Loss management in the beta-beam decay ring

The aim of the beta-beams is to produce pure electron neutrino and anti-neutrino highly energetic beams, coming from β-decay of the 18Ne10+ and 6He2+, both at γ = 100, directed towards experimental halls situated in the Fréjus tunnel [1], [2]. The high intensity ion beams are stored in a ring, until the ions decay. Consequently, all the injected particles will be lost anywhere around the ring generating a high level of irradiation. In order to keep a constant neutrino flux, the losses due to the decay of the radioactive ions are compensated with regular injections. The new ion beam is then merged with the stored beam with a specific RF program [3]. We have to consider two sources of losses: – The β-decay products: their magnetic rigidity being different from the reference one, they are bent differently and lost. – The losses during the injection merging process. The first one needs a particular ring design in order to insert appropriate beam stoppers at the right place. The second one needs a specific collimation system which allows beam longitudinal halo cleaning between two successive injections

The beta-beam decay ring design

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 a2Pi phase advance insertion, which improves the optical properties (dynamic aperture and momentum acceptance) and allows the easy determination of the working point bythe optics of the straight sections

Avoiding Emittance Degradation When Transferring the Beam From and to a Plasma-Wakefield Stage

International audienceThe plasma-wakefield acceleration technique is known to provide a very strong accelerating gradient (GV/m), up to three orders of magnitude higher than the conventional RF acceleration technique. The drawback is a relatively higher energy spread and especially a huge beam divergence at the plasma exit, leading to an irremediable and strong emittance degradation right after its extraction from the plasma for transferring it to an application or another plasma stage. In this article, we determine the criteria to be achieved so as to minimize this emittance growth after pointing out all the parameters involved in its mechanism. Then the plasma down ramp profile is studied in a typical configuration of the EuPRAXIA project at 5 GeV. It turns out that no specific profile is needed. For minimizing emittance growth at beam extraction, it is enough to optimize the ramp length so that the Twiss parameter γ is minimized. Finally the design of an optimal transfer line allows showing that the emittance growth can be contained to less than 10% in realistic conditions when transferring the beam to a free electron laser

Preserving emittance by matching out and matching in plasma wakefield acceleration stage

In more than four decades, particle acceleration by plasma wakefield has demonstrated its feasibility and efficiency. This acceleration technique is now starting to be planned for providing high-quality beams to well-defined user communities. High beam energy is also considered by piling successive plasma acceleration stages. In this context, avoiding beam degradation, on top of all emittance degradation, is the main concern when transferring the accelerated beam to the users or to the following acceleration stage. After examining the behavior of the trace and the phase emittances when crossing through a conventional transfer line, we are able to determine the criteria to be achieved in the plasma ramps so as to minimize emittance growth. Then the optimal density profile is studied for these ramps at the entrance and exit of a plasma stage accelerating electrons from the energy of 150 MeV to 5 GeV. Finally, the design of an optimal transfer line allows showing that the emittance growth can be contained to less than 10% in realistic conditions when transferring a beam to a free-electron laser

Updates on the Optic Corrections of FCC-hh

International audienceThe FCC-hh (Future Hadron-Hadron Circular Collider) is one of the options considered for the next generation accelerator in high-energy physics as recommended by the European Strategy Group, and the natural evolution of existing LHC. The evaluation of the various magnets mechanical error and field error tolerances in the arc sections of FCC-hh, as well as an estimation of the correctors strengths necessary to perform the error corrections, are important aspects of the collider design. In this study recommended values for the mechanical errors, dipole and quadrupole field errors tolerances are proposed, with the possible consequences on the correctors technological choice and on the beam screen design. Advanced correction schemes of the linear coupling (with skew quadrupoles) and of the beam tunes (with normal quadrupoles) are discussed. Also a combined correction scheme including the interaction regions is tested

Overview of Arc Optics of FCC-hh

International audienceThe FCC-hh (Future Hadron-Hadron Circular Collider) is one of the options considered for the next generation accelerator in high-energy physics as recommended by the European Strategy Group. In this overview the status and the evolution of the design of optics integration of FCC-hh are described, focusing on design of the arcs, alternatives, and tuning procedures

Advance on Dynamic Aperture at Injection for FCC-hh

International audienceIn the hadron machine option, proposed in the context of the Future Circular Colliders (FCC) study, the first evaluation of dipole field quality, based on the Nb3Sn technology, has shown a Dynamic Aperture at injection above the LHC target value. In this paper the effect of field imperfections on the dynamic aperture, using the updated lattice design, is presented. Tolerances on the main multipole components are evaluated including feed-down effect

Progress on the Optics Corrections of FCC-hh

International audienceThe FCC-hh (Future Hadron-Hadron Circular Collider) is one of the three options considered for the next generation accelerator in high-energy physics as recommended by the European Strategy Group, and the natural evolution of existing LHC. Studies are ongoing about the evaluation of the various magnets mechanical errors and field errors tolerances in the arc sections of FCC-hh, as well as an estimation of the correctors strengths necessary to perform the corrections of the errors. In this study advanced correction schemes for the residual orbit, the linear coupling and the ring tune are described. The impact of magnet tolerances on the residual errors, on the correctors technological choice and on the beam screen design are discussed. In particular the effect of the dipole a2 error is emphasized

Optic corrections for FCC-hh

International audienceThe FCC-hh (Future Hadron-Hadron Circular Collider) is one of the options considered for the next generation accelerator in high-energy physics as recommended by the European Strategy Group. The evaluation of the various magnets mechanical error and field error tolerances in the arc sections of FCC-hh, as well as an estimation of the required correctors strengths, are important aspects of the collider design. In this study the mechanical tolerances, dipole and quadrupole field error tolerances for the arc sections of FCC-hh are evaluated. The consolidated correction schemes of the linear coupling (with skew quadrupoles) and of the beam tunes (with normal quadrupoles) are presented. The integration of the different ring insertions (interaction region, collimation, injection, etc) is also discussed