Ludlum general-purpose ratemeters are professional-grade instruments that are available on the secondary market at affordable prices. They are compatible with a wide variety of probes, making them a great choice for educators, surveyors, and advanced amateur users. However, probes for Ludlum ratemeters are often as expensive as the meter instrument itself, making it worthwhile to build comparable versions from surplus components.
We just finished constructing a low-cost, yet highly sensitive gamma-ray scintillation probe for our CDV700-Pro counter. The probe is based on a Philips XP5312/SN photomultiplier tube (that is available from Sphere Research) and a piece of scintillation plastic. The probe yields a background count of approximately 1,000 counts/minute (cpm) in our lab, and 7,400 cpm from a 137Cs 6.7 µCi exempt source at a distance of 30 cm. The probe’s sensitivity, portability and rugged construction make it an ideal choice for surveying.
Image Credit: Images Scientific Corporation
Images Scientific Corporation just announced a new Geiger counter wand base provides a stable platform to hold the Geiger counter wand for experiments. The physical dimensions of the holder are 2″ wide by 12″ long. The length of the sled has markings in both metric and imperial.
The sled isotope holder provides a stable and moveable platform for radioactive isotopes 1″ diameter discs. The sled isotope holder is available in two sizes: One that holds 1/8″ thick discs and the other to hold 1/4″ thick discs.
When used in conjunction with the Sled isotope holder a number of nuclear experiments may be performed such as the Inverse Square Law of radiation, half life, shielding effects, etc.
I purchased two “Giant Super Sensitive MC6” GM tubes from Electronic Goldmine (Item Number : G18717, Unit Price: $89.95). These are Russian-made new-old-stock model MC6. They are 10.25″ long x 0.9″ diameter. I compared the sensitivity of these tubes to the other GM tubes that I use with my CDV700 Pro Geiger Counter. Continue reading
The book’s Figure 65 shows our β-particle magnetic deflection setup. It consists of a 90Sr disc source of beta particles, two copper washers to collimate the beam, and GM tubes placed at 0º and 90º to the β-particle beam. A sufficiently strong magnetic field (around 800 Gauss = 0.08 Tesla) provided by a permanent magnet bends the beam so much that it is easily detected at a right angle (notice the meter needles in the pictures above).
The attenuation of radiation as a function of distance can be measured using a radiation counter with a Geiger-Müller tube that is sensitive to α, β, and γ radiation. We used exempt plastic-disc sources containing Polonium 210 (210Po), Strontium 90 (90Sr), and Cobalt 60 (60Co) to experiment with the penetrating power of α, β, and γ radiation in air. Continue reading
We modified a surplus Civil Defense V-700 radiation survey meter made by Electro Neutronics Inc. (Model 6-b) into a very capable radiation counter capable of working with both Geiger-Müller and PMT scintillation probes. We modified the front panel to accommodate the new switches, connectors, and panel light. In addition, we placed a Veeder-Root count totalizer module on the side of the box. The new electronic components, including a Zener diode stack and a PMT preamplifier are wired directly to the original printed circuit board. Continue reading
