Comment Christmas tree (Score 1) 267
So long as there's a christmas tree, it doesn't matter.
(You know, the whole 31_Oct = 25_Dec thing)
So long as there's a christmas tree, it doesn't matter.
(You know, the whole 31_Oct = 25_Dec thing)
Just because I feel like it... I think you mean any positive altitude is valid. And given the type of plane, probably not in space either.
But yeah, I know what you mean
Fusion creates incredibly high energy neutrons, which are unaffected by the magnetic field, that pass through the plasma, heating it slightly, and leave the plasma.
The solution is (as many have said here already) to create a blanket of lithium around the device, and for the neutrons to pass into* the blanket, collide with the lithium, and cool down. This heats the lithium as well as breeding tritium fuel. The heat in the blanket is passed to create steam at a heat exchanger, steam powers turbine... electricity.
*creating the steel to hold the blanket in place without it becoming too damaged by the neutrons is also tricky.
If they can do what they can currently do once (last I checked) per day 100 times per second, yes. Its research is interesting plasma physics, interesting laser physics, and transferable in many cases to other fields - but an electricity generator NIF is not.
It does do a very good job of nuclear weapons research given a ban on testing though.
I think fusion reactors scale somewhere like r^4 in terms of Q value. As size increases, confinement time increases, and given the temperature and pressure gradients that can be sustained, the core temperature and pressure can increase.
I can't prove that it's r^4, but I'm sure I remember it being approximately r^4 or maybe r^3 (or somewhere between the 2).
With regards D-D/D-T, when tokamaks such as JET, MAST, ITER and the like run with deuterium, their aim isn't to allow fusion. So a typical deuterium Q value would be 0 or very close to 0.
The reason is that getting deuterium and tritium to fuse isn't the difficulty - so it's not something they have much need to practise. Working in a purely deuterium mode provides the same plasma physics challenges - but without the added difficulty of using tritium (for example, once a tokamak has had tritium in it, human access to the machine is very strictly limited).
With all that's learnt using deuterium and tritium, if a machine such as JET goes for a D-T campaign as it did in 1997, and another campaign was considered recently, then it gives a data point to show performance, proves that progress has been made, and may be useful if they were interested in studying ash (helium) in the plasma.
Studying effects of neutrons is usually done elsewhere - leaving a sample in a source of neutrons for long periods of time (such as in a fission reactor), although a Component Testing Facility is planned in the longer term to expose components to high energy neutrons (14MeV is much higher energy than neutrons in fission).
So not a huge amount is to be gained by running D-T regularly.
Never test for an error condition you don't know how to handle. -- Steinbach