Augusta Physics

Cloud Chamber Media and Notes

Optical Analysis of Nuclear Decay in a Cloud Chamber

Andrew L. and Khang K.

Advanced Laboratory

Undergraduate Physics,

College of Science and Mathematics, Augusta University

Acknowledgments and Special Thanks

We are especially thankful for Workforce Opportunities in Regional Careers (WORC) program and Augusta University for their comprehensive assistance and support.

  • Dr. T. DeSilva for mentorship in theoretical quantum physics,
  • Dr. J.A. Hauger for electronics and micro-computing assistance,
  • Dr. J. Newton for assistance and mentorship with nuclear theory,
  • Dr. N. Yanasak for assistance with programming image processing,
  • Mr. O. Angelton for assistance with laboratory materials, and
  • Mr. W. Cooke for assistance with system integration.

Abstract

We intend to identify and characterize decay phenomena in radioisotopes using a cloud chamber and optical measurements. The cloud chamber uses an extreme temperature gradient to hold isopropyl alcohol. Radioisotope source disintegrations emit charged particles which can cause localized ionizations in the vapor, the ionization and transfer of energy produces condensation phase transition with visible characteristic trails. We use ceramic heaters and PTC heating elements as well as dry ice to produce the desired temperature gradient in the chamber. We capture cloud chamber images using a single board computer, programmable LEDs, and a programmable camera. Tungsten thoriated rods and americium sources are visible without optical assistance.

Selected Media

Video 1: To increase the contrast of ionizations in the chamber, a 2.5 kV voltage generator is used to produce a vertical electric electric field.
Video 2: We identify a small but clearly visible alpha track during initial trials. We use trial images to evaluate camera and video analysis codes.
Video 3: We identify Alpha decay in an Am-241 Source.
Video 4: Camera Test with Th-232 Source

Conference Poster

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Download Working Paper

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Background

If seeing is believing, then observation is probably the best method for presenting the atomic phenomena. To meet this challenge, cloud chambers serve as an exceptionally suitable method to observe the nuclear phenomena.

Cloud Chambers were first developed by Charles Thomson Rees Wilson and applied in experimental analysis in 19121. The cloud chamber uses temperature gradient in a sealed chamber. The gradient helps create a region of air supersaturated with isopropyl vapor. Radioisotope source disintegrations emit charged particles which transfer energy to the supersaturated vapor2. Decay energy and particle mass produce phase transitions with characteristic condensation vapor trails3. Laterally angled illumination increases visible contrast in decay trails for video analysis3. Particles from atomic disintegrations become visible by unassisted eye

Theory

The general formula for Alpha Decay is:

{^{A}_{Z}X_N}\rightarrow{^{4}_{2}He^{2+}}+{^{A-4}_{Z-2}Y^{2-}}

Method

For analysis, we use 2% and 4% tungsten-thoriated rods as cloud chamber sources. The tungsten is most likely one of the most abundant and stable isotopes of tungsten so decay activity is not expected. We assume the thorium in the rod is likely the most naturally abundant isotope, thorium-232. We use an americium-241 source from a smoke detector.

Materials

  • Cloud Chamber Enclosure
    • 5.5-gallon standard glass aquarium
    • Steel Plate
    • Foam Board Insulation 1-in sheet
    • Source element holder (3D Printed)
  • Radioisotope Samples
    • 2% Tungsten-Thoriated Rods
    • 4% Tungsten-Thoriated Rods
    • Americium Source
    • 3D-Printed Heater Stand
  • 99.0 % Isopropyl Alcohol
  • Heating Element,
    • 50C/70C/110C PTC Heating Element
    • Meanwell 24v 25A Power Supply
    • Aluminum and 3D-Printed Heater Stand
  • Raspberry Pi Imaging Unit,
    • Raspberry Pi 4 Model B with peripherals
    • Standard Monitor
    • Power Supply Unit, USB-C, 5.1V, 3A
    • Camera Module 3 NoIR
  • Lighting Unit,
    • Meanwell 5v 3.0A Power Supply
    • NeoPixel Fit0612
  • Power Relays
    • Meanwell 5v 3.0A Power Supply

Results

We identify characteristic Am-241 and Th-232 alpha decay phenomena that manifest as condensation trails in the vapor. Image series of Th-232 shows a characteristic 4.08 MeV alpha decay causing  ionization and disrupting transport along a radial4.  Image series of Am-241 characteristic 5.64 MeV alpha decay showed several simultaneous decay tracks in a 2-dimensional fan. Am-241 shows a higher rate of ionization, which agrees with the higher isotopic activity as compared to Th-232 (432.6 y for Am-241 and 14×109 y for Th-232) 4

Conclusion

Improved conditions are needed to produce favorable imaging conditions or identify a proportional count rate

In future research, we plan to , construct acrylic or engineered glass chamber enclosure, integrate and program thermocouple and heating elements, improve video capture methods to pursue optical counting, and study alternate radioisotope sample sources.

Reference Annex

1 Britannica, T. Editors of Encyclopaedia (2023, February 10). C.T.R. Wilson. Encyclopedia Britannica. https://www.britannica.com/biography/C-T-R-Wilson

2 Interview of Luis Alvarez by Charles Weiner and Barry Richman on 1967 February 14, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/4483-1

3 B. Allison, Particle physics -cloud chambers activities for

schools (2012), https://www.birmingham.ac.uk.

4 National Nuclear Data Center. “NuDat 3.0 database”. Brookhaven National Laboratory. https://www.nndc.bnl.gov/nudat3/