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Piot, P.

Paper Title Page
TUP045 Generation of Femtosecond Bunch Trains Using a Longitudinal-to-Transverse Phase Space Exchange Technique 498
 
  • Y.-E. Sun, P. Piot
    Fermilab, Batavia
 
 

Funding: Work supported by the Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. DOE and by Northern Illinois University under Contract No. DE-FG02-08ER41532 with the U.S. DOE
We demonstrate analytically and via numerical simulation, how a longitudinal-to-transverse phase space manipulation* can be used to produce a train of femtosecond electron bunches. The technique uses an incoming transversely-modulated electron beam obtained via destructive (e.g. using a multislits mask) or non destructive (e.g. transversely shaping the photocathode drive laser) methods. A transverse-to-longitudinal exchanger insertion is used to map this transverse modulation into a temporal modulation. Limitation of the proposed method and scalability to the femtosecond regime are analysed analytically and with the help of numerical simulation. Application of the method to generation of super-radiant far infrared (and shorter wavelength) radiation in an FEL is explored. Finally, a proof-of-principle experiment is discussed in the context of the Fermilab's A0 photoinjector.


*P. Emma, Z. Huang, K.-J. Kim, and P. Piot, Phys. Rev. ST Accel. Beams 9, 100702 (2006).

 
TUP107 Longitudinal Beam Diagnostics for the ILC Injectors and Bunch Compressors 655
 
  • P. Piot
    Fermilab, Batavia
  • A. Bracke, T.J. Maxwell, D. Mihalcea, M.M. Rihaoui
    Northern Illinois University, DeKalb, Illinois
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio
  • J.G. Power
    ANL, Argonne
 
 

Funding: Work supported by US. Department of Energy, under Contract No. DE-FG02-06ER41435 with Northern Illinois University.
We present a diagnostics suite and analyze techniques for setting up the longitudinal beam dynamics in ILC electron injectors and bunch compressors. Techniques to measure first order moment and recover the first order longitudinal transfer map of the injector intricate bunching scheme are presented. Coherent transition radiation diagnotics needed to measure and monitor the bunch length downstream of the ~5 GeV bunch compressor are investigated using a vector diffraction model. We finally introduce a new diagnostics capable of measuring time-transverse correlation along a single bunch. Such a diagnostics should be valuable for controlling emittance dilution via transverse wakefield and for properly setting the crab cavities needed for maximizing luminosity for non-zero crossing angle at the interaction point.

 
TUP069 Low Energy Photoemission Electron Source for Applications in THz Radiation Production and Time-Resolved Electron Microscopy 554
 
  • N. Vinogradov, P. Piot, C.R. Prokop
    Northern Illinois University, DeKalb, Illinois
  • J.W. Lewellen, J. Noonan
    ANL, Argonne
 
 

Funding: Work supported by the Department of Education under contract P116Z010035 with Northern Illinois University.
A simple, inexpensive, and compact low-energy (~20 KeV) photoemission electron source was designed, built and recently commissioned. It uses a commercial ultraviolet photocathode drive laser producing 3 ns RMS pulse. The source will eventually be used to drive a table-top THz radiation source, based on the Smith-Purcell free-electron laser scheme, and could also have potential application to time-resolved electron microcopy. We present experimental measurements of the photoemitted electron beam and numerical simulations of the anticipated parameters. We also discuss the generation of flat beams required to efficiently drive the THz radiation source.

 
TUP103 Analysis of Halo Formation in a DC Photoinjector 645
 
  • D. Mihalcea, P. Piot
    Northern Illinois University, DeKalb, Illinois
 
 

Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University
We discovered, by modeling the AES/JLab direct-current photoinjector with several beam-simulation codes, that nominal injector settings would create a large diffuse beam halo as a consequence of the internal space-charge force in the beam. The injector-induced halo is sensitive to the injector settings, but if the settings are judiciously chosen, it can be largely circumvented. We present an exploration of the parameter space for the AES/JLab photoinjector. Measurement of beam halo will be a crucial aspect of commissioning this machine.

 
TUP104 A High-Brightness Low-Energy Photoinjector Option for the Fermilab Electron Accelerator Facility 648
 
  • P. Piot, D. Mihalcea
    Northern Illinois University, DeKalb, Illinois
  • M. Church, S. Nagaitsev, Y.-E. Sun
    Fermilab, Batavia
  • I.V. Pogorelov
    LBNL, Berkeley, California
 
 

Funding: Work supported by Fermi Research Alliance LLC. Under DE-AC02- 07CH11359 with the U.S. DOE and by the Department of Education under contract P116Z010035 with Northern Illinois University
Fermilab is currently constructing a GeV-scale electron accelerator test facility. The accelerator will serve as a backbone for several Fermilab R&D programs, e.g., to test subsystem associated to project-X, ILC and the muon collider program. It is also anticipated that this facility will support beam physics and accelerator R&D programs such as testing of novel acceleration techniques, beam diagnostics and radiation sources concepts. In this paper we describe a possible option for the electron injector based on a photoemission rf gun. Optimization and performance studies of this ~50 MeV photoinjector are performed with various tracking programs (Astra, GPT, Impact-T, Impact-Z). We explore the performances of the magnetic bunch compressor which is extremely challenging at 50 MeV due to strong phase space dilution via collective effects (space charge and coherent synchrotron radiation). We also investigate the generation of flat beams with very high transverse emittance ratio using a round-to-flat beam transformer.

 
TUP105 Simulation of the Upgraded Photoinjector for the 10 kW JLAB IR-FEL 649
 
  • D. Mihalcea, P. Piot
    Northern Illinois University, DeKalb, Illinois
  • C. Hernandez-Garcia, S. Zhang
    JLAB, Newport News, Virginia
 
 

Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University
The photoinjector of the JLab 10 kW IR FEL was recently upgraded: a new photocathode drive laser was commissioned and the booster section was replaced with 7-cell cavities. In this paper we present numerical simulation and optimization of the photoinjector perform with ASTRA, IMPACT-T and IMPACT-Z beam dynamics codes. We perform these calculations for two operating voltage of the dc gun: the nominal 350 keV and the planned 500 keV operating points.

 
TUP106 Simulation of Field-Emission Cathodes for High Current Electron Injectors 652
 
  • D. Mihalcea, P. Piot
    Northern Illinois University, DeKalb, Illinois
 
 

Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University
From the prospect of the high average current electron injectors, the most important advantage of the field-emission cathodes is their capability to generate very large current densities. Simulation of field-emission cathodes is complicated by the large range of spatial dimensions: from sub-micron scale, for a single field-emission tip, to millimeter scale, for a field-emitter array. To overcome this simulation challenge our numerical model is split in two steps. In the first step, only electrons emitted by a single tip are considered. In the second step, the beams originating from many single emitting tips are merged together to mimic the field-emitter array configuration. We present simulation results of injector based on field array emitters cathodes.

 
TUP117 Development of Ultra-Low Emittance Injector for Future X-Ray FEL Oscillator 676
 
  • P.N. Ostroumov, K.-J. Kim
    ANL, Argonne
  • P. Piot
    Northern Illinois University, DeKalb, Illinois
 
 

Funding: This work was supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC-02-06CH11357.
An XFELO proposed recently* requires a continuous sequence of electron bunches with ultra-low transverse emittance less than 0.1 mm-mr, a bunch charge of 40 pC, an rms energy spread of 1.4 MeV, repeating at a rate between 1 MHz to 100 MHz. The bunches are to be compressed to an rms lengths less than 2 ps at the final energy of 7 GeV. Following the successful commissioning of the pulsed injector based on a thermionic gun** we discuss a concept for ultra-low emittance injector to produce 100 MHz CW electron bunches. The electron beam is extracted by ~1MV rf voltage using low frequency ~100 MHz room temperature rf cavity. The injector also includes a chicane and slits to form a short ~1 nsec bunch, a pre-buncher a booster buncher to form low longitudinal emittance of the bunched beam, an accelerating section to ~50 MeV using higher harmonic cavities, and an rf cosine-wave chopper to form any required bunch repetition rate between 1 MHz and 100 MHz. The results of initial optimizations of the beam dynamics with the focus on extracting and preserving ultra-low emittance will be presented.


*K.-J. Kim, Y. Shvyd'ko, and S. Reiche, to be published in Physical Review Letters (2008)
**K. Togawa, et al., Phys. Rev. STAB 10, 020703 (2007)