FEL2013 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOPSO76	FEL Operation With the Superconducting RF Photo Gun at ELBE	gun, laser, FEL, SRF	136
	J. Teichert, A. Arnold, H. Büttig, M. Justus, U. Lehnert, P.N. Lu, P. Michel, P. Murcek, R. Schurig, W. Seidel, H. Vennekate, R. Xiang HZDR, Dresden, Germany T. Kamps, J. Rudolph HZB, Berlin, Germany I. Will MBI, Berlin, Germany
	The superconducting RF photoinjector (SRF gun) operating with a 31/2-cell niobium cavity and Cs2Te photocathodes is installed at the ELBE radiation center. The gun provides beams for ELBE as well as in a separate diagnostics beam line for beam parameter measurements. Since 2012 a new UV driver laser system developed by MBI has been installed for the SRF gun . It delivers CW or bust mode pulses with 13 MHz repetition rate or with reduced rates of 500, 200, and 100 kHz at an average UV power of about 1 W. The new laser allows the gun to serve as the driver for the infrared FELs at ELBE. In the first successful experiment a 250 μA beam with 3.3 MeV from SRF gun was injected into ELBE, further accelerated in the ELBE superconducting linac modules and then guided to the U100 undulator. First lasing was achieved at the wavelength of 41 μm. The spectrum, detuning curve and further parameters were measured.

TUOBNO03	An RF Deflecting Cavity Based Spreader System for Next Generation Light Sources	gun, FEL, dipole, electron	173
	C. Sun, L.R. Doolittle, P. Emma, J.-Y. Jung, M. Placidi, A. Ratti LBNL, Berkeley, California, USA
	Lawrence Berkeley National Laboratory (LBNL) is developing design concepts for a multi-beamline (up to 10 lines) soft x-ray FEL array powered by a superconducting linear accelerator with a high bunch repetition rate of approximately one MHz. The FEL array requires a beam spreader system which can distribute individual electron bunches from the linac to each independently configurable beamline. We propose a new spreader system using RF deflecting cavities to deflect electron bunches as an alternative design to the fast kicker scheme. This RF approach offers more stable deflection amplitude while removing the limitations on the bunch repetition rate characteristic of the kicker approach. In this work, we describes the design concept of this RF based spreader system, including technical choices, design parameters and beamline optics. [1] M. Placidi et al., Proceedings of IPAC2012, New Orleans, Louisiana, USA, pp.1765-1767
	Slides TUOBNO03 [1.391 MB]

TUICNO01	Progress in SRF Guns	gun, SRF, electron, cathode	176
	S.A. Belomestnykh BNL, Upton, Long Island, New York, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE In the last couple of years great progress has been made in the commissioning and operation of SRF electron beam sources. Both elliptical cavity designs and reentrant cavities have been developed. This talk will review recent progress in SRF guns.
	Slides TUICNO01 [12.748 MB]

TUOCNO04	Feasibility of CW and LP Operation of the XFEL Linac	cryomodule, linac, HOM, electron	189
	J.K. Sekutowicz, V. Ayvazyan, J. Branlard, M. Ebert, J. Eschke, T. Feldmann, A. Gössel, D. Kostin, I.M. Kudla, W. Merz, F. Mittag, C. Müller, R. Onken, I. Sandvoss, E. Schneidmiller, A.A. Sulimov, M.V. Yurkov DESY, Hamburg, Germany W. Cichalewski, A. Piotrowski, K.P. Przygoda TUL-DMCS, Łódź, Poland K. Czuba Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland W. Jałmużna Embedded Integrated Control Systems GmbH, Hamburg, Germany J. Szewiński NCBJ, Świerk/Otwock, Poland
	The European XFEL superconducting linac is based on cavities and cryomodules (CM) developed for TESLA linear collider. The XFEL linac will operate nominally in short pulse (sp) mode with 1.3 ms RF pulses (650 μs rise time and 650 μs long bunch train). For 240 ns bunch spacing and 10 Hz RF-pulse repetition rate, up to 27000 bunches per second can be accelerated to 17.5 GeV to generate uniquely high average brilliance photon beams at very short wavelengths. While many experiments can take advantage of full bunch trains, others prefer an increased to several μ-seconds intra-pulse distance between bunches, or short bursts with a kHz repetition rate. For these types of experiments, the high average brilliance can be preserved only with duty factors much larger than that of the currently proposed sp operation. In this contribution, we discuss progress in the R&D program for future upgrade of the European XFEL linac, namely an operation in the continuous wave (cw) and long pulse (lp) mode, which will allow for more flexibility in the electron and photon beam time structure.
	Slides TUOCNO04 [8.910 MB]

TUPSO12	RF Design Approach for an NGLS Linac	linac, cryomodule, cryogenics, controls	226
	A. Ratti, J.M. Byrd, J.N. Corlett, L.R. Doolittle, P. Emma, M. Venturini, R.P. Wells LBNL, Berkeley, California, USA C. Adolphsen, C.D. Nantista SLAC, Menlo Park, California, USA D. Arenius, S.V. Benson, D. Douglas, A. Hutton, G. Neil, W. Oren, G.P. Williams JLAB, Newport News, Virginia, USA C.M. Ginsburg, R.D. Kephart, T.J. Peterson, A.I. Sukhanov Fermilab, Batavia, USA
	Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 The Next Generation Light Source (NGLS) is a design concept for a multibeamline soft x-ray FEL array powered by a ~2.4 GeV CW superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. This paper describes the concepts for the cavity and cryostat design operating at 1.3 GHZ and based on minimal modifications to the design of ILC cryomodules, This leverages the extensive experience derived from R&D that resulted in the ILC design. Due to the different nature of the two applications, particular attention is given now to high loaded Q operation and microphonics control, as well as high reliability and expected up time. The work describes the design and configuration of the linac, including choice of gradient, possible modes of operation, cavity design and RF power, as well as the consequent requirements for the cryogenic system.

TUPSO13	Superconducting Linac Design Concepts for a Next Generation Light Source at LBNL	cryomodule, linac, HOM, controls	229
	J.N. Corlett, J.M. Byrd, L.R. Doolittle, P. Emma, A. Ratti, F. Sannibale, M. Venturini, R.P. Wells, S. Zimmermann LBNL, Berkeley, California, USA C. Adolphsen, C.D. Nantista SLAC, Menlo Park, California, USA D. Arenius, G. Neil, T. Powers, J.P. Preble JLAB, Newport News, Virginia, USA C.M. Ginsburg, R.D. Kephart, A.L. Klebaner, T.J. Peterson, A.I. Sukhanov Fermilab, Batavia, USA
	Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 The NGLS collaboration is developing design concepts for a multi-beamline soft X-ray FEL array powered by a superconducting linear accelerator, operating in CW mode, with a high bunch repetition rate of approximately 1 MHz. The superconducting linear accelerator design concept is based on existing TESLA and ILC technology, developed for this CW application in a light source. In this paper we describe design options and preferred approaches for the NGLS SRF linac components, cryomodules, and cryosystems.

TUPSO30	Conditioning Status of the First XFEL Gun at PITZ	gun, vacuum, solenoid, cathode	282
	I.I. Isaev, J.D. Good, M. Groß, L. Hakobyan, L. Jachmann, M. Khojoyan, W. Köhler, G. Kourkafas, M. Krasilnikov, D. Malyutin, B. Marchetti, R. Martin, A. Oppelt, M. Otevřel, B. Petrosyan, D. Richter, A. Shapovalov, F. Stephan, G. Vashchenko, R.W. Wenndorff DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria P. Boonpornprasert, S. Rimjaem Chiang Mai University, Chiang Mai, Thailand M.A. Nozdrin JINR, Dubna, Moscow Region, Russia G. Pathak Uni HH, Hamburg, Germany
	The paper describes the recent results of conditioning and dark current measurements for the photocathode RF gun at the photoinjector test facility at DESY, Zeuthen site (PITZ). The aim of PITZ is to develop and operate an optimized photo injector for free electron lasers and linear accelerators which require high quality beams. In order to get high gradients in the RF gun extensive conditioning is required. A data analysis of the conditioning process is based on data saved by a Data Acquisition system (DAQ). Conditioning results of the first gun cavity for the XFEL is presented. The events which occurred during the conditioning are briefly described.

TUPSO50	Numerical Study on Electron Beam Properties in Triode Type Thermionic RF Gun	gun, cathode, electron, FEL	344
	M. Mishima, M. Inukai, T. Kii, K. Masuda, H. Negm, H. Ohgaki, K. Okumura, M. Omer, K. Torgasin, K. Yoshida, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	The KU-FEL(Kyoto University- Free Electron Laser) facility uses a thermionic 4.5 cell S-band RF gun for electron beam generation because of such advantages over photocathode rf guns as lower cost, higher average current, longer cathode lifetime, and less vacuum requirement. The main disadvantage of using a thermionic RF gun is the back bombardment effect, which causes energy drop in macro pulse of FEL. A triode structure for RF gun was designed in order to minimize the inherent back-bombardment effect. The 2D-simulation has shown significant reduction of back-bombardment power, longitudinal emittance, and an increase of peak current. A coaxial RF cavity was fabricated based on the design for modification of the existing RF gun to a triode type one. The coaxial RF cavity is equipped with gasket tuning system in order to adjust the cavity resonance frequency. However the frequency adjustment by variation of gasket thickness changes the coaxial cavity geometry and might affect the predicted beam optics. Another parameter influencing beam optics is the position of thermionic cathode to be installed in the coaxial cavity, which might vary due to misalignment. K. Masuda, et al., Proceedings of FEL 2009, Liverpool, Pages 281-284 (2009). **K. Torgasin, et al., Proceedings of FEL 2012, Nara(2012).

TUPSO57	Generation of Ultrafast, High-brightness Electron Beams	gun, cathode, electron, brightness	355
	J.H. Park, H. Bluem, J. Rathke, T. Schultheiss, A.M.M. Todd AES, Princeton, New Jersey, USA
	Funding: This work was supported by the U.S. Department of Energy, under Contract No. DE-SC0009556. The production and preservation of ultrafast, high-brightness electron beams is a major R&D challenge for free electron laser (FEL) and ultrafast electron diffraction (UED) because transverse and longitudinal space charge forces drive emittance dilution and bunch lengthening in such beams. Several approaches, such as velocity bunching and magnetic compression, have been considered to solve this problem but each has drawbacks. We present a concept that uses radial bunch compression in an X-band photocathode radio frequency electron gun. By compensating for the path length differential with a curved cathode in an extremely high acceleration gradient cavity, we have demonstrated numerically the possibility of achieving more than an order of magnitude increase in beam brightness over existing electron guns. The initial thermo-structural analysis and mechanical conceptual design of this electron source are presented.

TUPSO58	Developments of a High-average-current Thermionic RF Gun for ERLs and FELs	gun, cathode, electron, FEL	359
	J.H. Park, H. Bluem, J. Rathke, T. Schultheiss, A.M.M. Todd AES, Princeton, New Jersey, USA
	Funding: Supported by ONR under Contract No. N00014-10-C-0191. The development of a high-average-current thermionic RF gun with the required beam performance for lasing would provide significant cost of ownership and reliability gains for high-average-power energy recovery linac (ERL) and free electron laser (FEL) devices. The beam for these applications requires high quality and high performance, specifically: low transverse emittance, short pulse duration and high average current. We are developing a gridded thermionic cathode embedded in a copper one-and-half cell UHF cavity to generate the electron beam. The fundamental RF and higher harmonics are combined on the grid and a gated DC voltage controls the beam emission from the cathode. Simulations indicate that short pulse ~ 10 psec, < 1 MeV electron beams with low-emittance ~ 15 mm-mrad at currents ≥ 100 mA can be generated. The elimination of sensitive photocathodes and their drive laser systems would provide significant capital cost saving, improved reliability and uptime due to increased robustness and hence operating and lifecycle cost savings as well. We will present the gun design and performance simulations and the progress achieved to date in optimizing the device.

TUPSO74	A Coaxially Coupled Deflecting-accelerating Mode Cavity System for Phase-space Exchange (PSEX)	coupling, simulation, emittance, electron	395
	Y.-M. Shin, P. Piot Northern Illinois University, DeKalb, Illinois, USA M.D. Church Fermilab, Batavia, USA J.H. Park, A.M.M. Todd AES, Princeton, New Jersey, USA
	A feasible method to readily remove energy spread (R56 term) due to thick lens effect of a deflecting mode RF-cavity has been widely investigated for emittance exchange in 6D phase-space,. By means of theoretical calculation and numerical analysis, it was found that an accelerating cavity effectively cancel the longitudinal phase space chirp. We have extensively investigated the combined deflecting-accelerating mode phase-space exchanger with the simple RF distribution system of the beam-pipe coaxial coupler. EM simulations proved the coupling scheme with eigenmode and S-parameter analyses. Currently we are looking into 3D beam dynamics in the system with tracking/particle-in-cell (PIC) simulations and wakefield analysis. Proof-of-concept (POC) experiment is planned with a high-Q normal conducting cavity built in a cryogenic cooling system (liquid nitrogen) in Fermilab. P. Emma, et. al., Phys. Rev. ST Accel. Beams 9, 100702 (2006) ** Zholents and M. Zolotorev, LBNL CBP Seminar (2010) and No. ANL/APS/LS-327(2011)

TUPSO75	Design Analysis and High Power RF Test of a 3.9 GHz 5-cell Deflecting-mode Cavity in a Cryogenic Operation	simulation, vacuum, cryomodule, coupling	399
	Y.-M. Shin Northern Illinois University, DeKalb, Illinois, USA M.D. Church Fermilab, Batavia, USA
	A 3.9 GHz deflecting mode (π, TM110) cavity has been long used for six-dimensional phase-space beam manipulation tests [1 - 5] at the A0 Photo-Injector Lab (16 MeV) in Fermilab and their extended applications with vacuum cryomodules are currently planned at the Advanced Superconducting Test Accelerator (ASTA) user facility (> 50 MeV). Despite the successful test results, the cavity, however, demonstrated limited RF performance during liquid nitrogen (LN2) ambient operation that was inferior to theoretical prediction. We have been performing full analysis of the designed cavity by analytic calculation and comprehensive system simulation analysis to solve complex thermodynamics and mechanical stresses. The re-assembled cryomodule is currently under the test with a 50 kW klystron at the Fermilab A0 beamline, which will benchmark the modeling analysis. The test result will be used to design vacuum cryomodules for the 3.9 GHz deflecting mode cavity that will be employed at the ASTA facility for beam diagnostics and phase-space control. [1] D. A. Edwards, LINAC 2002 [2] Y.-E Sun, PRTAB 2004 [3] P. Piot, PRSTAB2006 [4] J. Ruand et al., PRL 2011 [5] Y.-E. Sun, et al., PRL 2010

TUPSO92	Dark Current Measurements at the Rossendorf SRF Gun	gun, cathode, SRF, electron	455
	R. Xiang, A. Arnold, P.N. Lu, P. Murcek, J. Teichert, H. Vennekate HZDR, Dresden, Germany R. Barday, T. Kamps HZB, Berlin, Germany V. Volkov BINP SB RAS, Novosibirsk, Russia
	Funding: the European Community-Research Infrastructure Activity (EuCARD, contract number 227579) and the German Federal Ministry of Education and Research grant 05 ES4BR1/8 In high gradient photo injectors electron field emission creates so-called dark current. The dark current produces beam loss that increases the radiation level, causes damages to the accelerator components, and produces additional background for the users. Field emitted electrons which stay inside the gun, increases RF power consumption and heat load for the superconducting cavities. It is also believed that dark current is the source of local outgassing and plasma formation which can damage sensitive photocathodes. Thus, to understand and control the dark current has become increasingly important for accelerators. In this presentation, we report on dark current measurement at the ELBE SRF Gun at HZDR. The measurements were carried out with the 3.5 cell-cavity SRF gun and Cs2Te photocathodes. We discuss the dark current behavior for different cavity gradients and various solenoid fields. Simulations have been done to understand the experimental results.

WEPSO11	Coherent X-Ray Seeding Source for Driving FELs	undulator, FEL, electron, radiation	522
	A. Novokhatski, F.-J. Decker, R.O. Hettel, Z. Huang, H.-D. Nuhn, M.K. Sullivan SLAC, Menlo Park, California, USA
	Funding: "Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515 The success of the hard X-ray self-seeding experiment at the LCLS is very important in that it provided narrow, nearly transform-limited bandwidth from the FEL, fulfilling a beam quality requirement for experimental applications requiring highly monochromatic X-rays. Yet, because the HXRSS signal is generated random spikes of noise, it is not a truly continuous monochromatic seed signal and even higher FEL performance would be achieved using a continuous seed source. We propose developing such a source using an X-ray cavity to achieve a continuous, narrow band X-ray seed signal. This cavity consists of four crystals with corresponding Bragg angles of about 45 degrees for each. We will analyze and the interaction of X-rays and electron beams with this cavity. This source uses a train of electron bunches initially accelerated in a linear accelerator which then pass through a radiator element situated within an X-ray cavity. The number of bunches is proportional to the achievable Q-value of the X-ray cavity and may be in the range of 10-100. We do not need a high output power of X-ray beams, which leads to relaxed electron beam requirements. We will consider several options.

WEPSO28	Fast Electron Beam and FEL Diagnostics at the ALICE IR-FEL at Daresbury Laboratory	FEL, electron, laser, diagnostics	557
	F. Jackson, D. Angal-Kalinin, D.J. Dunning, J.K. Jones, A. Kalinin, T.T. Thakker, N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom D. Angal-Kalinin, D.J. Dunning, J.K. Jones, N. Thompson Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The ALICE facility at Daresbury Laboratory is an energy recovery based infra-red free electron laser of the oscillator type that has been operational since 2010. Recently fast diagnostics have been installed to perform combined measurements on pulse-by pulse FEL pulse energy and bunch-by-bunch electron bunch position and arrival time. These measurements have highlighted and quantified fast instabilities in the electron beam and consequently the FEL output, and are presented and discussed here.

WEPSO30	Integrating the FHI-FEL Into the FHI Research Environment - Design and Implementation Aspects	FEL, controls, EPICS, ion	562
	H. Junkes, W. Erlebach, S. Gewinner, U. Hoppe, A. Liedke, G. Meijer, W. Schöllkopf, M. Wesemann, G. von Helden FHI, Berlin, Germany H. Bluem, D. Dowell, R. Lange, A.M.M. Todd, L.M. Young AES, Princeton, New Jersey, USA S.B. Webb ORNL, Oak Ridge, Tennessee, USA
	The new mid-infrared FEL at the Fritz-Haber-Institut (FHI) was presented at the FEL12 conference. It will be used for spectroscopic investigations of molecules, clusters, nanoparticles and surfaces. This facility must be easy to use by the scientists at FHI, and should be seamlessly integrated into the existing research environment. The Experimental Physics and Industrial Control System (EPICS) software framework was chosen to build the FHI-FEL control system, and will also be used to interface the user systems. The graphical operator interface is based on the Control System Studio (CSS) package. It covers radiation safety monitoring as well as controlling the complete set of building automation and utility devices, regardless of their particular function. A user interface (subset of the operator interface) allows user-provided experiment-control software (KouDa, LabVIEW, Matlab) to connect with an EPICS Gateway providing secured access. The EPICS Channel Archiver continuously records selected process variable data and provides a web server offering archive and near real-time data. A sample experiment installation demonstrates how this user interface can be used efficiently. W. Schöllkopf et al., FIRST LASING OF THE IR FEL AT THE FRITZ-HABER-INSTITUT, BERLIN, Conference FEL12

WEPSO46	Study on the fluctuation of electron beam position in KU-FEL	gun, FEL, electron, feedback	602
	K. Okumura, M. Inukai, T. Kii, T. Konstantin, K. Masuda, K. Mishima, H. Negm, H. Ohgaki, M. Omer, Y. Tsugamura, K. Yoshida, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	Stability of electron beam is important for stable FEL operation. In Kyoto University MIR-FEL facility (KU-FEL), a BPM (Beam Position Monitor) system consisting of six 4-button electrode type BPMs was installed for monitoring of the electron beam position. The fluctuation of the electron beam position has been observed in horizontal and vertical directions. The origin of the beam position fluctuation is not clarified. In horizontal direction, the main fluctuation source is expected to be the energy fluctuation. As the one of candidate of the energy fluctuation, the cavity temperature of the RF gun has been suspected because the gun is operated in detuned condition [1] which enhances beam energy dependence on the cavity temperature. Another candidate is considered to be the fluctuation of the RF power fed to the gun. Therefore, we start to study the effect of the cavity temperature and the RF power on the position of electron beam. In this conference, we will present the measured result and numerical evaluation of the beam position dependence on temperature and RF power. [1] H. Zen, et al, “Beam Energy Compensation in a Thermionic RF Gun by Cavity Detuning,” IEEE transaction on nuclear science, Vol.56, No. 3, Pages 1487-1491 (2009)

WEPSO69	Optical Cavity Losses Calculation and Optimization of THz FEL with a Waveguide	coupling, FEL, radiation, undulator	689
	P. Tan, Q. Fu, L. Li, B. Qin, K. Xiong, Y.Q. Xiong HUST, Wuhan, People's Republic of China
	Funding: the Fundamental Research Funds for the Central Universities，HUST：2012QN080 The optical cavity with waveguide is used in most long wavelength free electron lasers. In this paper, the losses, gains and modes of a terahertz FEL sources in Huazhong Univeristy of Science and Technology(HUST) are analysis. Then the radii of curvature of the optical mirrors and shapes of the waveguide are optimized.

WEPSO84	Present Status of Kyoto University Free Electron Laser	undulator, FEL, electron, vacuum	711
	H. Zen, M. Inukai, T. Kii, R. Kinjo, K. Masuda, K. Mishima, H. Negm, H. Ohgaki, K. Okumura, M. Omer, K. Torgasin, K. Yoshida Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	A mid-infrared FEL named as KU-FEL (Kyoto University FEL) has been developed for energy related sciences [1]. After the achievement of the first lasing and the power saturation in 2008 [2, 3], we have been working to extend the tunable range of the FEL [4]. By replacing the original 1.6-m undulator into a 1.8 m one, the tunable range was expanded from 10-13 to 5-15 μm in January 2012. Then we fabricated a new undulator duct to reduce the minimum undulator gap from 20 to 15 mm. At 15-mm gap, the FEL gain can be expected to be twice as high as that at 20 mm gap. Commissioning of the new duct will be done in the end of this April. In this presentation, we will report on the result of the commissioning such as tunable range of KU-FEL and the estimated FEL gain, which would be compared with a simulation. [1] H. Zen, et al., Infrared Phys. Techn., 51, 382 (2008) [2] H. Ohgaki, et al., Proc. of FEL08, 4 (2008) [3] H. Ohgaki, et al., Proc. of FEL2009, 572 (2009) [4] H. Zen, et al., Proc. of FEL2012

Paper

Title

Other Keywords

Page

MOPSO76

FEL Operation With the Superconducting RF Photo Gun at ELBE

gun, laser, FEL, SRF

136

J. Teichert, A. Arnold, H. Büttig, M. Justus, U. Lehnert, P.N. Lu, P. Michel, P. Murcek, R. Schurig, W. Seidel, H. Vennekate, R. Xiang
HZDR, Dresden, Germany
T. Kamps, J. Rudolph
HZB, Berlin, Germany
I. Will
MBI, Berlin, Germany

The superconducting RF photoinjector (SRF gun) operating with a 31/2-cell niobium cavity and Cs2Te photocathodes is installed at the ELBE radiation center. The gun provides beams for ELBE as well as in a separate diagnostics beam line for beam parameter measurements. Since 2012 a new UV driver laser system developed by MBI has been installed for the SRF gun . It delivers CW or bust mode pulses with 13 MHz repetition rate or with reduced rates of 500, 200, and 100 kHz at an average UV power of about 1 W. The new laser allows the gun to serve as the driver for the infrared FELs at ELBE. In the first successful experiment a 250 μA beam with 3.3 MeV from SRF gun was injected into ELBE, further accelerated in the ELBE superconducting linac modules and then guided to the U100 undulator. First lasing was achieved at the wavelength of 41 μm. The spectrum, detuning curve and further parameters were measured.

TUOBNO03

An RF Deflecting Cavity Based Spreader System for Next Generation Light Sources

gun, FEL, dipole, electron

173

C. Sun, L.R. Doolittle, P. Emma, J.-Y. Jung, M. Placidi, A. Ratti
LBNL, Berkeley, California, USA

Lawrence Berkeley National Laboratory (LBNL) is developing design concepts for a multi-beamline (up to 10 lines) soft x-ray FEL array powered by a superconducting linear accelerator with a high bunch repetition rate of approximately one MHz. The FEL array requires a beam spreader system which can distribute individual electron bunches from the linac to each independently configurable beamline. We propose a new spreader system using RF deflecting cavities to deflect electron bunches as an alternative design to the fast kicker scheme. This RF approach offers more stable deflection amplitude while removing the limitations on the bunch repetition rate characteristic of the kicker approach. In this work, we describes the design concept of this RF based spreader system, including technical choices, design parameters and beamline optics.
[1] M. Placidi et al., Proceedings of IPAC2012, New Orleans, Louisiana, USA, pp.1765-1767

Slides TUOBNO03 [1.391 MB]

TUICNO01

Progress in SRF Guns

gun, SRF, electron, cathode

176

S.A. Belomestnykh
BNL, Upton, Long Island, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE
In the last couple of years great progress has been made in the commissioning and operation of SRF electron beam sources. Both elliptical cavity designs and reentrant cavities have been developed. This talk will review recent progress in SRF guns.

Slides TUICNO01 [12.748 MB]

TUOCNO04

Feasibility of CW and LP Operation of the XFEL Linac

cryomodule, linac, HOM, electron

189

J.K. Sekutowicz, V. Ayvazyan, J. Branlard, M. Ebert, J. Eschke, T. Feldmann, A. Gössel, D. Kostin, I.M. Kudla, W. Merz, F. Mittag, C. Müller, R. Onken, I. Sandvoss, E. Schneidmiller, A.A. Sulimov, M.V. Yurkov
DESY, Hamburg, Germany
W. Cichalewski, A. Piotrowski, K.P. Przygoda
TUL-DMCS, Łódź, Poland
K. Czuba
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
W. Jałmużna
Embedded Integrated Control Systems GmbH, Hamburg, Germany
J. Szewiński
NCBJ, Świerk/Otwock, Poland

The European XFEL superconducting linac is based on cavities and cryomodules (CM) developed for TESLA linear collider. The XFEL linac will operate nominally in short pulse (sp) mode with 1.3 ms RF pulses (650 μs rise time and 650 μs long bunch train). For 240 ns bunch spacing and 10 Hz RF-pulse repetition rate, up to 27000 bunches per second can be accelerated to 17.5 GeV to generate uniquely high average brilliance photon beams at very short wavelengths. While many experiments can take advantage of full bunch trains, others prefer an increased to several μ-seconds intra-pulse distance between bunches, or short bursts with a kHz repetition rate. For these types of experiments, the high average brilliance can be preserved only with duty factors much larger than that of the currently proposed sp operation. In this contribution, we discuss progress in the R&D program for future upgrade of the European XFEL linac, namely an operation in the continuous wave (cw) and long pulse (lp) mode, which will allow for more flexibility in the electron and photon beam time structure.

Slides TUOCNO04 [8.910 MB]

TUPSO12

RF Design Approach for an NGLS Linac

linac, cryomodule, cryogenics, controls

226

A. Ratti, J.M. Byrd, J.N. Corlett, L.R. Doolittle, P. Emma, M. Venturini, R.P. Wells
LBNL, Berkeley, California, USA
C. Adolphsen, C.D. Nantista
SLAC, Menlo Park, California, USA
D. Arenius, S.V. Benson, D. Douglas, A. Hutton, G. Neil, W. Oren, G.P. Williams
JLAB, Newport News, Virginia, USA
C.M. Ginsburg, R.D. Kephart, T.J. Peterson, A.I. Sukhanov
Fermilab, Batavia, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The Next Generation Light Source (NGLS) is a design concept for a multibeamline soft x-ray FEL array powered by a ~2.4 GeV CW superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. This paper describes the concepts for the cavity and cryostat design operating at 1.3 GHZ and based on minimal modifications to the design of ILC cryomodules, This leverages the extensive experience derived from R&D that resulted in the ILC design. Due to the different nature of the two applications, particular attention is given now to high loaded Q operation and microphonics control, as well as high reliability and expected up time. The work describes the design and configuration of the linac, including choice of gradient, possible modes of operation, cavity design and RF power, as well as the consequent requirements for the cryogenic system.

TUPSO13

Superconducting Linac Design Concepts for a Next Generation Light Source at LBNL

cryomodule, linac, HOM, controls

229

J.N. Corlett, J.M. Byrd, L.R. Doolittle, P. Emma, A. Ratti, F. Sannibale, M. Venturini, R.P. Wells, S. Zimmermann
LBNL, Berkeley, California, USA
C. Adolphsen, C.D. Nantista
SLAC, Menlo Park, California, USA
D. Arenius, G. Neil, T. Powers, J.P. Preble
JLAB, Newport News, Virginia, USA
C.M. Ginsburg, R.D. Kephart, A.L. Klebaner, T.J. Peterson, A.I. Sukhanov
Fermilab, Batavia, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The NGLS collaboration is developing design concepts for a multi-beamline soft X-ray FEL array powered by a superconducting linear accelerator, operating in CW mode, with a high bunch repetition rate of approximately 1 MHz. The superconducting linear accelerator design concept is based on existing TESLA and ILC technology, developed for this CW application in a light source. In this paper we describe design options and preferred approaches for the NGLS SRF linac components, cryomodules, and cryosystems.

TUPSO30

Conditioning Status of the First XFEL Gun at PITZ

gun, vacuum, solenoid, cathode

282

I.I. Isaev, J.D. Good, M. Groß, L. Hakobyan, L. Jachmann, M. Khojoyan, W. Köhler, G. Kourkafas, M. Krasilnikov, D. Malyutin, B. Marchetti, R. Martin, A. Oppelt, M. Otevřel, B. Petrosyan, D. Richter, A. Shapovalov, F. Stephan, G. Vashchenko, R.W. Wenndorff
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
P. Boonpornprasert, S. Rimjaem
Chiang Mai University, Chiang Mai, Thailand
M.A. Nozdrin
JINR, Dubna, Moscow Region, Russia
G. Pathak
Uni HH, Hamburg, Germany

The paper describes the recent results of conditioning and dark current measurements for the photocathode RF gun at the photoinjector test facility at DESY, Zeuthen site (PITZ). The aim of PITZ is to develop and operate an optimized photo injector for free electron lasers and linear accelerators which require high quality beams. In order to get high gradients in the RF gun extensive conditioning is required. A data analysis of the conditioning process is based on data saved by a Data Acquisition system (DAQ). Conditioning results of the first gun cavity for the XFEL is presented. The events which occurred during the conditioning are briefly described.

TUPSO50

Numerical Study on Electron Beam Properties in Triode Type Thermionic RF Gun

gun, cathode, electron, FEL

344

M. Mishima, M. Inukai, T. Kii, K. Masuda, H. Negm, H. Ohgaki, K. Okumura, M. Omer, K. Torgasin, K. Yoshida, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

The KU-FEL(Kyoto University- Free Electron Laser) facility uses a thermionic 4.5 cell S-band RF gun for electron beam generation because of such advantages over photocathode rf guns as lower cost, higher average current, longer cathode lifetime, and less vacuum requirement. The main disadvantage of using a thermionic RF gun is the back bombardment effect, which causes energy drop in macro pulse of FEL. A triode structure for RF gun was designed in order to minimize the inherent back-bombardment effect. The 2D-simulation has shown significant reduction of back-bombardment power, longitudinal emittance, and an increase of peak current*. A coaxial RF cavity was fabricated based on the design for modification of the existing RF gun to a triode type one. The coaxial RF cavity is equipped with gasket tuning system in order to adjust the cavity resonance frequency**. However the frequency adjustment by variation of gasket thickness changes the coaxial cavity geometry and might affect the predicted beam optics. Another parameter influencing beam optics is the position of thermionic cathode to be installed in the coaxial cavity, which might vary due to misalignment.
*K. Masuda, et al., Proceedings of FEL 2009, Liverpool, Pages 281-284 (2009).
**K. Torgasin, et al., Proceedings of FEL 2012, Nara(2012).

TUPSO57

Generation of Ultrafast, High-brightness Electron Beams

gun, cathode, electron, brightness

355

J.H. Park, H. Bluem, J. Rathke, T. Schultheiss, A.M.M. Todd
AES, Princeton, New Jersey, USA

Funding: This work was supported by the U.S. Department of Energy, under Contract No. DE-SC0009556.
The production and preservation of ultrafast, high-brightness electron beams is a major R&D challenge for free electron laser (FEL) and ultrafast electron diffraction (UED) because transverse and longitudinal space charge forces drive emittance dilution and bunch lengthening in such beams. Several approaches, such as velocity bunching and magnetic compression, have been considered to solve this problem but each has drawbacks. We present a concept that uses radial bunch compression in an X-band photocathode radio frequency electron gun. By compensating for the path length differential with a curved cathode in an extremely high acceleration gradient cavity, we have demonstrated numerically the possibility of achieving more than an order of magnitude increase in beam brightness over existing electron guns. The initial thermo-structural analysis and mechanical conceptual design of this electron source are presented.

TUPSO58

Developments of a High-average-current Thermionic RF Gun for ERLs and FELs

gun, cathode, electron, FEL

359

J.H. Park, H. Bluem, J. Rathke, T. Schultheiss, A.M.M. Todd
AES, Princeton, New Jersey, USA

Funding: Supported by ONR under Contract No. N00014-10-C-0191.
The development of a high-average-current thermionic RF gun with the required beam performance for lasing would provide significant cost of ownership and reliability gains for high-average-power energy recovery linac (ERL) and free electron laser (FEL) devices. The beam for these applications requires high quality and high performance, specifically: low transverse emittance, short pulse duration and high average current. We are developing a gridded thermionic cathode embedded in a copper one-and-half cell UHF cavity to generate the electron beam. The fundamental RF and higher harmonics are combined on the grid and a gated DC voltage controls the beam emission from the cathode. Simulations indicate that short pulse ~ 10 psec, < 1 MeV electron beams with low-emittance ~ 15 mm-mrad at currents ≥ 100 mA can be generated. The elimination of sensitive photocathodes and their drive laser systems would provide significant capital cost saving, improved reliability and uptime due to increased robustness and hence operating and lifecycle cost savings as well. We will present the gun design and performance simulations and the progress achieved to date in optimizing the device.

TUPSO74

A Coaxially Coupled Deflecting-accelerating Mode Cavity System for Phase-space Exchange (PSEX)

coupling, simulation, emittance, electron

395

Y.-M. Shin, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
M.D. Church
Fermilab, Batavia, USA
J.H. Park, A.M.M. Todd
AES, Princeton, New Jersey, USA

A feasible method to readily remove energy spread (R56 term) due to thick lens effect of a deflecting mode RF-cavity has been widely investigated for emittance exchange in 6D phase-space*,**. By means of theoretical calculation and numerical analysis, it was found that an accelerating cavity effectively cancel the longitudinal phase space chirp. We have extensively investigated the combined deflecting-accelerating mode phase-space exchanger with the simple RF distribution system of the beam-pipe coaxial coupler. EM simulations proved the coupling scheme with eigenmode and S-parameter analyses. Currently we are looking into 3D beam dynamics in the system with tracking/particle-in-cell (PIC) simulations and wakefield analysis. Proof-of-concept (POC) experiment is planned with a high-Q normal conducting cavity built in a cryogenic cooling system (liquid nitrogen) in Fermilab.
* P. Emma, et. al., Phys. Rev. ST Accel. Beams 9, 100702 (2006)
** Zholents and M. Zolotorev, LBNL CBP Seminar (2010) and No. ANL/APS/LS-327(2011)

TUPSO75

Design Analysis and High Power RF Test of a 3.9 GHz 5-cell Deflecting-mode Cavity in a Cryogenic Operation

simulation, vacuum, cryomodule, coupling

399

Y.-M. Shin
Northern Illinois University, DeKalb, Illinois, USA
M.D. Church
Fermilab, Batavia, USA

A 3.9 GHz deflecting mode (π, TM110) cavity has been long used for six-dimensional phase-space beam manipulation tests [1 - 5] at the A0 Photo-Injector Lab (16 MeV) in Fermilab and their extended applications with vacuum cryomodules are currently planned at the Advanced Superconducting Test Accelerator (ASTA) user facility (> 50 MeV). Despite the successful test results, the cavity, however, demonstrated limited RF performance during liquid nitrogen (LN2) ambient operation that was inferior to theoretical prediction. We have been performing full analysis of the designed cavity by analytic calculation and comprehensive system simulation analysis to solve complex thermodynamics and mechanical stresses. The re-assembled cryomodule is currently under the test with a 50 kW klystron at the Fermilab A0 beamline, which will benchmark the modeling analysis. The test result will be used to design vacuum cryomodules for the 3.9 GHz deflecting mode cavity that will be employed at the ASTA facility for beam diagnostics and phase-space control.
[1] D. A. Edwards, LINAC 2002
[2] Y.-E Sun, PRTAB 2004
[3] P. Piot, PRSTAB2006
[4] J. Ruand et al., PRL 2011
[5] Y.-E. Sun, et al., PRL 2010

TUPSO92

Dark Current Measurements at the Rossendorf SRF Gun

gun, cathode, SRF, electron

455

R. Xiang, A. Arnold, P.N. Lu, P. Murcek, J. Teichert, H. Vennekate
HZDR, Dresden, Germany
R. Barday, T. Kamps
HZB, Berlin, Germany
V. Volkov
BINP SB RAS, Novosibirsk, Russia

Funding: the European Community-Research Infrastructure Activity (EuCARD, contract number 227579) and the German Federal Ministry of Education and Research grant 05 ES4BR1/8
In high gradient photo injectors electron field emission creates so-called dark current. The dark current produces beam loss that increases the radiation level, causes damages to the accelerator components, and produces additional background for the users. Field emitted electrons which stay inside the gun, increases RF power consumption and heat load for the superconducting cavities. It is also believed that dark current is the source of local outgassing and plasma formation which can damage sensitive photocathodes. Thus, to understand and control the dark current has become increasingly important for accelerators. In this presentation, we report on dark current measurement at the ELBE SRF Gun at HZDR. The measurements were carried out with the 3.5 cell-cavity SRF gun and Cs2Te photocathodes. We discuss the dark current behavior for different cavity gradients and various solenoid fields. Simulations have been done to understand the experimental results.

WEPSO11

Coherent X-Ray Seeding Source for Driving FELs

undulator, FEL, electron, radiation

522

A. Novokhatski, F.-J. Decker, R.O. Hettel, Z. Huang, H.-D. Nuhn, M.K. Sullivan
SLAC, Menlo Park, California, USA

Funding: "Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515
The success of the hard X-ray self-seeding experiment at the LCLS is very important in that it provided narrow, nearly transform-limited bandwidth from the FEL, fulfilling a beam quality requirement for experimental applications requiring highly monochromatic X-rays. Yet, because the HXRSS signal is generated random spikes of noise, it is not a truly continuous monochromatic seed signal and even higher FEL performance would be achieved using a continuous seed source. We propose developing such a source using an X-ray cavity to achieve a continuous, narrow band X-ray seed signal. This cavity consists of four crystals with corresponding Bragg angles of about 45 degrees for each. We will analyze and the interaction of X-rays and electron beams with this cavity. This source uses a train of electron bunches initially accelerated in a linear accelerator which then pass through a radiator element situated within an X-ray cavity. The number of bunches is proportional to the achievable Q-value of the X-ray cavity and may be in the range of 10-100. We do not need a high output power of X-ray beams, which leads to relaxed electron beam requirements. We will consider several options.

WEPSO28

Fast Electron Beam and FEL Diagnostics at the ALICE IR-FEL at Daresbury Laboratory

FEL, electron, laser, diagnostics

557

F. Jackson, D. Angal-Kalinin, D.J. Dunning, J.K. Jones, A. Kalinin, T.T. Thakker, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
D. Angal-Kalinin, D.J. Dunning, J.K. Jones, N. Thompson
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The ALICE facility at Daresbury Laboratory is an energy recovery based infra-red free electron laser of the oscillator type that has been operational since 2010. Recently fast diagnostics have been installed to perform combined measurements on pulse-by pulse FEL pulse energy and bunch-by-bunch electron bunch position and arrival time. These measurements have highlighted and quantified fast instabilities in the electron beam and consequently the FEL output, and are presented and discussed here.

WEPSO30

Integrating the FHI-FEL Into the FHI Research Environment - Design and Implementation Aspects

FEL, controls, EPICS, ion

562

H. Junkes, W. Erlebach, S. Gewinner, U. Hoppe, A. Liedke, G. Meijer, W. Schöllkopf, M. Wesemann, G. von Helden
FHI, Berlin, Germany
H. Bluem, D. Dowell, R. Lange, A.M.M. Todd, L.M. Young
AES, Princeton, New Jersey, USA
S.B. Webb
ORNL, Oak Ridge, Tennessee, USA

The new mid-infrared FEL at the Fritz-Haber-Institut (FHI) was presented at the FEL12 conference*. It will be used for spectroscopic investigations of molecules, clusters, nanoparticles and surfaces. This facility must be easy to use by the scientists at FHI, and should be seamlessly integrated into the existing research environment. The Experimental Physics and Industrial Control System (EPICS) software framework was chosen to build the FHI-FEL control system, and will also be used to interface the user systems. The graphical operator interface is based on the Control System Studio (CSS) package. It covers radiation safety monitoring as well as controlling the complete set of building automation and utility devices, regardless of their particular function. A user interface (subset of the operator interface) allows user-provided experiment-control software (KouDa, LabVIEW, Matlab) to connect with an EPICS Gateway providing secured access. The EPICS Channel Archiver continuously records selected process variable data and provides a web server offering archive and near real-time data. A sample experiment installation demonstrates how this user interface can be used efficiently.
* W. Schöllkopf et al., FIRST LASING OF THE IR FEL AT THE FRITZ-HABER-INSTITUT, BERLIN, Conference FEL12

WEPSO46

Study on the fluctuation of electron beam position in KU-FEL

gun, FEL, electron, feedback

602

K. Okumura, M. Inukai, T. Kii, T. Konstantin, K. Masuda, K. Mishima, H. Negm, H. Ohgaki, M. Omer, Y. Tsugamura, K. Yoshida, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

Stability of electron beam is important for stable FEL operation. In Kyoto University MIR-FEL facility (KU-FEL), a BPM (Beam Position Monitor) system consisting of six 4-button electrode type BPMs was installed for monitoring of the electron beam position. The fluctuation of the electron beam position has been observed in horizontal and vertical directions. The origin of the beam position fluctuation is not clarified. In horizontal direction, the main fluctuation source is expected to be the energy fluctuation. As the one of candidate of the energy fluctuation, the cavity temperature of the RF gun has been suspected because the gun is operated in detuned condition [1] which enhances beam energy dependence on the cavity temperature. Another candidate is considered to be the fluctuation of the RF power fed to the gun. Therefore, we start to study the effect of the cavity temperature and the RF power on the position of electron beam. In this conference, we will present the measured result and numerical evaluation of the beam position dependence on temperature and RF power.
[1] H. Zen, et al, “Beam Energy Compensation in a Thermionic RF Gun by Cavity Detuning,” IEEE transaction on nuclear science, Vol.56, No. 3, Pages 1487-1491 (2009)

WEPSO69

Optical Cavity Losses Calculation and Optimization of THz FEL with a Waveguide

coupling, FEL, radiation, undulator

689

P. Tan, Q. Fu, L. Li, B. Qin, K. Xiong, Y.Q. Xiong
HUST, Wuhan, People's Republic of China

Funding: the Fundamental Research Funds for the Central Universities，HUST：2012QN080
The optical cavity with waveguide is used in most long wavelength free electron lasers. In this paper, the losses, gains and modes of a terahertz FEL sources in Huazhong Univeristy of Science and Technology(HUST) are analysis. Then the radii of curvature of the optical mirrors and shapes of the waveguide are optimized.

WEPSO84

Present Status of Kyoto University Free Electron Laser

undulator, FEL, electron, vacuum

711

H. Zen, M. Inukai, T. Kii, R. Kinjo, K. Masuda, K. Mishima, H. Negm, H. Ohgaki, K. Okumura, M. Omer, K. Torgasin, K. Yoshida
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

A mid-infrared FEL named as KU-FEL (Kyoto University FEL) has been developed for energy related sciences [1]. After the achievement of the first lasing and the power saturation in 2008 [2, 3], we have been working to extend the tunable range of the FEL [4]. By replacing the original 1.6-m undulator into a 1.8 m one, the tunable range was expanded from 10-13 to 5-15 μm in January 2012. Then we fabricated a new undulator duct to reduce the minimum undulator gap from 20 to 15 mm. At 15-mm gap, the FEL gain can be expected to be twice as high as that at 20 mm gap. Commissioning of the new duct will be done in the end of this April. In this presentation, we will report on the result of the commissioning such as tunable range of KU-FEL and the estimated FEL gain, which would be compared with a simulation.
[1] H. Zen, et al., Infrared Phys. Techn., 51, 382 (2008)
[2] H. Ohgaki, et al., Proc. of FEL08, 4 (2008)
[3] H. Ohgaki, et al., Proc. of FEL2009, 572 (2009)
[4] H. Zen, et al., Proc. of FEL2012