Keyword: emittance
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MOA2CO04 MICE Operation and Demonstration of Muon Ionization Cooling ion, simulation, optics, cavity 10

• A. Liu
Fermilab, Batavia, Illinois, USA

Funding: DOE, NSF, STFC, INFN, CHEPP and more
The international Muon Ionization Cooling Experiment (MICE) will demonstrate ionization cooling, the only technique that, given the short muon lifetime, can reduce the phase-space volume occupied by a muon beam quickly enough. MICE will demonstrate cooling in two steps. In the first one, Step IV, MICE will study the multiple Coulomb scattering in liquid hydrogen (LH2) and lithium hydride (LiH). A focus coil module will provide focusing on the absorber. The transverse emittance will be measured upstream and downstream of the absorber in two spectrometer solenoids (SS). Magnetic fields generated by two match coils in the SSs allow the beam to be matched into flat-field regions in which the tracking detectors are installed. This paper will present preliminary results and present plans for data taking of MICE Step IV, together with the design of the MICE Cooling Demonstration Step (Step DEMO), which requires addition of RF systems in the current setup.

Slides MOA2CO04 [10.025 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOA2CO04
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MOB3IO01 Commissioning of the Phase-I SuperKEKB B-Factory and Update on the Overall Status ion, electron, vacuum, coupling 32

• Y. Ohnishi, T. Abe, T. Adachi, K. Akai, Y. Arimoto, K. Egawa, Y. Enomoto, J.W. Flanagan, H. Fukuma, Y. Funakoshi, K. Furukawa, N. Iida, H. Iinuma, H. Ikeda, T. Ishibashi, M. Iwasaki, T. Kageyama, H. Kaji, T. Kamitani, T. Kawamoto, S. Kazama, M. Kikuchi, T. Kobayashi, K. Kodama, H. Koiso, M. Masuzawa, T. Mimashi, T. Miura, F. Miyahara, T. Mori, A. Morita, S. Nakamura, T.T. Nakamura, H. Nakayama, T. Natsui, M. Nishiwaki, K. Ohmi, T. Oki, S. Sasaki, M. Satoh, Y. Seimiya, K. Shibata, M. Suetake, Y. Suetsugu, H. Sugimoto, M. Tanaka, M. Tawada, S. Terui, M. Tobiyama, S. Uehara, S. Uno, X. Wang, K. Watanabe, Y. Yano, S.I. Yoshimoto, R. Zhang, D. Zhou, X. Zhou, Z.G. Zong
KEK, Ibaraki, Japan
• M.E. Biagini, M. Boscolo, S. Guiducci
INFN/LNF, Frascati (Roma), Italy
• D. El Khechen
LAL, Orsay, France

The SuperKEKB B-Factory at KEK (Japan), after few years of shutdown for the construction and renovation, has finally come to the Phase-1 commissioning of the LER and HER rings, without the final focus system and the Belle II detector. Vacuum scrubbing, optics tuning and beam related background measurements were performed in this phase. Low emittance tuning techniques have also been applied in order to set up the rings for Phase-2 with colliding beams next year. An update of the final focus system construction, as well as the status of the injection system with the new positron damping ring and high current/low emittance electron gun is also presented.
Slides MOB3IO01 [10.375 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOB3IO01
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TUB1CO02 Operating Synchrotron Light Sources with a High Gain Free Electron Laser ion, FEL, undulator, electron 259

• S. Di Mitri, M. Cornacchia
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

The peak current required by a high gain free electron laser (FEL) is not deemed to be compatible with the multi-bunch filling pattern of synchrotrons. We show that this problem can be overcome by virtue of magnetic bunch length compression in a ring section and that, after lasing, the beam returns to equilibrium conditions without beam quality disruption*. As a consequence of bunch length compression, the peak current stimulates a high gain FEL emission, while the large energy spread makes the beam less sensitive to the FEL heating and to the microwave instability. The beam large energy spread is matched to the FEL energy bandwidth through a transverse gradient undulator. Feasibility of lasing at 25 nm is shown for the Elettra synchrotron light source (SLS) at 1 GeV. Viable scenarios for the upgrade of existing or planned SLSs to the new hybrid insertion devices-plus-FEL operational mode are discussed, while ensuring little impact on the standard beamlines functionality.
* S. Di Mitri and M. Cornacchia, NJP 17 (2015) 113006

Slides TUB1CO02 [2.353 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUB1CO02
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TUB1CO03 ALS-U: A Soft X-Ray Diffraction Limited Light Source ion, undulator, injection, impedance 263

• C. Steier, A. Anders, J.M. Byrd, K. Chow, S. De Santis, R.M. Duarte, J.-Y. Jung, T.H. Luo, H. Nishimura, T. Oliver, J.R. Osborn, H.A. Padmore, G.C. Pappas, S. Persichelli, D. Robin, F. Sannibale, D. Schlueter, C. Sun, C.A. Swenson, M. Venturini, W.L. Waldron, E.J. Wallén, W. Wan, Y.C. Yang
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Improvements in brightness and coherent flux of about two orders of magnitude over operational storage ring based light sources are possible using multi bend achromat lattice designs. These improvements can be implemented as upgrades of existing facilities, like the proposed upgrade of the Advanced Light Source (ALS-U). The upgrade proposal will reuse much of the existing infrastructure, thereby reducing cost and time needed to reach full scientific productivity on a large number of beamlines. We will report on the accelerator design progress as well as the details of the ongoing R+D program.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUB1CO03
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TUB2IO01 Accelerator Physics Challenges in the Design of Multi Bend Achromat Based Storage Rings ion, lattice, storage-ring, injection 278

• M. Borland
ANL, Argonne, Illinois, USA
• R.O. Hettel
SLAC, Menlo Park, California, USA
• S.C. Leemann
MAX IV Laboratory, Lund University, Lund, Sweden
• D. Robin
LBNL, Berkeley, California, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
With the recent success in commissioning of MAX IV, the multi-bend achromat (MBA) lattice has begun to deliver on its promise to usher in a new generation of higher-brightness synchrotron light sources. In this paper, we begin by reviewing the challenges, recent success, and lessons learned of the MAX-IV project. Drawing on these lessons, we then describe the physics challenges in even more ambitious rings and how these can be met. In addition, we touch on engineering issues and choices that are tightly linked with the physics design.

Slides TUB2IO01 [3.723 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUB2IO01
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TUPOA19 50-MeV Run of the IOTA/FAST Electron Accelerator ion, electron, gun, cavity 326

• D.R. Edstrom, C.M. Baffes, C.I. Briegel, D.R. Broemmelsiek, K. Carlson, B.E. Chase, D.J. Crawford, E. Cullerton, J.S. Diamond, N. Eddy, B.J. Fellenz, E.R. Harms, M.J. Kucera, J.R. Leibfritz, A.H. Lumpkin, D.J. Nicklaus, E. Prebys, P.S. Prieto, J. Reid, A.L. Romanov, J. Ruan, J.K. Santucci, T. Sen, V.D. Shiltsev, Y.-M. Shin, G. Stancari, J.C.T. Thangaraj, R.M. Thurman-Keup, A. Valishev, A. Warner, S.J. Wesseln
Fermilab, Batavia, Illinois, USA
• A.T. Green
Northern Illinois Univerity, DeKalb, Illinois, USA
• A. Halavanau, D. Mihalcea, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
• J. Hyun
Sokendai, Ibaraki, Japan
• P. Kobak
BYU-I, Rexburg, USA
• W.D. Rush
KU, Lawrence, Kansas, USA

Funding: Supported by the DOE contract No.DEAC02-07CH11359 to the Fermi Research Alliance LLC.
The low-energy section of the photoinjector-based electron linear accelerator at the Fermilab Accelerator Science & Technology (FAST) facility was recently commissioned to an energy of 50 MeV. This linear accelerator relies primarily upon pulsed SRF acceleration and an optional bunch compressor to produce a stable beam within a large operational regime in terms of bunch charge, total average charge, bunch length, and beam energy. Various instrumentation was used to characterize fundamental properties of the electron beam including the intensity, stability, emittance, and bunch length. While much of this instrumentation was commissioned in a 20 MeV running period prior, some (including a new Martin-Puplett interferometer) was in development or pending installation at that time. All instrumentation has since been recommissioned over the wide operational range of beam energies up to 50 MeV, intensities up to 4 nC/pulse, and bunch structures from ~1 ps to more than 50 ps in length.

Poster TUPOA19 [4.636 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA19
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TUPOA46 Development of a Python-Based Emittance Calculator at Fermilab Science & Technology (FAST) Facility ion, quadrupole, experiment, solenoid 376

• A.T. Green
Northern Illinois Univerity, DeKalb, Illinois, USA
• Y.-M. Shin
Fermilab, Batavia, Illinois, USA
• Y.-M. Shin
Northern Illinois University, DeKalb, Illinois, USA

Beam emittance is an important characteristic which helps to describe a charged particle beam. In linear accelerators (linac), it is critical to characterize the beam phase space parameters and, in particular, to precisely measure transverse beam emittance. The quadrupole scan (quad-scan) is a well established technique used to characterize transverse beam parameters in four-dimensional phase space. Quad-scans are very time consuming and off-line analysis is needed to extrapolate the beam phase space parameters. We have developed a computational algorithm with Python scripts to automatically estimate beam parameters, in particular beam emittance, using the quadrupole scan technique in the electron linac of Fermilab Accelerator Science and Technology (FAST) facility. These Python scripts have decreased the time it takes to perform a single quad scan from a few hours to a few minutes. From the experimental data, the emittance calculator quickly delivers various results including: transverse emittance, Courant-Snyder parameters, and Beam Size (squared) vs Quadrupole field strength plots, among others.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA46
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TUPOA48 A High-Level Python Interface to the Fermilab ACNET Control System ion, quadrupole, controls, interface 383

• P. Piot
Fermilab, Batavia, Illinois, USA
• A. Halavanau
Northern Illinois University, DeKalb, Illinois, USA

This paper discusses the implementation of a PYTHON-based high-level interface to the Fermilab ACNET control system. We will especially present examples of applications which include the interfacing of an ELEGANT beam-dynamics model to assist lattice matching and an automated emittance measurement via the quadrupole-scan method.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA48
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TUPOA58 Minimization of Emittance at the Cornell Electron Storage Ring With Sloppy Models ion, simulation, storage-ring, lattice 402

• W.F. Bergan, A.C. Bartnik, I.V. Bazarov, H. He, D. L. Rubin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
• J.P. Sethna
Cornell University, Ithaca, New York, USA

Funding: DOE DE-SC0013571 NSF DGE-1144153
Our current method to minimize the vertical emittance of the beam at the Cornell Electron Storage Ring (CESR) involves measurement and correction of the dispersion, coupling, and orbit of the beam and lets us reach emittances of 10 pm, but is limited by finite dispersion measurement resolution.* For further improvement in the vertical emittance, we propose using a method based on the theory of sloppy models.** The storage ring lattice permits us to identify the dependence of the dispersion and emittance on our corrector magnets, and taking the singular value decomposition of the dispersion/corrector Jacobian gives us the combinations of these magnets which will be effective knobs for emittance tuning, ordered by singular value. These knobs will permit us to empirically tune the emittance based on direct measurements of the vertical beam size. Simulations show that when starting from a lattice with realistic alignment errors which has been corrected by our existing method to have an emittance of a few pm, this new method will enable us to reduce the emittance to nearly the quantum limit, assuming that vertical dispersion is the primary source of our residual emittance.
* J. Shanks, D.L. Rubin, and D. Sagan, Phys. Rev. ST Accel. Beams 17, 044003 (2014).
** K.S. Brown and J.P. Sethna, Phys. Rev. E 68, 021904 (2003).

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA58
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TUPOA64 Effects of Low Frequency Buncher Field (LFB) Variation on an H Beam Phase-Energy ion, cavity, DTL, bunching 414

• P.K. Roy, Y.K. Batygin
LANL, Los Alamos, New Mexico, USA

Funding: This work supported by the United States Department of Energy under contract DE-AC52-06NA25396
Beam bunching optimization at low energy (750keV) before injecting into a DTL (100MeV) is essential for beam transport, emittance reduction, and focusing on to a target. The LANSCE simultaneously utilizes H+ and H beam (with a timing variation) for many important national security sciences. In addition to quadrupole, several bunchers are utilized in the transport. A technique with pre-bunching at lower frequency and main bunching at higher frequency is utilized for beam injection into the linac. The buncher parameters (voltage and frequency) are well established for operations. However, there is the possibility that the parameters vary with time due to electrical malfunction or adverse tuning during a beam development activity. Some effort is needed to correct the parameters as a non-optimized pre-bunching setup can alter the beam phase space and the nominal beam intensity at a desired location. Here, we examine emittance and phase space distribution variation for H beam due to variation of the low frequency (16 MHz) buncher voltage, which typically operates at 25 kV peak. Beam phase dynamics with buncher voltage variation is also examined using the beam transport code Parmila.
LA-UR-16-23822
LANSCE: Los Alamos Neutron Science Center
DTL: Drift Tube Linac

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA64
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TUB3IO02 Overview of Electron Source Development for High Repetition Rate FEL Facilities ion, gun, cathode, electron 445

• F. Sannibale
LBNL, Berkeley, California, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 'fsannibale@lbl.gov
An increasing science demand for high-repetition rate (MHz-class) FEL facilities, from IR to X-rays, has been pushing institutions and groups around the world to develop proposals addressing such a need, and some of them have been already funded and are under construction. Such facilities require the development of high-brightness high-repetition rate electron guns, and a number of groups worldwide started to develop R&D programs to develop electron guns capable of operating at this challenging regime. Here we describe the approaches and technologies used by the different programs and discuss advantages and challenges for each of them. A review of the present achievements is included, as well as a brief analysis to understand if the present technology performance is sufficient to operate present and future high repetition rate FEL facilities.

Slides TUB3IO02 [7.951 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUB3IO02
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TUPOB16 A Simple Method for Measuring the Electron-Beam Magnetization ion, solenoid, electron, cathode 521

• A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
• G. Ha
POSTECH, Pohang, Kyungbuk, Republic of Korea
• P. Piot
Fermilab, Batavia, Illinois, USA
• J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA
• G. Qiang
TUB, Beijing, People's Republic of China

There are a number of projects that require magnetized beams, such as electron cooling or aiding in flat beam transforms. Here we explore a simple technique to characterize the magnetization, observed through the angular momentum of magnetized beams. These beams are produced through photoemission. The generating drive laser first passes through microlens arrays (fly-eye light condensers) to form a transversely modulated pulse incident on the photocathode surface. The resulting charge distribution is then accelerated from the photocathode. We explore the evolution of the pattern via the relative shearing of the beamlets, providing information about the angular momentum. This method is illustrated through numerical simulations and preliminary measurements carried out at the Argonne Wakefield Accelerator (AWA) facility are presented.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB16
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TUPOB17 Simulations in Support of Wire Beam-Beam Compensation Experiment at the LHC ion, simulation, experiment, optics 525

• A.S. Patapenka
Northern Illinois University, DeKalb, Illinois, USA
• R. De Maria, Y. Papaphilippou
CERN, Geneva, Switzerland
• A. Valishev
Fermilab, Batavia, Illinois, USA

The compensation of long-range beam-beam interaction with current wires is considered as a possible technology for the HL-LHC upgrade project. A demonstration experiment is planned in the present LHC machine starting in 2018. This paper summarizes the tracking studies of long range beam-beam effect compensation in the LHC aimed to aid in planning the demonstration experiment. The impact of wire compensators is demonstrated on the tune footprints, dynamic aperture, beam emittance and beam intensity degradation. The simulations are performed with SIXTRACK code. The symplectic transport map for the wire element, its verification and implementation into the code are also discussed.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB17
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TUPOB25 Unfolding Electron Beam Parameters Using Spot Size Measurement From Magnet Scan ion, electron, target, beam-transport 549

• Y.H. Wu, Y.J. Chen, J. Ellsworth
LLNL, Livermore, California, USA

Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
The Flash X-ray Radiography (FXR) [1] line-ar induction accelerator at Lawrence Livermore National Laboratory produces x-ray bursts for radiographs. The machine is able to produce x-ray spot sizes less than 2mm. Using the spot sizes measured from the magnet scanning, the beam parameters are unfolded by modelling the FXR LINAC with the simulation code AMBER [2] and the envelope code XENV [3]. In this study, the most recent spot size measurement results and techniques used to extract the beam parameters are described. Using the unfolded beam parameters as the initial condition, the backstreaming ions' neutralization factor f = 0.3 is found by comparing the calculated spot sizes with measured spot sizes at the target.

Poster TUPOB25 [0.576 MB]
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TUPOB29 Simulations of Nonlinear Beam Dynamics in the JLEIC Electron Collider Ring ion, sextupole, electron, dynamic-aperture 555

• F. Lin, Y.S. Derbenev, V.S. Morozov, F.C. Pilat, G.H. Wei, Y. Zhang
JLab, Newport News, Virginia, USA
• Y. Cai, Y.M. Nosochkov, M.K. Sullivan
SLAC, Menlo Park, California, USA
• M.-H. Wang

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. Work supported by the US DOE Contract DE-AC02-76SF00515.
The short lengths of colliding bunches in the proposed Jefferson Lab Electron-Ion Collider (JLEIC) allow for small beta-star values at the interaction point (IP) yielding a high luminosity. The strong focusing associated with the small beta-stars results in high natural chromaticities and potentially a beam smear at the IP. Rapid growth of the electron equilibrium emittances and momentum spread with energy further complicates the situation. We investigated nonlinear dynamics correction schemes that overcome these problems and allow for stable beam dynamics and sufficient beam lifetime at the highest electron energy. In this paper, we present and compare tracking simulation results for various schemes considering their emittance contributions.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB29
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TUPOB31 Compensation of Chromaticity in the JLEIC Electron Collider Ring ion, sextupole, electron, dipole 561

• Y.M. Nosochkov, Y. Cai, M.K. Sullivan
SLAC, Menlo Park, California, USA
• Y.S. Derbenev, F. Lin, V.S. Morozov, F.C. Pilat, G.H. Wei, Y. Zhang
JLab, Newport News, Virginia, USA
• M.-H. Wang

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. Work supported by the US DOE Contract DE-AC02-76SF00515.
The Jefferson Lab Electron-Ion Collider (JLEIC) is being designed to achieve a high luminosity of up to 1034 1/(cm2*sec). The latter requires a small beam size at the interaction point demanding a strong final focus (FF) quadrupole system. The strong beam focusing in the FF unavoidably creates a large chromaticity which has to be compensated in order to avoid a severe degradation of momentum acceptance. This has to be done while preserving sufficient dynamic aperture. An additional design requirement for the chromaticity compensation optics in the electron ring is preservation of the low beam emittance. This paper reviews the development and selection of a chromaticity correction scheme for the electron collider ring.

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TUPOB36 Simulation Study on JLEIC High Energy Bunched Electron Cooling ion, electron, simulation, collider 568

• H. Zhang, S.V. Benson, J. Chen, Y.S. Derbenev, R. Li, Y. Roblin, Y. Zhang
JLab, Newport News, Virginia, USA
• H. Huang, L. Luo
ODU, Norfolk, Virginia, USA

Funding: * Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
In the JLab Electron Ion Collider (JLEIC) project the traditional electron cooling technique is used to reduce the ion beam emittance at the booster ring, and to compensate the intrabeam scattering effect and maintain the ion beam emittance during the collision at the collider ring. Different with other electron coolers using DC electron beam, the proposed electron cooler at the JLEIC ion collider ring uses high energy bunched electron beam, provided by an ERL. In this paper, we report some recent simulation study on how the electron cooling rate will be affected by the bunched electron beam properties, such as the correlation between the longitudinal position and momentum, the bunch size, and the Larmor emittance.

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TUPOB44 Final 6d Muon Ionization Cooling Using Strong Focusing Quadrupoles ion, quadrupole, betatron, collider 592

• T.L. Hart, J.G. Acosta, L.M. Cremaldi, S.J. Oliveros, D.J. Summers
UMiss, University, Mississippi, USA
• D.V. Neuffer
Fermilab, Batavia, Illinois, USA

Low emittance muon beam lines and muon colliders are potentially a rich source of BSM physics for future experimenters. A normalized transverse muon emittance of 280 microns has been achieved in simulation with short solenoids and a betatron function of 3 cm. Here we use ICOOL, G4Beamline, and MAD-X to explore using a flat 400 MeV/c muon beam and strong focusing quadrupoles to achieve a normalized transverse emittance of 100 microns and finish 6D cooling. The low beta regions, as low as 5 mm, produced by the quadrupoles are occupied by dense, low Z absorbers, such as lithium hydride or beryllium, that cool the beam. Equilibrium transverse emittance is linearly proportional to the beta function. Reverse emittance exchange with septa and/or wedges is then used to decrease transverse emittance from 100 to 25 microns at the expense of longitudinal emittance for a high energy lepton collider. Cooling challenges include chromaticity correction, momentum passband overlap, quadrupole acceptance, and staying in phase with RF.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB44
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TUPOB61 Recent Improvements to TAPAs, the Android Application for Accelerator Physics and Engineering Calculations ion, lattice, cavity, storage-ring 625

• M. Borland

The Android application TAPAs, the Toolkit for Accelerator Physics on Androids, was released in 2012 and at present has over 300 users. TAPAs provides over 50 calculations, many of which are coupled together. Updates are released about once a month and have provided many new capabilities. Calculations for electron storage rings are a particular emphasis, and have expanded to include CSR threshold, ion trapping, Laslett tune shift, and emittance dilution. Other additions include helical superconducting undulators, rf cavity properties, Compton backscattering, and temperature calculations for mixing water.
Poster TUPOB61 [2.925 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB61
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TUPOB62 Benchmark of Strong-Strong Beam-Beam Simulation of the Kink Instability in an Electron Ion Collider Design ion, proton, electron, simulation 628

• J. Qiang, R.D. Ryne
LBNL, Berkeley, California, USA
• Y. Hao
BNL, Upton, Long Island, New York, USA

The kink instability limits the performance of a potential linac-ring based electron-ion collider design. In this paper, we report on the simulation study of the kink instability using a self-consistent strong-strong beam-beam model.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB62
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TUPOB64 Beam Measurements at the PIP-II Injector Test LEBT ion, solenoid, simulation, ion-source 636

• J.-P. Carneiro, B.M. Hanna, L.R. Prost, V.E. Scarpine, A.V. Shemyakin
Fermilab, Batavia, Illinois, USA

This paper presents the main results obtained during a series of beam measurements performed on the PIP-II Injector Test LEBT from November 2014 to June 2015. The measurements which focus on beam transmission, beam size and emittance at various locations along the beamline are compared with the beam dynamics code TRACK. These studies were aimed at preparing the beam for optimal operation of the RFQ, while evaluating simulation tools with respect to experimental data.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB64
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TUPOB66 Procedure for the Alignment of the Beam in the Electrical Axes of the Pi-Test RFQ ion, rfq, alignment, solenoid 639

• J.-P. Carneiro, L.R. Prost, J. Steimel
Fermilab, Batavia, Illinois, USA

The PI-Test Radio-Frequency Quadrupole (RFQ) has been in operation with beam at Fermilab since March 2016. The RFQ accelerates H beam from 30 keV to 2.1 MeV currently with 20 mus pulses and a maximum current of 10 mA. Once fully conditioned, the RFQ is expected to enable CW operation. Simulations with the beam dynamics code TRACK predict that a misalignment of the beam at the RFQ entrance can possibly deteriorate the transverse and longitudinal emittance at the RFQ exit without necessarily impacting the beam transmission. This paper discusses the procedure developed at Fermilab to align the beam in the electrical axes of the RFQ. Experimental results are shown together with predictions from TRACK.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB66
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WEA1CO04 Hollow Electron Beam Collimation for HL-LHC - Effect on the Beam Core ion, simulation, experiment, electron 651

• M. Fitterer, G. Stancari, A. Valishev
Fermilab, Batavia, Illinois, USA
• R. Bruce, S. Papadopoulou, G. Papotti, D. Pellegrini, S. Redaelli, D. Valuch, J.F. Wagner
CERN, Geneva, Switzerland

Funding: Fermilab is operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the US Department of Energy.
Collimation with hollow electron beams or lenses (HEL) is currently one of the most promising concepts for active halo control in HL-LHC. In previous studies it has been shown that the halo can be efficiently removed with a hollow electron lens. Equally important as an efficient removal of the halo, is also to demonstrate that the core stays unperturbed. In this paper, we present a summary of the experiment at the LHC and simulations in view of the effect of the HEL on the beam core in case of a pulsed operation.

Slides WEA1CO04 [1.830 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEA1CO04
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WEPOA34 Progress on Beam-Plasma Effect Simulations in Muon Ionization Cooling Lattices ion, plasma, simulation, scattering 765

• J.S. Ellison
IIT, Chicago, Illinois, USA
• P. Snopok
Fermilab, Batavia, Illinois, USA
• P. Snopok
Illinois Institute of Technology, Chicago, Illlinois, USA

Funding: Work supported by the U.S. Department of Energy.
New computational tools are essential for accurate modeling and simulation of the next generation of muon-based accelerators. One of the crucial physics processes specific to muon accelerators that has not yet been simulated in detail is beam-induced plasma effect in liquid, solid, and gaseous absorbers. We report here on the progress of developing the required simulation tools and applying them to study the properties of plasma and its effects on the beam in muon ionization cooling channels.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOA34
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WEPOA35 Wedge Absorbers for Muon Cooling with a Test Beam at MICE ion, collider, experiment, simulation 768

• D.V. Neuffer
Fermilab, Batavia, Illinois, USA
• J.G. Acosta, D.J. Summers
UMiss, University, Mississippi, USA
• T.A. Mohayai
IIT, Chicago, Illinois, USA
• P. Snopok
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Work supported by Fermi Research Alliance, LLC under contract No. DE-AC02-07CH11359
Emittance exchange mediated by wedge absorbers is required for longitudinal ionization cooling and for final transverse emittance minimization for a muon collider. A wedge absorber within the MICE beam line could serve as a demonstration of the type of emittance exchange needed for 6-D cooling, including the configurations needed for muon colliders. Parameters for this test are explored in simulation and possible experimental configurations with simulated results are presented.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOA35
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WEPOA36 Simulated Measurements of Beam Cooling in Muon Ionization Cooling Experiment ion, solenoid, experiment, lattice 771

• T.A. Mohayai
IIT, Chicago, Illinois, USA
• D.V. Neuffer, D.V. Neuffer, P. Snopok
Fermilab, Batavia, Illinois, USA
• C.T. Rogers
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
• P. Snopok
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Science Graduate Student Research (SCGSR) under contract No. DE-AC05-06OR23100.
Cooled muon beams are essential to enable future Neutrino Factory and Muon Collider facilities. The international Muon Ionization Cooling Experiment (MICE) aims to demonstrate muon beam cooling through ionization energy loss in material. A figure of merit for muon beam cooling in MICE is the transverse root-mean-square (RMS) emittance reduction and to measure this, the individual muon positions and momenta are reconstructed using two scintillating-fiber tracking detectors housed in spectrometer solenoid modules. The reconstructed positions and momenta before and after a low-Z absorbing material are then used for constructing the covariance matrix and measuring normalized transverse RMS emittance of MICE muon beam. However, RMS emittance is sensitive to nonlinear effects in beam optics. In this study, the direct measurement of phase-space density as an alternative approach to measuring the muon beam cooling using the novel Kernel Density Estimation (KDE) method, is described.

Poster WEPOA36 [1.855 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOA36
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WEPOA40 Construction Status of a RF-Injector with a CNT-Tip Cathode for High Brightness Field-Emission Tests ion, cathode, electron, gun 785

• Y.-M. Shin, G. Fagerberg, M. Figora
Northern Illinois University, DeKalb, Illinois, USA
• A.T. Green
Northern Illinois Univerity, DeKalb, Illinois, USA

We have been constructing a S-band RF-injector system for field-emission tests of a CNT-tip cathode. A pulsed S­band klystron is installed and fully commissioned with 5.5 MW peak power in a 2.5 micro­second pulse length and 1 Hz repetition rate. A single-cell RF­gun is designed to produce with 0.5 - ­ 1 pC electron bunches in a photo-emission mode within a 50 fs­ - 3 ps at 0.5-­ 1 MeV. The measured RF system jitters are within 1 % in magnitude and 0.2° in phase, which would induce 3.4 keV and 0.25 keV of energy jitters, corresponding to 80 fs and 5 fs of temporal jitters, respectively. Our PIC simulations indicate that the designed bunch compressor reduces the TOA­jitter by about an order of magnitude. Emission current and beam brightness of the field-emitted beam are improved by implanting CNT tips on the cathode surface, since they reduce the emission area, while providing high current emission. Once the system is completely commissioned in field-emission mode, the CNT-tip cathode will be tested in terms of klystron-power levels to map out its I-V characteristics under pulse emission condition.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOA40
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WEA3IO01 Emittance Growth from Modulated Focusing in Bunched Beam Cooling ion, electron, simulation, betatron 833

BNL, Upton, Long Island, New York, USA

The low energy RHIC electron cooling (LEReC) project at Brookhaven employs a linac to supply electrons with kinetic energies from 1.6 to 2.6 MeV. Along with cooling the stored ion beam the electron bunches create a coherent space charge field which can cause emittance growth. This is the primary source of heating when the cooling is well tuned. An analytic theory of this process is presented and compared with simulations.
Slides WEA3IO01 [4.160 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEA3IO01
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WEA4CO05 Accelerator Physics Design Requirements and Challenges of RF Based Electron Cooler LEReC ion, electron, cavity, cathode 867

• A.V. Fedotov, M. Blaskiewicz, W. Fischer, D. Kayran, J. Kewisch, S. Seletskiy, J.E. Tuozzolo
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A Low Energy RHIC electron Cooler (LEReC) is presently under construction at BNL to improve the luminosity of the Relativistic Heavy Ion Collider (RHIC). The required electron beam will be provided by a photoemission electron gun and accelerated by a RF linear accelerator. As a result, LEReC will be first bunched beam electron cooler. In addition, this will be the first electron cooler to cool beams under collisions. The achievement of very tight electron beam parameters required for cooling is very challenging and is being addressed by a proper beam transport and engineering design. In this paper, we describe accelerator physics requirements, design considerations and parameters, as well as associated challenges of such electron cooling approach.

Slides WEA4CO05 [4.866 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEA4CO05
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WEPOB01 Lower Emittance Lattice for the Advanced Photon Source Upgrade Using Reverse Bending Magnets ion, lattice, quadrupole, damping 877

• M. Borland, T.G. Berenc, R.R. Lindberg, V. Sajaev, Y.P. Sun
ANL, Argonne, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
he Advanced Photon Source (APS) is pursuing an upgrade to the storage ring to a hybrid seven-bend-achromat design*. The nominal design provides a natural emittance of 67 pm. By adding reverse dipole fields to several quadrupoles**, we can reduce the natural emittance to 41 pm while simultaneously providing more optimal beta functions in the insertion devices. The improved emittance results from a combination of increased energy loss per turn and a change in the damping partition. At the same time, the nonlinear dynamics performance is very similar, thanks in part to increased dispersion in the sextupoles. This paper describes the properties, optimization, and performance of the new lattice.
* L. Farvacque et al., IPAC13, 79 (2013).
** J.P. Delahaye \em et al., PAC89, 1611 (1990); A. Streun, NIM A 737, 148 (2014).

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB01
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WEPOB14 APS-U Lattice Design for Off-Axis Accumulation ion, lattice, injection, quadrupole 920

• Y.P. Sun, M. Borland, R.R. Lindberg, V. Sajaev
ANL, Argonne, Illinois, USA

A 67-pm hybrid-seven-bend achromat (H7BA) lattice is being proposed for a future Advanced Photon Source (APS) multi-bend-achromat (MBA) upgrade project. This lattice design pushes for smaller emittance and requires use of a swap-out (on-axis) injection scheme due to limited dynamic acceptance. Alternate lattice design work has also been performed for the APS upgrade to achieve better beam dynamics performance than the nominal APS MBA lattice, in order to allow off-axis accumulation. Two such alternate H7BA lattice designs, which target a still-low emittance of 90 pm, are discussed in detail in this paper. Although the single-particle-dynamics performance is good, simulations of collective effects indicate that surprising difficulty would be expected accumulating high single-bunch charge in this lattice. The brightness of the 90-pm lattice is also a factor of two lower than the 67-pm H7BA lattice.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB14
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WEPOB36 Upgrade of the Cornell Electron Storage Ring as a Synchrotron Light Source ion, undulator, lattice, injection 980

• D. L. Rubin, J.A. Crittenden, J.P. Shanks, S. Wang
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF-DMR 13-32208
The planned upgrade of the Cornell Electron Storage Ring as an X-ray source for CHESS will include an increase in beam energy and decrease in emittance from 100 nm-rad at 5.3 GeV to 30 nm-rad at 6 GeV, increase in beam current from 120 to 200 mA, continuous top-off injection of the single circulating beam, and four new zero dispersion inser- tion straights that can each accommodate a pair of canted undulators. The existing sextant of the storage ring arc that serves as the source for all of the CHESS X-ray beam lines will be reconfigured with 6 double-bend achromats, each consisting of two pairs of horizontally focusing quadrupoles, and a single pair of combined-function gradient bend magnets. The chromaticity will be compensated by the existing sextupoles in the legacy FODO arcs. We describe details of the linear optics, sextupole distributions to maximize dynamic aperture and injection efficiency, and characterization of magnetic field and alignment error tolerance.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB36
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WEPOB39 Photo-Injector Optimization and Validation Study with the OPAL Beam Simulation Code ion, simulation, booster, FEL 984

• L.D. Duffy, K. Bishofberger, J.W. Lewellen, S.J. Russell, D.Y. Shchegolkov
LANL, Los Alamos, New Mexico, USA

A 42 keV x-ray free electron laser (XFEL) is a plausible technology alternative for the Matter Radiation Interactions in Extremes (MaRIE) experimental project, a concept developed by Los Alamos National Laboratory. An early pre-conceptual design for such an XFEL calls for 100 pC electron bunches with very low emittance and energy spread. High fidelity simulations that capture all beamline physics will be required to ensure a successful design. We expect to use the beam simulation code OPAL as one of the tools in this process. In this study, we validate OPAL as a photo-injector design tool by comparing its performance with published PITZ experimental data and simulations.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB39
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WEPOB56 Beam Optics for the RHIC Low Energy Electron Cooler (LEReC) ion, electron, booster, space-charge 1015

• J. Kewisch, A.V. Fedotov, D. Kayran, S. Seletskiy
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
A Low-energy RHIC Electron Cooler (LEReC) system is presently under construction at Brookhaven National Laboratory. This device shall enable gold ion collisions at energies below the design injection energy with sufficient luminosity. Electron beam with energies between 1.6, 2.0 and 2.6 MeV are necessary. This machine will be the first to attempt electron cooling using bunched electron beam, using a 703 MHz SRF cavity for acceleration. Special consideration must be given to the effect of space charge forces on the transverse and longitudinal beam quality. We will present the current layout of the cooler and beam parameter simulations using the computer codes PARMELA.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB56
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WEPOB68 DESIGN AND SIMULATION OF EMITTANCE MEASUREMENT WITH MULTI-SLIT FOR LEREC ion, electron, simulation, space-charge 1045

• C. Liu, A.V. Fedotov, J. Kewisch, M.G. Minty
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
To improve the luminosity of beam energy scan of low energy Au-Au collision, a electron machine is under con- struction to cool ion beams in both RHIC rings with pulsed electron beam. Over the course of the project, a multi- slit device is needed to characterize the transverse beam emittance of three energies, 0.4, 1.6 and 2.6 MeV. This re- port shows the optimization and compromise of the design, which include the slit width, slit spacing, and drift space from the multi-slit to the downstream profile monitor.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB68
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THPOA04 Maximum Brightness of Linac-Driven Electron Beams in the Presence of Collective Effects ion, brightness, linac, electron 1101

• S. Di Mitri
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Linear accelerators capable of delivering high brightness electron beams are essential components of a number of research tools, such as free electron lasers (FELs) and elementary particle colliders. In these facilities the charge density is high enough to drive undesirable collective effects (wakefields) that may increase the beam emittance relative to the injection level, eventually degrading the nominal brightness. We formulate a limit on the final electron beam brightness, imposed by the interplay of geometric transverse wakefield in accelerating structures and coherent synchrotron radiation in energy dispersive regions*. Numerous experimental data of VUV and X-ray FEL drivers validate our model. This is then used to show that a normalized brightness of 1016 A/m2, promised so far by ultra-low charge beams (1-10 pC), can in fact be reached with a 100 pC charge beam in the Italian FERMI FEL linac, with the existing machine configuration.**
*Physical Review Special Topics - Accelerators And Beams 17, 110702 (2014)
**Physical Review Special Topics - Accelerators And Beams 16, 050701 (2013)

Poster THPOA04 [0.828 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA04
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THPOA05 Intrabeam Scattering in High Brightness Electron Linacs ion, electron, linac, quadrupole 1104

• S. Di Mitri
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

The role played by Intra-Beam Scattering (IBS) in high brightness electron linacs, like those driving free electron lasers, is studied analytically and with particle tracking. We found that IBS typically plays no significant role in the microbunching instability that develops in such accelerators*. A partial damping of the instability through IBS is envisaged, however, with dedicated magnetic insertions. The feasibility of linear and circular lattice designs to cumulate relevant IBS-induced energy spread, and the interplay with microbunching instability, are discussed theoretically, and with the help of tracking codes.
* S. Di Mitri, PRST-AB 17, 074401 (2014)

Poster THPOA05 [0.547 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA05
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THPOA06 CSR-Immune Arc Compressors for Recirculating Accelerators Driving High Brightness Electron Beams ion, optics, dipole, sextupole 1108

• S. Di Mitri, M. Cornacchia
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

The advent of short electron bunches in high brightness linear accelerators has raised the awareness of the accelerator community to the degradation of the beam transverse emittance by coherent synchrotron radiation (CSR) emitted in magnetic bunch length compressors, transfer lines and turnaround arcs. We reformulate the concept of CSR-driven beam optics balance, and apply it to the general case of varying bunch length in an achromatic cell*. The dependence of the CSR-perturbed emittance to beam optics, mean energy, and bunch charge is shown. The analytical findings are compared with particle tracking results**. Practical considerations on CSR-induced energy loss and nonlinear particle dynamics are included. As a result, we identify the range of parameters that allows feasibility of an arc compressor in a recirculating accelerator driving, for example, a free electron laser or a linear collider.
*S. Di Mitri and M. Cornacchia, EPL, 109 (2015) 62002
**S. Di Mitri, NIM A 806 (2016) 184'192

Poster THPOA06 [0.616 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA06
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THPOA08 Transformer Ratio Enhancement Experiment Based on Emittance Exchanger in Argonne Wakefield Accelerator ion, wakefield, experiment, GUI 1115

• Q. Gao, H.B. Chen, J. Shi
TUB, Beijing, People's Republic of China
• S.P. Antipov
Euclid Beamlabs LLC, Bolingbrook, USA
• M.E. Conde, D.S. Doran, W. Gai, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Argonne, Illinois, USA
• C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA

The transformer ratio is an important figure of merit in collinear wakefield acceleration, it indicates the efficiency of energy transferring from drive bunch to witness bunch. Higher transformer ratio will significantly reduce the length of accelerator thus reducing the cost of accelerator construction. However, for the gaussian bunch, this ratio has its limit of 2. To obtain higher transformer ratio, one possible method is to tailor the beam current profile to specific shapes. One method of beam shaping is based on emittance exchange, which has been demonstrated at the Argonne Wakefield Accelerator. Its principle is to tailor the beam transversely using a mask then exchange the beam's transverse profile and longitudinal profile. In this paper, we describe our efforts to optimize the beamline and mask in order to generate a triangular beam with quadratic head, which has a transformer ratio of 6.4. We also present our design of a dielectric slab based accelerating structure to measure the transformer ratio. Finally, we discuss an experiment for this high transformer ratio at Argonne Wakefield Accelerator Laboratory.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA08
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THPOA14 Ion Effects in the APS Particle Accumulator Ring ion, simulation, vacuum, coherent-effects 1123

• J.R. Calvey, K.C. Harkay, C. Yao
ANL, Argonne, Illinois, USA

Trapped ions in the APS Particle Accumulator Ring (PAR) lead to a positive coherent tune shift in both planes, which increases along the PAR cycle as more ions accumulate. This effect has been studied using an ion simulation code developed at SLAC. After modifying the code to include a realistic vacuum profile, multiple ionization, and the effect of shaking the beam to measure the tune, the simulation agrees well with our measurements. This code has also been used to evaluate the possibility of ion instabilities at the high bunch charge needed for the APS-Upgrade.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA14
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THPOA15 Adaptive Space Charge Calculations in MADX-SC ion, simulation, optics, resonance 1126

• Y.I. Alexahin, V.V. Kapin, A. Valishev
Fermilab, Batavia, Illinois, USA
• F. Schmidt, R. Wasef
CERN, Geneva, Switzerland

Funding: Work supported by Fermi Research Alliance, LLC under Contract DE-AC02-07CH11359 with the U.S. DOE
Since a few years MAD-X allows to simulate beam dynamics with frozen space charge à la Basseti-Erskine. The limitation of simulation with a fixed distribution is somewhat overcome by an adaptive approach that consists of updating the emittances once per turn and by recalculating the Twiss parameters after certain intervals, typically every 1,000 turns to avoid an excessive slowdown of the simulations. The technique has been benchmarked for the PS machines over 800, 000 turns. MADX-SC code developments are being discussed that include the re-introduction of acceleration into MAD-X and more advanced beam σ calculations that will avoid code interruptions for the Twiss parameters calculation.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA15
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THPOA16 Gaseous H2-Filled Helical FOFO Snake for Initial 6D Ionization Cooling of Muons ion, solenoid, focusing, dipole 1129

• Y.I. Alexahin
Fermilab, Batavia, Illinois, USA

Funding: Work supported by Fermi Research Alliance, LLC under Contract DE-AC02-07CH11359 with the U.S. DOE
H2 gas-filled channel for 6D ionization cooling of muons is described which consists of periodically inclined solenoids of alternating polarity with 325MHz RF cavities inside them. To provide sufficient longitudinal cooling LiH wedge absorbers are placed at the minima of transverse beta-function between the solenoids. An important feature of such channel (called Helical FOFO snake) is that it can cool simultaneously muons of both signs. Theoretical considerations as well as results of simulations with G4beamline are presented.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA16
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THPOA17 Computing Eigen-Emittances from Tracking Data ion, optics, simulation, controls 1132

• Y.I. Alexahin
Fermilab, Batavia, Illinois, USA

Funding: Work supported by Fermi Research Alliance, LLC under Contract DE-AC02-07CH11359 with the U.S. DOE
In a strongly nonlinear system the particle distribution in the phase space may develop long tails which contribution to the covariance (σ) matrix should be suppressed for a correct estimate of the beam emittance. A method is offered based on Gaussian approximation of the original particle distribution in the phase space (Klimontovich distribution) which leads to an equation for the σ matrix which provides efficient suppression of the tails and cannot be obtained by introducing weights. This equation is easily solved by iterations in the multi-dimensional case. It is also shown how the eigen-emittances and coupled optics functions can be retrieved from the σ matrix in a strongly coupled system.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA17
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THPOA32 Sensitivity of the Microbunching Instability to Irregularities in Cathode Current in the LCLS-II Beam Delivery System ion, cathode, bunching, undulator 1171

• C.E. Mitchell, J. Qiang, M. Venturini
LBNL, Berkeley, California, USA
• P. Emma
SLAC, Menlo Park, California, USA

Funding: This work is supported by the Office of Science of the U.S. Department of Energy under Contract Numbers DE-AC02-76SF00515, DE-AC02-05CH11231, and the LCLS-II Project.
LCLS-II is a high-repetition rate (1 MHz) Free Electron Laser (FEL) X-ray light source now under construction at SLAC National Accelerator Laboratory. During transport to the FEL undulators, the electron beam is subject to a space charge-driven microbunching instability that can degrade the electron beam quality and lower the FEL performance if left uncontrolled. The present LCLS-II design is well-optimized to control the growth of this instability out of the electron beam shot noise. However, the instability may also be seeded by irregularities in the beam current profile at the cathode (due to non-uniformities in the temporal profile of the photogun drive laser pulse). In this paper, we describe the sensitivity of the microbunching instability to small-amplitude temporal modulations on the emitted beam current profile at the cathode, using high-resolution simulations of the LCLS-II beam delivery system.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA32
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THPOA46 Benchmark of RF Photoinjector and Dipole Using ASTRA, GPT, and OPAL ion, simulation, gun, dipole 1194

• N.R. Neveu
IIT, Chicago, Illinois, USA
PSI, Villigen PSI, Switzerland
• G. Ha
POSTECH, Pohang, Kyungbuk, Republic of Korea
• C.J. Metzger-Kraus
HZB, Berlin, Germany
• N.R. Neveu, J.G. Power
ANL, Argonne, Illinois, USA
• P. Piot
Fermilab, Batavia, Illinois, USA
• P. Piot
Northern Illinois University, DeKalb, Illinois, USA
• S.J. Russell
LANL, Los Alamos, New Mexico, USA
• L.K. Spentzouris
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Grant no. DE-SC0015479, and contract No. DE-AC02-06CH11357.
With the rapid improvement in computing resources and codes in recent years, accelerator facilities can now achieve and rely on accurate beam dynamics simulations. These simulations include single particle effects (e.g. particle tracking in a magnetic field) as well as collective effects such as space charge (SC), and coherent synchrotron radiation (CSR). Using portions of the Argonne Wakefield Accelerator (AWA) as the benchmark model, we simulated beam dynamics with three particle tracking codes. The AWA rf photoinjector was benchmarked, primarily to study SC, in ASTRA, GPT, and OPAL-T using a 1 nC beam. A 20° dipole magnet was used to benchmark CSR effects in GPT and OPAL-T by bending a 1nC beam at energies between 2 MeV and 100 MeV. In this paper we present the results, and discuss the similarities and differences between the codes.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA46
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THPOA56 Primary Study of the Photocathode Electron Gun With a Cone Cathode and Radial Polarization Laser cathode, ion, gun, laser 1216

• R. Huang, Q.K. Jia
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: This work is partly supported by the National Nature Science Foundation of China under Grant No. 11375199.
The linearly polarized laser with oblique incidence can achieve a higher quantum efficiency (QE) of metal cathodes than that with the normal incidence, which however requires the wavefront shaping for better performance. To maintain the high QE and simplify the system, we propose a cone cathode electron gun with a radial polarization laser at normal incidence. The primary analytical estimation and numerical simulations are explored for its effect on the emittance of the electron beam.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA56
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THPOA61 A Possible Emittance Reduction Scheme for PLSII ion, lattice, quadrupole, electron 1226

• T.-Y. Lee
PAL, Pohang, Kyungbuk, Republic of Korea

As the upgrade of PLS, PLSII is a 3 GeV light source in 12 super-periods (281.8 m circumference) with 5.8 nm design emittance and can store electron beam up to 400 mA with 3 superconducting RF cavities. PLSII lattice is a double bend achromatic (DBA) lattice with 2 straight sections for each cell (24 straight sections). After comple-tion of PLSII, multi-bend achromatic lattice has widely been adopted to accomplish low emittance. This paper discusses how a minimal change can modify the PLSII's DBA to a quadruple bend achromatic (QBA) lattice and reduce the emittance to about a half value.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA61
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THPOA68 The First Particle-Based Proof of Principle Numerical Simulation of Electron Cooling ion, electron, proton, simulation 1241

• S. Abeyratne, B. Erdelyi
Northern Illinois University, DeKalb, Illinois, USA

Envisioned particle accelerators such as JLEIC demand unprecedented luminosities of 1034 cm -2 s -1 and small emittances are key to achieve them. Electron cooling, where a 'cold' electron beam and the 'hot' proton or ion beam co-propagate in the cooling section of the accelerator, can be used to reduce the emittance growth. It is required to precisely calculate the cooling force among particles to estimate accurately the cooling time. There are different methods to simulate electron cooling. We have developed a novel code, Particles' High-order Adaptive Dynamics (PHAD), for electron cooling. This code differs from other established methods since it is the first particle-based simulation method employing full particle nonlinear dynamics. In this paper we present the first results obtained that establish electron cooling of heavy ions.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA68
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FRA1CO04 6D Phase Space Measurement of Low Energy, High Intensity Hadron Beam ion, simulation, electron, quadrupole 1271

• B.L. Cathey
ORNL RAD, Oak Ridge, Tennessee, USA
• A.V. Aleksandrov, S.M. Cousineau, A.P. Zhukov
ORNL, Oak Ridge, Tennessee, USA

Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. The work has been partially supported by NSF grant 1535312
The goal of this project is to demonstrate a method for measuring the full 6D phase space of an low energy, high intensity hadron beam. This is done by combining 4D emittance measurement techniques along with dispersion measurement and a beam shape monitor to provide the energy and phase space components. The measurement will be performed on new Beam Testing Facility (BTF) at the Spallation Neutron Source (SNS), a 2.5 MeV functional duplicate of the SNS accelerator front end.

Slides FRA1CO04 [8.295 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-FRA1CO04
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