RLNR, Tokyo
AIST, Tsukuba, Ibaraki
WERC, Tsuruga , Fukui
Positron that is the antiparticle of the electron, by the specific character, can evaluate vacant spaces in microstructure from atomic level to nanometer level, which is difficult in other measurement methods. In the case of high functional material, this structure often relates directly to the performance, and the evaluation method that uses the positron beam is expected as a useful measurement tool to develop a new material. If it is able to produce more high-intense and low-energy positron beam with an accelerator, the microstructure evaluation is carried out in prompt and high accuracy for various demands of the material analysis. We have studied a positron production system using a superconducting electron linac instead of normal conducting one. Electron beam accelerated with the superconducting linac is irradiated on tantalum and converted to bremstrahlung photons, and positron beam is produced by pair creation of them. The designed acceleration energy of the superconducting electron linac is 15-40 MeV and the maximum beam power is 10 kW. The system configuration and the progress status will be presented.
Muons, Inc, Batavia
Fermilab, Batavia
We study electron-positron in-flight annihilation as a potential source of quasi-monoenergetic photon (or gamma-ray) beams. A high-intensity tunable-energy (1.5 MeV to 15 MeV) gamma source has many potential uses in medical, industrial and security applications. Several electron-positron collision geometries are considered: a) head-on; b) collinear; and c) positron beam incident on a fixed electron target. We analyze advantages of each of the geometries in order to optimize parameters of the generated gamma-ray beams.
Muons, Inc, Batavia
Positrons produced by electrons impinging on a target cover a broad momentum range. By bending the positrons 180° in a dipole magnetic field the momenta are dispersed according to their momenta along the exit plane of the magnet. A wedge-shaped absorber placed at the exit plane can reduce the momenta accordingly to produce a quasi-monochromatic beam of positrons. Simulation results are presented for 2 to 10 MeV/c quasi-mono-chromatic positrons produced by 75 MeV electrons on a tungsten target.
Muons, Inc, Batavia
Fermilab, Batavia
A compact tunable gamma ray source has many potential uses in medical and industrial applications. One novel scheme to produce an intense beam of gammas relies on the ability to create a high flux of positrons. We present various positron production methods that are compatible with this approach for producing the intense beam of gammas.
Università di Brescia, Brescia
I.N.F.N., Pavia
CERN, Geneva
The AEGIS experiment is expected to be installed at the CERN Antiproton Decelerator in a very close future, since the main goal of the AEGIS experiment is the measurement of gravity impact on antihydrogen, which will be produced on the purpose. Antihydrogen production implies very challenging environmental conditions: at the heart of the AEGIS facility 50 mK temperature, 10-12 mbar pressure and a 1 T magnetic field are required. Interfacing extreme cryogenics with ultra high vacuum will affect very strongly the design of the whole facility, requiring a very careful mechanical design. This paper presents an overview of the actual design of the AEGIS experimental facility, paying special care to mechanical aspects. Each subsystem of the facility - ranging from the positron source to the recombination region and the measurement region - will be shortly described. The ultra cold region, which is the most critical with respect to the antihydrogen formation, will be dealt in detail. The assembly procedures will be considered too, as they are expected to be critical to make the set-up phase easier, as well as to make possible any future improvement of the facility itself.
INFN/LNF, Frascati (Roma)
Università degli Studi di Firenze, Firenze
INOA, Firenze
VIGO System S.A., Ozarow Maz.
At the LNF of INFN an IR array detector with a ns response time has been built and assembled in order to collect the IR image of the e-/e+ sources at DAΦNE. Such detector is made by 32 bilinear pixels with a pixel size of 50x50 μm2 and a response time of 1 ns. The device with its electronic board has been assembled for the installation on the e+ ring of DAΦNE in the framework of an experiment funded by the INFN Vth Committee dedicated to beam diagnostics. A preliminary characterization of few pixels of the array and of the electronics has been carried out at the IR beamline SINBAD at DAΦNE. In particular the detection of the IR source of the e- beam has been observed using four pixels of the array acquiring signals simultaneously with a 4 channels scope at 1GHz and at 4 Gsamples/s. The acquisition of 4 pixels allowed monitoring in real time differences in the bunch signals in the vertical direction. Preliminary analysis of data is presented and discussed. In particular we will outline how the differences in the signals can be correlated to small displacements of the source after the bunch refilling and during a complete shift of DAΦNE and before the refilling of electrons.
JAI, Egham, Surrey
DESY, Hamburg
The PETRA-III Laser-wire, a Compton scattering beam size measurement system at DESY, uses an automated mirror to scan a Q-switched laser across the electron beam and is developed from the system previously operated at PETRA-II. This paper reports on recent upgrades of the optics, vacuum vessel and data acquisition. First beam profile measurements are also presented.
JAI, Oxford
We present the design of a stripline beam position monitor (BPM) signal processor with low latency (c. 10ns) and micron-level spatial resolution in single-pass mode. Such a BPM processor has applications in single-pass beamlines such as those at linear colliders and FELs. The processor was deployed and tested at the Accelerator Test Facility (ATF2) extraction line at KEK, Japan. We report the beam test results and processor performance, including response, linearity, spatial resolution and latency.
OXFORDphysics, Oxford, Oxon
INFN MIB, MILANO
The international Muon Ionization Cooling Experiment (MICE) will carry out a systematic investigations of ionization cooling of a muon beam. As the emittance measurement will be done on a particle-by-particle basis, a sophisticated beam instrumentation is needed to measure particle coordinates and timing vs RF. A PID system based on three time-of-flight detectors, two Aerogel Cerenkov counters and a KLOE-like calorimeter has been constructed in order to keep beam contamination (e, π) well below 1 %. The MICE TOF system will measure timing with a resolution better than 60 ps per plane, in a harsh environment due to high particle rates, fringe magnetic fields and RF backgrounds. Performances in beam of all detectors will be shown, as also future upgrades.
LBNL, Berkeley, California
CLASSE, Ithaca, New York
Grove City College, Grove City, Pennsylvania
The CESR Damping Ring Test Accelerator collaboration (Cesr-TA) utilizes the CESR e+/e- storage ring at Cornell University for carrying out R&D activities critical for the ILC damping rings. In particular, various locations have been instrumented for the study of the electron cloud effects and their amelioration. In this paper we present the results obtained using the TE wave propagation method to study the electron cloud evolution and its dependence on several beam and machine parameters. Whenever possible, we have also compared our measurements with those obtained by using retarding field analyzers (RFA) with good agreement. Amongst the results obtained, we were able to detect a strong resonance of the electron cloud with the TE wave in regions of the beampipe where a dipole-like magnetic field is also present. Besides the standard transmission method, we are also developing an alternative procedure, the so-called resonant BPM, which can be used for a more localized measurement of the electron cloud density, which has already yielded promising results.
CLASSE, Ithaca, New York
CalPoly, San Luis Obispo, CA
The beam position monitor (BPM) system at the Cornell Electron Storage Ring (CESR) has been upgraded for use in both CESR Test Accelerator (CesrTA) and Cornell High Energy Synchrotron Source (CHESS) operations. CesrTA operates with electron and positron bunch trains with as little as 4ns bunch spacing. CHESS operates with simultaneous counter-rotating electron and positron trains with 14ns bunch spacing. The upgraded BPM system provides high resolution measurement capability as is needed for the CesrTA ultra low emittance operations, turn-by-turn digitization of multiple bunches for beam dynamics studies, and the capability for real-time dual beam monitoring in CHESS conditions. In addition to standard position measurement capability, the system is also required to measure betatron phase by synchronous detection of a driven beam for optics diagnosis and correction. This paper describes the characteristics of the BPM hardware upgrade, performance figures of the electronics designed for this purpose and the overall status of the upgrade effort. Examples of key measurement types and the analysis of data acquired from the new instruments will also be presented.
CLASSE, Ithaca, New York
KEK, Ibaraki
We report on the design and operation of the CesrTA x-ray beam size monitor (xBSM). The xBSM resolution must be sufficient to measure vertical beam sizes of order 10um by imaging 2-4keV synchrotron radiation photons onto a one-dimensional photodiode array. Instrumentation in the evacuated x-ray beam line includes upstream interchangeable optics elements (slits, coded apertures, and Fresnel zone plates), a monochromator and an InGaAs photodiode detector. The readout is a beam-synchronized FADC that is capable of parallel measurement of consecutive bunches with 4ns spacing. The xBSM has been used to measure beam sizes during the August 2009, November 2009, and April 2010 runs. Single turn measurements are fit to characteristic image shapes to extract beam sizes independent of position variations. The turn-averaged beam size provides feedback for low-emittance tuning.
CLASSE, Ithaca, New York
CalPoly, San Luis Obispo, CA
During the last several years CESR has been studying the effects of electron clouds on stored beams in order to understand their impact on future linear-collider damping ring designs. One of the important issues is the way that the electron cloud alters the dynamics of bunches within the train. Techniques for observing the dynamical effects of beams interacting with the electron clouds have been developed. These methods will be discussed and examples of measurements will be presented.
CLASSE, Ithaca, New York
CERN, Geneva
Carleton University, College of Natural Sciences, Ottawa, Ontario
Purdue University, West Lafayette, Indiana
LBNL, Berkeley, California
Grove City College, Grove City, Pennsylvania
INFN/LNF, Frascati (Roma)
ASCo, Clayton, Victoria
KEK, Ibaraki
Clarkson University, Potsdam, New York
BNL, Upton, Long Island, New York
ANL, Argonne
CalPoly, San Luis Obispo, CA
Cockcroft Institute, Warrington, Cheshire
SLAC, Menlo Park, California
Fermilab, Batavia
Technion, Haifa
Loyola University, Chicago, Illinois
The Cornell Electron Storage Ring (CESR) has been reconfigured as a test accelerator (CesrTA) for a program of electron cloud (EC) research at ultra low emittance. The instrumentation in the ring has been upgraded with local diagnostics for measurement of cloud density and with improved beam diagnostics for the characterization of both the low emittance performance and the beam dynamics of high intensity bunch trains interacting with the cloud. Finally a range of EC mitigation methods have been deployed and tested. Measurements of cloud density and its impact on the beam under a range of conditions will be presented and compared with simulations. The effectiveness of a range of mitigation techniques will also be discussed.
INFN/LNF, Frascati (Roma)
CERN, Geneva
BINP SB RAS, Novosibirsk
Recently the peak luminosity achieved on the DAΦNE collider has been improved by almost a factor 3 by implementing a novel collision scheme based on large Piwinski angle and Crab-Waist. This encouraging result opened new perspectives for physics research and a new run with the KLOE-2 detector has been scheduled to start by spring 2010. The KLOE-2 installation is a complex operation requiring a careful design effort and a several months long shutdown. The high luminosity interaction region has been deeply revised in order to take into account the effect on the beam caused by the solenoidal field of the experimental detector and to ensure background rejection. The shutdown has been also used to implement several other modifications aimed at improving beam dynamics: the wiggler poles have been displaced from the magnet axis in order to cancel high order terms in the field, the feedback systems have been equipped with stronger power supplies and more efficient kickers and electrodes have been inserted inside the wiggler and the dipole vacuum chambers, in the positron ring, to avoid the e-cloud formation. A low level RF feedback has been added to the cavity control in both rings.
KEK, Ibaraki
Optics parameters at the interaction point, beta, x-y coupling, dispersion and their chromatic aberrations, seriously affect the beam-beam performance as is shown in experiments and simulations. The control of the optics parameters is essential to maintain the high luminosity in KEKB. They drift day by day, or before and after the beam abort. They were often monitored at intervals of the operation with taking the study time. They are recently measured during the physics run using a pilot bunch without collision. We show the measured the optics parameters and their variations and discuss the relation to the luminosity.
KEK, Ibaraki
Single bunch instability caused by electron cloud can depend on emittance, because the electron oscillation period in positron bunch is large. The single bunch instability should appear as a head-tail motion with synchro-beta frequency. We discuss the single bunch instability in low emittance rings, CesrTA, Super B factories and ILC damping ring with focusing the threshold and synchro-beta oscillation.
SLAC, Menlo Park, California
We study the bunch field diffusion and energy dissipation in the beam pipe of the Super-B detector, which consists of two coaxial Be thin pipes (half a millimeter). Cooling water will run between these two pipes. Gold and nickel will be sputtered (several microns) onto the beryllium pipe. The Maxwell equations for the beam fields in these thin layers are solved numerically for the case of infinite pipes. We also calculate the amplitude of electromagnetic fields outside the beam pipe, which may be noticeable as the beam current can reach 4 A in each beam. Results of simulations are used for the design of this central part of the Super-B detector.
SLAC, Menlo Park, California
We discuss the feasibility of an application of an implicit finite-difference approximation to calculate the fields of a bunch moving with no restriction inside the vacuum chamber.
KEK, Ibaraki
Super-KEKB, an upgrade plan of the present KEKB collider, has recently changed its scheme from 'high current' option to 'nano-beam' scheme. In the latter the current is relatively low(4A/2.3A for LER/HER ring) compared to that of the high-current option(9.4A/4.1A), while the vertical beam size is squeezed to 60 nm at the interaction point to get the high luminosity. The emittance of the injected beam should be low and, since the Tousheck lifetime is very short(600 sec), the intensity of the positron beam is as high as 8 nC/pulse. For the electron beam a low-emittance high-intensity RF gun is adopted. For the positron beam a damping ring has been proposed. The design of the damping ring has been performed for the high-current option*. In this paper an updated design for the nano-beam scheme is presented.
* Nucl. Instr. Meth. A 556 (2006) 13-19
LAL, Orsay
INFN/LNF, Frascati (Roma)
IN2P3 IPNL, Villeurbanne
Providing a high quality and sufficient high current positron beam for the ultra high luminosity B-factory SuperB is a major goal. In this paper a proposition for positrons production and capture scheme based on low energy electrons up to1 GeV is presented. For this technique, several types of flux concentrator used to capture the positrons are being studied. The following accelerating section bringing the positrons up to 280 MeV and the total yield for L-band and S-band type accelerators are given. Also the result of the benchmark between ASTRA and a LAL code based on Geant4 toolkit simulation is discussed.
Sokendai, Ibaraki
KEK, Ibaraki
Electron Cloud (ECLOUD) deteriorates the performance of proton and positron storage rings. Therefore it is desirable to understand the ECLOUD buildup in a given machine. The data taken by Retarded Field Analyzer (RFA) with a multi channel plate showed that the signal had the peaks coinciding with the positron bunch pattern if a high voltage of -2kV is applied to the retarded grid*. This suggests that the cloud electrons get maximum kick near the positron bunch. A computer program has been developed to study the near bunch ECLOUD density at KEKB LER (Low Energy Ring). In simulations, secondary electron emission is modeled according to the Furman and Pivi's model**. In this paper we compare the simulation results of the ECLOUD buildup with the experiments performed in KEK under different beam-optics elements.
* K. Kanazawa et al., PAC05, 1054.
** M. Furman and M. Pivi, PRST-AB, 5, 124404 (2002).
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock
The electron cloud, which is initially presumed as a homogeneous distribution of static electrons, changes its transverse centroid position very fast during the passage of even a single bunch. This is due to the strong focusing transverse field of the highly relativistic positron bunch. As the density of the electrons near the beam axis grows, its impact on the beam becomes stronger. The interaction of the electron cloud with the bunch results with the shift of the betatron tune of the coherent dipole motion of the beam. In this paper we simulated the dipole tune shift of the beam interacting with the electron cloud by taking also in to account the own space-charge forces of the electrons which strongly affect the motion of the electrons during the passage of the bunch. We computed the tune shift for different transverse size and density of the electron cloud.
CLASSE, Ithaca, New York
LBNL, Berkeley, California
ANL, Argonne
CalPoly, San Luis Obispo, CA
SLAC, Menlo Park, California
The Cornell Electron Storage Ring Test Accelerator (CesrTA) program has included extensive measurements of coherent tune shifts for a variety of electron and positron beam energies, bunch current levels, and bunch train configurations. The tune shifts have been shown to result primarily from the interaction of the beam with the space-charge field of the beam-induced low-energy electron cloud in the vacuum chamber. Comparison to several advanced electron cloud simulation program packages has allowed determination of the sensitivity of these measurements to physical parameters such as the synchrotron radiation flux, its interaction with the vacuum chamber wall, the beam emittance and lattice optics, as well as to those of the various contributions to the electron secondary yield model. We report on progress in understanding the cloud buildup and decay mechanisms in magnetic fields and in field-free regions, addressing quantitatively the precise determination of the physical parameters of the modelling. Validation of these models will serve as essential input in the design of damping rings for future high-energy linear colliders.
KEK, Ibaraki
As part of the design works of the interaction region (IR) of SuperKEKB (the upgrade of KEKB B-factory (KEKB)), the loss factor and impedance of beam ducts for the interaction point (IP duct) were calculated by GdfiedL. The IP duct is round and connected to beam ducts for electron and positron beams with a diameter of 20 mm via Y-shaped crotch ducts at both ends. The lengths of the straight section and crotch section are about 200 mm, respectively. The beam crossing angle is 83 mrad. Calculations for two types of IP duct were performed. Both ducts are almost same in design except for the diameter of the straight section (20 mm and 30 mm). The loss factors were about 0.001 V/pC in both cases when the bunch length was 6 mm. The longitudinal impedances showed that there were no modes trapped longitudinally in IP duct. However, from the results of the transverse impedance and eigenmode calculation, it was found that many TE modes can be trapped at the crotch section if the beam is off-center of the beam duct. For comparison, the loss factor and impedance of the IR beam duct of KEKB are also being calculated now. Full details of the calculation results will be provided in this report.
KEK, Ibaraki
SLAC, Menlo Park, California
Grooved surfaces are effective to suppress the secondary electron emission, and can be a possible technique to mitigate the electron cloud instability (ECI) in positron/proton storage rings. Various types of triangular grooved surfaces have been studied in a laboratory, and also using an intense positron beam of the KEKB B-factory. The grooves have vertex angles of 20 ~ 30 degrees, and depths of 2.5 mm. In the laboratory, the secondary electron yield (SEY) of sample pieces were measured using an electron beam in a magnetic-free condition. The maximum SEY well below 1.0 was obtained after some extent of electron bombardment for most of grooved surfaces. To test he groove efficacy in magnetic field regions of particle accelerators, insertions with several types of grooved surfaces were installed into a test chamber in a wiggler magnet of KEKB positron ring. In a dipole-like chamber wit magnetic field (0.78 T), the reduction in the electron density around the beam was observed for a grooved section when compared to the case of a flat surface with TiN coating. An R&D effort is underway to optimize and manufacture the grooved surface in accelerator beam pipes for practical use.
National Taras Shevchenko University of Kyiv, Radiophysical Faculty, Kiev
In the report the possibilities of FEL optimization and creation of tandem laser are considered. One of the optimal ways of coherent hard radiation generation is connected with the creation of FEL on channeling relativistic particles in perfect crystals [1]. The main role in solution of such problem plays the full Doppler effect [2]. The possibility of creation of tandem FEL, where one particle can radiate multiple times on one transition, is predicted for the first time. For such laser the intensive process of consecutive generation of two types of photons with different frequencies on the same radiating transition is possible and this double photon generation leads to the restoration of the initial state of quantum system. This effect allows to predict the possibility of multiple repeat of radiation cycle. The pumping source for such laser is the kinetic energy of moving particles. In such systems there is no need for inversion and absorption on radiation frequency is totally absent. The main problem of realization of tandem FEL is connected with the need of mediums with positive susceptibility in high frequency range, possible ways to solve this problem are also regarded.
1. Vysotskii V.I., Kuzmin R.N. Gamma-Ray Lasers, MSU Publ. House, Moscow, 1989.
2. Vysotskyy M.V., Vysotskii V.I. // Nuclear Instr. and Methods in Physics Research B, 2006, V. 252, P. 75-80
KEK, Ibaraki
SLAC, Menlo Park, California
In order to mitigate the electron cloud instability (ECI) in a positron ring, an electron clearing electrode with a very thin structure has been developed. The electrode has been tested with an intense positron beam of the KEKB B-factory using a test chamber. A drastic reduction in the electron density around the beam was demonstrated in a dipole magnetic field (0.78 T). The clearing electrode was then applied to the actual copper beam pipe (94 mm in diameter) with antechambers for wiggler magnets of KEKB. The feed-through was revised to improve reliability, and the length was modified to fit a real magnet. The input power into the electrode was estimated to be approximately 80 W/m. The clear reduction in the electron density was also observed by applying a voltage of +500 V to the electrode. The design of clearing electrodes has now reached a high reliability and it is suitable for accelerator applications.
KEK, Ibaraki
The general status of the International Linear Collider (ILC) project will be presented. After the publication of the RDR (Reference Design Report) in summer in 2007, the next milestone of the ILC project will be the Technical Design Report to be completed by the end of 2012. The GDE (Global Design Effort) has defined the period till 2010 summer as the Technical Design Phase 1 and is revisiting the design in RDR in the name of 'rebaselining'. The outline of the new design will be decided in March 2010 and will be reported in this talk together with the near future plan.
LAL, Orsay
IN2P3 IPNL, Villeurbanne
CERN, Geneva
BINP SB RAS, Novosibirsk
IHEP Beijing, Beijing
The CLIC study considers the hybrid source using channeling as the baseline for unpolarised positron production. The hybrid source uses a few GeV electron beam impinging on a crystal tungsten target. With the tungsten crystal oriented on its < 111 > axis it results an intense, relatively low energy photon beam due mainly to channeling radiation. Those photons are then impinging on an amorphous tungsten target producing positrons by e+e- pair creation. The downstream capture section is based on an adiabatic matching device and a 2 GHz pre-injector linac. The resulting studies are presented here.
IPM, Tehran
The effect of surface roughness on the secondary electron emission from a sandblasted surface is investigated using a Monte-Carlo method. Sandblasted surfaces can significantly reduce the secondary emission yield and have a large sensitivity to the percentage of surface roughness.
KEK, Ibaraki
A new laser-based alignment system is under development at the KEKB injector linac. We are revisiting our alignment system because the previous alignment system has become obsolete. The new alignment system is again required to increase the stability of the electron- and positron-beam injection towards next-generation of B-factories. It is similar to the previous one, which comprises a laser-diode system and quadrant photodetectors installed in vacuum light pipes. A displacement of a girder unit of the accelerating structure can be precisely measured in the direction of the laser-ray trace, where the laser light must stably propagate up to 500-m-long downstream without any orbital and beam-size fluctuation. A novel approach in which a two-beam-interference laser-light propagates in the vacuum light pipe, has been designed to increase the alignment precision based on the quadrant photodetector measurement. The propagating laser spot sizes can be narrowed due to the two-beam interference over the Rayleigh-range limit. The design of the new laser-based alignment system is summarized along with some experimental results in this report.
CERN, Geneva
IMFD, Freiberg
KIT, Karlsruhe
FZK, Karlsruhe
Two damping rings (e+, e-) are foreseen for the CLIC injection chain. In each damping ring 76 two meter long wigglers will be installed. The short period (40-50 mm), combined with a gap larger than 14 mm and a requested field in the mid-plane BPeak > 2 T requires the usage of superconducting technologies to meet these requirements. To demonstrate the feasibility of this wiggler design a short-model vertical racetrack wiggler (40 mm period; 16 mm gap) was built and successfully tested at CERN. The wiggler carries a current of 730 A and 910 A and reaches a mid-plane peak field of Bpeak = 2 T and Bpeak = 2.5 T at 4.2 K and 1.9 K, respectively. The results show that the wiggler model meets the magnetic requirements of the CLIC damping rings at 1.9 K. The paper will also discuss the improvements we propose to enhance the performance in order to meet the CLIC specifications also at 4.2 K.
SLAC, Menlo Park, California
BARC, Mumbai
CERN, Geneva
Significant progress has been made in the design of an 18MW Beam Dump for 500 GeV electron/positron beams at an ILC. The beam dump design is based on circulating water with a vortex-like flow pattern to dissipate and remove the energy deposited by the beam. Multi-dimensional technology issues have been addressed to design the beam dump system. Detailed thermal-hydraulic analysis was carried out in all the critical regions of the beam dump which include, 1) location of highest volumetric power deposition by the beam, 2) location of highest linear power deposition, 3) entrance window region, 4) vessel walls etc. Based on this analysis, the sizing of the beam dump and its components, water flow rate and inlet jet velocity, optimum location of the beam path in the beam dump, beam sweep radius etc have been estimated. In addition, preliminary mechanical design of the beam dump, cooling circuit details, sizing of the hydrogen/oxygen recombiner system, ion exchange and 7Be removal, prompt and residual radioactivity studies etc have been carried out. Details of this work will be presented.
CERN, Geneva
UMAN, Manchester
Fermilab, Batavia
Uppsala University, Uppsala
The 1.5TeV CLIC beams, with a total power of 14MW per beam, are disrupted at the interaction point due to the very strong beam- beam effect. The resulting spent beam products are transported to suitable dumps by the post-IP beam line, which generates beam losses and causes the production of secondary cascades towards the interaction region. In this paper the electromagnetic background at the IP are presented, which were calculated using biased Monte Carlo techniques. Also, a first estimate is made of neutron back-shine from the main beam dump.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
It is proposed to investigate the option of moving the positron source to the end of the main linac as a part of the central integration in the International Linear Collider project. The positron source incorporates an undulator at the end of the main linac and the photons generated in the undulator are transported to the target, located at a distance of around 400m. The dogleg design has been optimised to provide the required transverse off-set at the location of the target and to give minimum emittance growth at 500 GeV. The design of the dogleg and the tolerances on beam tuning as a result of locating this dogleg in the beginning of the beam delivery system are presented.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Ion induced pressure instability is a potential problem for the ILC positron damping ring (DR)if the chosen pumping scheme does not provide sufficient pumping. The ion induced pressure instability effect results from ionisation of residual gas molecules by the beam particles, their acceleration in the field of the beam towards the vacuum chamber walls, causing ion induced gas desorption from vacuum chamber walls; these gas molecules in their turn can also be ionised, accelerated and cause further gas desorption. If the pumping is insufficient, this effect may cause a pressure instability, in which the pressure in the beam chamber grows rapidly to an unacceptable level. To analyse the ion induced pressure instability in the ILC positron DR the energy gained by ions was calculated for the appropriate beam parameters; it was found that the energy gain of ions will be about 300 eV. The ion induced gas desorption was estimated, and pumping solutions to avoid the ion induced pressure instability are suggested. The cheapest and most efficient solution is to use NEG coated vacuum chamber.
Cockcroft Institute, Warrington, Cheshire
A new lattice design for the ILC damping ring has been developed since the beginning of 2008 as a lower cost alternative to the previous OCS6 design. The lattices for the electron and positron damping rings are identical, and are designed to provide an intense, 5 GeV beam with low emittance at extraction. The latest design, presented in this paper, provides sufficient dynamic aperture for the large positron beam at injection. The lattice also meets the engineering requirements for arrangement of the positron ring directly above the electron ring in the same tunnel, using common girders for the magnets in the two rings, but with the beams circulating in opposite directions.
INFN/LNF, Frascati (Roma)
BINP SB RAS, Novosibirsk
In DAΦNE, the Frascati e+/e- collider, the crab waist collision scheme has been successfully implemented in 2008 and 2009. During the collision operations for Siddharta experiment, an unusual synchrotron damping effect has been observed. Indeed, with the longitudinal feedback switched off, the positron beam becomes unstable with beam currents in the order of 200-300 mA. The longitudinal instability is damped by bringing the positron beam in collision with a high current electron beam (~2A). Besides, we have observed a shift of ≈600Hz in the residual synchrotron sidebands. Precise measurements have been performed by using a commercial spectrum analyzer and by using the diagnostics capabilities of the DAΦNE longitudinal bunch-by-bunch feedback. This damping effect has been observed in DAΦNE for the first time during collisions with the crab waist scheme. Our explanation is that beam collisions with a large crossing angle produce a longitudinal tune shift and a longitudinal tune spread, providing Landau damping of synchrotron oscillations.
INFN/LNF, Frascati (Roma)
CEA, Gif-sur-Yvette
LAL, Orsay
SLAC, Menlo Park, California
The ultra high luminosity B-factory (SuperB) project of INFN requires a high performance and reliable injection system, providing electrons at 4 GeV and positrons at 7 GeV, to fulfill the very tight requirements of the collider. Due to the short beam lifetime, continuous injection of electrons and positrons in both HER and LER rings is necessary to keep the average luminosity at a high level. Polarized electrons are required for experiments and must be delivered by the injection system, due to the beam lifetime shorter than the polarization build-up: they will be produced by means of a SLAC-SLC polarized gun. One or two 1 GeV damping rings are used to reduce e+ and e- emittances. Two schemes for positron production are under study, one with electron-positron conversion at low energy (<1 Gev), the second at 6 GeV with a recirculation line to bring the positrons back to the damping ring. Acceleration through the Linac is provided by a S-band RF system made of traveling wave, room temperature accelerating structures. An option to use the C-band technology is also presented.
KEK, Ibaraki
In order to improve the capture efficiency of the positron produced at the target in present KEKB Injector linac, a new project has just started to utilize L-band (1298MHz) RF. The present S-band (2856MHz) capture cavities and successive three RF units are to be replaced by those of L-band. The specifications of the L-Band system should fulfill the demands of a positron damping ring downstream which is also to be under study for super KEKB project. Besides the whole design work of the system, our present ongoing work is rather concentrated on establishing L-Band RF source and accelerating structures.
KEK, Ibaraki
For future high-intensity positron or proton accelerators, beam instability caused by electron cloud is one of the most important problems. Some coatings on inner surface of beam chambers with materials having low secondary emission yields such as titanium nitride (TiN), non-evaporable getter and so on have represented good effects against the electron cloud instability. In this study, diamond like carbon (DLC) and TiN coated chambers, and a copper chamber without coating were installed to an arc section of KEKB LER to make comparisons of total pressure, residual gas components and electron cloud activity during the beam operation under the same condition. Residual gas observation for the DLC coating revealed much higher hydrogen gas desorption because a process gas including hydrogen was used for the film growth. No remarkable hydrocarbon gas desorption was found. On the other hand, a mass peak of amu=14, that is N+ was prominent in the TiN coating. The electron cloud activity in the DLC coating was lower than the TiN coating and the copper chamber.
KEK, Ibaraki
OHTSUKA, Tsukuba-shi
The MO (Matsumoto-Ohtsuka) -type flange is suitable for connection flanges of beam pipes for accelerators. The flange uses a metal gasket that exactly fits the aperture of the beam pipe, and has a small beam impedance. The flange can be applied to a complicated aperture. We developed a stainless-steel MO-type flange for a copper beam pipe with antechambers. Several beam pipes were installed in the KEKB B-factory positron ring and were tested using beams. No serious problem was observed up to a beam current of 1600 mA (~10 nC/bunch and ~6 ns bunch spacing). Based on experiences in the stain-less steel case, a possibility of employing copper-alloy and aluminum-alloy MO-type flange has been experimentally studied. They can mitigate the heating problems found in the case of stainless-steel flanges, and simplify the manufacturing procedure of beam pipes made of copper or aluminum alloy. Copper-alloy (CrZrCu) flanges show a comparable vacuum sealing property to the stainless-steel one, and several beam pipes with this flange has been successfully installed in the KEKB. The R&D on aluminum-alloy (A2219 and A2024) flanges has recently started, and a promising result was obtained.
DESY Zeuthen, Zeuthen
The development of an intense polarised positron sources provides a challenge for a new generation of linear colliders. The software framework Geant4, a toolkit for simulation of the passage of particles trough matter, features tracking capabilities of charged particles in electromagnetic fields, and also includes the description of polarisation transfer in scattering processes. Based on Geant4 a novel simulation tool, PPS-Sim*, has been developed to optimise the design and to determine polarisation, beam properties, as well as energy deposition in accelerator components. All source components and their parameters can be chosen easily and flexible. Helical undulator, laser-Compton and coherent Bremsstrahlung in crystals are available as positron production schemes. Target materials and geometry can be adjusted. Flux concentrator, quarter wave transformer and lithium lens are implemented as possible capture devices. Geometry, accelerating components and magnetic field configuration can be specified by the user. In this contribution, PPS-Sim will be presented, and selected results for linear collider applications will be discussed.
* PPS-Sim web page - http://pps-sim.desy.de
Cockcroft Institute, Warrington, Cheshire
Lancaster University, Lancaster
LLNL, Livermore, California
Imperial College of Science and Technology, Department of Physics, London
The University of Liverpool, Liverpool
The efficiency of future positron sources for the next generation of high-energy particle colliders (e.g. ILC, CLIC, LHeC) can be improved if the positron-production target is immersed in the magnetic field of adjacent capture optics. If the target is also rotating due to heat deposition considerations then eddy currents may be induced and lead to additional heating and stresses. In this paper we present data from a rotating target wheel prototype for the baseline ILC positron source. The wheel has been operated at revolution rates up to 1800rpm in fields of the order of 1 Tesla. Comparisons are made between torque data obtained from a transducer on the target drive shaft and the results of finite-element simulations. Rotordynamics issues are presented and future experiments on other aspects of the positron source target station are considered.
Cockcroft Institute, Warrington, Cheshire
Lancaster University, Lancaster
The University of Liverpool, Liverpool
CLIC will need of order 10 to the 14 positrons per second to achieve its specified luminosity. For such a challenge, an undulator based scheme has been proposed as one of the options for the positron source. As CLIC may operate over a wide range of energy (from 0.5 TeV to 3 TeV), there is a large margin for us to push the performance of the whole system to be more efficient. We report on the undulator parameters and optimization of components of the source such as conversion target, AMD, solenoid and capture RF for different operational scenarios. In addition to maximizing the positron yield the polarization of the positron beam are also considered.
ANL, Argonne
CERN, Geneva
SLAC, Menlo Park, California
We propose a viable positron source scheme that uses circularly polarized gamma rays generated from the main 250 GeV electron beam. The beam passes through a helical superconducting undulator with a magnetic field of ~ 1 Tesla and a period of a few centimeters. The gamma-rays produced in the undulator in the energy range between ~ 3 MeV ~ 100 MeV will be directed to a titanium target and produces polarized positrons. The positrons are then captured, accelerated and transported to a damping ring. Detailed parameter studies of this scheme including positron yield, undulator parameter dependence and target composition and geometry will be presented. Effects on the 250 GeV drive beam, including emittance, energy spread and energy loss from the beam passing through the undulator will also be discussed.
ANL, Argonne
We present an update on the ANL ILC positron source study. We examined the impact of different drive beam energies on the positron yield and polarization for the ILC RDR baseline undulator. The e+ yield is found to drop rapidly as the drive beam energy is reduced. We studied different undulator parameters for their effect on the positron yield and polarization when working at lower drive beam energies. Using a lower K (B field level) can increase the photon energy, but it is still very difficult to bring the yield up for low drive beam energies. For 250 GeV drive beam options, we studied the RDR undulator performance as a function of K. Instead of powering off some sections of the undulator, one can also consider lowering the B field to bring the positron yield back to the desired 1.5 e+/e-. We also studied the liquid lead target option for ILC positron source and the energy deposition in the reference design Ti target wheel.
LLNL, Livermore, California
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The positron source at a future TeV scale electron linear collider will need to generate positrons at a rate two orders of magnitude larger than have been previously achieved. We report on a design of a 3.5 Tesla pulsed flux concentrator magnet which uses liquid nitrogen cooling of the flux concentrator plates to reduce the electrical resistance leading to reduced energy deposition and the ability to generate the required 1 ms pulse duration. This magnet can double the collection efficiency of positrons emitted from the target.
JINR, Dubna, Moscow Region
The radioactive ion isotopes 11C6+, 10C6+ and others are produced at interaction of primary carbon ion beam with target. These isotopes can be applied for Positron Emission Tomography. The projectile-fragmentation method is used for the production of radioactive isotopes. The intensity of radioactive ion beam is defined by the target optimal thickness, material and by available longitudinal and transverse acceptances of transportation channel. An increase of target thickness permits to improve production rate of radioactive ion beams, however it increase the energy and angle spreads of secondary ions and finally it gives a reduction of number of useful radioactive ions which can be transported to the PET camera. The GEANT 4 simulations related to formation of 11C6+ secondary ion beams at interaction with different targets are discussed.
KEK, Ibaraki
SuperKEKB, the upgrade plan of KEKB, aims to boost the luminosity up to 8·1035 /cm2/s. The beam energy of the Low Energy Ring (LER) is 4 GeV for positrons, and that of the High Energy Ring is 7 GeV for electrons. SuperKEKB is designed to produce low emittance beams. The horizontal and vertical emittances of the injection beams are 4nm and 1nm, respectively, which are one or two orders smaller than those of KEKB. The positron injector system consists of the source, capture system, L-band and S-band linacs, collimators, an energy compression system (ECS), a 1-GeV damping ring, a bunch compression system (BCS), S-band and C-band linacs, and a beam transport line into the LER. This paper reports a design of the positron beam transport system from L-band linacs to SuperKEKB.
KEK, Ibaraki
The KEK injector linac sequentially provides beams, and transfers them to the following four storage rings: a KEKB low-energy ring (LER) (3.5 GeV/positron), a KEKB high-energy ring (HER) (8 GeV/electron), a Photon Factory ring (PF ring; 2.5 GeV/electron), and an Advanced Ring for Pulse X-rays (PF-AR; 3 GeV/electron). So far, beam injection to the PF ring and PF-AR is carried out twice a day, whereas the KEKB rings are operated in the continuous injection mode (CIM) so that the stored current remains almost constant. The KEK linac upgrade project has been started since 2004 so that the PF top-up and KEKB CIM can be performed at the same time. The aim of this upgrade is to change the linac parameters up to 50 Hz, which is the maximum linac beam repetition rate, by using a multi-energy-linac scheme. This upgrade has been successfully completed. The simultaneous top-up operation for three rings has stably been carried out since this April. We will report the simultaneous top-up injection for the KEKB and PF rings in detail.
KEK, Ibaraki
The next generation B-factory 'SuperKEKB' project whose target luminosity is 8 ×1035 cm-2s-1 is under consideration. A 'nano-beam scheme' is introduced to the SuperKEKB. In the scheme, an electron beam (Energy = 7 GeV, Charge = 3-4 nC/bunch, Vertical emittance =2.8 x 10-5 m) and a positron beam (Energy = 4 GeV, Charge = 4 nC/bunch, Vertical emittance = 1.6 x 10-5 m), are required at the end of injector linac. They are quite challenging targets for the present linac. In order to meet the requirements, we will introduce some new components to the linac. They are a photo-cathode RF gun for an electron beam, a positron capture section using new L-band cavities, a newly designed positron-generation target system and a damping ring for a positron beam. This presentation shows a strategy of our injector upgrade.
Fermilab, Batavia
CERN, Geneva
Polarized positron and electron beams are ideal for searching for new physics at the Compact Linear Collider (CLIC). In order to properly orient and preserve the polarization of the beam at the interaction point, the beam polarization must be manipulated by a spin rotator along the beam line. In this paper a spin rotator design for the CLIC is presented and its integration into the CLIC ring to main linac transport system is discussed.