From: heathjohn2@gmail.com   
      
   On Thursday, October 12, 2017 at 5:36:47 PM UTC-4, Tom Roberts wrote:   
   > On 10/11/17 6:46 PM, John Heath wrote:   
   > > At Fermilab they needs to focus a beam of anti protons. [done with a   
   lithium   
   > > lens ...] How can an anti proton make it through 4 inches of solid lithium   
   > > without hitting a proton ?   
   >   
   > More than 90% of the anti-protons get through the Li lens with only multiple   
   > scattering, and the focusing is much stronger than the multiple scattering.   
   As   
   > the moderator said, "solid" lithium is mostly intra-atomic space as the   
   > anti-protons see it.   
   >   
   > > The anti proton negative charge only increases the chances of a proton hit.   
   >   
   > These are 8 GeV anti-protons, and their negative charge has only a tiny   
   effect   
   > on the cross-section to interact with a nucleus [#]. At 8 GeV the total   
   > cross-sections for protons and anti-protons differ by about 1% with an   
   errorbar   
   > that is larger than the difference.   
   >   
   > 	[#] You are probably thinking that the negative anti-proton will   
   > 	be attracted to the positive Li nucleus, and thus be deflected   
   > 	to hit it more often than a positive proton (which would be   
   > 	repelled). In fact, these 8 GeV anti-protons are so stiff it is   
   > 	easier to move the nucleus than deflect the track, and that is   
   > 	quite small because the anti-proton track is near each nucleus   
   > 	for such a short time that there is essentially no time for the   
   > 	EM force to accelerate it closer to the track. (This is a rather   
   > 	loose, classical description.)   
   >   
   > Tom Roberts   
      
   Hmmm interesting. 90 percent make it to the end. At 8 GeV the mass   
   is ballpark 10 times normal. It should be scooting along at a good   
   .99c . I can see why a Coulomb force is not that relevant at these   
   speeds. I was wondering how much of a problem lithium temperature   
   is with 500 k amps going through it plus a few annihilation here   
   and there? Lithium is not the best conductor , probably .01 to .1   
   m ohm for a tube that size. From what you know is keeping the lithium   
   tube from over heating critical or well under control?   
      
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