03 Linear Colliders, Lepton Accelerators and New Acceleration Techniques

A20 Plasma Wakefield Acceleration

Paper Title Page
THPEC001 Optimization of Nonlinear Wakefield Amplitude in Laser Plasma Interaction 4056
 
  • A.K. Upadhyay, P. Jha
    Lucknow University, Lucknow
  • S. Krishnagopal
    BARC, Mumbai
  • S.A. Samant, D. Sarkar
    CBS, Mumbai
 
 

Nonlinear, high-amplitude plasma waves are excited in the wake of an intense laser pulse propagating in a cold plasma, providing acceleration gradients up to GeV/m. Linear analytic analyses have shown that the wakefield amplitude is optimal for a certain ratio of the pulse length and plasma wavelength*,**. Here we present results of simulation studies to optimize the nonlinear wakefield amplitudes. Variation in the laser pulse length is considered for maximizing amplitudes of wakefields generated by half-sine and Gaussian pulse profiles. Further, the advantages of using a transversely inhomogeneous plasma for the generation of the nonlinear wakefields are studied and compared with the homogeneous case.


* E. Esarey, P. Sprengle, J. Krall and A. Ting, IEEE Trans. Palsma Sci. 24, 252 (1996)
** L. M. Gorbunov and V. I. Kirsanov, Zh. Eksp. Teor. Fiz. 93, 509 (1987), Sov. Phys. JETP, 46, 290 (1988).

 
THPEC002 Simulation of Electron Acceleration by Two Laser Pulses Propagating in a Homogenous Plasma 4059
 
  • S. Krishnagopal
    BARC, Mumbai
  • P. Jha, A.K. Upadhyay
    Lucknow University, Lucknow
  • S.A. Samant, D. Sarkar
    CBS, Mumbai
 
 

We study electron acceleration by two laser pulses co-propagating one behind the other in a homogeneous plasma. We show, using one-dimensional simulations, that the wake amplitude can be amplified or diminished depending on the time delay between the two lasers, in agreement with linear analytic theory. We extend the study to the bubble regime using two-dimensional simulations. We find that the one-dimensional optimization holds in two dimensions also. Trapping and acceleration of quasi-monoenergetic electrons (up to around 300 MeV) is found in the bucket behind the second laser, even for low intensities, where there is no trapping with a single laser. Thus, this scheme could be very useful for achieving a desired accelerated energy with less intense lasers, or, equivalently, increasing the accelerated energy for a given laser intensity.


* G. Raj, A. K. Upadhyay, R. K. Mishra and P. Jha, Phys. Rev. ST Accel. and Beams 11, 071301 (2008).

 
THPEC003 Stabilization of Laser Accelerated Electron Bunch by the Ionization-stage Control 4062
 
  • M. Mori, S.V. Bulanov, Y. Hayashi, K. Kawase, K. Kondo, A.S. Pirozhkov, A. Sugiyama
    JAEA, Ibaraki-ken
  • M. Kando
    JAEA APRC, Ibaraki-ken
  • H. Kotaki, K. Ogura
    JAEA/Kansai, Kyoto
  • H. Nishimura
    ILE Osaka, Suita
 
 

The pointing stability and the divergence of a quasi-monoenergetic electron bunch generated in a self-injected laser-plasma acceleration regime were investigated. Gas-jet targets have been irradiated with focused 40 fs laser pulses at the 4-TW peak power. A pointing stability of 2.4 mrad root-mean-square (RMS) and a beam divergence of 10.6 mrad (RMS) were obtained using argon gas-jet target for 50 sequential shots, while these values were about three times smaller than at the optimum condition using helium. In particular, the peak electron energy was 9 MeV using argon, which is almost three times lower than that using helium. This result implies that the formation of the wake-field is different between argon and helium, and it plays an important role in the generation of a electron bunch. This stabilization scheme is available for another gas material such as nitrogen. At nitrogen gas-jet target, the pointing stability is more improved to 1.4 times smaller (1.7 mrad (RMS)) than that in argon gas-jet target and the peak energy is increased to grater than 40 MeV. These results prove that this method not only stabilize the e-beam but also allows controlling the electron energy.

 
THPEC004 All-optical Hard X-ray Sources and their Application to Nuclear Engineering 4065
 
  • K. Koyama
    University of Tokyo, Tokyo
  • A. Maekawa, H. Masuda, M. Uesaka
    The University of Tokyo, Nuclear Professional School, Ibaraki-ken
  • Y. Oishi
    Central Research Institute of Electric Power Industry, Yokosuka-shi, Kanagawa
 
 

We are studying the artificial injection of initial electrons into the wakefield for producing stable electron bunch (the charge is 100 pC, the energy stability is better than a few per cent). The objective of our research is to produce 100-keV class monochromatic X-ray pulses for measuring concentrations of nuclear materials in a reprocessing plant. A K-edge densitometry using monochromatic hard x-ray beams is one of the effective technique to measure concentrations of nuclear materials in a reprocessing solutions. An inverse Compton scattering process between an IR-laser beam of 800 nm and high-energy electron bunch of above 80 MeV makes it possible to deliver tunable monochromatic x-rays near K-absorption edges of nuclear materials of 115-129 keV. In order to use in a reprocessing plant, the equipment for the K-edge densitometry must be smaller than a compact car. The only solution to realize the compact system is to use a laser wakefield accelerator instead of a radio frequency linac. An ultra-short ten-TW laser pulse focused on a supersonic jet makes it possible to accelerate electrons up to 100 MeV in a plasma length of 2.5 mm.

 
THPEC007 Density Structure Effect on the Electron Energy in Laser Wakefield Accelerator 4068
 
  • J. Kim, G. Kim, J. Kim, S.H. Yoo
    KERI, Changwon
 
 

Using the nonlinear interaction between the high power laser and the plasma, we can generate strong acceleration field, called the laser wake field acceleration. The plasma density is very crucial to generate high energy electron. In this work, we studied the effect of the plasma density structure on the accelerated electron energy. We used 20 TW, 40 fs laser system to generate the plasma wakefield. A gas jet was used as a target. The plasma density was controlled by the back pressure of the gas nozzle and measured by the interferometer. The accelerated electron energy was measured using the electron energy spectrometer with 0.5 T magnet. The bunch charge was measured integrated charge transformer (ICT). When the plasma density is uniform, 2×1019 cm-3 we can generate 200 MeV electron beam with bunch charge 33 pC. The electron beam divergence was less than 5 degree. If there exists the downward density tramp, the electron energy is only 50 MeV. The PIC simulation also indicates that if there is density ramp structure, the electron is not accelerated well. In this presentation, the overall experimental and simulation results are presented.

 
THPEC009 A Gas-filled Capillary Plasma Source for Laser-driven Plasma Acceleration 4071
 
  • H. Suk, D. Jang, D. Jang, M. Kim, S. Oh
    APRI-GIST, Gwangju
 
 

In recent years, the laser-driven plasma wakefield acceleration has attracted much attention as it has a much higher acceleration gradient (>100 GeV/m) compared with the RF-based conventional accelerators. In the past, the supersonic gas jet method for plasma wakefield acceleration was widely used, but this method has a limitation in acceleration distance and energy because the focused laser beam is diffracted severely over a very short distance (~ a few mm range). To avoid the diffraction problem, a capillary plasma source can be used, where a high power laser beam can be guided over a long distance (~ a few cm range) by a parabolic plasma density profile in the capillary plasma channel. We have developed a gas-filled capillary plasma source for generation of GeV-level electron beams in collaboration with the University of Oxford team. In this presentation, the detailed test results and the near-future experimental plan for GeV-level e-beam generation are shown.

 
THPEC011 Electron Acceleration Experiments Using the Hercules Laser System at the University of Michigan 4074
 
  • K.M. Krushelnick, V. Chvykov, F.J. Dollar, G. Kalintchenko, A. Maksimchuk, T. Matsuoka, C.S. McGuffey, W. Schumaker, A.G.R. Thomas, V. Yanovsky
    University of Michigan, FOCUS Center for Ultrafast Optical Science, Ann Arbor, Michigan
 
 

Recent experimental results will be discussed with regard to the use of the 300 TW, 30 fsec HERCULES laser system at the Center for Ultrafast Optical Science at Michigan to generate GeV range electron beams using Laser Wakefield Acceleration (LWFA). The electron beam quality is shown to be improved substantially using gas mixtures- causing an increase in beam charge and a decrease in emittance. The dynamics of the acceleration process are also determined by measurements of spatially resolved scattered laser radiation and the use of femtosecond optical probing techniques.

 
THPEC015 Breaking the Attosecond, Angstrom and TV/m Field Barriers with Ultra-fast Electron Beams 4080
 
  • J.B. Rosenzweig, G. Andonian, A. Fukasawa, E. Hemsing, G. Marcus, A. Marinelli, P. Musumeci, B.D. O'Shea, F.H. O'Shea, C. Pellegrini, D. Schiller, G. Travish
    UCLA, Los Angeles, California
  • P.H. Bucksbaum, M.J. Hogan, P. Krejcik
    SLAC, Menlo Park, California
  • M. Ferrario
    INFN/LNF, Frascati (Roma)
  • S.J. Full
    Penn State University, University Park, Pennsylvania
  • P. Muggli
    USC, Los Angeles, California
 
 

Recent initiatives at UCLA concerning ultra-short, GeV electron beam generation have been aimed at achieving sub-fs pulses capable of driving X-ray free-electron lasers (FELs) in single-spike mode. This uses of very low charge beams, which may allow existing FEL injectors to produce few-100 attosecond pulses, with very high brightness. Towards this end, recent experiments at the Stanford X-ray FEL (LCLS, first of its kind, built with essential UCLA leadership) have produced ~2 fs, 20 pC electron pulses. We discuss here extensions of this work, in which we seek to exploit the beam brightness in FELs, in tandem with new developments at UCLA in cryogenic undulator technology, to create compact accelerator/undulator systems that can lase below 0.15 Angstroms, or be used to permit 1.5 Angstrom operation at 4.5 GeV. In addition, we are now developing experiments which use the present LCLS fs pulses to excite plasma wakefields exceeding 1 TV/m, permitting a table-top TeV accelerator for frontier high energy physics applications.

 
FRXCMH02 Plasma Accelerators for Future Colliders
 
  • C. Joshi
    UCLA, Los Angeles, California
 
 

Recent experiments on beam-driven Plasma Wakefield Acceleration has shown spectacular results- that 42 GeV electrons can be made to double their energy in less than one meter using collective fields in a plasma. Simulations have shown that it is possible to not only obtain high energy gains but also to have small energy spread and emittances needed for a future collider application from such a device. Furthermore the overall energy extraction efficiency from the drive beam to the accelerating beam can be made to be very high. It is the purpose of the FACET facility now under construction at SLAC to address these critical issues in the next five years. Based on the luminosity requirements of high energy physicists for a 1 TeV CM electron-positron collider, a strawman design study of a plasma wakefield accelerator linear collider (PWFA-LC) has been carried out. This talk will review the the results obtained to-date, the proposed upcoming program on FACET and discuss the roadmap for a PWFA-LC.


Work done in collaboration with colleagues from SLAC experiments E157,162,164 and 167.

 

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