Author: Krasilnikov, M.
Paper Title Page
TUPAB034 Development of Multi-Alkali Antimonides Photocathodes for High-Brightness RF Photoinjectors 1416
 
  • S.K. Mohanty, M. Krasilnikov, A. Oppelt, H.J. Qian, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • G. Guerini Rocco, C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • P. Michelato, L. Monaco, D. Sertore
    INFN/LASA, Segrate (MI), Italy
 
  Multi-alkali antimonide-based photocathodes are suitable candidate for the electron sources of next-generation high brightness RF photoinjectors due to their excellent photoemissive properties especially, like low thermal emittances and high sensitivity to visible light. The former stands out, paving the way towards CW operations. Based on the previous successful development of Cesium Telluride photocathodes, we are now channelling our efforts toward an R&D activity focused on KCsSb and NaKSb(Cs) photocathodes. Parallel to that R&D activity, we have installed a new dedicated photocathode production system at the INFN-LASA to start the preparation of these photocathodes for their test in the PITZ photoinjector at DESY in Zeuthen. In this paper, detailed experimental results obtained from the KCsSb, along with a preliminary result from the NaKSb(Cs) photocathode material as well as the status of the overall project are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB034  
About • paper received ※ 19 May 2021       paper accepted ※ 21 June 2021       issue date ※ 31 August 2021  
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TUPAB071 Beam Line Design and Instrumentation for THz@PITZ - the Proof-of-Principle Experiment on a THz SASE FEL at the PITZ Facility 1528
 
  • T. Weilbach, P. Boonpornprasert, G.Z. Georgiev, G. Koss, M. Krasilnikov, X. Li, A. Lueangaramwong, F. Mueller, A. Oppelt, S. Philipp, F. Stephan, L.V. Vu
    DESY Zeuthen, Zeuthen, Germany
  • H. Shaker
    CLS, Saskatoon, Saskatchewan, Canada
 
  In order to allow THz pump-X-ray probe experiments at full bunch repetition rate for users at the European XFEL, the Photo Injector Test Facility at DESY in Zeuthen (PITZ) is building a prototype of an accelerator-based THz source. The goal is to generate THz SASE FEL radiation with a mJ energy level per bunch using an LCLS-I undulator driven by the electron beam from PITZ. Therefore, the existing PITZ beam line is extended into a tunnel annex downstream of the existing accelerator tunnel. The beam line extension in the PITZ tunnel consists of three quadrupole magnets, a bunch compressor, a collimation system and a beam dump. In the second tunnel a dipole magnet allows to serve two beam lines, one of them the THz@PITZ beam line. It consists of one LCLS-I undulator for the production of the THz radiation, a quadrupole triplet in front of it and a quadrupole doublet behind it. For the electron beam diagnostic six new screen stations are built, three of them also allow for the observation of the THz radiation for measurements. In addition six BPMs and a new BLM system for machine protection and FEL gain curve measurement will be installed. The progress of this work will be presented.  
poster icon Poster TUPAB071 [1.978 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB071  
About • paper received ※ 18 May 2021       paper accepted ※ 14 June 2021       issue date ※ 13 August 2021  
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WEPAB040 Characterization of Low Emittance Electron Beams Generated by Transverse Laser Beam Shaping 2690
 
  • M. Groß, N. Aftab, P. Boonpornprasert, G.Z. Georgiev, J. Good, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, D. Melkumyan, S.K. Mohanty, R. Niemczyk, A. Oppelt, H.J. Qian, G. Shu, F. Stephan, G. Vashchenko
    DESY Zeuthen, Zeuthen, Germany
  • Y. Chen, G. Loisch
    DESY, Hamburg, Germany
  • I. Will
    MBI, Berlin, Germany
 
  Linac based X-ray free electron laser demand a high beam quality from the electron source, therefore RF photoinjectors are used to generate the electron bunches for state of the art beam brightness. One important figure of merit for these injectors is the transverse emittance of the generated electron beam, which can be minimized by shaping the photocathode laser pulses. Best performance can be achieved with ellipsoidal laser pulses, but 3D shaping is technically challenging. Typically, a quasi-uniform transverse laser profile is truncated from the Gaussian profile generated by the laser with an aperture to reduce the transverse nonlinear space charge forces. This is investigated in detail by optimizing the laser transverse profile at the Photoinjector Test facility at DESY in Zeuthen (PITZ), where photoinjector R&D is conducted for the E-XFEL and FLASH free electron lasers at DESY in Hamburg. In this contribution we present experimental results at high acceleration gradients (up to 60 MV/m) for both 250 pC and 500 pC. For a bunch charge of 500 pC an emittance reduction of about 30% compared to the commonly used transverse flat-top laser distribution was achieved.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB040  
About • paper received ※ 17 May 2021       paper accepted ※ 02 June 2021       issue date ※ 19 August 2021  
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WEPAB101 An Improved Model for Photoemission of Space Charge Dominated Picosecond Electron Bunches: Theory and Experiment 2829
 
  • S.M. Polozov, V.I. Rashchikov
    MEPhI, Moscow, Russia
  • M. Krasilnikov
    DESY Zeuthen, Zeuthen, Germany
 
  The emission of a short highly charged electron bunch in a radiofrequency photogun is discussed. The traditional space charge limited emission numerical model is extended by an introduction of positively charged ions arising in the cathode region and dynamically changing during the emission. Estimates on the time characteristics of the charge migrating process in the semiconductor region are given. The numerical results are compared with the results of other numerical models and with experimental observations at the Photo Injector Test facility at DESY in Zeuthen (PITZ).  
poster icon Poster WEPAB101 [1.601 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB101  
About • paper received ※ 08 May 2021       paper accepted ※ 07 June 2021       issue date ※ 19 August 2021  
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WEPAB115 Beam Preparation with Temporally Modulated Photocathode Laser Pulses for a Seeded THz FEL 2866
 
  • G.Z. Georgiev, N. Aftab, P. Boonpornprasert, J. Good, M. Groß, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, A. Lueangaramwong, D. Melkumyan, S.K. Mohanty, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach
    DESY Zeuthen, Zeuthen, Germany
  • N. Chaisueb
    Chiang Mai University, Chiang Mai, Thailand
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  The need for carrier-envelope-phase (CEP) stable THz pump pulses is recognized at many pump-probe experiments at the European XFEL. At the Photo Injector Test Facility at DESY in Zeuthen (PITZ), a proof-of-principle experiment of an accelerator-based THz FEL source is in preparation. Since the CEP stability of FEL pulses is not guaranteed in the SASE regime, a seeding scheme is needed. A common scheme for seeding is to drive the microbunching process with external laser pulses, which are power-limited in the THz range. Alternatively, a pre-bunched beam, generated for example by applying a temporally modulated photocathode laser pulse, can be used to drive the FEL. The beam dynamics with such a seeding method are studied with ASTRA tracking code simulations with space-charge forces as well as experimentally. The results of these studies are shown and discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB115  
About • paper received ※ 19 May 2021       paper accepted ※ 27 July 2021       issue date ※ 26 August 2021  
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WEPAB257 Matching of a Space-Charge Dominated Beam into the Undulator of the THz SASE FEL at PITZ 3244
 
  • X. Li, Z. Aboulbanine, G.D. Adhikari, N. Aftab, Z.G. Amirkhanyan, P. Boonpornprasert, M.E. Castro Carballo, N. Chaisueb, G.Z. Georgiev, J. Good, M. Groß, C. Koschitzki, M. Krasilnikov, O. Lishilin, A. Lueangaramwong, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach
    DESY Zeuthen, Zeuthen, Germany
 
  The Photo Injector Test facility at DESY in Zeuthen (PITZ) is developing a THz SASE FEL as a prototype high repetition rate accelerator-based source for the THz-pumped, X-ray-probed experiments at the European XFEL. For the generation of THz pulses of mJ-level energy from SASE, an electron beam with a high charge (up to 4 nC) and high peak current (~200 A) will be injected into an LCLS-I undulator, which is currently being installed at the end of the photo-injector. The narrow vacuum chamber (11x5 mm) between the magnetic poles and the strong vertical focusing from the undulator, as well as the lack of beam diagnostics, have made it a challenge to match the space-charge dominated beam into the undulator without beam loss during the following transport. In this paper, boundary conditions of a matched electron beam will be discussed and the simulation and experimental study on our matching strategy will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB257  
About • paper received ※ 08 May 2021       paper accepted ※ 02 July 2021       issue date ※ 13 August 2021  
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WEPAB274 Numerical Study of Beam Dynamics in PITZ Bunch Compressor 3285
 
  • A. Lueangaramwong, Z. Aboulbanine, G.D. Adhikari, N. Aftab, P. Boonpornprasert, N. Chaisueb, G.Z. Georgiev, J. Good, M. Groß, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, D. Melkumyan, H.J. Qian, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach
    DESY Zeuthen, Zeuthen, Germany
  • H. Shaker
    CLS, Saskatoon, Saskatchewan, Canada
 
  A magnetic bunch compressor has been recently designed for an accelerator-based THz source which is under development at the Photo Injector Test facility at DESY in Zeuthen (PITZ). The THz source is assumed to be a prototype for an accelerator-based THz source for pump-probe experiments at the European XFEL. As an electron bunch is compressed to achieve higher bunch currents for the THz source, we investigate the beam dynamics in the bunch compressor by numerical simulations. A start-to-end simulation optimizer has been developed by combining the use of ASTRA, IMPACT-T, and OCELOT to support the design of the THz source prototype. Coherent synchrotron radiation effects degrade the compression performance for our study cases with bunch charges up to 4 nC and beam energy of 17 MeV at a bending angle of 19 degrees. Simulation and preliminary beam characteristic results will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB274  
About • paper received ※ 11 May 2021       paper accepted ※ 06 July 2021       issue date ※ 23 August 2021  
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THPAB049 Modeling the Magnetic Field of the LCLS-I Undulator for THz@PITZ 3855
 
  • M. Krasilnikov, X. Li, A. Lueangaramwong, F. Mueller, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • A. Brachmann, H.-D. Nuhn
    SLAC, Menlo Park, California, USA
  • M. Tischer, P. Vagin
    DESY, Hamburg, Germany
 
  Funding: This work was supported by the European XFEL research and development program
An accelerator-based THz source for pump-probe experiments at the European XFEL is under development at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). For the proof-of-principle experiments an LCLS-I undulator is planned to be installed downstream of the PITZ accelerator. The fields of the undulator module 26 have been re-measured at DESY in Hamburg and the results are consistent with earlier SLAC measurements. A model for 3D field reconstruction based on the undulator magnetic measurements has been developed. It includes also a horizontal gradient of the vertical field. Tracking of the 17 MeV/c beam has revealed that the transverse gradient will lead to a significant off-axis trajectory in the horizontal plane. This offset has to be corrected with a steering coil, the design of which is also presented. The performance of the THz generation with the correction coil is discussed as well.
 
poster icon Poster THPAB049 [1.409 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB049  
About • paper received ※ 12 May 2021       paper accepted ※ 12 July 2021       issue date ※ 02 September 2021  
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FRXB06
Direct response time measurements on semiconductor photocathodes  
 
  • G. Loisch, M. Groß, D.K. Kalantaryan, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, F. Stephan, G. Vashchenko, T. Weilbach
    DESY Zeuthen, Zeuthen, Germany
  • Y. Chen, S. Lederer
    DESY, Hamburg, Germany
  • L. Monaco, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  Semiconductor photocathodes like Cs2Te enable stable electron sources with high photon to electron conversion rate (quantum efficiency, QE) for high brightness photoinjectors. Besides QE, work function and vacuum stability, bunch lengthening is a key figure of merit for these sources, resulting from UV photon penetration into the semiconductor and scattering of excited electrons before emission. These processes and their statistical variation lead to a delay, as well as to lengthening of the extracted electron bunch w.r.t. the incident laser pulse, often referred to as "response time". Thus far, no direct measurement of the response time of Cs2Te, one of the most widely used cathode materials, has been reported. As such a measurement is crucial for photocathode laser based bunch shaping, short bunch applications, emission modeling and for evaluating new cathode materials like CsKSb, a measurement procedure has been established at the photoinjector test facility at DESY in Zeuthen (PITZ) to measure longitudinal bunch shape variation due to cathode emission effects. Here, we introduce the method and show first results on direct cathode response measurements of Cs2Te cathodes.  
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