Large area detector for X-rays

I built a large area detector that is sensitive to X-rays and will be used in an upcoming project. The detector is constructed from a "Lanex Regular" X-ray intensifying screen, and a Hamamatsu R6094 photomultiplier tube (PMT). The PMT amplifies the light from the intensifying screen which is emitted when an X-ray strikes the screen. The area of the screen allows it to catch many X-ray photons created by backscatter. The PMT is setup with a simple 100K resistor between the anode and ground. A 1V output corresponds to a 1 microamp anode current. I'll probably add a very simple opamp circuit to this, and then pipe it into an A/D converted for digitization.

First test with eBay x-ray tube

 I found an X-ray tube on eBay and fired it up with my Spellman high voltage supply. I ran the tube at about 35-40KV at 180uA. This required a filament current of about 1.5A at 2.5V DC.  With the room very dark, I could clearly see the phosphorescent screen glowing green. It wasn't bright enough for my eye to discern details in the X-ray images, but the camera with a 4 second exposure at f/5.6 and ISO400 was perfect. I took some pictures of various electronic components. I also X-rayed a dead, dried-up bumble bee, and it produced no image at all! The X-rays completely penetrated the insect without any visible absorption. I should have turned down the anode voltage, but I didn't think of this until after I threw away the bee.
The tube is a Nago GFH2-0.3-85-60

Follow-up: Attempting to make X-rays by unrolling Scotch tape -- Success?

In this follow-up video, I show that I was able to get a P47 phosphor disc to illuminate when unrolling tape in the vacuum chamber. The blue x-ray intensifier screen did not illuminate although it was also in the chamber. Also, it seems the P47 was illuminated through a thin copper foil, though I will have to do some more tests to believe this.

Attempting to make X-rays by unrolling Scotch tape (negative result)

A few years ago, a research group posted a video showing that X-rays could be created by unrolling scotch tape in a vacuum. The idea is that the static charge generated by the mechanical unrolling process would cause electrons to accelerate to 50KV (or so), and then produce x-rays when they slam into something. I tried to recreate this experiment, but I had pretty weak results. I may need a much larger vacuum pump to keep the pressure in the chamber very low while unrolling.

Creating X-rays with a standard vacuum tube

I forced an RCA 811A tube to produce some X-rays by operating the tube in cold-cathode mode at about 20KV and 150uA.  The glass fluoresces nicely, but I didn't get any light from my X-ray intensifier cassette.

MightyOhm's geiger counter kit: http://mightyohm.com/blog/products/geiger-counter/