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| MOPMA001 | Comparison of Measurements and Simulations for Single Bunch Instabilities at Diamond | 521 |
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| The single bunch dynamics in the Diamond storage ring has been analysed with a multiparticle tracking code and compared with the results of a wealth of diagnostics, including streak camera, Schottky diodes and FTIR spectra. The interplay of various wakefield sources has been studied and it has been found that the THz spectrum can be reproduced in many cases with simple impedance models, both below and above the bursting threshold. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA001 | |
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| MOPMA002 | Optimising the Diamond DDBA Upgrade Lattice for Low Alpha Operation | 525 |
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The Diamond storage ring will be upgraded during 2016 by replacing one of the existing double bend achromat (DBA) cells with a double-DBA (DDBA) cell*. One requirement of the upgrade is that following the installation of the new cell, Diamond should continue to offer dedicated user time in ‘low alpha’ mode**. In this paper we describe the particular challenges relating to this task, and present the lattice design and optimisation studies undertaken so far. The paper concludes by discussing preliminary studies of adding a second DDBA cell into the storage ring.
* R.P. Walker et al., Proc. IPAC 2014, MOPRO103, (2014) ** I.P.S. Martin et al., Proc. IPAC 2013, MOPEA070, (2013) |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA002 | |
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| MOPMA003 | Reconstruction of Electron Bunch Motion During CSR Bursts using Synchronised Diagnostics | 529 |
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| Above a certain threshold current, electron bunches become unstable and emit bursts of coherent synchrotron radiation (CSR). The character and periodicity of these bursts vary with bunch current, RF voltage and lattice momentum compaction. In this paper we describe recent measurements taken at Diamond of how the electron bunch longitudinal profile and energy vary during a burst, and correlate this with CSR emission at a range of wavelengths. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA003 | |
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| MOPMA004 | Numerical Optimization of Accelerators within oPAC | 533 |
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Funding: This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289485. Powerful simulation tools are required for every accelerator and light source to study the motion of charged particles through electromagnetic fields during the accelerator design process, to optimize the performance of machine diagnostics and to assess beam stability and non-linear effects. The Optimization of Particle Accelerators (oPAC) Project is funded by the EU within the 7th Framework Programme and currently supports 23 Fellows that are based at institutions across Europe. This large network carries out R&D that closely links beam physics studies with the development of diagnostics and beyond state-of-the-art simulation tools. This contribution presents selected research outcomes from oPAC, including the numerical optimization of beam loss monitor locations along the European Spallation Source’s 5 MW proton linac, results from tracking studies for the LHeC lattice that allow beam stability to be assessed, and multi-objective optimization of the linear and non-linear beam dynamics of the synchrotron SOLEIL. In addition, an overview of recent and future oPAC events is also given. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA004 | |
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| MOPMA005 | Non-invasive Beam Profile Monitoring | 537 |
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Funding: Work supported by the Helmholtz Association under contract VH-NG-328, the EU under contracts 215080 and 289485, as well as the STFC Cockcroft core grant No. ST/G008248/1. State-of-the-art high energy and high intensity accelerators require new approaches to transverse beam profile monitoring as many established techniques will no longer work due to the high power stored in the beam. In addition, many accelerator applications such as ion beam cancer therapy or material irradiation would benefit significantly from the availability of non-invasive beam profile monitors. Research in the QUASAR Group has focused on this area over the past 5 years. Two different approaches were successfully developed: Firstly, a supersonic gas jet-based monitor was designed and commissioned. It enables the detection of the 2-dimensional transverse beam profile of essentially any charged particle beam with negligible disturbance of the primary beam and accelerator vacuum. Secondly, a monitor based on the Silicon strip VELO detector, originally developed for the LHCb experiment, was tested as an online beam monitor at the Clatterbridge Cancer Center in the UK. The design of both monitors is presented in this contribution. Results from measurements are discussed and complemented by numerical studies into the performance limits of either technique. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA005 | |
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| MOPMA006 | Modeling RF Feedback in Elegant for Bunch-Lengthening Studies for the Advanced Photon Source Upgrade | 540 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The proposed Advanced Photon Source (APS) multi-bend achromat (MBA) lattice includes a passive bunch-lengthening cavity to alleviate lifetime and emittance concerns. Feedback in the main radio-frequency (rf) system affects the overall impedance presented to the beam in this double rf system. To aid beam stability studies, a realistic model of rf feedback has been developed and implemented in elegant and Pelegant. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA006 | |
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| MOPMA007 | Tracking Studies of a Higher-Harmonic Bunch-Lengthening Cavity for the Advanced Photon Source Upgrade | 543 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source (APS) multi-bend achromat (MBA) lattice will require a bunch-lengthening cavity to decrease the effects of Touschek scattering on the beam lifetime and of intrabeam scattering on the beam emittance. Using ELEGANT, we've performed tracking studies of a passive, i.e. beam-driven, fourth-harmonic cavity in the MBA lattice, including the predicted longitudinal impedance of the ring. The studies include an exploration of the required detuning and loaded Q of the main rf cavities and the harmonic cavity in order to stabilize the beam and achieve significant lengthening. We also studied the effects of bunch population variation and missing bunches. The computed bunch profiles are used for computation of the Touschek lifetime, verifying the beneficial effects in detail. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA007 | |
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| MOPMA008 | Simulation of Gas-Scattering Lifetime using Position- and Species-Dependent Pressure and Aperture Profiles | 546 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. When computing gas-scattering lifetime for storage rings, it is common to use the average pressure, even though it is known that the pressure varies with location in the ring and varies differently for different gas species. In addition, other simplifications are commonly made, such as assuming that the apertures in the horizontal and vertical planes are independent and assuming that the momentum acceptance can be characterized by a single value. In this paper, we describe computation of the elastic- and bremsstrahlung-scattering lifetimes that includes species-specific gas pressure profiles computed with VACCALC and MOLFLOW. In addition, the computations make use of the detailed shape of the dynamic acceptance and the position-dependent momentum acceptance. Comparisons are made to simpler methods for the Advanced Photon Source storage ring and the multi-bend achromat upgrade lattice. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA008 | |
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| MOPMA009 | Improvements in Modeling of Collective Effects in ELEGANT | 549 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. ELEGANT has long had the ability to model collective effects in various ways, including beam-driven cavity modes, short-range wakes, and coherent synchrotron radiation. Recently, we made improvements specifically targeting simulations that require multiple bunches in storage rings. The ability to simulate long-range, non-resonant wakes was added, which can be used for example to study the effect of the resistive wall wake and multibunch instabilities. We also improved the implementation of short-range and resonant wakes to make them more efficient for multibunch simulations. Finally, improvements in the parallel efficiency were made that allow taking advantage of larger parallel resources. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA009 | |
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| MOPMA010 | Commissioning Simulations for the APS Upgrade Lattice | 553 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. A hybrid seven-bend-achromat lattice has been proposed for the APS upgrade that will feature very strong focusing elements and relatively small vacuum chamber. Achieving design lattice parameters during commissioning will need to be accomplished in a short period of time to minimize dark time for APS users. We describe here start-to-end simulation of the machine commissioning beginning from first-turn trajectory correction, performing orbit and lattice correction, and finally evaluating nonlinear performance of the corrected lattice in terms of dynamic aperture and lifetime. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA010 | |
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| MOPMA011 | Evaluation of Power Supply and Alignment Tolerances for the Advanced Photons Source Upgrade | 556 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The hybrid seven-bend-achromat lattice that has been proposed for the Advanced Photon Source upgrade will feature very strong focusing elements and will provide an electron beam with very low emittance. In order to be able to maintain stable operation, very tight tolerances are required for various types of errors. Here we describe evaluation of the effects of various errors including magnet power supplies, alignment, and vibration. Based on this analysis, we determine short- and long-term stability requirements |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA011 | |
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| MOPMA012 | Intra-Beam and Touschek Scattering Computations for Beam with Non-Gaussian Longitudinal Distributions | 559 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 Both intra-beam scattering (IBS) and the Touschek effect become prominent for multi-bend-achromat- (MBA-) based ultra-low-emittance storage rings. To mitigate the transverse emittance degradation and obtain a reasonably long beam lifetime, a higher harmonic rf cavity (HHC) is often proposed to lengthen the bunch. The use of such a cavity results in a non-gaussian longitudinal distribution. However, common methods for computing IBS and Touschek scattering assume Gaussian distributions. Modifications have been made to several simulation codes that are part of the {\tt elegant} toolkit to allow these computations for arbitrary longitudinal distributions. After describing these modifications, we review the results of detailed simulations for the proposed hybrid seven-bend-achromat (H7BA) upgrade lattice for the Advanced Photon Source. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA012 | |
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| MOPMA013 | Experience with Round Beam Operation at the Advanced Photon Source | 562 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 Very short Touschek lifetime becomes a common issue for next-generation ultra-low emittance storage ring light sources. In order to reach a longer beam lifetime, such a machine often requires operating with a vertical-to-horizontal emittance ratio close to an unity, i.e. a ‘‘round beam''. In tests at the APS storage ring, we determined how a round beam can be reached experimentally. Some general issues, such as beam injection, optics measurement and corrections, and orbit correction have been tested also. To demonstrate that a round beam was achieved, the beam size ratio is calibrated using beam lifetime measurement. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA013 | |
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| MOPMA014 | Design of Superconducting CW linac for PIP-II | 565 |
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| Proton Improvement Plan (PIP) -II is a proposed roadmap to upgrade existing proton accelerator complex at Fermilab. It is primarily based on construction of superconducting (SC) linear accelerator (linac) that would be capable to operate in continuous wave (CW) mode. This paper will present reference design of SC linac and discuss motivations and requirements resulting in this layout and beam optics. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA014 | |
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| MOPMA015 | Applications of an MPI Enhanced Simulated Annealing Algorithm on nuSTORM and 6D Muon Cooling | 568 |
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| The nuSTORM decay ring is a compact racetrack storage ring with a circumference ∼ 480 m using large aperture (∅=60 cm) magnets. The design goal of the ring is to achieve a momentum acceptance of 3.8±10\% GeV/c and a phase space acceptance of 2000 μm·rad. The design has many challenges because the acceptance will be affected by many nonlinearity terms with large particle emittance and/or large momentum offset. In this paper, we present the application of a meta-heuristic optimization algorithm to the sextupole correction in the ring. The algorithm is capable of finding a balanced compromise among corrections of the nonlinearity terms, and finding the largest acceptance. This technique can be applied to the design of similar storage rings that store beams with wide transverse phase space and momentum spectra. We also present the recent study on the application of this algorithm to a part of the 6D muon cooling channel. The technique and the cooling concept will be applied to design a cooling channel for the extracted muon beam at nuSTORM in the future study. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA015 | |
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| MOPMA016 | Coupler RF Kick in the Input 1.3 GHz Accelerating Cavity of the LCLS-II Linac | 571 |
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| Main and HOM couplers break the cavity axial symmetry, distort RF field and, thus, create a transverse kick, even for a particle moving along the cavity axes. Dependence of a kick on the RF phase causes a beam emittance dilution and degrade the FEL radiation quality. The transverse kick is most dangerous for a beam passing through the first accelerating structure of a linac, where particles energy and their relativistic mass are low. In the paper we analyze the coupler RF kick in the first accelerating structure of the LCSL-II linac. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA016 | |
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| MOPMA017 | Numerical simulations of transverse modes in Gaussian bunches with space charge | 575 |
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| The transverse modes and the intrinsic Landau damping in Gaussian bunched beams with space charge are numerically investigated. The evolution of the phase space density is calculated with the Synergia accelerator modeling package and analyzed with Dynamic Mode Decomposition (DMD) method. DMD is a relatively new technique used to calculate mode dynamics in both linear and nonlinear systems. The properties of the first three space charge modes, including their shape, damping rates and tune shifts are calculated over the entire range of the space charge interaction. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA017 | |
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| MOPMA018 | Simulation of Multipacting in SC Low Beta Cavities at FNAL | 579 |
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| Proton Improvement Plan-II at Fermilab is a plan for improvements to the accelerator complex aimed at providing a beam power capability of at least 1 MW on target at the initiation of LBNE (Long Base Neutrino Experiment) operations. The central element of the PIP-II is a new 800 MeV superconducting linac, injecting into the existing Booster. Multipacting affects superconducting RF cavities in the entire range from high energy elliptical cavities to coaxial resonators for low-beta applications. This work is focused on multipacting study in the low-beta 325 MHz spoke cavities; namely SSR1 and SSR2, which are especially susceptible to the phenomena. The extensive simulations of multipacting in the cavities with updated material properties and comparison of the results with experimental data helped us to improve overall reliability and accuracy of these simulations. Our practical approach to the simulations is described in details. For SSR2, which has a high multipacting barrier right at the operating power level, some changes of the cavity shape to mitigate this harmful phenomenon are proposed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA018 | |
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| MOPMA019 | Simulations of the Fermilab Recycler for Losses and Collimation | 582 |
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| Fermilab has recently completed an upgrade to the com- plex with the goal of delivering 700 kW of beam power as 120 GeV protons to the NuMI target. A major part of boost- ing beam power is to shorten the beam cycle by accumulating up to 12 bunches of 0.5 × 10 11 protons in the Recycler ring through slip-stacking during the Main Injector ramp. This introduces much higher intensities into the Recycler than it has had before. Meeting radiation safety requirements with high intensity operations requires understanding the ef- fects of space charge induced tune spreads and resulting halo formation, and aperture restrictions in the real machine to de- velop a collimation strategy. We report on initial simulations of slip-stacking in the Recycler performed with Synergia. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA019 | |
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| MOPMA020 | Measurement and Correction of the Fermilab Booster Optics with LOCO | 586 |
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Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. The optics of the original Booster lacked the ability for full optics correction and it was not until 2009 when new optics corrector packages were installed between gradient magnets that this ability became available. The optics correction method that is chosen is called LOCO (Linear Optics from Closed Orbits) that measures the orbit response from every beam position monitor (BPM) in the ring from every kick of every dipole corrector. The large data set collected allows LOCO to not only calculate the quadrupole and skew quadrupole currents that both reduces beta beatings and corrects coupling, it also finds the dipole kicker strengths, BPM calibrations and their tilts by minimizing the difference between the measured and ideal orbit response of the beam. The corrected optics have been loaded into Booster and it is currently being tested to be eventually used in normal operations. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA020 | |
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| MOPMA022 | Numerical Analysis of Parasitic Crossing Compensation with Wires in DAΦNE | 589 |
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Funding: This work was partially supported by the US LARP. The HiLumi LHC Design Study is partially funded by the European Commission Grant Agreement 284404. Current bearing wire compensators were successfully used in the 2005-2006 running of the DAΦNE collider to mitigate the detrimental effects of parasitic beam-beam interactions. A marked improvement of the positron beam lifetime was observed in machine operation with the KLOE detector. In view of the possible application of wire beam-beam compensators for the High Luminosity LHC upgrade, we revisit the DAΦNE experiments. We use an improved model of the accelerator with the goal to validate the modern simulation tools and provide valuable input for the LHC upgrade project. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA022 | |
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| MOPMA024 | A Parallel Particle-Particle, Particle-Mesh Solver for Studying Coulomb Collisions in the Code IMPACT-T | 593 |
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Funding: This work is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. In intense charged-particle beams, the presence of Coulomb collisions can result in growth of the beam slice energy spread and emittance that cannot be captured correctly using traditional particle-in-cell codes. Particle-particle, particle-mesh solvers take a hybrid approach, combining features of N-body and particle-in-cell solvers, to correctly capture the effect of short-range particle interactions with less computing time than direct N-body solvers. We describe the implementation and benchmarking of such a solver in the code IMPACT-T for beam dynamics applications. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA024 | |
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| MOPMA025 | CSR Induced Microbunching Gain Estimation including Transient Effects in Transport and Recirculation Arcs | 596 |
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Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The coherent synchrotron radiation (CSR) of a high brightness electron beam traversing a series of dipoles, such as transport or recirculation arcs, may result in the microbunching instability (μBI). To accurately quantify the direct consequence of this effect, we further extend our previously developed semi-analytical simulation [C. -Y. Tsai et al., FEL Conference 2014 (THP022)] to include more relevant coherent radiation models than the steady-state free-space CSR impedance, such as the entrance and exit transient effects, which derive from upstream beam entering to and exiting from individual dipoles and propagating across the elements to downstream straight sections. Then we semi-analytically solve the linearized Vlasov equation for the amplification factor. The resultant gain functions and spectra for our example lattices are presented and compared with particle tracking simulation. Some underlying physics with inclusion of these effects are also discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA025 | |
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| MOPMA026 | Proposed Cavity for Reduced Slip-Stacking Loss | 600 |
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| This paper employs a novel dynamical mechanism to improve the performance of slip-stacking. Slip-stacking in an accumulation technique used at Fermilab since 2004 which nearly double the proton intensity. During slip-stacking, the Recycler or the Main Injector stores two particles beams that spatially overlap but have different momenta. The two particle beams are longitudinally focused by two 53 MHz 100 kV RF cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV RF cavity, with a frequency at the double the average of the upper and lower main RF frequencies. In simulation, we find the proposed RF cavity significantly enhances the stable bucket area and reduces slip-stacking losses under reasonable injection scenarios. We quantify and map the stability of the parameter space for any accelerator implementing slip-stacking with the addition of a harmonic RF cavity. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA026 | |
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| MOPMA027 | Electron Cloud Measurements in Fermilab Main Injector and Recycler | 604 |
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| This conference paper presents a series of electron cloud measurements in the Fermilab Main Injector and Recycler. A new instability was observed in the Recycler in July 2014 that generates a fast transverse excitation in the first high intensity batch to be injected. Microwave measurements of electron cloud in the Recycler show a corresponding dependence on the batch injection pattern. These electron cloud measurements are compared to those made with a retarding field analyzer (RFA) installed in a field-free region of the Recycler in November. RFAs are also used in the Main Injector to evaluate the performance of beampipe coatings for the mitigation of electron cloud. Contamination from an unexpected vacuum leak revealed a potential vulnerability in the amorphous carbon beampipe coating. The diamond-like carbon coating, in contrast, reduced the electron cloud signal to 1\% of that measured in uncoated stainless steel beampipe. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA027 | |
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| MOPMA028 | Chromaticity and Dispersion in Nonlinear Integrable Optics | 608 |
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Funding: This material is based upon work sup- ported by the U.S. Department of Energy, Office of Sci- ence, Office of High Energy Physics under Award Num- ber DE-SC0011340. Proton accumulator rings and other circular hadron accelerators are susceptible to intensity- driven parametric instabilities because the zero-current charged particle dynamics are characterized by a single tune. Landau damping can suppress these instabilities, which requires energy spread in the beam or introducing nonlinear magnets such as octupoles. However, this approach reduces dynamic aperture. Nonlinear integrable optics can suppress parametric instabilities independent of energy spread in the distribution, while preserving the dynamic aperture. This novel approach promises to reduce particle losses and enable order-of-magnitude increases in beam intensity. In this paper we present results, obtained using the Lie operator formalism, on how chromaticity and dispersion affect particle orbits in integrable optics. We conclude that chromaticity in general breaks the integrability, unless the vertical and horizontal chromaticities are equal. Because of this, the chromaticity correcting magnets can be weaker and fewer correcting magnet families are required, thus minimizing the impact on dynamic aperture. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA028 | |
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| MOPMA029 | Experiences Simulating Nonlinear Integrable Optics | 611 |
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Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0011340. With increasing interest in the nonlinear integrable optics, it is important that early experiences with simulating the lattices be shared to save time and point out potential difficulties in the simulations. We present here some details of simulating the nonlinear integrable lattices. We discuss correctly implementing and testing the elliptic element kicks, and the limits of the thin lens approximation. We also discuss generating a properly matched bunch in the transverse phase space, and how to analyze the resulting computational data from simulations. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA029 | |
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| MOPMA030 | Multisymplectic Integrators for Accelerator Tracking Codes | 614 |
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| It has been long understood that long time single particle tracking requires symplectic integrators to keep the simulations stable. In contrast, space charge has been added to tracking codes without much regard for this. Indeed, multisymplectic integrators are a promising new field which may lead to more stable and accurate simulations of intense beams. We present here the basic concept, through a spectral electrostatic field solve which is suitable for adapting into existing tracking codes. We also discuss the limitations of current algorithms, and suggest directions for future development for the next generations of high intensity accelerators. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA030 | |
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| MOPMA031 | Simulations of Diamond Detectors with Schottky Contacts | 617 |
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Funding: This work is supported by the US DOE Office of Science, department of Basic Energy Sciences, grant numbers DE-SC0006246 and DE-SC0007577. We present simulations of semiconductor devices using the code VSim (formerly Vorpal). The 3D simulations involve the movement and scattering of electrons and holes in the semiconductor, voltages which may be applied to external contacts, and self-consistent electrostatic fields inside the device. Particles may experience a Schottky barrier when moving between the semiconductor and a metal contact. Example devices include MOSFETs as well as a diamond X-ray detector. Our code VSim includes scattering models for GaAs and diamond, and runs in parallel on thousands of processors. We compare our simulation results with experimental results from a prototype diamond X-ray detector. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA031 | |
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| MOPMA033 | Modeling Electron Emission and Surface Effects from Diamond Cathodes | 620 |
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Funding: We are grateful to the U.S. DoE Office of Basic Energy Sciences for supporting this work under grants DE-SC0006246 and DE-SC0007577. We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional (3D) simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 to 17 MV/m along the [100] direction. The simulation results were compared to experimental data when using different emission models, band bending effects, and surface-dependent electron affinity. Simulations using surface patches with different levels of hydrogenation lead to the closest agreement with the experimental data. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA033 | |
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| MOPMA035 | Current Status of the GPU-accelerated ELEGANT | 623 |
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Funding: Work supported by the DOE Office of Science, Office of BES grant No. DE-SC0004585, and by Tech-X Corporation. This research used resources of the OLCF, supported under Contract DE-AC05-00OR22725. Efficient implementation of general-purpose particle tracking on GPUs can bring significant performance benefits to large-scale tracking simulations and direct (tracking-based) accelerator optimization techniques. This presentation is an update on the current status of our work on accelerating Argonne National Lab’s particle accelerator simulation code ELEGANT [*] using CUDA-enabled GPU. We summarize the performance of beamline elements ported to GPU, and discuss optimization techniques for some important collective effects kernels. We also outline briefly our testing and code validation infrastructure within ELEGANT and present the latest results of scaling studies with realistic lattices of the GPU-accelerated version of the code. * M. Borland, ‘‘elegant: A Flexible SDDS-compliant Code for Accelerator Simulation", APS LS-287, September 2000 |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA035 | |
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| MOPMA037 | Electron Cloud Buildup and Dissipation Models For PIP-II | 626 |
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Funding: This work was performed under the auspices of the Department of Energy as part of the ComPASS SCiDAC-2 project (DE-FC02-07ER41499), and the SCiDAC-3 project (DE-SC0008920). Buildup of electron plasmas in accelerator cavities can cause beam degradation and limit performance in high-intensity circular particle accelerators. This is especially important in machines such as the LHC, and PIP-II, where mitigation techniques such as beam scrubbing in order to decrease the SEY are expensive and time consuming. Modeling of electron cloud buildup and dissipation can provide understanding as to the potential negative effects of electron clouds on beam properties, as well as estimates of the mitigation required to maintain accelerator performance and beam quality as accelerators move to higher intensity configurations. We report here on simulations of electron cloud buildup and dissipation for geometry, beam and magnetic field configurations describing the Recycler at Fermilab. We perform electrostatic simulations in 3D with VSim PIC, including the effects of space charge and secondary electrons. We quantify the expected survival rate of electrons in these conditions, and argue that improvements in reducing the SEY is unlikely to mitigate the electron cloud effects. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA037 | |
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| MOPMA039 | Secondary Electron Yield Measurement and Electron Cloud Simulation at Fermilab | 629 |
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Funding: This work was funded by the National Science Foundation under the grant no. 1205811. Fermilab Main Injector is upgrading the accelerator to double the beam intensity from 24·1012 protons to 48·1012 protons, which brings the accelerator into a regime where electron cloud effects may limit the accelerator performance. In fact, an instability that could be caused by electron cloud effects has already been observed in the Recycler. Secondary Electron Yield (SEY) is an important property of the vacuum chamber material that has great influence on the process of building up free electrons. The Main Injector of the Fermilab accelerator complex offers the opportunity to measure SEY and conditioning effects in the environment of a running accelerator, since samples of these materials are located at the beampipe wall. The SEY of stainless steel (SS316L) and TiN coated SS316L in the proximity of the proton beam were measured and compared. A series of simulation studies of electron cloud build up were done for the Main Injector and Recycler using the code POSINST. Parametric studies were done to determine the maximum electron density vs. peak SEY at different beam intensities in the Fermilab Main Injector. Threshold simulations of electron cloud density verus SEY were extended from Main Injector to include the Recycler Ring. It was found that the electron cloud density around the beam depends on bunch location within the bunch train. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA039 | |
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| MOPMA040 | Analysis of Beam Transverse Instabilities at Fermilab | 633 |
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| The transverse beam dynamics in Fermilab Recycler ring has been analyzed using SCHARGEV Vlasov solver. In the first part of paper we discuss how SCHARGEV analyses collective instabilities for Gaussian bunch with strong space charge in resistive impedance environment. In the second part the bunched beam dynamics is studied depending on head-tail phase and damper gain. An example for Fermilab Recycler is presented. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA040 | |
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| MOPMA041 | Experimental Observation of Head-Tail Modes for Fermilab Booster | 636 |
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| The Fermilab Booster is known to suffer from beam transverse instabilities. An experimental attempt of head-tail modes extraction from the stable beam motion by periodic excitement of betatron motion has been performed. The shapes of head-tail modes have been successfully obtained while eigenfrequencies separation from the betatron tune were too small to be resolved. The qualitative agreement between the theory and an experimental data has been demonstrated. This is an important step towards the understanding of general theory of collective instabilities for strong space charge case, which is a rather typical case for hadron machines. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA041 | |
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| MOPMA043 | Longitudinal Bunch Shaping at Picosecond Scales using Alpha-BBO Crystals at the Advanced Superconducting Test Accelerator | 643 |
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Funding: This works is supported by the University Research Association, Inc. Operated by the Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy The Integrable Optics Test Accelerator (IOTA) electron injector at Fermilab will enable a broad range of experiments at a national laboratory in order to study and develop solutions to the limitations that prevent the propagation of high intensity beams at picosecond lengths. One of the most significant complications towards increasing short-beam intensity is space-charge, especially in the vicinity of the gun. A few applications that require a longitudinally shaped electron beam at high intensities are for, the generation of THz waves and dielectric wakefields, each of which will encounter the effects of longitudinal space-charge. This paper investigates the effects of longitudinal space-charge on alpha-BBO UV laser shaped electron bunches in the vicinity of the 1½cell 1.3 GHz cylindrically symmetric RF photocathode gun. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA043 | |
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| MOPMA044 | Barrier Shock Compression with Longitudinal Space Charge | 646 |
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Funding: This work is supported by the US Dept. of Energy, Office of High Energy Physics. Synchrotrons and storage rings routinely employ RF barrier buckets as a means of accumulating charge to increase the peak intensity and preserve longitudinal emittance while minimizing emittance growth [1-3]. This was shown in the main injector and recycler at Fermilab as well as the SIS-18 at GSI Helmholtz center for heavy ion research. The RF cavities typically used are ferrite loaded magnetic alloys with low Q to maximize bandwidth and generate single pulses, either as delta functions, triangular or half/full period sine waves. The University of Maryland Electron Ring (UMER) group is studying a novel scheme of bunch compression in the presence of longitudinal space charge. It has been analytically shown through 1-D computations that the presence of space-charge considerably improves the efficiency of the barrier compression by taking advantage of the shock-front that launches when the barrier moves into a space-charge dominated beam. In this paper, we summarize the initial results of the study. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA044 | |
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| MOPMA045 | Conceptual Difficulties of a Thermodynamics Description of Charged-Particle Beams | 649 |
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Funding: This work is funded by the US Dept. of Energy We review the existing phenomenological theories of emittance growth with and without entropy terms and re-examine the condition for thermal equipartitioning in an unbunched charged-particle beam. The model incorporates linear space charge and a uniform-focusing lattice. Because of non-extensitivity of the transverse ("thermal") energy and the absence of a classical heat bath, we conclude that a rigorous classical thermodynamics treatment of charged-particle beams is not possible. In particular, the postulated relationships between the rms emittance and temperature and entropy must be qualified. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA045 | |
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| MOPMA046 | Simulations and experiments in Support of Octupole Lattice Studies at the University of Maryland Electron Ring | 653 |
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Funding: This material is based on work supported by the NSF Graduate Research Fellowship and the NSF Accelerator Science Program We present plans for a nonlinear lattice at the University of Maryland Electron Ring (UMER). Theory predicts that a strong nonlinear lattice can limit resonant behavior without reducing dynamic aperture if the nonlinear fields preserve integrability or quasi-integrability. We discuss plans for a quasi-integrable octupole lattice, based on the work of Danilov and Nagaitsev.* We use Elegant and the WARP PIC code to estimate the octupole-induced tune spread. We discuss improvements to the ring in support of octupole lattice experiments, including generation and detection of emittance-dominated, negligible space charge beams. * V. Danilov, S. Nagaitsev, Phys. Rev. STAB 13, 084002 (2010). |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA046 | |
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| MOPMA047 | Nonlinear Beam Dynamics Studies of the Next Generation Strong Focusing Cyclotrons as Compact High Brightness, Low Emittance Drivers | 656 |
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Funding: Work is partially supported by grants from the State of Texas (ASE) & the Michelle foundation. The Strong Focusing Cyclotron development at Texas A&M University has evolved from stacks of cyclotrons to a single layer high brightness, low emittance to produce greater than 10 mA of proton beam to a desired target at 800 MeV. The latest design has a major geometric design optimization of strong focusing quadrupoles and a modified algorithm of high gradient cavities to address the small turn separation, and interaction of radially neighboring bunches and reduced the number of turns necessary to reach the desired final energy under control conditions. In this paper, we present the new design, physics of nonlinear synchrobetratron coupling, mνh+nνv=p causing beam blow-up in other form of cyclotrons and how we have resolved it. The cavity beam loading and space charge effects of multi turns at low energies to reduce losses are discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA047 | |
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| MOPMA049 | Development of a Single-pass Amplifier for an Optical Stochastic Cooling Proof-of-principle Experiment at Fermilab's IOTA facility | 659 |
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| Optical stochastic cooling (OSC) is a method of beam cooling which is expected to provide cooling rates orders of magnitude larger than ordinary stochastic cooling. Light from an undulator (the pickup) is amplified and fed back onto the particle beam via another undulator (the kicker). Fermilab is currently exploring a possible proof-of-principle experiment of the OSC at the integrable-optics test accelerator (IOTA) ring. To implement effective OSC a good correction of phase distortions in the entire band of the optical amplifier is required. In this contribution we present progress in experimental characterization of phase distortions associated to a Titanium Sapphire crystal laser-gain medium (a possible candidate gain medium for the OSC experiment to be performed at IOTA). We also discuss a possible option for a mid-IR amplifier. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA049 | |
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| MOPMA050 | Smooth Fast Multipole Method for Space Charge Tracking: An Alternate to Particle-In-Cell | 663 |
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The fast multipole method (FMM) algorithm was developed by Greengard and Rokhlin in 1987 *. As one of the top ten algorithms of the 20th century, it has been applied in a wide range of fields. The FMM complexity is O(N), where N is the number of articles, allowing for large-scale simulations. However, it includes all the two-body collisional forces, in contrast to other methods such as the popular particle in-cell (PIC) methods. While collisionality can be very important, many applications require only the mean field effects. PIC is frequently used in this regime. Due to recent concerns of unphysical effects of grids, interpolation and other approximations in PIC codes, an alternative based on different underlying assumptions would prove enlightening. For these cases, a smoothed or softened FMM using a Plummer-like smoothing parameter holds much promise. Unfortunately, the original FMM based on analytic expansions of the 1/r-like potentials does not allow for Plummer softening. We present our new soft-FMM employing differential algebras (DA) to obtain the modified expansions. We also compare the performance of the smoothed DA-FMM with examples from PIC simulations.
* L. Greengard and V. Rokhlin. “A fast algorithm for particle simulations". |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA050 | |
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| MOPMA051 | Generation of Modulated Bunch Using a Masked Chicane for Beam-Driven Acceleration Experiments at ASTA | 666 |
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Funding: This work was supported by the DOE contract No. DEAC02-07CH11359 to the Fermi Research Alliance LLC. Longitudinal density modulations on electron beams can improve machine performance of beam-driven accelerators and FELs with resonance beam-wave coupling *. The sub-ps beam modulation has been studied with a masked chicane ** *** by the analytic model and simulations with the beam parameters of the Advanced Superconducting Test Accelerator (ASTA) in Fermilab. With the nominal 50 MeV chicane parameters and 3 ps bunch length, the analytic model showed that a slit-mask with slit period 900 um and aperture width 300 μm generates about 100-um modulation periodicity with 2.4% correlated energy spread. With the designed slit mask and a 3 ps bunch, particle-in-cell simulations (CST-PS), including nonlinear energy distributions, space charge force, and coherent synchrotron radiation (CSR) effect, also result in ~ 100 um of longitudinal modulation. The beam modulation has been extensively examined with three different beam conditions, 0.25, 1 , and 3.2 nC, by extended 3D tracking simulations (Elegant). The modulated bunch generation will be tested by a slit-mask installed at the chicane of the ASTA 50-MeV-injector beamline for beam-driven acceleration experiments. * E. Kallos, Southern California 2008 ** D. C. Nguyen, B. E. Carlston, NIMA 375, 597 (1996) *** P. Muggli, V. Yakimenko, M. Babzien, E. Kallos, and K. P. Kusche, PRL 101, 054801 (2008) |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA051 | |
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| MOPMA052 | Implementation of Quadrupole-scan Emittance Measurement at Fermilab's Advanced Superconducting Test Accelerator (ASTA) | 669 |
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Funding: This work was supported by the DOE contract No. DEAC02-07CH11359 to the Fermi Research Alliance LLC. Transverse-emittance measurements based on the quadrupole-scan technique * ** ***, have been widely used to characterize the beam phase-space parameters in linear accelerators. This paper discusses the implementation of the technique at the Advanced Superconducting Test Accelerator (ASTA) at Fermilab. We plan on deploying a flexible implementation that permits an operator to select the quadrupole associated analysing screen to measure the beam emittance. Our implementation utilizes Python scripts combined with Fermilab’s control system ACNet and ELEGANT quadrupole-scan method at 50 MeV given the range of operating charge (20 pC to 3.2 nC) available at ASTA. Some preliminary measurements will also be presented. * B.E. Carlsten, et al, Nucl. Instrum. Methods Phys. Res. Sect. A 331, 791 (1993) ** C. Eckman et al, IPAC 2012 *** K. Poorrezaei, et al, Phys. Rev. ST-AB 16, 082801 (2013) |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA052 | |
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| MOPMA053 | Characterizing Betatron Tune Knobs on Duke Storage Ring | 672 |
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Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. The Duke electron storage ring is a dedicated driver for oscillator Free-Electron Lasers (FELs). A 34-m long straight section of the storage ring can host up to four FEL wigglers in several different configurations. The storage ring magnetic lattice has designed with great flexibility to enable the operation with different wiggler configurations and at different electron beam energies. To realize smooth storage ring operation with various electron beam and wiggler parameters, a sophisticated lattice feedforward compensation scheme and a set of betatron tune knobs have been designed, developed and implemented in the controls system. The built-in compensation and tune knobs have demonstrated to be highly useful to allow transparent operation of the storage ring. To fully understand the effectiveness of the lattice tuning scheme, experiments have been carried to characterize the betatron tune knobs. In this paper, we will outline the measurement techniques and procedures, report experimental results, and make important observations on the usefulness of developing an advanced light source storage ring using accurate knowledge of individual magnets with high-quality measured fields. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA053 | |
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| MOPMA054 | Start-to-end Simulation of Free-electron Lasers | 675 |
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| Start-to-end (S2E) modeling of free-electron lasers (FELs) normally requires the use of multiple codes to correctly capture the physics in each region of the machine. Codes such as PARMELA, IMPACT-T or MICHELLE, for instance, may be used to simulate the injector. From there the linac and transport line may be handled by codes such as DIMAD, ELEGANT or IMPACT-Z. Finally, at the FEL a wiggler interaction code such as GENESIS, GINGER, or MINERVA must be used. These codes may be optimized to work with a wide range in magnitude of macro-particle numbers (from 104-108 in different codes) and have different input formats. It is therefore necessary to have translator codes to provide a bridge between each section. It is essential that these translators be able to preserve the statistical properties of the bunch while raising or lowering the number of macro-particles used between codes. In this work we show a suite of such translators designed to facilitate S2E simulations of an FEL with a new wiggler code, MINERVA, and use these codes to provide benchmarking of MINERVA against other common wiggler simulation codes. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA054 | |
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| MOPMA055 | MuSim, a Graphical User Interface for Multiple Simulation Programs | 678 |
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| MuSim is a new user-friendly program designed to interface to many different particle simulation codes, regardless of their data formats or geometry descriptions. It presents the user with a compelling graphical user interface that includes a flexible 3-D view of the simulated world plus powerful editing and drag-and-drop capabilities. All aspects of the design can be parametrized so that parameter scans and optimizations are easy. It is simple to create plots and display events in the 3-D viewer (with a slider to vary the transparency of solids), allowing for an effortless comparison of different simulation codes. Simulation codes: G4beamline, MAD-X, and MCNP; more coming. Many accelerator design tools and beam optics codes were written long ago, with primitive user interfaces by today’s standards. MuSim is specifically designed to make it easy to interface to such codes, providing a common user experience for all, and permitting the construction and exploration of models with very little overhead. For today’s technology-driven students, graphical interfaces meet their expectations far better than text-based tools, and education in accelerator physics is one of our primary goals. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA055 | |
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| MOPMA056 | Measurement and Modeling of Single Bunch Wake Field Effects in CESR | 681 |
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Funding: Work supported by NSF PHY-1416318 and NSF DMR 1332208. This research used the National Energy Research Scientific Computing Center, which is supported by DOE Contract No. DE-AC02-05CH11231. Short-range wake fields have been incorporated into a Bmad-based particle tracking code in order to assess their contribution to current-dependent emittance growth, tune shift, and single bunch instabilities. The wakes are computed for CESR vacuum components using the T3P modeling software. Simulation results are compared with measurements of bunch length, vertical beam size, and coherent tune shift. Additionally, we use insertable scrapers to vary the transverse wake and measure the effect on the beam. We show that a vertical emittance increase at high current may be due to a transverse monopole wake, originating in the lump pump slots throughout CESR. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA056 | |
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| MOPMA057 | Space Charge Neutralization of 750 keV Proton Beam in LANSCE Injector Line | 685 |
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Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396 The 750-keV low-energy beam transport of the Los Alamos Neutron Science Center (LANSCE) linac consists of two independent beam lines for simultaneous injection of H+ and H− beams into the linear accelerator. Space charge effects play an important role in the beam transport therein. A series of experiments were performed to determine the level of proton beam space charge neutralization by residual gas ionization, and time required for neutralization. Study was performed as emittance scans between pair of emittance measurement stations. The value of compensated space charge was determined through comparison of results of measurements and simulations using macroparticle method and envelope code. Obtained results provide new setup for beam tuning in transport beamline. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA057 | |
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| MOPMA058 | Effect of Spherical Aberration on Beam Emittance Growth | 688 |
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Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396 Spherical aberration in axial-symmetric magnetic focusing lenses results in S-shape figure of beam emittance. Filamentation of beam emittance in phase space is a fundamental property of a beam affected by aberrations. Analytical expression for effective beam emittance growth due to spherical aberration as a function of lens aberraion coefficient, initial beam emittance, beam radius, and focal lens of the focusing lens is obtained. Analysis is extended for beam space charge aberrations. Analytical results are confirmed by numerical calculations. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA058 | |
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| MOPMA059 | Lorentz boosted frame simulation of Laser wakefield acceleration using hybrid Yee-fft solver in quasi-3d geometry | 691 |
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| We present results from a preliminary study on modeling Laser wakefield acceleration (LWFA) with OSIRIS in a Lorentz boosted frame using a quasi-3D algorithm. In the quasi-3D algorithm, the fields and currents are expanded into azimuthal harmonics and only a limited number of harmonics are kept. Field equations in (r,z) space are solved for a desired number of harmonics in φ. To suppress the numerical Cerenkov instability (NCI) that inevitably arises due to the relativistic plasma drift in the simulation, we use a hybrid Yee-FFT solver in which the field equations are solved in (kz, r) space, where \hat{z} is the drifting direction. Preliminary results show that high fidelity LWFA boosted frame simulations can be carried out with no evidence of the NCI. Good agreement is found when comparing LWFA boosted frame simulations in the full 3D geometry against those in the quasi-3D geometry. In addition, we discuss how the moving window can be combined with the hybrid Yee-FFT solver to further speed up the simulation. The results indicate that unprecedented speed ups for LWFA simulations can be achieved when combining the Lorentz boosted frame technique, the quasi-3D algorithm, and a moving window. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA059 | |
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| MOPMA060 | Impedance Measurement for the SPEAR3 Storage Ring | 694 |
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| We studied the transverse impedance of the SPEAR3 storage ring with tune shift vs. beam intensity, head-tail instability and transverse mode coupling instability measurements. By taking measurements under different machine conditions, we probed the frequency dependence of the impedance, from which an impedance model was built. This model is consistent with instability measurements and previous bunch lengthening results. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA060 | |
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