121358236
Emittance balancing technique for the resonant slow extraction from a synchrotron
A new method is proposed to produce identical beam emittances in the transverse phase planes from a severely asymmetric beam extracted from a slow-cycling synchrotron. This is important to obtain a good beam distribution at the irradiation spot when the spot scanning method is used for the treatment in hadron therapy. The method makes use of the beam rotation effect either by a solenoid or by a rotational quadrupole section, referred to as rotator, to produce identical emittances in the two transverse phase planes. It is also helpful for the stabilization of the beam spot at the irradiation point. Simulation studies with an artificially generated beam have been carried out to prove the principle. The method is not only applicable to fixed treatment nozzles but also to rotational gantry nozzles. Both a solenoid and a section of quadrupole rotator can be used, with the former being ideal for proton gantries and the latter for fixed carbon nozzles. There is a practical limit in using room-temperature solenoid due to the high beam rigidity in the case of a carbon beam, for which a superconducting solenoid has to be used. The comparison with other methods and the practical applications of the method are also presented.
11580844
Summary report of the impedance and instability subgroup
This subgroup discussed several technical issues facing the BTCF (Beijing tau-charm factory). Most of these are R and D issues to be performed before a construction start. The two uncertainties facing the B-factories and the BTCF alike, namely the transient ion instability and the photo-electron instability are much weaker in the BTCF. Another uncertainty concerns the monochromator scheme, for which a round of parameters optimization is called for. The R and D issues can be collected into a long list. These discussions are by no means exhaustive, but are listed below as a summary of this report: (1) impedance policing is to be established; (2) single bunch instability is marginally acceptable; (3) beam-beam effects is to be considered together with microwave instability to optimize the overall design; (4) microwave power is a new issue which needs attention; (5) trapped modes need attention; (6) aluminum antechamber vacuum chamber design is recommended; (7) electrostatic separators need to be designed to minimize the microwave power generation; (8) dust particles need attention.
124386868
The Application of Adiabatic Theorem to the Beam Dynamics in Accelerators
In this paper, the adiabatic criterion and the formulae for calculating the increment of adiabatic invariant due to the nonadiabatic change of paramters in Hamiltonian are derived and we have found that this increment is quite small, even in the case where the Landau's adiabatic criterion[1] is violated.
123202707
Chromaticity in Strong Focusing Accelerators and Storage Rings
The chromaticity formulae with accuracy to the first-order in momentum deviation in strong focusing accelerators & storage rings have been derived. It has been found that the edge magnetic field effects must be taken into account, otherwise the resultant errors introduced will be appreciable which increase rapidly with the decrease in machine size. They can not be neglected especially for proton and antiproton accumulators due to the very large momentum spread of the beams accumulated in them.
125315096
eta(c) physics at BES III
An introduction for eta(c) physics research is presented in this paper, which shows that the mechanism of eta(c) decays can't be. well described by current theoretical models and detailed experimental measurements need to be done with larger eta(c) sample. Based on the expected J/psi and psi' events taken with the planed BES III detector in one year, the eta(c) physics researches are discussed extensively, including the measurements of branching fractions of different final states, the search for new decay, modes, precision measurements of mass and width, and the search for rare decays. At last, the study of eta'(c) decays is also discussed briefly.
126424369
η and η' physics at BESIII
11750018
Measurement of the charm fragmentation into D* mesons at HERA
The charm fragmentation function has been measured with the H1 and ZEUS detectors at HERA in the deep inelastic scattering and photoproduction regimes. The measured function has been compared to different fragmentation models implemented in leading-logarithm Monte Carlo simulations and next-to-leading-order calculations.