Assembly of a He-3 Tube/System
Posted: Fri Nov 10, 2017 9:49 am
After reading a number of excellent posts on the recent successes of various neutron detectors, it is time I got back and started building &/or assemble the ones I have on hand (and get my fusor running again.) The easiest would be my He-3 tube since I have a counter/display/power supply consule (the ST-360) to run it. Just a matter of assembly of wiring/connectors to the He-3 tube. And thanks again for that information on proper voltage, Silviu!
In that regards, I have found that the Russian tubes (both the Boron gas based as well as the He-3 ones) electrical end connectors are the exact size to mate/connect with american standard copper tube compression fittings (see first picture. The fittings for 1/4" or 6 mm OD tubing.) I have a metal screw that easily fits inside the compression fitting core and makes tight contact with the He-3 detector pin. I then used a std bolt/wire connector on that nut/bolt assembly.
Aside: That exposed assembly will have silicon sealant covering to protect that assembly on the tube even though the HV is low enough that that shouldn't really be an issue.
I have the nearly finished He-3 neutron detector (see following picture) - all that remains is to install/seal the tube into the RF shielded case.
The ST-360 (recently and successfully repaired - thanks everyone here for that critical help!) is also shown.
The other end of the HV lead is my end cap (brass) with the coaxial HV connector connector attached. This end cap will be silver epoxied (conductive) to the copper tube. In this manner the entire system is RF tight and easy to handle.
Here is the finished He-3 detector assembly fully assembled and sealed - see picture below.
Note: the copper foil tape on edges of the assembly offers little RF protection; the Ag epoxy and metal components provides the major shielding factor. The center "pin" for the coaxial reads "open" relative to the shielding (as it better had); all shield sections read 0.3 ohms or less relative to each other (again, must or there is a bad connection somewhere.) I used some crumpled aluminum foil to fill the lower section of the copper case to keep the He-3 tube in good contact with the shield. The HV wires, "wrapped around inside the tube hold the other side of the detector firmly in place.
Before I fire up my fusor for neutrons, I will need to clean my fusor window (my electrode feed's thru it. ) Also, I intend to add a wire mess cylinder in the main fusor body/chamber so I have both a larger area and more uniform anode/ground for my cathode cage; this, I would think, will make my plasma more uniform. Hopefully, this improves my fusor's neutron output or lowers my require power for a similar performance.
Currently, I have only one copper tube (this is special thick walled; I got it surplus) so my large boron gas detector had to be removed. I will get that back in operation in a few weeks (yes, Silviu, likely will just use regular copper tubing as you suggest) if all goes well with the He-3 detector. I also have a solid boron detector wired and ready so, if the He-3 detector works, I might try that one as well.
My final major detector project is to assemble my scintillation neutron detector - that will be my last effort/project relative to detectors.
In that regards, I have found that the Russian tubes (both the Boron gas based as well as the He-3 ones) electrical end connectors are the exact size to mate/connect with american standard copper tube compression fittings (see first picture. The fittings for 1/4" or 6 mm OD tubing.) I have a metal screw that easily fits inside the compression fitting core and makes tight contact with the He-3 detector pin. I then used a std bolt/wire connector on that nut/bolt assembly.
Aside: That exposed assembly will have silicon sealant covering to protect that assembly on the tube even though the HV is low enough that that shouldn't really be an issue.
I have the nearly finished He-3 neutron detector (see following picture) - all that remains is to install/seal the tube into the RF shielded case.
The ST-360 (recently and successfully repaired - thanks everyone here for that critical help!) is also shown.
The other end of the HV lead is my end cap (brass) with the coaxial HV connector connector attached. This end cap will be silver epoxied (conductive) to the copper tube. In this manner the entire system is RF tight and easy to handle.
Here is the finished He-3 detector assembly fully assembled and sealed - see picture below.
Note: the copper foil tape on edges of the assembly offers little RF protection; the Ag epoxy and metal components provides the major shielding factor. The center "pin" for the coaxial reads "open" relative to the shielding (as it better had); all shield sections read 0.3 ohms or less relative to each other (again, must or there is a bad connection somewhere.) I used some crumpled aluminum foil to fill the lower section of the copper case to keep the He-3 tube in good contact with the shield. The HV wires, "wrapped around inside the tube hold the other side of the detector firmly in place.
Before I fire up my fusor for neutrons, I will need to clean my fusor window (my electrode feed's thru it. ) Also, I intend to add a wire mess cylinder in the main fusor body/chamber so I have both a larger area and more uniform anode/ground for my cathode cage; this, I would think, will make my plasma more uniform. Hopefully, this improves my fusor's neutron output or lowers my require power for a similar performance.
Currently, I have only one copper tube (this is special thick walled; I got it surplus) so my large boron gas detector had to be removed. I will get that back in operation in a few weeks (yes, Silviu, likely will just use regular copper tubing as you suggest) if all goes well with the He-3 detector. I also have a solid boron detector wired and ready so, if the He-3 detector works, I might try that one as well.
My final major detector project is to assemble my scintillation neutron detector - that will be my last effort/project relative to detectors.