Author: Evtushenko, P.E.
Paper Title Page
MOPF17 Optical System with Image Intensifier and Spatial Filters for Large Dynamic Range Transverse Beam Profile Measurements 247
  • P.E. Evtushenko
    JLAB, Newport News, Virginia, USA
  Funding: Work supported by US DOE office of Basic Energy Sciences under the early career program; DOE award number FWP#JLAB-BES11-05
We have previously reported * on transverse beam profile measurements where dynamic range (DR) was increase by a factor of 100 from typical 500 to about 5.0x104. It was shown that for non-equilibrium beam with non-Gaussian transverse distribution the RMS beam size can depend significantly on the DR used for calculations. Consequently, measured emittance and Twiss parameters depend on the DR as well. For the optical system used in * diffraction limits the DR at the level slightly above the 5.0x104 used in measurements. For further increase of the DR spatial filters needs to be used in a way similar to original solar coronagraph ** and its application to the synchrotron radiation measurements ***. To increase overall sensitivity to allow large dynamic range measurements with low duty cycle tune-up beam, our systems includes an image intensifier. On contrary to a coronagraph-like scheme, where central bright part of the distribution is not measured, our systems is intended for simultaneous, complete distribution measurements including the bright core and low amplitude halo, which is needed for proper beam size measurements. Here design considerations for the system are presented.
* P. Evtushenko et al., in Proceedings of FEL2012
** B. F. Lyot, Month. Notice Roy. Ast. Soc, p580, 99 (1939)
*** T. Mitsuhashi, “Beam halo observation by coronagraph”, Proceedings of DIPAC05
TUPC30 Design of Strip-Line BPM for Large Thermal Stress Conditions 442
  • P.E. Evtushenko, F.E. Hannon
    JLAB, Newport News, Virginia, USA
  • B. Wustmann
    HZDR, Dresden, Germany
  Jefferson Lab FEL operates DC photo gun and GaAs photocathode. Operation with average current of several mA and sufficiently long cathode lifetime requires pressure in the gun region at least at the 10-11 Torr level or better. To achieve such low pressure the gun chamber and the adjacent beam line are baked for an extended period of time. This imposes an additional requirement of withstanding the bake on all diagnostic elements. Additionally, analyzing beam line temperature in a high current energy-recovering linac as ones considered for future light sources, it was found that due to the short bunch length the resistive wall losses can be very high, which can cause large thermal stress to the beam line elements. With these in mind we have designed a modified strip-line beam position monitor with a flexible connection between the stip-line electrode and the central pin of conflate mounted SMA feedthrough. The design is based on a BPM previously developed for radiation source ELBE. To make manufacturing of the BPM more precise and less costly, brazing is used in place of welding. Mechanical and microwave design of the BPM is presented with initial microwave characterization.  
WEPC42 Design of a Time-Resolving Laser Wire for Large Dynamic Range Measurements 786
  • P.E. Evtushenko, M. Marchlik
    JLAB, Newport News, Virginia, USA
  Funding: Work supported by US DOE office of Basic Energy Sciences under the early career program; DOE award number FWP#JLAB-BES11-05
Better diagnostics and understanding of beam halo are needed for high average current CW SRF electron linacs. Here longitudinal beam halo upstream of the linac evolves in to transverse halo downstream of the linac. A diagnostic for measurements longitudinal phase space distribution with large dynamic range (LDR) is needed for proper setup of an injector and better understanding of beam halo formation. In addition, one of unsolved ERL’s diagnostic problems is the transverse beam size monitoring of a high average current, few MeV energy beam. We present our design for a Thomson scattering based CW laser wire system for LDR transverse beam profile measurements. It is designed to be used with CW beam starting with an average current of about 150 μA, but can, as it is non-destructive and non-intercepting, be use at any average current. When implemented in a dispersive section it can be used for energy distribution measurements. Using a short pulse laser adds time resolution to the diagnostic. Combining time and energy resolution, the system will allow measurements of the longitudinal phase space distribution while keeping the LDR due to the counting nature of the detection scheme.