STRONG DISCHARGE PROCESSES BY ATMOSPHERIC PLASMA JET A AY WITHOUT EXTERNAL GROUND ELECTRODE

Abstract

We previously reported an intense plasma emission formed by plasma jet-to-jet coupling from various circular array configurations at atmospheric pressure 1,2 . To achieve an intense plasma emission using plasma jet-to-jet coupling, the plasma array device required a single electrode configuration and external ground electrode located several centimeters apart from the array 1 . In spite of an intense plasma plume with a lot of reactive radicals in ambient air, the requirement of precise adjustment of the discharge distance between the plasma array and the counter electrode would be a drawback of the plasma jet array for various surface treatments at atmospheric pressure. To generate an intense plasma plume with a good stability regardless of the discharge distance, we now propose two different plasma array structures to eliminate a counter ground electrode.The first plasma array device consists of a central glass tube encircled by an array of hollow glass tubes with side openings. The device configuration forces the individual plasma jets emanating from the side openings of the outer tubes to merge with the central plasma plume. As a result, a high intensity plasma emission is stably produced from the plasma jet-to-jet coupling of the ten glass tubes regardless of the distance between the plasma array and the external ground electrode, thereby eliminating the need for an external ground electrode. The second proposed plasma array structure consisting of two plasma jet arrays with an appropriate angle and a double electrode configuration is used as an ambient plasma source. Since these proposed plasma devices are able to generate an intense plasma emission without external ground electrode, they are promising tools for surface treatments and modifications that require a strong discharge process such as an ambient ionization mass spectrometry, regardless of the dielectric property of the target material.