Author: McKenzie, J.W.
Paper Title Page
THPOW019 Beam Characterisation and Machine Developments at VELA 3975
 
  • D. Angal-Kalinin, A.D. Brynes, F. Jackson, S.P. Jamison, J.K. Jones, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, M.D. Roper, Y.M. Saveliev, D.J. Scott, R.J. Smith, E.W. Snedden, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • S.D. Barrett, C.P. Topping, A. Wolski
    The University of Liverpool, Liverpool, United Kingdom
  • C.S. Edmonds, F. Jackson, S.P. Jamison, J.K. Jones, J.W. McKenzie, B.D. Muratori, Y.M. Saveliev, D.J. Scott, C.P. Topping, P.H. Williams, A. Wolski
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  An overview is presented of developments on VELA (Versatile Electron Linear Accelerator), an RF photo-injector with two user stations at Daresbury Laboratory. Numerous commissioning, machine development, beam characterisation and user experiments have been completed in the past year. A new beamline and a dedicated multiuser station have been commissioned and the first experiments performed. A number of measures have been taken to improve the stability of machine by mitigating a phase drift, laser beam transport drift and a coherent ~1 Hz beam oscillation. The 6D phase space of the electron beam has been characterised through quad scans, transverse tomography and with a transverse deflecting cavity.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPMR035 Bunch Length Measurements using a Transverse Deflecting Cavity on VELA 323
 
  • J.W. McKenzie, S.R. Buckley, L.S. Cowie, P. Goudket, M. Jenkins, B.L. Militsyn, A.J. Moss, A.E. Wheelhouse
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • A. Wolski
    The University of Liverpool, Liverpool, United Kingdom
 
  The VELA facility at Daresbury Laboratory in the UK includes a 5 MeV/c 2.5 cell S-band photoinjector gun. This gun operates in the "blow-out" regime with a sub-200 fs length drive laser: the resulting bunch length is determined by space-charge effects. We present measurements made with an S-band transverse deflecting cavity to characterise the bunch length as a function of charge, and as a function of the gun operating phase.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR035  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPOW037 Developments in the CLARA FEL Test Facility Accelerator Design and Simulations 797
 
  • P.H. Williams, D. Angal-Kalinin, A.D. Brynes, J.A. Clarke, F. Jackson, J.K. Jones, J.W. McKenzie, B.L. Militsyn, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R.B. Appleby
    UMAN, Manchester, United Kingdom
  • B. Kyle
    University of Manchester, Manchester, United Kingdom
 
  We present recent developments in the accelerator design of CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility at Daresbury Laboratory. In order to prioritise FEL schemes requiring the shortest electron bunches, the layout has changed significantly to enable compression at higher energy. Four proposed modes of operation are defined and tracked from cathode to FEL using ASTRA. Supplementing these baseline mode definitions with CSR-enabled codes (such as CSRTRACK) where appropriate is in progress. The FEL layout is re-optimised to include shorter undulators with delay chicanes between each radiator.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW037  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPOW028 Comparison of Model vs. Reality for VELA 1810
 
  • M.S. Toplis, J.W. McKenzie, B.D. Muratori, D.J. Scott, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  The Versatile Electron Linear Accelerator (VELA) is a facility designed to provide a high quality electron beam for accelerator systems development, as well as industrial and scientific applications. Currently, the RF gun can deliver short bunches, of the order of 100 fs to a few ps, with a charge of up to 250 pC, at the longer bunch lengths, and up to 4.5 MeV/c beam momentum. A model for the injector has been developed in ASTRA, together with a suite of scripts to create scans of the available parameters around an empirically found arbitrarily optimal working point. The space of parameters consists of everything that can be changed in the control room, and ranges from bunch charge to laser spot size on the cathode, together with all magnet settings where and if necessary. The various scans facilitate the task of identifying where exactly the accelerator is in terms of parameters and trends. Initial comparisons of screen images are made between the model and reality. Ultimately, the goal of the model is to robustly and repeatably establish a desired operating setup on a daily basis from an unknown switch on condition.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW028  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPOY040 Advancements in Single-shot Electron Diffraction on VELA at Daresbury Laboratory 1988
 
  • J.W. McKenzie, S.L. Mathisen, M.D. Roper, M. Surman
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • D.M.P. Holland
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • J.G. Underwood
    UCL, London, United Kingdom
 
  Electron diffraction on VELA at Daresbury Laboratory was first demonstrated in 2014. Since then, we have studied the machine parameter optimisation for single-shot diffraction patterns from single-crystal gold and silicon samples at bunch charges down to 60 fC. We present bunch length measurements for electron diffraction setups determined with a transverse deflecting cavity. We also discuss the current limitations of VELA for electron diffraction and the improvements to be made.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOY040  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPOW018 Simulations of Field Emitted Dark Current Dynamics in DC Photoinjectors 3971
 
  • P.J. Tipping, J.W. McKenzie, B.L. Militsyn
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  Field emission is a concern in injectors with DC photoelectron guns because of the constant generation of dark current, which is accelerated down the beam line and can deteriorate the photoemitted bunch quality and lead to hardware damage. Simulations were carried out on the co-propagation of a field emitted, dark current halo and a photoemitted bunch in a typical 350 kV gun as used in an ERL or FEL injector, followed by a single cell buncher cavity. The photoemitted bunch repelled the halo longitudinally, leaving the area in the centre of the bunch with very low dark current, surrounded by two peaks of relatively high current at the front and back of the bunch. The peaks in current occur at all levels of dark current and were about 3.5 times the amplitude of the undisturbed dark current. The buncher caused the dark current to overcompress, forming a 'ghost' pulse an order of magnitude larger than the initial level of dark current, in front of the photoemitted bunch.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW018  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)