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A.Aleksandrov (Oak Ridge National Laboratory, USA)

Spallation Neutron Source Project: Commissioning Results, First Operation Experience, and Upgrade Plans

The Spallation Neutron Source accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H- injector, capable of producing one-ms-long pulses at 60Hz repetition rate with 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The 2.5MeV beam from the Front End is accelerated to 86 MeV in the Drift Tube Linac, then to 185 MeV in a Coupled-Cavity Linac and finally to 1 GeV in the Superconducting Linac. With the completion of beam commissioning, the accelerator complex began operation in June 2006. Commissioning results and first operation experience will be presented. A plan is being devel- oped to increase beam power up to 3MW. Parameters, design and status of the SNS Power Up-

grade Project will be presented. ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05- 00OR22725

Dr. Alexander Aleksandrov: sasha@sns.gov

Ya.Derbenev , R.P.Johnson (Muon Inc., USA) Advances in Beam Cooling for Muon Colliders

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. The helical cooling channel (HCC) has solenoidal, helical dipole, helical quadrupole, and helical sex- tupole magnetic fields, where emittance exchange is achieved by using a continuous homogene- ous absorber. Momentum-dependent path length differences in the dense hydrogen energy ab- sorber provide the required correlation between momentum and ionization loss to accomplish longitudinal cooling. Recent studies of 800 MHz RF cavities pressurized with hydrogen, as would be used in this application, show that their maximum gradient is not limited by the re- quired external magnetic field, unlike vacuum cavities. Two new cooling ideas, Parametric- resonance Ionization Cooling and Reverse Emittance Exchange, will be employed to further re- duce 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 demon- stration experiment. The status of the designs, simulations, and tests of the cooling components for a high luminosity, low emittance muon collider will be reviewed.

Dr. Rolland P. Johnson: rol@muonsinc.com

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