DIY scintillation probe: alluminium enclosures

How to make a scintillation probe with aluminium enclosure? Is not that hard if you have a lathe, a mill and a drill. I start assembling the scintillation crystal with the photomultiplier and measuring them. From standard aluminium pipe size, I choose one for the body and one, as reducer, to fit the scintillator inside the body pipe. From an alluminium round bar I made the ened cap.

Body pipe and crystal adapter. It fits inside the body and have a center hole where I put the crystal
This pic is from another probe… as you can see is easy to scale up my design. In this case the aluminium adapter fits a 36mm crystal into a 40mm pipe

Black silicon assembly
How the crystal + adapter fits the pipe

The crystal adapter is a piece of pipe shaped to fit inside the body pipe and have an inner hole where I put the crystal and photomultiplier. I use silicon black glue to gle everything together. It is strong but can be removed easily if I need to re-open the assembly.

Photomultiplier, crystal and front adapter
Silicon grease that will couple the crystal to the PMT front window

 

To assemble the PMT+crystal I’m using an optical coupling grease.

Coupling
Blocking the assembly with some black electrical tape
Fixing crystal + PMT inside the adapter with black silicon glue

After silicon glue hardened I assemble the voltage divider board to the photomultiplier wires. The divider board is home made etching it’s circuit on a piece of FR4 or bakelite copper clad board.

Front assembly

 

Voltage divider added

 

Bakelite voltage divider board

Now that everything is ready, I close the probe adding the end-cap and soldering the voltage divider + and – at the BNC female connector on the ending cap.

Ending cap inner view
Ending cap BNC connector

Usually I anodize my alluminium parts. Using different kind of alluminium alloys for different probe parts results in different color of the anodized surface.

Hi-Zinc content into the alluminium alloy makes it darker than standard aluminium

And this is the final result

Author: l.i.papadopol