An amateur-use open-source gamma spectrum analyzer is being developed by members of the GeigerCounterEnthusiast (GCE) Yahoo Group. This multichannel analyzer (MCA) is based on the STM32F103VBT6 microcontroller. It displays spectra on a color LCD.
To access the design files (and hopefully to participate in the development) you will need to join the GammaSpectrometry Yahoo Group (free membership). Join through: http://groups.yahoo.com/ Continue reading
We built the bulk of our PMT amplifier/processor/discriminator on a Universal PDIP Operational Amplifier Evaluation Module by Texas Instruments (model OPAMPEVM-PDIP). Click on the picture above for a full-size version of the picture.
The diagram in the following pdf file shows the connection layout for the circuit shown in the book’s Figure 34: PMT Processor PCB Continue reading
The book’s Figure 32 shows the schematic diagram for a low-cost, variable-voltage PMT power supply based on a BXA-12579 inverter module that is originally designed as a power supply for cold-cathode fluorescent lamps. This under-$20 module produces 1,500VAC at around 30kHz from a 12VDC input.
We are posting this picture to help you build your own power supply. It shows the BXA-12579 that has been modified as described in the book. The op-amp to the right of the CCFL module is used to control the voltage supplied to the module. The high-voltage AC output of the inverter is rectified and doubled and filtered by the diodes and capacitors at the left of the CCFL module. Continue reading
This is the datasheet for the RCA 6655A PMT used in the probe shown in the book’s Figure 30: RCA_6655A_Datasheet
This is the datasheet for Hamamatsu’s replacement of the RCA 6655A PMT: Hamamatsu replacement for RCA 6655A R2154-02
Schematic diagrams for the probe are in Figure 29.
We are posting this picture to help you construct the variable-output, low-ripple, high-stability, high-voltage power supply described in pages 38-40 of “Exploring Quantum Physics Through Hands-On Projects.” The schematic diagrams for this power supply are in the book’s Figure 31. Output voltage (up to 2 kV) and current (up to 1 mA) are monitored via two LCD panel meters. 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
Figure 54 in the book shows our setup based on a 6AF6-G “magic eye” tuning tube to measure e/m. The pictures in this figure supplement the book’s Figure 54 to help you build your own system. In the 6AF6, electrons produced by a thermionic cathode cause fluorescence on the tube’s anode. Applying an external magnetic field curves the path of the electrons reaching the anode’s fluorescent coating. Knowing R and the voltage applied to the tube allows one to calculate e/m. Continue reading
Figures 51 and 52 in the book show how to use an oscilloscope 2AP1 CRT to measure e/m using Hoag’s method. The pictures in this figure supplement the book’s, showing you how to construct the d.i.y. setup, as well as the way in which the electron beam fan is reduced to a point as the magnetic field fulfills the focusing equation. In this setup, an AC signal is placed across one set of plates of the CRT to produce a line on the screen. The solenoid is then energized until the line makes one complete helical turn. Continue reading
This is a supplementary picture to the book’s Figure 43. It shows our d.i.y. “Maltese Cross” CRT connected to the vacuum system and high-voltage power supply. Please note that the HV power supply is configured to produce a negative output referenced to ground. The anode and target electrode are at ground potential. The cathode rod inside the glow-discharge electron gun is connected to -HV. Continue reading
This figure supplements the book’s Figure 42. The book’s figure describes the features that appear in the glow discharge. However, we felt that a color picture is required as a cross-check to help you correctly set up your own system. 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
