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Title: Studies of plasma processes within argon glow discharges by fast flowing glow discharge mass spectrometry
Author: Mortimer, I. P.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2000
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This thesis describes investigations of ionisation processes within analytical argon flow discharges. These were conducted using a novel fast flowing glow discharge ion source previously developed within this laboratory. This consists of a short flow tube with a co-axial cathode glow discharge cell at one end and the ion exit at the other. Investigation of a variety of source parameters showed behaviour inconsistent with ionisation being solely due to Penning ionisation or direct ionisation processes (as is conventionally assumed). This indicates that other previously unconsidered ion-formation pathways also occur within the argon plasma. Various gases were injected into the region of the plasma close to the ion exit. In most cases, the intrinsic plasma ions were replaced by ions originating from the secondary gas. However, when small proportions of hydrogen were added, all of the ions originating from the discharge gas were severely quenched without replacement by ions originating from the hydrogen. The cathode ion abundance was also moderately enhanced. Investigations of this effect indicate that chemi-ionisation processes involving highly excited sates of neutral argon may play a significant role in ion formation within the plasma. The formation of anionic species within argon plasmas was investigated. No anion formation occurred unless the plasma contained electronegative species. Mechanisms are proposed to explain the formation of the anions that were detected. A small electric current is generated within the plasma close to the ion exit cone. The effect of several parameters upon this current have been investigated and the results obtained are consistent with this current originating from field-ionisation of highly excited states of neutral argon close to the ion exit cone.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available