CERN, Geneva
Uni HH, Hamburg
The 7 km long CERN Super Proton Synchrotron (SPS) is, apart from the LHC, the accelerator with the largest stored beam energy worldwide of up to 3 MJ. In 2008, an equipment failure led to a fast tune shift towards an integer resonance and an uncontrolled loss of a high intensity beam, which resulted in major damage of the accelerator. Distinct experimental studies and simulations provide clear understanding of the beam dynamics and the beam loss pattern at different SPS tune resonances. Diverging closed orbit oscillations, a resonant dispersion and increased beta beating are the driving effects that lead to a complete beam loss in as little as 3 turns (69μs). At the moment, the commissioning of a new turn-by-turn position interlock system which will counteract the vulnerability of the SPS is ongoing.
UMD, College Park, Maryland
We report on progress of studies of transverse and longitudinal space-charge beam physics at the University of Maryland electron ring (UMER), a low-energy, high current recirculator. The transverse beam dynamics studies include measurements of betatron and dispersion functions as well as linear resonances for a number of beam currents. We also discuss the implementation of induction focusing for the longitudinal containment of the lowest current beam. When complemented with optimized orbit steering, this longitudinal beam focusing has made possible to extend the number of turns from 100 to more than 1,000, limited mostly by electronics. Some of the results presented are compared with calculations and simulations with the computer codes ELEGANT and WARP.
BNL, Upton, Long Island, New York
There is a strong interest in heavy-ion collisions at the center of mass energies of 5-20 GeV/nucleon. This physics program is motivated by a search of the QCD phase transition critical point. Such low-energy operations started at Relativistic Heavy Ion Collider (RHIC) in 2010. The defining limitation in luminosity improvement for this program is expected to be due to the space charge. For RHIC, we are interested in rather long beam lifetime, which sets limitation on an allowable space-charge tune shift. An additional complication comes from the fact that ion beams are colliding, which requires careful consideration of the interplay of direct space-charge and beam-beam effects. We started to explore these beam dynamics effects in RHIC Accelerator Physics Experiments (APEX) in 2009 with proton beams. The experiments continued in 2010 with Au ion beams. This paper summarizes our findings and observations.
IUCEEM, Bloomington, Indiana
Fermilab, Batavia
Physics of chaos in a localized phase-space region is exploited to produce a longitudinally uniformly distributed beam. Theoretical study and numerical simulations are used to study its origin and its applicability in phase dilution of beam bunch. Through phase modulation to a double-rf system, a central region of localized chaos bounded by invariant tori are generated by overlapping parametric resonances. Condition and stability of the chaos will be analyzed. Applications of such a chaotic phase-space dilution system are high power beam, beam distribution uniformization, and industrial beam irradiation.
Fermilab, Batavia
The intrabeam scattering is the major reason of fast luminosity degradation in the Tevatron. It results in that in the case of optimal operation only about 40% of antiprotons are used to the store end and the rest are discarded. The beam cooling is the only effective remedy to mitigate this problem. Unfortunately neither electron or stochastic cooling can be effective at the Tevatron energy and bunch density. Thus the optical stochastic cooling is the only promising technology capable to cool the Tevatron beam. The paper circuses possible ways of such cooling implementation in Tevatron as well as advances in optical stochastic cooling theory. The technique looks promising and potentially can double the average Tevatron luminosity without increasing its peak value.
FZJ, Jülich
Experimentally it has been shown the achievable intensity of electron cooled beams at COSY is restricted by three main beam loss phenomena: the initial losses just after injection during 5-10 s of beam cooling, the coherent self-excited oscillation of cooled beam and the long-term losses ~ n x 1000 s. The second was successfully investigated and damped by the feedback system. In this work we study the first and third types of loss. Since the most important losses are suspected to be due to the single Coulomb scattering we have investigated the dynamic aperture with the electron beam as main source of non-linearity. We analytically and numerically studied how the dynamic aperture depends on an electron beam, in particular, value of its current, distribution, displacement relatively of proton beam and finally on TWISS-parameters in the cooler location. As a result we have concluded, that each of them influences on the dynamic aperture everyone in own way. In paper we compare the theoretical and experimental results.