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Yakimenko, V.

Paper Title Page
MOPAS103 Optical Parametric Amplifier Test for Optical Stochastic Cooling of RHIC 667
 
  • I. Pavlishin, M. Babzien, I. Pogorelsky, D. Stolyarov, V. Yakimenko
    BNL, Upton, Long Island, New York
  • M. S. Zolotorev
    LBNL, Berkeley, California
 
  Funding: Work supported by US Department of Energy contract DE-AC02-98CH10886

Optical stochastic cooling for the Relativistic Heavy Ion Collider (RHIC) based on optical parametric amplification was proposed by M. Babzien et al., Phys. Rev. ST Accel. Beams v.7, 012801, (2004). According to this proposal a CdGeAs2 nonlinear crystal is used as an active medium for the optical parametric amplifier because of extremely large nonlinear coefficient, wide transparency range, and possibility to be phase matched over the required spectral range. We discuss experimental results of the parametric amplifier gain and coherency for the conditions applicable to optical stochastic cooling for RHIC.

 
TUOBAB02 Experimental Characterization of the Transverse Phase Space of a 60-MeV Electron Beam through a Compressor Chicane 788
 
  • F. Zhou, A. C. Kabel
    SLAC, Menlo Park, California
  • R. B. Agustsson, G. Andonian, D. B. Cline, A. Y. Murokh, J. B. Rosenzweig
    UCLA, Los Angeles, California
  • V. Yakimenko
    BNL, Upton, Long Island, New York
 
  Funding: U. S. DOE of Sciences

Space charge and coherent synchrotron radiation may deteriorate electron beam quality when the beam passes through a magnetic bunch compressor. This paper presents the transverse phase-space tomographic measurements for a compressed beam at 60 MeV, around which energy the first stage of magnetic bunch compression takes place in most advanced linacs. Transverse phase-space bifurcation of a compressed beam is observed at that energy, but the degree of the space charge-induced bifurcation is appreciably lower than the one observed at 12 MeV. The Trafic4 simulation confirms the observation.

The paper was published at PRST-AB, November 2006

 
slides icon Slides  
TUPMS034 Seeded VISA: A 1064 nm Laser-Seeded FEL Amplifier at the BNL ATF 1257
 
  • M. P. Dunning, G. Andonian, E. Hemsing, S. Reiche, J. B. Rosenzweig
    UCLA, Los Angeles, California
  • M. Babzien, V. Yakimenko
    BNL, Upton, Long Island, New York
 
  An experimental study of a seeded free electron laser (FEL) using the VISA undulator and a Nd:YAG seed laser will be performed at the Accelerator Test Facility at Brookhaven National Laboratory. The study is motivated by the demand for a short Rayleigh length FEL amplifier at 1 micron for high power transmission with minimal damage of transport optics. Planned measurements include transverse and longitudinal coherence, angular distribution, and wavelength spectrum of the FEL radiation. The effects of detuning the electron beam energy will be studied, with an emphasis on control of the radiation emission angles and increase of the amplifier efficiency. Results of start-to-end simulations will be presented with preliminary experimental results.  
TUPMS036 Characterization of Orbital Angular Momentum Modes in FEL Radiation 1263
 
  • E. Hemsing, G. Andonian, J. B. Rosenzweig
    UCLA, Los Angeles, California
  • M. Babzien, V. Yakimenko
    BNL, Upton, Long Island, New York
  • A. Gover
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv
 
  Optical guiding of the radiation pulse through the source electron bunch in a free-electron laser is a well known phenomena that suppresses diffraction of the output radiation, and thus enhances the gain. The resulting radiation can be described by an expansion of orthogonal modes that are also composed of eigenstates of orbital angular momentum (OAM). In the VISA-FEL experiment at the ATF-BNL, gain guiding has been observed under self-amplified spontaneous emission conditions at 840 nm with a strongly chirped input electron beam. The resulting far-field transverse radiation profiles are observed to contain multiple modes in the angular intensity spectrum, and exhibit both hollow and spiral structures characteristic of single or multiply interfering OAM modes. Current efforts to characterize the transverse radiation profile both experimentally and through start-to-end simulations are presented.  
THPMS031 Plasma Wakefield Acceleration Utilizing Multiple Electron Bunches 3070
 
  • E. Kallos, T. C. Katsouleas, P. Muggli
    USC, Los Angeles, California
  • W. D. Kimura
    STI, Washington
  • I. Pavlishin, I. Pogorelsky, D. Stolyarov, V. Yakimenko
    BNL, Upton, Long Island, New York
 
  Funding: DoE contract # DE-FG02-92-ER40745

We investigate various plasma wakefield accelerator schemes that rely on multiple electron bunches to drive a large amplitude plasma wave, which are followed by a witness bunch at a phase where it will sample the high acceleration gradient and gain energy. Experimental verifications of various two bunch schemes are available in the literature; here we provide analytical calculations and numerical simulations of the wakefield dependency and the transformer ratio when M drive bunches and one witness bunch are fed into a high density plasma, where M is between 2 and 10. This is a favorable setup since the bunches can be adjusted such that the transformer ratio and the efficiency of the accelerator are enhanced compared to single bunch schemes. The possibility of a five bunch ILC afterburner to accelerate a witness bunch from 100 GeV to 500 GeV is also examined.

 
THPMS032 Plasma Wakefield Acceleration Experiments using Two Subpicosecond Electron Bunches 3073
 
  • P. Muggli, E. Kallos, T. C. Katsouleas
    USC, Los Angeles, California
  • W. D. Kimura
    STI, Washington
  • K. Kusche, I. Pavlishin, D. Stolyarov, V. Yakimenko
    BNL, Upton, Long Island, New York
 
  Funding: This work is supported by US DoE under contracts DE-FG02-92-ER40745 and DE-FG02-04ER41294.

Two ~100 fs electron bunches, separated in energy by approximately 1.8 MeV and in time by 0.5-1 ps, were sent through a capillary discharge plasma. The plasma density was varied from ~1·1014/cc to ~1·1017/cc. A 2-D PWFA model indicates the net wakefield produced by the bunches will depend on their relative charge, temporal separation, and the plasma density. This will affect the amount of energy gain or loss of the second bunch. During measurements of the energy spectrum of the second bunch, we observed a difference in the amount of gain or loss depending on the plasma density, which is consistent with the model prediction.

 
THPMS034 Generation and Characterization of the Microbunched Beams with a Wire Mesh Target 3079
 
  • P. Muggli, E. Kallos
    USC, Los Angeles, California
  • M. Babzien, K. Kusche, V. Yakimenko
    BNL, Upton, Long Island, New York
  • W. D. Kimura
    STI, Washington
 
  Funding: Work supported by US Department of Energy contract DE-AC02-98CH10886

The presentation will cover experimental results on generation and measurement of the beams with theμbunches length from 1 to 50 microns at Brookhaven Accelerator Test Facility. Arbitrary number of microbunches is sliced out of 5 ps long beam using wire mesh and slits. The details of beam structure are characterized using CSR interferometer and 6 mm long plasma wakefield channel with the controllable plasma density.

 
TUPMS033 Chicane Radiation Measurements with a Compressed Electron Beam at the BNL ATF 1254
 
  • G. Andonian, R. B. Agustsson, A. M. Cook, M. P. Dunning, E. Hemsing, A. Y. Murokh, S. Reiche, J. B. Rosenzweig
    UCLA, Los Angeles, California
  • M. Babzien, K. Kusche, R. Malone, V. Yakimenko
    BNL, Upton, Long Island, New York
 
  The radiation emitted from a chicane compressor has been studied at the Brookhaven National Laboratory (BNL) Accelerator Test Facility (ATF). Coherent edge radiation (CER)is emitted from a compressed electron beam as it traverses sharp edge regions of a magnet. The compression is accompanied by strong self-fields, which are manifested as distortions in the momentum space called beam bifurcation. Recent measurements indicate that the bunch length is approximately 100 fs rms. The emitted THz chicane radiation displays strong signatures of CER. This paper reports on the experimental characterization and subsequent analysis of the chicane radiation measurements at the BNL ATF with a discussion of diagnostics development and implementation. The characterization includes spectral analysis, far-field intensity distribution, and polarization effects. Experimental data is benchmarked to a custom developed start-to-end simulation suite.  
THPMS095 Experimental Demonstration of Feasibility of a Polarized Gamma-source for ILC Based on Compton Backscattering Inside a CO2 Laser Cavity 3208
 
  • I. Pogorelsky, V. Yakimenko
    BNL, Upton, Long Island, New York
 
  Funding: Work supported by US Department of Energy contract DE-AC02-98CH10886

Compton interaction point incorporated into a high-average-power laser cavity is the key element of the Polarized Positron Source (PPS) concept proposed for ILC [1]. According to this proposal, circularly polarized gamma rays are produced in Compton backscattering from a 6 GeV linac e-beam inside a CO2 laser amplifier cavity. Intra-cavity positioning of the interaction point allows multiple laser recycling to match the electron bunch train format. We conducted experimental tests of multi-pulse operation of such active Compton cavity upon injection of a picosecond CO2 laser beam. Together with earlier demonstration of a high x-ray yield via the e-beam/CO2-laser backscattering, these new results show a viability of the entire PPS concept and closely prototype the laser source requirements for ILC.

[1] V. Yakimenko and I. V. Pogorelsky, Phys. Rev. ST Accel. Beams 9, 091001 (2006)

 
FRPMS059 Generation and Analysis of Subpicosecond Double Electron Bunch at the Brookhaven Accelerator Test Facility 4132
 
  • X. P. Ding, D. B. Cline
    UCLA, Los Angeles, California
  • M. Babzien, K. Kusche, V. Yakimenko
    BNL, Upton, Long Island, New York
  • W. D. Kimura
    STI, Washington
  • F. Zhou
    SLAC, Menlo Park, California
 
  Funding: U. S.DOE of Science

Two compressed electron beam bunches from a single 60-MeV bunch have been generated in a reproducible manner during compression in the magnetic chicane - "dog leg" arrangement at ATF. Measurements indicate they have comparable bunch lengths (~100-200 fs) and are separated in energy by ~1.8 MeV with the higher-energy bunch preceding the lower-energy bunch by 0.5-1 ps. Some simulation results for analyzing the double-bunch formation process are also presented.