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| David Bass 2002-11-06 13:57:11 | Not high on technical detail, and completely fails to mention this distributed effort, but it may be of interest nevertheless. News Item |
| Ben Whitten 2002-11-06 14:38:56 | Wow I generaly havn't seen neutron machine pics but that Isis look like a right formidable monster of a machine  I like alot, well now I know when I'm helpin on I tink I'll have the comp on overtime |
| Stephen Brooks 2002-11-07 05:54:48 | quote: The bit in the picture is about 4m of the beam pipe - you can see it's curved, and it's in fact part of a ring of something like 60m circumference. That in turn has one linear accelerator feeding into it and a focussing channel leaving the ring, going off to hit the target. The big sphere thing is a _neutrino_ detector, not a _neutron_ accelerator, in case you got the two confused. "As every 11-year-old kid knows, if you concentrate enough Van-der-Graff generators and expensive special effects in one place, you create a spiral space-time whirly thing, AND an interesting plotline" |
| Tom King 2002-11-07 07:06:08 | How DO you accelerate neutrons anyway? |
| Stephen Brooks 2002-11-07 07:07:27 | Oh errr. I should have said it accelerates protons and then they hit the target and become neutrons. "As every 11-year-old kid knows, if you concentrate enough Van-der-Graff generators and expensive special effects in one place, you create a spiral space-time whirly thing, AND an interesting plotline" |
| Tom King 2002-11-07 07:26:33 | Er-Er-Er. So what's the target made out of, and why does it give out neutrons err neutrons when hit by protons? And also, won't an awful lot of neutrons given off be wasted becasue they'll be shooting out at any old angle? |
| Stephen Brooks 2002-11-07 13:22:57 | It used to be made of Uranium. (Yes I know, I thought that too). But now it's made of Tantalum or Palladium or some dull metal like that. They do all shoot out at odd angles - quite a few must be lost, but there are a load of refocussing channels coming off the target chamber at all different angles. "As every 11-year-old kid knows, if you concentrate enough Van-der-Graff generators and expensive special effects in one place, you create a spiral space-time whirly thing, AND an interesting plotline" |
| Midon 2002-11-09 07:51:10 | From this point the target material is not important. Every target will be high radioactive afer using it in the accelerator. You can try to choose materials which will produce only radioisotopes which has a short lifetime. You have to take care about many things. The target needs to be cooled because the beam will heat it up. For this reason a metall is a good choice. And you have to take care about the Neutrons which are produced, you need a moderator, ... |
| Stephen Brooks 2002-11-09 09:00:53 | The target certainly gets hot - I seem to remember the ISIS proton beam has a power of 160kW. Then when the target is sufficiently degraded it gets shipped off in a lorry to Sellfield and they get a new one. I'm not sure if the ISIS target is actively cooled. A few alternate suggestions for the neutrino factory target (the rod at the beginning of the Muon1 simulation) have been suggested - one is a liquid mercury jet target that gets vapourised by the incoming beak; another is a magnetically-levitating ring of metal that spins so that each part gets a turn at being hit by the beam and has time to cool off on the way around. If I get pion-emission data for these new sources I can simulate the effect of them too (v5+). "As every 11-year-old kid knows, if you concentrate enough Van-der-Graff generators and expensive special effects in one place, you create a spiral space-time whirly thing, AND an interesting plotline" |
| Midon 2002-11-09 10:01:46 | I found the answer for a future machine at http://www.isis.rl.ac.uk/accelerator/MuonMachine/BeamHeating/General.html. The target needs to be cooled. Only if you use a large ring only radiation cooling can be used. The material will get a peak temperature of 2400 K  . Tantal is melting a little bit over 3000 K. |
| taz 2002-11-12 14:17:25 | I still don't understand the need for Malaysian cars in all of this, except that they are cheap? |
