A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  

Douglas, D.

Paper Title Page
MOOAAB03 High Power Operation of the JLab IR FEL Driver Accelerator 83
  • S. V. Benson, K. Beard, G. H. Biallas, J. Boyce, D. B. Bullard, J. L. Coleman, D. Douglas, H. F.D. Dylla, R. Evans, P. Evtushenko, C. W. Gould, A. C. Grippo, J. G. Gubeli, D. Hardy, C. Hernandez-Garcia, C. Hovater, K. Jordan, J. M. Klopf, R. Li, S. W. Moore, G. Neil, M. Poelker, T. Powers, J. P. Preble, R. A. Rimmer, D. W. Sexton, M. D. Shinn, C. Tennant, R. L. Walker, G. P. Williams, S. Zhang
    Jefferson Lab, Newport News, Virginia
  Funding: This work supported by the Off. of Naval Research, the Joint Technology Off., the Commonwealth of Virginia, the Air Force Research Lab, Army Night Vision Lab, and by DOE Contract DE-AC05-060R23177.

Operation of the JLab IR Upgrade FEL at CW powers in excess of 10 kW requires sustained production of high electron beam powers by the driver ERL. This in turn demands attention to numerous issues and effects, including: cathode lifetime; control of beamline and RF system vacuum during high current operation; longitudinal space charge; longitudinal and transverse matching of irregular/large volume phase space distributions; halo management; management of remnant dispersive effects; resistive wall, wake-field, and RF heating of beam vacuum chambers; the beam break up instability; the impact of coherent synchrotron radiation (both on beam quality and the performance of laser optics); magnetic component stability and reproducibility; and RF stability and reproducibility. We discuss our experience with these issues and describe the modus vivendi that has evolved during prolonged high current, high power beam and laser operation.

slides icon Slides  
MOPAS074 Combined Panofsky Quadrupole & Corrector Dipole 602
  • G. H. Biallas, D. Douglas, T. Hiatt, K. Jordan
    Jefferson Lab, Newport News, Virginia
  • N. T. Belcher
    The College of William and Mary, Williamsburg
  Funding: Work supported by the US DOE Contract #DE-AC05-84ER40150, the Office of Naval Research, The Air Force Research Laboratory, the US Army Night Vision Laboratory and the Commonwealth of Virginia,

Two styles of Panofsky Quadrupoles with integral corrector dipole windings are in use in the electron beam line of the Free Electron Laser at Jefferson Lab. We combined the functions into single magnets, adding hundreds of Gauss-cm dipole corrector capability to existing quadrupoles because space is at a premium along the beam line. Superposing high quality dipole corrector field on a high quality, weak (600 to 1'000 Gauss) quadrupole is possible because the parallel slab iron yoke of the Panofsky Quadrupole acts as a window frame style dipole yoke. The dipole field is formed when two current sources, designed and made at Jlab, add and subtract current from the two opposite quadrupole current sheet windings parallel to the dipole field direction. The current sources also drive auxiliary coils at the yoke's inner corners that improve the dipole field. Magnet measurements yielded the control system field maps that characterize the two types of fields. Details of field analysis using OPERA, construction methods, wiring details, magnet measurements and the current sources are presented.

TUPMS062 National High Magnetic Field Laboratory FEL Injector Design Consideration 1323
  • P. Evtushenko, S. V. Benson, D. Douglas, G. Neil
    Jefferson Lab, Newport News, Virginia
  A Numerical study of beam dynamics was performed for two injector systems for the proposed National High Magnetic Field Laboratory at the Florida State University (FSU) Free Electron Laser (FEL) facility. The first considered a system consisting of a thermionic DC gun, two buncher cavities operated at 260 MHz and 1.3 GHz and two TESLA type cavities, and is very similar to the injector of the ELBE Radiation Source. The second system we studied uses a DC photogun (a copy of JLab FEL electron gun), one buncher cavity operated at 1.3 GHz and two TESLA type cavities. The study is based on PARMELA simulations and takes into account operational experience of both the JLab FEL and the Radiation Source ELBE. The simulations predict the second system will have a much smaller longitudinal emittance. For this reason the DC photo gun based injector is preferred for the proposed FSU FEL facility.  
TUPMS065 JLAMP: An Amplifier Based FEL in the JLab SRF ERL Driver 1329
  • K. Jordan, S. V. Benson, D. Douglas, P. Evtushenko, C. Hernandez-Garcia, G. Neil
    Jefferson Lab, Newport News, Virginia
  Funding: This work supported by the Off. of Naval Research, the Joint Technology Off., the Commonwealth of Virginia, the Air Force Research Lab, Army Night Vision Lab, and by DOE Contract DE-AC05-060R23177.

Notional designs for ERL-driven high average power free electron lasers often invoke amplifier-based architectures. To date, however, amplifier FELs have been limited in average power output to values several orders of magnitude lower than those demonstrated in optical-resonator based systems; this is due at least in part to the limited electron beam powers available from their driver accelerators. In order to directly contrast the performance available from amplifiers to that provided by high-power cavity-based resonators, we have developed a scheme to test an amplifier FEL in the JLab SRF ERL driver. We describe an accelerator system design that can seamlessly and non-invasively integrate a 10 m wiggler into the existing system and which provides, at least in principle, performance that would support high-efficiency lasing in an amplifier configuration. Details of the design and an accelerator performance analysis will be presented.

THOAC04 RMS Emittance Measurements Using Optical Transition Radiation Interferometry at the Jefferson Lab FEL 2645
  • M. A. Holloway, R. B. Fiorito, P. G. O'Shea, A. G. Shkvarunets
    UMD, College Park, Maryland
  • S. V. Benson, W. Brock, J. L. Coleman, D. Douglas, R. Evans, P. Evtushenko, K. Jordan, D. W. Sexton
    Jefferson Lab, Newport News, Virginia
  Funding: Office of Naval Research Joint Technology Office

Optical Transition Radiation Interferometry (OTRI) has proven to be effective tool for measuring rms beam divergence. We present rms emittance measurement results of the 115 MeV energy recovery linac at the Thomas Jefferson National Laboratories Free electron Laser using OTRI. OTRI data from both near field beam images and far field angular distribution images give evidence of two spatial and angular distributions within the beam. Using the unique features of OTRI we segregate the two distributions of the beam and estimate separate rms emittance values for each component.

slides icon Slides  
THPAS073 Simplified Charged Particle Beam Transport Modeling Using Commonly Available Commercial Software 3651
  • D. Douglas, K. Beard, J. Eldred, P. Evtushenko, A. Jenkins, S. W. Moore, L. Osborne, D. W. Sexton, C. Tennant
    Jefferson Lab, Newport News, Virginia
  Funding: Supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Air Force Research Laboratory, Army Night Vision Lab, and by DOE Contract DE-AC05-060R23177.

Particle beam modeling in accelerators has been the focus of much effort (at great expense) since the 1950s. Several generations of tools have resulted from this process, each leveraging both the understanding provided by predecessors and the availability of increasingly powerful computer hardware. Nonetheless, the process remains on-going, in part due to innovations in accelerator design, construction, and operation that result in machines not easily described by existing tools. We discuss a novel response to this issue, which was encountered when Jefferson Lab began operation of its energy-recovering linacs. As such machines are not conveniently described using legacy software, a machine model was been built using Microsoft Excel. This interactive simulation can query data from the accelerator, use it to compute machine parameters, analyze difference orbit data, and evaluate beam properties. It can also derive new accelerator tunings and rapidly evaluate the impact of changes in machine configuration. As it is spreadsheet-based, it can be easily user-modified in response to changing requirements. Examples for the JLab IR Upgrade FEL are presented.