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Design of the vacuum tube in the detector area for the NNBAR experiment

Eriksson, Harald LU (2024) PHYM01 20241
Solid State Physics
Particle and nuclear physics
Abstract
In the search for neutron antineutron oscillations (n → ̄n) in the proposed 200m long NNBAR beamline, it is imperative that the pions originating from the antineutron annihilation events can be detected outside of the vacuum chamber. The purpose of the design of the vacuum chamber then becomes to minimise the effect of the chamber while also adhering to the requirements of the pressure vessels. To this end, three different materials have been proposed and studied in this work, Alu- minium alloy (Al 6063-T6), Beryllium and Aluminium-Beryllium alloy (AlBeMet 162). To study the thickness of the walls for the vacuum chamber, the EN-13445 standard for unfired pressure vessels together with ANSYS was used with a 6 meter long tube with a diameter... (More)
In the search for neutron antineutron oscillations (n → ̄n) in the proposed 200m long NNBAR beamline, it is imperative that the pions originating from the antineutron annihilation events can be detected outside of the vacuum chamber. The purpose of the design of the vacuum chamber then becomes to minimise the effect of the chamber while also adhering to the requirements of the pressure vessels. To this end, three different materials have been proposed and studied in this work, Alu- minium alloy (Al 6063-T6), Beryllium and Aluminium-Beryllium alloy (AlBeMet 162). To study the thickness of the walls for the vacuum chamber, the EN-13445 standard for unfired pressure vessels together with ANSYS was used with a 6 meter long tube with a diameter of 2 meters. This to ensure that the tube does not buckle for the different materials due to external pressure. The thinnest possible wall thicknesses were 10mm (Al 6063-T6), 8.75mm (Be) and 10.25mm (AlBeMet 162). The different designs were then simulated in Geant4 in order to study scattering related parameters for signal particles for each design. The scattering angle distribution gave a mean FWHM for both the x- and y- direction for the thinnest material designs as 2.06◦ (Al 6063-T6), 0.87◦ (Be) and 1.36◦ (AlBeMet 162) . Lastly a vacuum simulation in MolFlow+ was done with proposed models for both the HIBEAM and the NNBAR experiment. The set up consisted of 17 turbopumps (HiPace®350 for the HIBEAM and HiPace®700 for the NNBAR), each in the central region of the beamlines. The mean pressure with an outgassing rate of 10−10mbar · l · s−1 · cm−2 resulted to 7.42 · 10−9mbar for the HIBEAM and 2.66 · 10−7mbar for the NNBAR vacuum system. (Less)
Popular Abstract
There are several open problems in particle physics that the standard model (SM) could not resolve. Aspects of the current state of the universe that were left unanswered were those such as the the matter-antimatter asymmetry (baryogenesis). It is intuitively understood as the universe seems to be made up exclusively of matter rather than antimatter. According to the SM, this asymmetry should not exist and requires a net baryon asymmetry. A prerequisite for this net baryon asymmetry are baryon number violating possesses such as the transitions of neutrons to antineutrons (n → n¯). It is the main goal of the NNBAR experiment (the pronunciation of nn¯) to find the neutron-antineutron oscillations. If even a single particle is observed to... (More)
There are several open problems in particle physics that the standard model (SM) could not resolve. Aspects of the current state of the universe that were left unanswered were those such as the the matter-antimatter asymmetry (baryogenesis). It is intuitively understood as the universe seems to be made up exclusively of matter rather than antimatter. According to the SM, this asymmetry should not exist and requires a net baryon asymmetry. A prerequisite for this net baryon asymmetry are baryon number violating possesses such as the transitions of neutrons to antineutrons (n → n¯). It is the main goal of the NNBAR experiment (the pronunciation of nn¯) to find the neutron-antineutron oscillations. If even a single particle is observed to transition from neutron to a antineutron, it could be a key discovery to explain why this matter-antimatter asymmetry exists in the universe. NNBAR is still under construction, but will when completed be a 200m long beamline having for the majority part of the beamline a diameter of 3m, all in vacuum. The method for detecting the antineutrons will be to measure the annihilation events signal that is emitted when the antineutron collides with another neutron or proton. Detectors will be placed outside of the 200m long beamline. The signal then needs to pass through the vacuum walls to be measured. The walls can then affect the signal negatively. The scope of this work focuses on minimising this effect by comparing different material choices for the vacuum chamber and designing it as thin as possible while still being thick enough to handle a vacuum pressure. To this end mechanical simulations in ANSYS has been used. The effect these different designs has on the signal was then furthered studied using Geant4 simulations. Lastly, the first vacuum simulations for the NNBAR experiment were done in MolFlow+ and a proposed vacuum system was put forth. (Less)
Please use this url to cite or link to this publication:
author
Eriksson, Harald LU
supervisor
organization
course
PHYM01 20241
year
type
H2 - Master's Degree (Two Years)
subject
keywords
ESS, vacuum, NNBAR, HIBEAM, Ansys, MolFlow+, MolFlow, Geant4
language
English
id
9168452
date added to LUP
2024-07-04 14:04:14
date last changed
2024-07-04 14:04:14
@misc{9168452,
  abstract     = {{In the search for neutron antineutron oscillations (n → ̄n) in the proposed 200m long NNBAR beamline, it is imperative that the pions originating from the antineutron annihilation events can be detected outside of the vacuum chamber. The purpose of the design of the vacuum chamber then becomes to minimise the effect of the chamber while also adhering to the requirements of the pressure vessels. To this end, three different materials have been proposed and studied in this work, Alu- minium alloy (Al 6063-T6), Beryllium and Aluminium-Beryllium alloy (AlBeMet 162). To study the thickness of the walls for the vacuum chamber, the EN-13445 standard for unfired pressure vessels together with ANSYS was used with a 6 meter long tube with a diameter of 2 meters. This to ensure that the tube does not buckle for the different materials due to external pressure. The thinnest possible wall thicknesses were 10mm (Al 6063-T6), 8.75mm (Be) and 10.25mm (AlBeMet 162). The different designs were then simulated in Geant4 in order to study scattering related parameters for signal particles for each design. The scattering angle distribution gave a mean FWHM for both the x- and y- direction for the thinnest material designs as 2.06◦ (Al 6063-T6), 0.87◦ (Be) and 1.36◦ (AlBeMet 162) . Lastly a vacuum simulation in MolFlow+ was done with proposed models for both the HIBEAM and the NNBAR experiment. The set up consisted of 17 turbopumps (HiPace®350 for the HIBEAM and HiPace®700 for the NNBAR), each in the central region of the beamlines. The mean pressure with an outgassing rate of 10−10mbar · l · s−1 · cm−2 resulted to 7.42 · 10−9mbar for the HIBEAM and 2.66 · 10−7mbar for the NNBAR vacuum system.}},
  author       = {{Eriksson, Harald}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Design of the vacuum tube in the detector area for the NNBAR experiment}},
  year         = {{2024}},
}