PAC07 - List of Keywords (positron)

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positron

Paper	Title	Other Keywords	Page
MOOBKI01	Central Mass Energy Determination in High Precision Experiments on VEPP-4M	luminosity, electron, energy-calibration, sextupole	63
	A. Bogomyagkov S. A. Nikitin, I. B. Nikolaev, A. G. Shamov, A. N. Skrinsky, G. M. Tumaikin BINP SB RAS, Novosibirsk
	The series of experiments on mass measurements of J/Psi, Psi' and Psi'' mesons have been done on VEPP-4M collider. The accuracy of obtained mass values for JΨ- and Psi'- mesons exceeded more than 3 times the world values, based on experiments on VEPP-4* and E760*. The ongoing experiment on tau lepton mass measurement is expected to achieve accuracy 1.5-2 times better than the present world value. The present paper describes the process and uncertainties of luminosity weighted interaction energy definition. The errors of interaction energy include uncertainties due to beam energy calibration by resonant depolarization technique and errors of interaction energy calculation. A. A. Zholentz et al., Phys. Lett. B 96 (1980) 214-216.** T. A. Armstrong et al., Phys. Rev. D47 (1993) 772-783.
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MOPAN108	The FONT4 ILC Intra-train Beam-based Digital Feedback System Prototype	feedback, kicker, linear-collider, electron	416
	P. Burrows G. B. Christian, C. I. Clarke, B. Constance, A. F. Hartin, H. D. Khah, C. Perry, C. Swinson, G. R. White JAI, Oxford A. Kalinin STFC/DL/ASTeC, Daresbury, Warrington, Cheshire S. Molloy SLAC, Menlo Park, California
	We present the design of the FONT4 intra-train beam-based digital position feedback system prototype. The system incorporates a fast analogue beam position monitor front-end signal processor, a digital feedback board, and a fast kicker-driver amplifier. The system latency goal is less than 150ns. We report preliminary results of beam tests at the Accelerator Test Facility (ATF) at KEK using electron bunches separated by c. 150ns.

TUODAB01	Variations of Betatron Tune Spectrum due to Electron Cloud Observed in KEKB	electron, damping, impedance, focusing	825
	T. Ieiri H. Fukuma, Y. Ohnishi, M. Tobiyama KEK, Ibaraki
	In order to investigate the characteristics of electron clouds, the wake effects were measured at KEKB using a test bunch placed behind a bunch-train, where there was a rapid decay in the electron cloud density. The current-dependent tune-shift of the test bunch exhibited nonlinear behaviour in the vertical plane [1]. By observing the tune spectrum, we found that the spectrum width expanded and this was accompanied with a large negative tune slope at a low cloud density and at a low bunch current. However, as the cloud density increased, the spectrum width shrunk and this was accompanied with a positive tune slope. These experimental results suggested that a high electron cloud density caused an anti-damping effect in the tune spectrum. We believe that the variations in the tune slope and spectrum width might be related to the wake field in the resonator model, where the wavelength is comparable to the bunch length. [1] T. Ieiri et al., Proc. of EPAC06, Edinburgh, Scotland, 2101 (2006).
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TUZAC02	Modern Accelerator Control Systems	controls, linac, injection, electron	873
	K. Furukawa
	Discussion of modern approaches to accelerator control systems including software and hardware implications, in view of maintaining reliability under changing requirements.
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TUPMN094	Development of a Model Superconducting Helical Undulator for the ILC Positron Source	undulator, linear-collider, collider, target	1136
	S. H. Kim C. Doose ANL, Argonne, Illinois
	Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Model superconducting helical undulators are under development for the proposed International Linear Collider (ILC) positron source. The undulator requires high-permeability steel poles and superconducting coils to meet the ILC parameters. A fabrication method for steel poles on a nonmagnetic beam chamber was developed. A model undulator with a period length of 14 mm and Nb3Sn coils was fabricated. Both ends of the model were designed to provide for continuous winding of a single conductor with 39 turns per helix. A 10-mm-period model was designed and is in the fabrication process. The 14-mm-period model may be used in the development of a cryogenic magnetic measurement system. Details of the fabrication and test results will be presented.

TUPMN108	Particle-in-Cell Calculations of the Electron Cloud in the ILC Positron Damping Ring Wigglers	electron, wiggler, damping, simulation	1164
	C. M. Celata M. A. Furman, J.-L. Vay LBNL, Berkeley, California D. P. Grote LLNL, Livermore, California
	Funding: This work was supported by the Office of High Energy Physics of the U. S. Department of Energy under contract number No. DE-AC02-05CH11231. Due to copious synchrotron radiation from the beam, electron cloud effects are predicted to be important in the wiggler sections of the ILC positron damping ring. In this area of the ring, the physics is inherently 3D. Moreover, a self-consistent calculation of the physics of the electron cloud/beam system is necessary for examining such phenomena as emittance growth in the beam. We present the first calculations of this system with the self-consistent 3D particle-in-cell code WARP/POSINST. The code includes self-consistent space charge for both species, mesh refinement, and detailed models of primary and secondary electron production. Interaction with electrons is assumed to occur only in the wigglers in this model– the beam is moved using maps between wiggler sections.

TUPAS056	Compensation Strategy for Optical Distortions Arising from the Beam-Beam Interaction at CESR	electron, optics, controls, dynamic-aperture	1778
	J. A. Crittenden M. G. Billing CESR-LEPP, Ithaca, New York
	Funding: National Science Foundation grant PHY-0202078 Following two decades of operation at 5 GeV beam energy for studies of bottom quark bound states, the Cornell Electron Storage Ring (CESR) converted to 2 GeV operation in 2001 for the purpose of investigating bound states of charm quarks. This reduction of beam energy resulted in increased relative contributions of the beam-beam force. The beam-beam interaction has been found to have considerable consequences for the optics and for the injection aperture. We describe recent developments in our modelling of the beam-beam interaction, experimental validation techniques, and investigations into compensation strategies.

WEZAB01	ILC Undulator Based Positron Source, Tests and Simulations	undulator, target, electron, polarization	1974
	A. A. Mikhailichenko
	Funding: NSF An undulator based positron source allows generation of polarized positrons in quantities required by ILC. Here we describe the results of modeling and testing of elements for such a system.
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THICKI05	European Industries Potential Capabilities on Cryogenics for the Future IlC	cryogenics, linac, damping, collider	2704
	P. Dauguet
	Following the construction of LHC, the European industries have demonstrated there ability to construct complete helium and nitrogen refrigeration systems both for the needs of the huge accelerator and the associated detectors. Eight 18 kW at 4.5 K and 2.4 kW at 1.8 K helium refrigeration systems have been constructed. Each refrigeration system is connected to 3 km of the 27 km long accelerator thanks to interconnecting valve boxes and high performances helium transfer lines. This is the biggest refrigeration system ever constructed in the world. The demand for cryogenics for the future ILC project is comparable in terms of equipment sizes but even bigger in terms of number of units required. The present refrigeration system scenario of ILC includes ten 22 kW at 4.5 K refrigerators and twelve 4.1 kW at 2 K refrigerators. In the present paper, this scenario will be presented and compared to the realizations done by the European Cryogenic Industries. Contact : Pascale.dauguet@airliquide.com
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THPMN017	Polarized Positron Production and Tracking at the ILC Positron Source	target, polarization, photon, simulation	2742
	A. Ushakov S. Riemann, A. Schaelicke DESY Zeuthen, Zeuthen
	Funding: This work is supported by the Commission of the European Communities under the 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899. A positron source based on a helical undulator system is planned to be used for the future International Linear Collider (ILC). Depending on the accelerator design it will be possible to get polarized positrons at the interaction point. A source performance with high positron yield and high polarization is the aim of our design studies. We focus on the optimization of target and capture section using several simulation codes. FLUKA is a suitable tool to calculate the positron yield, heat deposition, neutron generation and induced activity of source parts. The ASTRA code is used to calculate positron capture efficiency into the optical matching device. The new release of Geant4 includes the spin dependence of all QED processes and allows to perform a helicity-dependent tracking of particles through target and capture section. Starting with a cross-check, the synergy of these three codes allowed to specify the the parameters of a polarized positron source.

THPMN027	Status of C-band Accelerator Module in the KEKB Injector Linac	linac, acceleration, electron, klystron	2769
	T. Kamitani T. Higo, M. Ikeda, K. Kakihara, N. Kudoh, S. Ohsawa, T. Sugimura, T. T. Takatomi, K. Yokoyama KEK, Ibaraki
	For future upgrade of the KEKB injector linac, components of C-band accelerator module have been developed since 2002. A prototype C-band accelerator module composed of a 50-MW klystron, an RF-pulse compressor and four 1-m long accelerating sections, has been constructed in the present S-band injector linac. It has been operated for 14 months. In a recent beam-acceleration study, it has achieved an energy gain of 151 MeV, which corresponds to an average acceleration field of 39 MV/m.

THPMN030	Enhancement of the Positron Intensity by a Tungsten Single Crystal Target at the KEKB Injector Linac	target, electron, linac, vacuum	2778
	T. Suwada R. Chehab IN2P3 IPNL, Villeurbanne K. Furukawa, T. Kamitani, H. Okuno, M. Satoh, T. Sugimura, K. Umemori KEK, Ibaraki R. Hamatsu, T. Haruna, T. Sumiyoshi TMU, Hatioji-shi, Tokyo A. Potylitsyn INPR, Tomsk I. S. Tropin TPU, Tomsk K. Yoshida SAGA, Tosu
	Funding: This work was supported by the Grant-in-Aid of Ministry of Education, Culture, Sports, Science and Technology of Japan and by the grant of Ministry of Education and Science of the Russian Federation. A new tungsten single-crystalline positron target has been successfully employed for generation of the intense positron beam at the KEKB injector linac in September 2006. The target is composed of a tungsten single-crystal with a thickness of 10.5 mm. The positron production target is bombarded at an incident electron energy of 4 GeV, and the produced positrons are collected and accelerated up to the final injection energy of 3.5 GeV in the succeeding sections. A conventional tungsten plate with a thickness of 14 mm has been used previously, and the conversion efficiency (Ne⁺/Ne^-), the ratio between the number of positrons (Ne⁺) captured in the positron capture section and the number of the incident electrons (Ne^-), was 0.20 on average. By replacing the tungsten plate with the tungsten crystal, it increased to 0.25 on average. The increase of the conversion efficiency has boosted the positron intensity to its maximum since the beginning of KEKB operation in 1999. Now this new positron source is stably operating and is contributing to increasing the integrated luminosity of the KEKB B-factory.

THPMN058	Beam Dynamics Studies in the CLIC Injector Linac	linac, emittance, electron, quadrupole	2838
	A. Ferrari A. Latina, L. Rinolfi, F. Tecker CERN, Geneva
	The CLIC Injector Linac has to accelerate both electron and positron main beams from 200 MeV up to 2.42 GeV prior to their injection into the pre-damping rings. Its 26 accelerating structures operate at 1.875 GHz, with a loaded gradient of 17 MV/m. A FODO lattice that wraps the accelerating structures at the beginning of the linac, followed by a succession of triplet lattices between the accelerating structures, is proposed. The large transverse emittance (9200 mm.mrad), bunch length (5 mm) and energy spread (7 MeV) of the positron beam set constraints on the linac in order to reach acceptable characteristics at 2.42 GeV for the injection into the pre-damping ring. The use of a bunch compressor at the entrance of the linac is an option in order to achieve good performance in both the longitudinal and transverse phase spaces. Tracking studies of both electron and positron beams in the linac have been performed and are presented.

THPMN068	Beam Impact Studies on ILC Collimators	radiation, linear-collider, collider, electron	2859
	G. Ellwood R. J.S. Greenhalgh STFC/RAL, Chilton, Didcot, Oxon
	Funding: CCLRC The Commission of the European Communities under the 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899. Spoilers in the ILC Beam Delivery System are required to survive without failure a minimum of 1-2 direct impacts from each energetic electron or positron bunch of charged particles, in addition to maintaining low geometric and resistive wall wake fields. The transient shock wave resulting from rapid localised beam heating and its implications for spoiler design are studied using ANSYS. Shockwave propagation is modelled in 2 dimensions showing the effect of dilatational shockwaves striking free surfaces, producing reflected dilatational and distortional waves. The implication of these relflected waves on the damage of the collimators is also discussed.

THPMN070	Development of a Full Scale Superconducting Undulator Module for the ILC Positron Source	undulator, vacuum, radiation, linear-collider	2862
	Y. Ivanyushenkov I. R. Bailey, J. A. Clarke, J. B. Dainton, O. B. Malyshev, L. I. Malysheva, G. A. Moortgat-Pick, D. J. Scott Cockcroft Institute, Warrington, Cheshire D. P. Barber DESY, Hamburg E. Baynham, T. W. Bradshaw, A. J. Brummitt, F. S. Carr, A. J. Lintern, J. Rochford STFC/RAL, Chilton, Didcot, Oxon P. Cooke Liverpool University, Science Faculty, Liverpool B. J.A. Shepherd STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
	Funding: This work is supported in part by the Commission of the European Communities under the 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899. An undulator based positron source is a baseline for the International Linear Collider (ILC). The HeliCal collaboration in the UK is working on the development of a full scale 4-m long undulator module. Several prototypes have been built and tested in the R&D phase of the programme that culminated in the development of manufacturing techniques suitable for construction of the first full scale undulator sections. This paper details the design and the construction status of 4-m long undulator module.

THPMN071	Status of R&D on a Superconducting Helical Undulator for the ILC Positron Source	undulator, vacuum, linear-collider, collider	2865
	Y. Ivanyushenkov I. R. Bailey, J. A. Clarke, J. B. Dainton, O. B. Malyshev, L. I. Malysheva, G. A. Moortgat-Pick, D. J. Scott Cockcroft Institute, Warrington, Cheshire D. P. Barber DESY, Hamburg E. Baynham, T. W. Bradshaw, A. J. Brummitt, F. S. Carr, A. J. Lintern, J. Rochford STFC/RAL, Chilton, Didcot, Oxon P. Cooke Liverpool University, Science Faculty, Liverpool B. J.A. Shepherd STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
	Funding: This work is supported in part by the Commission of the European Communities under the 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899. An undulator based positron source is a baseline for the International Linear Collider (ILC). The HeliCal collaboration in the UK is carrying out an R&D programme on a short period supercoducting helical undulator with the goal to develop manufacturing technique as well as modelling and measurement techniques. Several undulator prototypes have been built and successfully tested. This paper summarizes the results of the R&D phase of the project.

THPMN074	The Status of the HeLiCal Contribution to the Polarised Positron Source for the International Linear Collider	undulator, simulation, electron, damping	2874
	D. J. Scott I. R. Bailey, D. P. Barber, J. B. Dainton, L. J. Jenner Cockcroft Institute, Warrington, Cheshire E. Baynham, T. W. Bradshaw, A. J. Brummitt, F. S. Carr, Y. Ivanyushenkov, A. J. Lintern, J. Rochford STFC/RAL, Chilton, Didcot, Oxon A. Birch, J. A. Clarke, O. B. Malyshev STFC/DL/ASTeC, Daresbury, Warrington, Cheshire L. I. Malysheva Liverpool University, Science Faculty, Liverpool G. A. Moortgat-Pick Durham University, Durham
	The positron source for the International Linear Collider is a helical undulator-based design, which can generate unprecedented quantities of polarised positrons. The HeLiCal collaboration takes responsibility for the design and prototyping of the superconducting helical undulator, which is a highly demanding short period device with very small aperture, and also leads the start to end simulations of the polarised electrons and positrons to ensure that the high polarisation levels generated survive from the source up to the collision point. This paper will provide an update on the work of the collaboration, focusing on these two topic areas, and will also discuss future plans.

THPMN083	Spin Tracking at the International Linear Collider	polarization, damping, linac, simulation	2901
	I. R. Bailey, I. R. Bailey, P. Cooke, L. Zang Liverpool University, Science Faculty, Liverpool D. P. Barber DESY, Hamburg E. Baynham, T. W. Bradshaw, F. S. Carr, Y. Ivanyushenkov, J. Rochford STFC/RAL/ASTeC, Chilton, Didcot, Oxon A. Birch STFC/DL/ASTeC, Daresbury, Warrington, Cheshire A. J. Brummitt, A. J. Lintern STFC/RAL, Chilton, Didcot, Oxon J. A. Clarke, J. B. Dainton, L. J. Jenner, O. B. Malyshev, L. I. Malysheva, G. A. Moortgat-Pick, D. J. Scott Cockcroft Institute, Warrington, Cheshire A. F. Hartin OXFORDphysics, Oxford, Oxon
	Funding: This work is supported in part by the Commission of the European Communities under the 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899. Polarized electron and positron beams are foreseen for the future International Linear Collider (ILC), with polarized electrons already included in the baseline design and polarized positrons seen as a highly-desirable upgrade. High precision physics requires the polarization of both beams to be known with a relative uncertainty of approximately 0.5% or better. Therefore all possible depolarization effects that could operate between the polarized sources and the interaction regions have to be carefully modelled. The "heLiCal" collaboration aims to provide a full "cradle-to-grave" analysis of all depolarization effects at the ILC, and to develop software tools to carry out appropriate computer simulations. In this paper we report on the first phase of our work which includes extensive simulations of the ILC spin-dynamics and a detailed study of beam-beam depolarization effects at the interaction point(s).

THPMN087	Simulations of the Rotating Positron Target in the Presence of OMD Field	target, simulation, optical-matching, linear-collider	2909
	S. P. Antipov W. Gai, W. Liu ANL, Argonne, Illinois L. K. Spentzouris Illinois Institute of Technology, Chicago, Illinois
	Funding: US Department of Energy For an ILC undulator-based positron source target configuration, a strong optical matching device (OMD) field is needed inside the target to increase the positron yield (by more than 40%)[1]. It is also required that the positron target is constantly rotated to reduce thermal and radiation damage. We report on a simulation of the rotating metal target wheel under a strong magnetic field. By rearranging Maxwell?s equations for a rotating frame and using FEMLAB, we have solved the detailed magnetic field distribution and eddy current of a rotating metal disk in magnetic field, and so the required power to drive the target wheel. In order to validate the simulation process, we have compared our results with previous experimental data [2] and found they are in very good agreement, but differ from previous approximate models [3]. Here we give detailed results on the proposed ILC target system, such as induced magnetic field (dipole and higher orders), eddy current distribution and the driving force requirements. The effect of these higher order fields on the positron beam dynamics is also considered.

THPMN090	Systematic Study of Undulator Based ILC Positron Source: Production and Capture	undulator, target, photon, polarization	2918
	W. Liu W. Gai, K.-J. Kim ANL, Argonne, Illinois
	A systematic study of the positron production and capture systems for the undulator-based ILC positron source has been performed. Various undulator parameters, such as k and λ, were considered. Our model starts from the electron beam production of the polarized photons in the undulator section, photon transport and collimation in the drift section, and photon interaction on the target (titanium or tungsten). Next, our model transports the produced polarized positrons from the target, through the tapered capturing magnet, and through the normal conducting linac to several hundred MeV. Finally, the captured positrons meeting the damping ring emittance and energy spread requirements are accelerated up to 5 GeV using the standard ILC superconducting cavities. We will present parametric studies for the different scenarios (e.g. 60% polarization vs. unpolarized; target immersed in magnetic field vs. non-immersed) currently under consideration and report on the capturing yield and polarizations achieved for each.

THPMN091	Study on High Flux Accelerator Based Slow Positrons Source	target, simulation, radiation, electron	2921
	J. Long S. Chemerisov, W. Gai, C. D. Jonah, W. Liu, H. Wang ANL, Argonne, Illinois
	This work represents a new direction in the development of linac-based high intense slow positron source. The approach is to use RF cavities to decelerate positrons (to ~100 keV) which are produced from a high-energy electron (~10 MeV) beam irradiating a heavy-metal target. In this paper, we present simulation works on the technique to decelerate the positrons to energies where techniques such as penning traps, DC deceleration or moderation can be done with high efficiency. Present techniques for decelerating positrons by thermalizing them in tungsten moderator have an efficiency of 10^-3 to 10^-5 slow positrons per high energy positron, so even modest success in decelerating and trapping positrons can lead to an increase in the production of low-energy positrons. The challenging aspect of this work is the broad energy and angular distribution of the positrons produced by pair-production in the heavy-metal target. We have explored the use of an adiabatic-matching device and a pillbox RF cavity and have obtained promising results.

THPMN092	Design and Prototyping of the AMD for the ILC	target, simulation, power-supply, coupling	2924
	H. Wang W. Gai, W. Liu ANL, Argonne, Illinois A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio T. Wong Illinois Institute of Technology, Chicago, Illinois
	The Adiabatic Matching Device (AMD), a tapered magnetic field with initial on-axis magnetic field up to 5 Tesla, is required in ILC positron capturing optics. An option of using a pulsed normal conducting structure based on flux concentrator technique can be used to generate high magnetic field. By choosing the AMD geometry appropriately, one can shape the on-axis magnetic field profile by varying the inner shape of a flux concentrator. In this paper, we present an equivalent circuit model of a pulsed flux concentrator based on frequency domain analysis. The analysis shows a very good agreement with the experiment results from reference. We have also constructed a prototype flux concentrator based on the circuit model, and experimental results are presented to verify the effectiveness of the model. Using the equivalent circuit model, a flux concentrator based AMD is designed for ILC positron matching. The beam capturing simulation results using the designed AMD are presented in this paper. * H. Brechna, D. A. Hill and B. M. Bally, "150 KOe Liquid Nitrogen Cooled Flux Concentrator Magnet", Rev. Sci. Instr., 36 1529,1965.

THPMN100	Suppression of Muon Backgrounds Generated in the ILC Beam Delivery System	background, simulation, beam-losses, electron	2945
	A. I. Drozhdin L. Keller SLAC, Menlo Park, California N. V. Mokhov, N. Nakao, S. I. Striganov Fermilab, Batavia, Illinois
	Particle fluxes generated from the interactions of beam halo with the collimators in the ILC Beam Delivery System (BDS) can exceed tolerable levels for the collider detectors and create hostile radiation environment in the interaction region. Thorough analysis of the BDS model, beam loss patterns, driving geometry factors and physics processes along with verification of the simulation codes were performed for the current ILC BDS layout with 250-GeV electron and positron beams crossing at 14 mrad with a push-pull detector option. Muon flux reduction by distributed toroids (doughnut-type spoilers) in comparison with magnetic iron walls filling the BDS tunnel are calculated and analysed in great detail. Shielding conditions which allow occupancy of the interaction region while the full power beam is on the linac tuneup dump are also studied.

THPMN111	A Kicker Driver for the International Linear Collider	kicker, damping, linear-collider, collider	2972
	M. A. Kempkes F. O. Arntz, M. P.J. Gaudreau Diversified Technologies, Inc., Bedford, Massachusetts A. Kardo-Sysoev IOFFE, St. Petersburg A. Krasnykh SLAC, Menlo Park, California
	Diversified Technologies, Inc. (DTI), under a SBIR grant from the U. S. Department of Energy, is developing a driver for a kicker strip-line deflector which inserts and extracts charge bunches to and from the electron and positron damping rings of the International Linear Collider. The deflector requires a driver capable of 10 kV, 200 A pulses of 2 ns duration, after-pulse clamping of the deflector voltage to less than one volt within six nanoseconds, and must function at burst rates of 3 to 6 MHz. The driver must also effectively absorb high-order mode signals emerging from the deflector itself. In this paper, DTI will describe a promising approach to the design of the kicker driver involving high voltage DSRDs (Drift Step Recovery Diodes) and high voltage MOSFETs. In addition, our design approach to meeting the challenges posed by the ILC requirements will be discussed.

THPMS012	Collection Optics for ILC Positron Target	target, electron, undulator, optics	3017
	A. A. Mikhailichenko
	Funding: NSF We are considering the implementation of a Lithium lens and SC solenoidal lens for collection of positrons in ILC undulator-based source. Such a lens installed right after the thin target, which is illuminated by gamma quants from helical undulator.

THPMS037	ON THE POSSIBILITY OF ACCELERATING POSITRON ON AN ELECTRON WAKE AT SABER	electron, plasma, simulation, target	3082
	X. Wang R. Ischebeck SLAC, Menlo Park, California C. Joshi UCLA, Los Angeles, California T. C. Katsouleas, P. Muggli USC, Los Angeles, California
	Funding: This work was supported by the Department of Energy contract DE-FG02-92-ER40745 A new approach for positron acceleration in non-linear plasma wakefields driven by electron beams is presented. Positrons can be produced by colliding an electron beam with a thin foil target embedded in the plasma. Integration of positron production and acceleration in one stage is realized by a single relativistic, intense electron beam. Simulations with the parameters of the proposed SABER facility at SLAC suggest that this concept could be tested there.

THPMS060	Transport Optics Design and Multi-particle Tracking for the ILC Positron Source	linac, target, optics, electron	3124
	F. Zhou Y. K. Batygin, Y. Nosochkov, J. Sheppard, M. Woodley SLAC, Menlo Park, California W. Liu ANL, Argonne, Illinois
	Funding: U. S. DOE Contract DE-AC02-76SF00515 Undulator-based positron source is adopted as the International Linear Collider baseline design. Complete optics to transport the positron beam having large angular divergence and large energy spread from a thin Ti target to the entrance of the 5 GeV damping ring injection line is developed. Start-to-end multi-particle tracking through the beamline is performed including the optical matching device, capture accelerator system, transport system, superconducting booster linac, spin rotators, and energy compressor. Positron capture efficiency of different schemes (immersed vs shielded target, and flux concentrator vs quarter wave transformation for the optics matching system) is compared. For the scheme of a shielded target and quarter wave transformation, the simulation shows that 15.1% of the positrons from the target are captured within the damping ring 6-D acceptance at the entrance of the damping ring injection line.

THPMS067	A CW Positron Source for CEBAF	electron, target, quadrupole, simulation	3133
	S. Golge A. Freyberger Jefferson Lab, Newport News, Virginia C. Hyde-Wright ODU, Norfolk, Virginia
	Funding: Authored by Jefferson Science Associates, LLC under U. S. DOE Contract No. DE-AC05-06OR23177. A positron source for the 6 GeV (or the proposed 12 GeV upgrade) recirculating linacs at Jefferson Lab is presented. The proposed 100nA CW positron source has several unique characteristics; high incident beam power (100kW), 10 MeV incident electron beam energy, CW incident beam and CW production. Positron production with 10 MeV electrons has several advantages; the energy is below neutron threshold so the production target will not become activated during use and the absolute energy spread is bounded by the low incident energy. These advantages are offset by the large angular distribution of the outgoing positrons. Results of simulations of the positron production, capture, acceleration and injection into the recirculating linac are presented. Energy flow and thermal management of the production target present a challenge and are included in the simulations.

THPMS095	Experimental Demonstration of Feasibility of a Polarized Gamma-source for ILC Based on Compton Backscattering Inside a CO2 Laser Cavity	laser, electron, photon, scattering	3208
	I. Pogorelsky V. Yakimenko BNL, Upton, Long Island, New York
	Funding: Work supported by US Department of Energy contract DE-AC02-98CH10886 Compton interaction point incorporated into a high-average-power laser cavity is the key element of the Polarized Positron Source (PPS) concept proposed for ILC [1]. According to this proposal, circularly polarized gamma rays are produced in Compton backscattering from a 6 GeV linac e-beam inside a CO2 laser amplifier cavity. Intra-cavity positioning of the interaction point allows multiple laser recycling to match the electron bunch train format. We conducted experimental tests of multi-pulse operation of such active Compton cavity upon injection of a picosecond CO2 laser beam. Together with earlier demonstration of a high x-ray yield via the e-beam/CO2-laser backscattering, these new results show a viability of the entire PPS concept and closely prototype the laser source requirements for ILC. [1] V. Yakimenko and I. V. Pogorelsky, Phys. Rev. ST Accel. Beams 9, 091001 (2006)

THPAN060	3D PIC Method Development for Simulation of Beam-Beam Effects in Supercolliders	simulation, electron, focusing, beam-beam-effects	3366
	M. A. Boronina E. Levichev, S. A. Nikitin BINP SB RAS, Novosibirsk V. N. Snytnikov IC SB RAS, Novosibrsk V. A. Vshivkov ICM&MG SB RAS, Novosibirsk
	A new Beam-Beam simulation code based on a 3D PIC method has been developed. Taking into account to the full extent the three-dimensional nature of the interaction can be useful for studies of some thin questions such as a pinch effect at large crossing angles in ILC and Crab Waist properties in SuperB Factory. Colliding electron and positron beams move in the region shaped as parallelepiped. The physical process is described by Vlasov-Liouville equations and a set of Maxwell equations that interrelate of the densities of charge and current, and intensities of electric and magnetic fields. The examples of the electron and positron bunches movement and collision simulation are presented.

THPAN087	Study of Turn-by-Turn Vertical Beam Dynamics at Low and High Energy CESR Operation	electron, synchrotron, synchrotron-radiation, radiation	3423
	R. Holtzapple G. W. Codner, M. A. Palmer, E. Tanke CESR-LEPP, Ithaca, New York J. S. Kern Alfred University, Alfred, New York
	Funding: This work was supported by the National Science Foundation. Presently, CESR is operated at two different beam energies, low energy (E=2GeV) for high energy physics (CESR-c), and high energy (E=5.3GeV) for synchrotron radiation production (CHESS). The electron and positron bunches vertical dynamics at these two energies are vastly different, in part due to the change in the pretzel orbit, the presence of wiggler magnets at low energy, and synchrotron radiation power at two vastly different energies. Using the 32 channel photomultiplier array, we measured the vertical beam dynamics on a turn-by-turn basis during CHESS and CESR-c operation as well as dedicated machine studies time. For these studies we quantify the electron cloud effects such as vertical tune shift and vertical beam size blow-up along the electron and positron trains at these two vastly different beam energies. In addition, the turn-by-turn capability of the PMT array allows us to study the vertical bunch dynamics over 10k turns. Design and Implementation of an Electron and Positron Multibunch Turn-by-Turn Vertical Beam Profile Monitor in CESR-PAC2007 proceedings

FRPMN042	Continued Study on Photoelectron and Secondary Electron Yield of TiN Coating and NEG (Ti-Zr-V) Coatings at the KEKB Positron Ring	electron, photon, simulation, synchrotron	4054
	Y. Suetsugu H. Hisamatsu, K.-I. Kanazawa, K. Shibata KEK, Ibaraki
	In order to investigate a way to mitigate the electron-cloud instability (ECI), the secondary electron and photoelectron yields (SEY and PEY) of a TiN coating and a NEG (Ti-Zr-V) coating have been studied at the KEK B-Factory (KEKB) positron ring. Following the previous study at an arc section, the test chambers were installed a straight section, where the line density was less than 1/10 of that at the arc section. The number of electrons around the beam orbit was measured up to a stored beam current of about 1.7 A (1389 bunches). The electron current of the NEG-coated and TiN-coated chambers were about 60% and 30% of that for a copper chamber, respectively. The difference between the copper and the NEG coating was clearer than the measurement at the arc section, where the intense SR obscured the effect of SEY. The evaluated max values for the TiN coating, the NEG coating and the copper were 0.9 - 1.0, 1.0 - 1.1 and 1.3 - 1.4, respectively, which were almost consistent with the previous results. The experiments using a beam duct with ante-chambers are also briefly touched upon. Y. Suetsugu et al., NIM-PR-A, Vol.556 (2006) 399.

FRPMN094	Beam Profile Measurements with the 2-D Laser-Wire at PETRA	laser, electron, photon, simulation	4303
	M. T. Price K. Balewski, Eckhard. Elsen, V. Gharibyan, H.-C. Lewin, F. Poirier, S. Schreiber, N. J. Walker, K. Wittenburg DESY, Hamburg G. A. Blair, S. T. Boogert, G. E. Boorman, A. Bosco, S. Malton Royal Holloway, University of London, Surrey T. Kamps BESSY GmbH, Berlin
	Funding: Work supported by the PPARC LC-ABD collaboration and the Commission of the European Communities under the 6th Framework Programme Structuring the European Research Area, contract number RIDS-011899. The current PETRA II Laser-Wire system, being developed for the ILC and PETRA III, uses a piezo-driven mirror to scan laser light across an electron bunch. This paper reports on the recently installed electron-beam finding system, presenting recent horizontal and vertical profile scans with corresponding studies.

FRPMS019	Measurement of the Propagation of EM Waves Through the Vacuum Chamber of the PEP-II Low Energy Ring for Beam Diagnostics	electron, vacuum, simulation, plasma	3946
	S. De Santis J. M. Byrd LBNL, Berkeley, California M. T.F. Pivi SLAC, Menlo Park, California
	Funding: Work supported by the U. S. Department of Energy under Contract No. DE-AC0-05CH11231. We present the results of measurements of the electron cloud intensity in the PEP-II low energy ring (LER) by propagating a TE wave into the beam pipe. Connecting a pulse generator to a beam position monitor button we can excite a signal above the vacuum chamber cut-off and measure its propagation with a spectrum analyzer connected to another button a few meters away. The measurement can be performed with different beam conditions and also at different settings of the solenoids used to reduce the build up of electrons. The presence of a modulation in the TE wave transmission, synchronous with the beam revolution frequency and only measurable with the solenoids off, would be directly correlated to the intensity of the electron cloud phenomenon in the relative region of the ring. In this paper we present and discuss our measurements taken near Interaction Region 12 on the LER, during 2006 and early 2007.

FRPMS047	Design and Implementation of an Electron and Positron Multibunch Turn-by-Turn Vertical Beam Profile Monitor in CESR	electron, background, synchrotron, radiation	4081
	M. A. Palmer B. Cerio, R. Holtzapple, J. S. Kern Alfred University, Alfred, New York J. Dobbins, D. L. Hartill, C. R. Strohman CLASSE, Ithaca E. Tanke CESR-LEPP, Ithaca, New York M. E. Watkins CMU, Pittsburgh, Pennsylvania
	Funding: This work is supported by the National Science Foundation. A fast vertical beam profile monitor has been implemented at the Cornell Electron Storage Ring (CESR). Readout is based on the Hamamatsu H7260K multianode photomultiplier. This device has a 32 channel linear anode array with 1 mm channel pitch and sub-nanosecond rise time. It provides the ability to probe individual electron and position bunches which are separated by 14 ns within the trains in CESR. A custom 72 MHz digitizer unit allows synchronous multibunch and turn-by-turn data acquisition. An on-board digital signal processor provides local data processing capability. This system provides the capability to probe a range of single bunch and multibunch beam dynamics issues as well as machine stability issues. In this paper we describe the profile monitor hardware, data acquisition system, calibration of the profile monitor, and data analysis software.

FRPMS066	Commissioning the Fast Luminosity Dither for PEP-II	luminosity, feedback, electron, controls	4165
	A. S. Fisher S. Ecklund, R. C. Field, S. M. Gierman, P. Grossberg, K. E. Krauter, E. S. Miller, M. Petree, N. Spencer, M. K. Sullivan, K. K. Underwood, U. Wienands SLAC, Menlo Park, California K. G. Sonnad LBNL, Berkeley, California
	Funding: Supported by US DOE under contract DE-AC03-76SF00515. To maximize luminosity, a feedback system adjusts the relative transverse (x,y) position and vertical angle (y') of the electron and positron beams at the interaction point (IP) of PEP-II. The original system sequentially moved ("dithered") the electrons in four steps per coordinate. Communication with DC corrector magnets and field penetration through copper vacuum chambers led to a full-cycle time of 10 s. Machine tuning can move the beams at the IP and so had to be slowed to wait for the feedback. A new system installed in 2006 simultaneously applies a small sinusoidal dither to all three coordinates at 73, 87 and 103 Hz. Air-core coils around stainless-steel chambers give rapid field penetration. A lock-in amplifier at each frequency detects the magnitude and phase of the luminosity's response. Then corrections for all coordinates are determined using Newton's method, based on convergence from prior steps, and are applied by the same DC correctors used previously but with only one adjustment per cycle for an expected ten-fold increase in speed. We report on the commissioning of this system and on its performance in maintaining peak luminosity and aiding machine tuning.

FRPMS081	Geometric Effects on Electron Cloud	electron, beam-losses, vacuum, simulation	4243
	L. Wang A. Chao SLAC, Menlo Park, California J. Wei BNL, Upton, Long Island, New York
	The development of an electron cloud in the vacuum chambers of high intensity positron and proton storage rings may limit the machine performances by inducing beam instabilities, beam emittance increase, beam loss, vacuum pressure increases and increased heat load on the vacuum chamber wall. The electron multipacting is a kind of geometric resonance phenomenon and thus is sensitive to the geometric parameters such as the aperture of the beam pipe, beam shape and beam bunch fill pattern, etc. This paper discusses the geometric effects on the electron cloud build-up in a beam chamber and examples are given for different beams and accelerators.