First Neutron Pulse from SNS

kebes writes "The $1.4 billion Spallation Neutron Source is nearing completion, and has produced its first neutron pulse. The SNS is a scientific instrument that generates beams of neutrons, which can be used to probe anything from minuscule samples to industrial materials. When fully operational, the facility is expected to host up to 2,000 international scientists annually."

Re:But, what does it do?

[blair1q]

5 (expanded): you can add neutrons to the nuclei of atoms to create heavier isotopes, which may then (in one of several decay scenarios*) split, as in fission

I.e., the most obviously valuable use of a high-density, high-energy neutron beam is studying heretofore under-investigated fission reactions and adding significant digits to heretofore over-investigated fission reactions. All this stuff about the "commercial benefits" is a cartoonish beard for A-bomb research.

* - the other common scenarios are alpha (helium-nucleus) emission resulting in a decrease of atomic number by 2 and mass number by 4, and beta (electron) emission resulting in an increase of atomic number by 1 and no change in mass number; i.e., we're talking alchemy here, kids.

Re:Can they aim this at.....

[spiro_killglance]

Actually, i forget the article, but a physicist did genunely suggest using a neutrino (not neutron) beam to cause enermy nuclear weopeans to melt down in there casings. It seemed reasonably practicle as well, it
would require a very high current particle accelerator to produce a very narrow ultra relavistic pion or
muon beam. At these high speed the neutrino decay products of pions would still be very tightly directioned. They could pass straight through the earth, and cause sufficient stimulated fission reactions in remote nuclear materal to cause it to gently (as opposite to explosively) melt down.

Pyroelectric Fusion as Neutron Source?

[Aelcyx]

Anyone remember UCLA doing a form of cold fusion using pyroelectric crystals? It did not release enough energy to make it efficient as an energy source, but I recall the article saying it would make a portable neutron source. Perhaps that could be used to make a smaller and more efficient version of the Oak Ridge facility.

Re:How do they make a pulsed neutron beam?

[CaryTheSane]

IANAPP (I am not a Particle Physicist) but I *DO* work at the SNS site. I'm a software engineer in their Beam Diagnostics group, and was in the contorol room on Friday when we met this milestone. My basic understanding is that here we use our Linac to accelerate protons (H-). A minipuse sent down the linac is approx 700 ns long. They first go into an accumulator ring, and are "stacked" to increase the intensity of the pulse to target. On Friday we accumulated for around 180 pulses, design specs are for around 1000. Finally the the pulse is extracted from the ring and hits a target vessel filled with mercury. Again, IANAPP, but my understanding is that this intense pulse of protons only 700 ns long, hits the mecury, and "spalls" neutrons from the mercury atoms. Then as others have mentioned the neutrons are columnated and fly down different beam lines to be used in different refraction experiments (or they will be once this source is fully operational ;-) . Bottom line is that the particles that we acclerate are not the ones that contribute neutrons. Once more, IANAPP, but it helps me to think of it as we're accelerating cue balls, and hitting a (3D) rack of billard balls.

Re:Pyroelectric Fusion as Neutron Source?

[SlashSquatch]

Yep. The pyroelectric crystal can produce about 1000 neutrons per second. This spallation accelerator produces 1.5e10^14 protons per pulse. Each proton should generate 20-30 neutrons. Evidently this source is supposed to be brighter. If I estimate correctly, brighter by an order of 10^10 times.