Scientific Results

Optical and spectroscopic study of a
supersonic flowing helium plasma:
energy transport in the afterglow

Year: 2020

Authors: Brandi F., L. Labate, D. Rapagnani, R. Buompane, A. di Leva, L. Gialanella,
L. A. Gizzi

Autors Affiliation: Intense Laser Irradiation Laboratory (ILIL), Istituto Nazionale di Ottica – Consiglio Nazionale delle Ricerche (INO-
CNR), Sede Secondaria di Pisa, Via Moruzzi, 1, 56124, Pisa, Italy.

Istituto Nazionale di Fisica Nucleare (INFN),
Sezione di Pisa, Largo Bruno Pontecorvo, 3, 56127, Pisa, Italy.

Dipartimento di Fisica e Geologia, Universitá
degli Studi di Perugia, via A.Pascoli, 06123, Perugia, Italy.

INFN sezione di Perugia, via A.Pascoli, 06123, Perugia,

Dipartimento di Matematica e Fisica, Universitá della Campania ”L. Vanvitelli”, Viale Lincoln, 5, Caserta,

Dipartimento di Fisica ”E. Pancini”, Universitá di Napoli ”Federico II”, Via Cinthia snc, Napoli, Italy. 7 Istituto
Nazionale di Fisica Nucleare, Sezione di Napoli, Via Cinthia snc, Napoli, Italy.

Abstract: Flowing plasma jets are increasingly investigated and used for surface treatments, including biological
matter, and as soft ionization sources for mass spectrometry. They have the characteristic capability to
transport energy from the plasma excitation region to the flowing afterglow, and therefore to a distant
application surface, in a controlled manner. The ability to transport and deposit energy into a specimen
is related to the actual energy transport mechanism. In case of a flowing helium plasma, the energy in
the flowing afterglow may be carried by metastable helium atoms and long-lived helium dimer ions.
In this work a systematic investigation of the optical and spectroscopic characteristics of a supersonic
flowing helium plasma in vacuum and its afterglow as function of the helium gas density is presented.
The experimental data are compared with numerical modeling of the plasma excitation and helium
dimer ion formation supported by a Computational Fluid Dynamic simulation of the helium jet. The
results indicate that the plasma afterglow is effectively due to helium dimer ions recombination via a
three-body reaction.


Volume: 10      Pages from: 5087  to: 5097

KeyWords: plasma diagnostics, spectroscopy, plasma afterglow