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Euronu Super Beam Design Study (2008-2012)
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One of the future options to produce high intensity neutrino beams has been investigated in the framework of the EUROnu Collaboration[1]. These facility considers a 130 km baseline between the neutrino source located at CERN and the LSM (Laboratoire Souterrain de Modane) where the MEMPHYS Cherenkov detector will be installed with a fiducial mass of 0.5 MegaTons. The source will use a primary proton beam with 4-5 GeV and a power of several MegaWatts. The technological challenge will be to build a target station able to work under theses extreme conditions.

Neutrino beam production

This superbeam will benefit for the CERN developments made for the SPL (Superconducting Proton Linac)[2]. The proton beam at the end of the accumulator will have an energy range between 4-5 GeV with 4MW beam power running at 50 Hz frequency.

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In order to minimise the power dissipation and limiting the radiation damages, the proton beam will be shared over four independent targets with 1MW for each target running at 12.5 Hz frequency. The secondary particle due the interaction inside the target will be focused by four magnetic horns in the tunnel producing the neutrino by decay in flight.

Target Station

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The four horn system is foreseen to work with a high intensity (350kA) pulsed current at 12.5 Hz frequency. A 20 kW power will be dissipated by the structure. In case of one horn is damage, the beam will be shared over the others. Hence, each horn has to work under a 1.3 MW beam power.

Target

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The target contains titanium spheres in a
cylinder with holes. An helium jet at a 10 bar pressure will circulate permently inside allowing to cool the target. This geometry allows to increase the surface with the gas and minimise the mechanical constraints due to the impact of the protons inside the target.

Magnetic horn

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The body of the horn is made of aluminium alloy Al 6061 T6 which offert a good compromise between mechanical stress, good resistance to corrosion and good electrical conductivity. The wall thickness has to be as thin as possible to ensure optimal physics performances and to limi the energy deposition inside from the secondary particles escaping the target. The mechanical constraints, due to magnetic pressure has been calculated with a finite element based model. The lifetime of the horn reach a maximum for a stress less than 30 MPa and an uniform temperature of 60°C. In order to maintain a constant temperature of the horns, water jets around their body are foreseen. The water flow inside each horn will be 60 to 120 l/min.

Power Station

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The current is supplied to the horn thanks to an electrical transmission lines 33m long and eight aluminium conductors with a rectangular section 60cmX2cm. These geometrical dimensions have been calculated in order to reduce the resistivity and the inductance. The power station will be located in a special room 180m2 which will be able to support a specific weight of 1ton/m2. The electrical consumption of 1.3 MW with a total dissipated power of 243 kW by water cooling and 280 kW by air.

Building

The building concept will include the target station consisting of the four magnetic horns equipped with their target. The decay tunnel length reach 25m. A special hot cell able to manipulate highly radioactive material is foreseen for repairing or replacement of horn with a specific equipment.

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References:
[1] EUROnu - WP2
[2] Conceptual design of the SPL II : A high-power superconducting H− linac at CERN : CERN-2006-006
[3] The SPL Neutrino Super Beam arXiv:1212.0732

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