FEL2014 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOB03	Phase Space Manipulations in Modern Accelerators	laser, electron, FEL, radiation	16
	D. Xiang Shanghai Jiao Tong University, Shanghai, People's Republic of China
	Funding: This work was supported by the National Natural Science Foundation of China under Grants No. 11327902. Beam manipulation is a process to rearrange beam's distribution in 6-D phase space. In many cases, a simple phase space manipulation may lead to significant enhancement in the performance of accelerator based facilities. In this paper, I will discuss various beam manipulation techniques for tailoring beam distribution in modern accelerators to meet the requirements of various applications. These techniques become a new focus of accelerator physics R&D and hold great promise in opening up new opportunities in accelerator based scientific facilities.
	Slides MOB03 [5.078 MB]

MOP021	Commissioning of a Dual-sweep Streak Camera with Applications to the ASTA Photoinjector Drive Laser	laser, timing, controls, gun	66
	A.H. Lumpkin, D.R. Edstrom, J. Ruan, J.K. Santucci Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. The high-power electron beams for the Advanced Superconducting Test Accelerator (ASTA) facility will be generated in a photoinjector based on a UV drive laser and the L-band rf photocathode (PC) gun cavity. The initial objectives of these studies were: 1) the evaluation of the amplified UV component’s bunch length and phase stability and 2) the commissioning of the laser room Hamamatsu C5680 streak camera system. We used a new readout camera based on the Prosilica GC1380 digital CCD with Gig-E readout that was compatible with our image processing tools. We observed a longer than expected UV bunch length of 4 ps σ and an unexpected peak multiplicity (with spacing of about 70 ps) in the synchronous sum of 5 UV micropulses. We have now systematically investigated the issues of whether the multiplicity was with each micropulse of the 3-MHz pulse train. We describe our extensive investigations that indicated both issues originated in the multi-pass amplifier. We have replaced the MPA with three single-pass devices, measured 3.5-ps bunch lengths without the multiplicity, and generated photoelectrons from the gun successfully.

MOP028	Field Integral Measurement System and Optical Alignment System for HUST THz-FEL	undulator, FEL, alignment, electron	80
	B. Qin, Q.S. Chen, M. Fan, Q. Fu, T. Hu, X. Lei, K.F. Liu, X. Liu, P. Tan, Y.Q. Xiong, J. Yang, L. Yang HUST, Wuhan, People's Republic of China X. Liu, Z. Ouyang, Y.B. Wang Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China Y.J. Pei USTC/NSRL, Hefei, Anhui, People's Republic of China
	A Free Electron Laser oscillator with radiation wavelength 50–100 μm is under construction in Huazhong University of Science and Technology (HUST). The linear polarization undulator with K=1.0-1.25 has been designed and manufactured by Kyma s.r.l., by using a pure permanent magnet scheme. Acceptance test bas been performed in Kyma factory with well controlled phase error and field integrals for all gaps. This paper introduces the development of an online field integrals measurement system for the undulator, using the stretched wire method. The design and considerations of the optical alignment system is described as well.

MOP088	High Repetition Rate Energy Modulator System Utilizing a Laser Enhancement Cavity	laser, electron, radiation, resonance	260
	Y. Honda KEK, Ibaraki, Japan
	A high intensity laser field can be realized at a high repetition rate using an enhancement optical cavity scheme. We propose to apply the 100GW-level laser field inside the cavity for producing a micro-bunch structure in an electron bunch. Combining this system with an ERL scheme of accelerator, it can be used for a seeded FEL at a high repetition rate of ~100MHz continuous beam. The longitudinal electric field at the center area of a higher-order transverse mode of laser can be used to modulate beam energy at a period of the laser wavelength. A 250 MeV class two-loop ERL accelerator has been proposed in KEK as a future upgrade plan of existing 35 MeV ERL test accelerator. It will be able to provide a low emittance, small energy spread, short bunch electron beam at a high repetition rate of continuous operation. We propose to apply this beam to produce a seeded VUV coherent radiation. We will discuss the feasibility of the scheme and status of the laser modulator development.

TUP008	An Analysis of Optimum Out-coupling Fraction for Maximum Output Power in Oscillator FEL	coupling, FEL, electron, laser	368
	Q.K. Jia USTC/NSRL, Hefei, Anhui, People's Republic of China
	The effect of the out-coupling fraction on the output power in oscillator FEL is analyzed. The formulas of the optimum out-coupling fraction and the corresponding maximum output power are given. They are dependent on the initial small signal gain and the passive loss rate of the light in the optical cavity. The initial comparison show that the result given by the formula agree well with the results in references.

TUP069	Cavity Length Change vs. Mirror Steering in a Ring Confocal Resonator	wiggler, FEL, operation, optics	516
	S.V. Benson JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-84-ER40150, the Office of Naval Research, and the Joint Technology Office. In principle, a ring confocal resonator allows for the use of a short Rayleigh length without the extreme sensi-tivity to mirror steering typical in a near-concentric reso-nator [1]. One possible weakness of such a resonator is that the cavity length is no longer independent of the mirror steering. This is one of the strengths of a linear resonator. In this presentation, it is shown that, in a simple 2-dimensional corner cube type ring confocal resonator, the cavity length is, in fact, not dependent on the mirror steering to first order in the mirror angles. Thus the ring-confocal resonator might be a very easy-to-operate and stable resonator for short Rayleigh range operation in FEL oscillators [1] Stephen Benson, George Neil, Michelle Shinn, Laser and Beam Control Technologies, Santanu Basu, James Riker, Editors, Proceedings of SPIE Vol. 4632 (2002).

TUP072	Present Status of Coherent Electron Cooling Proof-of-principle Experiment	electron, ion, gun, laser	524
	I. Pinayev, Z. Altinbas, D.R. Beavis, S.A. Belomestnykh, I. Ben-Zvi, K.A. Brown, J.C. Brutus, A.J. Curcio, L. DeSanto, A. Elizarov, C. Folz, D.M. Gassner, H. Hahn, Y. Hao, C. Ho, Y. Huang, R.L. Hulsart, M. Ilardo, J.P. Jamilkowski, Y.C. Jing, F.X. Karl, D. Kayran, R. Kellermann, N. Laloudakis, R.F. Lambiase, V. Litvinenko, G.J. Mahler, M. Mapes, W. Meng, R.J. Michnoff, T.A. Miller, M.G. Minty, P. Orfin, A. Pendzick, F. Randazzo, T. Rao, J. Reich, T. Roser, J. Sandberg, B. Sheehy, J. Skaritka, K.S. Smith, L. Snydstrup, A.N. Steszyn, R. Than, C. Theisen, R.J. Todd, J.E. Tuozzolo, E. Wang, G. Wang, D. Weiss, M. Wilinski, T. Xin, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA G.I. Bell, J.R. Cary, K. Paul, I.V. Pogorelov, B.T. Schwartz, A.V. Sobol, S.D. Webb Tech-X, Boulder, Colorado, USA C.H. Boulware, T.L. Grimm, R. Jecks, N. Miller Niowave, Inc., Lansing, Michigan, USA M.A. Kholopov, P. Vobly BINP SB RAS, Novosibirsk, Russia V. Litvinenko Stony Brook University, Stony Brook, USA P.A. McIntosh, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: Work supported by Stony Brook University and by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The status of FEL-based Coherent Electron Cooling Proof-of-principle Experiment at BNL is presented. The experimental set-up is comprised of a 2 MeV CW SRF electron gun and 20 MeV CW SRF linac and 8-m long helical FEL amplifier. The status of the accelerator commissioning, and progress in the construction of the helical undulator at Budker INP, is also reported

TUP074	High Power Coupled FEL Oscillators for the Generation of High Repetition Rate Ultrashort Mid-IR Pulses	FEL, injection, coupling, radiation	532
	M. Tecimer University of Hawaii at Manoa, Honolulu, USA
	100-200 MeV range ERL-FELs generating few cycle short, high intensity mid-IR pulses with tens of MHz repetition rates might become attractive tools in various strong field applications. In a recent study [1] a mode locked coupled FEL oscillator scheme has been presented to produce multi-mJ level, ultra-short (<10 cycles) pulses tunable within the entire IR region. In this work an improved coupled FEL oscillator scheme is described. The coupled system operates unidirectionally (feedback in the reverse direction less than 10^-8 level). The various operational regimes of the system are discussed. Some of the conclusions stated in [1] have been revised. [1] M. Tecimer, PRST-AB 15, 020703 (2012).

TUP075	Commissioning Status of the ASTA Facility at Fermilab	cryomodule, gun, laser, diagnostics	537
	A.H. Lumpkin, D.R. Broemmelsiek, D.J. Crawford, N. Eddy, D.R. Edstrom, E.R. Harms, A. Hocker, J.R. Leibfritz, J. Ruan, J.K. Santucci, G. Stancari, D. Sun, J.C.T. Thangaraj, R.M. Thurman-Keup, A. Warner, J. Zhu Fermilab, Batavia, Illinois, USA
	Funding: Work at Fermilab supported by Fermi Research Alliance, LLC under Contract No. DE-AC02- 07CH11359 with the United States Department of Energy. Early commissioning results and status of the Advanced Superconducting Test Accelerator (ASTA) at Fermilab will be described. The ASTA facility consists of an L-band rf photocathode (PC) gun, two superconducting L-band rf booster cavities, transport lines, and an 8-cavity TESLA style cryomodule. Early results include first photoelectrons from the Cs2Te photocathode and operations at 3-5 MeV from the rf PC gun. The beam line with one 4-dipole chicane, extensive diagnostics, and 50-MeV spectrometer are being installed. The base beam profile imaging stations have been equipped with both YAG:Ce scintillators and optical transition radiation (OTR) screens, optical transport, and with 5 Mpix digital CCD cameras using Gig-E readout. A set of rf BPMs, wall current monitors, and toroids are also being implemented. Transport of OTR to a C5680 Hamamatsu streak camera is also planned for longitudinal profile information at the picosecond level. Downstream of this location is the 8-cavity cryomodule in which most cavities have been operated at the targeted 31.5 MV/m gradient. Initial beam measurements at 20 MeV and updated cryomodule results will be presented as available.

TUP079	A Swedish Compact Linac-based THz/X-ray Source at FREIA	electron, radiation, gun, linac	545
	V.A. Goryashko Private Address, Uppsala, Sweden A. Opanasenko NSC/KIPT, Kharkov, Ukraine V. Zhaunerchyk University of Gothenburg, Gothenburg, Sweden
	THz radiation enables probing and controlling low-energy excitations in matter such as molecular rotations, DNA dynamics, spin waves and Cooper pairs. In view of growing interest to the THz radiation, the Swedish FEL Center and FREIA Laboratory are working on the conceptual design of a compact multicolor photon source for multidisciplinary research. We present the design of such a source driven by high-brightness electron bunches produced by a superconducting linear accelerator. A THz source is envisioned as an FEL oscillator since this enables not only generation of THz pulses with a bandwidth down to 0.01% (with inter-pulse locking technique) but also generation of short pulses with several cycles in duration by detuning the resonator. For pump-probe experiments, the THz source will be complemented with an X-ray source. One of the most promising options is the inverse Compton scattering of quantum laser pulses from electron bunches. Such an X-ray source will operate in water window with output intensity comparable to a second generation synchrotron. The envisioned THz/X-ray source is compact with a cost comparable to the cost of one beamline at a synchrotron.

TUP091	Developments in the CLARA FEL Test Facility Accelerator Design and Simulations	FEL, gun, linac, diagnostics	589
	P.H. Williams, D. Angal-Kalinin, A.D. Brynes, J.K. Jones, B.P.M. Liggins, J.W. McKenzie, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S. Spampinati Cockcroft Institute, Warrington, Cheshire, United Kingdom
	We present recent developments in the accelerator design of CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility at Daresbury Laboratory. These comprise a revised front-end to ensure integration with the existing VELA line, simulations of a magnetically compressed ultra-short mode and a post-FEL diagnostics section. We also present first considerations on the inclusion of final acceleration using X-band structures.

WEB02	Beam Operation of the PAL-XFEL Injector Test Facility	gun, laser, emittance, electron	615
	J.H. Han, S.Y. Baek, M.S. Chae, H. J. Choi, T. Ha, J.H. Hong, J. Hu, W.H. Hwang, S.H. Jung, H.-S. Kang, C. Kim, C.H. Kim, I.Y. Kim, J.M. Kim, S.H. Kim, I.S. Ko, H.-S. Lee, J. Lee, S.J. Lee, W.W. Lee, C.-K. Min, G. Mun, D.H. Na, S.S. Park, S.J. Park, Y.J. Park, Y.G. Son, H. Yang PAL, Pohang, Kyungbuk, Republic of Korea
	The Pohang Accelerator Laboratory X-ray Free electron Laser (PAL-XFEL) project was launched in 2011. This project aims at the generation of X-ray FEL radiation in a range of 0.1 to 10 nm for photon users with a bunch repetition rate of 60 Hz. The machine consists of a 10 GeV normal conducting S-band linear accelerator and five undulator beamlines. The linac and two undulator beamlines will be constructed by the end of 2015 and first FEL radiation is expected in 2016. As a part of preparation for the project, an Injector Test Facility was constructed in 2012. Since December 2012, beam commissioning is being carried out to find optimum operating conditions and to test accelerator components including RF, laser, diagnostics, magnet, vacuum and control. We present the status of beam commissioning and components tests at the test facility.
	Slides WEB02 [10.249 MB]

WEB04	The New IR FEL Facility at the Fritz-Haber-Institut in Berlin	FEL, electron, radiation, undulator	629
	W. Schöllkopf, W. Erlebach, S. Gewinner, H. Junkes, A. Liedke, G. Meijer, A. Paarmann, G. von Helden FHI, Berlin, Germany H. Bluem, D. Dowell, R. Lange, J. Rathke, A.M.M. Todd, L.M. Young AES, Princeton, New Jersey, USA S.C. Gottschalk STI, Washington, USA U. Lehnert, P. Michel, W. Seidel, R. Wünsch HZDR, Dresden, Germany
	A mid-infrared oscillator FEL has been commissioned at the Fritz-Haber-Institut. The accelerator consists of a thermionic gridded gun, a subharmonic buncher and two S-band standing-wave copper structures [1,2]. It provides a final electron energy adjustable from 15 to 50 MeV, low longitudinal (<50 keV-ps) and transverse emittance (<20 π mm-mrad), at more than 200 pC bunch charge with a micro-pulse repetition rate of 1 GHz and a macro-pulse length of up to 15 μs. Regular user operation started in Nov. 2013 with 6 user stations. Pulsed radiation with up to 100 mJ macro-pulse energy at about 0.5% FWHM bandwidth is routinely produced in the wavelength range from 4 to 48 μm. We will describe the FEL design and its performance as determined by IR power, bandwidth, and micro-pulse length measurements. Further, an overview of the new FHI FEL facility and first user results will be given. The latter include, for instance, spectroscopy of bio-molecules (peptides and small proteins) conformer selected or embedded in superfluid helium nano-droplets at 0.4 K, as well as vibrational spectroscopy of mass-selected metal-oxide clusters and protonated water clusters in the gas phase. [1] W. Schöllkopf et al., MOOB01, Proc. FEL 2012. [2] W. Schöllkopf et al., WEPSO62, Proc. FEL 2013.
	Slides WEB04 [12.785 MB]

THB04	Electron Beam Diagnostics and Feedback for the LCLS-II	feedback, diagnostics, controls, undulator	666
	J.C. Frisch, P. Emma, A.S. Fisher, P. Krejcik, H. Loos, T.J. Maxwell, T.O. Raubenheimer, S.R. Smith SLAC, Menlo Park, California, USA
	Funding: work supported by DOE contract DE-AC02-76-SF00515 The LCLS_II is a CW superconducting accelerator driven, hard and soft X-ray Free Electron Laser which is planned to be constructed at SLAC. It will operate with a variety of beam modes from single shot to approximately 1 MHz CW at bunch charges from 10pc to 300pC with average beam powers up to 1.2 MW. A variety of types of beam instrumentation will be used, including stripline and cavity BPMS, fluorescent and OTR based beam profile monitors, fast wire scanners and transverse deflection cavities. The beam diagnostics system is designed to allow tuning and continuous measurement of beam parameters, and to provide signals for fast beam feedbacks.
	Slides THB04 [1.501 MB]

THP013	Slice Emittance Measurement using RF Deflecting Cavity at PAL-XFEL ITF	emittance, quadrupole, electron, gun	707
	J. Lee POSTECH, Pohang, Kyungbuk, Republic of Korea J.H. Han, J.H. Hong, I.S. Ko, S.J. Park PAL, Pohang, Kyungbuk, Republic of Korea
	One of key characteristic for operating PAL-XFEL is the time-dependent transverse properties of a bunch, slice emittance. To achieve the design FEL performance of PAL-XFEL a slice emittance of 0.4 mm mrad at 0.2 nC is required. An Injector Test Facility (ITF) was constructed to study beam properties. In addition to projected emittance measurement, slice emittance measurement is being done using a transverse RF deflecting cavity. We presents results of slice emittance measurement at ITF and future plan for the optimization of operating condition.

THP019	Higher-Order Moment Models of Longitudinal Pulse Shape Evolution in Photoinjectors	space-charge, wakefield, FEL, electron	722
	C.E. Mitchell, D. Filippetto, R. Huang, C. F. Papadopoulos, H.J. Qian, J. Qiang, F. Sannibale, M. Venturini LBNL, Berkeley, California, USA
	The presence of longitudinal asymmetry, sometimes in the form of a one-sided tail, in the current profile emerging from low-energy photoinjectors can strongly impact the beam quality downstream of the compression system of the FEL beam delivery system. To understand the origin of this feature, an approximate model for the evolution of higher-order beam moments is developed in the presence of nonlinear kinematic effects and longitudinal space-charge. This model is applied to investigate the evolution of beam skewness for injector systems with parameters similar to the APEX Injector under investigation at Lawrence Berkeley National Laboratory.

THP020	Electron Beam Dynamics Optimization Using A Unified Differential Evolution Algorithm	emittance, electron, controls, solenoid	726
	J. Qiang, C.E. Mitchell 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. Accelerator beam dynamics design depends heavily on the use of control parameter optimization to achieve the best performance. In this paper, we report on electron beam dynamics optimization of a model photoinjector using a new unified differential evolution algorithm. We present the new unified differential evolution algorithm and benchmark its performance using several test examples. We also discuss the application of the algorithm in the multi-objective optimization of the photoinjector.

THP024	High-gradient Cathode Testing for MaRIE	cathode, electron, gun, laser	739
	J.W. Lewellen, F.L. Krawczyk, N.A. Moody LANL, Los Alamos, New Mexico, USA
	X-ray free-electron lasers (X-FELs) provide unprecedented capabilities for characterizing and controlling matter at temporal, spatial and energetic regimes which have been previously inaccessible. The quality of the electron beam is critical to X-FEL performance; a degradation of beam quality by a factor of two, for instance, can prevent the X-FEL from lasing at all, rather than yielding a simple reduction in output power. While conceptual designs for new beam sources exist, they incorporate assumptions about the behavior of the photocathode, under extreme operating conditions. The combined requirements for high bunch charge, short bunch duration, and small emission area, dictate the use of high-efficiency photocathodes operating at electric field gradients of ~140 MV/m. No suitable cathode has been operated at these gradients, however, so the success of next-generation X-FELs rests on a series of untested assumptions. We present our plans to address these knowledge gaps, including the design of a high-gradient RF cavity specifically designed for testing cathodes under MaRIE-relevant conditions.

THP042	The LCLS-II Injector Design	gun, cathode, emittance, laser	815
	J.F. Schmerge, A. Brachmann, D. Dowell, A.R. Fry, R.K. Li, Z. Li, T.O. Raubenheimer, T. Vecchione, F. Zhou SLAC, Menlo Park, California, USA A.C. Bartnik, I.V. Bazarov, B.M. Dunham, C.M. Gulliford, C.E. Mayes Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA D. Filippetto, R. Huang, C. F. Papadopoulos, G.J. Portmann, J. Qiang, F. Sannibale, S.P. Virostek, R.P. Wells LBNL, Berkeley, California, USA A. Lunin, N. Solyak, A. Vivoli Fermilab, Batavia, Illinois, USA
	The new LCLS-II project will construct a 4 GeV continuous wave (CW) superconducting linear accelerator to simultaneously feed two undulators which will cover the spectral ranges 0.2-1.2 keV and 1-5 keV, respectively. The injector must provide up to 300 pC/bunch with a normalized emittance < 0.6 mm and peak current > 30 A at up to 1 MHz repetition rate. An electron gun with the required brightness at such high repetition rate has not yet been demonstrated. However, several different options have been explored with results that meet or exceed the performance requirements of LCLS-II. The available technologies for high repetition-rate guns, and the need to keep dark current within acceptable values, limit the accelerating gradient in the electron gun. We propose a CW normal conducting low frequency RF gun for the electron source due to a combination of the simplicity of operation and the highest achieved gradient in a CW gun, potentially allowing for lower beam emittances. The high gradient is especially significant at the 300 pC/bunch charge where beam quality can suffer due to space charge. This paper describes the design challenges and presents our solutions for the LCLS-II injector.

THP048	Formation of the Electron Bunch Longitudinal Profile for Coherent Electron Cooling Experiment	electron, gun, experiment, laser	840
	I. Pinayev, D. Kayran, V. Litvinenko BNL, Upton, Long Island, New York, USA
	Proof-of-princilpe experiment of the coherent electron cooling is ongoing at Brookhaven National Lab. CeC mechanism utilizes amplification of density modulation, induced by hadrons, by an FEL structure. To fully utilize electron beam cooling capacity we need uniform longitudinal beam profile. In this paper we present two frequency injector system tuned for this requirement.

THP053	Steady State Multipacting in a Micro-pulse Electron Gun	electron, cathode, experiment, gun	851
	K. Zhou, X.Y. Lu, X. Luo, S.W. Quan, Z.Q. Yang, J. Zhao PKU, Beijing, People's Republic of China
	Multipacting is a resonant electron discharge phenomenon via secondary electron emission, while micro-pulse electron gun (MPG) utilizes the multipacting current in a radio-frequency (RF) cavity to produce short pulse electron beams. The concept of MPG has been proposed for many years. However, the unstable operating state of MPG vastly obstructs its practical applications. This paper presents a study on the steady state mulitpacting in a MPG. The requirements for steady state multipacting are proposed through the analysis of the interaction between the RF cavity and the beam load. Accordingly, a MPG cavity with the frequency of 2856 MHz has been designed and constructed. Various kinds of grid-anodes are tested in our primary experiments. Both the unstable and stable multipacting current have been observed. Presently, the stable output beam current has been detected at about 12.2 mA. Further experimental study is under way now.
	Poster THP053 [2.525 MB]

THP056	The SwissFEL C-band RF Pulse Compressor: Manufacturing and Proof of Precision by RF Measurements	vacuum, coupling, resonance, klystron	859
	U. Ellenberger, H. Blumer, M. Heusser, M. Kleeb, L. Paly, M. Probst, T. Stapf Paul Scherrer Institute, Villigen PSI, Switzerland M. Bopp, A. Citterio, R. Zennaro PSI, Villigen PSI, Switzerland
	A pulse compressor is required to compress the RF power distributed to the four accelerating structures of a single C-band (5712 GHz) module of the SwissFEL. The pulse compressor is of the barrel open cavity (BOC) type. A total of 26 BOC devices are necessary to operate the linear accelerator (26 modules or 10⁴ C-band structures) of SwissFEL X-ray laser. The C-band BOC combines the advantages of compactness and large RF efficiency i.e. large compression factor. Key features of the BOC are described and how they have been implemented in the manufacturing and tuning processes. RF measurements of the BOC are presented to account for the mechanical precision reached by manufacturing. Up to August 2014 about 6 BOCs have been manufactured in-house and one has been high power tested in a RF test stand to simulate the operation in SwissFEL.

THP057	Longitudinal and Transverse Optimization for a High Repetition Rate Injector	gun, emittance, electron, brightness	864
	C. F. Papadopoulos, D. Filippetto, R. Huang, G.J. Portmann, H.J. Qian, F. Sannibale, S.P. Virostek, R.P. Wells LBNL, Berkeley, California, USA A.C. Bartnik, I.V. Bazarov, B.M. Dunham, C.M. Gulliford, C.E. Mayes Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA A. Brachmann, D. Dowell, P. Emma, Z. Li, T.O. Raubenheimer, J.F. Schmerge, T. Vecchione, F. Zhou SLAC, Menlo Park, California, USA A. Vivoli Fermilab, Batavia, Illinois, USA
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 The injector is the low energy part of a linac, where space charge and kinematic effects may affect the electron beam quality significantly, and in the case of single pass systems determines the brightness in the downstream components. Following the increasing demand for high repetition rate user facilities, the VHF-gun, a normal conducting, high repetition rate (1 MHz) RF gun operating at 186 MHz has been constructed at LBNL within the APEX project and is under operation. In the current paper, we report on the status of the beam dynamics studies. For this, a multi-objected approach is used, where both the transverse and the longitudinal phase space quality is optimized, as quantified by the transverse emittance and the bunch length and energy spread respectively. We also report on different bunch charge operating modes.

THP061	Commissioning of an Improved Superconducting RF Photo Injector at ELBE	gun, SRF, solenoid, laser	881
	J. Teichert, A. Arnold, M. Freitag, P.N. Lu, P. Michel, P. Murcek, H. Vennekate, R. Xiang HZDR, Dresden, Germany P. Kneisel JLab, Newport News, Virginia, USA I. Will MBI, Berlin, Germany
	In order to produce high-brightness electron beams in a superconducting RF photo injector, the most important point is to reach a high acceleration field in the cavity. For this reason two new 3.5-cell niobium cavities were fabricated, chemically treated and cleaned in collaboration with Jlab. The first of these two cavities was shipped to HZDR and assembled in a new cryomodule. This new gun (SRF Gun II) was installed in the ELBE accelerator hall in May 2014 and replaces the previous SRF Gun I. Beside the new cavity the ELBE SRF gun II differs from the previous gun by the integration of a superconducting solenoid. The paper presents the results of the first test run with a Cu photocathode.

THP063	Production of C-band Disk-loaded type CG Accelerating Structures	vacuum, operation, resonance, acceleration	885
	N. Shigeoka, S. Miura, D. Suzuki MHI, Hiroshima, Japan T. Asaka, T. Inagaki, Y. Otake, T. Sakurai RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan H. Ego JASRI/SPring-8, Hyogo-ken, Japan
	In April 2013, MITSUBISHI HEAVY INDUSTRIES, LTD. contracted with RIKEN to produce six C-band disk-loaded type and constant gradient (CG) accelerating structures for removal of SCSS. These structures were newly designed by RIKEN for operation with an acceleration gradient of over 45 MeV/m and a repletion rate of 120 pps. The first structure was delivered in August 2013 to RIKEN and the other five was also delivered in March 2014. The accelerating structures were stacked from one hundred accelerating cells and formed by the vacuum brazing method. These cells using oxygen free copper were ultra-precisely machined. Unlike the C-band choke-mode type structures, which MHI manufactured in past for SACLA, the accelerating cells of the CG structure can be tuned after the brazing by pushing dimpling at the tuning hole of each cell. Demands of a VSWR < 1.1 and a phase error < 3 degree are fulfilled after the tuning by using the nodal shift method, which corrects cell frequency shifts due to the machining errors of cells and a cell’s deformation by the heat cycle of the brazing. The detailed results of the production and low-power RF tests will be presented in this presentation.
	Poster THP063 [0.623 MB]

THP064	High Repetition Rate S-band Photoinjector Design for the CLARA FEL	gun, linac, FEL, emittance	889
	J.W. McKenzie, L.S. Cowie, P. Goudket, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom T.J. Jones STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom V.V. Paramonov RAS/INR, Moscow, Russia
	We present the design of a 1.5cell S-band photoinjector RF gun intended to be operated at repetition rates up to 400 Hz in single bunch mode. This gun is intended for use at the proposed CLARA (Compact Linear Accelerator for Research and Applications) FEL test facility at Daresbury Laboratory in the UK and will first be tested and characterised on VELA (Versatile Electron Linear Accelerator) in 2015. The final cavity design is presented including optimisation for CLARA beam dynamics, and choice of a novel coaxial H-shaped coupler.

THP080	A Low-Cost, High-Reliability Femtosecond Laser Timing System for LCLS	laser, timing, controls, software	917
	K. Gumerlock, J.C. Frisch, B.L. Hill, J. May, D.J. Nelson, S.R. Smith SLAC, Menlo Park, California, USA
	Funding: Work supported by DOE Contract DE-AC02-76-SF00515 LCLS has developed a low-cost, high-reliability radio-frequency-based locking system which provides phase locking with sub-25-femtosecond jitter for the injector and experiment laser systems. This system does not add significantly to the X-ray timing jitter from the accelerator RF distribution. The system uses heterodyne RF locking at 3808 MHz with an I/Q vector phase shifter and variable event receiver triggers to control the timing of the emission of the amplified laser pulse. Controls software provides full automation with a single process variable to control the laser timing over a 600 microsecond range with up to 4 femtosecond resolution, as well as online diagnostics and automatic error correction and recovery. The performance of this new locking system is sufficient for experiments with higher-precision timing needs that use an X-ray/optical cross-correlator to record relative photon arrival times.

THP084	Longitudinal Diagnostics of RF Electron Gun using a 2-cell RF Deflector	electron, gun, laser, experiment	929
	M. Nishiyama, K. Sakaue, T. Takahashi, T. Toida, M. Washio Waseda University, Tokyo, Japan T. Takatomi, J. Urakawa KEK, Ibaraki, Japan
	Funding: This work was supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 and the Quantum Beam Technology Program of MEXT. We have been studying a compact electron accelerator based on an S-band Cs-Te photocathode rf electron gun at Waseda University. We are using this high quality electron bunch for many application researches. It is necessary to measure the bunch length and temporal distribution for evaluating application researches and for improving an rf gun itself. Thus we adopted the rf deflector system. It kicks the electron bunch with resonated rf electromagnetic field. Using this technique, the longitudinal distribution is mapped into the transverse space. The rf deflector has a 2-cell standing wave π-mode structure, operating in TM120 dipole mode at 2856 MHz. It provides a maximum vertical kick of 1.00MV with 750 kW input rf-power which is equivalent to the temporal resolution of around 58 femtoseconds bunch length. In this conference, we report the details of our rf deflector, the latest progress of longitudinal phase space diagnostics and future prospective.

THP085	Commissioning and Results from the Bunch Arrival-time Monitor Downstream the Bunch Compressor at the SwissFEL Test Injector	pick-up, diagnostics, laser, timing	933
	V.R. Arsov, M. Aiba, M.M. Dehler, F. Frei, S. Hunziker, M.G. Kaiser, A. Romann, V. Schlott PSI, Villigen PSI, Switzerland
	A high bandwidth Bunch Arrival-Time Monitor has been commissioned at the Swiss FEL test injector. A new acquisition front end allowing utilization of the ADC full dynamic range has been implemented. The resolution is measured as a function of the charge for different EOM front-ends. Downstream the magnetic chicane the bunch arrival time is sensitive to the amplitude and phases of the RF structures, responsible for creation of an energy chirp, used for bunch compression, as well as the ones of the harmonic cavity, used for phase space linearization. The time of flight as a function of the angle of the magnetic chicane has also been measured.

Paper

Title

Other Keywords

Page

MOB03

Phase Space Manipulations in Modern Accelerators

laser, electron, FEL, radiation

16

D. Xiang
Shanghai Jiao Tong University, Shanghai, People's Republic of China

Funding: This work was supported by the National Natural Science Foundation of China under Grants No. 11327902.
Beam manipulation is a process to rearrange beam's distribution in 6-D phase space. In many cases, a simple phase space manipulation may lead to significant enhancement in the performance of accelerator based facilities. In this paper, I will discuss various beam manipulation techniques for tailoring beam distribution in modern accelerators to meet the requirements of various applications. These techniques become a new focus of accelerator physics R&D and hold great promise in opening up new opportunities in accelerator based scientific facilities.

Slides MOB03 [5.078 MB]

MOP021

Commissioning of a Dual-sweep Streak Camera with Applications to the ASTA Photoinjector Drive Laser

laser, timing, controls, gun

66

A.H. Lumpkin, D.R. Edstrom, J. Ruan, J.K. Santucci
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The high-power electron beams for the Advanced Superconducting Test Accelerator (ASTA) facility will be generated in a photoinjector based on a UV drive laser and the L-band rf photocathode (PC) gun cavity. The initial objectives of these studies were: 1) the evaluation of the amplified UV component’s bunch length and phase stability and 2) the commissioning of the laser room Hamamatsu C5680 streak camera system. We used a new readout camera based on the Prosilica GC1380 digital CCD with Gig-E readout that was compatible with our image processing tools. We observed a longer than expected UV bunch length of 4 ps σ and an unexpected peak multiplicity (with spacing of about 70 ps) in the synchronous sum of 5 UV micropulses. We have now systematically investigated the issues of whether the multiplicity was with each micropulse of the 3-MHz pulse train. We describe our extensive investigations that indicated both issues originated in the multi-pass amplifier. We have replaced the MPA with three single-pass devices, measured 3.5-ps bunch lengths without the multiplicity, and generated photoelectrons from the gun successfully.

MOP028

Field Integral Measurement System and Optical Alignment System for HUST THz-FEL

undulator, FEL, alignment, electron

80

B. Qin, Q.S. Chen, M. Fan, Q. Fu, T. Hu, X. Lei, K.F. Liu, X. Liu, P. Tan, Y.Q. Xiong, J. Yang, L. Yang
HUST, Wuhan, People's Republic of China
X. Liu, Z. Ouyang, Y.B. Wang
Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China
Y.J. Pei
USTC/NSRL, Hefei, Anhui, People's Republic of China

A Free Electron Laser oscillator with radiation wavelength 50–100 μm is under construction in Huazhong University of Science and Technology (HUST). The linear polarization undulator with K=1.0-1.25 has been designed and manufactured by Kyma s.r.l., by using a pure permanent magnet scheme. Acceptance test bas been performed in Kyma factory with well controlled phase error and field integrals for all gaps. This paper introduces the development of an online field integrals measurement system for the undulator, using the stretched wire method. The design and considerations of the optical alignment system is described as well.

MOP088

High Repetition Rate Energy Modulator System Utilizing a Laser Enhancement Cavity

laser, electron, radiation, resonance

260

Y. Honda
KEK, Ibaraki, Japan

A high intensity laser field can be realized at a high repetition rate using an enhancement optical cavity scheme. We propose to apply the 100GW-level laser field inside the cavity for producing a micro-bunch structure in an electron bunch. Combining this system with an ERL scheme of accelerator, it can be used for a seeded FEL at a high repetition rate of ~100MHz continuous beam. The longitudinal electric field at the center area of a higher-order transverse mode of laser can be used to modulate beam energy at a period of the laser wavelength. A 250 MeV class two-loop ERL accelerator has been proposed in KEK as a future upgrade plan of existing 35 MeV ERL test accelerator. It will be able to provide a low emittance, small energy spread, short bunch electron beam at a high repetition rate of continuous operation. We propose to apply this beam to produce a seeded VUV coherent radiation. We will discuss the feasibility of the scheme and status of the laser modulator development.

TUP008

An Analysis of Optimum Out-coupling Fraction for Maximum Output Power in Oscillator FEL

coupling, FEL, electron, laser

368

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

The effect of the out-coupling fraction on the output power in oscillator FEL is analyzed. The formulas of the optimum out-coupling fraction and the corresponding maximum output power are given. They are dependent on the initial small signal gain and the passive loss rate of the light in the optical cavity. The initial comparison show that the result given by the formula agree well with the results in references.

TUP069

Cavity Length Change vs. Mirror Steering in a Ring Confocal Resonator

wiggler, FEL, operation, optics

516

S.V. Benson
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-84-ER40150, the Office of Naval Research, and the Joint Technology Office.
In principle, a ring confocal resonator allows for the use of a short Rayleigh length without the extreme sensi-tivity to mirror steering typical in a near-concentric reso-nator [1]. One possible weakness of such a resonator is that the cavity length is no longer independent of the mirror steering. This is one of the strengths of a linear resonator. In this presentation, it is shown that, in a simple 2-dimensional corner cube type ring confocal resonator, the cavity length is, in fact, not dependent on the mirror steering to first order in the mirror angles. Thus the ring-confocal resonator might be a very easy-to-operate and stable resonator for short Rayleigh range operation in FEL oscillators
[1] Stephen Benson, George Neil, Michelle Shinn, Laser and Beam Control Technologies, Santanu Basu, James Riker, Editors, Proceedings of SPIE Vol. 4632 (2002).

TUP072

Present Status of Coherent Electron Cooling Proof-of-principle Experiment

electron, ion, gun, laser

524

I. Pinayev, Z. Altinbas, D.R. Beavis, S.A. Belomestnykh, I. Ben-Zvi, K.A. Brown, J.C. Brutus, A.J. Curcio, L. DeSanto, A. Elizarov, C. Folz, D.M. Gassner, H. Hahn, Y. Hao, C. Ho, Y. Huang, R.L. Hulsart, M. Ilardo, J.P. Jamilkowski, Y.C. Jing, F.X. Karl, D. Kayran, R. Kellermann, N. Laloudakis, R.F. Lambiase, V. Litvinenko, G.J. Mahler, M. Mapes, W. Meng, R.J. Michnoff, T.A. Miller, M.G. Minty, P. Orfin, A. Pendzick, F. Randazzo, T. Rao, J. Reich, T. Roser, J. Sandberg, B. Sheehy, J. Skaritka, K.S. Smith, L. Snydstrup, A.N. Steszyn, R. Than, C. Theisen, R.J. Todd, J.E. Tuozzolo, E. Wang, G. Wang, D. Weiss, M. Wilinski, T. Xin, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
G.I. Bell, J.R. Cary, K. Paul, I.V. Pogorelov, B.T. Schwartz, A.V. Sobol, S.D. Webb
Tech-X, Boulder, Colorado, USA
C.H. Boulware, T.L. Grimm, R. Jecks, N. Miller
Niowave, Inc., Lansing, Michigan, USA
M.A. Kholopov, P. Vobly
BINP SB RAS, Novosibirsk, Russia
V. Litvinenko
Stony Brook University, Stony Brook, USA
P.A. McIntosh, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Work supported by Stony Brook University and by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The status of FEL-based Coherent Electron Cooling Proof-of-principle Experiment at BNL is presented. The experimental set-up is comprised of a 2 MeV CW SRF electron gun and 20 MeV CW SRF linac and 8-m long helical FEL amplifier. The status of the accelerator commissioning, and progress in the construction of the helical undulator at Budker INP, is also reported

TUP074

High Power Coupled FEL Oscillators for the Generation of High Repetition Rate Ultrashort Mid-IR Pulses

FEL, injection, coupling, radiation

532

M. Tecimer
University of Hawaii at Manoa, Honolulu, USA

100-200 MeV range ERL-FELs generating few cycle short, high intensity mid-IR pulses with tens of MHz repetition rates might become attractive tools in various strong field applications. In a recent study [1] a mode locked coupled FEL oscillator scheme has been presented to produce multi-mJ level, ultra-short (<10 cycles) pulses tunable within the entire IR region. In this work an improved coupled FEL oscillator scheme is described. The coupled system operates unidirectionally (feedback in the reverse direction less than 10^-8 level). The various operational regimes of the system are discussed. Some of the conclusions stated in [1] have been revised.
[1] M. Tecimer, PRST-AB 15, 020703 (2012).

TUP075

Commissioning Status of the ASTA Facility at Fermilab

cryomodule, gun, laser, diagnostics

537

A.H. Lumpkin, D.R. Broemmelsiek, D.J. Crawford, N. Eddy, D.R. Edstrom, E.R. Harms, A. Hocker, J.R. Leibfritz, J. Ruan, J.K. Santucci, G. Stancari, D. Sun, J.C.T. Thangaraj, R.M. Thurman-Keup, A. Warner, J. Zhu
Fermilab, Batavia, Illinois, USA

Funding: Work at Fermilab supported by Fermi Research Alliance, LLC under Contract No. DE-AC02- 07CH11359 with the United States Department of Energy.
Early commissioning results and status of the Advanced Superconducting Test Accelerator (ASTA) at Fermilab will be described. The ASTA facility consists of an L-band rf photocathode (PC) gun, two superconducting L-band rf booster cavities, transport lines, and an 8-cavity TESLA style cryomodule. Early results include first photoelectrons from the Cs2Te photocathode and operations at 3-5 MeV from the rf PC gun. The beam line with one 4-dipole chicane, extensive diagnostics, and 50-MeV spectrometer are being installed. The base beam profile imaging stations have been equipped with both YAG:Ce scintillators and optical transition radiation (OTR) screens, optical transport, and with 5 Mpix digital CCD cameras using Gig-E readout. A set of rf BPMs, wall current monitors, and toroids are also being implemented. Transport of OTR to a C5680 Hamamatsu streak camera is also planned for longitudinal profile information at the picosecond level. Downstream of this location is the 8-cavity cryomodule in which most cavities have been operated at the targeted 31.5 MV/m gradient. Initial beam measurements at 20 MeV and updated cryomodule results will be presented as available.

TUP079

A Swedish Compact Linac-based THz/X-ray Source at FREIA

electron, radiation, gun, linac

545

V.A. Goryashko
Private Address, Uppsala, Sweden
A. Opanasenko
NSC/KIPT, Kharkov, Ukraine
V. Zhaunerchyk
University of Gothenburg, Gothenburg, Sweden

THz radiation enables probing and controlling low-energy excitations in matter such as molecular rotations, DNA dynamics, spin waves and Cooper pairs. In view of growing interest to the THz radiation, the Swedish FEL Center and FREIA Laboratory are working on the conceptual design of a compact multicolor photon source for multidisciplinary research. We present the design of such a source driven by high-brightness electron bunches produced by a superconducting linear accelerator. A THz source is envisioned as an FEL oscillator since this enables not only generation of THz pulses with a bandwidth down to 0.01% (with inter-pulse locking technique) but also generation of short pulses with several cycles in duration by detuning the resonator. For pump-probe experiments, the THz source will be complemented with an X-ray source. One of the most promising options is the inverse Compton scattering of quantum laser pulses from electron bunches. Such an X-ray source will operate in water window with output intensity comparable to a second generation synchrotron. The envisioned THz/X-ray source is compact with a cost comparable to the cost of one beamline at a synchrotron.

TUP091

Developments in the CLARA FEL Test Facility Accelerator Design and Simulations

FEL, gun, linac, diagnostics

589

P.H. Williams, D. Angal-Kalinin, A.D. Brynes, J.K. Jones, B.P.M. Liggins, J.W. McKenzie, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S. Spampinati
Cockcroft Institute, Warrington, Cheshire, United Kingdom

We present recent developments in the accelerator design of CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility at Daresbury Laboratory. These comprise a revised front-end to ensure integration with the existing VELA line, simulations of a magnetically compressed ultra-short mode and a post-FEL diagnostics section. We also present first considerations on the inclusion of final acceleration using X-band structures.

WEB02

Beam Operation of the PAL-XFEL Injector Test Facility

gun, laser, emittance, electron

615

J.H. Han, S.Y. Baek, M.S. Chae, H. J. Choi, T. Ha, J.H. Hong, J. Hu, W.H. Hwang, S.H. Jung, H.-S. Kang, C. Kim, C.H. Kim, I.Y. Kim, J.M. Kim, S.H. Kim, I.S. Ko, H.-S. Lee, J. Lee, S.J. Lee, W.W. Lee, C.-K. Min, G. Mun, D.H. Na, S.S. Park, S.J. Park, Y.J. Park, Y.G. Son, H. Yang
PAL, Pohang, Kyungbuk, Republic of Korea

The Pohang Accelerator Laboratory X-ray Free electron Laser (PAL-XFEL) project was launched in 2011. This project aims at the generation of X-ray FEL radiation in a range of 0.1 to 10 nm for photon users with a bunch repetition rate of 60 Hz. The machine consists of a 10 GeV normal conducting S-band linear accelerator and five undulator beamlines. The linac and two undulator beamlines will be constructed by the end of 2015 and first FEL radiation is expected in 2016. As a part of preparation for the project, an Injector Test Facility was constructed in 2012. Since December 2012, beam commissioning is being carried out to find optimum operating conditions and to test accelerator components including RF, laser, diagnostics, magnet, vacuum and control. We present the status of beam commissioning and components tests at the test facility.

Slides WEB02 [10.249 MB]

WEB04

The New IR FEL Facility at the Fritz-Haber-Institut in Berlin

FEL, electron, radiation, undulator

629

W. Schöllkopf, W. Erlebach, S. Gewinner, H. Junkes, A. Liedke, G. Meijer, A. Paarmann, G. von Helden
FHI, Berlin, Germany
H. Bluem, D. Dowell, R. Lange, J. Rathke, A.M.M. Todd, L.M. Young
AES, Princeton, New Jersey, USA
S.C. Gottschalk
STI, Washington, USA
U. Lehnert, P. Michel, W. Seidel, R. Wünsch
HZDR, Dresden, Germany

A mid-infrared oscillator FEL has been commissioned at the Fritz-Haber-Institut. The accelerator consists of a thermionic gridded gun, a subharmonic buncher and two S-band standing-wave copper structures [1,2]. It provides a final electron energy adjustable from 15 to 50 MeV, low longitudinal (<50 keV-ps) and transverse emittance (<20 π mm-mrad), at more than 200 pC bunch charge with a micro-pulse repetition rate of 1 GHz and a macro-pulse length of up to 15 μs. Regular user operation started in Nov. 2013 with 6 user stations. Pulsed radiation with up to 100 mJ macro-pulse energy at about 0.5% FWHM bandwidth is routinely produced in the wavelength range from 4 to 48 μm. We will describe the FEL design and its performance as determined by IR power, bandwidth, and micro-pulse length measurements. Further, an overview of the new FHI FEL facility and first user results will be given. The latter include, for instance, spectroscopy of bio-molecules (peptides and small proteins) conformer selected or embedded in superfluid helium nano-droplets at 0.4 K, as well as vibrational spectroscopy of mass-selected metal-oxide clusters and protonated water clusters in the gas phase.
[1] W. Schöllkopf et al., MOOB01, Proc. FEL 2012.
[2] W. Schöllkopf et al., WEPSO62, Proc. FEL 2013.

Slides WEB04 [12.785 MB]

THB04

Electron Beam Diagnostics and Feedback for the LCLS-II

feedback, diagnostics, controls, undulator

666

J.C. Frisch, P. Emma, A.S. Fisher, P. Krejcik, H. Loos, T.J. Maxwell, T.O. Raubenheimer, S.R. Smith
SLAC, Menlo Park, California, USA

Funding: work supported by DOE contract DE-AC02-76-SF00515
The LCLS_II is a CW superconducting accelerator driven, hard and soft X-ray Free Electron Laser which is planned to be constructed at SLAC. It will operate with a variety of beam modes from single shot to approximately 1 MHz CW at bunch charges from 10pc to 300pC with average beam powers up to 1.2 MW. A variety of types of beam instrumentation will be used, including stripline and cavity BPMS, fluorescent and OTR based beam profile monitors, fast wire scanners and transverse deflection cavities. The beam diagnostics system is designed to allow tuning and continuous measurement of beam parameters, and to provide signals for fast beam feedbacks.

Slides THB04 [1.501 MB]

THP013

Slice Emittance Measurement using RF Deflecting Cavity at PAL-XFEL ITF

emittance, quadrupole, electron, gun

707

J. Lee
POSTECH, Pohang, Kyungbuk, Republic of Korea
J.H. Han, J.H. Hong, I.S. Ko, S.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea

One of key characteristic for operating PAL-XFEL is the time-dependent transverse properties of a bunch, slice emittance. To achieve the design FEL performance of PAL-XFEL a slice emittance of 0.4 mm mrad at 0.2 nC is required. An Injector Test Facility (ITF) was constructed to study beam properties. In addition to projected emittance measurement, slice emittance measurement is being done using a transverse RF deflecting cavity. We presents results of slice emittance measurement at ITF and future plan for the optimization of operating condition.

THP019

Higher-Order Moment Models of Longitudinal Pulse Shape Evolution in Photoinjectors

space-charge, wakefield, FEL, electron

722

C.E. Mitchell, D. Filippetto, R. Huang, C. F. Papadopoulos, H.J. Qian, J. Qiang, F. Sannibale, M. Venturini
LBNL, Berkeley, California, USA

The presence of longitudinal asymmetry, sometimes in the form of a one-sided tail, in the current profile emerging from low-energy photoinjectors can strongly impact the beam quality downstream of the compression system of the FEL beam delivery system. To understand the origin of this feature, an approximate model for the evolution of higher-order beam moments is developed in the presence of nonlinear kinematic effects and longitudinal space-charge. This model is applied to investigate the evolution of beam skewness for injector systems with parameters similar to the APEX Injector under investigation at Lawrence Berkeley National Laboratory.

THP020

Electron Beam Dynamics Optimization Using A Unified Differential Evolution Algorithm

emittance, electron, controls, solenoid

726

J. Qiang, C.E. Mitchell
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.
Accelerator beam dynamics design depends heavily on the use of control parameter optimization to achieve the best performance. In this paper, we report on electron beam dynamics optimization of a model photoinjector using a new unified differential evolution algorithm. We present the new unified differential evolution algorithm and benchmark its performance using several test examples. We also discuss the application of the algorithm in the multi-objective optimization of the photoinjector.

THP024

High-gradient Cathode Testing for MaRIE

cathode, electron, gun, laser

739

J.W. Lewellen, F.L. Krawczyk, N.A. Moody
LANL, Los Alamos, New Mexico, USA

X-ray free-electron lasers (X-FELs) provide unprecedented capabilities for characterizing and controlling matter at temporal, spatial and energetic regimes which have been previously inaccessible. The quality of the electron beam is critical to X-FEL performance; a degradation of beam quality by a factor of two, for instance, can prevent the X-FEL from lasing at all, rather than yielding a simple reduction in output power. While conceptual designs for new beam sources exist, they incorporate assumptions about the behavior of the photocathode, under extreme operating conditions. The combined requirements for high bunch charge, short bunch duration, and small emission area, dictate the use of high-efficiency photocathodes operating at electric field gradients of ~140 MV/m. No suitable cathode has been operated at these gradients, however, so the success of next-generation X-FELs rests on a series of untested assumptions. We present our plans to address these knowledge gaps, including the design of a high-gradient RF cavity specifically designed for testing cathodes under MaRIE-relevant conditions.

THP042

The LCLS-II Injector Design

gun, cathode, emittance, laser

815

J.F. Schmerge, A. Brachmann, D. Dowell, A.R. Fry, R.K. Li, Z. Li, T.O. Raubenheimer, T. Vecchione, F. Zhou
SLAC, Menlo Park, California, USA
A.C. Bartnik, I.V. Bazarov, B.M. Dunham, C.M. Gulliford, C.E. Mayes
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
D. Filippetto, R. Huang, C. F. Papadopoulos, G.J. Portmann, J. Qiang, F. Sannibale, S.P. Virostek, R.P. Wells
LBNL, Berkeley, California, USA
A. Lunin, N. Solyak, A. Vivoli
Fermilab, Batavia, Illinois, USA

The new LCLS-II project will construct a 4 GeV continuous wave (CW) superconducting linear accelerator to simultaneously feed two undulators which will cover the spectral ranges 0.2-1.2 keV and 1-5 keV, respectively. The injector must provide up to 300 pC/bunch with a normalized emittance < 0.6 mm and peak current > 30 A at up to 1 MHz repetition rate. An electron gun with the required brightness at such high repetition rate has not yet been demonstrated. However, several different options have been explored with results that meet or exceed the performance requirements of LCLS-II. The available technologies for high repetition-rate guns, and the need to keep dark current within acceptable values, limit the accelerating gradient in the electron gun. We propose a CW normal conducting low frequency RF gun for the electron source due to a combination of the simplicity of operation and the highest achieved gradient in a CW gun, potentially allowing for lower beam emittances. The high gradient is especially significant at the 300 pC/bunch charge where beam quality can suffer due to space charge. This paper describes the design challenges and presents our solutions for the LCLS-II injector.

THP048

Formation of the Electron Bunch Longitudinal Profile for Coherent Electron Cooling Experiment

electron, gun, experiment, laser

840

I. Pinayev, D. Kayran, V. Litvinenko
BNL, Upton, Long Island, New York, USA

Proof-of-princilpe experiment of the coherent electron cooling is ongoing at Brookhaven National Lab. CeC mechanism utilizes amplification of density modulation, induced by hadrons, by an FEL structure. To fully utilize electron beam cooling capacity we need uniform longitudinal beam profile. In this paper we present two frequency injector system tuned for this requirement.

THP053

Steady State Multipacting in a Micro-pulse Electron Gun

electron, cathode, experiment, gun

851

K. Zhou, X.Y. Lu, X. Luo, S.W. Quan, Z.Q. Yang, J. Zhao
PKU, Beijing, People's Republic of China

Multipacting is a resonant electron discharge phenomenon via secondary electron emission, while micro-pulse electron gun (MPG) utilizes the multipacting current in a radio-frequency (RF) cavity to produce short pulse electron beams. The concept of MPG has been proposed for many years. However, the unstable operating state of MPG vastly obstructs its practical applications. This paper presents a study on the steady state mulitpacting in a MPG. The requirements for steady state multipacting are proposed through the analysis of the interaction between the RF cavity and the beam load. Accordingly, a MPG cavity with the frequency of 2856 MHz has been designed and constructed. Various kinds of grid-anodes are tested in our primary experiments. Both the unstable and stable multipacting current have been observed. Presently, the stable output beam current has been detected at about 12.2 mA. Further experimental study is under way now.

Poster THP053 [2.525 MB]

THP056

The SwissFEL C-band RF Pulse Compressor: Manufacturing and Proof of Precision by RF Measurements

vacuum, coupling, resonance, klystron

859

U. Ellenberger, H. Blumer, M. Heusser, M. Kleeb, L. Paly, M. Probst, T. Stapf
Paul Scherrer Institute, Villigen PSI, Switzerland
M. Bopp, A. Citterio, R. Zennaro
PSI, Villigen PSI, Switzerland

A pulse compressor is required to compress the RF power distributed to the four accelerating structures of a single C-band (5712 GHz) module of the SwissFEL. The pulse compressor is of the barrel open cavity (BOC) type. A total of 26 BOC devices are necessary to operate the linear accelerator (26 modules or 10⁴ C-band structures) of SwissFEL X-ray laser. The C-band BOC combines the advantages of compactness and large RF efficiency i.e. large compression factor. Key features of the BOC are described and how they have been implemented in the manufacturing and tuning processes. RF measurements of the BOC are presented to account for the mechanical precision reached by manufacturing. Up to August 2014 about 6 BOCs have been manufactured in-house and one has been high power tested in a RF test stand to simulate the operation in SwissFEL.

THP057

Longitudinal and Transverse Optimization for a High Repetition Rate Injector

gun, emittance, electron, brightness

864

C. F. Papadopoulos, D. Filippetto, R. Huang, G.J. Portmann, H.J. Qian, F. Sannibale, S.P. Virostek, R.P. Wells
LBNL, Berkeley, California, USA
A.C. Bartnik, I.V. Bazarov, B.M. Dunham, C.M. Gulliford, C.E. Mayes
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A. Brachmann, D. Dowell, P. Emma, Z. Li, T.O. Raubenheimer, J.F. Schmerge, T. Vecchione, F. Zhou
SLAC, Menlo Park, California, USA
A. Vivoli
Fermilab, Batavia, Illinois, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
The injector is the low energy part of a linac, where space charge and kinematic effects may affect the electron beam quality significantly, and in the case of single pass systems determines the brightness in the downstream components. Following the increasing demand for high repetition rate user facilities, the VHF-gun, a normal conducting, high repetition rate (1 MHz) RF gun operating at 186 MHz has been constructed at LBNL within the APEX project and is under operation. In the current paper, we report on the status of the beam dynamics studies. For this, a multi-objected approach is used, where both the transverse and the longitudinal phase space quality is optimized, as quantified by the transverse emittance and the bunch length and energy spread respectively. We also report on different bunch charge operating modes.

THP061

Commissioning of an Improved Superconducting RF Photo Injector at ELBE

gun, SRF, solenoid, laser

881

J. Teichert, A. Arnold, M. Freitag, P.N. Lu, P. Michel, P. Murcek, H. Vennekate, R. Xiang
HZDR, Dresden, Germany
P. Kneisel
JLab, Newport News, Virginia, USA
I. Will
MBI, Berlin, Germany

In order to produce high-brightness electron beams in a superconducting RF photo injector, the most important point is to reach a high acceleration field in the cavity. For this reason two new 3.5-cell niobium cavities were fabricated, chemically treated and cleaned in collaboration with Jlab. The first of these two cavities was shipped to HZDR and assembled in a new cryomodule. This new gun (SRF Gun II) was installed in the ELBE accelerator hall in May 2014 and replaces the previous SRF Gun I. Beside the new cavity the ELBE SRF gun II differs from the previous gun by the integration of a superconducting solenoid. The paper presents the results of the first test run with a Cu photocathode.

THP063

Production of C-band Disk-loaded type CG Accelerating Structures

vacuum, operation, resonance, acceleration

885

N. Shigeoka, S. Miura, D. Suzuki
MHI, Hiroshima, Japan
T. Asaka, T. Inagaki, Y. Otake, T. Sakurai
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
H. Ego
JASRI/SPring-8, Hyogo-ken, Japan

In April 2013, MITSUBISHI HEAVY INDUSTRIES, LTD. contracted with RIKEN to produce six C-band disk-loaded type and constant gradient (CG) accelerating structures for removal of SCSS. These structures were newly designed by RIKEN for operation with an acceleration gradient of over 45 MeV/m and a repletion rate of 120 pps. The first structure was delivered in August 2013 to RIKEN and the other five was also delivered in March 2014. The accelerating structures were stacked from one hundred accelerating cells and formed by the vacuum brazing method. These cells using oxygen free copper were ultra-precisely machined. Unlike the C-band choke-mode type structures, which MHI manufactured in past for SACLA, the accelerating cells of the CG structure can be tuned after the brazing by pushing dimpling at the tuning hole of each cell. Demands of a VSWR < 1.1 and a phase error < 3 degree are fulfilled after the tuning by using the nodal shift method, which corrects cell frequency shifts due to the machining errors of cells and a cell’s deformation by the heat cycle of the brazing. The detailed results of the production and low-power RF tests will be presented in this presentation.

Poster THP063 [0.623 MB]

THP064

High Repetition Rate S-band Photoinjector Design for the CLARA FEL

gun, linac, FEL, emittance

889

J.W. McKenzie, L.S. Cowie, P. Goudket, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
V.V. Paramonov
RAS/INR, Moscow, Russia

We present the design of a 1.5cell S-band photoinjector RF gun intended to be operated at repetition rates up to 400 Hz in single bunch mode. This gun is intended for use at the proposed CLARA (Compact Linear Accelerator for Research and Applications) FEL test facility at Daresbury Laboratory in the UK and will first be tested and characterised on VELA (Versatile Electron Linear Accelerator) in 2015. The final cavity design is presented including optimisation for CLARA beam dynamics, and choice of a novel coaxial H-shaped coupler.

THP080

A Low-Cost, High-Reliability Femtosecond Laser Timing System for LCLS

laser, timing, controls, software

917

K. Gumerlock, J.C. Frisch, B.L. Hill, J. May, D.J. Nelson, S.R. Smith
SLAC, Menlo Park, California, USA

Funding: Work supported by DOE Contract DE-AC02-76-SF00515
LCLS has developed a low-cost, high-reliability radio-frequency-based locking system which provides phase locking with sub-25-femtosecond jitter for the injector and experiment laser systems. This system does not add significantly to the X-ray timing jitter from the accelerator RF distribution. The system uses heterodyne RF locking at 3808 MHz with an I/Q vector phase shifter and variable event receiver triggers to control the timing of the emission of the amplified laser pulse. Controls software provides full automation with a single process variable to control the laser timing over a 600 microsecond range with up to 4 femtosecond resolution, as well as online diagnostics and automatic error correction and recovery. The performance of this new locking system is sufficient for experiments with higher-precision timing needs that use an X-ray/optical cross-correlator to record relative photon arrival times.

THP084

Longitudinal Diagnostics of RF Electron Gun using a 2-cell RF Deflector

electron, gun, laser, experiment

929

M. Nishiyama, K. Sakaue, T. Takahashi, T. Toida, M. Washio
Waseda University, Tokyo, Japan
T. Takatomi, J. Urakawa
KEK, Ibaraki, Japan

Funding: This work was supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 and the Quantum Beam Technology Program of MEXT.
We have been studying a compact electron accelerator based on an S-band Cs-Te photocathode rf electron gun at Waseda University. We are using this high quality electron bunch for many application researches. It is necessary to measure the bunch length and temporal distribution for evaluating application researches and for improving an rf gun itself. Thus we adopted the rf deflector system. It kicks the electron bunch with resonated rf electromagnetic field. Using this technique, the longitudinal distribution is mapped into the transverse space. The rf deflector has a 2-cell standing wave π-mode structure, operating in TM120 dipole mode at 2856 MHz. It provides a maximum vertical kick of 1.00MV with 750 kW input rf-power which is equivalent to the temporal resolution of around 58 femtoseconds bunch length. In this conference, we report the details of our rf deflector, the latest progress of longitudinal phase space diagnostics and future prospective.

THP085

Commissioning and Results from the Bunch Arrival-time Monitor Downstream the Bunch Compressor at the SwissFEL Test Injector

pick-up, diagnostics, laser, timing

933

V.R. Arsov, M. Aiba, M.M. Dehler, F. Frei, S. Hunziker, M.G. Kaiser, A. Romann, V. Schlott
PSI, Villigen PSI, Switzerland

A high bandwidth Bunch Arrival-Time Monitor has been commissioned at the Swiss FEL test injector. A new acquisition front end allowing utilization of the ADC full dynamic range has been implemented. The resolution is measured as a function of the charge for different EOM front-ends. Downstream the magnetic chicane the bunch arrival time is sensitive to the amplitude and phases of the RF structures, responsible for creation of an energy chirp, used for bunch compression, as well as the ones of the harmonic cavity, used for phase space linearization. The time of flight as a function of the angle of the magnetic chicane has also been measured.