Optical Plasma Phenomena

Charles Danforth, SSX

Though not one of the main areas of experimental research in the Swarthmore Magnetofluids Lab, optical phenomena of plasmas are easily studied given the current setup. It also happens to be an area of personal expertise. The vaccuum vessel is fitted with a transparent window in one of the ports through which light generated by the plasmas can escape.

The project has three stages.

Recent Notes


The first few firings with DD1 (Danforth Detector 1), the commercial single-channel detector, show interesting results. The data followed expected trends with a rapid rise in intensity followed by an exponential fall-off probably due to radiative cooling of the plasma. There is a region between the rapid rise and the cooling phases where the intensity continues to rise. My hypothesis is that this is the phase where the plasma leaks out of the spheromak and diffuses through the hole in the small flux conserver.

An unexpected find is that DD1 is an excellant diagnostic as to whether or not a spheromak was formed. In the case where the plasma disconnects from the stuffing flux, a great deal of plasma leaked through the hole in the flux conserver (red line). In the case where the gun did not "unstuff", most of the plasma was trapped between the electrodes and almost no light was produced (blue line).


After having fixed the shutter assembly, it has been determined that there is something wrong with the CCD camera's imaging capability. Despite our best efforts, the camera won't work for us. It has been returned to Photometrics for repairs. We expect it back in a few weeks at which point it can once again be hooked up to the spectrograph and data can be taken. An unfortunate setback.


After several days of work DD3 (Danforth Detector 3) has been completed. It is based around three photodiode detector chips with on-board amplification and is powered by two 9-volt batteries. The filter holder is adapted to use standard astronomical one-inch diameter filters up to 3/8" thick. I look forward to first light on this third phase of the project. Unfortunately, with the current lack of functioning spectrograph, we will have to wait on ordering the filters.


August 7, 1996 / Charles Danforth `95 / danforth@ccs.uky.edu