Fusor Forums

Hi Everyone,

I recently completed my demo fusor (used the design from make magazine). However, the problem that I am having is that rather than getting a purple glow, I am getting an orange arcing. The inner grid is arcing with the top and bottom of the chamber (which are grounded). More so, it is getting extremely hot - I fabricated my inner grid from stainless steel wire, and I am having it get so hot that the stainless steel wire is actually melting. I think these problems are due to a weak vacuum - my vacuum pump is a new refrigeration pump designed to get to 70 microns.

Would a stronger vacuum solve these problems?

It is almost certainly a vacuum issue. If the pump outlet is spewing oil vapor, then you definitely have a leak. I'm assuming you don't have a vacuum gauge?

I don't have a good enough vacuum gauge. I'm not seeing any leaks though and the oil level looks fine.

Cameron, I think this thread is in the wrong forum. It fits the description for New User Chat Area.

As Liam said, your pressure is _much_ too high. Got a vacuum gauge of the kind shown in Make magazine, which fusioneers snickered at? They should be able to plainly show the difference between the vacuum from your new pump by itself, and pressures causing the arcs you described. Outer scale ticks in picture are 1/2 inch of mercury = 12.7 torr. You can read pressure differences much more accurately than absolute pressures.

I bet if you put oil on outside of your leak you will see it get sucked in. How fast does the pressure go up when you turn the pump off, or valve it off from chamber? I hope you are not pointing the finger of suspicion at your new pump, instead of at the handiwork of a vacuum novice.