irradiation with a primary energy from 20 to 400 eV. We separated the contributions of reflected, rediffused and true-secondary electrons out from the spectra and observed significant differences in their incidence angle dependence. These results provide crucial information on the electron cloud formation in particle accelerators and may shed light on the involved physical mechanisms

TUPP088	Software Components for Electron Cloud Simulation	electron, simulation, proton, space-charge	1735
	D. R. Dechow, P. Stoltz Tech-X, Boulder, Colorado J. F. Amundson, P. Spentzouris Fermilab, Batavia, Illinois B. Norris ANL, Argonne, Illinois
	The Synergia2 beam dynamics code is an attempt to incorporate state-of-the-art space charge models from the Impact code into the Chef accelerator tracking code. The need to add new accelerator physics capabilities to the Synergia2 framework has led to software development efforts based on the Common Component Architecture (CCA). The CCA is a specification and a toolset for developing HPC from interchangeable parts, called components. Electron cloud is a potentially limiting effect in the performance of both high-intensity electron and proton machines. The modeling of electron cloud effects is important for the Fermilab main injector. Here, electron cloud effects are expected to play a significant role when the main injector operates in the regime of a high-intensity proton source for the neutrino program. In the ideal case, computational accelerator physicists would like to be able model electron cloud generation and dynamics in a single, self-consistent simulation. As a first step towards creating component-based, electron cloud generation simulations, this work describes a CCA component created from TxPhysics, a library of impact and field ionization routines.

TUPP130	Development of 3D Dose Verification System for Scanned Ion Beam at HIMAC	brightness, ion, target, heavy-ion	1830
	N. Saotome, T. Furukawa, T. Inaniwa, T. Kanai, K. Noda, S. Sato NIRS, Chiba-shi
	A 3D dose imaging system has been developed for a project of a new cancer treatment with 3D pencil beam scanning at HIMAC. This system provides the dose measurements easily and rapidly. this system consists of a water tank, fluorescent screen and charge-coupled device, set at isocentor. The fluorescent screen is directly attached to the downstream side of water tank. One of great advantages of this system is to obtain 2D dose map at once, by correcting LET-dependent quenching. The procedure to verify 3D dose distribution is based on the 2D dose measurement of slice-by-slice under a water depth. We will present the measurement result of 3D dose distribution by the proposed method, and its comparison with that by the ionization chamber.

WEPC112	The Acceptance and Photon Beam Formation in SLS FEMTO Beamline	laser, radiation, electron, damping	2264
	L. M. Hovhannisyan, D. K. Kalantaryan, V. M. Tsakanov CANDLE, Yerevan S. T. Hakobyan YSU, Yerevan A. Streun PSI, Villigen
	The FEMTO insertion at the Swiss Light Source (SLS) produces sub-ps X-ray pulses by modulating the electron energy in a slice of the bunch through interaction with a fs-laser. The radiation from the sliced bunch in the FEMTO undulator of the SLS storage ring has been studied. Only photons passing all apertures of the beam line arrive at the experiment. We derive the transverse phase space distribution of these photons, the radiation spectra, and the spatial and angular distribution. Transmission of the radiated photons through the FEMTO beamline is calculated using the SRW simulation code in order to evaluate the acceptance of the beamline and the photon beam phase space distribution at the experimental station.

WEPC139	Recent Experience in the Fabrication and Brazing of Ceramic Beam Tubes for Kicker Magnets at FNAL	kicker, vacuum, booster, controls	2335
	C. R. Ader, C. C. Jensen, R. E. Reilly, D. Snee, J. H. Wilson Fermilab, Batavia, Illinois
	Ceramic beam tubes are utilized in numerous kicker magnets in different accelerator rings at Fermi National Accelerator Laboratory. Kovar flanges are brazed onto each beam tube end, since kovar and high alumina ceramic have similar expansion curves. The tube, kovar flange, end piece, and braze foil (titanium/inconel) alloy brazing material are stacked in the furnace and then brazed in the furnace at 1000°C. The ceramic specified is Alumina 99.8% Al₂O₃, a strong recrystalized high-alumina fabricated by slip casting. Recent experience at Fermilab with the fabrication and brazing of these tubes has brought to light numerous problems including tube breakage and cracking and also the difficulty of brazing the tube to produce a leak-tight joint. These problems may be due to the ceramic quality, voids in the ceramic, thinness of the wall, and micro-cracks in the ends which make it difficult to braze because it cannot fill tiny surface cracks which are caused by grain pullout during the cutting process. Solutions which are being investigated include lapping the ends of the tubes before brazing to eliminate the micro-cracks and also metallization of the tubes.

WEPD002	Magnetic Design Studies for the Final Focus Quadrupoles of the SuperB Large Crossing Angle Collision Scheme	quadrupole, factory, target, simulation	2401
	E. Paoloni University of Pisa and INFN, Pisa S. Bettoni CERN, Geneva M. E. Biagini, P. Raimondi INFN/LNF, Frascati (Roma)
	The vertical focusing element closest to the interaction point of the SuperB factory based on the large crossing angle collision scheme (~50 mrad), must provide a pure quadrupolar field on each of the two beams. This allows to avoid the high background rate in the detector which would be produced by the over-bend of the off-energy particles if a dipolar component were present. Because of the small separation of the two beams in the transverse dimension (only 2 cm) the influence of each winding on the other one is not negligible and, for the same space limitation, a multi-layer configuration is not suitable to compensate the high order multipoles. A novel design, based on 'helical-type' windings, has therefore been investigated. The windings generates the pure quadrupolar field as a superposition of the inner field of the surrounding coil and of the outer fringe field of the neighbor one. The same idea may be used to produce two pure quadrupolar fields with opposite strength, suitable for the final focus elements in colliders, as LHC, where the sign of the circulating particles are the same. In this paper the 2D concept and the 3D model of this design are presented.

WEPD023	Multi-purpose Fiber Optic Sensors for HTS Magnets	superconducting-magnet, monitoring, optics, controls	2458
	J. Schwartz NHMFL, Tallahassee, Florida R. P. Johnson, S. A. Kahn, M. Kuchnir Muons, Inc, Batavia
	Magnets using new high temperature superconductor (HTS) materials are showing great promise for high magnetic field and/or radiation environment applications such as particle accelerators, NMR, and the plasma-confinement systems for fusion reactors. The development and operation of these magnets is limited, however, because appropriate sensors and diagnostic systems are not yet available to monitor the manufacturing and operational processes that dictate success. Optical fibers are being developed to be imbedded within the HTS magnets to monitor strain, temperature and irradiation, and to detect quenches. In the case of Bi2212, the fiber will be used as a heat treatment process monitor to ensure that the entire magnet has reached thermal equilibrium. Real-time measurements will aid the development of high-field magnets that are subject to large Lorentz forces and allow the effective detection of quenches so that the stored energy of operating magnets can be extracted and/or dissipated without damaging the magnet.

WEPD045	Hydrogen Cryosorption on Multi Walled Carbon Nanotubes	vacuum, collider, cryogenics, synchrotron	2515
	F. Xu, M. Barberio, P. Barone, A. Oliva, L. Papagno, V. Pirronello, R. Vasta INFN Gruppo di Cosenza, Arcavacata di Rende (Cosenza)
	We present a Temperature Programmed Desorption (TPD) study on H₂ adsorption on multiwalled carbon nanotubes (MWNT) at very low pressure (< 10^-6 Torr) and temperature (12-30 K). Our results show a hydrogen take up limit in the range of 10^-8 mol per gram depending on the adsorption temperature. We compare the MWNT cryosorption capacity with that of commonly used activated carbon and discuss the possibility of employing MWNT as cryosorber in large particle accelerators.

WEPP018	Operational Experience with a Near-integer Working Point at RHIC	proton, closed-orbit, heavy-ion, dynamic-aperture	2563
	C. Montag, M. Bai, J. Beebe-Wang, W. Fischer, Y. Luo, N. Malitsky, T. Roser, T. Satogata, S. Tepikian BNL, Upton, Long Island, New York
	During the RHIC polarized proton run in FY 2006 it became evident that the luminosity performance is limited by the beam-beam effect. With a working point between 2/3 and 7/10, and the necessity to mirror the tunes of the two RHIC rings at the diagonal, the beam with a horizontal tune closest to 2/3 showed poor lifetime. To overcome this limitation, a near-integer working point has been proposed. Tracking studies performed at both working points showed a larger dynamic aperture near the integer tune than above 2/3. In Run-8, this new working point was commissioned in one ring of RHIC, while the other ring was operated at the same working point as in Run-6. In this paper we report the commissioning process and operational experience with this new working point.

WEPP042	An Improved Design for a SuperB Interaction Region	quadrupole, emittance, interaction-region, luminosity	2614
	M. K. Sullivan, J. Seeman, U. Wienands SLAC, Menlo Park, California S. Bettoni CERN, Geneva M. E. Biagini, P. Raimondi INFN/LNF, Frascati (Roma) E. Paoloni University of Pisa and INFN, Pisa
	We present an improved design for a SuperB interaction region. The new design attempts to minimize the bending of the two colliding beams which results from shared magnetic elements near the Interaction Point (IP). The total crossing angle at the IP is increased from 34 mrad to 50 mrad and the distance from the IP to the first quadrupole is increased. Although the two beams still travel through this shared magnet, these changes allow for a new a new magnetic field design with a septum which gives the magnet two magnetic centers. This greatly reduces the beam bending from this shared quadrupole and thereby reduces the radiative bhabha background for the detector as well as any beam emittance growth from the bending. We decribe the new design for the interaction region.

WEPP084	Fabrication of a Quadrant-type Accelerator Structure for CLIC	linear-collider, collider, feedback, acceleration	2716
	T. Higo, Y. Higashi, H. Kawamata, T. T. Takatomi, K. Ueno, Y. Watanabe, K. Yokoyama KEK, Ibaraki A. Grudiev, G. Riddone, M. Taborelli, W. Wuensch, R. Zennaro CERN, Geneva
	In order to heavily damp the higher order modes of an accelerator structure for CLIC, two kind of damping mechanisms are implemented in one of the designs. Here each cell is equipped with electrically coupled damping channels in addition to the magnetically coupled waveguides. This design requires an assembly of longitudinally cut four quadrants to form a structure and the parts are necessarily made with milling. Since KEK has developed a high-precision machining of X-band accelerator cells with milling and turning at the same time, the experience was extended to the milling of this quadrant. Firstly, the fabrication test of a short quadrant was performed with multiple vendors to taste the present-day engineering level of milling. Following this, a full-size quadrant is also made. In this course, some of the key features are addressed, such as flatness of the reference mating surfaces, alignment grooves, 3D profile shape of the cells, surface roughness and edge treatment. In this paper, these issues are discussed from both fabrication and evaluation point of views.

WEPP111	Modeling Breakdown in RF Cavities Using Particle-in-cell (PIC) codes	simulation, plasma, electron, ion	2767
	S. Mahalingam, J. R. Cary, P. Stoltz, S. A. Veitzer Tech-X, Boulder, Colorado
	A main limitation on future accelerator projects is breakdown of metallic structures. We have developed computer models of the process of breakdown using Particle-In-Cell (PIC) codes which include: Fowler-Nordheim field emission due to large surface electric fields, impact ionization of neutral gas, ion-induced secondary electron emission, ion-induced sputtering of neutrals, the effects of applied magnetic fields, plasma radiation effects, and surface heating. Two computational tools have been used to self-consistently model the breakdown. These are OOPIC Pro, a 2-Dimensional serial electromagnetic code with cylindrical coordinates, and VORPAL, a 3-Dimensional massively parallel electromagnetic code with cartesian grids. We describe here the results of our numerical experiments including the effects of applied magnetic field strength and direction on the breakdown process, sensitivity of breakdown triggers on field emission parameters, and the potential to measure the onset of breakdown by examining impurity radiation. We show comparison with breakdown experiments performed at Fermilab and Argonne for copper structures being considered for a future muon collider project.

THPP037	A Decelerator for Heavy Highly Charge Ions at HITRAP	emittance, ion, linac, heavy-ion	3449
	J. Pfister, B. Hofmann, U. Ratzinger, A. Schempp IAP, Frankfurt am Main W. Barth, L. A. Dahl, P. Gerhard, O. K. Kester, W. Quint, T. Stoehlker GSI, Darmstadt
	The heavy highly charged ion trap (HITRAP) project at GSI is in the commissioning phase. Highly charged ions up to U⁹²⁺ provided by the GSI accelerator facility will be decelerated and subsequently injected into a large Penning trap for further cooling almost to rest. A combination of an IH^- and an RFQ-structure decelerates the ions from 4 MeV/u down to 6 keV/u. In front of the decelerator a double drift-buncher-system provides for phase focusing and a final de-buncher integrated in the RFQ-tank reduces the energy spread in order to improve the efficiency for beam capture in the cooler trap. This contribution concentrates on the beam dynamics simulations and corresponding measurements in the first commissioning beam times.