Details

Autor(en) / Beteiligte

• Sakakibara, Noritaka
• Muneoka, Hitoshi
• Urabe, Keiichiro
• Yasui, Ryoma
• Sakai, Osamu
• Terashima, Kazuo

Titel

Laser diagnostics on atmospheric pressure discharge plasmas, including cryoplasmas, in environments around room and cryogenic temperature

Ist Teil von

• Journal of physics. D, Applied physics, 2017-03, Vol.50 (16), p.165201

Ort / Verlag

IOP Publishing

Erscheinungsjahr

2017

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Cryoplasmas, the plasma gas temperature (Tg) of which can be controlled continuously below room temperature, show various unique and advantageous properties depending on Tg. Recently, the Tg dependence of plasma chemistry related to metastable helium (Hem) has been revealed in helium cryoplasmas. However, Tg was only estimated by thermal calculation from the temperature outside the plasmas. In this study, for better evaluation of Tg, near-infrared laser heterodyne interferometry (NIR-LHI) measurements were conducted in atmospheric pressure helium pulsed discharge plasmas at around room and cryogenic ambient temperatures (Ta). The maximum difference between Tg and Ta was evaluated as 47 K at Ta  =  300 K with 282 mW power consumption. To further investigate the Tg dependence of plasma chemical reactions related to Hem, laser absorption spectroscopy (LAS) was performed on the same discharge plasmas to measure the Hem density and lifetime. The Hem lifetime was longer at lower Tg, i.e. the lifetime at Tg  =  145 K (9.6 µs) was seven times longer than that at Tg  =  386 K (1.4 µs). By comparing the results with the numerically simulated rates of Hem quenching reactions taking Tg into account, the mechanism of the Hem quenching reaction was revealed to vary with Tg even though the main quenching reaction was a three-body collision at all Tg. In this manner, the combination of NIR-LHI with LAS led directly to the Tg dependence of Hem quenching reactions.