Overview of the New Facility

The NGS consists of a neutrino beam directed towards the INFN Gran Sasso Laboratory, an underground laboratory in central Italy, 732 km from CERN, and an underground experimental area for neutrino physics approximately 2 km from CERN at the boundary of the Geneva airport. The far site will allow the search for neutrino oscillations over a long baseline (LBL) while the experimental area near CERN will serve a short base line (SBL) experiment such as TOSCA. The main components of the NGS are shown in Figure 1.

The design of the NGS is deeply rooted in the WANF experience and many of the improvements proposed for the WANF in SPSC/I213 have been adopted in the NGS design. The experimental conditions are to a large extent similar. As the WANF, the NGS beam will be an essentially pure beam with a similar average neutrino energy. We will emphasise here in some detail the main differences in the experimental conditions for TOSCA, that follow from differences in the two beams :

• The NGS will use a proton beam with a momentum up to 450GeV/c extracted from the CERN SPS in LSS4. The reference beam momentum is 400GeV/c.
• The neutrino spill is foreseen to be almost 500 times shorter in the NGS, where a fast extraction (FE), over 10 , of the primary proton beam is planned. A slower 5 ms fast-slow resonant extraction (FS) is presently used in the WANF.
• The target station is designed to house a segmented graphite target, based on the successful design of the T9 target in the present WANF [3]. The change from a beryllium target in the WANF to a graphite target is suggested by the better thermo-mechanical properties of graphite and is expected to allow the change from fast-slow (5ms) to fast (10 s) proton beam extraction without danger to the target even at higher proton intensities. The secondary meson yield is expected to be similar.
• The decay tunnel of the NGS is foreseen to be about 1000 m long, more than three times longer than the WANF tunnel with a length of 289 m.
• The beam dump at the end of the decay tunnel starts with a graphite insert that provides a better distribution of the deposited heat.
• The distance of the TOSCA detector from the primary neutrino production target is foreseen to be about twice as long in the NGS compared to the WANF, 1858 m and 830 m, respectively.

A two-stage focusing system, horn and reflector will focus a range of chosen and K momenta into a parallel beam, pointing towards the Gran Sasso Laboratory. The WANF experience is the origin of the choice for the focusing elements, horn and reflector, two coaxial lenses, similar in shape but different in size. Their characteristics are not very different from those used in the WANF [4]. The distances of horn and reflector from the target and the shape of the magnetic field provided by them are chosen such to provide a wide-band high-energy beam.

Most of the pion and kaon decays produce a neutrino and a muon. A muon monitoring system will permit on-line monitoring, tuning and control of the beam and its alignment. Measuring the muon intensity and profile provides information on the intensity and profile of the neutrino beam.

The NGS is fully described in [5], the conceptual design report prepared by the NGS CERN-INFN Technical Committee.

  
Figure 1: Vertical cut showing the SPS and the main components of the NGS.