evans@mhuxt.UUCP (07/08/83)
The news note on the upgrade at FNAL reminds me that there are several other interesting proposals for large machines in the US (I'll ignore LEP at CERN -it is a monster e+e- machine). The Tevatron beat ISA- BELLE at Brookhaven National Labs to the punch largely due to delays caused by designing state of the art 60 kgauss superconducting magnets at BNL. As a result the BNL machine consists of a large tunnel on Long Island. Several rescue schemes have been proposed and HEPAP (High-Energy Physics Advisory Panel) meet last month at Woods Hole to consider the options. One of the options would be to upgrade ISABELLE into something called the CBA (Colliding Beam Accelerator) which is a 800 GeV on 800 GeV proton machine. This is considerably more than the 400 GeV on 400 GeV planned for ISABELLE, but less than the energy available at the Tevatron. The advantage of this machine is luminosity (basically a density of particles available in the collision regions) -- it is many orders of magnitude higher than the Tevatron allowing searches for very rare interactions. The other possibility being considered by HEPAP is more dramatic. The idea is to leapfrog all existing machines and go to very high energies - 40 TeV center of mass!!! This project requires a very large acceleration ring and would probably be built in a desert giving it the name "Desertron." If one was to use cheap iron magnets (30 kgauss), one requires a 240 km/dia acceleration ring. With 50 kgauss superconducting magnets (current state of the art), the diameter drops to 125 km. If one can develop 100 kgauss magnets you are left with something about 70 km/dia. Proposed sites include deserts near Alburquerque, Kitt Peak, Salt Lake City, and Austin. People are talking about development costs of $2 - 3 x 10^9. Physicists being reasonably clever people have even come up with a bizarre funding scheme. De Rujula, Charpak, Glashow, and Wilson (kind of a who's who of HE theory and experimental types) wrote a paper titled "Neutrino Exploration of the Earth". It turns out that the probability of a neutrino interacting with ordinary matter goes linerally with the energy of the neutrino. At 10 TeV the mean interaction length is roughly the diameter of the Earth. Hmmmm.... why not Whole Earth Tomography? You build a 20 TeV accelerator and divert the fast protons to a target. After the collisions you colminate a fast muon beam and let it decay in a long vacuum tube. Now you have your neutrino beam. Simply point it down (gasp!) and look through the Earth. Since the mean interaction length is roughly the diameter of the Earth, you should be able to "easily" deduce variations in the Earth's density and composition. The problem here is that the beam extractor/target/muon decay tube (called the "snout") must be several km long, making it difficult to aim straight down. The proposal says that the accelerator would probably have to be built at sea, with the snout anchored on an atoll in very deep water. So far none of the oil companies are interested in the GEOTRON, but Saudia Arabia has been making inquiries. The above schemes are conventional in that they use synchrotrons. Some people are investigating accelerating particles using the intense fields found in a laser beam (inverse free electron lasers) near a diffraction grating. Steve Crandall mhuxt!evans #
mat@hou5e.UUCP (07/13/83)
>From a recent article:
The above schemes are conventional in that they use synchrotrons. Some
people are investigating accelerating particles using the intense fields
found in a laser beam (inverse free electron lasers) near a diffraction
grating.
I don't think that many of us know what this is all about (I could be wrong.)
Could the author elaborate on the principles involved?
hou5e!mat
Mark Terribile