A bremsstrahlung gamma-ray source based on stable ionization injection of electrons into a laser wakefield accelerator

Abstract Laser wakefield acceleration permits the generation of ultra-short, high-brightness relativistic electron beams on a millimeter scale. While those features are of interest for many applications, the source remains constraint by the poor stability of the electron injection process. Here we present results on injection and acceleration of electrons in pure nitrogen and argon. We observe stable, continuous ionization-induced injection of electrons into the wakefield for laser powers exceeding a threshold of 7 TW. The beam charge scales approximately with the laser energy and is limited by beam loading. For 40 TW laser pulses we measure a maximum charge of almost 1 nC per shot, originating mostly from electrons of less than 10 MeV energy. The relatively low energy, the high charge and its stability make this source well-suited for applications such as non-destructive testing. Hence, we demonstrate the production of energetic radiation via bremsstrahlung conversion at 1 Hz repetition rate. In accordance with Geant4 Monte-Carlo simulations, we measure a γ-ray source size of less than 100 μm for a 0.5 mm tantalum converter placed at 2 mm from the accelerator exit. Furthermore we present radiographs of image quality indicators.

[1]  K. Perez.  Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment , 2014 .

[2]  A. Dell'Acqua,et al.  Geant4 - A simulation toolkit , 2003 .

[3]  A Pak,et al.  Self-guided laser wakefield acceleration beyond 1 GeV using ionization-induced injection. , 2010, Physical review letters.

[4]  V Malka,et al.  High-resolution gamma-ray radiography produced by a laser-plasma driven electron source. , 2005, Physical review letters.

[5]  Kazuhisa Nakajima,et al.  Towards a table-top free-electron laser , 2008 .

[6]  Ferenc Krausz,et al.  Density-transition based electron injector for laser driven wakefield accelerators , 2010 .

[7]  P Krejcik,et al.  Ionization-induced electron trapping in ultrarelativistic plasma wakes. , 2007, Physical review letters.

[8]  A. E. Dangor,et al.  Monoenergetic beams of relativistic electrons from intense laser–plasma interactions , 2004, Nature.

[9]  H Schwoerer,et al.  Thomson-backscattered x rays from laser-accelerated electrons. , 2006, Physical review letters.

[10]  T. Tajima,et al.  Laser Electron Accelerator , 1979 .

[11]  Zulfikar Najmudin,et al.  Characterization of a gamma-ray source based on a laser-plasma accelerator with applications to radiography , 2002 .

[12]  Z. Najmudin,et al.  Characterization of transverse beam emittance of electrons from a laser-plasma wakefield accelerator in the bubble regime using betatron x-ray radiation , 2011, 1105.5559.

[13]  V Malka,et al.  Single shot phase contrast imaging using laser-produced Betatron x-ray beams. , 2011, Optics letters.

[14]  Y. Glinec,et al.  Controlled injection and acceleration of electrons in plasma wakefields by colliding laser pulses , 2006, Nature.

[15]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[16]  C. Bentley,et al.  Evaluation of the sensitivity and fading characteristics of an image plate system for x-ray diagnostics. , 2008, The Review of scientific instruments.

[17]  R. Sheu,et al.  A detailed study on the neutron contamination for a 10 MeV medical electron accelerator , 2006 .

[18]  S. Corde,et al.  Compact and high-quality gamma-ray source applied to 10 μm-range resolution radiography , 2011 .

[19]  W. Coolidge.  A Powerful Röntgen Ray Tube with a Pure Electron Discharge , 1913 .

[20]  J. Cary,et al.  Plasma-density-gradient injection of low absolute-momentum-spread electron bunches. , 2008, Physical review letters.

[21]  Eric Esarey,et al.  Theory of ionization-induced trapping in laser-plasma accelerators , 2012 .

[22]  Rajiv C. Shah,et al.  All-optical Compton gamma-ray source , 2012, Nature Photonics.

[23]  J. Cary,et al.  High-quality electron beams from a laser wakefield accelerator using plasma-channel guiding , 2004, Nature.

[24]  Eric Esarey,et al.  Trapping and acceleration in nonlinear plasma waves , 1995 .

[25]  R. Sigel,et al.  Polarized light interferometer for laser fusion studies. , 1979, The Review of scientific instruments.

[26]  I. V. Glazyrin,et al.  Ionization induced trapping in a laser wakefield accelerator. , 2009, Physical review letters.

[27]  G. Felici,et al.  Radiation protection measurements around a 12 MeV mobile dedicated IORT accelerator. , 2010, Medical physics.

[28]  Antoine Rousse,et al.  Production of a keV x-ray beam from synchrotron radiation in relativistic laser-plasma interaction. , 2004, Physical review letters.

[29]  Eric Esarey,et al.  Physics of laser-driven plasma-based electron accelerators , 2009 .

[30]  Eric Esarey,et al.  Low-emittance electron bunches from a laser-plasma accelerator measured using single-shot x-ray spectroscopy. , 2012 .

[31]  Y. Glinec,et al.  A laser–plasma accelerator producing monoenergetic electron beams , 2004, Nature.

[32]  V. Krainov,et al.  Tunneling and barrier-suppression ionization of atoms and ions in a laser radiation field , 1998 .

[33]  V. Malka,et al.  Laser-driven accelerators by colliding pulses injection: A review of simulation and experimental results , 2009 .

[34]  Victor Malka,et al.  Physics of fully-loaded laser-plasma accelerators , 2015 .

[35]  Erik Lefebvre,et al.  Few femtosecond, few kiloampere electron bunch produced by a laser-plasma accelerator , 2011 .

[36]  Zulfikar Najmudin,et al.  Bright spatially coherent synchrotron X-rays from a table-top source , 2010 .

[37]  R. Lillie,et al.  TRANSMISSION OF PHYSIOLOGICAL INFLUENCE IN PROTOPLASMIC SYSTEMS, ESPECIALLY NERVE , 1922 .

[38]  V Malka,et al.  Observation of longitudinal and transverse self-injections in laser-plasma accelerators , 2013, Nature Communications.

[39]  Miss A.O. Penney.  (b) , 1974, The New Yale Book of Quotations.