Analysis of a laser induced plasma in high pressure SF6 gas for high-voltage, high-current switching

<p>The Laser Triggered Switch Program at Sandia National Laboratories is an intensive development study to understand and optimize the laser triggered gas switch (LTGS) for the Z-Refurbishment (ZR) project. The laser triggered gas switch is the final command-triggered switch in the machine, and reliability and performance of the switch is crucial. A modified LTGS trigger section with optical viewing windows perpendicular to the laser propagation is used to analyze a laser induced plasma spark in SF6 gas in order to quantify parameters such as spark length and plasma temperature. The laser spark is created through a focusing lens by the fourth-harmonic (266nm) of a 5ns FWHM pulsed Nd:YAG laser with 30mJ maximum energy output. Several diagnostic methods are used to analyze the laser spark. Visible spark length measurements are made using a lens system mounted to a CCD camera at gas pressures ranging from sub-atmosphere to four atmospheres. Differing focal length lenses are compared to determine an optimal focal length for a given gas pressure and laser energy. The visible length of the laser induced plasma channel is used as an indicator of the ability of a spark to trigger a switch at a given gas pressure and charge voltage. As a rule of thumb, the visible spark length must be at least 30% of the electrode gap spacing to produce acceptable switch run-time and jitter. Schlieren imaging and electrical length measurements using a capacitive probe are also used to obtain laser induced spark lengths. Spectroscopy is used to estimate laser plasma temperature from which plasma resistivity is calculated.</p>

Name thesis:degree_name

Optical Science and Engineering

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Optical Science and Engineering

Year

2007

Author dc:creator

• Clark, Waylon

Contributors dc:contributor

• Gilmore, Mark
• Savage, Mark
• Lynn, Alan

• Laser plasmas.
• Other Engineering

Language dc:language

English

Repository record dc:identifier

https://digitalrepository.unm.edu/ose_etds/53

OAI identifier oai:identifier

oai:digitalrepository.unm.edu:ose_etds-1052