Tomographic characterisation of gas-jet targets for laser wakefield acceleration

作者：Couperus J P^*; Koehler A; Wolterink T A W; Jochmann A; Zarini O; Bastiaens H M J; Boller K J; Irman A; Schramm U

来源：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment , 2016, 830: 504-509.

DOI：10.1016/j.nima.2016.02.099

• Laser wakefield acceleration
• LWFA
• Gas-jet analysis
• Interferometry
• Tomography

Laser wakefield acceleration (LWFA) has emerged as a promising concept for the next generation of high energy electron accelerators. The acceleration medium is provided by a target that creates a local welldefined gas-density profile inside a vacuum vessel. Target development and analysis of theresulting gas density profiles is an important aspect in the further development of LWFA. Gas jet targets are widely used in regimes where relatively high electron densities over short interaction lengths are required (up to several millimetres interaction length, plasma densities down to similar to 1018 cm(-3)). In this paper we report a precise characterisation of such gas jet targets by a laser interferometry technique. We show that phase shifts down to 4 mrad can be resolved. Tomographic phase reconstruction enables detection of non-axisymmetrical gas-density profiles which indicates defects in cylindrical nozzles, analysis of slit-nozzles and nozzles with an induced shock-wave density step. In a direct comparison between argon and helium jets we show that it cannot automatically be assumed, as is often done, that a nozzle measured with argon will provide the same gas density with helium.

• 出版日期2016-9-11