In my previous post, I revealed a look at the new enhanced extractor design for the AIS-ILIS1 ionic liquid electrospray thruster. Continuing with the design overview, here is a look at field simulations for the extractor.
This first set of results looks at the field at the emitter edges looking down into the extractor. The left picture is the original straight slit that was used in the recent test with a linear 0.75mm wide slit aperture, while the right is the enhanced slit design.
We can see a major difference in field strength and enhancement at the corner of the emitter. In the original linear slit design, field strength is the highest at the corner, causing emission for occur there the first, and increasing in intensity as emitter voltage is increased. However, I want to reduce field enhancement here, and instead focus it along the length of the emitter so that turn on and bulk emission occurs along the central region. In the new design, field strength at the corner is reduced to a value lower than the central region, where field enhancement has been significantly increase. Although I lose a few mm of effective emission length along the emitter as a result, I hopefully gain more uniform and reliable emission overall as a result, and eliminate turn-on at the corners.
In this second set of simulation results we see a comparison of the extraction field viewed as a cross section of the emitter/extractor interface. The left picture depicts the fields from the original 0.75mm wide slit, which is also a bit over 0.1mm thick. On the rigth, we see the new extractor design, with a much narrower slit width, and thicker extractor plate. The new thinner slit significantly increases field strength, allowing for lower turn-on voltage. In addition, by using a thicker plate, beam divergence can be reduced from the original thinner one, at the cost of some additional beam intercept at the extractor.
The new design, which is being laser cut from thin stainless steel spring temper stock, is already under production, and should be arriving within the next week or so.