JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
The Japan Proton Accelerator Research Complex (J-PARC) consists of Linac, 3-GeV rapid cycling synchrotron (RCS) and 50-GeV main ring synchrotron (MR). The J-PARC has been beam-commissioned since November 2006. The Linac and RCS have recently completed initial tunings of the basic parameters, and are now in transition from commissioning to operation and also to the challenging phase for aiming at the higher current operation. The MR also has recently started initial tunings in the storage mode. In this talk, the current status of the J-PARC beam commissioning will be outlined together with experimental data obtained in the actual beam tuning procedures.
Fermilab, Batavia, Illinois
While a beam is being bunched, a coherent synchrotron frequency grows from zero to a maximal value, crossing many synchro-betatron resonances of the bunch motion. If a related driving force is high enough, the beam can get unstable. This phenomenon is important at Fermilab Booster, presumably being driven by dispersion in the cavities. To stabilize the beam, high chromaticities are required.
Fermilab, Batavia, Illinois
Coupling between different degrees of freedom complicates analysis of beam dynamics in a ring. Nevertheless appropriate choice of dynamic variables often allows reducing a problem to uncoupled case. Effects of coupling on the beam instabilities and their damping are considered. As examples the X-Y coupling in Tevatron and the coupling of longitudinal and horizontal motion in FNAL Booster are considered.
ORNL, Oak Ridge, Tennessee
The 248 meter Spallation Neutron Source accumulator ring is designed to operate with a beam intensity of 1.5·1014 ppp. A major concern for high intensity operation is the possibility of beam instabilities. Recently a series of experiments have been performed to systematically map out the instability parameter space. Beam instabilities have been measured versus betatron tune, ring RF voltage, lattice chromaticity, and beam intensity. The results of these studies are presented here
IUCF, Bloomington, Indiana
Fermilab, Batavia, Illinois
Scaling laws of the emittance growth factor (EGF) for a beam crossing the 6th order systematic space-charge resonances and the random 4th order resonance driven by octupoles are obtained by numerical multi-particle simulations. These scaling laws can be used in setting the minimum acceleration rate, and the maximum tolerable resonance strength for the design of non-scaling fixed-field alternating gradient (FFAG) accelerators.
CERN, Geneva
The Large Hadron Collider (LHC) will collide two protons beam with an energy of 7 TeV each. The stored energy and intensity exceeds the quench level of the superconducting magnets and the damage level of the machine components by far. Therefore a robust and reliable collimation system is required which controls the losses to the superconducting magnets below the quench limit and to protect the accelerator components from damage in the event of beam loss. The layout and design of the LHC collimation system is presented and the expected system performance is shown. The calculated losses around the ring were provided as input for energy deposition studies in the cleaning insertions itself but also close to experimental insertions. In addition the results from studies on proton losses originating from p-p interaction in the experiments are shown.