Ionization Cooling using Parametric Resonances

[摘要] Ionization Cooling using Parametric Resonances was an SBIR project begun in July 2004 and ended in January 2008 with Muons, Inc., (Dr. Rolland Johnson, PI), and Thomas Jefferson National Accelerator Facility (JLab) (Dr. Yaroslav Derbenev, Subcontract PI). The project was to develop the theory and simulations of Parametric-resonance Ionization Cooling (PIC) so that it could be used to provide the extra transverse cooling needed for muon colliders in order to relax the requirements on the proton driver, reduce the site boundary radiation, and provide a better environment for experiments. During the course of the project, the theoretical understanding of PIC was developed and a final exposition is ready for publication. Workshops were sponsored by Muons, Inc. in May and September of 2007 that were devoted to the PIC technique. One outcome of the workshops was the interesting and somewhat unexpected realization that the beam emittances using the PIC technique can get small enough that space charge forces can be important. A parallel effort to develop our G4beamline simulation program to include space charge effects was initiated to address this problem. A method of compensating for chromatic aberrations by employing synchrotron motion was developed and simulated. A method of compensating for spherical aberrations using beamline symmetry was also developed and simulated. Different optics designs have been developed using the OptiM program in preparation for applying our G4beamline simulation program, which contains all the power of the Geant4 toolkit. However, no PIC channel design that has been developed has had the desired cooling performance when subjected to the complete G4beamline simulation program. This is believed to be the consequence of the difficulties of correcting the aberrations associated with the naturally large beam angles and beam sizes of the PIC method that are exacerbated by the fringe fields of the rather complicated channel designs that have been attempted. That is, while the designs developed and tested using the matrix program OptiM can work well, a real simulation with lumped dipoles, quadrupoles, and solenoids and their associated fringe fields has not succeeded. As a consequence of this realization, a new approach is being attempted that is based on the use of a helical solenoid (HS) channel that is made of simple coils that provide a much more homogeneous magnetic field. However, in order to use the HS a new approach was required to generate a variable dispersion that is needed according to the PIC theory described above. This approach and its first implementation will be described at EPAC08 in June, 2008.

[发布日期] 2008-06-07

[学科分类] 核物理和高能物理

[关键词] BEAM EMITTANCE;CEBAF ACCELERATOR;CHROMATIC ABERRATIONS;DESIGN;DIPOLES;GEOMETRICAL ABERRATIONS;IMPLEMENTATION;IONIZATION;MAGNETIC FIELDS;MUONS;OPTICS;PROTONS;QUADRUPOLES;SOLENOIDS;SPACE CHARGE;SYMMETRY;SYNCHROTRONS Muon;Collider;ionization cooling;parametric resonance;beam emittance