FEL2011 - List of Keywords (cathode)

Paper	Title	Other Keywords	Page
TUOCI1	Latest Developments for Photoinjector, Seeding and THz Laser Systems	laser, gun, electron, radiation	173
	C.P. Hauri, A. Trisorio, C. Vicario Paul Scherrer Institut, Villigen, Switzerland C. Ruchert PSI, Villigen PSI, Switzerland
	For driving compact FEL facilities cutting edge laser technology is required. We present the latest laser developments and concepts for ultrastable and versatile electron gun lasers, seed lasers and high-power laser-based THz sources taking place at the Paul Scherrer Institute and at other Free Electron Laser facilities. Such developments are of fundamental interest for next generation FEL pump-probe experiments requiring a temporal resolution beyond state of the art.
	Slides TUOCI1 [5.159 MB]

TUOC3	High QE, Low Emittance, Green Sensitive FEL Photocathodes Using K₂CsSb	emittance, electron, laser, gun	179
	H.A. Padmore, D. Dowell, J. Feng, T. Vecchione, W. Wan LBNL, Berkeley, California, USA I. Ben-Zvi Stony Brook University, Stony Brook, USA T. Rao, J. Smedley BNL, Upton, Long Island, New York, USA
	Funding: Work was supported by the Director, Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy, under Contract No. DE-AC02-05CH11231, KC0407-ALSJNT-I0013, and DE-SC0005713. We describe the development of photocathodes based on Potassium-Cesium-Antimonide that satisfy many of the key requirements of future light sources, such as robustness, high quantum efficiency when excited with visible light and low transverse emittance. We have demonstrated QE of 7% at 532 nm, a normalized transverse emittance of 0.36 μm at 543 nm and 3 MV/m field gradient[1]. We have also shown that the material can be relatively robust to residual water contamination and we have extracted current densities of 1 mA/mm² with very long lifetime. We believe that this work is an important step forward in FEL development where high repetition rate is required. [1] Applied Physics Letters (submitted)
	Slides TUOC3 [4.825 MB]

TUPA21	Optical Synchronization of the SwissFEL 250 Mev Test Injector Gun Laser With the Optical Master Oscillator	laser, controls, FEL, gun	243
	V.R. Arsov, S. Hunziker, M.G. Kaiser, V. Schlott Paul Scherrer Institut, Villigen, Switzerland F. Löhl CLASSE, Ithaca, New York, USA
	Funding: This work is partly supported by IRUVX-PP, an EU co-funded project under FP7 (Grant Agreement 211285) The SwissFEL gun laser stability is crucial for stable SASE operation in the hard X-ray regime. In 10 pC mode in which sub-10 fs photon pulses will be delivered for the users, the gun laser arrival time jitter at the cathode shouldn't exceed 30 fs (rms). In the present design it is foreseen that the gun oscillator is optically stabilized. It is also necessary to check the stability of the combination laser oscillator and transfer line with an optical reference. For this, the Ti:Sa oscillator was used as a master laser and its pulses were delivered through a ca. 5 m long free space transfer line to optically synchronize an Er-fiber oscillator via two color balanced optical cross correlator with a BBO crystal. The two lasers were placed on different optical tables, which didn't have a mechanical connection through the transfer line. Stable optical lock for at least 60 minutes was demonstrated with an in-loop stability in the range 3.7-17.6 fs. In the range 10 Hz-1 kHz the phase noise stability of the optically locked Er-fiber oscillator varied between 76.5 fs and 118.5 fs rms, 76 fs of which was the contribution of the 1.5 GHz PLO, to which the Ti:Sa oscillator was RF-locked.

WEPA01	Commissioning of a Photoinjector in HLS	laser, emittance, solenoid, gun	331
	Z.G. He, Q.K. Jia, B.G. Sun, X.H. Wang USTC/NSRL, Hefei, Anhui, People's Republic of China
	A BNL type photoinjector was installed in HLS (Hefei Light Source) and commissioning work was carrying out in last months. The dark current was measured when the high power testing of the gun was processed. The quantum efficiency (QE) of the photocathode was measured and studied, the main parameters of beam quality such as electric charge, transverse emittance and energy were measured and presented in this paper.

WEPA06	Experimental Studies with Spatial Gaussian-cut Laser for the LCLS Photocathode Gun	laser, emittance, simulation, electron	341
	F. Zhou, A. Brachmann, P. Emma, A. Gilevich, Z. Huang SLAC, Menlo Park, California, USA
	Funding: U.S. Department of Energy under contract DE-AC02-76SF00515 To further enhance the LCLS injector performances or simplify its operating conditions, we are evaluating the various parameters including the photocathode drive laser. Simulations show that both the projected and time-sliced emittances with spatial Gaussian profiles having reasonable tail-cutoff are better than those with uniform one. The simulated results are also supported by theoretical analyses. In the LCLS, the spatial uniform or quasi-Gaussian laser profiles are conveniently obtained by adjusting the optics of telescope upstream of an iris, used to define laser size on the cathode. Preliminary beam studies at the LCLS show that both the projected and time-sliced emittances with spatial quasi-Gaussian laser are almost as good as, although not better than, those with uniform one, and also laser transmission through the iris with the quasi-Gaussian is twice that with uniform one, which is to ease copper cathode operations and thus improve the LCLS operation efficiency. More beam studies are planned in the coming summer to measure FEL performances with the quasi-Gaussian in comparison with the uniform one. All simulations and measurements are presented.

WEPA12	The Driving Laser for FEL-THz	laser, FEL, gun, electron	349
	Y. Chen, M. Li, H.B. Wang, D. Wu, X. Yang CAEP/IAE, Mianyang, Sichuan, People's Republic of China
	A solid-state driving laser system have been developed to meet the requirements of the FEL-THz research. The design specifications, configuration and diode-pumped amplifier of the drive-laser system are also described. The laser system can generate continuous or 10μs-20μs pulses light with wavelength 10⁶⁴ nm, 532nm, 266nm at a repetition rate 54.167MHz. The average power of the driving laser system is more than 25W, 8W, 1W at wavelength 1064nm, 532nm, 266nm respectively. The cathode material is GaAs. The second harmonic is used, of which average power is 8.55W, pulse width is about 12ps, power stability is 0.72% and pointing stability is 46urad.

WEPA23	DEVELOPMENT OF AN ITC-RF GUN FOR COMPACT THz FEL	gun, electron, cavity, FEL	385
	W. Bai, Y. Chen, M. Li, L.J. Shan, X.M. Shen, H.B. Wang CAEP/IAE, Mianyang, Sichuan, People's Republic of China
	An independent tunable cells thermionic rf gun (ITC-RF Gun) used for compact Tera-hertz (THz) free electron laser(FEL) is developed at Institute of Applied Electronics, China Academy of Engineering Physics (CAEP). This RF-gun consists of a single cell and a 3-cells accelerating cavity which are excited independently, so the amplitude and phase of the two parts can be adjusted easily. The paper introduces some results of the simulation, cold test and preliminary hot test. The test results agree well with the theoretical design.

WEPB20	The Design Of A Multi-Beam Electron Gun For A Photonic Free-Electron Laser	gun, electron, emittance, beam-transport	427
	J.H.H. Lee, K.-J. Boller, T. Denis, P.J.M. van der Slot Mesa+, Enschede, The Netherlands
	Funding: This research is supported by the Dutch Technology Foundation STW, applied science division of NWO and the Technology Program of the Ministry of Economic Affairs. The photonic Free-Electron Laser (pFEL) is a novel slow-wave device which relies on a photonic crystal (PhC) to synchronize the Cherenkov electromagnetic radiation generated from the co-propagating electron beams. The advantage of pFEL is in its frequency- and power-scaling properties. The scale invariance of Maxwell’s equations allows the use of the same beam energy to operate at higher frequencies when the PhC is correspondingly scaled. On the other hand, power-scaling is achieved by varying the number of electron beams propagating in parallel through the PhC. To produce a set of parallel beams, we have designed a multi-beam electron gun using flat cathodes, which produces a total current of 1 A at a beam voltage of 14 kV. We will present the design of this gun together with the expected performance. In addition, we have investigated the beam transport system and will discuss the options for guiding the beams through the PhC.

THPA10	RF Photo Gun Stability Measurement at PITZ	gun, laser, feedback, monitoring	485
	I.I. Isaev, G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff DESY Zeuthen, Zeuthen, Germany M. Hoffmann, H. Schlarb DESY, Hamburg, Germany M.A. Khojoyan ANSL, Yerevan, Armenia D. Richter BESSY GmbH, Berlin, Germany A. Shapovalov MEPhI, Moscow, Russia
	High stability of the RF photo gun is one of the necessary conditions for the successful operation of linac based free electron lasers. Fluctuations of the RF launch phase have significant influence on the beam quality. Investigation on the dependence of different gun parameters and selection of optimal conditions are required to achieve high RF gun phase stability. Measurements of the gun RF phase stability are based on beam charge and momentum monitoring downstream of the gun. The stability of the RF gun phase for different operating conditions has been measured at the Photo Injector Test facility at DESY in Zeuthen (PITZ) and the results will be presented.

THPA15	Simulation Studies of Generating Ultra Short Pulses at PITZ	laser, electron, emittance, simulation	499
	M.A. Khojoyan, M. Krasilnikov, A. Oppelt, F. Stephan DESY Zeuthen, Zeuthen, Germany M.A. Khojoyan ANSL, Yerevan, Armenia
	Generation of the ultra short electron bunches (<10fs bunch length) which have a small transverse phase space volume and relatively small energy spread is of great interest. Such bunches are required for fully coherent (transversally and longitudinally) FEL radiation (single spike lasing) and for plasma acceleration experiments. The Photo Injector Test Facility at DESY in Zeuthen has already demonstrated the possibility to generate and characterize high quality electron beams for a wide range of bunch charges. Currently electron bunches have a typical length of several ps. To study the possibility of producing short electron bunches at PITZ many beam dynamics simulations have been performed for 1pC bunch charge using the ASTRA code. The current PITZ beam line is supposed to be extended by a small magnet chicane. Several temporal profiles of the cathode laser pulse have been used for the simulations to produce ultra-short electron bunches with small transverse sizes. The results of the beam dynamics simulations are presented and discussed.

THPA17	Study of the Back-bombardment Effect in the ITC-Rf Gun for t-ACTS Project at Tohoku University	gun, electron, simulation, radiation	503
	X. Li, H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, T. Muto, K. Nanbu, Y. Tanaka Tohoku University, Research Center for Electron Photon Science, Sendai, Japan F. Miyahara KEK, Ibaraki, Japan
	A specially designed thermionic RF gun which consists of two independently tunable cells [1] (ITC) is used to produce sub-picoseconds electron pulses as the source for coherent terahertz radiation at Tohoku University. Simulations of particle motion show that the back-bombardment effect on the LaB6 cathode surface is serious and should be controlled carefully. Using EGS5 [2] the power deposition of the back-bombardment inside the cathode can be calculated by using the information of back-streaming electrons derived from GPT [3] simulation, and further used to evaluate the temperature increase on the cathode surface by numerically solving a 2-dimentional equation for heat conduction. In the 2D model, the back-streaming electrons are treated as external heat source as well as the cathode heater that heats the cathode from its side along with thermal radiation from its surface. In addition, some methods will be proposed to reduce the back-bombardment effect and we will also compare the simulation results with experimental data. [1] H. Hama et al., New J. Phys. 8 (2006) 292 [2] Electron Gamma Shower, http://rcwww.kek.jp/research/egs/egs5.html [3] General Particle Tracer, http://www.pulsar.nl/gpt

THPA18	Operation of the FLASH Photoinjector Laser System	laser, electron, gun, controls	507
	S. Schreiber, M. Görler, K. Klose, T. Schulz, M. Staack DESY, Hamburg, Germany G. Klemz, G. Koss DESY Zeuthen, Zeuthen, Germany I.H. Templin, I. Will, H. Willert MBI, Berlin, Germany
	The photoinjector of FLASH uses an RF gun equipped with caesium telluride photocathodes illuminated by appropriate UV laser pulses as a source of ultra-bright electron beams. The superconducting accelerator of FLASH is able to accelerate thousands of electron bunches per second in burst mode. This puts special demands on the design of the electron source, especially the laser system. The fully diode pumped laser system is based on Nd:YLF and produces a train of 2400 UV pulses in a burst of 0.8 ms length with a repetition rate of 5 Hz and 800 pulses with 10 Hz. The single pulse energy is up to 25 μJ per pulse at 262 nm. The laser uses a pulsed oscillator synchronized to the master RF with a stability of better than 200 fs in arrival time at the RF gun. Special care has been taken to produce a uniform and stable pulse train in terms of pulse energy, shape, and phase. Since FLASH is a free-electron laser user facility, the laser is designed to operate for more than 8000 h per year without operator intervention and little maintenance. We report on operational experience with the new system brought in operation in spring 2010.

THPA19	Photocathodes at FLASH	gun, laser, solenoid, electron	511
	S. Schreiber, H. Hansen, S. Lederer, H.-H. Sahling DESY, Hamburg, Germany P. Michelato, L. Monaco, D. Sertore INFN/LASA, Segrate (MI), Italy
	For several years now, caesium telluride photocathodes are successfully used in the photoinjector of the free electron laser FLASH at DESY, Germany. They show a high quantum efficiency and long lifetime. The injector produces routinely thousand of bunches per second with a single bunch charge in the range of 0.1 to 1.5 nC. Recent results on lifetime, quantum efficiency, darkcurrent, and operating experience is reported. At DESY, a new preparation system has been set-up. First cathodes have been produced and tested successfully.

THPA23	Investigations on Thermal Emittance at PITZ	emittance, laser, electron, simulation	519
	M. Otevřel, G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, B. Petrosyan, D. Richter, S. Rimjaem, A. Shapovalov, F. Stephan, G. Vashchenko, S. Weidinger DESY Zeuthen, Zeuthen, Germany S. Lederer DESY, Hamburg, Germany
	The main aim of the Photo-Injector Test Facility at DESY, location Zeuthen (PITZ) is to develop and test an FEL photo-injector system capable of producing high charge electron bunches of lowest possible transverse emittance, which has a fundamental impact on FEL performance. Recent measurement results at PITZ showed a fairly small electron beam transverse projected emittance [1] which increased interest in the thermal emittance and its contribution to the overall electron beam emittance budget. Therefore thermal emittance was investigated at PITZ. Results of these studies are presented and discussed.

THPA30	First Results with Tomographic Reconstruction of the Transverse Phase Space at PITZ	emittance, laser, booster, gun	543
	G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria D. Richter HZB, Berlin, Germany
	The development of high brightness electron sources capable to drive FELs like FLASH and European XFEL is a major objective of the Photo-Injector Test Facility at DESY in Zeuthen, PITZ. A key parameter used to define the beam quality at PITZ is the transverse phase-space density distribution and its evolution along the beamline. Complementary to the standard phase-space measurement setup constituting slit-scan stations, a module for tomographic diagnostics has been commissioned in 2010/2011. It consists of four observation screens separated by FODO cells and an upstream matching section. The expected advantages of the tomography method are the possibility to measure both transverse planes simultaneously and an improved resolution for low charges and short pulse trains. The fundamental challenges are related to strong space-charge forces at low beam momentum of only 25~MeV/c at PITZ at the moment. Such a constraint presents an obstacle to obtain beam envelope parameters well-matched to the optics of the FODO lattice. This contribution presents the first practical experience with the phase-space tomography module.

THPA31	Commissioning of ITC-RF Gun for t-ACTS Project at Tohoku University	gun, electron, radiation, coupling	547
	F. Hinode, H. Hama, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka Tohoku University, Research Center for Electron Photon Science, Sendai, Japan F. Miyahara KEK, Ibaraki, Japan
	Funding: This work is partially supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003. A test accelerator as the coherent terahertz source project (t-ACTS) is in progress at Tohoku University, in which an isochronous ring and a bunched free electron laser will provide the intense terahertz radiation by dint of the sub-picoseconds electron pulses [1, 2]. A thermionic RF gun with two independently-tunable cells (ITC), an alpha magnet and a 3 m accelerating structure are employed in the t-ACTS injector for the short pulse generation. Tracking simulations show that very short electron pulse less than 100 fs with a bunch charge of about 20 pC can be obtained by means of the velocity bunching scheme [2]. Although the usable amount of the extracted beam from the ITC-RF gun is quite small comparing with photo-injectors, there seem to be distinct features such as the better stability and the multi-bunch capability. High power RF processing for the gun has already been accomplished, and then the beam commissioning will be started soon. We will report results of beam commissioning of the ITC-RF gun and also present the current status of t-ACTS project. [1] H. Hama et al., New J. Phys. 8 (2006) 292, [2] H. Hama and M. Yasuda, Proc. of FEL2009, TUPC69, (2009) 394 [3] F. Miyahara et al., Proc. of IPAC'10, THPD094, (2010) 4509

THPA34	Assessment of Thermionic Emission Properties and Back Bombardment Effects for LaB₆ and CeB₆	gun, electron, simulation, FEL	557
	M. A. Bakr, Y.W. Choi, H. Imon, K. Ishida, T. Kii, N. Kimura, R. Kinjo, K. Komai, K. Masuda, H. Ohgaki, M. Omer, S. Shibata, K. Shimahashi, T. Sonobe, K. Yoshida, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan M. Kawai Tohoku University, School of Science, Sendai, Japan
	Back Bombardment (BB) effect limits wide usage of thermionic RF guns. BB effect induces not only ramping-up of a cathode’s temperature and beam current, but also degradation of cavity voltage and beam energy during the macropulse. In this research we are clarifying BB phenomenon and find out cathode material properties contribution on BB effect. Therefore, assessment of emission properties and comparison of BB effect in LaB6 and CeB6 are introduced. Emission properties for these materials are measured in temperature range between 1600 and 2100 K. Then, heating property of materials is investigated against BB effect by numerical calculation of stopping range and deposited heat. Finally, change in cathode temperate and corresponding change in current density during 6 μs pulse duration is determined. Experimental results estimates work functions at 1800 K for LaB6 and CeB6 were 2.8 and 2.75 eV respectively. Our simulation of BB effect shows that for a pulse of 6 μs duration, LaB6 cathode experiences a large change in temperature compared with CeB6. The change in current density is two times higher. The experimental and simulation results will be presented in the meeting

THPB14	APEX Project Phase 0 and I Status and Plans and Activities for Phase II	gun, laser, cavity, electron	582
	F. Sannibale, B.J. Bailey, K.M. Baptiste, J.M. Byrd, A.L. Catalano, D. Colomb, C.W. Cork, J.N. Corlett, S. De Santis, L.R. Doolittle, J. Feng, D. Filippetto, G. Huang, S. Kwiatkowski, W.E. Norum, H.A. Padmore, C. F. Papadopoulos, G. Penn, G.J. Portmann, S. Prestemon, J. Qiang, D.G. Quintas, J.W. Staples, M.E. Stuart, T. Vecchione, M. Venturini, M. Vinco, W. Wan, R.P. Wells, M.S. Zolotorev, F.A. Zucca LBNL, Berkeley, California, USA M. J. Messerly, M.A. Prantil LLNL, Livermore, California, USA C. Pellegrini UCLA, Los Angeles, California, USA M. Yoon POSTECH, Pohang, Kyungbuk, Republic of Korea
	Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 The APEX project at the Lawrence Berkeley National Laboratory is devoted to the development of a high repetition rate (MHz-class) electron injector for X-ray FEL applications. The injector is based on a new concept photo-gun, utilizing a normal conducting 187 MHz RF cavity operating in CW mode in conjunction with high quantum efficiency photocathodes able to deliver the required repetition rates with available laser technology. The APEX activities are staged in two phases. In Phase I, the electron photo-gun is constructed, tested and several different photo-cathodes, such as alkali antimonides, Cs₂Te [1], diamond amplifiers [2], and metals, are tested at full repetition rate. In Phase II, a pulsed linac is added for accelerating the beam at several tens of MeV to prove the high brightness performance of the gun when integrated in an injector scheme. Based on funding availability, after Phase II, the program could also include testing of new undulator technologies and FEL studies. The status of Phase I, in its initial experimental phase, is described together with plans and activities for Phase II and beyond. [1] In collaboration with INFN-LASA, Milano, Italy. [2] In collaboration with Brookhaven National Laboratory, Upton NY, USA

THPB15	Metal Cathodes with Reduced Emittance and Enhanced Quantum Efficiency	emittance, FEL, electron, photon	586
	C.M.R. Greaves, J. Feng, H.A. Padmore, W. Wan LBNL, Berkeley, California, USA D. Dowell AES, Princeton, New Jersey, USA
	In this paper, we report experimental results on photoemission from copper and silver surfaces. Using the technique of angle resolved photoemission spectroscopy (ARPES), we demonstrate that, for excess energy around 0.5 eV, the photoelectrons from the Cu(111) and Ag(111) surfaces generated by p-polarized light originate primarily from the well-known surface state with normalized emittance only a fraction of that of the polycrystalline copper cathode presently used in the RF guns. Meanwhile, we demonstrate that the enhancement of the quantum efficiency (QE) at grazing angle is closely related to the surface state as well. Furthermore, we show that the surface state can be easily restored by a simple anneal process, thus pointing to a practical way to reducing the emittance and QE of a metal cathode simultaniously.

THPB20	DC High Voltage Photoemission Electron Gun for CAEP FEL	gun, vacuum, electron, high-voltage	598
	H.B. Wang, M. Li, X. Yang CAEP/IAE, Mianyang, Sichuan, People's Republic of China
	The research on high average power Terahertz free electron laser requires more demanding specifications of electron source. DC high voltage electron guns with photoemission cathodes are a natural choice for generating the critical beams considering the condition of technology. Field emission from the electrode structures limits the operating voltage and cathode field gradient in these guns. A ceramic insulator determines the level of operating voltage. The photocathode operational lifetime is limited by the gun vacuum and by ion back bombardment. The designing thought and the technical solution to aforementioned issues are presented. The results of the beam dynamic simulation based on the design are displayed, normalized emittance at the location 120 cm far from the cathode surface: x=1.335 πmmmrad, y=1.364 πmmmrad, z=4.81 π*keV-deg, using the following initial beam parameters: the laser spot 4 mm in diameter, the laser pulse length FWHM 12 ps, the charge per bunch 35 pC and the accelerating voltage 350 kV. Now the DC photoemission gun is conditioning.

THPB29	Design of a Low Emittance and High Repetition Rate S-band Photoinjector	gun, emittance, solenoid, laser	621
	J.H. Han Diamond, Oxfordshire, United Kingdom
	One of key components for the success of X-ray free-electron lasers (FELs) is the electron injector. Injectors starting with photocathode RF guns provide exceptionally high brightness electron beams and therefore they are being adopted as injectors of X-ray FELs. In this paper we show how to improve the photoinjector performance in terms of emittance and repetition rate by means of components optimization based on mature technologies. Transverse emittance at an injector is reduced by optimizing the RF gun cavity design, gun solenoid position, and accelerating section position. The repetition rate of an injector mainly depends on the cooling capability of the gun cavity. By adopting the coaxial RF gun coupler and improving cooling-water channels of the gun, a maximum repetition rate of 1 kHz for the injector will be achieved.

THPB30	SwissFEL Injector Test Facility – Test and Plans	emittance, gun, cavity, laser	625
	M. Pedrozzi, M. Aiba, S. Bettoni, B. Beutner, A. Falone, R. Ganter, R. Ischebeck, F. Le Pimpec, G.L. Orlandi, E. Prat, S. Reiche, T. Schietinger, A. Trisorio, C. Vicario Paul Scherrer Institut, Villigen, Switzerland
	In August 2010 the Paul Scherrer Institute inaugurated the SwissFEL Injector test facility as a first step toward the Swiss hard X-ray FEL planned at PSI. The main purpose of the facility is to demonstrate and consolidate the generation of high-brightness beam as required to drive the 6 GeV SwissFEL accelerator. Additionally the injector serves as a platform supporting development and test of accelerator components/systems and optimization procedures foreseen for SwissFEL. In this paper we report on the present status of the commissioning with some emphasis on emittance measurements and component performances. The scientific program and long-term plans will be discussed as well.

Paper

Title

Other Keywords

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TUOCI1

Latest Developments for Photoinjector, Seeding and THz Laser Systems

laser, gun, electron, radiation

173

C.P. Hauri, A. Trisorio, C. Vicario
Paul Scherrer Institut, Villigen, Switzerland
C. Ruchert
PSI, Villigen PSI, Switzerland

For driving compact FEL facilities cutting edge laser technology is required. We present the latest laser developments and concepts for ultrastable and versatile electron gun lasers, seed lasers and high-power laser-based THz sources taking place at the Paul Scherrer Institute and at other Free Electron Laser facilities. Such developments are of fundamental interest for next generation FEL pump-probe experiments requiring a temporal resolution beyond state of the art.

Slides TUOCI1 [5.159 MB]

TUOC3

High QE, Low Emittance, Green Sensitive FEL Photocathodes Using K₂CsSb

emittance, electron, laser, gun

179

H.A. Padmore, D. Dowell, J. Feng, T. Vecchione, W. Wan
LBNL, Berkeley, California, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA
T. Rao, J. Smedley
BNL, Upton, Long Island, New York, USA

Funding: Work was supported by the Director, Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy, under Contract No. DE-AC02-05CH11231, KC0407-ALSJNT-I0013, and DE-SC0005713.
We describe the development of photocathodes based on Potassium-Cesium-Antimonide that satisfy many of the key requirements of future light sources, such as robustness, high quantum efficiency when excited with visible light and low transverse emittance. We have demonstrated QE of 7% at 532 nm, a normalized transverse emittance of 0.36 μm at 543 nm and 3 MV/m field gradient[1]. We have also shown that the material can be relatively robust to residual water contamination and we have extracted current densities of 1 mA/mm² with very long lifetime. We believe that this work is an important step forward in FEL development where high repetition rate is required.
[1] Applied Physics Letters (submitted)

Slides TUOC3 [4.825 MB]

TUPA21

Optical Synchronization of the SwissFEL 250 Mev Test Injector Gun Laser With the Optical Master Oscillator

laser, controls, FEL, gun

243

V.R. Arsov, S. Hunziker, M.G. Kaiser, V. Schlott
Paul Scherrer Institut, Villigen, Switzerland
F. Löhl
CLASSE, Ithaca, New York, USA

Funding: This work is partly supported by IRUVX-PP, an EU co-funded project under FP7 (Grant Agreement 211285)
The SwissFEL gun laser stability is crucial for stable SASE operation in the hard X-ray regime. In 10 pC mode in which sub-10 fs photon pulses will be delivered for the users, the gun laser arrival time jitter at the cathode shouldn't exceed 30 fs (rms). In the present design it is foreseen that the gun oscillator is optically stabilized. It is also necessary to check the stability of the combination laser oscillator and transfer line with an optical reference. For this, the Ti:Sa oscillator was used as a master laser and its pulses were delivered through a ca. 5 m long free space transfer line to optically synchronize an Er-fiber oscillator via two color balanced optical cross correlator with a BBO crystal. The two lasers were placed on different optical tables, which didn't have a mechanical connection through the transfer line. Stable optical lock for at least 60 minutes was demonstrated with an in-loop stability in the range 3.7-17.6 fs. In the range 10 Hz-1 kHz the phase noise stability of the optically locked Er-fiber oscillator varied between 76.5 fs and 118.5 fs rms, 76 fs of which was the contribution of the 1.5 GHz PLO, to which the Ti:Sa oscillator was RF-locked.

WEPA01

Commissioning of a Photoinjector in HLS

laser, emittance, solenoid, gun

331

Z.G. He, Q.K. Jia, B.G. Sun, X.H. Wang
USTC/NSRL, Hefei, Anhui, People's Republic of China

A BNL type photoinjector was installed in HLS (Hefei Light Source) and commissioning work was carrying out in last months. The dark current was measured when the high power testing of the gun was processed. The quantum efficiency (QE) of the photocathode was measured and studied, the main parameters of beam quality such as electric charge, transverse emittance and energy were measured and presented in this paper.

WEPA06

Experimental Studies with Spatial Gaussian-cut Laser for the LCLS Photocathode Gun

laser, emittance, simulation, electron

341

F. Zhou, A. Brachmann, P. Emma, A. Gilevich, Z. Huang
SLAC, Menlo Park, California, USA

Funding: U.S. Department of Energy under contract DE-AC02-76SF00515
To further enhance the LCLS injector performances or simplify its operating conditions, we are evaluating the various parameters including the photocathode drive laser. Simulations show that both the projected and time-sliced emittances with spatial Gaussian profiles having reasonable tail-cutoff are better than those with uniform one. The simulated results are also supported by theoretical analyses. In the LCLS, the spatial uniform or quasi-Gaussian laser profiles are conveniently obtained by adjusting the optics of telescope upstream of an iris, used to define laser size on the cathode. Preliminary beam studies at the LCLS show that both the projected and time-sliced emittances with spatial quasi-Gaussian laser are almost as good as, although not better than, those with uniform one, and also laser transmission through the iris with the quasi-Gaussian is twice that with uniform one, which is to ease copper cathode operations and thus improve the LCLS operation efficiency. More beam studies are planned in the coming summer to measure FEL performances with the quasi-Gaussian in comparison with the uniform one. All simulations and measurements are presented.

WEPA12

The Driving Laser for FEL-THz

laser, FEL, gun, electron

349

Y. Chen, M. Li, H.B. Wang, D. Wu, X. Yang
CAEP/IAE, Mianyang, Sichuan, People's Republic of China

A solid-state driving laser system have been developed to meet the requirements of the FEL-THz research. The design specifications, configuration and diode-pumped amplifier of the drive-laser system are also described. The laser system can generate continuous or 10μs-20μs pulses light with wavelength 10⁶⁴ nm, 532nm, 266nm at a repetition rate 54.167MHz. The average power of the driving laser system is more than 25W, 8W, 1W at wavelength 1064nm, 532nm, 266nm respectively. The cathode material is GaAs. The second harmonic is used, of which average power is 8.55W, pulse width is about 12ps, power stability is 0.72% and pointing stability is 46urad.

WEPA23

DEVELOPMENT OF AN ITC-RF GUN FOR COMPACT THz FEL

gun, electron, cavity, FEL

385

W. Bai, Y. Chen, M. Li, L.J. Shan, X.M. Shen, H.B. Wang
CAEP/IAE, Mianyang, Sichuan, People's Republic of China

An independent tunable cells thermionic rf gun (ITC-RF Gun) used for compact Tera-hertz (THz) free electron laser(FEL) is developed at Institute of Applied Electronics, China Academy of Engineering Physics (CAEP). This RF-gun consists of a single cell and a 3-cells accelerating cavity which are excited independently, so the amplitude and phase of the two parts can be adjusted easily. The paper introduces some results of the simulation, cold test and preliminary hot test. The test results agree well with the theoretical design.

WEPB20

The Design Of A Multi-Beam Electron Gun For A Photonic Free-Electron Laser

gun, electron, emittance, beam-transport

427

J.H.H. Lee, K.-J. Boller, T. Denis, P.J.M. van der Slot
Mesa+, Enschede, The Netherlands

Funding: This research is supported by the Dutch Technology Foundation STW, applied science division of NWO and the Technology Program of the Ministry of Economic Affairs.
The photonic Free-Electron Laser (pFEL) is a novel slow-wave device which relies on a photonic crystal (PhC) to synchronize the Cherenkov electromagnetic radiation generated from the co-propagating electron beams. The advantage of pFEL is in its frequency- and power-scaling properties. The scale invariance of Maxwell’s equations allows the use of the same beam energy to operate at higher frequencies when the PhC is correspondingly scaled. On the other hand, power-scaling is achieved by varying the number of electron beams propagating in parallel through the PhC. To produce a set of parallel beams, we have designed a multi-beam electron gun using flat cathodes, which produces a total current of 1 A at a beam voltage of 14 kV. We will present the design of this gun together with the expected performance. In addition, we have investigated the beam transport system and will discuss the options for guiding the beams through the PhC.

THPA10

RF Photo Gun Stability Measurement at PITZ

gun, laser, feedback, monitoring

485

I.I. Isaev, G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, Ye. Ivanisenko, G. Klemz, W. Köhler, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko, S. Weidinger, R.W. Wenndorff
DESY Zeuthen, Zeuthen, Germany
M. Hoffmann, H. Schlarb
DESY, Hamburg, Germany
M.A. Khojoyan
ANSL, Yerevan, Armenia
D. Richter
BESSY GmbH, Berlin, Germany
A. Shapovalov
MEPhI, Moscow, Russia

High stability of the RF photo gun is one of the necessary conditions for the successful operation of linac based free electron lasers. Fluctuations of the RF launch phase have significant influence on the beam quality. Investigation on the dependence of different gun parameters and selection of optimal conditions are required to achieve high RF gun phase stability. Measurements of the gun RF phase stability are based on beam charge and momentum monitoring downstream of the gun. The stability of the RF gun phase for different operating conditions has been measured at the Photo Injector Test facility at DESY in Zeuthen (PITZ) and the results will be presented.

THPA15

Simulation Studies of Generating Ultra Short Pulses at PITZ

laser, electron, emittance, simulation

499

M.A. Khojoyan, M. Krasilnikov, A. Oppelt, F. Stephan
DESY Zeuthen, Zeuthen, Germany
M.A. Khojoyan
ANSL, Yerevan, Armenia

Generation of the ultra short electron bunches (<10fs bunch length) which have a small transverse phase space volume and relatively small energy spread is of great interest. Such bunches are required for fully coherent (transversally and longitudinally) FEL radiation (single spike lasing) and for plasma acceleration experiments. The Photo Injector Test Facility at DESY in Zeuthen has already demonstrated the possibility to generate and characterize high quality electron beams for a wide range of bunch charges. Currently electron bunches have a typical length of several ps. To study the possibility of producing short electron bunches at PITZ many beam dynamics simulations have been performed for 1pC bunch charge using the ASTRA code. The current PITZ beam line is supposed to be extended by a small magnet chicane. Several temporal profiles of the cathode laser pulse have been used for the simulations to produce ultra-short electron bunches with small transverse sizes. The results of the beam dynamics simulations are presented and discussed.

THPA17

Study of the Back-bombardment Effect in the ITC-Rf Gun for t-ACTS Project at Tohoku University

gun, electron, simulation, radiation

503

X. Li, H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
F. Miyahara
KEK, Ibaraki, Japan

A specially designed thermionic RF gun which consists of two independently tunable cells [1] (ITC) is used to produce sub-picoseconds electron pulses as the source for coherent terahertz radiation at Tohoku University. Simulations of particle motion show that the back-bombardment effect on the LaB6 cathode surface is serious and should be controlled carefully. Using EGS5 [2] the power deposition of the back-bombardment inside the cathode can be calculated by using the information of back-streaming electrons derived from GPT [3] simulation, and further used to evaluate the temperature increase on the cathode surface by numerically solving a 2-dimentional equation for heat conduction. In the 2D model, the back-streaming electrons are treated as external heat source as well as the cathode heater that heats the cathode from its side along with thermal radiation from its surface. In addition, some methods will be proposed to reduce the back-bombardment effect and we will also compare the simulation results with experimental data.
[1] H. Hama et al., New J. Phys. 8 (2006) 292
[2] Electron Gamma Shower, http://rcwww.kek.jp/research/egs/egs5.html
[3] General Particle Tracer, http://www.pulsar.nl/gpt

THPA18

Operation of the FLASH Photoinjector Laser System

laser, electron, gun, controls

507

S. Schreiber, M. Görler, K. Klose, T. Schulz, M. Staack
DESY, Hamburg, Germany
G. Klemz, G. Koss
DESY Zeuthen, Zeuthen, Germany
I.H. Templin, I. Will, H. Willert
MBI, Berlin, Germany

The photoinjector of FLASH uses an RF gun equipped with caesium telluride photocathodes illuminated by appropriate UV laser pulses as a source of ultra-bright electron beams. The superconducting accelerator of FLASH is able to accelerate thousands of electron bunches per second in burst mode. This puts special demands on the design of the electron source, especially the laser system. The fully diode pumped laser system is based on Nd:YLF and produces a train of 2400 UV pulses in a burst of 0.8 ms length with a repetition rate of 5 Hz and 800 pulses with 10 Hz. The single pulse energy is up to 25 μJ per pulse at 262 nm. The laser uses a pulsed oscillator synchronized to the master RF with a stability of better than 200 fs in arrival time at the RF gun. Special care has been taken to produce a uniform and stable pulse train in terms of pulse energy, shape, and phase. Since FLASH is a free-electron laser user facility, the laser is designed to operate for more than 8000 h per year without operator intervention and little maintenance. We report on operational experience with the new system brought in operation in spring 2010.

THPA19

Photocathodes at FLASH

gun, laser, solenoid, electron

511

S. Schreiber, H. Hansen, S. Lederer, H.-H. Sahling
DESY, Hamburg, Germany
P. Michelato, L. Monaco, D. Sertore
INFN/LASA, Segrate (MI), Italy

For several years now, caesium telluride photocathodes are successfully used in the photoinjector of the free electron laser FLASH at DESY, Germany. They show a high quantum efficiency and long lifetime. The injector produces routinely thousand of bunches per second with a single bunch charge in the range of 0.1 to 1.5 nC. Recent results on lifetime, quantum efficiency, darkcurrent, and operating experience is reported. At DESY, a new preparation system has been set-up. First cathodes have been produced and tested successfully.

THPA23

Investigations on Thermal Emittance at PITZ

emittance, laser, electron, simulation

519

M. Otevřel, G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, B. Petrosyan, D. Richter, S. Rimjaem, A. Shapovalov, F. Stephan, G. Vashchenko, S. Weidinger
DESY Zeuthen, Zeuthen, Germany
S. Lederer
DESY, Hamburg, Germany

The main aim of the Photo-Injector Test Facility at DESY, location Zeuthen (PITZ) is to develop and test an FEL photo-injector system capable of producing high charge electron bunches of lowest possible transverse emittance, which has a fundamental impact on FEL performance. Recent measurement results at PITZ showed a fairly small electron beam transverse projected emittance [1] which increased interest in the thermal emittance and its contribution to the overall electron beam emittance budget. Therefore thermal emittance was investigated at PITZ. Results of these studies are presented and discussed.

THPA30

First Results with Tomographic Reconstruction of the Transverse Phase Space at PITZ

emittance, laser, booster, gun

543

G. Asova, H.-J. Grabosch, M. Groß, L. Hakobyan, I.I. Isaev, Ye. Ivanisenko, M.A. Khojoyan, G. Klemz, M. Krasilnikov, M. Mahgoub, D. Malyutin, A. Oppelt, M. Otevřel, B. Petrosyan, S. Rimjaem, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
D. Richter
HZB, Berlin, Germany

The development of high brightness electron sources capable to drive FELs like FLASH and European XFEL is a major objective of the Photo-Injector Test Facility at DESY in Zeuthen, PITZ. A key parameter used to define the beam quality at PITZ is the transverse phase-space density distribution and its evolution along the beamline. Complementary to the standard phase-space measurement setup constituting slit-scan stations, a module for tomographic diagnostics has been commissioned in 2010/2011. It consists of four observation screens separated by FODO cells and an upstream matching section. The expected advantages of the tomography method are the possibility to measure both transverse planes simultaneously and an improved resolution for low charges and short pulse trains. The fundamental challenges are related to strong space-charge forces at low beam momentum of only 25~MeV/c at PITZ at the moment. Such a constraint presents an obstacle to obtain beam envelope parameters well-matched to the optics of the FODO lattice. This contribution presents the first practical experience with the phase-space tomography module.

THPA31

Commissioning of ITC-RF Gun for t-ACTS Project at Tohoku University

gun, electron, radiation, coupling

547

F. Hinode, H. Hama, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
F. Miyahara
KEK, Ibaraki, Japan

Funding: This work is partially supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003.
A test accelerator as the coherent terahertz source project (t-ACTS) is in progress at Tohoku University, in which an isochronous ring and a bunched free electron laser will provide the intense terahertz radiation by dint of the sub-picoseconds electron pulses [1, 2]. A thermionic RF gun with two independently-tunable cells (ITC), an alpha magnet and a 3 m accelerating structure are employed in the t-ACTS injector for the short pulse generation. Tracking simulations show that very short electron pulse less than 100 fs with a bunch charge of about 20 pC can be obtained by means of the velocity bunching scheme [2]. Although the usable amount of the extracted beam from the ITC-RF gun is quite small comparing with photo-injectors, there seem to be distinct features such as the better stability and the multi-bunch capability. High power RF processing for the gun has already been accomplished, and then the beam commissioning will be started soon. We will report results of beam commissioning of the ITC-RF gun and also present the current status of t-ACTS project.
[1] H. Hama et al., New J. Phys. 8 (2006) 292,
[2] H. Hama and M. Yasuda, Proc. of FEL2009, TUPC69, (2009) 394
[3] F. Miyahara et al., Proc. of IPAC'10, THPD094, (2010) 4509

THPA34

Assessment of Thermionic Emission Properties and Back Bombardment Effects for LaB₆ and CeB₆

gun, electron, simulation, FEL

557

M. A. Bakr, Y.W. Choi, H. Imon, K. Ishida, T. Kii, N. Kimura, R. Kinjo, K. Komai, K. Masuda, H. Ohgaki, M. Omer, S. Shibata, K. Shimahashi, T. Sonobe, K. Yoshida, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan
M. Kawai
Tohoku University, School of Science, Sendai, Japan

Back Bombardment (BB) effect limits wide usage of thermionic RF guns. BB effect induces not only ramping-up of a cathode’s temperature and beam current, but also degradation of cavity voltage and beam energy during the macropulse. In this research we are clarifying BB phenomenon and find out cathode material properties contribution on BB effect. Therefore, assessment of emission properties and comparison of BB effect in LaB6 and CeB6 are introduced. Emission properties for these materials are measured in temperature range between 1600 and 2100 K. Then, heating property of materials is investigated against BB effect by numerical calculation of stopping range and deposited heat. Finally, change in cathode temperate and corresponding change in current density during 6 μs pulse duration is determined. Experimental results estimates work functions at 1800 K for LaB6 and CeB6 were 2.8 and 2.75 eV respectively. Our simulation of BB effect shows that for a pulse of 6 μs duration, LaB6 cathode experiences a large change in temperature compared with CeB6. The change in current density is two times higher. The experimental and simulation results will be presented in the meeting

THPB14

APEX Project Phase 0 and I Status and Plans and Activities for Phase II

gun, laser, cavity, electron

582

F. Sannibale, B.J. Bailey, K.M. Baptiste, J.M. Byrd, A.L. Catalano, D. Colomb, C.W. Cork, J.N. Corlett, S. De Santis, L.R. Doolittle, J. Feng, D. Filippetto, G. Huang, S. Kwiatkowski, W.E. Norum, H.A. Padmore, C. F. Papadopoulos, G. Penn, G.J. Portmann, S. Prestemon, J. Qiang, D.G. Quintas, J.W. Staples, M.E. Stuart, T. Vecchione, M. Venturini, M. Vinco, W. Wan, R.P. Wells, M.S. Zolotorev, F.A. Zucca
LBNL, Berkeley, California, USA
M. J. Messerly, M.A. Prantil
LLNL, Livermore, California, USA
C. Pellegrini
UCLA, Los Angeles, California, USA
M. Yoon
POSTECH, Pohang, Kyungbuk, Republic of Korea

Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
The APEX project at the Lawrence Berkeley National Laboratory is devoted to the development of a high repetition rate (MHz-class) electron injector for X-ray FEL applications. The injector is based on a new concept photo-gun, utilizing a normal conducting 187 MHz RF cavity operating in CW mode in conjunction with high quantum efficiency photocathodes able to deliver the required repetition rates with available laser technology. The APEX activities are staged in two phases. In Phase I, the electron photo-gun is constructed, tested and several different photo-cathodes, such as alkali antimonides, Cs₂Te [1], diamond amplifiers [2], and metals, are tested at full repetition rate. In Phase II, a pulsed linac is added for accelerating the beam at several tens of MeV to prove the high brightness performance of the gun when integrated in an injector scheme. Based on funding availability, after Phase II, the program could also include testing of new undulator technologies and FEL studies. The status of Phase I, in its initial experimental phase, is described together with plans and activities for Phase II and beyond.
[1] In collaboration with INFN-LASA, Milano, Italy.
[2] In collaboration with Brookhaven National Laboratory, Upton NY, USA

THPB15

Metal Cathodes with Reduced Emittance and Enhanced Quantum Efficiency

emittance, FEL, electron, photon

586

C.M.R. Greaves, J. Feng, H.A. Padmore, W. Wan
LBNL, Berkeley, California, USA
D. Dowell
AES, Princeton, New Jersey, USA

In this paper, we report experimental results on photoemission from copper and silver surfaces. Using the technique of angle resolved photoemission spectroscopy (ARPES), we demonstrate that, for excess energy around 0.5 eV, the photoelectrons from the Cu(111) and Ag(111) surfaces generated by p-polarized light originate primarily from the well-known surface state with normalized emittance only a fraction of that of the polycrystalline copper cathode presently used in the RF guns. Meanwhile, we demonstrate that the enhancement of the quantum efficiency (QE) at grazing angle is closely related to the surface state as well. Furthermore, we show that the surface state can be easily restored by a simple anneal process, thus pointing to a practical way to reducing the emittance and QE of a metal cathode simultaniously.

THPB20

DC High Voltage Photoemission Electron Gun for CAEP FEL

gun, vacuum, electron, high-voltage

598

H.B. Wang, M. Li, X. Yang
CAEP/IAE, Mianyang, Sichuan, People's Republic of China

The research on high average power Terahertz free electron laser requires more demanding specifications of electron source. DC high voltage electron guns with photoemission cathodes are a natural choice for generating the critical beams considering the condition of technology. Field emission from the electrode structures limits the operating voltage and cathode field gradient in these guns. A ceramic insulator determines the level of operating voltage. The photocathode operational lifetime is limited by the gun vacuum and by ion back bombardment. The designing thought and the technical solution to aforementioned issues are presented. The results of the beam dynamic simulation based on the design are displayed, normalized emittance at the location 120 cm far from the cathode surface: x=1.335 π*mm*mrad, y=1.364 π*mm*mrad, z=4.81 π*keV-deg, using the following initial beam parameters: the laser spot 4 mm in diameter, the laser pulse length FWHM 12 ps, the charge per bunch 35 pC and the accelerating voltage 350 kV. Now the DC photoemission gun is conditioning.

THPB29

Design of a Low Emittance and High Repetition Rate S-band Photoinjector

gun, emittance, solenoid, laser

621

J.H. Han
Diamond, Oxfordshire, United Kingdom

One of key components for the success of X-ray free-electron lasers (FELs) is the electron injector. Injectors starting with photocathode RF guns provide exceptionally high brightness electron beams and therefore they are being adopted as injectors of X-ray FELs. In this paper we show how to improve the photoinjector performance in terms of emittance and repetition rate by means of components optimization based on mature technologies. Transverse emittance at an injector is reduced by optimizing the RF gun cavity design, gun solenoid position, and accelerating section position. The repetition rate of an injector mainly depends on the cooling capability of the gun cavity. By adopting the coaxial RF gun coupler and improving cooling-water channels of the gun, a maximum repetition rate of 1 kHz for the injector will be achieved.

THPB30

SwissFEL Injector Test Facility – Test and Plans

emittance, gun, cavity, laser

625

M. Pedrozzi, M. Aiba, S. Bettoni, B. Beutner, A. Falone, R. Ganter, R. Ischebeck, F. Le Pimpec, G.L. Orlandi, E. Prat, S. Reiche, T. Schietinger, A. Trisorio, C. Vicario
Paul Scherrer Institut, Villigen, Switzerland

In August 2010 the Paul Scherrer Institute inaugurated the SwissFEL Injector test facility as a first step toward the Swiss hard X-ray FEL planned at PSI. The main purpose of the facility is to demonstrate and consolidate the generation of high-brightness beam as required to drive the 6 GeV SwissFEL accelerator. Additionally the injector serves as a platform supporting development and test of accelerator components/systems and optimization procedures foreseen for SwissFEL. In this paper we report on the present status of the commissioning with some emphasis on emittance measurements and component performances. The scientific program and long-term plans will be discussed as well.