IPAC2013 - List of Keywords (positron)

Paper	Title	Other Keywords	Page
MOPFI011	Construction and First Tests of the New Injection System for the Linac II at DESY	linac, electron, gun, injection	303
	C. Liebig, M. Hüning, M. Schmitz DESY, Hamburg, Germany
	For the Linac II, which supplies the accelerator chain at DESY with electrons and positrons, a new injection system is planned. It is supposed to ensure reliable operation and to avoid the beam loss of about 60% at energies up to 400 MeV and the associated activation. The function of the injector components, the entire injection system and the acceleration in the linac sections were optimized in simulations. The main components are a 6 A/100 kV triode gun, buncher and a dispersive section for energy collimation. The output energy is 5 MeV and the beam pulse length can be chosen from 5 ns to 50 ns. The new buncher structure is a hybrid of a standing wave and traveling wave structure and allows a compact design and good electron capture. One of two assembled structures has been tuned and completed a test rig in the linac tunnel. In this test system detailed analysis of its properties is in progress as well as minor corrections like alignment and improvements of reliability. The final installation is going to take place from September 2013. First experimental analysis compared to simulation results will be presented.

MOPFI017	SuperKEKB Positron Source Target Protection Scheme	target, electron, radiation, simulation	315
	L. Zang, T. Kamitani KEK, Ibaraki, Japan
	The SuperKEKB requires an intense beam with a large number of positrons, which is generated by a high energy electron beam strike on a solid tungsten target. The cascade shower in the target deposits large amount of energy in the material leading to target damage. The pulsed electron beam distributed the energy non-uniformly over the target. In that case, a mechanical stress appears due to the large thermal gradient during each pulse, which could potentially destroy the target. Based on the analysis of the SLAC damaged target, peak energy deposition density (PEDD) should not exceed 35 J/g to ensure a long term of safe operation. One way of reducing PEDD is increasing the beam spot size. Hence we proposed a target protection scheme, in which a protection target is placed upstream of generation target as a spoiler. The aim is to maintain the generation target’s PEDD below 35 J/g even with a point primary electron beam. In this paper, we will introduce graphite, aluminum and copper as the protection target material candidates. And also present the PEDD and positron yield evaluation as a function of various parameters such as protection target thickness and drift space.

MOPFI018	Design Study of a New Large Aperture Flux Concentrator	target, simulation, solenoid, focusing	318
	L. Zang, M. Akemoto, S. Fukuda, K. Furukawa, T. Higo, K. Kakihara, T. Kamitani, Y. Ogawa, H. Someya, T. Takatomi KEK, Ibaraki, Japan
	For high luminosity electron-positron colliders, intense positron beam production is one of the key issues. Flux Concentrator (FC) is a pulsed solenoid that can generate high magnetic field of several Tesla and is often used for focusing positrons emerged from a production target. It works as an optical matching device in a positron capture section. With this device, high capture efficiency is achieved. In this paper, we will introduce a new design of a FC for the SuperKEKB positron source. The advantages of the new design are: 1. the aperture could be doubled of the previous design, 2. the transverse components are only 1/10 of the previous design, 3. maintain the same high peak longitudinal field. The new FC modeling has been done in CST Studio and we will report the results of new FC field evaluation. In order to calculate the positron yield and capture efficiency, a tracking simulation to the end of capture section has also been carried out, which is also included in this paper.

MOPME004	Fast Luminosity Monitoring using Diamond Sensors for Super Flavour Factories	luminosity, scattering, photon, electron	473
	C. Rimbault, P. Bambade LAL, Orsay, France
	Super flavour factories aim to reach very high luminosities thanks to a new concept whereby the ultra-low emittance beams collide with a large crossing angle. Fast luminosity measurements are needed as input to luminosity optimization and feedback in the presence of dynamic imperfections. The required small relative precision can be reached exploiting the very large cross section of the radiative Bhabha process at zero photon scattering angle. The instrumental technique selected to sustain the large particle fluxes is based on diamond sensors to be positioned via moveable stages immediately outside the beam pipe, at locations chosen to minimize the contamination from other particle loss mechanisms.

MOPME031	Emittance Measurement with Multi-wire Scanners for BEPC-II Linac	emittance, linac, electron, injection	541
	H. Geng, W.B. Liu, W. Qiao, Q. Qin, Y.F. Sui, Y. Yue IHEP, Beijing, People's Republic of China
	During the BEPC-II linac upgrade, five wire scanners have been installed in the common transport line, which makes a fast emittance measurement possible. In this paper, we will show the primary results of BEPC-II linac emittance measurement using multi-wire scanner method. The least squares method will be used for data analysis. A comparison of the results with the ones obtained by quad scan method will also be given.

MOPWA071	A Comparison of Electron Cloud Density Measurements at CesrTA	electron, simulation, resonance, pick-up	843
	J.P. Sikora, J.A. Crittenden, D.O. Duggins, Y. Li, X. Liu CLASSE, Ithaca, New York, USA S. De Santis LBNL, Berkeley, California, USA
	Funding: This work is supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the US Department of Energy DE-FC02-08ER41538, DE-SC0006505. Several techniques have been employed to measure the electron cloud (EC) density in accelerators. These include Time Resolved Retarding Field Analyzers (TR-RFA) and Shielded Pickups (SPU) that measure the flux of cloud electrons onto the beam-pipe wall, as well as TE wave resonance techniques that measure the EC density in a region within the volume of the beam-pipe. We have made measurements to test the EC mitigation properties of different surface coatings and geometries, often with more than one technique used in the same test chamber. We present a comparison of bare aluminum chambers with those having a TiN coating, as well as the effect of beam conditioning. In addition, we will compare the results of the different measurement techniques used in the same chamber. These measurements were made at the Cornell Electron Storage Ring (CESR) which has been reconfigured as a test accelerator (CesrTA) having positron or electron beam energies ranging from 2 GeV to 5 GeV.

MOPWA072	MODELING FOR TIME-RESOLVED RETARDING FIELD ANALYZER MEASUREMENTS OF ELECTRON CLOUD BUILDUP AT CesrTA	electron, vacuum, dipole, pick-up	846
	J.A. Crittenden, Y. Li, X. Liu, M.A. Palmer, J.P. Sikora CLASSE, Ithaca, New York, USA
	Funding: US National Science Foundation PHY-0734867, PHY-1002467, and the U.S. Department of Energy DE-FC02-08ER41538 The Cornell Electron Storage Ring Test Accelerator program includes investigations into electron cloud buildup mitigation techniques using custom vacuum chambers. Multibunch electron and positron beams of energies between 2.1 and 5.3 GeV with bunch spacings from 4 to 98 ns and bunch populations ranging from 10¹⁰ to 16·10¹⁰ provide highly differentiated sensitivity to the processes contributing to cloud buildup such as photoelectron production, cloud space-charge dynamics, and secondary electron emission. Measurements of the time dependence of cloud buildup using BPM-style shielded pickups have been shown to provide tight constraints on cloud buildup models. Recently, time-resolving retarding-field analyzers have been designed, installed and commissioned. These novel detectors combine the time-resolving feature of the shielded pickups with the fine transverse segmentation and cloud electron energy sensitivity of the time-integrating retarding-field analyzers used previously. We report on progress in modeling these measurements and quantify their sensitivity to various parameters describing the underlying physical processes contributing to cloud buildup.

MOPWA078	The Calibration of the PEPPo Polarimeter for Electrons and Positrons	electron, photon, target, polarization	861
	A.H. Adeyemi JLAB, Newport News, Virginia, USA E. J-M. Voutier LPSC, Grenoble, France
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 The PEPPo (Polarized Electrons for Polarized Positrons) experiment at Jefferson Laboratory investigated the polarization transfer from longitudinally polarized electrons to longitudinally polarized positrons, with the aim of developing this technology for a low energy (~MeV) polarized positron source. Polarization of the positrons was measured by means of a Compton transmission polarimeter where incoming positrons transfer their polarization into circularly polarized photons that were subsequently analyzed by a thick polarized iron target. The measurement of the transmitted photon flux with respect to the orientation of the target polarization (±) or the helicity (±) of the incoming leptons provided the measurement of their polarization. Similar measurements with a known electron beam were also performed for calibration purposes. This presentation will describe the apparatus and calibrations performed at the injector at the Jefferson Laboratory to measure positron polarization in the momentum range 3.2-6.2 MeV/c, specifically to quantify the positron analyzing power from electron experimental data measured over a comparable momentum range. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes

MOPWA079	Characterization of the Analyzing Target of the PEPPo Experiment	target, polarization, photon, electron	864
	O. Dadoun LAL, Orsay, France E. Froidefond, E. J-M. Voutier LPSC, Grenoble, France
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 Various methods have been investigated over the past decades for the production of polarized positrons. The purpose of the PEPPo (Polarized Electrons for Polarized Positrons) experiment is to demonstrate, for the first time, the production of polarized positrons from a polarized electron beam. This two-step process involves the production of circularly polarized photons in a high Z target via the bremsstrahlung process followed, within the same target, by the conversion of polarized photons into polarized e⁺e⁻ pairs through the pair creation process. The PEPPo experiment was performed in Spring 2012 at the injector of the Jefferson Laboratory using a highly spin-polarized (~85%) 8.3 MeV/c electron beam. The positron polarization was measured by means of a Compton transmission polarimeter over the momentum range from 3.2 MeV/c to 6.2 MeV/c. This presentation will discuss the experimental set-up with a special emphasis on the analyzing magnet constituting the polarization filter of the experiment. The knowledge of the analyzing target polarization will be discussed on the basis of simulations and calibrated to experimental data The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes

TUYB101	Progress in Super B-Factories	emittance, luminosity, linac, alignment	1096
	K. Akai KEK, Ibaraki, Japan
	The upgrade of B-Factories to Super B-Factories, which will search for new physics beyond the Standard Model, opens the way for new luminosity frontier. The status of Super B-Factories will be reported.
	Slides TUYB101 [42.300 MB]

TUYB102	Summary of the ILC R&D and Design	electron, linac, damping, cavity	1101
	B.C. Barish CALTECH, Pasadena, California, USA
	This talk should provide a summary of the main activities of ILC-GDE since 2005, and an overview of the Technical Design Report with prospects for the next steps for the future.
	Slides TUYB102 [6.544 MB]

TUPEA021	Calculation of Wakefields in Plasma Filled Dielectric Capillaries Generated by a Relativistic Electron Beam	plasma, wakefield, electron, collider	1205
	C. Li, W. Gai ANL, Argonne, USA C. Li, C.-X. Tang, H. Zha TUB, Beijing, People's Republic of China
	In this paper we give an analytical solution of TM0n mode for wakefields generated by a relativistic electron beam passing through plasma-filled capillary waveguides. The numerical solution shows that the fields of TM0n modes could not be ignored when the plasma wave length is comparable with the effective radius of the capillary tube, which means that the boundaries are not shielded completely by plasma. Numerical examples are given in several typical cases.

TUPEA045	Self-Modulation and Hosing Instability of Slac Electron and Positron Bunches in Plasmas	electron, plasma, wakefield, simulation	1235
	J. Vieira, N.C. Lopes Instituto Superior Tecnico, Lisbon, Portugal E. Adli, S.J. Gessner, M.J. Hogan, S.Z. Li, M.D. Litos SLAC, Menlo Park, California, USA Y. Fang USC, Los Angeles, California, USA C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi UCLA, Los Angeles, California, USA P. Muggli MPI, Muenchen, Germany O. Reimann MPI-P, München, Germany L.O. Silva IPFN, Lisbon, Portugal
	Funding: This work has been partially supported by Humboldt Foundation. The understanding of the self-modulation (SMI) and hosing (HI) instabilities is critical for the success of the upcoming proton driven plasma wakefield acceleration experiments at CERN. The use of long SLAC electron and positron bunches provides the possibility of understanding experimentally the interplay between SMI and HI. In this work we perform particle-in-cell simulations with the code OSIRIS with parameters that will be available for experiments at SLAC in 2013. We show that the SMI of 20 GeV lepton bunches can grow and saturate in less than 15 cm. Up to 8 GeV energy gain/loss could be observed after a meter long plasma. The HI can also be effectively mitigated by seeding the SMI using bunches with short rise times. We also show analytically and numerically that in the linear regime and after saturation of the SMI the HI can be suppressed by a plasma-BNS damping analogue. Several diagnostics that could be used in experiments to measure the SMI development and these effects are also explored. G. Xia et al., J. Plasma Phys., 1-7 (2012). **J. Vieira et al., Phys. Plasmas 19, 063105 (2012).

TUPME002	Design Integration at the International Linear Collider	lattice, electron, damping, civil-engineering	1559
	B. List, L. Hagge, J. Kreutzkamp, N.J. Walker DESY, Hamburg, Germany
	In preparation for the Technical Design Report of the International Linear Collider, a comprehensive design of the accelerator has been compiled. DESY has contributed a systematic design integration approach, which helps to achieve a complete, correct and consistent design. We use the lattice as the leading element for design integration. Geometry information including 3D visualization models are derived from the lattice, and are used to ensure that the beamlines fit and suited for access and installation. The 3D models are also used as basis for tunnel and cavern layout. As detailed designs of components become available, the lattice is adjusted and the overall models are iterated. Lists of components are derived from the lattice and are used to generate a component bill of materials, which in turn serves as basis for cost estimation and installation planning. An integrated 3D model of the entire accelerator and all the civil construction elements helps to optimize the design for example with regard to space efficiency, ease of access for installation, and life safety. Setting up design integration in an early project stage results in a better design helps to reduce costs.

TUPME003	Simulations of the ILC Positron Source at Low Energies	undulator, target, electron, polarization	1562
	A. Ushakov, V.S. Kovalenko, G.A. Moortgat-Pick University of Hamburg, Hamburg, Germany S. Riemann, F. Staufenbiel DESY Zeuthen, Zeuthen, Germany
	Funding: This work is supported by the German Federal Ministry of Education and Research, Joint Research Project R&D Accelerator "Spin Optimization", contract number 19XL7Ic4 The International Linear Collider (ILC) baseline design includes an undulator-based positron source. The accelerated electron beam will be used for the positron generation before it goes to the collision point. For the whole ILC energy range the source has to generate 1.5 positrons per electron. However, the efficiency of positron production goes down with decreasing electron drive beam energy. This effect can be compensated to some extend by the choice of undulator parameters and an optimized capture section. The simulation study considers for the range of electron beam energies down to low values of 120 GeV the feasibility to achieve the required positron yield. In particular, the optimum parameters for undulator and capture section are presented depending on the drive electron beam energy.

TUPME004	Spin Tracking at the International Linear Collider	resonance, dipole, polarization, damping	1565
	V.S. Kovalenko, G.A. Moortgat-Pick, A. Ushakov University of Hamburg, Hamburg, Germany S. Riemann DESY Zeuthen, Zeuthen, Germany M. Vogt DESY, Hamburg, Germany A. Wolski Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work is supported by the German Federal Ministry of Education and Research, Joint Research Project R&D Accelerator "Spin Optimization", contract number 19XL7Ic4 In the baseline design for the International Linear collider an helical undulator-based positron source has been chosen that can provide positrons with a polarization of 60% as an upgrade option motivated by physics reasons. But even the baseline configuration would already provide about 30%. In order to match the high precision requirements from physics and to optimize the physics outcome one has to control systematic uncertainties to a very high level. Therefore it is needed to run both beams polarized but provide also an unpolarized set-up for control reasons. In our study we present results on precise spin tracking and propose also an minimal machine set-up to run in an unpolarized mode within the baseline design.

TUPME006	Simulation of Stress in Positron Targets for Future Linear Colliders	target, photon, undulator, electron	1571
	F. Staufenbiel, S. Riemann DESY Zeuthen, Zeuthen, Germany O.S. Adeyemi, V.S. Kovalenko, G.A. Moortgat-Pick, A. Ushakov University of Hamburg, Hamburg, Germany
	Future linear collider projects require intense positron sources with yields of about 10¹⁴ positrons per second. The positron source for the ILC is based on a helical undulator passed by the accelerated electron beam to create an intense circularly polarized photon beam. The positron beam produced by these photons is longitudinally polarized. The intense photon beam causes rapid temperature increase in the target material resulting in periodic stress. The average and peak thermal and mechanical load are simulated. Implications due to long-term target irradiation are considered.

TUPME008	Beam Dynamics Studies for the Injection System of a High Luminosity Flavour Factory	linac, injection, electron, luminosity	1577
	D. Pellegrini CERN, Geneva, Switzerland M.E. Biagini, S. Guiducci INFN/LNF, Frascati (Roma), Italy
	The requirements, in terms of average luminosity and lifetimes, of high luminosity e⁺e⁻ colliders such as the Flavor factories, pose stringent constraints to the design of the injection complex. For the SuperB B-factory project at Tor Vergata, Italy, a design was developed to deliver full energy bunches (4.2 GeV e^- and 6.7 GeV e+) to the main rings every 30 ms aiming at a high and nearly constant luminosity. The system included a polarized electron gun, a positron production system, linac sections, a Damping Ring (DR) and transfer lines connecting to the collider Main Rings (MR). After the decision, due to budget issues, to rescale the project to a lower energy (2.3 GeV/beam) for a tau/charm flavour factory, the same design principles have been applied. In this paper beam dynamics studies from the DR to the MR entrance is presented, including optimization of the transfer lines and of the bunch compressor. A start to end simulation shows that the beam quality satisfies theinjection requirements, even in the presence of energy errors and collective effects like CSR and wakefields.

TUPME010	High-intensity and Low-emittance Upgrade of 7-GeV Injector Linac towards SuperKEKB	emittance, linac, electron, laser	1583
	K. Furukawa, M. Akemoto, D.A. Arakawa, Y. Arakida, A. Enomoto, S. Fukuda, H. Honma, R. Ichimiya, N. Iida, M. Ikeda, E. Kadokura, K. Kakihara, T. Kamitani, H. Katagiri, M. Kurashina, S. Matsumoto, T. Matsumoto, H. Matsushita, S. Michizono, K. Mikawa, T. Miura, F. Miyahara, T. Mori, H. Nakajima, K. Nakao, T. Natsui, Y. Ogawa, S. Ohsawa, F. Qiu, M. Satoh, T. Shidara, A. Shirakawa, H. Sugimoto, T. Suwada, T. Takatomi, T. Takenaka, M. Tanaka, Y. Yano, K. Yokoyama, M. Yoshida, L. Zang, X. Zhou KEK, Ibaraki, Japan D. Satoh TIT, Tokyo, Japan
	After a decade of successful operation at KEKB a new electron/positron collider, SuperKEKB, is being constructed to commission within FY2014. It aims at a luminosity of 8 x 10³⁵ /s.cm², 40-times higher than that of KEKB, in order to study the flavor physics of elementary particles further, by mainly squeezing the beams at the collision point. The injector linac should provide high-intensity and low-emittance beams of 7-GeV electron and 4-GeV positron by newly installing a RF-gun, a flux concentrator, and a damping ring with careful emittance and energy management. It also have to perform simultaneous top-up injections into four storage rings by pulse-to-pulse beam modulations not to interfare between three facilities of SuperKEKB, Photon Factory and PF-AR. This paper describes the injector design decisions and present status of the construction.

TUPME015	Proposal of Polarized Gamma-ray Source for ILC Based on CSR Inverse Compton Scattering	electron, cavity, scattering, laser	1598
	M. Shimada, K. Yokoya KEK, Ibaraki, Japan R. Hajima JAEA, Ibaraki-ken, Japan M. Tecimer University of Hawaii at Manoa, Honolulu, USA
	The positron source of International Linear Collider (ILC) requires a circular polarized gamma-ray with a flux more than 10¹⁶ phs./s and a helical undulator-based gamma-ray source is proposed in the baseline design. Although the undulator scheme is technically feasible, it is not easy for a stand-alone operation because of the required electron energy, ~ 150GeV. In this paper, we propose an alternative method, the inverse Compton scattering with a high-power mid-infrared optical pulse generated from coherent synchrotron radiation (CSR). To achieve the high flux gamma-ray, CSR with a few MHz is stacked in a high-finesse optical cavity made of a photonic crystal. In the proposed scheme, a stand-alone operation is feasible because the electron energy is less than 10GeV.

TUPME028	RF Orbit Separation for CPT-Test Experiment at VEPP-4M	electron, betatron, closed-orbit, beam-beam-effects	1634
	V.E. Blinov, E.A. Bekhtenev, G.V. Karpov, V.A. Kiselev, S.A. Krutikhin, G.Y. Kurkin, E.B. Levichev, O.I. Meshkov, S.I. Mishnev, V.V. Neyfeld, S.A. Nikitin, I.B. Nikolaev, D.N. Shatilov, G.M. Tumaikin BINP SB RAS, Novosibirsk, Russia A.P. Chabanov, O.P. Gordeev, A.I. Mickailov Budker INP & NSU, Novosibirsk, Russia
	Funding: This work was supported by the Ministry of Education and Science of the Russian federation and the Russian Foundation for Basis Research (grant 11-02-01422-a) In a special program of experiments which is under development in a background regime at the VEPP-4M storage ring we set an aim to realize a potential possibility to make the CPT invariance test with the accuracy better than 10^-8. The test will be based on a precise comparison of the spin precession frequencies of simultaneously stored electrons and positrons. To exclude the presence of static electric fields increasing a systematic error we have developed and tested a special RF system driven at the half revolution frequency to subsitute for the electrostatic orbit separation system. The latter is needed for the electron and positron orbit separation at the parasitic interaction point where the beam-beam effects drastically cut the beam currents.

TUPME029	VEPP-4: Application Beyond the High Energy Physics	electron, collider, radiation, target	1637
	O.I. Meshkov BINP SB RAS, Novosibirsk, Russia
	The current status of VEPP-4M electron-positron collider has been described. During fall of 2011 the accelerator was shut down for planned reconstruction of KEDR detector. The next long run of the collider will be dedicated to the experiments at high energy physics within area of 2-5 GeV. Nevertheless, the set of experiments at booster VEPP-3 were continued. VEPP-3 was operated as an SR source, the experiment with internal target was performed and electron/positron scattering at proton was studied. The short runs of VEPP-4M were used as for commissioning of the new “warm” 3T wiggler as for experiments with an extracted electron beam dedicated for testing of different high energy physics detectors. The experiment of comparing of anomalous magnetic moment of electron and positron is con-tinued at VEPP-4M. The system of RF beam shifting is installed at a straight section of the accelerator. It is applied for elimination of parasitic interaction points of electron and positron beams. The first experiments with this system are described. KEDR detector reconstruction should be finished at autumn of 2013. The future experiments with KEDR detector are discussed.

TUPME056	3.5 GeV Superconducting Stacking Ring for Compton Based Polarized Positrons Source of CLIC	injection, damping, synchrotron, emittance	1697
	E.V. Bulyak, P. Gladkikh, A.A. Kalamayko NSC/KIPT, Kharkov, Ukraine T. Omori, J. Urakawa, K. Yokoya KEK, Ibaraki, Japan L. Rinolfi, F. Zimmermann CERN, Geneva, Switzerland
	This paper describes 3.5 GeV superconducting storage ring dedicated to positron accumulation as part of a polarized positron source for CLIC, based on Compton scattering in a Compton storage ring. The superconducting stacking ring can provide a synchrotron damping time of order 250 microseconds. Together with combined injection scheme in the longitudinal and transverse plane, such a ring may solve the problem of accumulating a positron beam with efficiency close to 95 % and with the beam intensity required for CLIC.

TUPWA061	Observation at CesrTA of the Reduction of the Vertical Beam Size of the Lead Bunch in a Train Due to the Presence of a Precursor Bunch	electron, dipole, feedback, simulation	1841
	M.G. Billing, K.R. Butler, G. Dugan, M.J. Forster, R.E. Meller, G. Ramirez, N.T. Rider, K.G. Sonnad, H.A. Williams CLASSE, Ithaca, New York, USA J.W. Flanagan KEK, Ibaraki, Japan R. Holtzapple, M. Randazzo CalPoly, San Luis Obispo, California, USA M.A. Palmer Fermilab, Batavia, USA
	Funding: Work supported by DOE Award DE-FC02-08ER41538, NSF Award PHY-0734867, PHY-1068662 and the Lepton Collider R&D Coop Agreement: NSF Award PHY-1002467. Electron cloud-induced beam dynamics is being studied at CesrTA under various conditions. These measurements make use of instrumentation for the detection of the coherent self-excited spectrum for each bunch within the train and bunch-by-bunch vertical beam size. In the position spectrum coherent betatron dipole and head-tail motion is detectable for each individual bunch within the train. These techniques are utilized to study the electron cloud-related interactions, which cause the growth of coherent motion and beam size along the train. We report on the observations of the vertical enlargement of the first bunch(es) in 30 bunch-long trains. We also report that the addition of a precursor bunch following the train of bunches and before the start of the next train can counteract the vertical enlargement of the first bunch(es) in the train. Results from these observations will be presented.

TUPWA062	Dependence of Beam Instabilities Caused by Electron Clouds at CesrTA on Variations in Bunch Spacing and Chromaticity	electron, damping, dipole, resonance	1844
	M.G. Billing, K.R. Butler, G. Dugan, M.J. Forster, R.E. Meller, M.A. Palmer, G. Ramirez, N.T. Rider, K.G. Sonnad, H.A. Williams CLASSE, Ithaca, New York, USA R.F. Campbell, R. Holtzapple, M. Randazzo CalPoly, San Luis Obispo, California, USA J.W. Flanagan KEK, Ibaraki, Japan
	Funding: Work supported by DOE Award DE-FC02-08ER41538, NSF Award PHY-0734867 and the Lepton Collider R&D Coop Agreement: NSF Award PHY-1002467 Experiments have been performed at the Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) to probe the interaction of the electron cloud with a 2.1 Gev stored positron beam. The purpose of these experiments was to characterize the dependence of beam–electron cloud interactions on the bunch spacing and the vertical chromaticity. These experiments were performed on a 30-bunch positron train, at a fixed current of 0.75mA/bunch. The bunch spacing was varied between 4 and 28 ns at three different vertical chromaticity settings. The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 1) a gated Beam Position Monitor (BPM) and spectrum analyzer to measure the bunch-by-bunch frequency spectrum of the bunch trains; 2) an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the observations from these experiments and analyze the effects of the electron cloud on the stability of bunches within these different trains.

TUPWA063	Dependence of Vertical Beam Dynamics Influenced by Electron Clouds at CesrTA on Variations in Bunch Spacing and Vertical Chromaticity	electron, synchrotron, emittance, feedback	1847
	R. Holtzapple, R.F. Campbell, E.L. Holtzapple CalPoly, San Luis Obispo, California, USA M.G. Billing, K.R. Butler, G. Dugan, M.J. Forster, B.K. Heltsley, G. Ramirez, N.T. Rider, J.P. Shanks, K.G. Sonnad CLASSE, Ithaca, New York, USA J.W. Flanagan KEK, Ibaraki, Japan
	Funding: Work supported by DOE Award DE-FC02-08ER41538, NSF Award PHY-0734867, PHY-1068662 and the Lepton Collider R&D Coop. Agreement: NSF Award PHY-1002467 Experiments have been performed on the Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) to probe the interaction of the electron cloud with a 2-Gev stored positron beam. The purpose of these experiments was to characterize the beam–electron cloud interactions by varying the vertical chromaticity and bunch spacing. These experiments were performed on a 30-bunch positron train, at a fixed current of 0.75mA/bunch, where the bunch spacing was varied between 4 and 28ns at three different vertical chromaticity settings. The vertical beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using the x-ray beam size monitor (xBSM) that is used to measure the bunch-by-bunch, turn-by-turn vertical beam size of the bunch trains. In this paper, we report the results from these experiments and discuss the effects of the electron cloud on the CesrTA beam dynamics.

WEOAB203	The PEPPo Concept for a Polarized Positron Source	electron, polarization, target, photon	2088
	E. J-M. Voutier LPSC, Grenoble, France
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Polarized positron beams are identified as an essential ingredient for the experimental program at the next generation of lepton accelerators (JLab, Super KEK B, ILC, CLIC). A proof-of-principle experiment for a new method to produce polarized positrons has recently been performed at the Jefferson Laboratory. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁺e⁻ pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high Z conversion target. The experiment was performed at the injector of the CEBAF accelerator at JLab and investigated the polarization transfer of an 8.3 MeV/c polarized electron beam to positrons produced in varying production target thicknesses. A dedicated new beam-line was constructed to produce, collect and transport positrons in the momentum range of 3.2 MeV/c to 6.2 MeV/c to a polarized iron target for polarization measurements. This technique potentially opens a new pathway for both high energy and thermal polarized positron beams. This presentation will discuss the PEPPo concept, the motivations for the experiment and the preliminary experimental results. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
	Slides WEOAB203 [4.102 MB]

WEPEA022	Analytical Estimations of the Dynamic Apertures of Beams with Momentum Deviation and Application in FFAG	dynamic-aperture, sextupole, simulation, lattice	2546
	M. Xiao, J. Gao IHEP, Beijing, People's Republic of China
	Analytical formulae for estimating the dynamic apertures of synchrotron particles has been well established. Based on the standard mapping, we extend the analytical formulae of dynamic aperture for off-momentum particles in circular accelerator. And we compare the analytical results with the simulation ones in the BEPC-II positron ring lattice under some conditions. What's more, we give the analytical formulae of dynamic aperture for FFAG in the similar way.

WEPEA067	Beam Optics Measurements through Turn by turn Beam Position Data in the SLS	betatron, storage-ring, optics, luminosity	2663
	P. Zisopoulos, Y. Papaphilippou CERN, Geneva, Switzerland A. Streun PSI, Villigen PSI, Switzerland V.G. Ziemann Uppsala University, Uppsala, Sweden
	Refined Fourier analysis of turn-by-turn (TBT) transverse position data measurements can be used for determining several beam properties of a ring, such as transverse tunes, optics functions, phases, chromatic properties and coupling. In particular, the Numerical Analysis of Fundamental Frequencies (NAFF) algorithm is used to analyze TBT data from the Swiss Light Source (SLS) storage ring in order to estimate on and off-momentum beam characteristics. Of particular interest is the potential of using the full position information within one turn in order to measure beam optics properties.

WEPFI019	High Power Test of Kanthal-coated L-band Lossy Cavity	cavity, vacuum, klystron, solenoid	2744
	F. Miyahara, Y. Arakida, Y. Higashi, T. Higo, K. Kakihara, S. Matsumoto KEK, Ibaraki, Japan K. Saito Hitachi, Ltd., Energy and Environmental System Laboratory, Hitachi-shi, Japan H. Sakurabata Hitachi, Ltd., Power & Industrial Systems R&D Laboratory, Ibaraki-ken, Japan
	We have been developing a Kanthal (Al-Cr-Fe)-coated collinear load as a possible candidate of the L-band acc. structure of SuperKEKB positron capture system. In order to achieve the higher capture efficiency comparing to that of KEKB, the upgrade of the e⁺ production and capture section is required. The system consists of a W target with a flux concentrator followed by acc. structures surrounded by solenoids. The increase of the e⁺ bunch charge and the reduction of satellite bunches are the main issues for this system. The frequency choice of L-band is based on the larger transverse and longitudinal acceptances than those of the S-band one. The load is preferable to compose the system with compact magnets and to minimize the dip in the solenoid field. The design of the load was reported in previous work. We understand that the Kanthal-coated cell should be confirmed in high power to confirm the feasibility at our design field of 10 MV/m level. We are making a test cavity which consists of 3 cells and one of them is composed of Kanthal-coated disks to lower the intrinsic Q value from 20000 to the order of 1000. The cavity production and the experimental result will be reported. Development of L-band accelerating structure with Kanthal-coated collinear load for SuperKEKB, IPAC12, THLR04.

WEPFI084	High Power S-band RF Window Optimized to Minimize Electric and Magnetic Field on the Surface	klystron, linac, vacuum, simulation	2893
	A.D. Yeremian, V.A. Dolgashev, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: * Work Supported by Doe Contract No. DE-AC02-76SF00515 RF windows are used to separate vacuum from atmosphere in high power microwave systems, such as klystrons. RF breakdowns in these megawatt power environments are frequent and problematic. And S-band RF window was designed to have reduced electric and magnetic field in the ceramic and waveguide joints. Specifically the normal component of the electric field on the ceramic is minimized and a traveling wave is created inside the ceramic by optimizing the shape of the window and the geometry of the joint between the circular waveguide to the rectangular waveguide. A prototype of this window in the process of being made at SLAC for high power tests.

THPFI013	Development of Cylindrical-type 1.2 MW High Power Water-load for Super KEKB	klystron, collider, cavity, factory	3318
	K. Watanabe, K. Ebihara, A. Kabe, K. Marutsuka, M. Nishiwaki KEK, Ibaraki, Japan Y. Kawane, A. Miura Nihon Koshuha Co. Ltd, Yokohama, Japan
	We have developed and manufactured CW 1.2 MW high power water-load for the use of the Super KEKB, an electron – positron double-ring collider at KEK. The tank and rf window of the water-load is the circular and cylindrical-type. The material to absorb the rf power is a tap water. This load is equipped on the 3rd port of the circulators to safe the 1.2 MW CW klystrons to drive the ARES cavities in main ring. The operational frequency is 508.9 MHz. A proto-type model of this water-load was fabricated at Sep 2012, and tested using by high power klystron (1 MW) at Oct 2012 at KEK D2-ET station. The result of high power test will be reported in this paper.

THPFI088	Electron Cloud Diagnostic Chambers with Various EC-suppression Coatings	vacuum, electron, ion, pick-up	3496
	Y. Li, J.V. Conway, X. Liu, M.A. Palmer CLASSE, Ithaca, New York, USA
	Funding: Work supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the U.S. Department of Energy DE-FC02-08ER41538 Suppression of electron cloud (EC) growth and density is critical for many high intensity accelerators of positively charged particles, such as positron rings for Super KEKB and ILC’s positron damping ring. Among various suppression techniques, passive coating with low secondary electron emission (SEY) coefficient is the most economic method. During CesrTA EC study program, we have created two dedicated short sections in the CESR vacuum system to study effectiveness of various SEY reduction coatings. During last 4 years, six one-meter-long EC study vacuum chambers were constructed, and rotated through these short sections. The EC chambers were not only equipped with EC diagnostics (including a RFA and RF-shield pickups), they were also installed in CESR with vacuum instrument, including a cold cathode ion gauge and a residual gas analyzer. With these EC study chambers, EC-suppression effectiveness of TiN, amorphous carbon and diamond-like carbon coatings were evaluated, relative to bare aluminum chamber. In this report, we will report vacuum properties of these coatings. In particular, the photon-induced desorption and beam conditioning histories are presented.

THPWA014	Development of Photon-induced Positron Annihilation Lifetime Spectroscopy using an S-band Compact Electron Linac	photon, electron, linac, laser	3660
	Y. Taira, R. Kuroda, B.E. O'Rourke, N. Oshima, R. Suzuki, M. Tanaka, H. Toyokawa AIST, Tsukuba, Ibaraki, Japan K. Watanabe Nagoya University, Nagoya, Japan T. Yanagida Kyushu Institute of Technology, Fukuoka, Japan
	Funding: This work was supported by Grants-in-Aid for Scientific Research (22360297) Positron annihilation lifetime spectroscopy (PALS) is a very sensitive tool to characterize materials and study defects at the nanometer scale. However, the application of PALS has been restricted to thin samples because of the limited range of positrons in materials. PALS for thick samples is possible by using high energy photons to create positrons inside the sample via pair production. This technique is called photon-induced positron annihilation lifetime spectroscopy (PiPALS). We have developed a novel PiPALS system using ultra-short photon pulses based on bremsstrahlung radiation to carry out in-situ measurement of structural materials under special conditions (piping for supercritical water and nuclear reactor materials). Intense, ultra-short photon pulses with energies up to 40 MeV can be generated by using an electron linear accelerator with photocathode rf gun system at AIST. In this conference, we will present the experimental result of the positron annihilation lifetime spectrum of a metal target by using ultra-short photon pulses. Y. Taira et al., Rad. Phys. and Chem., accepted for publication 2012.

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MOPFI011

Construction and First Tests of the New Injection System for the Linac II at DESY

linac, electron, gun, injection

303

C. Liebig, M. Hüning, M. Schmitz
DESY, Hamburg, Germany

For the Linac II, which supplies the accelerator chain at DESY with electrons and positrons, a new injection system is planned. It is supposed to ensure reliable operation and to avoid the beam loss of about 60% at energies up to 400 MeV and the associated activation. The function of the injector components, the entire injection system and the acceleration in the linac sections were optimized in simulations. The main components are a 6 A/100 kV triode gun, buncher and a dispersive section for energy collimation. The output energy is 5 MeV and the beam pulse length can be chosen from 5 ns to 50 ns. The new buncher structure is a hybrid of a standing wave and traveling wave structure and allows a compact design and good electron capture. One of two assembled structures has been tuned and completed a test rig in the linac tunnel. In this test system detailed analysis of its properties is in progress as well as minor corrections like alignment and improvements of reliability. The final installation is going to take place from September 2013. First experimental analysis compared to simulation results will be presented.

MOPFI017

SuperKEKB Positron Source Target Protection Scheme

target, electron, radiation, simulation

315

L. Zang, T. Kamitani
KEK, Ibaraki, Japan

The SuperKEKB requires an intense beam with a large number of positrons, which is generated by a high energy electron beam strike on a solid tungsten target. The cascade shower in the target deposits large amount of energy in the material leading to target damage. The pulsed electron beam distributed the energy non-uniformly over the target. In that case, a mechanical stress appears due to the large thermal gradient during each pulse, which could potentially destroy the target. Based on the analysis of the SLAC damaged target, peak energy deposition density (PEDD) should not exceed 35 J/g to ensure a long term of safe operation. One way of reducing PEDD is increasing the beam spot size. Hence we proposed a target protection scheme, in which a protection target is placed upstream of generation target as a spoiler. The aim is to maintain the generation target’s PEDD below 35 J/g even with a point primary electron beam. In this paper, we will introduce graphite, aluminum and copper as the protection target material candidates. And also present the PEDD and positron yield evaluation as a function of various parameters such as protection target thickness and drift space.

MOPFI018

Design Study of a New Large Aperture Flux Concentrator

target, simulation, solenoid, focusing

318

L. Zang, M. Akemoto, S. Fukuda, K. Furukawa, T. Higo, K. Kakihara, T. Kamitani, Y. Ogawa, H. Someya, T. Takatomi
KEK, Ibaraki, Japan

For high luminosity electron-positron colliders, intense positron beam production is one of the key issues. Flux Concentrator (FC) is a pulsed solenoid that can generate high magnetic field of several Tesla and is often used for focusing positrons emerged from a production target. It works as an optical matching device in a positron capture section. With this device, high capture efficiency is achieved. In this paper, we will introduce a new design of a FC for the SuperKEKB positron source. The advantages of the new design are: 1. the aperture could be doubled of the previous design, 2. the transverse components are only 1/10 of the previous design, 3. maintain the same high peak longitudinal field. The new FC modeling has been done in CST Studio and we will report the results of new FC field evaluation. In order to calculate the positron yield and capture efficiency, a tracking simulation to the end of capture section has also been carried out, which is also included in this paper.

MOPME004

Fast Luminosity Monitoring using Diamond Sensors for Super Flavour Factories

luminosity, scattering, photon, electron

473

C. Rimbault, P. Bambade
LAL, Orsay, France

Super flavour factories aim to reach very high luminosities thanks to a new concept whereby the ultra-low emittance beams collide with a large crossing angle. Fast luminosity measurements are needed as input to luminosity optimization and feedback in the presence of dynamic imperfections. The required small relative precision can be reached exploiting the very large cross section of the radiative Bhabha process at zero photon scattering angle. The instrumental technique selected to sustain the large particle fluxes is based on diamond sensors to be positioned via moveable stages immediately outside the beam pipe, at locations chosen to minimize the contamination from other particle loss mechanisms.

MOPME031

Emittance Measurement with Multi-wire Scanners for BEPC-II Linac

emittance, linac, electron, injection

541

H. Geng, W.B. Liu, W. Qiao, Q. Qin, Y.F. Sui, Y. Yue
IHEP, Beijing, People's Republic of China

During the BEPC-II linac upgrade, five wire scanners have been installed in the common transport line, which makes a fast emittance measurement possible. In this paper, we will show the primary results of BEPC-II linac emittance measurement using multi-wire scanner method. The least squares method will be used for data analysis. A comparison of the results with the ones obtained by quad scan method will also be given.

MOPWA071

A Comparison of Electron Cloud Density Measurements at CesrTA

electron, simulation, resonance, pick-up

843

J.P. Sikora, J.A. Crittenden, D.O. Duggins, Y. Li, X. Liu
CLASSE, Ithaca, New York, USA
S. De Santis
LBNL, Berkeley, California, USA

Funding: This work is supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the US Department of Energy DE-FC02-08ER41538, DE-SC0006505.
Several techniques have been employed to measure the electron cloud (EC) density in accelerators. These include Time Resolved Retarding Field Analyzers (TR-RFA) and Shielded Pickups (SPU) that measure the flux of cloud electrons onto the beam-pipe wall, as well as TE wave resonance techniques that measure the EC density in a region within the volume of the beam-pipe. We have made measurements to test the EC mitigation properties of different surface coatings and geometries, often with more than one technique used in the same test chamber. We present a comparison of bare aluminum chambers with those having a TiN coating, as well as the effect of beam conditioning. In addition, we will compare the results of the different measurement techniques used in the same chamber. These measurements were made at the Cornell Electron Storage Ring (CESR) which has been reconfigured as a test accelerator (CesrTA) having positron or electron beam energies ranging from 2 GeV to 5 GeV.

MOPWA072

MODELING FOR TIME-RESOLVED RETARDING FIELD ANALYZER MEASUREMENTS OF ELECTRON CLOUD BUILDUP AT CesrTA

electron, vacuum, dipole, pick-up

846

J.A. Crittenden, Y. Li, X. Liu, M.A. Palmer, J.P. Sikora
CLASSE, Ithaca, New York, USA

Funding: US National Science Foundation PHY-0734867, PHY-1002467, and the U.S. Department of Energy DE-FC02-08ER41538
The Cornell Electron Storage Ring Test Accelerator program includes investigations into electron cloud buildup mitigation techniques using custom vacuum chambers. Multibunch electron and positron beams of energies between 2.1 and 5.3 GeV with bunch spacings from 4 to 98 ns and bunch populations ranging from 10¹⁰ to 16·10¹⁰ provide highly differentiated sensitivity to the processes contributing to cloud buildup such as photoelectron production, cloud space-charge dynamics, and secondary electron emission. Measurements of the time dependence of cloud buildup using BPM-style shielded pickups have been shown to provide tight constraints on cloud buildup models. Recently, time-resolving retarding-field analyzers have been designed, installed and commissioned. These novel detectors combine the time-resolving feature of the shielded pickups with the fine transverse segmentation and cloud electron energy sensitivity of the time-integrating retarding-field analyzers used previously. We report on progress in modeling these measurements and quantify their sensitivity to various parameters describing the underlying physical processes contributing to cloud buildup.

MOPWA078

The Calibration of the PEPPo Polarimeter for Electrons and Positrons

electron, photon, target, polarization

861

A.H. Adeyemi
JLAB, Newport News, Virginia, USA
E. J-M. Voutier
LPSC, Grenoble, France

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The PEPPo (Polarized Electrons for Polarized Positrons) experiment at Jefferson Laboratory investigated the polarization transfer from longitudinally polarized electrons to longitudinally polarized positrons, with the aim of developing this technology for a low energy (~MeV) polarized positron source. Polarization of the positrons was measured by means of a Compton transmission polarimeter where incoming positrons transfer their polarization into circularly polarized photons that were subsequently analyzed by a thick polarized iron target. The measurement of the transmitted photon flux with respect to the orientation of the target polarization (±) or the helicity (±) of the incoming leptons provided the measurement of their polarization. Similar measurements with a known electron beam were also performed for calibration purposes. This presentation will describe the apparatus and calibrations performed at the injector at the Jefferson Laboratory to measure positron polarization in the momentum range 3.2-6.2 MeV/c, specifically to quantify the positron analyzing power from electron experimental data measured over a comparable momentum range.
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes

MOPWA079

Characterization of the Analyzing Target of the PEPPo Experiment

target, polarization, photon, electron

864

O. Dadoun
LAL, Orsay, France
E. Froidefond, E. J-M. Voutier
LPSC, Grenoble, France

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Various methods have been investigated over the past decades for the production of polarized positrons. The purpose of the PEPPo (Polarized Electrons for Polarized Positrons) experiment is to demonstrate, for the first time, the production of polarized positrons from a polarized electron beam. This two-step process involves the production of circularly polarized photons in a high Z target via the bremsstrahlung process followed, within the same target, by the conversion of polarized photons into polarized e⁺e⁻ pairs through the pair creation process. The PEPPo experiment was performed in Spring 2012 at the injector of the Jefferson Laboratory using a highly spin-polarized (~85%) 8.3 MeV/c electron beam. The positron polarization was measured by means of a Compton transmission polarimeter over the momentum range from 3.2 MeV/c to 6.2 MeV/c. This presentation will discuss the experimental set-up with a special emphasis on the analyzing magnet constituting the polarization filter of the experiment. The knowledge of the analyzing target polarization will be discussed on the basis of simulations and calibrated to experimental data
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes

TUYB101

Progress in Super B-Factories

emittance, luminosity, linac, alignment

1096

K. Akai
KEK, Ibaraki, Japan

The upgrade of B-Factories to Super B-Factories, which will search for new physics beyond the Standard Model, opens the way for new luminosity frontier. The status of Super B-Factories will be reported.

Slides TUYB101 [42.300 MB]

TUYB102

Summary of the ILC R&D and Design

electron, linac, damping, cavity

1101

B.C. Barish
CALTECH, Pasadena, California, USA

This talk should provide a summary of the main activities of ILC-GDE since 2005, and an overview of the Technical Design Report with prospects for the next steps for the future.

Slides TUYB102 [6.544 MB]

TUPEA021

Calculation of Wakefields in Plasma Filled Dielectric Capillaries Generated by a Relativistic Electron Beam

plasma, wakefield, electron, collider

1205

C. Li, W. Gai
ANL, Argonne, USA
C. Li, C.-X. Tang, H. Zha
TUB, Beijing, People's Republic of China

In this paper we give an analytical solution of TM0n mode for wakefields generated by a relativistic electron beam passing through plasma-filled capillary waveguides. The numerical solution shows that the fields of TM0n modes could not be ignored when the plasma wave length is comparable with the effective radius of the capillary tube, which means that the boundaries are not shielded completely by plasma. Numerical examples are given in several typical cases.

TUPEA045

Self-Modulation and Hosing Instability of Slac Electron and Positron Bunches in Plasmas

electron, plasma, wakefield, simulation

1235

J. Vieira, N.C. Lopes
Instituto Superior Tecnico, Lisbon, Portugal
E. Adli, S.J. Gessner, M.J. Hogan, S.Z. Li, M.D. Litos
SLAC, Menlo Park, California, USA
Y. Fang
USC, Los Angeles, California, USA
C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi
UCLA, Los Angeles, California, USA
P. Muggli
MPI, Muenchen, Germany
O. Reimann
MPI-P, München, Germany
L.O. Silva
IPFN, Lisbon, Portugal

Funding: This work has been partially supported by Humboldt Foundation.
The understanding of the self-modulation (SMI) and hosing (HI) instabilities is critical for the success of the upcoming proton driven plasma wakefield acceleration experiments at CERN*. The use of long SLAC electron and positron bunches provides the possibility of understanding experimentally the interplay between SMI and HI. In this work we perform particle-in-cell simulations with the code OSIRIS with parameters that will be available for experiments at SLAC in 2013. We show that the SMI of 20 GeV lepton bunches can grow and saturate in less than 15 cm. Up to 8 GeV energy gain/loss could be observed after a meter long plasma. The HI can also be effectively mitigated by seeding the SMI using bunches with short rise times**. We also show analytically and numerically that in the linear regime and after saturation of the SMI the HI can be suppressed by a plasma-BNS damping analogue. Several diagnostics that could be used in experiments to measure the SMI development and these effects are also explored.
*G. Xia et al., J. Plasma Phys., 1-7 (2012).
**J. Vieira et al., Phys. Plasmas 19, 063105 (2012).

TUPME002

Design Integration at the International Linear Collider

lattice, electron, damping, civil-engineering

1559

B. List, L. Hagge, J. Kreutzkamp, N.J. Walker
DESY, Hamburg, Germany

In preparation for the Technical Design Report of the International Linear Collider, a comprehensive design of the accelerator has been compiled. DESY has contributed a systematic design integration approach, which helps to achieve a complete, correct and consistent design. We use the lattice as the leading element for design integration. Geometry information including 3D visualization models are derived from the lattice, and are used to ensure that the beamlines fit and suited for access and installation. The 3D models are also used as basis for tunnel and cavern layout. As detailed designs of components become available, the lattice is adjusted and the overall models are iterated. Lists of components are derived from the lattice and are used to generate a component bill of materials, which in turn serves as basis for cost estimation and installation planning. An integrated 3D model of the entire accelerator and all the civil construction elements helps to optimize the design for example with regard to space efficiency, ease of access for installation, and life safety. Setting up design integration in an early project stage results in a better design helps to reduce costs.

TUPME003

Simulations of the ILC Positron Source at Low Energies

undulator, target, electron, polarization

1562

A. Ushakov, V.S. Kovalenko, G.A. Moortgat-Pick
University of Hamburg, Hamburg, Germany
S. Riemann, F. Staufenbiel
DESY Zeuthen, Zeuthen, Germany

Funding: This work is supported by the German Federal Ministry of Education and Research, Joint Research Project R&D Accelerator "Spin Optimization", contract number 19XL7Ic4
The International Linear Collider (ILC) baseline design includes an undulator-based positron source. The accelerated electron beam will be used for the positron generation before it goes to the collision point. For the whole ILC energy range the source has to generate 1.5 positrons per electron. However, the efficiency of positron production goes down with decreasing electron drive beam energy. This effect can be compensated to some extend by the choice of undulator parameters and an optimized capture section. The simulation study considers for the range of electron beam energies down to low values of 120 GeV the feasibility to achieve the required positron yield. In particular, the optimum parameters for undulator and capture section are presented depending on the drive electron beam energy.

TUPME004

Spin Tracking at the International Linear Collider

resonance, dipole, polarization, damping

1565

V.S. Kovalenko, G.A. Moortgat-Pick, A. Ushakov
University of Hamburg, Hamburg, Germany
S. Riemann
DESY Zeuthen, Zeuthen, Germany
M. Vogt
DESY, Hamburg, Germany
A. Wolski
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work is supported by the German Federal Ministry of Education and Research, Joint Research Project R&D Accelerator "Spin Optimization", contract number 19XL7Ic4
In the baseline design for the International Linear collider an helical undulator-based positron source has been chosen that can provide positrons with a polarization of 60% as an upgrade option motivated by physics reasons. But even the baseline configuration would already provide about 30%. In order to match the high precision requirements from physics and to optimize the physics outcome one has to control systematic uncertainties to a very high level. Therefore it is needed to run both beams polarized but provide also an unpolarized set-up for control reasons. In our study we present results on precise spin tracking and propose also an minimal machine set-up to run in an unpolarized mode within the baseline design.

TUPME006

Simulation of Stress in Positron Targets for Future Linear Colliders

target, photon, undulator, electron

1571

F. Staufenbiel, S. Riemann
DESY Zeuthen, Zeuthen, Germany
O.S. Adeyemi, V.S. Kovalenko, G.A. Moortgat-Pick, A. Ushakov
University of Hamburg, Hamburg, Germany

Future linear collider projects require intense positron sources with yields of about 10¹⁴ positrons per second. The positron source for the ILC is based on a helical undulator passed by the accelerated electron beam to create an intense circularly polarized photon beam. The positron beam produced by these photons is longitudinally polarized. The intense photon beam causes rapid temperature increase in the target material resulting in periodic stress. The average and peak thermal and mechanical load are simulated. Implications due to long-term target irradiation are considered.

TUPME008

Beam Dynamics Studies for the Injection System of a High Luminosity Flavour Factory

linac, injection, electron, luminosity

1577

D. Pellegrini
CERN, Geneva, Switzerland
M.E. Biagini, S. Guiducci
INFN/LNF, Frascati (Roma), Italy

The requirements, in terms of average luminosity and lifetimes, of high luminosity e⁺e⁻ colliders such as the Flavor factories, pose stringent constraints to the design of the injection complex. For the SuperB B-factory project at Tor Vergata, Italy, a design was developed to deliver full energy bunches (4.2 GeV e^- and 6.7 GeV e+) to the main rings every 30 ms aiming at a high and nearly constant luminosity. The system included a polarized electron gun, a positron production system, linac sections, a Damping Ring (DR) and transfer lines connecting to the collider Main Rings (MR). After the decision, due to budget issues, to rescale the project to a lower energy (2.3 GeV/beam) for a tau/charm flavour factory, the same design principles have been applied. In this paper beam dynamics studies from the DR to the MR entrance is presented, including optimization of the transfer lines and of the bunch compressor. A start to end simulation shows that the beam quality satisfies theinjection requirements, even in the presence of energy errors and collective effects like CSR and wakefields.

TUPME010

High-intensity and Low-emittance Upgrade of 7-GeV Injector Linac towards SuperKEKB

emittance, linac, electron, laser

1583

K. Furukawa, M. Akemoto, D.A. Arakawa, Y. Arakida, A. Enomoto, S. Fukuda, H. Honma, R. Ichimiya, N. Iida, M. Ikeda, E. Kadokura, K. Kakihara, T. Kamitani, H. Katagiri, M. Kurashina, S. Matsumoto, T. Matsumoto, H. Matsushita, S. Michizono, K. Mikawa, T. Miura, F. Miyahara, T. Mori, H. Nakajima, K. Nakao, T. Natsui, Y. Ogawa, S. Ohsawa, F. Qiu, M. Satoh, T. Shidara, A. Shirakawa, H. Sugimoto, T. Suwada, T. Takatomi, T. Takenaka, M. Tanaka, Y. Yano, K. Yokoyama, M. Yoshida, L. Zang, X. Zhou
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan

After a decade of successful operation at KEKB a new electron/positron collider, SuperKEKB, is being constructed to commission within FY2014. It aims at a luminosity of 8 x 10³⁵ /s.cm², 40-times higher than that of KEKB, in order to study the flavor physics of elementary particles further, by mainly squeezing the beams at the collision point. The injector linac should provide high-intensity and low-emittance beams of 7-GeV electron and 4-GeV positron by newly installing a RF-gun, a flux concentrator, and a damping ring with careful emittance and energy management. It also have to perform simultaneous top-up injections into four storage rings by pulse-to-pulse beam modulations not to interfare between three facilities of SuperKEKB, Photon Factory and PF-AR. This paper describes the injector design decisions and present status of the construction.

TUPME015

Proposal of Polarized Gamma-ray Source for ILC Based on CSR Inverse Compton Scattering

electron, cavity, scattering, laser

1598

M. Shimada, K. Yokoya
KEK, Ibaraki, Japan
R. Hajima
JAEA, Ibaraki-ken, Japan
M. Tecimer
University of Hawaii at Manoa, Honolulu, USA

The positron source of International Linear Collider (ILC) requires a circular polarized gamma-ray with a flux more than 10¹⁶ phs./s and a helical undulator-based gamma-ray source is proposed in the baseline design. Although the undulator scheme is technically feasible, it is not easy for a stand-alone operation because of the required electron energy, ~ 150GeV. In this paper, we propose an alternative method, the inverse Compton scattering with a high-power mid-infrared optical pulse generated from coherent synchrotron radiation (CSR). To achieve the high flux gamma-ray, CSR with a few MHz is stacked in a high-finesse optical cavity made of a photonic crystal. In the proposed scheme, a stand-alone operation is feasible because the electron energy is less than 10GeV.

TUPME028

RF Orbit Separation for CPT-Test Experiment at VEPP-4M

electron, betatron, closed-orbit, beam-beam-effects

1634

V.E. Blinov, E.A. Bekhtenev, G.V. Karpov, V.A. Kiselev, S.A. Krutikhin, G.Y. Kurkin, E.B. Levichev, O.I. Meshkov, S.I. Mishnev, V.V. Neyfeld, S.A. Nikitin, I.B. Nikolaev, D.N. Shatilov, G.M. Tumaikin
BINP SB RAS, Novosibirsk, Russia
A.P. Chabanov, O.P. Gordeev, A.I. Mickailov
Budker INP & NSU, Novosibirsk, Russia

Funding: This work was supported by the Ministry of Education and Science of the Russian federation and the Russian Foundation for Basis Research (grant 11-02-01422-a)
In a special program of experiments which is under development in a background regime at the VEPP-4M storage ring we set an aim to realize a potential possibility to make the CPT invariance test with the accuracy better than 10^-8. The test will be based on a precise comparison of the spin precession frequencies of simultaneously stored electrons and positrons. To exclude the presence of static electric fields increasing a systematic error we have developed and tested a special RF system driven at the half revolution frequency to subsitute for the electrostatic orbit separation system. The latter is needed for the electron and positron orbit separation at the parasitic interaction point where the beam-beam effects drastically cut the beam currents.

TUPME029

VEPP-4: Application Beyond the High Energy Physics

electron, collider, radiation, target

1637

O.I. Meshkov
BINP SB RAS, Novosibirsk, Russia

The current status of VEPP-4M electron-positron collider has been described. During fall of 2011 the accelerator was shut down for planned reconstruction of KEDR detector. The next long run of the collider will be dedicated to the experiments at high energy physics within area of 2-5 GeV. Nevertheless, the set of experiments at booster VEPP-3 were continued. VEPP-3 was operated as an SR source, the experiment with internal target was performed and electron/positron scattering at proton was studied. The short runs of VEPP-4M were used as for commissioning of the new “warm” 3T wiggler as for experiments with an extracted electron beam dedicated for testing of different high energy physics detectors. The experiment of comparing of anomalous magnetic moment of electron and positron is con-tinued at VEPP-4M. The system of RF beam shifting is installed at a straight section of the accelerator. It is applied for elimination of parasitic interaction points of electron and positron beams. The first experiments with this system are described. KEDR detector reconstruction should be finished at autumn of 2013. The future experiments with KEDR detector are discussed.

TUPME056

3.5 GeV Superconducting Stacking Ring for Compton Based Polarized Positrons Source of CLIC

injection, damping, synchrotron, emittance

1697

E.V. Bulyak, P. Gladkikh, A.A. Kalamayko
NSC/KIPT, Kharkov, Ukraine
T. Omori, J. Urakawa, K. Yokoya
KEK, Ibaraki, Japan
L. Rinolfi, F. Zimmermann
CERN, Geneva, Switzerland

This paper describes 3.5 GeV superconducting storage ring dedicated to positron accumulation as part of a polarized positron source for CLIC, based on Compton scattering in a Compton storage ring. The superconducting stacking ring can provide a synchrotron damping time of order 250 microseconds. Together with combined injection scheme in the longitudinal and transverse plane, such a ring may solve the problem of accumulating a positron beam with efficiency close to 95 % and with the beam intensity required for CLIC.

TUPWA061

Observation at CesrTA of the Reduction of the Vertical Beam Size of the Lead Bunch in a Train Due to the Presence of a Precursor Bunch

electron, dipole, feedback, simulation

1841

M.G. Billing, K.R. Butler, G. Dugan, M.J. Forster, R.E. Meller, G. Ramirez, N.T. Rider, K.G. Sonnad, H.A. Williams
CLASSE, Ithaca, New York, USA
J.W. Flanagan
KEK, Ibaraki, Japan
R. Holtzapple, M. Randazzo
CalPoly, San Luis Obispo, California, USA
M.A. Palmer
Fermilab, Batavia, USA

Funding: Work supported by DOE Award DE-FC02-08ER41538, NSF Award PHY-0734867, PHY-1068662 and the Lepton Collider R&D Coop Agreement: NSF Award PHY-1002467.
Electron cloud-induced beam dynamics is being studied at CesrTA under various conditions. These measurements make use of instrumentation for the detection of the coherent self-excited spectrum for each bunch within the train and bunch-by-bunch vertical beam size. In the position spectrum coherent betatron dipole and head-tail motion is detectable for each individual bunch within the train. These techniques are utilized to study the electron cloud-related interactions, which cause the growth of coherent motion and beam size along the train. We report on the observations of the vertical enlargement of the first bunch(es) in 30 bunch-long trains. We also report that the addition of a precursor bunch following the train of bunches and before the start of the next train can counteract the vertical enlargement of the first bunch(es) in the train. Results from these observations will be presented.

TUPWA062

Dependence of Beam Instabilities Caused by Electron Clouds at CesrTA on Variations in Bunch Spacing and Chromaticity

electron, damping, dipole, resonance

1844

M.G. Billing, K.R. Butler, G. Dugan, M.J. Forster, R.E. Meller, M.A. Palmer, G. Ramirez, N.T. Rider, K.G. Sonnad, H.A. Williams
CLASSE, Ithaca, New York, USA
R.F. Campbell, R. Holtzapple, M. Randazzo
CalPoly, San Luis Obispo, California, USA
J.W. Flanagan
KEK, Ibaraki, Japan

Funding: Work supported by DOE Award DE-FC02-08ER41538, NSF Award PHY-0734867 and the Lepton Collider R&D Coop Agreement: NSF Award PHY-1002467
Experiments have been performed at the Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) to probe the interaction of the electron cloud with a 2.1 Gev stored positron beam. The purpose of these experiments was to characterize the dependence of beam–electron cloud interactions on the bunch spacing and the vertical chromaticity. These experiments were performed on a 30-bunch positron train, at a fixed current of 0.75mA/bunch. The bunch spacing was varied between 4 and 28 ns at three different vertical chromaticity settings. The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 1) a gated Beam Position Monitor (BPM) and spectrum analyzer to measure the bunch-by-bunch frequency spectrum of the bunch trains; 2) an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the observations from these experiments and analyze the effects of the electron cloud on the stability of bunches within these different trains.

TUPWA063

Dependence of Vertical Beam Dynamics Influenced by Electron Clouds at CesrTA on Variations in Bunch Spacing and Vertical Chromaticity

electron, synchrotron, emittance, feedback

1847

R. Holtzapple, R.F. Campbell, E.L. Holtzapple
CalPoly, San Luis Obispo, California, USA
M.G. Billing, K.R. Butler, G. Dugan, M.J. Forster, B.K. Heltsley, G. Ramirez, N.T. Rider, J.P. Shanks, K.G. Sonnad
CLASSE, Ithaca, New York, USA
J.W. Flanagan
KEK, Ibaraki, Japan

Funding: Work supported by DOE Award DE-FC02-08ER41538, NSF Award PHY-0734867, PHY-1068662 and the Lepton Collider R&D Coop. Agreement: NSF Award PHY-1002467
Experiments have been performed on the Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) to probe the interaction of the electron cloud with a 2-Gev stored positron beam. The purpose of these experiments was to characterize the beam–electron cloud interactions by varying the vertical chromaticity and bunch spacing. These experiments were performed on a 30-bunch positron train, at a fixed current of 0.75mA/bunch, where the bunch spacing was varied between 4 and 28ns at three different vertical chromaticity settings. The vertical beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using the x-ray beam size monitor (xBSM) that is used to measure the bunch-by-bunch, turn-by-turn vertical beam size of the bunch trains. In this paper, we report the results from these experiments and discuss the effects of the electron cloud on the CesrTA beam dynamics.

WEOAB203

The PEPPo Concept for a Polarized Positron Source

electron, polarization, target, photon

2088

E. J-M. Voutier
LPSC, Grenoble, France

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Polarized positron beams are identified as an essential ingredient for the experimental program at the next generation of lepton accelerators (JLab, Super KEK B, ILC, CLIC). A proof-of-principle experiment for a new method to produce polarized positrons has recently been performed at the Jefferson Laboratory. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁺e⁻ pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high Z conversion target. The experiment was performed at the injector of the CEBAF accelerator at JLab and investigated the polarization transfer of an 8.3 MeV/c polarized electron beam to positrons produced in varying production target thicknesses. A dedicated new beam-line was constructed to produce, collect and transport positrons in the momentum range of 3.2 MeV/c to 6.2 MeV/c to a polarized iron target for polarization measurements. This technique potentially opens a new pathway for both high energy and thermal polarized positron beams. This presentation will discuss the PEPPo concept, the motivations for the experiment and the preliminary experimental results.
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.

Slides WEOAB203 [4.102 MB]

WEPEA022

Analytical Estimations of the Dynamic Apertures of Beams with Momentum Deviation and Application in FFAG

dynamic-aperture, sextupole, simulation, lattice

2546

M. Xiao, J. Gao
IHEP, Beijing, People's Republic of China

Analytical formulae for estimating the dynamic apertures of synchrotron particles has been well established. Based on the standard mapping, we extend the analytical formulae of dynamic aperture for off-momentum particles in circular accelerator. And we compare the analytical results with the simulation ones in the BEPC-II positron ring lattice under some conditions. What's more, we give the analytical formulae of dynamic aperture for FFAG in the similar way.

WEPEA067

Beam Optics Measurements through Turn by turn Beam Position Data in the SLS

betatron, storage-ring, optics, luminosity

2663

P. Zisopoulos, Y. Papaphilippou
CERN, Geneva, Switzerland
A. Streun
PSI, Villigen PSI, Switzerland
V.G. Ziemann
Uppsala University, Uppsala, Sweden

Refined Fourier analysis of turn-by-turn (TBT) transverse position data measurements can be used for determining several beam properties of a ring, such as transverse tunes, optics functions, phases, chromatic properties and coupling. In particular, the Numerical Analysis of Fundamental Frequencies (NAFF) algorithm is used to analyze TBT data from the Swiss Light Source (SLS) storage ring in order to estimate on and off-momentum beam characteristics. Of particular interest is the potential of using the full position information within one turn in order to measure beam optics properties.

WEPFI019

High Power Test of Kanthal-coated L-band Lossy Cavity

cavity, vacuum, klystron, solenoid

2744

F. Miyahara, Y. Arakida, Y. Higashi, T. Higo, K. Kakihara, S. Matsumoto
KEK, Ibaraki, Japan
K. Saito
Hitachi, Ltd., Energy and Environmental System Laboratory, Hitachi-shi, Japan
H. Sakurabata
Hitachi, Ltd., Power & Industrial Systems R&D Laboratory, Ibaraki-ken, Japan

We have been developing a Kanthal (Al-Cr-Fe)-coated collinear load as a possible candidate of the L-band acc. structure of SuperKEKB positron capture system. In order to achieve the higher capture efficiency comparing to that of KEKB, the upgrade of the e⁺ production and capture section is required. The system consists of a W target with a flux concentrator followed by acc. structures surrounded by solenoids. The increase of the e⁺ bunch charge and the reduction of satellite bunches are the main issues for this system. The frequency choice of L-band is based on the larger transverse and longitudinal acceptances than those of the S-band one. The load is preferable to compose the system with compact magnets and to minimize the dip in the solenoid field. The design of the load was reported in previous work*. We understand that the Kanthal-coated cell should be confirmed in high power to confirm the feasibility at our design field of 10 MV/m level. We are making a test cavity which consists of 3 cells and one of them is composed of Kanthal-coated disks to lower the intrinsic Q value from 20000 to the order of 1000. The cavity production and the experimental result will be reported.
*Development of L-band accelerating structure with Kanthal-coated collinear load for SuperKEKB, IPAC12, THLR04.

WEPFI084

High Power S-band RF Window Optimized to Minimize Electric and Magnetic Field on the Surface

klystron, linac, vacuum, simulation

2893

A.D. Yeremian, V.A. Dolgashev, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: * Work Supported by Doe Contract No. DE-AC02-76SF00515
RF windows are used to separate vacuum from atmosphere in high power microwave systems, such as klystrons. RF breakdowns in these megawatt power environments are frequent and problematic. And S-band RF window was designed to have reduced electric and magnetic field in the ceramic and waveguide joints. Specifically the normal component of the electric field on the ceramic is minimized and a traveling wave is created inside the ceramic by optimizing the shape of the window and the geometry of the joint between the circular waveguide to the rectangular waveguide. A prototype of this window in the process of being made at SLAC for high power tests.

THPFI013

Development of Cylindrical-type 1.2 MW High Power Water-load for Super KEKB

klystron, collider, cavity, factory

3318

K. Watanabe, K. Ebihara, A. Kabe, K. Marutsuka, M. Nishiwaki
KEK, Ibaraki, Japan
Y. Kawane, A. Miura
Nihon Koshuha Co. Ltd, Yokohama, Japan

We have developed and manufactured CW 1.2 MW high power water-load for the use of the Super KEKB, an electron – positron double-ring collider at KEK. The tank and rf window of the water-load is the circular and cylindrical-type. The material to absorb the rf power is a tap water. This load is equipped on the 3rd port of the circulators to safe the 1.2 MW CW klystrons to drive the ARES cavities in main ring. The operational frequency is 508.9 MHz. A proto-type model of this water-load was fabricated at Sep 2012, and tested using by high power klystron (1 MW) at Oct 2012 at KEK D2-ET station. The result of high power test will be reported in this paper.

THPFI088

Electron Cloud Diagnostic Chambers with Various EC-suppression Coatings

vacuum, electron, ion, pick-up

3496

Y. Li, J.V. Conway, X. Liu, M.A. Palmer
CLASSE, Ithaca, New York, USA

Funding: Work supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the U.S. Department of Energy DE-FC02-08ER41538
Suppression of electron cloud (EC) growth and density is critical for many high intensity accelerators of positively charged particles, such as positron rings for Super KEKB and ILC’s positron damping ring. Among various suppression techniques, passive coating with low secondary electron emission (SEY) coefficient is the most economic method. During CesrTA EC study program, we have created two dedicated short sections in the CESR vacuum system to study effectiveness of various SEY reduction coatings. During last 4 years, six one-meter-long EC study vacuum chambers were constructed, and rotated through these short sections. The EC chambers were not only equipped with EC diagnostics (including a RFA and RF-shield pickups), they were also installed in CESR with vacuum instrument, including a cold cathode ion gauge and a residual gas analyzer. With these EC study chambers, EC-suppression effectiveness of TiN, amorphous carbon and diamond-like carbon coatings were evaluated, relative to bare aluminum chamber. In this report, we will report vacuum properties of these coatings. In particular, the photon-induced desorption and beam conditioning histories are presented.

THPWA014

Development of Photon-induced Positron Annihilation Lifetime Spectroscopy using an S-band Compact Electron Linac

photon, electron, linac, laser

3660

Y. Taira, R. Kuroda, B.E. O'Rourke, N. Oshima, R. Suzuki, M. Tanaka, H. Toyokawa
AIST, Tsukuba, Ibaraki, Japan
K. Watanabe
Nagoya University, Nagoya, Japan
T. Yanagida
Kyushu Institute of Technology, Fukuoka, Japan

Funding: This work was supported by Grants-in-Aid for Scientific Research (22360297)
Positron annihilation lifetime spectroscopy (PALS) is a very sensitive tool to characterize materials and study defects at the nanometer scale. However, the application of PALS has been restricted to thin samples because of the limited range of positrons in materials. PALS for thick samples is possible by using high energy photons to create positrons inside the sample via pair production. This technique is called photon-induced positron annihilation lifetime spectroscopy (PiPALS). We have developed a novel PiPALS system using ultra-short photon pulses based on bremsstrahlung radiation to carry out in-situ measurement of structural materials under special conditions (piping for supercritical water and nuclear reactor materials). Intense, ultra-short photon pulses with energies up to 40 MeV can be generated by using an electron linear accelerator with photocathode rf gun system at AIST. In this conference, we will present the experimental result of the positron annihilation lifetime spectrum of a metal target by using ultra-short photon pulses*.
*Y. Taira et al., Rad. Phys. and Chem., accepted for publication 2012.