Date: May 17, 2007
Time: 4:00 pm - 5:30 pm

SLAC Accelerator Seminar

Speaker: Rolland Johnson, Muons, Inc.

Thursday, May 17, 2007

4:00 P.M.

Yellow Room

Abstract: A six-dimensional (6D) ionization cooling channel based on helical magnets surrounding RF cavities filled with dense hydrogen gas is the basis for the latest plans for muon colliders. This helical cooling channel (HCC) has solenoidal, helical dipole, and helical quadrupole magnetic fields, where emittance exchange is achieved by using a continuous homogeneous absorber. Momentum-dependent path length differences in the dense hydrogren energy absorber provide the required correlation between momentum and ionization loss to accomplish longitudinal cooling. Recent studies of an 800 MHz RF cavity pressurized with hydrogen, as would be used in this application, show that the maximum gradient is not limited by a large external magnetic field, unlike vacuum cavities. Two new cooling ideas, Parametric-resonance Ionization Cooling and Reverse Emittance Exchange, will be employed to further reduce transverse emittances to a few mm-mr, which allows high luminosity with fewer muons than previously imagined. We describe these new ideas as well as a new precooling idea based on a HCC with z dependent fields that is being developed for an exceptional 6D cooling demonstration experiment. Present concepts for a 1.5 to 4 TeV center of mass collider with average luminosity greater than 10 34/s-cm2 include ILC RF structures to accelerate positive and negative muons in a 10-pass recirculating Linac. The status of the designs, simulations, and tests of the cooling components for a high luminosity, low emittance muon collider will be reviewed.