Sonofusion detector

[Richard Hull]

I have studied the Sonofusion paper a bit now and it appears that these folks used a common plastic scintillator and PMT. They used a secondary liquid scintillator as a Gamma discriminator utilizing pulse width differences and coincidence detection to decide which of the plastic scintillator pulses was a real neutron. They claim an absolute, neutron counting efficiency of 5x10e-3. This is just great! Old posts will show that the venerable BC-720 by Bicron is rated as having and efficiency of 0.6% or (6x10e-3), which is damned close to what these guys were using. More nice confirmation of technique used by myself and others in those early days of real fusor fusing (2000).

For those working up their own BC-720 "work-alike" (Jon and Tom)it looks good. For those hoping to use a plain scintillator, it looks like some fancy foot work will need to be done to separate the gamma from the neuts inorder to obtain reliable results. (I also noted this a while back.)

The gamma background in such plain scintillators is relatively high and would have to be weeded out. Plus, any x-rays, (fusors make a lot of 'em) would be definitely counted in such a scintillator.

The paper also has a nice timing diagram to show how they were not deceived due to identifiable noise sources in time. The pulsed neutron source definitely triggers the counter not ony from neutrons, but from the large high energy electrical pulse creating a large EM wave. The neutron induced nucleation, the bubble growth and ultimate collapse are separated in time by about 27 microseconds. The Sonofusion nuets are more or less coincident with the SL light pulse.

One extra control that I would like to see is a small HF dipole hooked up to a fast digital o'scope to see if an EMP was also coincident with the light flash. After all, it is a miniature fusion blast that they are claiming and during such events, EMP is classically attendant. But, maybe not in this sonofusion situation. Still, it would be a good additional control. Any significant EMP coincident with neutron detection would make the neutron detection, itself, suspect.

Their absolute best control was the same as used by myself, then Scott Little and, finally, by Joe Zambelli........run the device with similar modus operandi minus the D2. All of us recorded zero neutrons at full power. These folks used pure acetone and, also, recorded zip.

There is no such thing as too much care in making neutron measurements. After you are sure you are recording only neutrons, run the null test as above.

Richard Hull

[Richard Hester]

The rebuttal paper to the one that slammed the sonofusion results is very valuable for the insights offered into neutrom metrology, down to the optimum volume of scintillator plastic for detection of 2.5 Mev neutrons. Also valuable is the discussion of discriminator setting for optimum detection of neutrons of a given energy. You don't often get nitty-gritty details like that spelled out...

[Richard Hull]

Yes, I must agree that those original authors had done a decent job of doing their homework on neutron detection. I would love to chat with both groups on the exact manner of neutron measurement and see it happening in real time. You would think that the replication attempt by the two ORNL annointed ones, would certainly have superlative neutron measurment techniques brought to bear. First, because it is an atomic laboratory and things like neutron measurement should be second nature. Second, If they are going into the experiment looking for errors, you would think their instrumentation would be tight. If the rebuttal paper to theORNL replication attempt is correct, it looks just the opposite!

Richard Hull

[Richard Hull]

It seems that the rebuttal paper by the original authors to the "failure to replicate" paper by the Oak Ridge appointees says the the replication experiment DID find all the neutrons they should have!!

This is based on the rebuttal/original authors saying that the stated efficiency of the neutron detector used by the "failure to replicate" team was off by two orders of magnitude!!!

This is a rather bold and tremendous statement. Again, I must point out that regardless of what you are counting or how slow the counts come, the effcieincy of the instrument (neutron detector) is THE KEY SALIENT POINT!

For one researcher to claim to know the efficiency of another researcher's instrument better than he does is like a slap in the face, whether it is true or not.

The fur will continue to fly.......

Richard Hull