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Category Archives: Chapter 3 – Atoms and Radioactvity

Reader-Built e/m Measurement System Showcased on YouTube

Posted on December 8, 2013 by David Prutchi Posted in Chapter 3 - Atoms and Radioactvity, e/m Measurement, Electron-Beam Tube

Javier De Elias Cantalapiedra from Madrid, Spain posted the YouTube video above to show the e/m measurement system that he put together based on the description in our book.  His measurement system is based on Hoag’s method, and his nicely laid-out setup allowed him to obtain very nice results (4 to 6% error compared to the theoretical e/m).

Javier is an industrial engineer who works in the telecommunications industry.  However, his passion is physics, which he pursues at a (very high) amateur level.

Thank you Javier for sharing!

 

Original Source for Flyback Driver Hack?

Posted on May 8, 2013 by David Prutchi Posted in Chapter 3 - Atoms and Radioactvity, High-Voltage Power Supply

Flyback driver circuit from Radio Electronics September 1981 David Prutchi PhD www.diyPhysics.com

One of my all-time favorite circuits is the the following DC-to-AC inverter (click diagram to enlarge) based on an old color TV flyback:

High voltage AC driver for 250 kV DC power supply by David and Shanni Prutchi

Continue reading→

diy Scintillation Probe for Ludlum Ratemeters Using Surplus XP3312/SQ PMT

Posted on March 22, 2013 by David Prutchi Posted in CDV700 Pro Geiger-Müller Counter, Chapter 3 - Atoms and Radioactvity, Ionizing Radiation Detection, Photomultipliers, Scintillation Detector

 

Low-Cost Scintillation Probe Based on a Surplus XP3312 PMT for Ludlum Ratemeters www.diyPhysics.com prutchi

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.

Continue reading→

80 µCi Americium-241 Sources Inside Old Pyrotronics F3/5A Smoke Detectors

Posted on January 20, 2013 by David Prutchi Posted in Chapter 3 - Atoms and Radioactvity, Radioisotopes

Pyrotronics F3/5A 80uCi Am-241 Source

These are pictures of the Americium-241 sources inside some old Pyrotronics F3/5A smoke detectors that were being decommissioned.  The activity of the Am-241 sources at the time of manufacture (1970s) totaled  80 µCi, so they should still have some ~70 µCi left in them.

80uCi Am-241 Label on Pyrotronics F3/5A smoke detector

The Pyrotronics F3/5A smoke detectors were manufactured in the early 1970s. The radioactive sources consist of americium oxide mixed with gold powder and formed into a small billet. This billet was then placed between a sheet of silver and a sheet of gold and rolled into a foil under high heat and pressure.  Americium-241 decays primarily by alpha particle emission to neptunium-237, along with low energy gamma radiation, with a 59.5 keV gamma emission being most prominent.

Continue reading→

A Low-Cost, Super-Sensitive Paint Can Scintillation Probe for the Prutchi CDV700-Pro

Posted on January 12, 2013 by David Prutchi Posted in CDV700 Pro Geiger-Müller Counter, Chapter 3 - Atoms and Radioactvity, Scintillation Detector

 

Shanni Prutchi Paint Can Scintillator PMT www.diyphysics.com

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.

Continue reading→

Using the $79 SainSmart DSO201 Pocket Oscilloscope and GammaGrapher with the PMT/Scintillation Probe

Posted on September 21, 2012 by David Prutchi Posted in Chapter 2 - Light as Particles, Chapter 3 - Atoms and Radioactvity, Chapter 5 - Wave-Particle Duality, Compton Scattering, MCA/PHA, Photomultipliers, PMT/Scintillation Processor, Scintillation Detector, Single-Photon Experiments

Connects directly to PMT probe shown in the book’s Figure 30 with no need for PMT amplifier!

 

Freeware Gamma Grapher MCA with diy PMT Scintillation Probe by David and Shanni Prutchi diyPhysics.com

The nice guys at the Yahoo GammaSpectrometry Group developed multichannel analyzer software for the $79 SainSmart DSO201 Pocket-Sized Digital Oscilloscope.  The upload of the MCA software to the oscilloscope is really easy (via USB), and it allows the PMT probe shown in the book’s Figure 30 to be connected directly to the oscilloscope’s input with no need for a PMT amplifier!

Continue reading→

New Isotope/Geiger Tube Holder at Images Scientific

Posted on April 22, 2012 by David Prutchi Posted in Attenuation of Radiation, CDV700 Pro Geiger-Müller Counter, Chapter 3 - Atoms and Radioactvity, Ionizing Radiation Detection, β-Particle Magnetic Deflection
Radioisotope/GM tube calibrated sled

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.

Continue reading→

d.i.y. Alpha-Particle Rutherford Scattering Experiment – Supplementary Pictures

Posted on March 3, 2012 by David Prutchi Posted in Chapter 3 - Atoms and Radioactvity, Polymeric Radiation Detector, Rutherford Alpha-Particle Scattering

diy Alpha-particle Rutherford scattering device by David and Shanni Prutchi www.diyPhysics.com

The book’s Figures 70 and 71 show our d.i.y. version of a popular apparatus to measure alpha particle scattering.  The figure above shows additional views to help you build your own.  The apparatus allows you to demonstrate alpha particle scattering discovered by Ernest Rutherford in 1908.  Fundamental to the discovery of the atom’s structure, the experiment demonstrates that the charge of the atomic nucleus is concentrated at the center of the atom. Continue reading→

Connecting to Surplus Scionix Miniature Scintillation Probes

Posted on February 20, 2012 by David Prutchi Posted in Chapter 3 - Atoms and Radioactvity, Chapter 5 - Wave-Particle Duality, Ionizing Radiation Detection, Photomultipliers, Radio-Isotope Identification, Scintillation Detector

Scionix miniature photomultiplier scintillation probe David Prutchi PhD www.diyPhysics.com

Lemo connector on Scionix miniature photomultiplier scintillation probe David Prutchi PhD www.diyPhysics.com

Scionix in The Netherlands has taken advantage of the recent development of miniature mesh-type dynode photomultiplier tubes to construct small-diameter scintillation probes.  Scionix’s miniature probes incorporate one of those PMTs, a NaI(Tl) scintillation crystal, and a built-in dynode voltage divider.  Connection to the probe is made through a miniature high-voltage locking coaxial connector.  Finding a mating connector is the main problem faced by enthusiasts who find these probes in the surplus market. Continue reading→

Simple d.i.y. Bias-T for Scintillation Probes with Single Connector

Posted on February 20, 2012 by David Prutchi Posted in Chapter 3 - Atoms and Radioactvity, Chapter 4 - The Priciple of Quantum Physics, MCA/PHA, Photomultipliers, PMT/Scintillation Processor, Radio-Isotope Identification

diy Signal/High-Voltage Splitter for Scintillation Probe with Single Connector David Prutchi www.diyphysics.comMany surplus scintillation probes have a single connector through which the PMT is fed with high voltage and the anode signal is output.  However, this may require an external “Bias-T” (a high voltage / signal splitter) to connect the probe to a high-voltage power supply that is separate from the PMT amplifier/processor. Continue reading→

Adding Your Own Primary to High-Voltage Flyback Transformer for Resonant Driving

Posted on February 10, 2012 by David Prutchi Posted in Chapter 3 - Atoms and Radioactvity, High-Voltage Power Supply 3 Comments

High voltage flyback transformer by David and Shanni Prutchi www.diyphysics.com

Our two prior posts show how to build very high voltage power supplies using flybacks from old color TVs.  The advantage of the method we use is that any flyback can be driven, regardless of how its primary is wired.  This is because we wind our own primary using litz wire. Continue reading→

Universal Resonant Transformer Driver (High-Voltage Flyback Driver)

Posted on February 10, 2012 by David Prutchi Posted in Chapter 3 - Atoms and Radioactvity, High-Voltage Power Supply

Universal resonant transformer driver by David and Shanni Prutchi www.diyPhysics.com

We use the flyback-driver circuit shown in our d.i.y. 250 kV DC power supply in many other of our setups, so we built a stand-alone universal resonant transformer driver.  Continue reading→

d.i.y. 250 kV High Voltage DC Power Supply with Neat Trick for Switching Polarity

Posted on February 9, 2012 by David Prutchi Posted in Chapter 3 - Atoms and Radioactvity, High-Voltage Power Supply

d.i.y. 300 kV DC high voltage power supply by David and Shanni Prutchi

High voltage DC power supplies are used by science enthusiasts for powering electron tubes and x-ray tubes, charging high-voltage capacitors, powering electrostatic “levitators”, etc.  Many of these power supplies use a flyback transformer to produce high voltage at high frequency (AC), followed by a “Cockroft-Walton Multiplier” to rectify and dramatically increase the voltage.

The Cockroft-Walton multiplier uses a cascaded series of diodes and capacitors to generate a high voltage DC potential from an AC input through a circuit topology that uses diodes to charge capacitors in parallel and discharge them in series.  The output polarity of the Cockroft-Walton multiplier depends on the way in which its diodes are oriented, so the output polarity (referenced to ground) of a high-voltage DC power supply is usually set during the design.

However, since some of our physics experiments require one or the other polarity, we build our Cockroft-Walton multipliers with an extra capacitor so that we can make our HV power supplies output either positive or negative high voltage referenced to ground.  Continue reading→

Home-Built Radiac (Radiation Detector and Meter) for a Surplus DT-590A/PDR-56F Scintillation Probe

Posted on February 2, 2012 by David Prutchi Posted in Chapter 3 - Atoms and Radioactvity, Ionizing Radiation Detection, Photomultipliers, Radio-Isotope Identification, Scintillation Detector

Home-Made PDR-56F Radiac for a surplus DT-590A/PDR-56F Plutonium Contamination Probe

Military DT-590A/PDR-56 “x-ray” probes are widely available in the surplus market.  They were meant to be used with the military Radiac Set AN/PDR-56, which is a portable scintillation-type instrument used for detection of plutonium-239 contamination. In addition to emitting 5.1 MeV alpha particles, Plutonium-239 also emits gamma rays in the energy range of 14 to 21 keV. Because these gamma rays are more penetrating than the alpha particles, they travel further in matter and air and can be detected at longer distances from the ground. The probe uses a CaF2(Eu) scintillator/photomultiplier combination to detect these 14-21 keV gammas from Pu-239. The discriminator inside the probe is factory-tuned to detect only pulses from the Pu-239 gamma rays. Hopefully you don’t have plutonium contamination in your basement, so you can set the discriminator window wide open to make the probe sensitive to a much wider range of gamma energies. In addition, you can replace the CaF2(Eu) crystal by a NaI(Tl) scintillation crystal assembly. This will turn the instrument into a general-purpose gamma radiation detector that will outperform virtually any handheld Geiger counter in the detection of 100keV to 1.3MeV photons.

PDR56 Circuit Continue reading→

Converting a DT-590A/PDR-56F “X-Ray” Probe into a General-Purpose NaI(Tl) Gamma Probe

Posted on February 1, 2012 by David Prutchi Posted in Chapter 3 - Atoms and Radioactvity, Ionizing Radiation Detection, PMT/Scintillation Processor, Scintillation Detector

PDR56 probe modification for general-purpose gamma detection

The military Radiac Set, AN/PDR-56 is a portable scintillation type instrument used for detection of alpha contamination. The system includes a large and small interchangeable probe with a probe extension.  This system is being phased out by the US Air Force, so new probes are becoming widely available in the surplus market.

The “x-ray” probe for the AN/PDR-56 uses a CaF2(Eu) scintillator/photomultiplier combination to detect the 14-21 keV gammas from Pu-239. The x-ray probe is an assembly which includes the amplifier-discriminator circuits integral to the phototube scintillator housing. The discriminator is a single channel analyzer adjusted to detect Pu-239 gamma rays. Continue reading→

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