• Tag Archives radioactiviteit
  • Detecting Radon with an ionization chamber

    Since I am interested in radiation I have been looking into ways of detecting radon and logging the results electronically. There are different ways of detecting radon.There are alpha track detectors which measure radon by having the alpha particles damage plastic and analysing the material later. Lucas cells are used to take an air sample and count the amount of alpha decays detected by a ZnS(Ag) scintillator and a photomultiplier.

    Alpha particles are strongly ionizing due to the fact that they are heavy particles that easily interact with matter. They have enough energy to hit a zinc sulphide scintillator and be visible to a dark-adapted human eye.

    A different way of detecting alpha particles is measuring the amount of ions they generate when they travel through a distance of air. By using an ion chamber, these ions can be converted into a measurable current, and even a discrete current pulse for each alpha ionization event.

    I found Alan Yates’ “Ion Chamber Alpha Particle Counter” to be easy to build. It is a small ion chamber with a JFET and a small circuit using a plain TL072 opamp.

    Some notes for anyone building this circuit:

    • A nice ion chamber can be made using a BNC male to SO-239 adapter and the screw hull from a PL-259 connector. Remove the teflon/plastic from the SO-239 end and solder the source of the JFET to the center pin and the drain to the wall. I covered one end of the screw hull with copper tape and punched a lot of holes in it to allow air to enter the ion chamber
    • Shielding of the JFET is critical, if shielding is insufficient the circuit will detect electric fields from static charges, mains voltage etc. and become unstable.
    • The circuit shows a 2N5484, I used a J201 that I intended to use for another type of alpha detector. I did not need to change the 560 ohm resistor on the source of the JFET.
    • It usually takes a minute for the circuit to settle down. This is because the gate of the JFET is floating and slowly charges up to a stable voltage. Before this happens no proper detections can take place.
    • This is a slow detector, when an alpha particle strikes it takes 100’s of milliseconds for the charge to leak away. During this time no other particles can be detected. In practice this is not a problem since alpha count rates even in high radon environments will not exceed the maximum count rate.

    This circuit is highly recommended for people wanting to research radon. It is easy and cheap to build, does not require high voltages and could be easily adapted to enable logging with microcontrollers. The last thing is a matter of converting the output into a 5/3.3V signal using a voltage divider and connecting it to a microprocessor GPIO pin. I am thinking of using a ESP8266 and ESP Easy’s pulse counting feature to make radon measurements available on the network/internet.

    Here is a video of my build of this circuit in action:

     


  • Interfacing the Uradmonitor with the Internet of Things, MQTT and Pimatic

    Intro

    For some time I have owned a Uradmonitor model A unit. This is a radiation monitoring solution which measures radiation and makes it available on a website. Connect it to your local network, and it will automatically get an IP address and start logging to www.uradmonitor.com. There you can find the stations and associated readings on a map.

    Since the Uradmonitor has a webinterface it is easy to scrape the data and send it elsewhere. For example, the CPM can be displayed on a VFD display or displayed in domotics applications.

    At home I try to make any sensor reading available using Mosquitto/MQTT. It is a lightweight, easy to use protocol to distribute dynamic data. Besides the Uradmonitor, multiple NodeMCU ESP8266 units running ESP Easy publish their sensor readings to the local MQTT server. All of this is done by Mosquitto running on my Debian ARM NAS and a Raspberry Pi running Raspbian and Pimatic.

    Scraping and publishing to MQTT

    First off I scrape the data from the Uradmonitor webpage using curl. Then, after some awk and html2text processing it is published to my local MQTT server using the mosquitto_pub MQTT publishing client.

    #!/bin/bash
    uradmonitorcpm=$(curl -s http://<ip of uradmonitor/ | html2text | grep radiation | egrep -o '[0-9.]*')
    mosquitto_pub -m $uradmonitorcpm -t /uradmonitor/cpm

    This bash script runs every minute using /etc/crontab and updates the local MQTT server with the latest measurement. The command ends with the MQTT topic which is the “address” of the dynamic value on the MQTT server.  Please note that mosquitto_sub does not need an IP address when publishing to localhost/127.0.0.1 since that is a default of the client. To specify a host, use the -h <ip address of mqtt server> option. Continue reading  Post ID 3618


  • Sterrenstof

    Op deze site schrijf ik vaak artikelen over radioactiviteit. Ik heb zelfs een geheel losstaande pagina aan dit onderwerp gewijd. Een vraag die bij al die elementen en isotopen bij mij naar boven kwam was: waar komen al die elementen toch vandaan? Hieronder een korte uitleg waar de elementen vandaan komen.

    CNO_Cycle

    fusie van helium en tritium naar koolstof, stikstof en zuurstof

    In het begin was er zoals bekend de Oerknal. Vlak na de oerknal waren er alleen simpele elementen zoals waterstof en helium, en in mindere mate beryllium, tritium, deuterium en lithium. Door de zwaartekracht concentreerden waterstof en helium zich en ontstonden sterren. Sterren verbranden in de eerste instantie de eerder genoemde elementen door middel van kernfusie. Hierbij onstaat stikstof en koolstof. Naarmate een ster ouder wordt zal deze steeds zwaardere elementen door kernfusie genereren, zoals neon, magnesium, silicium, zwavel, calcium en ijzer. Dit proces noemt men stellaire nucleosynthese. Continue reading  Post ID 3618


  • PMTs and scintillation probes

    quickprobe

    temporary probe with NaI(Tl) crystal, PMT, socket with voltage divider and BNC socket

    Following is a little guide to using photomultiplier tubes in DIY scintillation probes.

    Photomultipliers are vacuum tubes that convert light into electrons and multiply the resulting current up to millions of times. They are used to detect the minute flashes of light generated by scintillators, materials that convert gamma and x-rays into visible light.

    How to use these tubes? There are some things you need to remember when working with PMTs.

    Continue reading  Post ID 3618


  • Ludlum Model 2A 500K cpm mod

    ludlum500krange

     

    I recently bought a Ludlum Measurements model 2A survey meter on eBay from Obtanium. This is a nice meter which features the well known rugged Ludlum design, adjustable HV and 3 ranges of 500, 5000 and 50000 counts per minute.

    Using a scintillation probe the meter easily saturates on the 500 cpm scale, and the 5k and 50k ranges are also overloaded with certain sources.

    So I thought of adding a 500k cpm range. I already read the manuals and associated schematics to find out how to do this.

    Ludlum model 2 and 3 offer about the same functionality and basically share the same PCB, circuit, knobs and switches. Depending on age and model there are certain differences, but a lot of the stuff and functionality is the same. Continue reading  Post ID 3618