A high intensity ⁶ He beam for the β-beam neutrino oscillation facility

Abstract

This work presents the production and extraction of the short-lived radionuclide 6 He in yet unmatched yields from the ISOLDE facility at CERN. It is the first report of 6 He production using spallation neutrons via the 9 Be(n, α) 6 He reaction. These neutrons are produced from the 1.4 GeV proton beam of the Proton Synchrotron Booster (PSB) striking a tungsten converter, and are impinging on a porous BeO material. The central position of 6 He in future experiments is due to its role as a necessary radioactive nucleus to realize the β-beam at CERN, a next-generation facility to study neutrino oscillation parameters, and hence neutrino masses. In the β-beam scenario, an intense beam of radioactive 6 He nuclei will be produced, accelerated to multi-GeV energies and stored in a dedicated storage ring. The resulting virtually mono-directional anti-neutrino beam from the decay of the stored 6 He nuclei will be directed towards a remote underground neutrino detector. A similar beam of, e.g., 18 Ne will provide neutrinos, an ideal concept to test CP violation in the neutrino sector. The results of the present experiment demonstrate for the first time that the necessary conditions for the realization of the proposed β-beam scheme with anti-neutrinos can be fulfilled.

Design of a neutrino source based on beta beams

“…5(b)] from the release curves at different target temperatures showed an intarget production that ranged from 2.6 × 10 10 to 4.1 × 10 10 6 He=μC of incident protons, in excellent agreement with the calculated 2.8 × 10 10 6 He=μC and 2.4 × 10 10 6 He=μC using FLUKA and GEANT4, respectively [17]. Therefore, about 82% of the produced isotopes were released at a target temperature of 1400°C, which translates into a release efficiency of 57% at the foreseen beta beam facility [17].…”

“…5(b)] from the release curves at different target temperatures showed an intarget production that ranged from 2.6 × 10 10 to 4.1 × 10 10 6 He=μC of incident protons, in excellent agreement with the calculated 2.8 × 10 10 6 He=μC and 2.4 × 10 10 6 He=μC using FLUKA and GEANT4, respectively [17]. Therefore, about 82% of the produced isotopes were released at a target temperature of 1400°C, which translates into a release efficiency of 57% at the foreseen beta beam facility [17]. One shall note that in the beta beams configuration, a similar neutron converter beryllium oxide target layout is proposed, with a water-cooled converter to dissipate the deposited beam power of an incoming 200 kW proton beam and a larger target allowing the interception of a larger fraction of the emitted neutrons.…”

“…The production of 6 He has been successfully validated using the isotope separation online (ISOL) method [16], where the ions have been obtained with fast neutrons on a thick beryllium oxide target. Experimental tests performed at CERN-ISOLDE showed the validation of the production of 10 14 6 He=s with 100 μA, 1.4 GeV protons and an optimized geometry [17].…”

“…The validation of the required 6 He intensities for the β beams has been performed with on-line tests at CERN-ISOLDE [17]. These tests have been performed using a standard ISOLDE unit, as shown in Fig.…”

CERN-MEDICIS (Medical Isotopes Collected from ISOLDE): A New Facility

“…Our simulated in-target production results are computed for a homogeneous target material. For ISOL (Isotope mass Separation OnLine) isotope extraction, the microstructure of the target is optimized to maximize the extraction efficiency and selectivity during the mass separation process [6]. For this last step, the experience already gained at ISOLDE during the past 40 years is of utmost importance, and possible future developments are expected to provide production gains.…”