Efficient generation of extended plasma waveguides with the axicon ignitor-heater scheme

Abstract

An efficient method for generating extended plasma waveguides is developed by using the axicon lens in conjunction with the ignitor-heater scheme. The short-pulse ignitor generates the seed electrons by multiphoton ionization, and the long-pulse heater expands the plasma by inverse bremsstrahlung heating and builds up the plasma density barrier by collisional ionization. A 1.2-cm-long plasma waveguide is generated in pure Ar gas with a total energy of only 100 mJ. Evolution of the plasma density profile is measured by time-resolved interferometry to show the waveguide forming process and how it can be optimized.

Plasma expansion into a waveguide created by a linearly polarized femtosecond laser pulse

“…Preformed plasma waveguides have been achieved by ionizing and heating a linear region of gas, either by using high-voltage discharges [18][19][20]23 or by using long laser pulses ($10-100 ps) with linear focusing optics such as axicons focused in gas jets. 16,17,24 The initial plasma heating generates a hydrodynamic expansion wave leading to density depletion in the center of the plasma column forming the plasma channel. These methods have been used to create guiding structures in the centimeter range and open the path to laser-plasma multi-GeV electron accelerators, with current laser technology.…”

Dramatic Enhancement of Optical-Field-Ionization Collisional-Excitation X-Ray Lasing by an Optically Preformed Plasma Waveguide

“…In this Letter, we report demonstration of optical-field-ionization collisional-excitation x-ray lasers in an optically preformed plasma waveguide. By using the axicon-ignitor-heater scheme [17] to produce a 9-mm-long plasma waveguide of pure krypton gas, enhancement of Ni-like krypton x-ray lasing at 32.8 nm by a factor of 400 is observed compared to that without the plasma waveguide, resulting in a photon number of 8 10 10 and an energy conversion efficiency of 2 10 ÿ6 with a pump pulse of only 235 mJ energy. In addition, taking advantage of the high atom density and large gain length provided by such a plasma waveguide, optical-fieldionization collisional-excitation x-ray lasing for the highthreshold low-gain transition at 46.9 nm in neonlike argon is also demonstrated.…”

“…Among all the guiding methods reported, optically preformed plasma waveguide in a gas jet [15][16][17] is most favorable because it allows (1) guiding of the pump pulse and the lasing x-ray pulse simultaneously, (2) characterization of the underlying process through various diagnostics such as interferometry, and (3) damage-free long-term high-repetition-rate operation for practical applications. Discovering methods to apply an optically preformed plasma waveguide to x-ray lasers has been an ongoing effort since 1995 [18].…”

Laser guiding for GeV laser–plasma accelerators

“…Much higher net energy gains can be realized for the same amount of input laser power by extending the acceleration distance beyond Z R . Guiding concepts relying on the use of preformed channels are being studied by several groups around the world (Volfbeyn et al 1999;Geddes et al 2004a;Alexeev et al 2003;Downer et al 2003;Tochitsky et al 2004;Sprangle et al 2001;Spence & Hooker 2001;Zhidkov et al 2004;Lopes et al 2003;Chen et al 2004;Cros et al 2002). At LBNL, using the ignitor-heater concept (Volfbeyn et al 1999), we have recently produced plasma channels that have guided, to our knowledge, the highest peak power and the highest intensity in a preformed channel (Geddes et al 2004a).…”