Abstract
The beam windows of high-energy beam lines are important, and it is sometimes difficult to design because it is necessary to ensure particle propagation with minimum disturbance and fulfill mechanical requirements at the same time. The upstream decay pipe window of the long baseline neutrino facility at Fermilab has an extremely large diameter (1.8 m), with a thickness of only 1.5 mm to separate the helium atmosphere in the decay pipe and the nitrogen atmosphere on the other side. Furthermore, the center of this dish-shaped window is expected to be a 200-mm-diameter beryllium dish welded to the outside aluminum alloy A6061, and this welded combination must withstand extreme conditions of a 2.4-MW, high-energy proton beam without leakage. These severe conditions make the design of this window an unprecedented challenge. This paper describes the static thermal-structural analyses based on which the structure has been optimized, as well as dynamic analyses for understanding the shockwave effects originating in the beam. After optimization, the maximum von Mises stresses in the window decreased significantly in both normal operation and accident cases, making our design very reasonable.
Highlights
The long baseline neutrino facility (LBNF) is a facility under construction that will provide the accelerator, primary beam, and target infrastructure for the production of a neutrino beam to serve Deep Underground Neutrino Experiment (DUNE) [1, 2]
Because of their low mass; plastic or organic materials tend not to have high resistance to high irradiation doses. Aluminum is another conventional beam window material that has the properties of low density, radiation resistance, and good mechanical strength, and it has been used for proton beam windows at spallation neutron sources such as JSNS [7] and CSNS [8], as well as decay pipe window at NuMI [9]
Forced air cooling has been chosen from the thermal analyses, and forced water cooling could be added in the future if needed
Summary
The long baseline neutrino facility (LBNF) is a facility under construction that will provide the accelerator, primary beam, and target infrastructure for the production of a neutrino beam to serve Deep Underground Neutrino Experiment (DUNE) [1, 2]. A high-intensity, high-energy proton beam accelerated in the Fermilab accelerator complex, with an energy of 120 GeV, impinges on a special target, producing high-energy pions and kaons These unstable secondaries will be focused by magnetic horns and directed through a decay pipe with a length of 194 m toward a hadron absorber. Because of their low mass; plastic or organic materials tend not to have high resistance to high irradiation doses Aluminum is another conventional beam window material that has the properties of low density, radiation resistance, and good mechanical strength, and it has been used for proton beam windows at spallation neutron sources such as JSNS [7] and CSNS [8], as well as decay pipe window at NuMI [9]. A window has been designed and will be constructed
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