Experimental Modern and Quantum Physics for Do-It-Yourself Science Enthusiasts 

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d.i.y. GPS-Disciplined 10 MHz Frequency Standard / GPS-Based Universal Time Clock

diy GPS-disciplined 10 MHz frequency reference by David Prutchi PhD www.diyPhysics.com

Last week I posted detailed construction information for my rubidium atomic clock frequency reference.  Besides that unit, I also built a GPS-disciplined 10 MHz oscillator to serve as a secondary frequency reference, as well as a source of GPS NMEA data for my ham shack instruments that can use precise location and real-time-clock data (e.g. for satellite tracking). Read more…

 
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d.i.y. 15 kV @ 30 mA Floating-Output AC or DC High-Voltage Power Supply

15 kV @ 30 mA diy High Voltage Power Supply by David Prutchi PhD www.diyPhysics.com

Transformers made for powering large neon signs are inexpensive and very reliable.  Most commonly, the secondary is center-tapped, which prevents the use of its full peak-to-peak output in applications where one of the terminals needs to be grounded.

In the power supply described in this post, I took out the high-voltage transformer out of its metallic enclosure to isolate the center tap from ground.  This requires very careful application of a thick insulated layer to the transformer.  I used a full can of Shellac to patiently coat and re-coat the transformer. Read more…

 
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d.i.y. 10 MHz Atomic Clock Frequency Standard Using Surplus Rubidium Oscillator

diy Rubidium Atomic Clock 10 Mhz Frequency Reference by David Prutchi Ph.D. www.diyPhysics.com

Efratom Model M-100 Rubidium Frequency Standard (RFS) oscillators are widely available in the surplus market.  Units on eBay commonly sell in the $150 to $200 range.  Despite their low surplus price, they were originally very expensive components, with superb performance.  The M100 was designed to be used by the military as a master oscillator in high-performance communication systems, frequency standard equipment, advanced navigation equipment, and all other systems which require extremely precise frequencies and time intervals.

With the proper input power provided and suitable cooling provisions, you can turn a surplus M-100 into a free-standing 10 MHz +/-5×10-11  (+/-5 x 10 ^-11 in case that your web browser doesn’t display the superscript font) frequency standard for frequency counters, as well as a precise calibration source.  I use mine to keep precise track of frequency when working on Earth-Moon-Earth (EME) communications, where even tiny errors in tuning can make the difference between success and failure to receive weak echoes. Read more…

 
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d.i.y. Quantum Dot Synthesis

CdSe nanoparticle suspension of quantum dots of the type used by David and Shanni Prutchi www.diyphysics.comExperimental chemistry is not our forte, so we prefer to use professionally-manufactured quantum dots for the Schrödinger’s Wave Equation experiments we discuss in the book‘s Chapter 7.  However, if you are interested in synthesizing your own quantum-dot nanoparticle suspensions, we recommend that you take a look at the detailed instructions prepared by  Professor George Lisensky at Beloit College for the Preparation of Cadmium Selenide Quantum Dot Nanoparticles (Local printer-friendly copy at: CdSe_Quantum_Dot_Synthesis). Read more…

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

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. Read more…

 
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Universal Resonant Transformer Driver (High-Voltage Flyback Driver)

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.  Read more…

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

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.  Read more…

 
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Engineer’s Date Night

Engineer's date night by Daniel Vasconcellos

Image Credit: Daniel Vasconcellos

From:  http://www.edn.com/article/471834-Something_from_nothing.php

 

 
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d.i.y. CW CO2 Laser Power Meter Posted at www.prutchi.com

diy CO2 laser power meter by David Prutchi, Ph.D.

I just posted at www.prutchi.com the construction of a simple, but very useful laser power meter.  I used it to tune my 18 W CO2 laser, but the concept is applicable to any other high-power CW laser.  Click here for a direct link to the blog post.

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

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 Read more…

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

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. Read more…

 
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Open-Source Handheld Gamma Spectrometer on Yahoo Group GammaSpectrometry

GammaGrapher Open-Source MCA developed by members of Yahoo Group GCE

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/ Read more…

 
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d.i.y. Handheld Multichannel Analyzer (MCA) based on 16F877 PIC Microcontroller and LCD

Isotope gama spectra obtained with d.i.y. multichannel analyzer (MCA)

Some time ago I was developing a medical instrument which required histogramming, which got me in the mood to retake my own PIC MCA project(http://home.comcast.net/~prutchi/index_files/scint.htm ).   I used the variable RAM in the microcontroller (16F877), so I limited the number of channels to 95 and let the histogram run until some channel reaches 240 counts (the highest 8-bit number that yields an integer when divided by 8 which is also divisible by the 30 pixel height of the LCD). The firmware then displays the spectrum as a bar with a maximum height of 30 pixels for each one of the 95 channels. Read more…

 
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Prototyping PCB for d.i.y. Photomultiplier (PMT) Amplifier/Processor

Printed circuit board for diy PMT amplifier, processor, discriminator and scintillator detector

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  Read more…

 
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d.i.y. Mod for Perkin Elmer SPCM-AQR Single-Photon Detector Module to Improve Photon Timing Performance

Perkin-Elmer SPCM for diy quantum entanglement experiments modified to improve photon-counting timing performanceI. Rech, I. Labanca, M. Ghioni, and S. Cova of the Politecnico di Milano in Italy described an interesting modification to the Perkin Elmer SPCM-AQR Single-Photon Counting Module (SPCM) to improve its timing characteristics in:

I. Rech, I. Labanca, M. Ghioni, and S. Cova, “Modified single photon counting modules for optimal timing performance“, Rev. Sci. Instrum. 77, 033104 (2006); doi:10.1063/1.2183299 (5 pages). Read more…

 
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