title: Note: Real-time monitoring via second-harmonic interferometry of a flow gas cell for laser wakefield acceleration.
abstract: The use of a gas cell as a target for laser wakefield acceleration (LWFA) offers the possibility to obtain stable and manageable laser-plasma interaction process, a mandatory condition for practical applications of this emerging technique, especially in multi-stage accelerators. In order to obtain full control of the gas particle number density in the interaction region, thus allowing for a long term stable and manageable LWFA, real-time monitoring is necessary. In fact, the ideal gas law cannot be used to estimate the particle density inside the flow cell based on the preset backing pressure and the room temperature because the gas flow depends on several factors like tubing, regulators, and valves in the gas supply system, as well as vacuum chamber volume and vacuum pump speed/throughput. Here, second-harmonic interferometry is applied to measure the particle number density inside a flow gas cell designed for LWFA. The results demonstrate that real-time monitoring is achieved and that using low backing pressure gas (<1 bar) and different cell orifice diameters (<2 mm) it is possible to finely tune the number density up to the 10(19) cm(-3) range well suited for LWFA.
authors: Intense Laser Irradiation Laboratory (ILIL), Istituto Nazionale di Ottica (INO-CNR), Via Moruzzi 1, 56124 Pisa, Italy.
authors: F
authors: F
authors: Brandi
authors: Dipartimento di Fisica, Università degli Studi di Pisa, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
authors: F
authors: F
authors: Giammanco
authors: Dipartimento di Fisica, Università degli Studi di Pisa, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
authors: F
authors: F
authors: Conti
authors: SourceLAB SAS, 86 Rue de Paris, 91400 Orsay, France.
authors: F
authors: F
authors: Sylla
authors: LOA, ENSTA ParisTech, CNRS, Ecole Polytechnique, Université Paris-Saclay, 828 bd des Maréchaux, 91762 Palaiseau Cedex, France.
authors: G
authors: G
authors: Lambert
authors: Intense Laser Irradiation Laboratory (ILIL), Istituto Nazionale di Ottica (INO-CNR), Via Moruzzi 1, 56124 Pisa, Italy.
authors: L A
authors: LA
authors: Gizzi