To Echo3Romeo
That is a good suggestion, but it may fail to glow if his current production is as low as I think it must be. (If his currnet is not almost nill, he should be getting voltage on the dome as every electron placed inside will go to surface.)
The electrostatic foil volt meter I suggested may fail too for essentially the same reason, but it takes almost zero current.
Do you know the current required to sustain a Ne bulb glow?
A NE-2 with a 33k series resistor will have a glow discharge current of about 3.6mA at 120V. Those tend to be rated for higher brightness. Some will remain lit with a 47k resistor, and a discharge current of 2.5mA. I'm not sure what current can be continuously supplied from the face of a CRT. The secondary anode supply (the suction cup on the funnel of the tube's back side) is usually capable of supplying +25kV at 5-6mA, which is somewhere around where the beam current of the electron gun(s) are and therefore enough to neutralize most of the negative charge that would otherwise build up on the front of the picture tube during operation, at least in theory. From simple observation we can conclude that the current that can be collected from the tube face is much, much less, as anything more than perhaps 50 microamperes would present an electrical and radiological hazard to consumers - remember those old TV sets that needed leaded glass and shielding due to the X-rays produced inside the CRT?
An electroscope has the advantage of being able to detect electrostatic fields easier. It registers coloumb electrostatic force rather than the flow of current, so it is capable of measuring and maintaining a steady state. However, a neon lamp will work in a pinch and is easier to get a hold of. There should be plenty of current to get intermittent activity inside the lamp; enough to tell our friend whether or not ions are collecting on the test surface. It will not remain lit continuously, but when the probe lead comes into contact with an area where significant ionization has built up, the rush of current through the lamp will produce a quick flash of light.
Billy T said:
Job was quite an experience as SAC wanted it "yesterday" in cost plus contract and gave huge bonus if delivired in 3 months.
Amazing what can be done when cost is not an issue. It reminds me of something more recent:
C-RAM (that crappy web page is all I could find about it) is a USN CIWS mounted on a flatbed and loaded with self-destructing explosive rounds. Instead of antiship missiles and low-flying aircraft, it can track and engage indirect fires incoming to its position (mortar, rocket, artillery) and shoot them out of the sky. A few of them were slapped together in 2005 as part of a crash program to deal with the artillery threat.
I have no idea how much it cost, I can only say that it works amazingly well.
Here is a video of a C-RAM mount engaging a mortar round in Balad, Iraq (aka Mortaritaville).