Neutron detector build
Posted: Tue Mar 19, 2019 11:10 pm
This is a neutron detector experiment, a build using a USSR-made SNM-11 boron-10 corona tube.
Here the tube is slid into the moderator and the PCB sits just outside.
The tube can easily be slid off for the all-important "moderator on vs. moderator off" test.
Here is the exposed assembly before sliding into the moderator.
3M copper foil tape with conductive adhesive is used to make the contact onto the tube.
Here is detail of the PCB.
This is the starting HDPE stock.
The HDPE is 90mm OD, which is a little thin for complete thermalisation of neutrons, but this is the material that I had available easily at a reasonable price. It should be good for producing epithermalisation of neutrons, maybe for activation experiments one day.
The HDPE rod is cut to 350mm length (slightly longer than the SNM-11) and drilled to 20mm down the centre.
This is the amplifier schematic, using a single BJT (MMBT3904 in this case.) R2 is changed to 68k, the output bias R5/R6 are not populated,
R1 is 330k, R3 is 5.6k. (I changed these slightly from the drawing to suit the components on hand.)
The bias tee section consists of a 100pF HV ceramic, a 47M HV resistor and an SHV connector fed from a 0-5kV adjustable (low current) power supply module. I haven't installed the 16k resistor yet.
Here the tube is slid into the moderator and the PCB sits just outside.
The tube can easily be slid off for the all-important "moderator on vs. moderator off" test.
Here is the exposed assembly before sliding into the moderator.
3M copper foil tape with conductive adhesive is used to make the contact onto the tube.
Here is detail of the PCB.
This is the starting HDPE stock.
The HDPE is 90mm OD, which is a little thin for complete thermalisation of neutrons, but this is the material that I had available easily at a reasonable price. It should be good for producing epithermalisation of neutrons, maybe for activation experiments one day.
The HDPE rod is cut to 350mm length (slightly longer than the SNM-11) and drilled to 20mm down the centre.
This is the amplifier schematic, using a single BJT (MMBT3904 in this case.) R2 is changed to 68k, the output bias R5/R6 are not populated,
R1 is 330k, R3 is 5.6k. (I changed these slightly from the drawing to suit the components on hand.)
The bias tee section consists of a 100pF HV ceramic, a 47M HV resistor and an SHV connector fed from a 0-5kV adjustable (low current) power supply module. I haven't installed the 16k resistor yet.