MadExp PMT adapter

UPDATE 18 Feb. 2018
I've analyzed my home radioactive background simply leaving the MadExp PMT connected and running for 100 minutes on the table top. The result is this:


UPDATE 10 Feb. 2018
I've completed my first example of MadExp PMT adapter and it's NaI(Ti) probe. I'm making some test with it. Three audio samples was recorded with it and are listed below.
This one is my location gamma backround
This is an Am241 alpha emitter capsule from smoke detector
This is the sound of an highly active (15mSievert/h) Pechblende uranium ore

In this video you can see my first PMT test.

How to power and aquire signal of a scintillation probe?

You I need some high voltage and signal conditioning circuit! Inspired by the Theremino PMT project, I’ve decided to build my own customized version of their circuit. http://www.theremino.com/blog/gamma-spectrometry

My project goal is to make an all-in-one photomultiplier tube power supply and audio ADC powered by a single USB cable. The high voltage generator is regulable in the range 700-1500V with a simple trimmer.

Corrent status of the project:

  • Schematic at version 2 (erros corrected)
  • PCB routing ready
  • First batch of PCB’s arrived from chinese manufacturer
  • First complete prototype ready and working
Schematic V2.0

To enlarge the schematic right click on the image and select “Show Image” or download it and zoom with your image viewer.

In order to make the CM108AH working you absolutely need to add the 47 ohm series resistors on USB D+ and D- data lines with a pull-up resistor of 1.5K from the ic’s 3,3V out to D+. I’ve lost a lot of time to understand this simple thing… but not so obvious!

This is the PCB board top layer

With my CNC engraver I’ve made some engravings to the PMT adapter enclousure… as a first test I’ve messed with the cutting deep/speed.

The video below is my first test of the circuit

First test connecting the adapter to my pc soundcard. The program is Theremino MCA, is not calibrated… I need to set each control of the MCA at the right position so I need some time for setting up it.

Testing a camera lens containing thorium
Testing a natural Pichblende sample from a mine situated in northen Italy.

6 thoughts on “MadExp PMT adapter”

  1. Greetings! This is my first comment here so I just wanted
    to give a quick shout out and tell you I genuinely
    enjoy reading through your posts. Can you suggest any other blogs/websites/forums that
    cover the same topics? Many thanks!

  2. This design is spectacular! You obviously know how
    to keep a reader amused. Between your wit and your videos,
    I was almost moved to start my own blog (well, almost…HaHa!) Fantastic job.
    I really loved what you had to say, and more than that,
    how you presented it. Too cool!

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