FAQ - Surplus portable neutron detectors
Posted: Tue Jul 10, 2012 10:28 am
Many are in search of neutron detectors. Once common on e-bay, the units have been gobbled up to such a degree that they are very rare now. The most common to find are the old Eberline units with the PNC-1 leading the pack. On rare occasions, a rem ball, (Bonner sphere), with a mated PNR-4 will be encountered.
In most all instances, the seller will have no idea as to whether the thing works or not and admits it, saying "All sales final". In spite of this warning, prices usually climb quickly to far more than such a "pig in a poke" is worth. Such seems to be the desire to possess neutron counters. I often wonder if this "frenzy" is fusioneer driven since prior to the fusion effort, such items were often encountered and sold rather inexpensively. Most of this ended by 2006.
Speaking from experience and having purchased several of these since 1999, if they are surplus they are probably dead unless the seller warrants a fully functional unit.
Common issues are grossly corroded battery case, failed HV supply, or defective tunnel diode, (PNC-1, irreplacable). The PNR-4 has a special log-log dual movement meter and is often defective or damaged. (I have two of these that are parts-only units.)
Victoreen and later, Nuclear Associates, made the large black moderator "snoopy" style counters. These are also found at a functional level of only ~20%.
Most all survey type portable counters require a strong neutron field to push their needles up scale, if all is in good order. The tubes are typically a rather tiny Nancy Woods BF3 tube and the resultant sensitivity is low even with the counter in contact with typical amateur level sources.
The best use for these counters is with their audio outputs being be fed to a digital counter where good data over longer periods of time can be collected and recorded.
Using one of the above, a decent count rate can be obtained at about 150,000 neutrons per second. (isotropic). Valuable data counting can begin at about 50,000 n/s with easy detection at about 10,000 n/s. This last figure is about where the amateur will first start to fuse unless he is very lucky, indeed. As skills and fusor conditioning improves the amateur can only then really see much benefit in the survey meter type neutron detector.
Of all the old meters to have, the PNC-1 is probably the most useful if in good order. It allows for close contact with the fusor or source and is nicely portable and uses common D cells. I have one that had the battery holder and compartment ruined and have wired two leads coming out to go to a simple bench supply instead of batteries.
A rem ball, by itself, can be very useful if the tube is good. Good electronics for the Bonner Sphere can be assembled either from standard NIM components or, better still, modern electronics cobbled up by adroit hands using some of Richard Hester's excellent circuits posted in these forums.
Any of these items offered on e-bay or surplus need to be looked at with a jaundiced eyed. In unknown condition, a PNC-1, if complete, is worth about $200.00 max
If warranted with a money back agreement and stated to be working and tested, then $400.00 - $1,000 would be acceptable.
A naked, (no detector) PNR-4 is not worth $100.00. However if it is with a remball and is functionally warranted, then $1000.00 would be a modern normal maximum. A naked remball that has the tube in it and is warranted is worth at least $400.00 or more.
A Snoopy, if warranted, is worth $500.00 to $800.00 if unwarranted and complete it might be worth $200.00-$400.00.
Extremely old portable neutron counters should never be considered as they are often vacuum tube based and use batteries that can no longer be purchased or use some sort of scintillation detection that is very low in efficiency. Such older units were made for very high neutron flux fields. These are of curio-antique value only.
Finally, you may see tiny modern electronic handheld counters that tout that they can detect neutorns. Well, Maybe, but they are not worth the time to consider as they will only detect large neutron field levels as well.
Be advised that many of the above mentioned and recommended Eberline units have sold in the distant past for far less than the above quoted figures and could be sold in future for less, as well. However, many insane bids have been placed that have pushed even un-warranted items into ridiculousville! Buyer beware.
Often, the best overall solution and obtained at the lowest cost, is to purchase a good neutron detector tube, (still can be costly), and build or assemble your own moderator and electronics. (what I did with fusor IV) But, this FAQ was about surplus, all-in-one counters and I will leave it here.
Richard Hull
In most all instances, the seller will have no idea as to whether the thing works or not and admits it, saying "All sales final". In spite of this warning, prices usually climb quickly to far more than such a "pig in a poke" is worth. Such seems to be the desire to possess neutron counters. I often wonder if this "frenzy" is fusioneer driven since prior to the fusion effort, such items were often encountered and sold rather inexpensively. Most of this ended by 2006.
Speaking from experience and having purchased several of these since 1999, if they are surplus they are probably dead unless the seller warrants a fully functional unit.
Common issues are grossly corroded battery case, failed HV supply, or defective tunnel diode, (PNC-1, irreplacable). The PNR-4 has a special log-log dual movement meter and is often defective or damaged. (I have two of these that are parts-only units.)
Victoreen and later, Nuclear Associates, made the large black moderator "snoopy" style counters. These are also found at a functional level of only ~20%.
Most all survey type portable counters require a strong neutron field to push their needles up scale, if all is in good order. The tubes are typically a rather tiny Nancy Woods BF3 tube and the resultant sensitivity is low even with the counter in contact with typical amateur level sources.
The best use for these counters is with their audio outputs being be fed to a digital counter where good data over longer periods of time can be collected and recorded.
Using one of the above, a decent count rate can be obtained at about 150,000 neutrons per second. (isotropic). Valuable data counting can begin at about 50,000 n/s with easy detection at about 10,000 n/s. This last figure is about where the amateur will first start to fuse unless he is very lucky, indeed. As skills and fusor conditioning improves the amateur can only then really see much benefit in the survey meter type neutron detector.
Of all the old meters to have, the PNC-1 is probably the most useful if in good order. It allows for close contact with the fusor or source and is nicely portable and uses common D cells. I have one that had the battery holder and compartment ruined and have wired two leads coming out to go to a simple bench supply instead of batteries.
A rem ball, by itself, can be very useful if the tube is good. Good electronics for the Bonner Sphere can be assembled either from standard NIM components or, better still, modern electronics cobbled up by adroit hands using some of Richard Hester's excellent circuits posted in these forums.
Any of these items offered on e-bay or surplus need to be looked at with a jaundiced eyed. In unknown condition, a PNC-1, if complete, is worth about $200.00 max
If warranted with a money back agreement and stated to be working and tested, then $400.00 - $1,000 would be acceptable.
A naked, (no detector) PNR-4 is not worth $100.00. However if it is with a remball and is functionally warranted, then $1000.00 would be a modern normal maximum. A naked remball that has the tube in it and is warranted is worth at least $400.00 or more.
A Snoopy, if warranted, is worth $500.00 to $800.00 if unwarranted and complete it might be worth $200.00-$400.00.
Extremely old portable neutron counters should never be considered as they are often vacuum tube based and use batteries that can no longer be purchased or use some sort of scintillation detection that is very low in efficiency. Such older units were made for very high neutron flux fields. These are of curio-antique value only.
Finally, you may see tiny modern electronic handheld counters that tout that they can detect neutorns. Well, Maybe, but they are not worth the time to consider as they will only detect large neutron field levels as well.
Be advised that many of the above mentioned and recommended Eberline units have sold in the distant past for far less than the above quoted figures and could be sold in future for less, as well. However, many insane bids have been placed that have pushed even un-warranted items into ridiculousville! Buyer beware.
Often, the best overall solution and obtained at the lowest cost, is to purchase a good neutron detector tube, (still can be costly), and build or assemble your own moderator and electronics. (what I did with fusor IV) But, this FAQ was about surplus, all-in-one counters and I will leave it here.
Richard Hull