title: Note: femtosecond laser micromachining of straight and linearly tapered capillary discharge waveguides.
abstract: Gas-filled capillary discharge waveguides are important structures in laser-plasma interaction applications, such as the laser wakefield accelerator. We present the methodology for applying femtosecond laser micromachining in the production of capillary channels (typically 200-300 μm in diameter and 30-40 mm in length), including the formalism for capillaries with a linearly tapered diameter. The latter is demonstrated to possess a smooth variation in diameter along the length of the capillary (tunable with the micromachining trajectories). This would lead to a longitudinal plasma density gradient in the waveguide that may dramatically improve the laser-plasma interaction efficiency in applications.
authors.affiliation: Scottish Universities Physics Alliance, Department of Physics, University of Strathclyde, Glasgow G4 0NG, United Kingdom. mark.wiggins@strath.ac.uk
authors.forename: S M
authors.initials: SM
authors.lastname: Wiggins
authors.forename: M P
authors.initials: MP
authors.lastname: Reijnders
authors.forename: S
authors.initials: S
authors.lastname: Abuazoum
authors.forename: K
authors.initials: K
authors.lastname: Hart
authors.forename: G H
authors.initials: GH
authors.lastname: Welsh
authors.forename: R C
authors.initials: RC
authors.lastname: Issac
authors.forename: D R
authors.initials: DR
authors.lastname: Jones
authors.forename: D A
authors.initials: DA
authors.lastname: Jaroszynski