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Stability of non-linear integrable accelerator

Description: The stability of non-linear Integrable Optics Test Accelerator (IOTA) model developed in [1] was tested. The area of the stable region in transverse coordinates and the maximum attainable tune spread were found as a function of non-linear lens strength. Particle loss as a function of turn number was analyzed to determine whether a dynamic aperture limitation present in the system. The system was also tested with sextupoles included in the machine for chromaticity compensation. A method of evaluation of the beam size in the linear part of the accelerator was proposed.
Date: September 1, 2011
Creator: Batalov, I.; /Moscow, MIPT; Valishev, A. & /Fermilab
Partner: UNT Libraries Government Documents Department

Transverse instability of the antiproton beam in the Recycler Ring

Description: The brightness of the antiproton beam in Fermilab's 8 GeV Recycler ring is limited by a transverse instability. This instability has occurred during the extraction process to the Tevatron for large stacks of antiprotons even with dampers in operation. This paper describes observed features of the instability, introduces the threshold phase density to characterize the beam stability, and finds the results to be in agreement with a resistive wall instability model. Effective exclusion of the longitudinal tails from Landau damping by decreasing the depth of the RF potential well is observed to lower the threshold density by up to a factor of two.
Date: March 1, 2011
Creator: Prost, L.R.; Bhat, C.M.; Burov, A.; Crisp, J.; Eddy, N.; Hu, M. et al.
Partner: UNT Libraries Government Documents Department

A Study of Laser System Requirements for Application in Beam Diagnostics And Polarimetry at the ILC

Description: Advanced laser systems will be essential for a range of diagnostics devices and polarimetry at the ILC. High average power, high beam quality, excellent stability and reliability will be crucial in order to deliver the information required to attain the necessary ILC luminosity as well as for efficient polarimetry. The key parameters are listed together with the R & D required to achieve the necessary laser system performance.
Date: February 12, 2007
Creator: Dixit, S.; Delerue, N.; Foster, B.; Howell, D. F.; Peach, K.; Quelch, G. et al.
Partner: UNT Libraries Government Documents Department

Betatron-Function Measurement in Lattices with 90-Degrees Sections

Description: Lattice functions derived from betatron phase-advance measurements have been used successfully at many e{sup +}-e{sup -} facilities in the world, including at the PEP-II High Energy Ring. For the Low energy Ring of PEP-II, however, extraction of meaningful beta functions is hampered by the 90{sup o} phase advance/cell in the arcs, which causes a singularity in the expressions for beta. An algorithm has been developed calculating beta functions based on {beta} and {alpha} at the beginning of an arc and tracking the Twiss parameters through the arc while matching the observed phase advance/cell. Stability of the algorithm is improved by doing the same calculation 'backward' as well as forward and averaging the result. The algorithm allows estimating beta functions at bad BPMs in many cases. The paper presents the algorithm used as well as examples of use in PEP.
Date: April 24, 2012
Creator: Wienands, U.; /SLAC; Biagini, M.E. & /Frascati
Partner: UNT Libraries Government Documents Department

Development of Electronics for the ATF2 Interaction Point Region Beam Position Monitor

Description: Nanometer resolution beam position monitors have been developed to measure and control beam position stability at the interaction point region of ATF2. The position of the beam has to be measured to within a few nanometers at the interaction point. In order to achieve this performance, electronics for the low-Q IP-BPM was developed. Every component of the electronics have been simulated and checked on the bench and using the ATF2 beam. We will explain each component and define their working range. Then, we will show the performance of the electronics measured with beam signal. ATF2 is a final focus test beam line for ILC in the framework of the ATF international collaboration. The new beam line was constructed to extend the extraction line at ATF, KEK, Japan. The first goal of ATF2 is the acheiving of a 37 nm vertical beam size at focal point (IP). The second goal is to stabilize the beam at the focal point at a few nanometer level for a long period in order to ensure the high luminosity. To achieve these goals a high resolution IP-BPM is essential. In addition for feedback applications a low-Q system is desirable.
Date: August 14, 2012
Creator: Kim, Youngim; U., /Kyungpook Natl.; Heo, Ae-young; U., /Kyungpook Natl.; Kim, Eun-San; U., /Kyungpook Natl. et al.
Partner: UNT Libraries Government Documents Department

The Straightness Monitor System at ATF2

Description: The demonstration of absolute stability of the position of the focused beam is the primary goal of the ATF2 commissioning effort. We have installed a laser interferometer system that will eventually correct the measurement of high-precision Beam Position Monitors used in the ATF2Final Focus Steering Feedback for mechanical motion or vibrations. Here, we describe the installed system and present preliminary data on the short- and long-term mechanical stability of the BPM system.
Date: July 6, 2012
Creator: Hildreth, Michael; U., /Notre Dame; Aryshev, Alexander; /Royal Holloway, U. of London; Boogert, Stewart; /Oxford U., JAI et al.
Partner: UNT Libraries Government Documents Department

Phase and Frequency Locked Magnetrons for SRF Sources

Description: Magnetrons are low-cost highly-efficient microwave sources, but they have several limitations, primarily centered about the phase and frequency stability of their output. When the stability requirements are low, such as for medical accelerators or kitchen ovens, magnetrons are the very efficient power source of choice. But for high energy accelerators, because of the need for frequency and phase stability - proton accelerators need 1-2 degrees source phase stability, and electron accelerators need .1-.2 degrees of phase stability - they have rarely been used. We describe a novel variable frequency cavity technique which will be utilized to phase and frequency lock magnetrons.
Date: May 1, 2009
Creator: Neubauer, M.; Johnson, R.P.; /Muons Inc., Batavia; Popovic, M.; Moretti, A. & /Fermilab
Partner: UNT Libraries Government Documents Department

Measurement of critical current and instability threshold of rutherford-type nb3sn cables

Description: As part of a collaboration between FNAL and CERN, Nb{sub 3}Sn Rutherford-type cables made of different wires (MJR and PIT) have been assembled in the sample holder at FNAL and tested at FRESCA (CERN). All cable samples had 28 strands with 1-mm diameter, and a trapezoidal cross-section with 0.9-1 degree keystone angle. All samples were tested at 4.3 and 1.8 K. After the first series of tests both cables were retested with higher prestress. The PIT sample was extensively retested at 1.9 K. During the second run the MJR sample was also tested at constant current in sweeping field in order to characterize its stability. All samples showed signs of instability and several voltage spikes were detected and recorded. Critical current and instability threshold measurements are presented and compared with previous tests and magnet performances.
Date: December 1, 2005
Creator: Ambrosio, G.; Andreev, N.; Barzi, E.; Bordini, B.; /Fermilab; Denarie, C.-H. et al.
Partner: UNT Libraries Government Documents Department

Issues of Stability and Ground Motion in ILC

Description: Stability of International Linear Collider is determined by the stability of the site, additional noises of beamline component, energy and kicker jitter, and performance of train-to-train and intratrain feedback. Stability goals in terms of the beam jitter at the end of the linac, in BDS and at the IP are discussed in this paper, and translated to stability goals for the site and for component jitter. Present status of stability studies is reviewed and feasibility of achieving the stability goals is discussed.
Date: February 3, 2006
Creator: Seryi, Andrei; Hendrickson, Linda; White, Glen & /SLAC
Partner: UNT Libraries Government Documents Department

Analysis of DESY-Flash LLRF Measurements for the ILC Heavy Beam Loading Test

Description: In September 2008 the DESY-FLASH accelerator was run with up to 550, 3 nano-coulomb bunches at 5 Hz repetition rate. This test is part of a longer-term study aimed at validating ILC parameters by operation as close as possible to ILC beam currents and RF gradients. The present paper reports on the analysis that has been done in order to understand the RF control system performance during this test. Actual klystron power requirements and beam stability are evaluated with heavy beam loading conditions. Results include suggested improvements for upcoming tests in 2009.
Date: June 1, 2009
Creator: Cancelo, Gustavo; Chase, Brian; Davidsaver, Michael; /Fermilab; Carwardine, J.; /Argonne et al.
Partner: UNT Libraries Government Documents Department

Stability of Flat Bunches in the Recycler Barrier Bucket

Description: We examine the stability of intense flat bunches in barrier buckets used in the Fermilab Recycler. We consider some common stationary distributions and show that they would be unstable against rigid dipole oscillations. We discuss the measurements which identify stable distributions. We also report on experimental studies on the impact of creating a local extremum of the incoherent frequency within the rf bucket. We considered two typical stationary distributions and found they were not adequate descriptions of the Recycler bunches. From the measured line density distribution we find (a) the tanh function is a good fit to the line density, and (b) the coherent frequency of the rigid dipole mode for this distribution is within the incoherent spread at nominal intensities. Stability diagrams when the beam couples to space charge and external impedances will be discussed elsewhere. Our initial experimental investigations indicate that longitudinal stability in the Recycler is, consistent with expectations, influenced by the ratio T{sub 2}/(4T{sub 1}) which determines the location of the extremum of the incoherent tune. The coherent tune depends strongly on the distribution in the bunch tails which is difficult to measure. Numerical studies using both a conventional tracking code and a Vlasov solver are in progress and should provide more insight into conditions that may lead to unstable behavior.
Date: May 1, 2009
Creator: Sen, T.; Bhat, C.; Ostiguy, J.-F. & /Fermilab
Partner: UNT Libraries Government Documents Department

Single Bunch Stability in LER of PEP II

Description: The note describes results of studies of the single bunch stability in the low energy ring (LER) of the PEP-II B-factory. Simulations describe the potential well distortion (PWD) obtained by numerical solution of the Haiisinski equation and results on the beam stability obtained with the code TRISIM. Both longitudinal and transverse wake fields are taken into account. Preliminary estimates indicate that single bunch in the LER of the PEP-II B-factory has to be stable, both longitudinally and transversely, at the maximum design bunch current 1.8 mA (beam current 3A). However, realistic wakes of the machine has been constructed only recently using results of the extensive numerical simulations of the vacuum components of the ring. Additional to that, the code TRISIM, a simulation program for single-bunch collective effects written by one of the authors (G. S.), became recently available. This allows us to study beam stability in a more reliable way than it is possible analytically.
Date: October 11, 2011
Creator: Heifets, S.; /SLAC; Sabbi, G. & /Fermilab
Partner: UNT Libraries Government Documents Department

Simulation of Wakefield Effect in ILC IR Chamber

Description: To achieve super high luminosity, high current beams with very short bunch length are needed, which carry high intensity EM fields. For ILC, two bunch trains with bunch length of 300 {micro}m and bunch charge of 3.2nC are needed to collide at the IR to achieve the ILC luminosity goals. When the 300 {micro}m bunches pass through the IR chamber, wakefields will be excited, which will cause HOM power flowing through the IR chamber beam pipe to the final doublets due to the high frequency characteristic of the induced wakefields. Since superconducting technology is adopted for the final doublets of ILC BDS, whose operation stability might be affected by the HOM power produced at the IR chamber, quench might happen. In this paper, we did some analytical estimation and numerical simulation on the wakefield effects in ILC IR chamber.
Date: June 26, 2008
Creator: Pei, S; Seryi, A.; Raubenheimer, T.O. & /SLAC
Partner: UNT Libraries Government Documents Department

Coherent instabilities at the FNAL Booster

Description: This paper presents results of experimental and theoretical investigations of transverse beam stability at injection to Fermilab Booster and discusses a novel scheme for transition crossing allowing to avoid the longitudinal emittance growth related to the transition. At reduced chromaticity a multibunch high order head-tail mode develops with growth time of 12 turns at fractional part of tune close to zero. An estimate of the growth rate based on known sources of impedance results in significantly smaller value and cannot explain observed instability growth rate.
Date: June 1, 2006
Creator: Lebedev, V.; Burov, A.; Pellico, W.; Yang, X. & /Fermilab
Partner: UNT Libraries Government Documents Department

Optics implications of implementing Nb3Sn magnets in the LHC phase 1 upgrade

Description: CERN has encouraged the US-LARP collaboration to participate in Phase I of the LHC luminosity upgrade by analyzing the benefits gained by using Nb3Sn technology to replace the functionality of select NbTi magnets that CERN is committed to construct. Early studies have shown that the much higher gradients (shorter magnetic lengths) and temperature margins (quench stability) of Nb3Sn magnets compared to their NbTi counterparts is favorable--allowing the insertion of additional absorbers between Q1 and Q2, for example. This paper discusses the relative merits of the NbTi and Nb3Sn options.
Date: June 1, 2008
Creator: Johnstone, J.A.; Kashikhin, V.V.; Mokhov, N.V.; Zlobin, A.V. & /Fermilab
Partner: UNT Libraries Government Documents Department

Present Status And First Results of the Final Focus Beam Line at the KEK Accelerator Test Facility

Description: ATF2 is a final-focus test beam line which aims to focus the low emittance beam from the ATF damping ring to a vertical size of about 37 nm and to demonstrate nanometer level beam stability. Several advanced beam diagnostics and feedback tools are used. In December 2008, construction and installation were completed and beam commissioning started, supported by an international team of Asian, European, and U.S. scientists. The present status and first results are described.
Date: November 11, 2011
Creator: Bambade, P.; Alabau Pons, M.; Amann, J.; Angal-Kalinin, D.; Apsimon, R.; Araki, S. et al.
Partner: UNT Libraries Government Documents Department

ATF2 Commissioning

Description: ATF2 is a final-focus test beam line that aims to focus the low-emittance beam from the ATF damping ring to a beam size of about 37 nm, and at the same time to demonstrate nm beam stability, using numerous advanced beam diagnostics and feedback tools. The construction has been finished at the end of 2008 and the beam commissioning of ATF2 has started in December of 2008. ATF2 is constructed and commissioned by ATF international collaborations with strong US, Asian and European participation.
Date: October 30, 2009
Creator: Seryi, A.; Christian, G.; Parker, B.; Schulte, D.; Delahaye, J. -P.; Tomas, R. et al.
Partner: UNT Libraries Government Documents Department

Trapped Ions and Beam Coherent Instability

Description: In accelerators with negatively charged beams, ions generated from the residual gas molecules may be trapped by the beam. Trapped ions may interact resonantly with the beam and cause a beam-ion coherent instability. This coherent instability bears many similarities to the resistive wall instability and can present important limitations to those machines operation. A description of this effect requires a treatment of the beam coherent instability including both the normal machine wake field and the interaction with ions. They present a linear approach incorporating contributions from the machine impedance as well as ion forces. it also includes spreads in beam and ion frequencies and thus Landau damping. The analysis results in a modified stability diagram which will be used together with physical arguments to explain experimental observations in the Fermilab antiproton accumulator.
Date: January 1, 1992
Creator: Zhou, P.; Colestock, P.L.; Werkema, S.J. & /Fermilab
Partner: UNT Libraries Government Documents Department

Field Quality And Magnetic Center Stability Achieved in a Variable Permanent Magnet Quadrupole for the ILC

Description: A superstrong permanent magnet quadrupole (PMQ) is one of the candidates for the final focus lens for the International Linear Collider (ILC). Our prototype PMQ can produce variable strengths from 3.5T to 24.2T in 1.4T steps. The magnetic center of the PMQ must not move more than a few microns during a 20% strength change to enable a Beam-Based Alignment (BBA) process to work. Our PMQ can be mechanically adjusted to suppress the center movement from more than 30{micro}m to less than 10{micro}m during strength changes.
Date: February 6, 2006
Creator: Iwashita, Y.; Mihara, T.; Kumada, M. & Spencer, C.
Partner: UNT Libraries Government Documents Department

On possible use of electron lenses in LHC

Description: We present basic facts about electron lenses used in high-energy accelerators and discuss their possible application in the LHC. Four proposals are presented: (a) electron lenses for compensation of head-on beam-beam effects; (b) electron lens as tune-spreader for better beam stability; (c) as electromagnetic primary collimator for ions and protons; (d) satellite bunch cleaning by electron lenses. Main requirements are discussed.
Date: October 1, 2006
Creator: Shiltsev, V.
Partner: UNT Libraries Government Documents Department

Results of head-on beam-beam compensation studies at the Tevatron

Description: At the Tevatron collider, we studied the feasibility of suppressing the antiproton head-on beam-beamtune spread using a magnetically confined 5-keV electron beam with Gaussian transverse profile overlapping with the circulating beam. When electron cooling of antiprotons is applied in regular Tevatron operations, the head-on beam-beam effect on antiprotons is small. Therefore, we first focused on the operational aspects, such as beam alignment and stability, and on fundamental observations of tune shifts, tune spreads, lifetimes, and emittances. We also attempted two special collider stores with only 3 proton bunches colliding with 3 antiproton bunches, to suppress long-range forces and enhance head-on effects. We present here the results of this study and a comparison between numerical simulations and observations, in view of the planned application of this compensation concept to RHIC.
Date: March 1, 2011
Creator: Valishev, A. & Stancari, G.
Partner: UNT Libraries Government Documents Department

Conceptual design of the Project-X 1.3 GHz 3-8 GeV pulsed linac

Description: Project-X, a multi-MW proton source, is under development at Fermilab. It enables a Long Baseline Neutrino Experiment via a new beam line pointed to DUSEL in Lead, South Dakota, and a broad suite of rare decay experiments. The initial acceleration is provided by a 3-GeV 1-mA CW superconducting linac. In a second stage, about 5% of the H{sup -} beam is accelerated up to 8 GeV in a 1.3 GHz SRF pulsed linac and injected into the Recycler/Main Injector complex. In order to mitigate problems with stripping foil heating during injection, higher current pulses are accelerated in the CW linac in conjunction with the 1 mA beam which is separated and further accelerated in the pulsed linac. The optimal current in the pulsed linac is discussed as well as the constraints that led to its selection. A conceptual design which covers optics and RF stability analysis is presented. Finally, the need for HOM damping is discussed.
Date: March 1, 2011
Creator: Solyak, N.; Eidelman, Y.; Nagaitsev, S.; Ostiguy, J.-F.; Vostrikov, A.; Yakovlev, V. et al.
Partner: UNT Libraries Government Documents Department

Chromaticity correction for a muon collider optics

Description: Muon Collider (MC) is a promising candidate for the next energy frontier machine. However, in order to obtain peak luminosity in the 10{sup 34} cm{sup 2}s{sup -1} range the collider lattice designmust satisfy a number of stringent requirements. In particular the expected large momentum spread of the muon beam and the very small {beta}* call for a careful correction of the chromatic effects. Here we present a particular solution for the interaction region (IR) optics whose distinctive feature is a three-sextupole local chromatic correction scheme. The scheme may be applied to other future machines where chromatic effects are expected to be large. The expected large muon energy spread requires the optics to be stable over a wide range of momenta whereas the required luminosity calls for {beta}* in the mm range. To avoid luminosity degradation due to hour-glass effect, the bunch length must be comparatively small. To keep the needed RF voltage within feasible limits the momentum compaction factor must be small over the wide range of momenta. A low {beta}* means high sensitivity to alignment and field errors of the Interaction Region (IR) quadrupoles and large chromatic effects which limit the momentum range of optics stability and require strong correction sextupoles, which eventually limit the Dynamic Aperture (DA). Finally, the ring circumference should be as small as possible, luminosity being inversely proportional to the collider length. A promising solution for a 1.5 TeV center of mass energy MC with {beta}* = 1 m in both planes has been proposed. This {beta}* value has been chosen as a compromise between luminosity and feasibility based on the magnet design and energy deposition considerations. The proposed solution for the IR optics together with a new flexible momentum compaction arc cell design allows to satisfy all requirements and is relatively insensitive to the ...
Date: March 1, 2011
Creator: Alexahin, Y.; Gianfelice-Wendt, E.; Kapin, V. & /Fermilab
Partner: UNT Libraries Government Documents Department

Loss of Landau Damping for Bunch Oscillations

Description: Conditions for the existence, uniqueness and stability of self-consistent bunch steady states are considered. For the existence and uniqueness problems, simple algebraic criteria are derived for both the action and Hamiltonian domain distributions. For the stability problem, van Kampen theory is used. The onset of a discrete van Kampen mode means the emergence of a coherent mode without any Landau damping; thus, even a tiny couple-bunch or multi-turn wake is sufficient to drive the instability. The method presented here assumes an arbitrary impedance, RF shape, and beam distribution function. Available areas on the intensity-emittance plane are shown for resistive wall wake and single harmonic, bunch shortening and bunch lengthening RF configurations. Thresholds calculated for the Tevatron parameters and impedance model are in agreement with the observations. These thresholds are found to be extremely sensitive to the small-argument behaviour of the bunch distribution function. Accordingly, a method to increase the LLD threshold is suggested. This article summarizes and extends recent author's publications.
Date: April 11, 2011
Creator: Burov, A.
Partner: UNT Libraries Government Documents Department