Bruno Autin

The acceleration and storage of radioactive ions for a neutrino factory

The term beta-beam has been coined for the production of a pure beam of electron neutrinos or their antiparticles through the decay of radioactive ions circulating in a storage ring. This concept requires radioactive ions to be accelerated to a Lorentz gamma of 150 for 6 He and 60 for 18 Ne. The neutrino source itself consists of a storage ring for this energy range, with long straight sections in line with the experiment(s). Such a decay ring does not exist at CERN today, nor does a high -intensity proton source for the production of the radioactive ions. Nevertheless, the existing CERN accelerator infrastructure could be used as this would still represent an important saving for a betabeam facility. This paper outlines the first study, while some of the more speculative ideas will need further investigations.

Conducting target for pion production

When particles are produced inside a magnetic field, the portrait at the end of the target depends on the nature and intensity of the field. Targets embedded in a strong solenoidal field have been up to now the reference configuration for neutrino factories and muon colliders as well. An alternative configuration consists of pulsing an axial current through the target. It is shown that a conducting target can produce a much brighter beam than a target magnetized by a solenoid for the same field intensity at the periphery of the target.

Multipole fields in the antiproton accumulator magnet system

The Antiproton Accumulator is a very large aperture storage ring in which antiprotons are collected over a wide momentum range, stochastically cooled and stacked. The optical properties must be precisely realised and require a variety of high order field components. The very wide aperture and a lack of available space, preclude the use of separate sextupoles and octupoles to provide these corrections. One of the sextupole components was incorporated into the pole profile of the wide elliptic quadrupoles the left-right symmetry of which was thus broken. The other non linear components were produced by variation of the effective length of the dipoles and quadrupoles and achieved in practice with detachable end shims.

Neutrino Factory R&D In Europe

Until last year the CERN Neutrino Factory Working Group has been quite active together with other European laboratories. The sudden discovery of the bad financial situation at CERN due to the LHC construction put an abrupt halt to these studies. Lots of CERN activities were cut back to allow for the finishing of LHC in time and without any significant global increase in CERN’s budget. Nevertheless with a new organisation and several committees and working groups, activity on a European scale is still going on. This paper describes the actual situation and some European ideas in the different areas which may turn out to be very relevant in the future.

Technical challenges of neutrino factories

Abstract Using muons as a source of neutrinos can be traced back to 25 years ago but it is with the recent studies on muon colliders that this idea came back to the front of the stage. The threshold of interest for neutrino oscillation experiments is attained with about 10 20 muons per year stored in the decay ring where the neutrinos created in the muon decay are emitted towards the detector. For ultimate CP violation experiments, at least 10 21 muons per year have to be stored. A neutrino factory is a major investment and has to be built with ultimate performances in mind even if they cannot be achieved at the begining. The various stages of pion production by powerful proton beams, collection of secondary particles, fast acceleration and storage of muons are reviewed.

Emittance preservation in the PS complex

As the LHC injectors have to provide bright beams, all the potential sources of emittance blow-up must be eliminated. One such source arises from the mismatch of the betatron focusing at the interface of a transfer line with a circular machine. Measurements and corrections of this effect have been performed in the line downstream of the linac where space charge plays an important role and between the booster and the PS ring where four beams are recombined and have to be matched simultaneously.

Optimization of the transmission in an alternating gradient muon collection channel

This paper reports on recent results regarding the optimization of the transmission in a muon production channel based on quadrupole focusing technique.

Transverse Collection of Pions

Abstract The early stages of a neutrino factory are critical to fulfill physics requirements in the final muon storage ring. The transverse collection of pions behind the target is therefore a crucial feature for which different options exist. In this article, two collection systems using either quadrupoles or a transition solenoid between the target and the downstream channel are studied. The transition optics from the solenoid to a quadrupole channel is also discussed. Some figures of merit such as maximum transverse momentum captured or radial acceptance are compared as well as the technical challenges for each solution.

Beam Optics Studies on the Antiproton Accumulator

The CERN Antiproton Accumulator (AA) was designed to accumulate 6 x 1011 antiprotons per day, using the stochastic cooling technique. Its construction was completed within two years and the first beam circulated in early July 1980. This paper describes the conceptual design of the lattice and how multipole shim corrections were applied to develop the large betatron and momentum design acceptances. We also report how a sequence of such corrections, based on optics studies with proton beams, have been applied to the point that the machine is now approaching design performance.

Muon emittance and pion decay

An efficient collection of muons is a crucial task for machines such as neutrino factories or muon colliders. The definition of the beam emittance and the determination of the capture efficiencies both in transverse and longitudinal spaces is made difficult by the transition from the pion to the muon beam through the decay process. An analytical approach to the problem is derived for a transport line where path length variations can be neglected.