Author: Niknejadi, P.
Paper Title Page
MOPWA069 Time-resolved Electron Beam Position Monitor Macropulse Waveform Measurement in MkV Linear Accelerator at University of Hawaii Free Electron Laser Laboratory 837
  • P. Niknejadi, M.R. Hadmack, B.T. Jacobson, J. Madey, G.S. Varner
    University of Hawaii, Honolulu, HI, USA
  Real time waveform measurements of electron beams will provide valuable data and possibility of online bunch diagnostics in linear accelerators. The University of Hawaii Linear Accelerator utilizes a thermionic LaB6 cathode microwave gun injector and a single section of S-band linear accelerator capable of producing a 40MeV, 1-2 ps bunched electron beam with average current of 200mA over the duration of a 4.5 us macropulse. This beam, pulsed at 4 Hz, produces strong RF signal at 2.856 GHz which is coupled out of the beam-pipe by a family of stripline beam position monitors (BPM's) and read out using custom built logarithmic-difference based electronics installed in 2012.* A high speed Analog to Digital Convertor and Field-Programmable Gate Array will be used to digitize the signal and record the waveform. The goal is to make a cost effective oscilloscope on a chip/board with feasible and functional operation to achieve optimal beam configuration. The circuit board design, in-circuit programming, waveform digitization challenges, and preliminary results from the prototype will be presented at the conference.
* B. T. Jacobson, M. R. Hadmack, J. M. J. Madey, P. Niknejadi "Modular Logarithmic Amplifier Beam Position Monitor Readout System at University of Hawai’i," IBIC Conf. Proc. (2012)
WEPWA072 Design and Commissioning of Chasman-­Green Double Bend Achromatic Lattice Linear Transport Line at the University of Hawai'i MkV Accelerator Facility 2280
  • B.T. Jacobson, J. Madey, P. Niknejadi
    University of Hawaii, Honolulu, HI, USA
  The design of the Double Bend Achromat (DBA) lattice was originally motivated by the desire to increase the brightness of a synchrotron ring by storing a low emittance electron beam*. Alternating the direction of the bends in the DBA lattice turns the ring into a linear transport line, which has advantages over the straight transport lines typically used in linac FEL's. The dipoles in the DBA cells provide synchrotron images of the electron beam, a real-time non-destructive diagnostic during operation. As in circular machines, sections between DBA cells provide a low-emittance dispersion free beam for insertion devices such as FEL's and inverse Compton backscattering sources. This paper describes an example linear DBA, which has been designed and commissioned as part of the MkV 40 MeV electron accelerator facility at the University of Hawaii.
* Renate Chasman and G. Kenneth Green "Preliminary Design of a Dedicated Synchrotron Radiation Facility", IEEE Transactions on Nuclear Science, NS­22(3):1765-­1767, June 1975