Open Collections will undergo maintenance on Thursday, July 24th, 2025. The site will not be available from 8:00 AM - 9:00 AM PST and performance may be impacted from 9:00 AM - 12:00 PM PST.

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Measurement of small shifts of wide lines Potter, Michael Urwin

Abstract

A new technique has been devised to obtain time-resolved measurements of small spectral line shifts. Two linear neutral density wedges with opposite transmission gradients were placed over the top and bottom of a monochromator exit slit in such a way that a wavelength shift of a spectral line resulted in a change in light intensity transmitted through the wedges, which was monitored by two photomultipliers. To test this technique, an N II line, for which Griem has calculated the Stark shift as a function of electron density, was observed in the emission spectrum of a small theta-pinch using a monochromator of 10 Å/mm inverse dispersion. Space and time resolved line shift measurements were made and were associated with the axial velocity and the electron density fluctuations of the plasma. An uncertainty of 0.015 Å was estimated, which, for the 1.5 Å line used, corresponds to a shift to width ratio of 10⁻², believed to be lower than any previous shift measuring technique. Time of flight velocity measurements and conservation of mass considerations have confirmed the results as both reasonable and self-consistent.

Item Media

Item Citations and Data

Rights

For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.