Stability analyses of the beam tube cooling system in the KATRIN source cryostat Original Research Article

The Karlsruhe Tritium Neutrino Experiment (KATRIN) will measure the mass of the electron antineutrino with a sensitivity of View the MathML source0.2eV/c2, based on the precise measurement of the T2βT2β spectrum in a region close to the endpoint. This requires a T2T2 source, which can provide 1011β1011β decay electrons per second. The KATRIN source cryostat consists in its centre of a 10 m long beam tube of 90 mm inner diameter, operated at 30 K. Molecular T2T2 is injected in the beam tube through a central injection chamber and pumped at either tube end. The T2T2 density profile must have a stability of 10-310-3 in order to limit the systematic errors, yielding stringent requirements on the beam tube temperature homogeneity and stability of View the MathML source±30mK. This shall be achieved with a design, where the thermal radiation from the vacuum pumps is almost entirely absorbed by LN2LN2 and He heat exchangers on the pump ports. The beam tube itself is cooled with two-phase tubes that are part of a Ne thermosiphon. After describing the thermal environment of the beam tube, the design parameters and the operational limits of the thermosiphon will be discussed. This is followed by a detailed analysis of its dynamic behaviour, based on experimental data taken in the primary He cooling system. A “tailor-made” Ne condenser design is presented, enabling the suppression of the primary He temperature variations by two orders of magnitude, from c. View the MathML source±0.3K to below View the MathML sourceThe Karlsruhe Tritium Neutrino Experiment (KATRIN) will measure the mass of the electron antineutrino with a sensitivity of View the MathML source0.2eV/c2, based on the precise measurement of the T2βT2β spectrum in a region close to the endpoint. This requires a T2T2 source, which can provide 1011β1011β decay electrons per second. The KATRIN source cryostat consists in its centre of a 10 m long beam tube of 90 mm inner diameter, operated at 30 K. Molecular T2T2 is injected in the beam tube through a central injection chamber and pumped at either tube end. The T2T2 density profile must have a stability of 10-310-3 in order to limit the systematic errors, yielding stringent requirements on the beam tube temperature homogeneity and stability of View the MathML source±30mK. This shall be achieved with a design, where the thermal radiation from the vacuum pumps is almost entirely absorbed by LN2LN2 and He heat exchangers on the pump ports. The beam tube itself is cooled with two-phase tubes that are part of a Ne thermosiphon. After describing the thermal environment of the beam tube, the design parameters and the operational limits of the thermosiphon will be discussed. This is followed by a detailed analysis of its dynamic behaviour, based on experimental data taken in the primary He cooling system. A “tailor-made” Ne condenser design is presented, enabling the suppression of the primary He temperature variations by two orders of magnitude, from c. View the MathML source±0.3K to below View the MathML sourceThe Karlsruhe Tritium Neutrino Experiment (KATRIN) will measure the mass of the electron antineutrino with a sensitivity of View the MathML source0.2eV/c2, based on the precise measurement of the T2βT2β spectrum in a region close to the endpoint. This requires a T2T2 source, which can provide 1011β1011β decay electrons per second. The KATRIN source cryostat consists in its centre of a 10 m long beam tube of 90 mm inner diameter, operated at 30 K. Molecular T2T2 is injected in the beam tube through a central injection chamber and pumped at either tube end. The T2T2 density profile must have a stability of 10-310-3 in order to limit the systematic errors, yielding stringent requirements on the beam tube temperature homogeneity and stability of View the MathML source±30mK. This shall be achieved with a design, where the thermal radiation from the vacuum pumps is almost entirely absorbed by LN2LN2 and He heat exchangers on the pump ports. The beam tube itself is cooled with two-phase tubes that are part of a Ne thermosiphon. After describing the thermal environment of the beam tube, the design parameters and the operational limits of the thermosiphon will be discussed. This is followed by a detailed analysis of its dynamic behaviour, based on experimental data taken in the primary He cooling system. A “tailor-made” Ne condenser design is presented, enabling the suppression of the primary He temperature variations by two orders of magnitude, from c. View the MathML source±0.3K to below View the MathML sourceThe Karlsruhe Tritium Neutrino Experiment (KATRIN) will measure the mass of the electron antineutrino with a sensitivity of View the MathML source0.2eV/c2, based on the precise measurement of the T2βT2β spectrum in a region close to the endpoint. This requires a T2T2 source, which can provide 1011β1011β decay electrons per second. The KATRIN source cryostat consists in its centre of a 10 m long beam tube of 90 mm inner diameter, operated at 30 K. Molecular T2T2 is injected in the beam tube through a central injection chamber and pumped at either tube end. The T2T2 density profile must have a stability of 10-310-3 in order to limit the systematic errors, yielding stringent requirements on the beam tube temperature homogeneity and stability of View the MathML source±30mK. This shall be achieved with a design, where the thermal radiation from the vacuum pumps is almost entirely absorbed by LN2LN2 and He heat exchangers on the pump ports. The beam tube itself is cooled with two-phase tubes that are part of a Ne thermosiphon. After describing the thermal environment of the beam tube, the design parameters and the operational limits of the thermosiphon will be discussed. This is followed by a detailed analysis of its dynamic behaviour, based on experimental data taken in the primary He cooling system. A “tailor-made” Ne condenser design is presented, enabling the suppression of the primary He temperature variations by two orders of magnitude, from c. View the MathML source±0.3K to below View the MathML source