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A high-power, beam-based, coherently enhanced THz radiation source

A high-power, beam-based, coherently enhanced THz radiation source.

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A high-power, beam-based, coherently enhanced THz radiation source

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  1. A high-power, beam-based, coherently enhanced THz radiation source We propose a Smith-Purcell radiation device that can potentially generate high average power THz radiation with very high conversion efficiency. The source is based on a train of short electron bunches from an rf photoemission gun at an energy of a few MeV. Particle tracking simulation and analysis show that with a beam current of 1 mA, it is feasible to generate hundreds of Watts of narrow-band THz radiation at a repetition rate of 1 MHz. Yuelin Li, Yin-E Sun, and Kwang-Je Kim Accelerator Systems Division Argonne Accelerator Institute Argonne National Laboratory, Argonne, IL 60439

  2. Content • Power of THz imaging • Capability of current available source • Our Approach of THz generation • Coherence enhancement • Laser pulse train generation • E-beam generation and dynamics • Smith-Purcell radiation • Putting together • Challenges • Summary

  3. Current sources • Broadband, THz TDS, <650 mW • CW • Gunn diode/Back wave oscillators, <200 mW • THz-wave parametric oscillators, <100 mW • THz gas lasers, <180 mW • QCL, <100 mW • FEL, >20 W, but bulky ~mW, 8 min H. B. Liu et al, Proc. IEEE 95, 1515 (2007). Higher power is needed field application.

  4. The matter of coherence Radiation power from a electron bunch Coherent radiation Incoherent radiation dE/dw: electron radiation energy into per spectral frequency N: total number of electrons Coherence factor S(t): electron temporal distribution

  5. Coherence factor as a function of bunch length Short bunch is the key for high coherent factor! Y.Li and K.-J. Kim, Appl. Phys. Lett. 92, 014101 (2008).

  6. Degradation of coherence factors in electron bunches Energy from zero to 8 MeV (see later) The degradation is due to space charge force.

  7. Effect of the space charge force Q: total charge sz, sr: longi and trans beam sizes g: relativistic factor To solve the problem Higher beam energy, costly on $$$$ Less charge, costly on photons How about bunch train? Reduced space charge but preserved coherence factor.

  8. Preserve the coherence factor by bunch trains Coherence factor for a bunch train scoh: coherence factor for individual bunched tb: bunch spacing, to be set as 2p/w Nb: Number of bunches

  9. Preserve the coherence factor by bunch trains Same coherence factor but narrower band width Coherent factor as a function of frequency for 1-16 bunches

  10. Laser pulse train generation (Credit: Cialdi et al., Appl. Phys. 46, 4959 (2007)) Number of pulses= 2n, n is the number of birefringence crystals

  11. Electrons Laser Gun Rf photoinjector • Need high duty factor, kHz to MHz • Laser power of 100 W • Klystron power: 10 kW L/S band gun Klystron Laser

  12. Simulation for an rf gun: bunch coherent factor Coherence fator at harmonics

  13. Smith-Purcell radiation (Credit: Scott Berg, http://www.cap.bnl.gov/spexp/) Resonant wavelength Radiation power per electron Ng, lg: number of grating grooves and grating period. le: evanescent wavelength n: diffraction order S.J. Smith and E. M. Purcell, Phys. Rev. 92, 1069 (1953). P.M. van den Berg, J. Opt. Soc. Am. 63, 1588 (1973).

  14. Electrons Laser Gun Putting things together: radiation powers at 1 MHz, for 0.5 THz grating THz total radiation power as a function of the beam center-grating distance with a beam scraper height D in mm measured from the grating surface.

  15. Summary • We showed that with coherence enhancement, a beam based source delivering hundreds of watts of THz power is possible and may be made compact for field application tools. Can we make a THz source like this? http://www.tfot.info/news/1051/boeing-tests-avenger-solid-state-laser-weapon.html

  16. References • B. Ferguson and X.C. Zhang, Nature Materials 1, 26 (2002). • K. Kawase, J. Shikata, K. Imai, and H. Ito, Appl. Phys. Lett. 78, 2819 (2001). • See, for example, D. Abbott and X.-C Zhang, Proc. IEEE 95, 1509 (2007) and the references therein. • G.L. Carr, M.C. Martin, W.R. McKinney, K. Jordan, G.R. Neil, and G.P. Williams, Nature 420, 153 (2002). • S.V. Miginsky, N.A. Vinokurov, D.A. Kayran, B.A. Knyazev, E.I. Kolobanov, V.V. Kotenkov, V.V. Kubarev, G.N. Kulipanov, A.V. Kuzmin, A.S. Lakhtychkin, A.N. Matveenko, L.E. Medvedev, L.A. Mironenko, A.D. Oreshkov, V.K. Ovchar, V.M. Popik, T.V. Salikova, S.S. Serednyakov, A.N. Skrinsky, O.A. Shevchenko, M.A. Scheglov, Proc of 2007 Asian Patical Accelerator Conference, Indore, India. • J.S. Nodvick and D.S. Saxon, Phys. Rev. 96, 180 (1954). • Y.K. Batygin, Phys. Plasmas 8, 3103 (2001). • B.J. Siwick, J.R. Dwyer, R.E. Jordan, R.J.D. Miller, J. Appl. Phys. 92, 1643 (2002). • A.M. Michalik and J.E. Sipe, J. Appl. Phys. 99, 054908 (2006). • Y.Li and K.-J. Kim, Appl. Phys. Lett. 92, 014101 (2008). • S.E. Korbly, A.S. Kesar, J.R. Sirigiri, and R.J. Temkin, Phys. Rev. Lett. 94, 054803 (2005). • M. Arbel, A. Abramovich, A. L. Eichenbaum, A. Gover, H. Kleinman, Y. Pinhasi, and I. M. Yakover, Phys. Rev. Lett. 86, 2561 (2001), and references therein. • http://www.pulsar.nl/gpt. • http://tesla.desy.de/~lfroehli/astra/ • S.J. Smith and E. M. Purcell, Phys. Rev. 92, 1069 (1953). • P.M. van den Berg, J. Opt. Soc. Am. 63, 1588 (1973). • H.L. Andrews and C.A. Brau, Phys. Rev. ST AB 7, 070701 (2004). • M. Boscolo, M. Ferrario,I. Boscolo, F. Castelli, and S. Cialdi, Nucl. Instr. and Meth. Phys. Res. A 577(3), 409 (2007). • J.G. Neumann, P.G. O'Shea, D. Demske, W.S. Graves, B. Sheehy, H. Loos and G.L. Carr, Nucl. Instr. Meth. Phys. Res. A 507, 498 (2003). • B. Dromey, M. Zepf, M. Landreman, K. O'Keeffe, T. Robinson, and S. M. Hooker, Appl. Opt. 46, 5142 (2007). • D.H. Dowell, F.K. King, R.E. Kirby, J. F. Schmerge, and J.M. Smedley, Phys. Rev. ST-AB 9, 063502 (2006). • T. Srinivasan-Rao, I. Ben-Zvi, J. Smedley, X.J. Wang, M. Woodle, Proc. PAC 97, 2790 (1998). • F. Röser, J. Rothhard, B. Ortac, A. Liem, O. Schmidt, T. Schreiber, J. Limpert, and A. Tünnermann, Opt. Lett. 30, 2754 (2005). • P. Dupriez, C. Finot, A. Malinowski, J.K. Sahu, J. Nilsson, D.J. Richardson, K.G. Wilcox, H.D. Foreman, and A.C. Tropper, Opt. Express 14, 9611 (2006). • D.N. Papadopoulos, Y. Zaouter, M. Hanna, F. Druon, E. Mottay, E. Cormier, and P. Georges, Opt. Lett. 32, 2520 (2007) • D.H. Dowell, J.W. Lewellen, D. Nguyen, and R. Rimmer, Nucl. Instrum. Meth. Phys. Research A 557, 61 (2006). • A. Todd, Nucl. Instrum. Meth. Phys. Research A 557, 36 (2006). • M. Cornacchia, S. Di Mitri, and G. Penco, and A.A. Zholents, Phys. Rev. ST-AB 9, 120701 (2006), and reference therein.

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