Cooling hadron, ion and muon beams

5 problems

• Experimental demonstration of coherent electron cooling of hadrons

  Open

  In coherent electron cooling each ion imprints a density ripple on a co-moving electron beam, the ripple is amplified, and it then pushes the ion back toward the ideal energy; this has not yet been seen to cool a beam.

• Three-dimensional crystalline beams in a storage ring

  Open

  Cooled enough, a circulating ion beam should freeze into an ordered crystal moving as one; real rings have shown only ions lined up in a single file.

• Cooling time reachable for 275 GeV protons by microbunched electron cooling

  Open

  An electron-ion collider needs to cool its high-energy proton beam faster than collisions inside the bunch heat it; whether coherent cooling can do this is unsettled.

• Reaching muon collider target emittances by ionization cooling

  Open

  Muons must be squeezed in phase space by a factor of about a million within microseconds, by passing them through absorbers and re-accelerating them; the full chain has never been built.

• Optical stochastic cooling of hadron beams at collider energies

  Open

  Optical stochastic cooling, first shown with electrons in a small ring, uses light pulses emitted by each particle to correct that particle's motion; it is unproven for heavy high-energy beams.