03 Particle Sources and Alternative Acceleration Techniques
T02 Electron Sources

Paper	Title	Page
MOZB01	Superconducting RF Guns: Emerging Technology for Future Accelerators	4085
	J. Teichert HZDR, Dresden, Germany
	This talk should give an overview of Superconducting photo injectors (SRF guns) and focus on the present status of SRF gun development, the technical requirements and the critical issues like cavity design, photocathode integration, and emittance compensation methods.
	Slides MOZB01 [22.198 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOZB01
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MOZB02	Advances in Photocathodes for Accelerators	48
	L. Cultrera Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	This talk reviews advances in photocathode technology for accelerators: cathodes demonstrating record average currents and deliverable charge, possessing ultra-low intrinsic emittance and sub-picosecond response time. It addresses the grand challenge to combine all these useful properties into a single photoemitter - one that is being actively pursued by the research community.
	Slides MOZB02 [4.354 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOZB02
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MOPRI017	Status of AREAL RF Photogun Test Facility	620
	B. Grigoryan, G.A. Amatuni, V.S. Avagyan, H. Avdishyan, H. Davtyan, A.A. Gevorgyan, L.H. Hakobyan, M. Ivanyan, V.G. Khachatryan, E.M. Laziev, A. Lorsabyan, M. Manukyan, I.N. Margaryan, N. Martirosyan, T.H. Mkrtchyan, S. Naghdalyan, V.H. Petrosyan, H. Poladyan, V. Sahakyan, A. Sargsyan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan, V. V. Vardanyan, G.S. Zanyan CANDLE SRI, Yerevan, Armenia T.K. Sargsyan LT-PYRKAL cjsc, Yerevan, Armenia
	Advanced Research Electron Accelerator Laboratory (AREAL) is a 20 MeV laser driven RF linear accelerator which is being constructed in the CANDLE institute. The construction of phase-1 is finished and at present the machine commissioning is in progress. In phase-1 a photocathode RF gun provides a 5 MeV small emittance electron beam with the 100 pC bunch charge and variable electron bunch length from 0.5 to 8 ps. Two main operation modes are foreseen for this phase – single and multibunch regimes to satisfy experimental demands. We report the status of linac, first experience and nearest machine run schedule. The brief review of the facility, main parameters, performance and first results are presented.
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MOPRI018	Influence of Growth Method on K3Sb Photocathode Structure and Performance	624
	S.G. Schubert, T. Kamps, M. Schmeißer HZB, Berlin, Germany K. Attenkofer, J. Smedley BNL, Upton, Long Island, New York, USA E.M. Muller SBU, Stony Brook, New York, USA H.A. Padmore, J.J. Wong LBNL, Berkeley, California, USA M. Ruiz-Osés Stony Brook University, Stony Brook, USA J. Xie ANL, Argonne, Illinois, USA
	Funding: Supported by Director, OoS., OBES of US DOE, Contract DE-AC02-05CH11231, DE-AC02-98CH10886, KC0407-ALSJNTI0013, DE-SC0005713, germ. BMBF, Land Berlin, Helmholtz Assoc.. Use of CHESS by NSF, DMR-0936384. Future high brightness photoelectron sources delivering >100 mA average current call for a new generation of photocathodes. Materials which qualify for this purpose should exhibit low intrinsic emittance, long lifetime and high quantum efficiency at photon energies in the visible range of the spectrum to relax drive laser requirements. A combination of material science techniques are used to determine the influence of the growth parameters on structure and performance of photocathode materials . In-situ XRR, XRD and GiSAXS measurements were performed at the synchrotron radiation sources, NSLS and CHESS. The growth of K3Sb, a precursor material of one of the prime candidates CsK2Sb, was studied intensively to optimize this intermediate growth step in terms of quantum efficiency and roughness. Three methods, a “layer by layer” type and a “super-lattice type” were examined. K3Sb exists in two crystallographic phases, namely cubic and hexagonal. The cubic phase exhibits a higher quantum efficiency at 532 nm than the hexagonal phase and transforms more easily into CsK2Sb, tuning this phase is believed to be one of the key parameters in the CsK2Sb growth.
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MOPRI019	In-situ Characterization of K2CsSb Photocathodes	627
SUSPSNE115	use link to see paper's listing under its alternate paper code
	M. Schmeißer, A. Jankowiak, T. Kamps, S.G. Schubert HZB, Berlin, Germany S.G. Schubert BNL, Upton, Long Island, New York, USA
	Funding: Work supported by German Bundesministerium für Bildung und Forschung contract 05K12CB2 PCHB and Land Berlin. Alkali antimonide photocathodes with high quantum efficiency hold the promise of delivering electrons for high-brightness injectors. A drift type spectrometer (momentatron) was attached to the HZB preparation system to allow in-situ characterization within short time after fabrication and possibly identify correlations between growth process and cathode performance parameters.
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MOPRI020	Introducing GunLab – A Compact Test Facility for SRF Photoinjectors	630
SUSPSNE035	use link to see paper's listing under its alternate paper code
	J. Völker, R. Barday, A. Jankowiak, T. Kamps, J. Rudolph, S.G. Schubert, S. Wesch HZB, Berlin, Germany A. Ferrarotto, T. Weis DELTA, Dortmund, Germany V.I. Shvedunov MSU, Moscow, Russia I.Yu. Vladimirov MSU SINP, Moscow, Russia
	Funding: Work supported by German Bundesministerium für Bildung und Forschung (BMBF contract 05K12CB2 PCHB and 05K10PEA), Land Berlin and grants of Helmholtz Association Superconducting radio-frequency photoelectron injectors (SRF photoinjectors) are a promising electron source for high brightness accelerators with high average current and short pulse duration like FELs and ERLs. For the upcoming ERL project BERLinPro we want to test and commission different SRF photoinjectors and examine the beam performance of photocathode materials in an independent test facility. Therefore we designed GunLab to characterize the beam parameters from the SRF photoinjectors in a compact diagnostics beamline. In GunLab we want to investigate the complete 6 dimensional phase space as a function of drive laser and RF setup parameters. In this work we present the design and the estimated performance of GunLab.
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MOPRI021	Laser Systems Generating Short Polarized Electron Bunches at the S-DALINAC	633
SUSPSNE031	use link to see paper's listing under its alternate paper code
	M. Espig, J. Enders, Y. Fritzsche, A. Kaiser, M. Wagner TU Darmstadt, Darmstadt, Germany
	Funding: Supported by DFG within CRC634 and by the state of Hesse through the LOEWE center HIC for FAIR. The source of polarized electrons at the superconducting Darmstadt electron linear accelerator S-DALINAC uses photo-emission from strained-layer superlattice-GaAs and bulk-GaAs photocathodes. This system is driven by either 3 GHz gain-switched diode lasers or a short-pulse Ti:Sapphire laser system. Highly polarized electrons are generated with laser light at 780 nm, while blue laser light is used for unpolarized high-current experiments. We present the existing pulsed laser systems and the planned developments for the diode laser system, including, e.g., impedance matching of the diode lasers, gain switching with short electrical pulses and pulsing with a Mach-Zehnder modulator. The pulsed operation is aimed at generating short electron bunches (< 50 ps) at the S-DALINAC with variable repetition rates from some MHz to 3 GHz.
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MOPRI023	Simulation of the ELBE SRF Gun II	636
	P.N. Lu, A. Arnold, U. Lehnert, P. Murcek, J. Teichert, H. Vennekate, R. Xiang HZDR, Dresden, Germany
	Funding: EuCARD, contract number 227579 German Federal Ministry of Education and Research grant 05 ES4BR1/8 LA³NET, Grant Agreement Number GA-ITN-2011-289191 By combining the code of ASTRA and elegant in a user-friendly interface, a simulation tool is developed for the ELBE SRF Gun II. The photoelectric emission and first acceleration to several MeV in the gun cavity are simulated by ASTRA with a 1D Model, where the space charge effect is considered. The dependence of the beam quality on key parameters is studied, and a compromised optimization for a 77 pC beam is used for further elegant simulation of the beam transport through a dogleg and ELBE Linacs. Proper settings of the magnets and RF phases are the main targets of improving the beam quality. Up to now the best simulation result is an electron bunch with the energy of 47 MeV, energy spread of 66 keV, bunch length of 0.35 ps and transverse emittance of 1.9 μm and 2.7 μm in the two perpendicular directions.
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MOPRI024	NEA-GaAs (Cs, O) Photocathodes for the ELBE SRF Gun	639
	R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate HZDR, Dresden, Germany
	Funding: supported by the European Community under the FP7 programme (EuCARD-2, contract number 312453, and LA3NET, contract number 289191), and by the BMBF grant 05K12CR1. At HZDR a preparation chamber for NEA-GaAs (Cs, O) has been built and commissioned. GaAs is the next photocathode material for the ELBE SRF gun, which has been successfully operated with Cs2Te layer in last years. GaAs At HZDR a preparation chamber for NEA-GaAs (Cs, O) has been built and tested. GaAs is the next photocathode material for the ELBE SRF gun, which has been successfully operated with Cs2Te photocathode in last years. GaAs photocathodes are advantageous because of their high quantum efficiency (QE) with visible light and the extensive experiences of their use in DC guns. Furthermore, GaAs photocathodes provide the possibility to realize a polarized SRF gun in the future. In this presentation we will introduce the new preparation system and the first results of the GaAs tests. The new transfer system under construction will be also presented.
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MOPRI025	Recent Improvement of Cs2Te Photocathodes at HZDR	642
	R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate HZDR, Dresden, Germany
	Funding: Work supported by the European Community-Research Infrastructure Activity (EuCARD, contract number 227579), and the support of the German Federal Ministry of Education and Research grant 05 ES4BR1/8. The SRF gun has been successfully operated for the radiation source ELBE at HZDR. To achieve higher current and lower beam emittance, a new niobium cavity with superconducting solenoid and a new 13 MHz laser have been recently developed. For this reason, better photocathodes with high quantum efficiency are urgently in demand. In this work we improve the present Cs2Te preparation system for cleaner environment and more precise stoichiometric control than before. A new mask is designed to prevent cesium pollution of the cathode body. Instead of Kapton only alumina ceramics are used for isolation, and the cathode plugs are degassed at higher temperature. New evaporators are installed and tested to obtain an accurate deposition rate. Furthermore, the cathode transfer system is thoroughly cleaned for a better vacuum condition.
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MOPRI026	Complete Simulation of Laser Induced Field Emission from Nanostructures Using a DGTD, PIC and FEM Code	645
	A. Fallahi, F.X. Kärtner CFEL, Hamburg, Germany K.K. Berggren, R. Hobbs, F.X. Kärtner, P.D. Keathley, M.E. Swanwick, L.F. Velasquez-Garcia, Y. Yang MIT, Cambridge, Massachusetts, USA
	Funding: DARPA contract number N66001-11-1-4192 and the Center for Free-Electron Laser Science, DESY Hamburg. We present a general and efficient numerical algorithm for studying laser induced field emission from nanostructures. The method combines the Discontinuous Galerkin Time Domain (DGTD) method for solving the optical field profile, the Particle-In-Cell (PIC) method for capturing the electron dynamics and the Finite Element Method (FEM) for solving the static field distribution. The charge distribution is introduced to the time-domain method based on a modified Fowler-Nordheim field emission model, which accounts for the band-bending of the charge carriers at the emitter surface. This algorithm is capable of considering various effects in the emission process such as space-charge, Coulomb blockade and image charge. Simulation results are compared with experimental findings for optically driven electron emission from nanosharp Si-tips.
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MOPRI027	Dark Current Studies at Relativistic Electron Gun for Atomic Exploration – REGAE	649
	H. Delsim-Hashemi, K. Flöttmann DESY, Hamburg, Germany
	Electron diffraction is a tool for exploring structural dynamics of matter. The scattering cross section is orders of magnitude higher for electrons than for X-rays so that only a small number of electrons is required to achieve comparable results. However, the required electron beam quality is extraordinary. To study e. g. proteins a coherence length of 30 nm is required which translates into a transverse emittance of 5 nm at a spot size of 0.4mm. In addition short bunch lengths down to 10 fs and a temporal stability of the same order are required in order to study chemical reactions or phase transitions in pump probe type experiments. These are challenging parameters for an electron source, which demand improvements at many frontiers. Dark current degrades contrast of diffraction patterns in all experiments. Understanding dark-current generation and propagation can lead to better methods to decrease it. In this paper dark current studies that are performed at REGAE will be presented.
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MOPRI028	Different Countermeasures of Electron Amplification in the Photocathode Unit	652
	E.T. Tulu, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany A. Arnold HZDR, Dresden, Germany
	Funding: Federal Ministry for Research and Education BMBF; Project: 05K2013-HOPE Superconducting radio frequency (SRF) structures may be subjected to electron multipacting (MP). The electrons emitted from one of the structure’s wall under certain conditions are accelerated by the RF field, thereby they may impact the wall again based on the field pattern in the structure. Accordingly the number of electrons increases exponentially caused by secondary electron emission*. The latter depends on the secondary emission coefficient of the surface material and the electron trajectory in the device under study**. This phenomenon limits the accelerating gradient in the cavity, moreover, it might cause an impair of RF components and distortion of the RF signal. Therefore, there should be an efficient countermeasure to suppress MP in order to boost the performance of the SRF gun. In this paper, three techniques of suppression of MP from the vicinity of the cathode, such as DC-bias, geometric modification and the microstructure of the cathode's surface, in the Rossendorf SRF gun are presented. The simulation has been done using CST Microwave Studio® and CST Particle Studio®***. Eventually, the efficient suppression method would be chosen for this particular case. * H.Padamsee, J. Knobloch and T. Hays, 1998, Ch. 10. ** E. T. Tulu, A. Arnold and U. van Rienen, 16th International Conference on SRF, Paris, France, 2013. *** CST AG, http://www.cst.com.
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MOPRI029	Spectrometer for Laser-pulsed Electrons from Field Emission Cathodes	655
	S. Mingels, B. Bornmann, D. Lützenkirchen-Hecht, G. Müller, V. Porshyn Bergische Universität Wuppertal, Wuppertal, Germany
	Funding: German Federal Ministry of Education and Research (BMBF). Project number: 05K13PX2. In order to develop highly brilliant, pulsed electron sources based on photo-induced field emission (PFE), which combines advantages of photo and field emission (FE), a new measurement system was constructed at BUW*. In an UHV system the electrons are extracted from a cold cathode by a mesh electrode under pulsed laser illumination (3.5 ns, 10 Hz, 0.5 – 5.9 eV, > 0.3 mJ) and so far analyzed by a CW-spectrometer. Quantum efficiency investigations of flat metal (Au, Ag of different surface orientations) and semiconductor crystals (n- and p-Si**, GaN) yielded the expected work functions and revealed first hints for PFE effects. However, the kinetic energy of the electrons could not be measured with the CW-spectrometer. In addition, the achievable electric field (< 20 MV/m) was limited by parasitic FE. Hence, the system is presently upgraded with a spectrometer (resolution < 3 meV) that can handle electron pulses and a dust reduced environment is installed at the load lock. First results acquired with the upgraded apparatus on PFE cathodes will be presented at the conference. * B. Bornmann et al., Rev. Sci. Instrum. 83, 013302 (2012). ** S. Mingels et al., Proc. FEL2013, New York, USA, p. 339.
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MOPRI030	Basic Design of a 20K C-band 2.6-cell Photocathode RF Gun	658
	T. Tanaka, M. Inagaki, K. Nakao, K. Nogami, T. Sakai LEBRA, Funabashi, Japan M.K. Fukuda, T. Takatomi, J. Urakawa, M. Yoshida KEK, Ibaraki, Japan T.S. Shintomi Nihon University, Tokyo, Japan
	Funding: This research was supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). A cryocooled C-band photocathode RF gun operating at 20K is under design at Nihon University. The RF gun is of BNL-type 2.6-cell pillbox cavity with a resonant frequency of 5712 MHz. With high-purity Oxygen-free copper used as the cavity material, the quality factor of the cavity is expected to be approximately 60000 from theoretical prediction of the anomalous skin effect at low temperatures. Considering the cooling capacity, initial operation of the RF gun is assumed at a duty factor of 0.01%. The cavity elements designed for low-power test is in preparation for machining. The low-power test at room temperature is scheduled early spring in 2014 before assembled at KEK by means of diffusion bonding technique. Since it is intended for the basic understanding and measurements of low temperature RF properties, the cavity is not equipped with structures for the photocathode assembling or the RF input coupler. The cavity design and the results of RF properties measured at room temperature before diffusion bonding will be reported.
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MOPRI031	Multi-alkali Photocathode R&D	661
	Y. Seimiya, M. Kuriki, N. Yamamoto HU/AdSM, Higashi-Hiroshima, Japan
	Multi-alkali photocathode has excellent features: high quantum efficiency, long lifetime, and excitation by visible light, for example green laser. The multi-alkali cathode is considered to be one of the best candidate of the high brightness electron source of the advanced electron accelerator such as ERL and FEL. We study conditions of multi-alkali evaporations, such as thicknesses, substrate temperature, and evaporation rate, and examine the cathode performances, such as quantum efficiency and extractable current density. Antimony (Sb), potassium (K), and cesium (Cs) are used in our evaporation system.
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MOPRI032	A STUDY ON ROBUSTNESS OF NEA-GAAS PHOTOCATHODE*	664
	K. Uchida, R. Kaku, M. Kuriki, K. Miyoshi, Y. Seimiya, N. Yamamoto HU/AdSM, Higashi-Hiroshima, Japan H. Iijima Tokyo University of Science, Tokyo, Japan
	Electron source is one of the most important component in the advanced linac. There is a strong demand on the high performance cathode, such as small emittance, high brightness, and short pulse generation. NEA-GaAs photo-cathode is a unique technology which is capable for generating highly polarized and extremely low emittance beam. Quantum efficiency (QE) of the cathode is high in near IR region, so it is favor to generate a high current density beam. These advantages are originated to the Negative Electron Affinity (NEA) surface, but it is fragile so the operational lifetime is limited. A study on a robust NEA surface cathode is reported. According to the hetero-junction model, Cs-Te thin film deposited on GaAs forms a robust NEA surface. We performed the Cs-Te evaporation experiment on a clean GaAs cathode and measured QE spectra. We found that some sample showed a high quantum efficiency up to 900nm wavelength which strongly suggested a NEA surface formation.
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MOPRI033	Quasi-traveling Wave Side Couple RF Gun Commissioning for SuperKEKB	667
	T. Natsui, Y. Ogawa, M. Yoshida, X. Zhou KEK, Ibaraki, Japan
	We are developing a new RF gun for SuperKEKB. High-charge low-emittance electron and positron beams are required for SuperKEKB. We will generate 7.0 GeV electron beam at 5 nC 20 mm-mrad by J-linac. In this linac, a photo cathode S-band RF gun will be used as the electron beam source. For this reason, we are developing an advanced RF gun. New RF gun which has two side coupled standing wave field is developed. We call it quasi traveling wave side couple RF gun. This gun has a strong focusing field at the cathode and the acceleration field distribution also has a focusing effect. Beam commissioning has been started with the new RF gun. I will report the result of beam commissioning.
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MOPRI034	Development of temporal response measurement system for transmission-type spin-polarized photocathodes	670
	T. Inagaki, M. Hosaka, Y. Takashima, N. Yamamoto Nagoya University, Nagoya, Japan M. Adachi KEK, Ibaraki, Japan X.G. Jin Institute for Advanced Research, Nagoya, Japan M. Katoh, T. Konomi UVSOR, Okazaki, Japan Y. Okano IMS, Okazaki, Japan
	Spin polarized electron beam is essential for "International Linear Collider". In Nagoya University, transmission-type spin-polarized photocathodes have been developed, and the quantum efficiency of 0.5 % and the polarization of 90 % were achieved*,**. Recently, we succeeded in making the active layer several times thicker with keeping the spin polarization on the GaAs/GaAsP strain-compensated superlattice photocathode***. Increasing the thickness of the active layer is very advantageous for high quantum efficiency, but might be disadvantageous for pulse response. In order to investigate the pulse response, we have developed a pulse length measurement system by using an RF deflecting cavity. In the measurement, magnetic field induced on the beam axis kicks electron pulse transversely and the pulse length is projected to the transverse plane, which is measured by knife-edge method. The pump laser pulses are provided by a Ti:sapphire laser oscillator. By using a pulse stretcher, the pulse width of the pump laser can be changed in the range between 130 fs and 20 ps. In the poster session, we will describe the details of the measurement system and the most recent experimental results. * T. Nakanishi, The XXI International LINAC Conference(1998) ** Xiuguang Jin, Japanese Journal of Applied Physics 51 (2012) 108004 *** Xiuguang Jin, Applied Physics Express 6 (2013) 015801
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MOPRI035	Development of the Photocathode LiTi2O4 and Evaluations of the Initial Emittance	673
	R. Inagaki, M. Hosaka, Y. Takashima, N. Yamamoto Nagoya University, Nagoya, Japan T. Hitosugi, S. Shiraki Tohoku Uneversity, WPI-AIMR, Sendai, Japan E. Kako, Y. Kobayashi, S. Yamaguchi KEK, Ibaraki, Japan M. Katoh, T. Konomi, T. Tokushi UVSOR, Okazaki, Japan Y. Okano IMS, Okazaki, Japan
	In UVSOR, the X-ray free electron laser (XFEL) based on linear accelerator with high pulse repetition about 1MHz has been designed as a candidate for the next radiation sources. We thought a combination of superconducting RF cavity and photocathode is an optimal electron gun for the new accelerator. For this electron gun, we propose a back-illuminated multi-alkali* photocathode with transparent superconductor LiTi2O4**. The reason for using LiTi2O4 is to reflect RF by using feature of penetration depth of superconductor, which is defined from London equation. This feature protects optical components from RF damage. However, LiTi2O4 is a new material and properties are not clear. We have measured the basic properties of this photocathode, such as magnetic susceptibility measurement and photoelectron spectrometry, etc. In this conference, we will explain the detail of the concept and advantage of this cathode, and show the result measured about the basic properties of this photocathode focusing on the initial emittance measurement. * A. V. Lyashenko et al. JINST 4 P07005 (2009) ** Kumatani et al. APL 101 (2012) 123103″
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MOPRI036	Pulse Radiolysis Using Terahertz Probe Pulses	676
	K. Kan, M. Gohdo, T. Kondoh, K. Norizawa, I. Nozawa, A. Ogata, T. Toigawa, J. Yang, Y. Yoshida ISIR, Osaka, Japan
	Pulse radiolysis, which utilizes a pump electron beam and a probe pulse, is a powerful tool that can be used for the time-resolved observation of ultrafast radiation-induced phenomena. Recently, double-decker pulse radiolysis* using visible probe pulses were demonstrated based on a photocathode RF gun driven by two UV pulses, which enabled synchronized pump electron beam and visible probe pulses. In this study, pulse radiolysis using terahertz (THz) probe pulses which were realized by the “double-decker” electron beams and dynamics of transient quasi-free electrons in semiconductors are presented. * K. Kan et al., Rev. Sci. Instrum. 83, 073302 (2012).
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MOPRI037	Development of Iridium Cerium Photocathode for the Generation of High-Charge Electron Beam	679
SUSPSNE033	use link to see paper's listing under its alternate paper code
	D. Satoh TIT, Tokyo, Japan N. Hayashizaki RLNR, Tokyo, Japan T. Natsui, M. Yoshida KEK, Ibaraki, Japan
	We developed an iridium cerium cathode material made by new production method for multi-purpose electron source. For multi-purpose electron source, we focused on the Ir5Ce compound which has a high melting point (> 2100 K) and a low work function (2.57 eV). This material has some excellent properties as both a thermionic cathode and a photocathode. For example, Ir5Ce thermionic cathode can generate one-order higher electrical current than a LaB6 cathode at the same temperature. Another advantage is that an Ir5Ce thermionic cathode has a lifetime two orders longer than that of a LaB6 thermionic cathode under the same conditions. Moreover, we discovered that this material has a reasonably high quantum efficiency (2.70 × 10−3 @213nm at 1000°C) and long-lifetime (> LaB6) as a photocathode. Our research shows that Ir5Ce compound is optimum material for a thermionic cathode and photocathode. We focused on this good emission properties under the high temperature and we tried to develop a backside electron beam heating system and demonstrate a laser pre-pulse heating for a high current thermionic gun system or high charge photocathode gun.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI037
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MOPRI038	Study on Quantum Efficiency of NEA-GaAs with Various Thermal Treatments; The Increase in Quantum Efficiency by the Low Temperature Treatment.	682
	K. Hayase, R. Chiba, H. Iijima, Y. Inagaki, T. Meguro Tokyo University of Science, Tokyo, Japan
	Negative electron affinity (NEA) surface are formed by deposition of Cs atoms on p-GaAs, and the drastic increase in the electron emission is observed by the Yo-Yo method. It is necessary to remove oxide layers of GaAs surface for the NEA surface formation, therefore the thermal treatment was carried out prior to the NEA activation. We have discussed the quantum efficiency (QE) with different thermal history. GaAs surfaces cleaned with organic solvents were thermally treated with the temperature sequence of 773K, 823K, and 723K. The NEA activation was carried out at every temperature. The QE less than 1% was obtained with 773K of treatment temperature on the initial surface. Then the QE increased at 10% after treatment at higher 823K. Successive increase of the QE to 13% was observed with a reduced temperature treatment at 723K. The GaAs surfaces after the thermal treatment in the high temperature region with the NEA activation are different from the as-cleaned-GaAs surfaces probably in stoichiometry or morphology due to desorption of As and Ga atoms. The role of thermal treatment with NEA activation is the modification of surface properties important for elevating the QE.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI038
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MOPRI039	Ultra-short Electron Bunch Generation using Energy-chirping Cell Attached RF Electron Gun	685
	K. Sakaue, Y. Koshiba, M. Mizugaki, M. Washio Waseda University, Tokyo, Japan R. Kuroda AIST, Tsukuba, Ibaraki, Japan T. Takatomi, J. Urakawa KEK, Ibaraki, Japan
	Funding: Work supported by JSPS Grant-in-Aid for Young Scientists (B) 23740203 and Scientific Research (A) 10001690 We have been developing an Energy-Chirping-Cell attached RF electron gun (ECC-RF-Gun) for generating ultra-short electron bunches. ECC-RF-Gun has extra cell at the end of gun cavity in order to chirp the bunch energy. Such a bunch can be compressed by the velocity difference though the drift space. We have already installed it to our accelerator system and successfully observed a coherent synchrotron/transition radiation at 0.3THz. It is clear that the bunch length was short enough to generate 0.3THz, which corresponds to less than 500fs bunch length was achieved if we assume the gaussian shape. In this conference, the principle of ECC-RF-Gun, the recent results of bunch length measurement and future prospective will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI039
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MOPRI040	Design and Analysis of an Electron Beam in an Electron Gun for X-Ray Radiotherapy	688
SUSPSNE032	use link to see paper's listing under its alternate paper code
	J.C. Lee, J.-S. Chai, M. Ghergherehchi, H.S. Kim, Y.S. Lee, S. Shin, Y.H. Yeon SKKU, Suwon, Republic of Korea B.N. Lee KAERI, Dae-jeon, Republic of Korea
	Funding: This work was supported by (IT R&D program of MSIP/KEIT [10043897] and MOTIE [13-DU-EE-12]) in KOREA. Electron linear accelerators are used as x-ray generators for diagnosing the human body. In this paper conceptual design of electron beam for compact electron gun was calculated by using EGN2w and CST-Particle Studio codes. The structure of the electron gun was used for Pierce and diode type and the specification of electron beam was selected as 500 cGy/min. Specifications of designed electron gun were focused on current, beam size and normalized emittance. Optimized beam current, diameter and normalized emittance are 226.88 mA, 0.689 mm (Full width) and 1.03π mm• mrad, respectively by using two simulation codes. Accuracy of simulation was verified by comparison of emitted beam current which has error of 0.74%. * Subhash C. Sharma et al., Journal of applied clinical medical physics, 8, 3 (2007) 119-125. * Yuichiro Kamino et al., Med. Phys. 34 (2007) 1797-1808.
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MOPRI041	Electrons Injectors with Cathode Diameter of 6/15mm and New Cup Energy Input on the Wave E11 for Accelerators	692
	K.G. Simonov, E.A. Alkhimenko, T.A. Batkova, S.I. Grishin, A.V. Mamontov, G.I. Pravdikovskaya, E.A. Stroykov ISTOK, Moscow Region, Russia A.I. Shapovalov MRTI RAS, Moscow, Russia
	RPC "Istok" has created a number of electron injectors with voltage of 20-60kV and cathode diameter of 6-15mm of diode and triode designs. Injectors use the impregnated cathodes; the injector design allows rapid replacement of cathode assemblies. Injectors have been widely used in linear electron accelerators in Russia and Ukraine, in particular, in the sterilization accelerator center of JSC "MRTI RAS", Moscow, in the accelerator of the Russian Eye and Plastic Surgery Centre, Ufa. Have been proposed new input energy windows on the E11 wave, providing significant levels of transmission of the pulse power at high average power levels. Have been created two types of windows at 10-cm range, in which the ceramic disk made of ecologically clean alumina ceramic with diameter of 103mm and thickness of 13mm is used. In the first type of windows the heat transfer is provided from the peripheral portion, and in the second type of window – both from peripheral and central portions of the ceramic disk. These windows are used in accelerator of FSUE "NIIEFA" (St.Petersburg), installed at Izhora mill for testing the welding seals of atomic reactors and in accelerator of JSC "MRTI RAS".
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MOPRI042	Recent Developments at the High-charge PHIN Photoinjector and the CERN Photoemission Laboratory	695
	C. Heßler, E. Chevallay, S. Döbert, V. Fedosseev, I. Martini, M. Martyanov, A. Perillo Marcone, Sz. Sroka CERN, Geneva, Switzerland
	The high-charge PHIN photoinjector has originally been developed to study the feasibility of a photoinjector option for the drive beam of the CLIC Test Facility 3 (CTF3) at CERN and is now being used to investigate the feasibility of a drive beam photoinjector for CLIC. In this paper recent R&D efforts to improve the parameters of the existing system towards CLIC requirements will be discussed. This includes studies of a feedback loop for intensity stabilization, the upgrade of the PHIN vacuum system and the planned upgrade of the driving laser system. For photocathode production and R&D a dedicated photoemission laboratory is available at CERN. To increase the production rate of photocathodes and the availability of the photoemission lab for other studies, an upgrade of the photocathode preparation system with a load-lock system is under study and will also be presented.
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MOPRI043	Study of a C-band Standing-wave Gun for the SwissFEL Injector	698
SUSPSNE034	use link to see paper's listing under its alternate paper code
	M. Schaer, S. Bettoni, A. Citterio, P. Craievich, M. Negrazus, L. Stingelin, R. Zennaro PSI, Villigen PSI, Switzerland
	The baseline design of the SwissFEL injector foresees the "PSI Gun 1", a 2.6-cell RF photo-cathode gun operating at S-band frequency, as the electron source. In this paper a new design is presented where a 5.6-cell C-band gun could replace the PSI Gun 1 with no impact on the rest of the injector setup. A conservative maximum gradient of 135 MV/m at the cathode is assumed which drives the electron beam faster into the relativistic regime and therefore allows to tolerate larger charge densities. The presented solution also foresees a coaxial RF coupling from the cathode side in order to place the gun solenoid as near to the photo-cathode as possible, improving the emittance compensation. Astra simulations showed that the transverse beam brightness can be doubled before the first bunch compressor preserving the low transverse emittance value as compared to the current design for the S-band injector configuration of SwissFEL.
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MOPRI044	Feasibility Study of an Ultrafast Electron Diffraction System in NSRRC	701
SUSPSNE036	use link to see paper's listing under its alternate paper code
	P. Wang, K.C. Leou NTHU, Hsinchu, Taiwan N.Y. Huang, W.K. Lau, A.P. Lee NSRRC, Hsinchu, Taiwan
	It has been suggested that the MeV beam generated from a laser-driven photo-cathode rf gun can be used for ultrafast electron diffraction (UED)*. The feasibility of operating the NSRRC photo-cathode rf gun system for ultrashort bunch generation is being investigated. The results of space-charge tracking calculations show that a low emittance, few hundred femtoseconds MeV beam with reasonable bunch charge can be generated for single shot UED experiments. In this report, a preliminary design of this UED system will be discussed. * X.J. Wang et al., in Proceedings of PAC'03, p.420.
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MOPRI045	Beam Diagnostics E-GUN Test Stand at TARLA	704
	Ç. Kaya, A.A. Aksoy, A. Aydin, V. Karakilic, Ö. Karslı, E. Kazancı, B. Koc, S. Kuday, E.Ç. Polat, I. Sara, M. Yildiz Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey S. Özkorucuklu Istanbul University, Istanbul, Turkey
	Funding: Work supported by Turkish State Planning Organization (Grant No: DPT2006K-120470) Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) facility, which is essentially proposed to generate oscillator mode FEL in 3-250 microns wavelengths range, will consist of totally normal conducting injector system with 250 keV beam energy, two superconducting RF accelerating modules in order to accelerate the beam 15-40 MeV. Continuous wave (CW) electron beam will provided by TARLA thermionic electron gun (E-GUN). Various aspects of the Thermionic EGUN test stand to deliver the necessary electron beam in terms of bunch charge, current, energy, emittance and profile for the beam diagnostic will be discussed. Primarily measurements results of electron beam energy loss and transverse orbit will be shown as well as beam image and shape measurements. On behalf of TARLA Collaboration
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MOPRI046	The Evolution of the Transverse Energy Distribution of Electrons from a GaAs Photocathode as a Function of its Degradation State	707
	L.B. Jones, B.L. Militsyn, T.C.Q. Noakes STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom H.E. Scheibler, A.S. Terekhov ISP, Novosibirsk, Russia
	The brightness of a photoelectron injector is fundamentally limited by the mean longitudinal and transverse energy distributions of the photoelectrons emitted from its photocathode, and the electron beam brightness is increased significantly if the mean values of these quantities are reduced. ASTeC have commissioned a Transverse Energy Spread Spectrometer (TESS – an experimental facility designed to measure these transverse and longitudinal energy distributions) which can be used for III-V semiconductor, alkali antimonide/telluride and metal photocathode research*. GaAs photocathodes were activated in our photocathode preparation facility (PPF)**, then transferred to TESS under XHV conditions and progressively degraded through controlled exposure to oxygen. We present commissioning data and initial measurements showing the evolution of the transverse energy distribution of electrons from GaAs photocathodes as a function of their degradation state. * Proc. FEL ’13, TUPPS033, 290-293 ** Proc. IPAC ’11, THPC129, 3185-3187
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MOPRI047	The Preparation of Atomically Clean Metal Surfaces for use as Photocathodes in Normally Conducting RF Guns	711
	T.C.Q. Noakes, A.N. Hannah, K.J. Middleman, B.L. Militsyn, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S. Mistry Loughborough University, Leicestershre, United Kingdom
	Funding: Research supported by FP7 EuCard2 http://cern.ch/eucard2 This work reports a study of various alternative metal samples as candidate materials for use as photocathodes in normally conducting RF guns. Clean surfaces were prepared using Argon ion bombardment and quantum efficiency measured using a 265 nm UV LED light source with a picoammeter for drain current monitoring. Surface composition was studied using X-ray photoelectron spectroscopy and a Kelvin probe apparatus provided work function measurements. Data was taken both before and after annealing to 200°C, a temperature that is routinely achieved during RF gun vacuum baking. Ion bombardment typically leaves a very rough surface that can have a detrimental effect on beam emittance, so further work will focus on the use of Oxygen plasma cleaning of the best candidate alternative metals. An oxygen plasma treated Copper photocathode has been shown to produce an acceptable level of quantum efficiency in the VELA accelerator at Daresbury Laboratory.
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MOPRI049	An Ultracold Electron Facility in Manchester	714
	Ö. Mete, R. Appleby, W. Bertsche, M.A. Harvey, G.X. Xia UMAN, Manchester, United Kingdom S. Chattopadhyay Cockcroft Institute, Warrington, Cheshire, United Kingdom A.J. Murray The University of Manchester, The Photon Science Institute, Manchester, United Kingdom
	An ultra-cold atom based electron source (UCAE) facility has been built in the Photon Science Institute (PSI), University of Manchester. In this paper, the key components and working principles of this source are introduced. Pre-commissioning status of this facility and the preliminary simulations results are presented.
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MOPRI050	Preliminary Study for an RF Photocathode based Electron Injector for AWAKE Project	717
	Ö. Mete, G.X. Xia UMAN, Manchester, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom S. Chattopadhyay Cockcroft Institute, Warrington, Cheshire, United Kingdom
	AWAKE project, a proton driven plasma wakefield acceleration (PDPWA) experiment is approved by CERN. The PDPWA scheme consists of a seeding laser, a drive beam to establish the accelerating wakefields within the plasma cell; and a witness beam to be accelerated. The drive beam protons will be provided by the CERN's SPS. The plasma ionisation will be performed by a seeding laser and the drive beam protons to produce the accelerating wakefields. After establishing the wakefields, witness beam, namely, electron beam from a dedicated source should be injected into the plasma cell. The primary goal of this experiment is to demonstrate acceleration of a 5-15 MeV single bunch electron beam up to 1 GeV in a 10 m of plasma. This paper explores the possibility of an RF photocathode as the electron source for this PDPWA scheme based on the existing PHIN photoinjector at CERN. The modifications to the existing design, preliminary beam dynamics simulations in order to provide the required electron beam are presented in this paper.
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MOPRI051	Measurements of the Longitudinal Energy Distribution of Low Energy Electrons	720
SUSPSNE030	use link to see paper's listing under its alternate paper code
	L.J. Devlin, O. Karamyshev, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom L.J. Devlin, O. Karamyshev, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom L.B. Jones, B.L. Militsyn, T.C.Q. Noakes STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: Work supported by STFC Cockcroft Core Grant No.ST/G008248/1 The Transverse Energy Spread Spectrometer (TESS) is an ASTeC experiment designed to measure the energy of electrons from different cathode materials. It is a dedicated test stand for future light sources. A full particle tracking code has been developed in the QUASAR Group, which simulates particle trajectories through TESS. Using this code it is possible to simulate different operational conditions of the experiment and cathode materials. The simulation results can then be benchmarked against experimental data to test the validity of the emission and beam transport model. Within this paper, results from simulation studies are presented and compared against experimental data as a collaboration within the Cockcroft Institute between ASTeC and the QUASAR Group for the case of measuring the longitudinal velocity distribution of electrons emitted from a gallium arsenide cathode using a grid structure as an energy filter.
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MOPRI053	High Repetition Rate Ultrafast Electron Diffraction at LBNL	724
	D. Filippetto, M. Mellado Munoz, H.J. Qian, F. Sannibale, W. Wan, R.P. Wells, M.S. Zolotorev 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" Here we propose to use the APEX photo-gun as novel source for time-resolved electron diffraction studies. The electron source has been designed, built and successfully tested at LBNL. It combines a high accelerating field needed for bright beams, MeV electron energy essential for time resolution in gas-phase experiments and studies of bulk processes, together with continuous (CW) operations. Ultra-short electron pulses can be delivered with a maximum repetition rate of 186 MHz, enabling new science to be studied. We report the design of a dedicated electron diffraction beamline that fits in the space constraints of the APEX tunnel. Simulations of beam properties have been carried out with a genetic optimizer, showing 100 fs time resolution. Beam jitters in energy, time and position are currently being characterized, and a mitigation strategy via fast feedback loops is discussed.
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MOPRI054	Status of the APEX Project at LBNL	727
	F. Sannibale, K.M. Baptiste, C.W. Cork, J.N. Corlett, S. De Santis, L.R. Doolittle, J.A. Doyle, D. Filippetto, G.L. Harris, G. Huang, H. Huang, R. Huang, T.D. Kramasz, S. Kwiatkowski, R.E. Lellinger, V. Moroz, W.E. Norum, C. F. Papadopoulos, G.J. Portmann, H.J. Qian, J.W. Staples, M. Vinco, S.P. Virostek, R.P. Wells, M.S. Zolotorev LBNL, Berkeley, California, USA R. Huang USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 The Advanced Photo-injector EXperiment (APEX) at the Lawrence Berkeley National Laboratory (LBNL), consists in the development of an injector designed to demonstrate the capability of the VHF gun, a normal conducting 186 MHz RF gun operating in CW mode, to deliver the brightness required by X-ray FEL applications at MHz repetition rate. APEX is organized in 3 main phases where different aspects of the required performance are gradually demonstrated. The status and future plans for the project are presented.
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MOPRI055	APEX Present Experimental Results	730
	D. Filippetto, C.W. Cork, S. De Santis, L.R. Doolittle, G. Huang, R. Huang, W.E. Norum, C. F. Papadopoulos, G.J. Portmann, H.J. Qian, F. Sannibale, J.W. Staples, R.P. Wells LBNL, Berkeley, California, USA J. Yang TUB, Beijing, People's Republic of China
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 The APEX electron source at LBNL combines high-repetition-rate and high beam brightness typical of photo-guns, delivering low emittance electron pulses at MHz frequency. Proving the high beam quality of the beam is an essential step for the success of the experiment. It would enable high repetition rate operations for brightness-hungry applications such as X-Ray FELs, and MHz ultrafast electron diffraction. A full 6D characterization of the beam phase space at the gun beam energy (750 keV) is foreseen in the first phase of the project. Diagnostics for low and high current measurements have been installed and tested, measuring the performances of different cathode materials in a RF environment with mA average current. A double-slit system allows the characterization of beam emittance at high charge and full current (mA). An rf deflecting cavity and a high precision spectrometer allow the characterization of the longitudinal phase space. Here we present the latest results at low and high repetition rate, discussing the tools and techniques used.
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MOPRI056	Design and Fabrication of a VHF - CW High Repetition Rate Electron Gun	733
	R.P. Wells, B. Ghiorso, F. Sannibale, J.W. Staples LBNL, Berkeley, California, USA T.M. Huang IHEP, Beijing, People's Republic of China
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 A high repetition rate, MHz, electron source is a key element in future FEL based light sources. The Advance Photo-injector Experiment (APEX) at Lawrence Berkeley National Laboratory (LBNL) consists of a high repetition rate 186 MHz (VHF-band) CW electron gun, 1 MHz UV laser source and the diagnostic components necessary to quantify the gun’s performance. The gun design is based on well established, conventional RF cavity design, with a couple notable exceptions. The basis for the selection of this technology, novel design features, fabrication techniques and measured cavity performance are presented.
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MOPRI057	Photoemission from III-V Semiconductor Cathodes	736
	S.S. Karkare Cornell University, Ithaca, New York, USA I.V. Bazarov, L. Cultrera, W.J. Schaff Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA X.G. Jin Institute for Advanced Research, Nagoya, Japan Y. Takeda Nagoya University, Nagoya, Japan
	Quantum efficiencies (QE) and mean transverse energies (MTE) of GaAs photocathodes grown using various techniques: metal-organic vapor phase epitaxy (MOVPE), molecular beam epitaxy (MBE), and atomic polishing have been compared and found to be identical. GaAs and GaInP based samples grown at Nagoya University were activated and measured in the Cornell ERL photoinjector. These were found to be in agreement with the samples measured at the ERL injector in KEK.
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MOPRI058	Metal Plasmonic Nanostructures Functionalized by Atomic Layer Deposition of MgO for Photocathode Applications	739
	S.V. Baryshev, S.P. Antipov, A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA M.R. Savina, A.V. Zinovev ANL, Argonne, Illinois, USA E. Thimsen University of Minnesota, Minneapolis, USA
	Funding: Euclid TechLabs LLC acknowledges support from the DOE SBIR program, grant No. DE-SC0009572. To create high current, long lasting electron sources capable of providing sub-ps bunches, new photocathode concepts are sought. Most recently, plasmonic nanostructured metal surfaces or flat metal surfaces activated by an ultrathin MgO are under great attention. We report on a photocathode design combining these two approaches. It consists of plasmonic Ag nanoparticles (NPs) functionalized by 3 MgO monolayers (MLs). Ag NPs were synthesized by an aerosol method and MgO was grown by atomic layer deposition (ALD). The NPs geometry was tuned to obtain broadband >50% absorption in the entire blue range as evidenced by UV-vis. spectroscopy. The WF of 3 MgO MLs/Ag NPs multilayer was reduced by 1 eV compared to bare NPs, from 5 to 4 eV, as evidenced by UPS and Kelvin probe. Reduction by 1 eV is maximal for this pair of materials, and agrees well with experimental and theoretical findings. While the effect on WF is indeed significant, a special handling protocol for Ag before depositing MgO is a must. It would preserve a clean Ag surface with a WF of nearly 4 eV to achieve 3 eV upon ALD of MgO. This and other issues are under study to promote photocathode applications.
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MOPRI059	Fabrication of Alkali Antimonide Photocathode for SRF Gun	742
	E. Wang, S.A. Belomestnykh, I. Ben-Zvi, D. Kayran, G.T. McIntyre, T. Rao, J. Smedley, D. Weiss, W. Xu BNL, Upton, Long Island, New York, USA I. Ben-Zvi, M. Ruiz-Osés Stony Brook University, Stony Brook, USA X. Liang SBU, Stony Brook, New York, USA H.M. Xie PKU, Beijing, People's Republic of China
	Funding: * This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE and DOE grant The first alkali antimonide photocathode was prepared and inserted into the BNL 704 MHz SRF gun. An excimer laser cleaning system was installed in a cathode deposition chamber and the cleaning technique developed previously was used in the first cathode preparation. We also demonstrated that oxidized cathode can be removed by exposing it to the same excimer laser. In this paper, we show the set up of the incorporated laser cleaning system and the QE enhancement of alkali antimony photocathode. The vacuum evolution at transport cart and QE measurement system are also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI059
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MOPRI063	Alkali Antimonide Photocathodes in a Can	745
	J. Smedley, K. Attenkofer, T. Rao, S.G. Schubert BNL, Upton, Long Island, New York, USA I. Ben-Zvi, X. Liang, E.M. Muller, M. Ruiz-Osés Stony Brook University, Stony Brook, USA J. DeFazio PHOTONIS USA Pennsylvanis, Inc., Lancaster, Pennsylvania, USA H.A. Padmore, J.J. Wong LBNL, Berkeley, California, USA J. Xie ANL, Argonne, Illinois, USA
	Funding: Work was supported by the US DOE, under Contracts DE-AC02-05CH11231, DE-AC02-98CH10886, KC0407-ALSJNT-I0013, DE-FG02-12ER41837 and DE-SC0005713. Use of CHESS is supported by NSF award DMR-0936384. The next generation of x-ray light sources will need reliable, high quantum efficiency photocathodes. These cathodes will likely be from the alkali antimonide family, which currently holds the record for highest average current achieved from a photoinjector. In this work, we explore a new option for delivering these cathodes to a machine which requires them: use of sealed commercial vacuum tubes. Several sealed tubes have been introduced into a vacuum system and separated from their housing, exposing the active photocathode on a transport arm suitable for insertion into a photoinjector. The separation has been achieved without loss of QE. These cathodes are compared to those grown via traditional methods, both in terms of QE and in terms of crystalline structure, and found to be similar.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI063
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)