Magnetic Shielding for HUNTER Sterile Neutrino Detector
The Heavy Unseen Neutrinos from Total Energy-momentum Reconstruction, or HUNTER, project, is working to search for sterile neutrinos by observing their mass through the electron capture decay of cesium-131. When cesium-131 decays, it releases a positive xenon ion, an x-ray, and an electron in addition to the neutrino. By building MOTRIMS, a magneto-optical trap for recoil ion spectroscopy, the momenta of these particles can be measured, and from this, the mass of the neutrino can be calculated. However, this device requires a very uniform magnetic field to be generated along its length in order to guarantee the capture of the electron. In order to assure that the field remains uniform and is unaffected by external magnetic fields, a magnetic shield must encompass the device. This is made difficult largely due to the high degree of uniformity necessary within the device and the irregular shape of the apparatus which makes it impossible to enclose it in a simple cylindrical shield. Using FEMM software, we simulated the magnetic fields generated by the device and investigated which aspects of the preliminary shielding affect the internal field. The current design, being in its early stages, has not had its shielding thoroughly studied. Our results suggest that the current shielding is ineffective on account of the gaps in the center and that correspondingly closing off the gap to any extent is helpful. However, more study is warranted, as no gap can be entirely covered. Other software such as Radia may provide a better alternative to FEMM, and a more thorough analysis can be made using this software instead once its functionality is understood.