positron

Paper	Title	Other Keywords	Page
MOPKF064	Design Considerations for a Helical Undulator for the Production of Polarised Positrons for TESLA	undulator, photon, electron, permanent-magnet	458
	D.J. Scott, S.C. Appleton, J.A. Clarke, B. Todd CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire E. Baynham, T.W. Bradshaw, S.C. Carr, Y. Ivanyushenkov, J. Rochford CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
	An efficient and simple method for the production of positrons, in the necessary quantities, is one of the problems facing proposals for any future e+ e- Linear Collider project. The possibility of colliding polarised beams would also be an advantage. One method to produce a polarised positron beam uses circularly polarised radiation generated by the main electron beam passing through a helical undulator. Design considerations and calculations for two undulators, based on super-conducting and pure permanent magnet technologies, for the TESLA machine, are presented.
MOPKF084	Beam Instabilities in Lepton Ring of eRHIC	electron, lepton, impedance, ion	515
	D. Wang, M. Farkhondeh, C. Tschalaer, J. Van der Laan, F. Wang, A. Zolfaghari, T. Zwart MIT/BLAC, Middleton, Massachusetts M. Blaskiewicz, Y. Luo, L. Wang BNL, Upton, Long Island, New York
	The eRHIC is a high luminosity lepton-hadron collider planned to be built in Brookhaven National Lab, Upton, New York, USA. The lepton machine of eRHIC is a completely newly designed machine complex to provide highly polarized lepton beams at up to 10 GeV energy for the high luminosity lepton-hadron collisions. This paper decribes major issues of collective effects in this lepton storage ring. Besides conventional impedance-driven instabilities, the electron cloud effects in positron operation and fast beam-ion effects in electron operation are of major conserns. The analytical and numerical estimats for major collective effects are made with different machine operation conditions.
MOPLT048	High Current Switch-mode Power Converter Prototype for LHC Project 6kA, 8V	simulation, collider, power-supply, quadrupole	656
	E. Jauregi, J.M. Del Río, J.M. Dela Fuente, M. Tellería, J.R. Zabaleta JEMA GJ, Lasarte-Oria F. Bordry, V. Montabonnet CERN, Geneva E.F. Figueres E.T.S.I.I., Valencia
	For the Large Hadron Collider (LHC) accelerator being constructed on the CERN site, very precise variable DC currents are required. The company JEMA had during year 2002, designed, manufactured and tested a power converter prototype according to CERN specifications, particularly demanding in terms of dc stability and dynamic response. The power converter is formed by four sub-converters 8V, 2kA in parallel. Isolation between mains input and magnet load is at high frequency done, 40 kHz, which means a volume reduction and better mains perturbations rejection. IGBT inverter soft switch-mode power conversion in ZVS operation reduces dramatically commutation losses, increasing total efficiency of the power converter. The sub-converter, regulated by a wide band width current loop in ACC mode, follows the current reference calculated by the overall voltage loop, providing a good sharing of the output currents and high output stability. The design of the water cooled power converter, results in a very reduce volume and modular structure, providing the system a very flexible exchangeability. The power converter was tested and accepted by CERN into year 2003, some minor points were left to be adjusted during the pre-series stage.
MOPLT067	KEKB Performance	luminosity, injection, vacuum, electron	707
	Y. Funakoshi, K. Akai, K. Ebihara, K. Egawa, A. Enomoto, J. Flanagan, H. Fukuma, K.  Furukawa, T. Furuya, J. Haba, S. Hiramatsu, T. Ieiri, N. Iida, H. Ikeda, T. Kageyama, S. Kamada, T. Kamitani, S. Kato, M. Kikuchi, E. Kikutani, H. Koiso, M. Masuzawa, T. Mimashi, A. Morita, T. Nakamura, H. Nakayama, Y. Ogawa, K. Ohmi, Y. Ohnishi, N. Ohuchi, K. Oide, M. Shimada, S. Stanic, M. Suetake, Y. Suetsugu, T. Sugimura, T. Suwada, M. Tawada, M. Tejima, M. Tobiyama, S. Uehara, S. Uno, S.S. Win, N. Yamamoto, Y. Yamamoto, Y. Yano, K. Yokoyama, M. Yoshida, M. Yoshida, S.I. Yoshimoto KEK, Ibaraki F. Zimmermann CERN, Geneva
	The KEKB B-Factory is an electron-positron double ring collider working at KEK. Its peak luminosity surpassed 1034 /cm2/sec in May 2003 for the first time in the history of colliders. In this report, we summarize the history of KEKB with an emphasis of recent progress.
MOPLT072	Effects of Positrons on Relativistic Solitons in Laser-Plasma Interactions	ion, electron, plasma, laser	719
	J.B.  Kim, I.S. Ko POSTECH, Pohang, Kyungbuk H. Suk KERI, Changwon
	An extended 1D kinetic model of relativistic solitons by high power lasers in three species plasmas is suggested and it is applied to analysis on the effects of electron-positron pairs on the solitons. Stability condition of the solitons is derived. The range of parameters for the stable solitons are specified in the frequency-temperature plane. With the creation of electron-positron pairs, relativistic solitons appear stable in wider range of frequencies and temperatures. The regions are expanded toward higher values in overall ranges in the frequency-temperature plane. The stability conditions are affected by the density of positrons. The variation of shapes, peak E-field, and width of the solitons by varying the positron density are analyzed. We discuss the implications of the variation in the soliton on the ion accelerations by it.
MOPLT088	Experimental Plasma Wake-field Acceleration Project at the VEPP-5 Injection Complex	plasma, acceleration, electron, injection	740
	A.V. Petrenko, A. Burdakov, A.M. Kudryavtsev, P.V. Logatchev, K.V. Lotov, A.N. Skrinsky BINP SB RAS, Novosibirsk
	The project of an experimental facility based on the VEPP-5 injection complex is described. Due to a good quality of electron or positron beams and special beam preparation system, the facility opens several possibilities for studies of the plasma wakefield acceleration: high peak beam currents, arbitrary beam profiles, long term beam-plasma interaction (up to the full driver depletion), and precise beam diagnostics. Various wakefield regimes can be experimentally demonstrated and studied: the efficient blow-out regime with a low energy spread and high acceleration rate (up to several GeV per meter); multibunch regime; long bunch instabilities; beam self-organization in plasma; plasma lens. If successfully realized, this experiment becomes a solid argument for feasibility of a high-energy collider based upon the plasma wakefield acceleration.
MOPLT089	SOS-diode Based Pulser for the Injection System of the Collider VEPP-2000	injection, kicker, collider, electron	743
	F.V. Podgorny, B.I. Grishanov, A.S. Kasaev BINP SB RAS, Novosibirsk
	We describe high voltage pulsers for supplying of kickers of the collider VEPP-2000 injection system. The high voltage pulse is formed as a result of a sharp break of a high current, accumulated previously in storage elements, by means SOS-diode. Pulse forming lines or inductances could be used as the storage elements. The generators form the quasi-rectangular pulses on the 50-Ohm load. The generator scheme is described also.
MOPLT130	Bunch Pattern with More Bunches in PEP-II	luminosity, injection, electron, beam-losses	842
	F.-J. Decker, S. Colocho, A. Novokhatski, M.K. Sullivan, U. Wienands SLAC, Menlo Park, California
	The number of bunches in the PEP-II B-Factory has increased over the years. The luminosity followed roughly linear that increase or even faster since we also lowered the spot size at the interaction point. The recent steps from 933 in June of 2003 to about 1320 in February 2004 should have been followed by a similar rise in luminosity from 6.5·1033 1/cm2 1/s to 9.2·1033 1/cm2 1/s. This didn?t happen so far and a peak luminosity of only 7.3·1033 1/cm2 1/s was achieved. By filling the then partially filled by-3 pattern to a completely filled by-3 pattern (1133 bunches) should even give 7.9·1033 1/cm2 1/s with scaled currents of 1400 mA (HER) and 1900 mA (LER). We are typically running about 1300 mA and 1900 mA with 15% more bunches. The bunch pattern is typically by-2 with trains of 14 bunches out of 18. The parasitic beam crossings or electron cloud effects might play a role in about a 10% luminosity loss. Also the LER x-tune could be pushed further down to the ? integer in the by-3 pattern. On the other hand we might not push the beam-beam tune shift as hard as in June of 2003 since we started trickle injection and therefore might avoid the highest peak luminosity with a higher background. A mixed pattern with a by2-by3 setup (separation of 2, 3, 2, 3 ?) would give totally filled a slightly higher number of bunches (1360), but near the interaction point there would be only one parasitic crossing per beam lowering the tune shift by two.
MOPLT135	Damping the High Order Modes in the Pumping Chamber of the PEP-II Low Energy Ring	vacuum, damping, impedance, electromagnetic-fields	854
	A. Novokhatski, S. Debarger, F.-J. Decker, A. Kulikov, J. Langton, M. Petree, J. Seeman, M.K. Sullivan SLAC, Menlo Park, California
	The Low Energy Ring of the PEP-II B-factory operates with extremely high currents and short positron bunches. Any discontinuity in the vacuum chamber can excite a broad-band spectrum of the High Order Modes. A temperature rise has been found in the vacuum chamber elements in one transition from straight section to arc. The power in the wake fields was high enough to char beyond use the feed-through for the Titanium Sublimation Pump. This pumping section consists of the beam chamber and an ante-chamber. Fields, excited in the beam chamber penetrate to the ante-chamber and then through the heater wires of the TSP come out. A small ceramic tile was placed near the TSP feed-through to absorb these fields. A short wire antenna was also placed there. HOM measurements show a wide spectrum with a maximum in the 2-3 GHz region. A special water cooled HOM absorber was designed and put inside the ante-chamber part of the section. As a result, the HOM power in the section decreased and the temperature rise went down. The power loss is 750 W for a beam current of 2 A. Measurements of the HOM impedance for different bunch patterns, bunch length and transverse beam position will be presented.
MOPLT136	Reliability Simulations for a Linear Collider	simulation, collider, linear-collider, luminosity	857
	N. Phinney, T.M. Himel, M.C. Ross SLAC/NLC, Menlo Park, California P. Czarapata, H. Edwards, M. Huening Fermilab, Batavia, Illinois
	A new flexible tool for evaluating accelerator reliability was developed as part of the US Linear Collider Technology Comparison Study. The linear collider designs considered were based on the GLC/NLC X-band and TESLA Superconducting proposals, but modified to meet the US physics requirements. To better model some of the complexities of actual operation, a simulation program was written, which included details such as partial fixes or workarounds, hot-swappable repairs, multiple simultaneous repairs, cooldown periods before access, staged recovery from an outage, and both opportunistic and scheduled machine development. The main linacs and damping rings were modeled in detail with component counts taken from the designs, and using MTBFs and MTTRs from existing accelerator experience. Other regions were assigned a nominal overall failure rate. Variants such as a single tunnel or conventional positron source were also evaluated, and estimates made of the sensitivity to recovery or repair times. While neither design was predicted to be sufficiently reliable given present experience, the required improvements were estimated to increase the overall project cost by only a few percent.
MOPLT143	Results and Plans of the PEP-II B-Factory	luminosity, injection, beam-beam-effects, electron	875
	J. Seeman, J. Browne, Y. Cai, S. Colocho, F.-J. Decker, M.H. Donald, S. Ecklund, R.A. Erickson, A.S. Fisher, J.D. Fox, S.A. Heifets, R.H. Iverson, A. Kulikov, A. Novokhatski, M.T.F. Pivi, M.C. Ross, P. Schuh, T.J. Smith, K. Sonnad, M. Stanek, M.K. Sullivan, P. Tenenbaum, D. Teytelman, J.L. Turner, D. Van Winkle, U. Wienands, M. Woodley, Y.T. Yan, G. Yocky SLAC, Menlo Park, California M.E. Biagini INFN/LNF, Frascati (Roma) J.N. Corlett, C. Steier, A. Wolski, M.S. Zisman LBNL, Berkeley, California W. Kozanecki CEA/DSM/DAPNIA, Gif-sur-Yvette G. Wormser IPN, Orsay
	PEP-II is an e+e- B-Factory Collider located at SLAC operating at the Upsilon 4S resonance. PEP-II has delivered, over the past four years, an integrated luminosity to the BaBar detector of over 175 fb-1 and has reached a luminosity over 7.4x1033/cm2/s. Steady progress is being made in reaching higher luminosity. The goal over the next few years is to reach a luminosity of at least 2x1034/cm2/s. The accelerator physics issues being addressed in PEP-II to reach this goal include the electron cloud instability, beam-beam effects, parasitic beam-beam effects, trickle injection, high RF beam loading, lower beta y*, interaction region operation, and coupling control.
MOPLT155	Study of Beam-beam Effects at PEP-II	luminosity, simulation, damping, coupling	896
	I.V. Narsky, F.C. Porter CALTECH, Pasadena, California Y. Cai, J. Seeman SLAC, Menlo Park, California W. Kozanecki CEA/DSM/DAPNIA, Gif-sur-Yvette
	Using a self-consistent, three-dimensional simulation program running on parallel supercomputers, we have simulated the beam-beam interaction at the PEP II asymmetric e+e- collider. In order to provide guidance to luminosity improvement in PEP-II, we have scanned the tunes and other machine parameters in both rings, and computed their impact on the luminosity and particle loss. Whenever possible, the code has been benchmarked against experimental measurements, at various beam currents, of luminosity and luminous-region size using the BaBar detector. These studies suggest that three-dimensional effects such as bunch lengthening may be important to understand a steep drop of luminosity near the peak currents.
TUZACH01	Positron Source Options for Linear Colliders	target, photon, radiation, electron	69
	K. Floettmann DESY, Hamburg
	Linear colliders require sources delivering particle intensities much higher than sources for storage rings and even several orders of magnitude larger than the SLC positron source, the highest intensity positron source operated so far. A fundamental limitation for the intensity of a positron source is set by the thermal stress in the target. Besides improvements of conventional positron sources, i.e. sources where an electron beam creates electron position pairs in an electromagnetic cascade, new concepts based on the direct conversion of gamma radiation offer possibilities for increased particle intensities. In these sources the hard gamma radiation has to be produced either in an undulator or by backscattering of laser light off an electron beam. An additional advantage of gamma radiation based sources is the possibility to produce polarized positrons. The talk will give an overview of the developments of high intensity unpolarized and polarized positron sources for linear colliders.
	Video of talk
	Transparencies
TUPLT037	Dispersion Correction in HERA	closed-orbit, luminosity, polarization, electron	1228
	J. Keil, W. Decking DESY, Hamburg
	The electron-proton collider HERA at the DESY laboratory in Hamburg has been in operation since 1991. After the luminosity upgrade of HERA in 2001 the control of the horizontal and vertical dispersion function of the positron beam became more important than before. Deviations from the design dispersion in the horizontal plane can change the emittance of the electron beam significantly thus leading to a reduction of the luminosity. For optimizing the polarization of the electron beam the reduction of vertical orbit and dispersion deviations is important. In this paper the combined dispersion and orbit correction in HERA is described and first results are reported.
TUPLT104	Particle Dynamics in the Low Energy Positron Toroidal Accumulator: First Experiments and Results	electron, septum, quadrupole, kicker	1396
	G.V. Troubnikov, V. Antropov, E. Boltushkin, V. Bykovsky, A.I. Ivanov, S. Ivashkevich, A. Kobets, I.I. Korotaev, V. Lohmatov, I.N. Meshkov, D. Monahov, V. Pavlov, R. Pivin, I.A. Seleznev, A.O. Sidorin, A. Smirnov, E. Syresin, S. Yakovenko JINR, Dubna, Moscow Region
	The project of Low Energy Particle Toroidal Accumulator (LEPTA) is dedicated to construction of a positron storage ring with electron cooling of positrons circulating in the ring. Such a peculiarity of the LEPTA enables it automatically to be a generator of positronium (Ps) atoms, which appear in recombination of positrons with cooling electrons inside the cooling section of the ring. The project has a few goals: to study electron and positron dynamics in the ring (particle motion in the horizontal and vertical planes are coupled contrary to of classic cycle accelerators), to set up first experiments with Ps in flight; Magnetic measurements of main LEPTA elements are performed. Several elements : kicker, injection system of electron beam, helical quadrupole, septum magnet are tested and expected design parameters were achieved for those elements. The investigations of electron beam dynamics are started. First results of experiments with circulating electron beam are presented and discussed in this article. Several beam diagnostic methods for studying of strong coupled motion of charged particles are proposed and tested.
TUPLT113	Technicalities for a Novel Medium Energy Ion Accelerator	ion, vacuum, proton, heavy-ion	1411
	V. Gorev RRC Kurchatov Institute, Moscow
	Transmutation of radioactive waste,high-intensity pulsed sources of fast neutrons,problem of inertially-confined fusion and a lot of different problems of science and technology put increased demands on the linear high power medium energy proton and heavy ion accelerators.But these accelerators are presently massive,huge and very expansive,which restrict now and in a near future their wide use and motivates the study of altenetive methods to achieve the design current,power and economic characteristics.This report decribes the present reseach on attaining high power medium energy ion beams,using novel idea for accelerator design.Theoretical proposal and preliminary conceptual design for the accelerator,based on a principle of free flying ion emitter("ballistic anode"),were discussed first a few years ago.The principle involves a high potencial difference generated only for a short time in the special vacuum chamber,but not steady-state conditions.Now,we would like to discuss next problems:1.technicalities of the ballistic anode design,both for proton and heavy ion beams generation.2 pulse power multiplication.3.high current sources for charge pumping of the ballistic anode.4 experimental modelling.
WEPKF080	Secondary Electron Yield Measurements from Thin Surface Coatings for NLC Electron Cloud Reduction	electron, vacuum, damping, luminosity	1789
	F. Le Pimpec, F. King, R.E. Kirby, M.T.F. Pivi SLAC, Menlo Park, California
	In the beam pipe of the positron damping ring of the Next Linear Collider, electrons will be created by beam interaction with the surrounding vacuum chamber wall and give rise to an electron cloud. Several solutions are possible for avoiding the electron cloud, without changing the beam bunch structure or the diameter of the vacuum chamber. Some of the currently available solutions include reducing residual gas ionization by the beam, minimizing photon-induced electron production, and lowering the secondary electron yield (SEY) of the chamber wall. We will report on recent SEY measurements performed at SLAC on TiN coatings and TiZrV non-evaporable getter thin films.
WEPLT105	Beam-Beam Effects Measured Using Gated Monitors at KEKB	luminosity, emittance, electron, betatron	2095
	T. Ieiri, Y. Funakoshi, T. Kawamoto, M. Masuzawa, M. Tawada, M. Tobiyama, S.S. Win KEK, Ibaraki
	KEKB is a multi-bunch, high-current, electron/positron collider for B meson physics. The two beams collide at one interaction point (IP) with a finite horizontal crossing angle and with a bunch-space of 6 to 8 ns. The luminosity of KEKB is the best in the world. The collision is performed by carefully adjusting a horizontal orbit bump of the electron beam at IP, which results in a horizontal offset to obtain the best luminosity. In order to investigate the asymmetric beam-beam effects, beam parameters of collision and non-collision bunches were compared using beam monitors capable of selecting a specific bunch in a bunch train. The beam-beam kick and the beam-beam tune-shift were obtained by the gated beam-position monitor and by the gated tune monitor. It was found that the horizontal offset was negligibly small in the case of a wide bunch-space of 48 ns. This result suggests that the horizontal offset is related to wake fields including electron-cloud effects.
WEPLT155	Effect of Dark Currents on the Accelerated Beam in an X-band Linac	electron, simulation, cathode, emittance	2203
	V.A. Dolgashev SLAC/ARDA, Menlo Park, California K.L.F. Bane, G.V. Stupakov, J. Wu SLAC, Menlo Park, California T.O. Raubenheimer SLAC/NLC, Menlo Park, California
	X-band accelerating structures operate at surface gradients up to 120-180 MV/m. At these gradients, electron currents are emitted spontaneously from the structure walls ("dark currents") and generate additional electromagnetic fields inside the structure. We estimate the effect of these fields on the accelerated beam in a linac using two methods: a particle-in-cell simulation code MAGIC and a particle tracking code. We use the Fowler-Nordheim dependence of the emitted current on surface electric field with field enhancement factor beta. In simulations we consider geometries of traveling wave structures that have actually been built for the Next Linear Collider project.
WEPLT157	Single-bunch Electron Cloud Effects in the GLC/NLC, US-cold and TESLA Low Emittance Transport Lines	electron, emittance, collider, focusing	2209
	M.T.F. Pivi, D. Bates, A. Chang, D. Chen, T.O. Raubenheimer SLAC, Menlo Park, California
	In the beam pipe of the Beam Delivery System (BDS) and Bunch Compressor system (BCS) of a linear collider, ionization of residual gasses and secondary emission may lead to amplification of an initial electron signal during the bunch train passage and ultimately give rise to an electron-cloud. A positron beam passing through the linear collider beam delivery may experience unwanted additional focusing due to interaction with the electron cloud. This typically leads to an increase in the beam size at the interaction point (IP) when the cloud density is high. Interaction with the electron cloud in the bunch compressor could also potentially cause an instability. This paper examines the severity of the electron cloud effects in the BCS and BDS of both the GLC/NLC and US-Cold linear collider design through the use of specially developed simulation codes. An estimate of the critical cloud density is given for the BDS and BCS of both designs.
THPLT026	Beam Profile Measurements at PETRA with the Laserwire Compton Scattering Monitor	laser, photon, background, collider	2529
	T.  Kamps BESSY GmbH, Berlin K. Balewski, H.-C. Lewin, S. Schreiber, K. Wittenburg DESY, Hamburg G.A. Blair, G. Boorman, J. Carter, F. Poirier Royal Holloway, University of London, Surrey S.T. Boogert UCL, London T. Lefevre CERN, Geneva
	The vertical beam profile at the PETRA positron storage ring has been measured using a laserwire scanner. A laserwire monitor is a device which can measure high brilliant beam profiles by scanning a finely focused laser beam non-invasively across the charged particle beam. Evaluation of the Compton scattered photon flux as a function of the laser beam position yields the transverse beam profile. The aim of the experiment at PETRA is to obtain the profile of the positron beam at several GeV energy and several nC bunch charge. Key elements of laserwire systems are currently being studied and are described in this paper such as laser beam optics, a fast scanning system and a photon calorimeter. Results are presented from positron beam profile scans using orbit bumps and a fast scanning scheme.
THPLT056	Horizontal Instability and Feedback Performance in DAFNE e+ Ring	feedback, damping, pick-up, injection	2613
	A. Drago INFN/LNF, Frascati (Roma)
	In DAFNE, after the 2003 shutdown for the installation of FINUDA, a strong horizontal multibunch instability was found to limit the positron beam current at the level of ~450 mA. We have performed transverse grow-damp measurements in order to estimate the instability growth rates as well as the feedback damping rates for each bunch at different beam currents and to evaluate the tune shift along the bunch train. In particular, a strong dependence of oscillation amplitudes on the relative position of the bunch in the train has been observed. In this paper we describe the setup for multibunch oscillation amplitude recording, discuss the transverse feedback performance and summarize some observations on the transverse instability. The feedback rises the threshold by about a factor of two, depending on the machine configuration.
THPLT109	The Upgraded Optical Diagnostic of the VEPP-4M Collider	diagnostics, electron, collider, booster	2739
	O.I. Meshkov, M.G. Fedotov, V.F. Gurko, A.D. Khilchenko, N.Y. Muchnoi, Yu.A. Pakhotin, N.A. Selivanov, A.N. Zhuravlev, E.I. Zinin, P.V. Zubarev BINP SB RAS, Novosibirsk
	The upgraded optical diagnostic of the VEPP-4M collider is described. The system abilities are improved sufficiently in comparing with the previous version. Now the diagnostic supplies the data about an electron/positron beam transversal and longitudinal size, shape and position. It is applied to study the electron beam "tails" and turn-to-turn beam profile dynamics. The system is used to tune of the beam pass-by from the VEPP-3 booster to the VEPP-4M collider and provides the permanent measurements of the synchrotron and betatron frequencies.
THPLT122	The Energy Deposition Profile of 0.1-3.0 MeV Electrons in NaCl	electron, target, scattering, radiation	2756
	V.V. Gann NSC/KIPT, Kharkov A.V. Sugonyako, D.I. Vainshtein, H.W. den Hartog RUG, Groningen
	An analysis is presented of existing experimental and theoretical data of energy loss profiles and energy deposition in thick targets irradiated with MeV-energy electrons. A simple approximate calculation is proposed for the energy deposition profile of a perpendicular beam of 0.1-3 MeV electrons in matter. The results obtained with this method are in agreement with existing calculated and measured energy absorption profiles for a variety of materials. It will be shown that the build-up phenomenon has a significant effect on the energy deposition profile in thick samples. A systematic experimental investigation of the energy deposition profile of 0.5 MeV electrons in 0.2 - 0.8 mm thick NaCl platelets has been carried out. The distribution of the absorbed dose was determined with differential scanning calorimetry method by measuring either the latent heat of melting of the radiation-induced Na-precipitates or the stored energy.
THPLT151	Evaluation of Beam Position Monitors in the Nonlinear Regime	betatron, closed-orbit, electron, coupling	2810
	R.W. Helms, G. Hoffstaetter Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
	Here we present a new algorithm for processing BPM signals and extracting orbit and phase data for very large beam excursion where the BPM response function changes nonlinearly with the beam position. Using two dimensional models of each BPM geometry, we calculate the button response using numerical solution of Laplace's equation and Green's reciprocity theorem. The difference between the calculated signals and the measured signals is minimized in real time to calculate the beam position and measurement errors. Using the derivatives of the response functions, we model the effect of beam shaking, and from it, calculate the betatron phase.
THPLT154	Design of an X-ray Imaging System for the Low-Energy Ring of PEP-II	photon, dipole, vacuum, radiation	2819
	A.S. Fisher, D. Arnett, H. De Staebler, S. Debarger, R.K. Jobe, D. Kharakh, D.J. McCormick, M. Petree, M.C. Ross, J. Seeman, B. Smith SLAC, Menlo Park, California J. Albert, D. Hitlin CALTECH, Pasadena, California J. Button-Shafer, J.A. Kadyk LBNL, Berkeley, California
	An x-ray beam-size monitor for positrons in the low-energy ring (LER) of the PEP-II B Factory at SLAC is being designed to accommodate the present 2-A, 3.1-GeV beam and anticipated currents of up to 4.7 A. The final photon stop of an arc will be rebuilt to pass dipole radiation through cooled apertures to optics 17 m from the source. Zone-plate imaging there can achieve a resolution of 6 microns, compared to 35 for a pinhole camera. Two multilayer x-ray mirrors precede the zone plate, limiting the bandwidth to 1%, in order to avoid chromatic blurring and protect the zone plate. Despite the narrow bandwidth, the zone plate?s larger diameter compared to a pinhole camera allows for a comparable photon flux. We will image all 1700 LER bunches and also measure them individually, searching for variations along the train due to electron-cloud and beam-beam effects, using a scanning detector conceptually derived from a wire scanner. A mask with three narrow slots at different orientations will scan the image to obtain three projections. In one passage, signals from a fast scintillator and photomultiplier will be rapidly digitized and sorted to profile each bunch.