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: mightyohm.com/blog/products/geiger-counter/

• #science_technology
• #x_rays
• #xrays
• #811a
• #vacuum_tube
• #cold_cathode
• #tube