NAPAC2016 - List of Keywords (cathode)

Paper	Title	Other Keywords	Page
MOPOB61	Updates of Vertical Electropolishing Studies at Cornell with KEK and Marui Galvanizing Co. Ltd .	ion, cavity, SRF, target	208
	F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, T. Saeki KEK, Ibaraki, Japan
	Cornell, KEK, and Marui Galvanizing Co. Ltd (MGI) have started new Vertical Electro-Polishing (VEP) R&D collaboration in 2014. MGI and KEK has developed their original VEP cathode named 'i-cathode Ninja'® which has four retractable wing-shape parts per cell for single-/9-cell cavities. One single cell cavity had processed with VEP using i-cathode Ninja at Cornell. Cornell also performed the vertical test on that cavity. We will present the details of process and RF test result at Cornell.
	Poster MOPOB61 [2.251 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOPOB61
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MOPOB81	Deposition of Non-Evaporative Getters R&D Activity for HEPS-TF	ion, vacuum, site, distributed	238
	P. He, D.Z. Guo, B. Liu, Y. Ma, Y.C. Yang, L. Zhang IHEP, Beijing, People's Republic of China
	Non Evaporable Getter(NEG) coating technology was widely used around the world's ultra-low emittance storage rings. It will provide the distributed pumping which is the obvious solution to solve the conductance limitation of narrow vacuum chamber at small magnet aperture. The HEPS-TF is the R&D project of HEPS (High Energy Photon Source), it will cover all of the key technology for HEPS accelerator system and beamlines. In order to meet the small aperture vacuum chamber distributed pumping requirement, the NEG coating R&D for HEPS vacuum chamber is under the way. Getter films deposited on the inner surface of the chamber would transform the vacuum chamber from an outgassing source into a pump. The coating test bench will be shown here and coating procedure will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOPOB81
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TUB3IO02	Overview of Electron Source Development for High Repetition Rate FEL Facilities	ion, gun, electron, emittance	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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TUB3CO04	A New Thermionic RF Electron Gun for Synchrotron Light Sources	ion, gun, coupling, electron	453
	S.V. Kutsaev, A.Y. Murokh, E.A. Savin, A.Yu. Smirnov, A.V. Smirnov RadiaBeam Systems, Santa Monica, California, USA R.B. Agustsson, J.J. Hartzell, A. Verma RadiaBeam, Santa Monica, California, USA A. Nassiri, Y. Sun, G.J. Waldschmidt, A. Zholents ANL, Argonne, Illinois, USA E.A. Savin MEPhI, Moscow, Russia
	Funding: This work is supported by the U.S. Department of Energy, Office of Basic Energy Science, under contract DE-SC0015191 and contract No. DE-AC02-06CH11357. A thermionic RF gun is a compact and efficient source of electrons used in many practical applications. RadiaBeam Systems and the Advanced Photon Source of Argonne National Laboratory collaborate in developing of a reliable and robust thermionic RF gun for synchrotron light sources which would offer substantial improvements over existing thermionic RF guns and allow stable operation with up to 1A of beam peak current at a 100 Hz pulse repetition rate and a 1.5 μs RF pulse length. In this paper, we discuss the electromagnetic and engineering design of the cavity, and report the progress towards high power tests of the cathode assembly of the new gun.
	Slides TUB3CO04 [2.661 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUB3CO04
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TUPOB16	A Simple Method for Measuring the Electron-Beam Magnetization	ion, solenoid, electron, emittance	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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WEPOA40	Construction Status of a RF-Injector with a CNT-Tip Cathode for High Brightness Field-Emission Tests	ion, electron, gun, emittance	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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WEPOA42	RF Design of a 1.3-GHz High Average Beam Power SRF Electron Source	ion, gun, electron, simulation	789
	N. Sipahi, S. Biedron, S.V. Milton CSU, Fort Collins, Colorado, USA I.V. Gonin, R.D. Kephart, T.N. Khabiboulline, N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	There is a significant interest in developing high-average power electron sources, particularly those integrated with Superconducting Radio Frequency (SRF) accelerator systems. Even though there are examples of high-average-power electron sources, they are not compact, highly efficient, or available at a reasonable cost. Adapting the recent advances in SRF cavities, RF power sources, and innovative solutions for an SRF gun and cathode system, we have developed a design concept for a compact SRF high-average power electron linac. This design will produce electron beams with energies up to 10 MeV. In this paper, we present the design results of our cathode structure integrated with modified 9-cell accelerating structure.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOA42
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WEPOA62	The Center for Bright Beams	ion, brightness, electron, cavity	830
	J.R. Patterson, G.H. Hoffstaetter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA Y.K. Kim University of Chicago, Chicago, Illinois, USA
	Funding: National Science Foundation award PHY-1549132. The Center for Bright Beams (CBB) is a new National Science Foundation-supported Science and Technology Center. CBB's research goal is to increase the brightness of electron beams while reducing the cost and size of key technologies. To achieve this, it will augment the capabilities of accelerator physicists with those of physical chemists, materials scientists, condensed matter physicists, plasma physicists, and mathematicians. This approach has the potential to increase the brightness of electron sources through better photocathodes, the efficiency and gradient of SRF cavities through deeper understanding of superconducting compounds and their surfaces, and better understanding of beam storage and transport and the associated optics by using new mathematical techniques.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOA62
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WEA4CO05	Accelerator Physics Design Requirements and Challenges of RF Based Electron Cooler LEReC	ion, electron, cavity, emittance	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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WEPOB11	Tuning of the APS Linac Accelerating Cavities After Structural Re-Alignment	ion, linac, cavity, photon	910
	T.L. Smith, G.J. Waldschmidt ANL, Argonne, Illinois, USA
	A new S-band LCLS type Photo-cathode (PC) gun was recently installed in the APS linac. As a consequence, it was recognized that many of the linac accelerating structures were out of their 1mm straightness tolerances. In order to reduce the effects of wakefield on the beam, several of the misaligned structures were straightened. This paper discusses the bead-pull RF measurements, the effect of the straightening efforts on rf and the cell to cell retuning efforts that were performed.
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WEPOB19	Summary of Cs2te Photocathode Performance and Improvements in the High-Gradient, High-Charge AWA Drive Gun	ion, gun, operation, wakefield	934
	E.E. Wisniewski, S.P. Antipov, M.E. Conde, D.S. Doran, W. Gai, C.-J. Jing, W. Liu, J.G. Power, J.Q. Qiu, C. Whiteford ANL, Argonne, Illinois, USA S.P. Antipov, C.-J. Jing, J.Q. Qiu Euclid TechLabs, LLC, Solon, Ohio, USA
	Funding: Argonne, a U.S.A. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The AWA L-band, high-charge photoinjector for the 70 MeV drive beamline has been operating for almost 3 years at the Argonne Wakefield Accelerator (AWA) facility. at Argonne National Laboratory (ANL). The gun operates at high-field (85 MV/m peak field on the cathode) and has a high quantum efficiency (QE) Cesium telluride photocathode with a large area (30 mm diameter). It produces high-charge, short pulse, single bunches (Q > 100 nC) as well as long bunch-trains (Q > 600 nC) for wakefield experiments (high peak current). During the first two years of operation, photocathode performance was evaluated and areas of improvement were identified. After study, consideration and consultation, steps were taken to improve the performance of the photocathode. So far, in total, three photocathodes have been fabricated on-site, installed and operated in the gun. Improvements made to the photocathode plug, vacuum system, and gun operation are detailed. The results include vastly improved conditioning times, better cathode performance, and QE above 4% for over 11 months.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB19
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WEPOB25	Analytical Modeling of Electron Back-Bombardment Induced Current Increase in Un-Gated Thermionic Cathode Rf Guns	ion, gun, electron, simulation	953
	J.P. Edelen Fermilab, Batavia, Illinois, USA J.R. Harris Directed Energy Directorate, Air Force Research Laboratory, Albuquerque, USA J.W. Lewellen LANL, Los Alamos, New Mexico, USA Y. Sun ANL, Argonne, Illinois, USA
	In this paper we derive analytical expressions for the output current of an un-gated thermionic cathode RF gun in the presence of back-bombardment heating. We provide a brief overview of back-bombardment theory and discuss comparisons between the analytical back-bombardment predictions and simulation models. We then derive an expression for the output current as a function of the RF repetition rate and discuss relationships between back-bombardment, field-enhancement, and output current. We discuss in detail the relevant approximations and then provide predictions about how the output current should vary as a function of repetition rate for some given system configurations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB25
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WEPOB26	Observation of Repetition-Rate Dependent Emission From an Un-Gated Thermionic Cathode Rf Gun	ion, gun, electron, experiment	956
	J.P. Edelen Fermilab, Batavia, Illinois, USA J.R. Harris Directed Energy Directorate, Air Force Research Laboratory, Albuquerque, USA J.W. Lewellen LANL, Los Alamos, New Mexico, USA Y. Sun ANL, Argonne, Illinois, USA
	Recent work at Fermilab in collaboration with the Advanced Photon Source and members of other national labs, designed an experiment to study the relationship between the RF repetition rate and the average current per RF pulse. While existing models anticipate a direct relationship between these two parameters we observed an inverse relationship. We believe this is a result of damage to the barium coating on the cathode surface caused by a change in back-bombardment power that is unaccounted for in the existing theories. These observations shed new light on the challenges and fundamental limitations associated with scaling an un-gated thermionic cathode RF gun to high average current.
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WEPOB29	Modeling of Dark Current Generation and Transport Using the IMPACT-T Code	ion, electron, cavity, space-charge	964
	J. Qiang, K. Hwang LBNL, Berkeley, California, USA
	Dark current from unwanted electrons in photoinjector can present significant danger to the accelerator operation by causing damage to photocathode and power deposition onto conducting wall. In this paper, we present numerical models of dark current generation from the field emission and from the electron impact ionization of the residual gas that were recently developed in the IMPACT-T code. We also report on the application of above numerical model to an LCLS-II like photoinjector.
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WEPOB49	LCLS Injector Laser Profile Shaping Using Digital Micromirror Device	laser, ion, electron, target	1001
	S. Li Stanford University, Stanford, California, USA S.C. Alverson, D.K. Bohler, A.R. Fry, S. Gilevich, Z. Huang, A. Miahnahri, D.F. Ratner, J. Robinson, F. Zhou SLAC, Menlo Park, California, USA
	In the Linear Coherent Light Source (LCLS) at SLAC, the injector laser plays an important role as the source of the electron beam for the Free Electron Laser (FEL). The emittance of the beam is highly related to the transverse profile of the injector laser. Currently the LCLS injector laser has undesired features, such as hot spots, which carry over to the electron beam. These undesired features increase electron emittance, degrade the FEL performance, and complicate operations. The injector laser shaping project at LCLS aims to produce arbitrary electron beam profiles, such as cut-Gaussian, uniform, and parabolic, and to study the effect of spatial profiles on beam emittance and FEL performance. Effectively it also allows easy transition between the two spare lasers, where the operators can use the spatial shaper to achieve identical profiles for the two lasers. In this paper, we describe the experimental methods to achieve laser profile shaping and electron beam profile shaping respectively, and demonstrate promising results.
	Poster WEPOB49 [1.850 MB]
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WEPOB55	Simulation of Stray Electrons in the RHIC Low Energy Cooler	ion, electron, cavity, SRF	1012
	J. Kewisch 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. The Low Energy RHIC electron Cooler, under construction at BNL, accelerates electrons with a 400 kV DC gun and a 2.2 MeV SRF booster cavity. Electrons which leave the cathode at the wrong time will not be accelerated to the correct energies and will not reach the beam dump at the end of the accelerator. Thy may impact the beam pipe after incorrect deflection in dipoles or after being slowed down longitudinally in the booster while the transverse momentum is not affected. In some cases their direction is reversed in the booster and they will impact the cathode. We simulated the trajectories of these electrons using the GPT tracking code. The results are qualitative, not quantitative, since the sources and numbers of the stray electrons are unknown.
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WEPOB58	Cathode Puck Insertion System Design for the LEReC Photoemission DC Electron Gun	ion, gun, vacuum, insertion	1021
	C.J. Liaw, V. De Monte, L. DeSanto, K. Hamdi, M. Mapes, T. Rao, A.N. Steszyn, J.E. Tuozzolo, J. Walsh BNL, Upton, Long Island, New York, USA K.W. Smolenski Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. DOE. The operation of LEReC is to provide an electron cooling to improve the luminosity of the RHIC heavy ion beam at lower energies in a range of 2.5-25 GeV/nucleon. The electron beam is generated in a DC Electron Gun (DC gun) designed and built by the Cornell High Energy Synchrotron Source Group. This DC gun will operate around the clock for at least two weeks without maintenance. This paper presents the design of a reliable cathode puck insertion system, which includes a multi-pucks storage device, a transfer mechanism, a puck insertion device, a vacuum/control system, and a transport scheme.
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WEPOB59	Performance of CEC Pop Gun During Commissioning	ion, gun, laser, cavity	1024
	I. Pinayev, W. Fu, Y. Hao, M. Harvey, T. Hayes, J.P. Jamilkowski, Y.C. Jing, P. K. Kankiya, D. Kayran, R. Kellermann, V. Litvinenko, G.J. Mahler, M. Mapes, K. Mernick, K. Mihara, T.A. Miller, G. Narayan, M.C. Paniccia, W.E. Pekrul, T. Rao, F. Severino, B. Sheehy, J. Skaritka, K.S. Smith, J.E. Tuozzolo, E. Wang, G. Wang, W. Xu, A. Zaltsman, Z. Zhao BNL, Upton, Long Island, New York, USA I. Petrushina SUNY SB, Stony Brook, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The Coherent Electron Cooling Proof-of-Principle (CeC PoP) experiment employs a high-gradient CW photo-injector based on the superconducting RF cavity. Such guns operating at high accelerating gradients promise to revolutionize many sciences and applications. They can establish the basis for super-bright monochromatic X-ray and gamma ray sources, high luminosity hadron colliders, nuclear waste transmutation or a new generation of microchip production. In this paper we report on our operation of a superconducting RF electron gun with a high accelerating gradient at the CsK2Sb photo-cathode (i.e. ~ 20 MV/m) generating a record-high bunch charge (above 4 nC). We give short description of the system and then detail our experimental results.
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WEPOB67	K2CsSb Photocathode Performance in QWR SRF Gun	ion, gun, multipactoring, vacuum	1042
	E. Wang, Y. Hao, Y.C. Jing, V. Litvinenko, I. Pinayev, T. Rao, J. Skaritka, G. Wang, T. Xin BNL, Upton, Long Island, New York, USA
	In 2016 run of Coherent Electron Cooling, we have successfully tested the performance of a number of K2CsSb cathodes. These cathodes with QE of 6%-10% were fabricated in Instrumentation Division, a few miles away, transported to RHIC tunnel under UHV conditions, attached to the CeC gun, kept in storage, and inserted in the gun as needed. A maximum bunch charge of 4.6 nC was generated in the gun when the QE was 1.8 %. With careful conditioning at increasing accelerating fields, it was possible to maintain the QE of several cathodes for more than a week. For the cathodes that experienced degradation, the primary cause was multipacting when the power into the gun was increased. In the initial runs, the entire 20 mm substrate face was coated with the cathode material causing cathode induced multipacting. For subsequent measurements, the substrate was masked to coat only the central 9 mm of the substrate. By optimizing the procedure for boosting the power to the gun and covering all viewports to minimize dark current, we were able to minimize QE degradation. In this paper we discuss the cathode preparation, transfer to the gun and operational experience with the cathodes in 112 MHz gun.
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THA2CO03	New 1.4 Cell RF Photoinjector Design for High Brightness Beam Generation	ion, brightness, laser, electron	1083
	E. Pirez, P. Musumeci UCLA, Los Angeles, California, USA D. Alesini INFN/LNF, Frascati (Roma), Italy J.M. Maxson Cornell University, Ithaca, New York, USA
	Funding: This work was partially funded by NSF grant 145583 The new electromagnetic and mechanical designs of the S-band 1.4 cell photoinjector are discussed. A novel fabrication method is adopted to replace the brazing process with a clamping technique achieving lower breakdown probability. The photoinjector is designed to operate at a 120 MV/m gradient and an optimal injection phase of 70 degrees to improve the extraction field by a factor of 1.9 compared to standard 1.6 cell designs with the same peak field. New geometries and features are implemented to improve beam quality for the demand of high brightness beam applications.
	Slides THA2CO03 [2.444 MB]
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THPOA32	Sensitivity of the Microbunching Instability to Irregularities in Cathode Current in the LCLS-II Beam Delivery System	ion, bunching, undulator, emittance	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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THPOA42	3D Modeling and Simulations of Electron Emission From Photocathodes With Controlled Rough Surfaces	ion, electron, simulation, scattering	1187
	D.A. Dimitrov, G.I. Bell, D.N. Smithe, C.D. Zhou Tech-X, Boulder, Colorado, USA I. Ben-Zvi, J. Smedley BNL, Upton, Long Island, New York, USA S.S. Karkare, H.A. Padmore LBNL, Berkeley, California, USA
	Funding: This work is supported by the US DOE Office of Science, department of Basic Energy Sciences under grant DE-SC0013190. Developments in materials design and synthesis have resulted in photocathodes that can have a high quantum efficiency (QE), operate at visible wavelengths, and are robust enough to operate in high electric field gradient photoguns, for application to free electron lasers and in dynamic electron microscopy and diffraction. However, synthesis often results in roughness, ranging from the nano to the microscale. The effect of this roughness in a high gradient accelerator is to produce a small transverse accelerating gradient, which therefore results in emittance growth. Although analytical formulations of the effects of roughness have been developed, a full theoretical model and experimental verification are lacking, and our work aims to bridge this gap. We report results on electron emission modeling and 3D simulations from photocathodes with controlled surface roughness similar to grated surfaces that have been fabricated by nanolithography. The simulations include both charge carrier dynamics in the photocathode material and a general electron emission modeling that includes field enhancement effects at rough surfaces. The models are being implemented in the VSim code.
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THPOA56	Primary Study of the Photocathode Electron Gun With a Cone Cathode and Radial Polarization Laser	ion, gun, laser, emittance	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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MOPOB61

Updates of Vertical Electropolishing Studies at Cornell with KEK and Marui Galvanizing Co. Ltd .

ion, cavity, SRF, target

208

F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, T. Saeki
KEK, Ibaraki, Japan

Cornell, KEK, and Marui Galvanizing Co. Ltd (MGI) have started new Vertical Electro-Polishing (VEP) R&D collaboration in 2014. MGI and KEK has developed their original VEP cathode named 'i-cathode Ninja'® which has four retractable wing-shape parts per cell for single-/9-cell cavities. One single cell cavity had processed with VEP using i-cathode Ninja at Cornell. Cornell also performed the vertical test on that cavity. We will present the details of process and RF test result at Cornell.

Poster MOPOB61 [2.251 MB]

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MOPOB81

Deposition of Non-Evaporative Getters R&D Activity for HEPS-TF

ion, vacuum, site, distributed

238

P. He, D.Z. Guo, B. Liu, Y. Ma, Y.C. Yang, L. Zhang
IHEP, Beijing, People's Republic of China

Non Evaporable Getter(NEG) coating technology was widely used around the world's ultra-low emittance storage rings. It will provide the distributed pumping which is the obvious solution to solve the conductance limitation of narrow vacuum chamber at small magnet aperture. The HEPS-TF is the R&D project of HEPS (High Energy Photon Source), it will cover all of the key technology for HEPS accelerator system and beamlines. In order to meet the small aperture vacuum chamber distributed pumping requirement, the NEG coating R&D for HEPS vacuum chamber is under the way. Getter films deposited on the inner surface of the chamber would transform the vacuum chamber from an outgassing source into a pump. The coating test bench will be shown here and coating procedure will be presented.

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TUB3IO02

Overview of Electron Source Development for High Repetition Rate FEL Facilities

ion, gun, electron, emittance

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]

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TUB3CO04

A New Thermionic RF Electron Gun for Synchrotron Light Sources

ion, gun, coupling, electron

453

S.V. Kutsaev, A.Y. Murokh, E.A. Savin, A.Yu. Smirnov, A.V. Smirnov
RadiaBeam Systems, Santa Monica, California, USA
R.B. Agustsson, J.J. Hartzell, A. Verma
RadiaBeam, Santa Monica, California, USA
A. Nassiri, Y. Sun, G.J. Waldschmidt, A. Zholents
ANL, Argonne, Illinois, USA
E.A. Savin
MEPhI, Moscow, Russia

Funding: This work is supported by the U.S. Department of Energy, Office of Basic Energy Science, under contract DE-SC0015191 and contract No. DE-AC02-06CH11357.
A thermionic RF gun is a compact and efficient source of electrons used in many practical applications. RadiaBeam Systems and the Advanced Photon Source of Argonne National Laboratory collaborate in developing of a reliable and robust thermionic RF gun for synchrotron light sources which would offer substantial improvements over existing thermionic RF guns and allow stable operation with up to 1A of beam peak current at a 100 Hz pulse repetition rate and a 1.5 μs RF pulse length. In this paper, we discuss the electromagnetic and engineering design of the cavity, and report the progress towards high power tests of the cathode assembly of the new gun.

Slides TUB3CO04 [2.661 MB]

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TUPOB16

A Simple Method for Measuring the Electron-Beam Magnetization

ion, solenoid, electron, emittance

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.

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WEPOA40

Construction Status of a RF-Injector with a CNT-Tip Cathode for High Brightness Field-Emission Tests

ion, electron, gun, emittance

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.

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WEPOA42

RF Design of a 1.3-GHz High Average Beam Power SRF Electron Source

ion, gun, electron, simulation

789

N. Sipahi, S. Biedron, S.V. Milton
CSU, Fort Collins, Colorado, USA
I.V. Gonin, R.D. Kephart, T.N. Khabiboulline, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

There is a significant interest in developing high-average power electron sources, particularly those integrated with Superconducting Radio Frequency (SRF) accelerator systems. Even though there are examples of high-average-power electron sources, they are not compact, highly efficient, or available at a reasonable cost. Adapting the recent advances in SRF cavities, RF power sources, and innovative solutions for an SRF gun and cathode system, we have developed a design concept for a compact SRF high-average power electron linac. This design will produce electron beams with energies up to 10 MeV. In this paper, we present the design results of our cathode structure integrated with modified 9-cell accelerating structure.

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WEPOA62

The Center for Bright Beams

ion, brightness, electron, cavity

830

J.R. Patterson, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Y.K. Kim
University of Chicago, Chicago, Illinois, USA

Funding: National Science Foundation award PHY-1549132.
The Center for Bright Beams (CBB) is a new National Science Foundation-supported Science and Technology Center. CBB's research goal is to increase the brightness of electron beams while reducing the cost and size of key technologies. To achieve this, it will augment the capabilities of accelerator physicists with those of physical chemists, materials scientists, condensed matter physicists, plasma physicists, and mathematicians. This approach has the potential to increase the brightness of electron sources through better photocathodes, the efficiency and gradient of SRF cavities through deeper understanding of superconducting compounds and their surfaces, and better understanding of beam storage and transport and the associated optics by using new mathematical techniques.

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WEA4CO05

Accelerator Physics Design Requirements and Challenges of RF Based Electron Cooler LEReC

ion, electron, cavity, emittance

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]

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WEPOB11

Tuning of the APS Linac Accelerating Cavities After Structural Re-Alignment

ion, linac, cavity, photon

910

T.L. Smith, G.J. Waldschmidt
ANL, Argonne, Illinois, USA

A new S-band LCLS type Photo-cathode (PC) gun was recently installed in the APS linac. As a consequence, it was recognized that many of the linac accelerating structures were out of their 1mm straightness tolerances. In order to reduce the effects of wakefield on the beam, several of the misaligned structures were straightened. This paper discusses the bead-pull RF measurements, the effect of the straightening efforts on rf and the cell to cell retuning efforts that were performed.

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WEPOB19

Summary of Cs2te Photocathode Performance and Improvements in the High-Gradient, High-Charge AWA Drive Gun

ion, gun, operation, wakefield

934

E.E. Wisniewski, S.P. Antipov, M.E. Conde, D.S. Doran, W. Gai, C.-J. Jing, W. Liu, J.G. Power, J.Q. Qiu, C. Whiteford
ANL, Argonne, Illinois, USA
S.P. Antipov, C.-J. Jing, J.Q. Qiu
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: Argonne, a U.S.A. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357.
The AWA L-band, high-charge photoinjector for the 70 MeV drive beamline has been operating for almost 3 years at the Argonne Wakefield Accelerator (AWA) facility. at Argonne National Laboratory (ANL). The gun operates at high-field (85 MV/m peak field on the cathode) and has a high quantum efficiency (QE) Cesium telluride photocathode with a large area (30 mm diameter). It produces high-charge, short pulse, single bunches (Q > 100 nC) as well as long bunch-trains (Q > 600 nC) for wakefield experiments (high peak current). During the first two years of operation, photocathode performance was evaluated and areas of improvement were identified. After study, consideration and consultation, steps were taken to improve the performance of the photocathode. So far, in total, three photocathodes have been fabricated on-site, installed and operated in the gun. Improvements made to the photocathode plug, vacuum system, and gun operation are detailed. The results include vastly improved conditioning times, better cathode performance, and QE above 4% for over 11 months.

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WEPOB25

Analytical Modeling of Electron Back-Bombardment Induced Current Increase in Un-Gated Thermionic Cathode Rf Guns

ion, gun, electron, simulation

953

J.P. Edelen
Fermilab, Batavia, Illinois, USA
J.R. Harris
Directed Energy Directorate, Air Force Research Laboratory, Albuquerque, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA
Y. Sun
ANL, Argonne, Illinois, USA

In this paper we derive analytical expressions for the output current of an un-gated thermionic cathode RF gun in the presence of back-bombardment heating. We provide a brief overview of back-bombardment theory and discuss comparisons between the analytical back-bombardment predictions and simulation models. We then derive an expression for the output current as a function of the RF repetition rate and discuss relationships between back-bombardment, field-enhancement, and output current. We discuss in detail the relevant approximations and then provide predictions about how the output current should vary as a function of repetition rate for some given system configurations.

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WEPOB26

Observation of Repetition-Rate Dependent Emission From an Un-Gated Thermionic Cathode Rf Gun

ion, gun, electron, experiment

956

J.P. Edelen
Fermilab, Batavia, Illinois, USA
J.R. Harris
Directed Energy Directorate, Air Force Research Laboratory, Albuquerque, USA
J.W. Lewellen
LANL, Los Alamos, New Mexico, USA
Y. Sun
ANL, Argonne, Illinois, USA

Recent work at Fermilab in collaboration with the Advanced Photon Source and members of other national labs, designed an experiment to study the relationship between the RF repetition rate and the average current per RF pulse. While existing models anticipate a direct relationship between these two parameters we observed an inverse relationship. We believe this is a result of damage to the barium coating on the cathode surface caused by a change in back-bombardment power that is unaccounted for in the existing theories. These observations shed new light on the challenges and fundamental limitations associated with scaling an un-gated thermionic cathode RF gun to high average current.

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WEPOB29

Modeling of Dark Current Generation and Transport Using the IMPACT-T Code

ion, electron, cavity, space-charge

964

J. Qiang, K. Hwang
LBNL, Berkeley, California, USA

Dark current from unwanted electrons in photoinjector can present significant danger to the accelerator operation by causing damage to photocathode and power deposition onto conducting wall. In this paper, we present numerical models of dark current generation from the field emission and from the electron impact ionization of the residual gas that were recently developed in the IMPACT-T code. We also report on the application of above numerical model to an LCLS-II like photoinjector.

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WEPOB49

LCLS Injector Laser Profile Shaping Using Digital Micromirror Device

laser, ion, electron, target

1001

S. Li
Stanford University, Stanford, California, USA
S.C. Alverson, D.K. Bohler, A.R. Fry, S. Gilevich, Z. Huang, A. Miahnahri, D.F. Ratner, J. Robinson, F. Zhou
SLAC, Menlo Park, California, USA

In the Linear Coherent Light Source (LCLS) at SLAC, the injector laser plays an important role as the source of the electron beam for the Free Electron Laser (FEL). The emittance of the beam is highly related to the transverse profile of the injector laser. Currently the LCLS injector laser has undesired features, such as hot spots, which carry over to the electron beam. These undesired features increase electron emittance, degrade the FEL performance, and complicate operations. The injector laser shaping project at LCLS aims to produce arbitrary electron beam profiles, such as cut-Gaussian, uniform, and parabolic, and to study the effect of spatial profiles on beam emittance and FEL performance. Effectively it also allows easy transition between the two spare lasers, where the operators can use the spatial shaper to achieve identical profiles for the two lasers. In this paper, we describe the experimental methods to achieve laser profile shaping and electron beam profile shaping respectively, and demonstrate promising results.

Poster WEPOB49 [1.850 MB]

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WEPOB55

Simulation of Stray Electrons in the RHIC Low Energy Cooler

ion, electron, cavity, SRF

1012

J. Kewisch
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.
The Low Energy RHIC electron Cooler, under construction at BNL, accelerates electrons with a 400 kV DC gun and a 2.2 MeV SRF booster cavity. Electrons which leave the cathode at the wrong time will not be accelerated to the correct energies and will not reach the beam dump at the end of the accelerator. Thy may impact the beam pipe after incorrect deflection in dipoles or after being slowed down longitudinally in the booster while the transverse momentum is not affected. In some cases their direction is reversed in the booster and they will impact the cathode. We simulated the trajectories of these electrons using the GPT tracking code. The results are qualitative, not quantitative, since the sources and numbers of the stray electrons are unknown.

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WEPOB58

Cathode Puck Insertion System Design for the LEReC Photoemission DC Electron Gun

ion, gun, vacuum, insertion

1021

C.J. Liaw, V. De Monte, L. DeSanto, K. Hamdi, M. Mapes, T. Rao, A.N. Steszyn, J.E. Tuozzolo, J. Walsh
BNL, Upton, Long Island, New York, USA
K.W. Smolenski
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. DOE.
The operation of LEReC is to provide an electron cooling to improve the luminosity of the RHIC heavy ion beam at lower energies in a range of 2.5-25 GeV/nucleon. The electron beam is generated in a DC Electron Gun (DC gun) designed and built by the Cornell High Energy Synchrotron Source Group. This DC gun will operate around the clock for at least two weeks without maintenance. This paper presents the design of a reliable cathode puck insertion system, which includes a multi-pucks storage device, a transfer mechanism, a puck insertion device, a vacuum/control system, and a transport scheme.

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WEPOB59

Performance of CEC Pop Gun During Commissioning

ion, gun, laser, cavity

1024

I. Pinayev, W. Fu, Y. Hao, M. Harvey, T. Hayes, J.P. Jamilkowski, Y.C. Jing, P. K. Kankiya, D. Kayran, R. Kellermann, V. Litvinenko, G.J. Mahler, M. Mapes, K. Mernick, K. Mihara, T.A. Miller, G. Narayan, M.C. Paniccia, W.E. Pekrul, T. Rao, F. Severino, B. Sheehy, J. Skaritka, K.S. Smith, J.E. Tuozzolo, E. Wang, G. Wang, W. Xu, A. Zaltsman, Z. Zhao
BNL, Upton, Long Island, New York, USA
I. Petrushina
SUNY SB, Stony Brook, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The Coherent Electron Cooling Proof-of-Principle (CeC PoP) experiment employs a high-gradient CW photo-injector based on the superconducting RF cavity. Such guns operating at high accelerating gradients promise to revolutionize many sciences and applications. They can establish the basis for super-bright monochromatic X-ray and gamma ray sources, high luminosity hadron colliders, nuclear waste transmutation or a new generation of microchip production. In this paper we report on our operation of a superconducting RF electron gun with a high accelerating gradient at the CsK2Sb photo-cathode (i.e. ~ 20 MV/m) generating a record-high bunch charge (above 4 nC). We give short description of the system and then detail our experimental results.

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WEPOB67

K2CsSb Photocathode Performance in QWR SRF Gun

ion, gun, multipactoring, vacuum

1042

E. Wang, Y. Hao, Y.C. Jing, V. Litvinenko, I. Pinayev, T. Rao, J. Skaritka, G. Wang, T. Xin
BNL, Upton, Long Island, New York, USA

In 2016 run of Coherent Electron Cooling, we have successfully tested the performance of a number of K2CsSb cathodes. These cathodes with QE of 6%-10% were fabricated in Instrumentation Division, a few miles away, transported to RHIC tunnel under UHV conditions, attached to the CeC gun, kept in storage, and inserted in the gun as needed. A maximum bunch charge of 4.6 nC was generated in the gun when the QE was 1.8 %. With careful conditioning at increasing accelerating fields, it was possible to maintain the QE of several cathodes for more than a week. For the cathodes that experienced degradation, the primary cause was multipacting when the power into the gun was increased. In the initial runs, the entire 20 mm substrate face was coated with the cathode material causing cathode induced multipacting. For subsequent measurements, the substrate was masked to coat only the central 9 mm of the substrate. By optimizing the procedure for boosting the power to the gun and covering all viewports to minimize dark current, we were able to minimize QE degradation. In this paper we discuss the cathode preparation, transfer to the gun and operational experience with the cathodes in 112 MHz gun.

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THA2CO03

New 1.4 Cell RF Photoinjector Design for High Brightness Beam Generation

ion, brightness, laser, electron

1083

E. Pirez, P. Musumeci
UCLA, Los Angeles, California, USA
D. Alesini
INFN/LNF, Frascati (Roma), Italy
J.M. Maxson
Cornell University, Ithaca, New York, USA

Funding: This work was partially funded by NSF grant 145583
The new electromagnetic and mechanical designs of the S-band 1.4 cell photoinjector are discussed. A novel fabrication method is adopted to replace the brazing process with a clamping technique achieving lower breakdown probability. The photoinjector is designed to operate at a 120 MV/m gradient and an optimal injection phase of 70 degrees to improve the extraction field by a factor of 1.9 compared to standard 1.6 cell designs with the same peak field. New geometries and features are implemented to improve beam quality for the demand of high brightness beam applications.

Slides THA2CO03 [2.444 MB]

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THPOA32

Sensitivity of the Microbunching Instability to Irregularities in Cathode Current in the LCLS-II Beam Delivery System

ion, bunching, undulator, emittance

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.

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THPOA42

3D Modeling and Simulations of Electron Emission From Photocathodes With Controlled Rough Surfaces

ion, electron, simulation, scattering

1187

D.A. Dimitrov, G.I. Bell, D.N. Smithe, C.D. Zhou
Tech-X, Boulder, Colorado, USA
I. Ben-Zvi, J. Smedley
BNL, Upton, Long Island, New York, USA
S.S. Karkare, H.A. Padmore
LBNL, Berkeley, California, USA

Funding: This work is supported by the US DOE Office of Science, department of Basic Energy Sciences under grant DE-SC0013190.
Developments in materials design and synthesis have resulted in photocathodes that can have a high quantum efficiency (QE), operate at visible wavelengths, and are robust enough to operate in high electric field gradient photoguns, for application to free electron lasers and in dynamic electron microscopy and diffraction. However, synthesis often results in roughness, ranging from the nano to the microscale. The effect of this roughness in a high gradient accelerator is to produce a small transverse accelerating gradient, which therefore results in emittance growth. Although analytical formulations of the effects of roughness have been developed, a full theoretical model and experimental verification are lacking, and our work aims to bridge this gap. We report results on electron emission modeling and 3D simulations from photocathodes with controlled surface roughness similar to grated surfaces that have been fabricated by nanolithography. The simulations include both charge carrier dynamics in the photocathode material and a general electron emission modeling that includes field enhancement effects at rough surfaces. The models are being implemented in the VSim code.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA42

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THPOA56

Primary Study of the Photocathode Electron Gun With a Cone Cathode and Radial Polarization Laser

ion, gun, laser, emittance

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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