------ This guy uses 60kv and a 4-1000a to make x-rays
Of course, producing X-rays is a challenge to every HV experimenter. Since I do not own a "real" X-ray tube at present, I am looking for alternatives. It would be interesting to know how other vacuum tubes behave when exposed to extremely high voltage. My choice falls on a 4-1000A (EIMAC) which has been resting on my shelf for more than 30 years. This is a high power tetrode often used in RF power amplifiers. The anode of this tube is attached only to the top of the glas bulb. Since there are no ceramic spacers between the anode and the other electrodes, the tube should be able to handle high voltages without internal arcing, provided the vacuum is still ok. The specified maximum plate voltage is 6 kV.
4-1000A Transmitter Tube (Manufacturer: EIMAC, USA)
I assume that at a sufficiently high negative voltage with respect to the anode, the wire cage of grid 2 should ionize near-by gas molecules, thus releasing electrons and acting as a cold cathode. Although transmitter tubes have a fairly good vacuum, there is always some residual gas left, particularly after many years of storage. I connect grid 2, grid 1, and both filament pins with each other. The next picture shows the tube with the cathode thus formed connected to the negative (hot) lead of the above multiplier (the anode is grounded). The tube draws about 3 mA under these conditions. Since the voltage drops to about 60 kV under this load, total power dissipation is approx. 180 W (tube gets warm). This is far below the specified maximum plate dissipation of 1 kW (with forced air-cooling). The grids seem to stay more or less cold during this kind of operation (no red glow visible). The photo shows a greenish fluorescence inside the tube system. Occasionally, flashes between the electrodes occur. The state of the vacuum is crucial to the efficiency of the tube running in this mode. Too much residual gas would result in arcing-over, too little gas would reduce plate current and X-ray emission. Actually, this is how the first (cold-cathode) X-ray tubes worked.
4-1000A at 60 kV Plate Voltage
A GM (Geiger-Müller) counter placed near the tube immediately displays an overflow. Since this might be bad for my health, I decide to turn the power off. Next, I operate the HV transformer with a remote-controlled switch from the adjacent room. Even behind a 20cm (0.7 ft) stone wall, the counter shows about twice the normal background radiation. Without shielding, the counter sounds like a machine gun even at a distance of 10 m (33 ft) from the tube. A thick wooden door or a piece of sheet aluminum put between tube and counter does not make much of a difference. Although I used to work with X-rays when I was at the university many years ago, I am still fascinated, and I get a feeling of what W C Röntgen must have thought when he discovered this kind of radiation in 1895.
At full resolution, the photo of the tube (see below) reveals a large number of small bright spots randomly distributed over the whole image area. Since this phenomenon only occurs when taking pictures of the radiating tube, I conclude that the ionizing radiation affects the pixel elements of the CCD sensor (digicam). The distance between tube and camera was approx. 1 m (3.3 ft).
Although this tube can work as an X-ray source, it has a number of drawbacks. Since the radiation is emitted from the whole inner surface of the anode cylinder (penetrating the metal), the radiation is quite diffuse and would lead to indistinct images on a film. To improve image quality, diagnostic X-ray tubes are designed to emit their radiation from a small area of the anode surface (the focal spot where the electron beam hits the target). Moreover, the 4-1000A has an anode with cooling fins which would probably cast shadows. Although the transmitter tube does not show any visible damage after this abuse, it may be possible that the surfaces of the electrodes become gradually modified by ion bombardment, resulting in changed tube characteristics.
All that was the text from his web page ,but it didn't send the photos so you will have to check out his page for those,sorry