page unless you are familiar with High Voltage Safety Techniques
as well as Radiation Protection and Radiation Measurement!
|Have you ever wanted an X-Ray machine of your own, but don't have the $10,000+ to buy a commercial machine? This page will show you how to build your own machine for less than $200! X-rays are created when electrons are accelerated at high speed from the negative electrode (cathode) of a vacuum tube and strike the positive electrode (anode) inside the tube. Some vacuum tubes used in old radios, televisions, and other antique electronic equipment will generate X-rays of surprising intensity when a high voltage DC potential is placed across one of the heater pins on the bottom and the anode on the top. To locate the heater pins, use a multimeter. The heater pins will show a few ohms, while the other pins will show infinite resistance (open). You can also search the NJ7P Tube Database for information about your tube.Tubes which work best in this configuation are half-wave recitifier and beam triode types such as the 2X2A, 3DR3, 6BK4B, 6EN4, 15E and CRC 816. Testing here at Dangerous Laboratories has shown that the 2X2A works best. We measured intensity of the X-Rays as greater than 200 mR/hr which is the upper limit of our Ludlum Model 3 survey meter with 44-7 geiger tube.The heater pins on the 2X2A are pins 1 and 4. The other tubes mentioned seem to produce arcing across the outside of the tube, which reduces X-Ray intensity.|
|The first step is to locate a 2X2 tube. Fortunately, they are fairly common, and cost from $2.00 to $4.00. Antique Electronics Supply
is a good resource for these tubes. You will also need a high voltage
DC power supply capable of producing in excess of 40,000 volts. Some
experimenters have used a flyback transformer and several voltage
triplers found in old TV sets. I use the "Ion Ray Gun" available from Information Unlimited (part# IOG9K). This sells in kit form for about $130 and fully assembled for about $200. View the schematic for the IOG9K.
It is The ray gun is safe to use, and does not produce dangerous
shocks. It is highly recommended for those who might be new to high
Get some alligator clips, a 12 volt lamp (part# 272-332), a rocker switch (part# 275-694), battery holder (part# 270-407), and a 9V type connector (part# 270-325) from Radio Shack. Don't forget the 8 "AA" batteries. You could skip the "AA" batteries, holder, and 9V-type connector and use any 12 volt DC power source, alternatively. You will also need some high voltage wire to connect the (+) High Voltage output of the Ion Ray Gun to the anode of the tube. We use copper conductor spark plug wire. Most auto parts stores sell spark plug wires as an assembled set for a particular model of car, so they are expensive. Furthermore, most of the newer wires are carbon conductor, which is impossible to solder to. A better bet would be to check your local junkyard for older cars and remove one from a junker. Make sure it is copper core before you take it home. You will need about a foot. Save the boots from the wires to use as insulators. Slide the boots on to the section of wire with the open ends of the boots facing out towards the wire ends and solder the clips onto the ends. You now have your hookup wire.
An enclosure is necessary to protect the operator from the X-Rays! Never energize a tube with high voltage without 1/4" lead shielding! If you are anywhere close to the tube when it is energized, you run the risk of getting severe radiation burns! Be sure to get some lead sheet that is at least 1/4" thick to shield the tube. A metal toolbox lined with lead makes an excellent and inexpensive enclosure. The battery can be disconnected internally and the box padlock to prevent accidents and unauthorized use.
building your machine make sure you have a geiger counter for measuring
the X-Rays. We recommend that you also wear an electronic type
dosimeter such as the Rad Scanner Model 500 available from Meter Conversions.
This unit fits in your shirt pocket and has an audible alarm that
sounds when radiation is detected. It also has a cumulative dose
Don't assume that your unit is not producing X-Rays just because your geiger counter is not registering excess radiation! It is best to treat your machine like a loaded gun and keep the aperture end pointed away from you whenever the battery is connected. It is also advisable to keep the aperture covered with a sheet of lead when the unit is not in use.
|This is the completed unit. We mounted the two switches and two lights in a plastic project box affixed to the top of the toolbox. The switches are hooked up in series as a redundant safety measure. A slide type switch lights the green "armed" lamp and the rocker switch energizes the ion ray gun and red "on" lamp. The above schematic shows only one switch, but you can modify the switch configuration to suit your personal tastes.||This photo shows the front of the unit. The aperture is 2 inches in diameter and was cut with a drill and hole saw. The front if the box is lined with extra lead (except for the aperture) to reduce stray radiation.|
|The lid of the lead-lined box has been removed to show the vaccum tube. A stainless steel hose clamp was attached to the anode terminal of the 2X2A tube, and the spark plug wire attached to it. The 18 gauge ground wire is attached to one of the heater pins on the tube with an alligator clip. The tube is mounted in a piece of styrofoam and secured with plastic cable ties. The styrofoam is secured with velcro which attaches it to the bottom of the lead lined box. The tube has been moved away from the aperture for clarity. In operation, the tube is as close to the aperature as possible, to ensure maximum X-Ray intensity in front of the aperture. We were careful to ensure that the heater pins and anode were not shorting on the inside of the box.|
|The black tube inside the box is the Ion Ray Gun. You can see the spark plug wire running from the Ion Ray Gun to the lead lined box which holds the 2X2A tube.|
that you have your X-Ray machine built, you will want to take some
pictures. You can use black and white photographic paper. Simply place
the object to be photographed between the aperture of the machine and
the photographic paper. This will have to be done in a darkroom with a
safelight, of course.This photo was taken at a distance of 1 cm from
the aperture of the machine. The aluminum screen was clamped to the
paper. The paper is standard Ilford paper. The exposure time was 40
seconds. You can see that the X-Rays did not penetrate the aluminum,
but did expose the paper through the holes. Further experiments with
the geiger counter have shown that the rays will penetrate .016 sheet
aluminum. Check out the X-Ray pictures of our preserved frog!
Commercial X-Ray tubes have a heated filament which produces a greater number of electrons which consequently produce more X-Ray intensity. We have found the opposite to be true with the 2X2A tube. We hooked up a 1.5 volt battery to the heater pins of the tube and energized the HV circuit. The intensity was actually less than with the tube operating in "cold cathode" mode. This phenomenon has been explained in a Bell Jar article by another X-Ray experimenter, Bob Templeman, as follows: "Since the tube is operated in a cold cathode mode, the tube's degree of vacuum is quite important. Bob found that about one in eight tubes is able to produce enough radiation to expose his film. One might ask 'why not just heat the filament to get an assured, controlled emission of x-rays?' The answer lies in the basic characteristics of a high vacuum diode. A `normal' vacuum diode, such as a rectifier tube, operates in a region where the tube current varies nearly linearly with the voltage drop. Thus, substantial increases in current would be required to produce a voltage drop across the tube significant enough to produce useful levels of x-rays. For normal tubes, the current would be well in excess of the tube's power rating. Normal operation for a rectifier tube is moderate to high current with a low voltage drop.What is good for rectifiers is not good for x-ray tubes. In the case of the x-ray tube, the tube is operated in the upper part of the characteristic curve, the 'saturation' region. In this mode, the voltage can be increased with little increase of electron current. Getting the right balance between current and voltage is part of each tube's design. Also, as noted before, varying the filament temperature (e.g. by means of varying the filament voltage) allows the intensity of the tube's output to be adjusted. For each filament temperature, there is a different current vs. voltage characteristic."
|Another interesting way to produce X-Rays is to simply place a tube on top of a tesla coil. We have found two tubes that work for this: 01A and 866A. The intensity of the X-Rays is much less than with the Ion Ray Gun. NOTE - Radiation Danger: Do not stand anywhere near the tesla coil and tube when the coil is energized!!|