Publications: Conference

Author(s) :F.W. Jones, TRIUMF, Vancouver, Canada, and E. Wildner, CERN, Geneva, Switzerland

Radioactive ions injected into the decay ring of a Betabeam neutrino facility will constitute a continuous source of decay products distributed around the ring. Secondary ions from beta decays will differ in charge state from the primary ions and will follow widely offmomentum orbits. In the racetrack configuration of the ring, they will be mismatched in the long straights and may acquire large amplitudes, but the great majority of losses will be in the arcs. We describe here a comprehensive model of ion decay, secondary ion tracking, and loss detection, which has been implemented in the tracking and simulation code Accsim. Methods have been developed to accurately follow ion trajectories at large momentum deviations as well as to detect their impact coordinates on vacuum chamber walls and possibly inside magnetic elements. Using secondary-ion data from Accsim and postprocessing with Mathematica, we have implemented a follow-on simulation in FLUKA with a 3D geometry of decay ring components and physics models for ion interactions in matter, allowing radiological studies and in particular the visualization and analysis of heat deposition in the dipole magnets which is a critical design factor for the ring. In our simulations we have also implemented absorber elements which are intended to localize the majority of losses outside of the dipoles. These studies provide estimates of ring performance (in terms of loss concentration and management), the effectiveness of absorbers, and the implications for successful superconducting dipole operation.

Author(s) :E. Wildner, M. Benedikt, N. Emelianenko, A. Fabich, S. Hancock, M. Lindroos

The beta beam concept for the production of intense (anti-)neutrino beams is now well established. A baseline design has recently been published for a beta-beam facility at CERN. It has the virtue of respecting the known limitations of the CERN PS and SPS synchrotrons, but falls short of delivering the requested annual rate of neutrinos. We report on a first analysis to increase the rate using the baseline ions of 6He and 18 Ne. A powerful method to understand the functional dependence of the many parameters that influence the figure of merit for a given facility is available with modern analytical calculation software. The method requires that a symbolic analytical description is produced of the full accelerator chain. Such a description has been made using Mathematica for the proposed beta beam facility at CERN. The direct access from Mathematica to an ORACLE database for reading basic design parameters and re-injecting derived parameters for completion of the parameter list is both convenient and efficient. We acknowledge the financial support of the European Community under the FP6 “Research Infrastructure Action - Structuring the European Research Area” EURISOL DS Project Contract no. 515768 RIDS.

Author(s) :A. Chancé, J. Payet, CEA/DSM/DAPNIA, Saclay, France

The aim of the beta-beams is to produce highly energetic beams of pure electron neutrino and antineutrino, coming from β-decays of the 18Ne10+ and 6He2+, both at gamma = 100, directed towards experimental halls situated in the Fréjus tunnel. The high intensity ion beams are stored in a ring until the ions decay. Consequently, all the injected ions will be lost anywhere in the ring, generating a high level of irradiation. Since they come from the SPS, the ring circumference has to be a multiple of the SPS one. The straight sections must be as long as possible in order to maximize the useful neutrino flux. The straight section length is chosen to be about 36% of the circumference length, which imposes 1-km-long arcs. The bend field in the arcs is then achievable. The arc has been chosen as a 2Pi phase advance insertion, which improves the optical properties (dynamic aperture and momentum acceptance) and allows the easy determination of the working point by the optics of the straight sections.

Author(s) :A. Chancé, J. Payet, CEA/DSM/ DAPNIA, Saclay, France

LOSS MANAGEMENT IN THE BETA-BEAM DECAY RING

Author(s) :Elena Wildner, Christine Vollinger (CERN, Geneva)

The aim of beta beams in a decay ring is to produce highly energetic pure electron neutrino and anti-neutrino beams coming from b-decay of 18Ne10+ and 6He2+ ion beams. The decay products, having different magnetic rigidities than the ion beam, are deviated inside the dipole. The aperture and the length of the magnet have to be optimized to avoid that the decay products hit the coil. The decay products are intercepted by absorber blocks inside the beam pipe between the dipoles to protect the following dipole. A first design of a 6T arc dipole using a cosine theta layout of the coil with an aperture of 80 mm fulfils the optics requirements. Heat deposition in the coil has been calculated using different absorber materials to find a solution to efficiently protect the coil. Aspects of impedance minimization for the case of having the absorbers inside the beam pipe have also been addressed.

Author(s) :M. Benedikt, A. Fabich, E. Mahner, CERN M. Kirk, C. Omet, P. J. Spiller, GSI

The beta-beam is based on the acceleration and storage of radioactive ions. Due to the large number of ions required and their relatively short lifetime, beam losses are a major concern. This paper estimates the decay losses for the part of the accelerator chain comprising the CERN PS and SPS machines. For illustration purposes, the power deposition in these accelerators is compared to that expected for nominal CNGS proton operation. The beam losses induced vacuum dynamics is simulated and the consequences for machine operation are discussed.

Author(s) :M. Lindroos, A. Källberg

The beta-beam is based on the acceleration and storage of radioactive ions. Due to the large number of ions required and their relatively short lifetime, beam losses are a major concern. This paper estimates the decay losses for the part of the accelerator chain comprising the CERN PS and SPS machines. For illustration purposes, the power deposition in these accelerators is compared to that expected for nominal CNGS proton operation. The beam losses induced vacuum dynamics is simulated and the consequences for machine operation are discussed.

Author(s) :A. Chance (Saclay), S. Hancock (CERN)

The so-called beta-beam concept for accelerator-driven neutrino experiments envisages the production of a pure beam of electron neutrinos (or their antiparticles) through the beta-decay of radioactive ions circulating in a high-energy storage ring. An unprecedented number of ions must be collected in the decay ring and maintained in a few short bunches. Stacking is unavoidable to match the available source rates with this demand. A new stacking method makes use of off-momentum injection into the decay ring to approach the circulating beam without requiring ultra-fast injection elements, rotation in the longitudinal plane to bring the fresh bunches onto the central orbit and asymmetric merging to transport these ions into the centre of the large stack. Simulation results are presented for the repetitive stacking process for two candidate ion species of significantly different charge-to-mass ratio.

Author(s) :M. Benedikt, A. Fabich, E. Mahner, CERN;M. Kirk, C. Omet, P. Spiller, GSI Darmstadt

The Beta-beam is based on the acceleration and storage of radioactive ions. Due to the large number of ions required and their relatively short lifetime, beam losses are a major concern.

Author(s) :Ander Kaellberg, MSL, Stockholm University, Sweden;Mats Lindroos, AB department, CERN;Ansgar Simonson, MSL, Stockholm University, Sweden

The EU supported EURISOL Design Study encompasses a beta-beam facility for neutrino physics. Intense electron (anti-)neutrino beams are in such a machine generated through the decay of radioactive ions in a high energy storage ring.