The length and diameter of the pipe also affect the neutrino flux spectrum. A longer decay pipe increases the total neutrino flux with a larger flux increase at higher energies, while a larger diameter allows the capture and decay of lower-energy pions, increasing the neutrino flux at lower energies. The dimensions of the pipe affect some of the backgrounds. Studies of the optimal decay pipe dimensions will be coordinated with the optimization of the target and horn systems described above. As described earlier in this CDR, the target chase is air filled and together with the surrounding target pile it is cooled by air. There are two studies in progress that could eventually determine gas selection for use in the target chase/pile cooling system: (1) the LBNF Corrosion Task Force studies that includes both measurements at NuMI and associated modeling, and (2) LBNF studies of Air Releases to the Atmosphere. The conclusion from either one or both of these studies could require that the oxygen and argon concentrations in the target pile cooling system be minimized to mitigate the possible problems of (1) corrosion due to ozone production, and/or (2) radionuclide emission to the atmosphere. As discussed in the Neutrino Beam section of the CDR, compliance with a requirement to minimize the oxygen concentration will be accomplished by changing the cooling gas from air to nitrogen gas or possibly to helium. The conclusion of the LBNF Beamline Air-Releases Design Review that took place in April 2015 indicates that the reference design scheme to keep air-releases under control is reasonable and with sufficient safety factor. The air-releases calculations will be revisited between CD-1 and CD-2 after the volumes of the target chase and decay pipe are finalized.
The length and diameter of the pipe also affect the neutrino flux spectrum. A longer decay pipe increases the total neutrino flux with a larger flux increase at higher energies, while a larger diameter allows the capture and decay of lower-energy pions, increasing the neutrino flux at lower energies. The dimensions of the pipe affect some of the backgrounds. Studies of the optimal decay pipe dimensions will be coordinated with the optimization of the target and horn systems described above. As described earlier in this CDR, the target chase is air filled and together with the surrounding target pile it is cooled by air. There are two studies in progress that could eventually determine gas selection for use in the target chase/pile cooling system: (1) the LBNF Corrosion Task Force studies that includes both measurements at NuMI and associated modeling, and (2) LBNF studies of Air Releases to the Atmosphere. The conclusion from either one or both of these studies could require that the oxygen and argon concentrations in the target pile cooling system be minimized to mitigate the possible problems of (1) corrosion due to ozone production, and/or (2) radionuclide emission to the atmosphere. As discussed in the Neutrino Beam section of the CDR, compliance with a requirement to minimize the oxygen concentration will be accomplished by changing the cooling gas from air to nitrogen gas or possibly to helium. The conclusion of the LBNF Beamline Air-Releases Design Review that took place in April 2015 indicates that the reference design scheme to keep air-releases under control is reasonable and with sufficient safety factor. The air-releases calculations will be revisited between CD-1 and CD-2 after the volumes of the target chase and decay pipe are finalized.
CDR%20Volume%203.docx