The MIGDAL experiment
File(s)
Author(s)
Marley, Timothy
Type
Thesis
Abstract
The cosmological and astrophysical evidence for dark matter (DM) is overwhelming, yet its nature remains unknown beyond gravitational interactions. A leading candidate for DM particles are weakly interacting massive particles (WIMPs), with masses in the ~1 -- 10,000 GeV range. Direct DM detectors typically search for these particles through their elastic scattering off nuclei, but nuclear recoils (NRs) which occur below some small threshold energy -- typically of O(1 keV) -- are not detectable in most technologies. This creates a kinematic limit for the minimum DM mass detectable by these methods. One can expand this sensitivity to lower DM masses by invoking the `Migdal effect’, where the sudden acceleration of a nucleus may (rarely) result in the ejection of a higher energy electron, which might be easier to detect than the accompanying NR. Although the Migdal effect has been observed in radioactive decay, its low probability means it has not yet been observed in nuclear scattering, making experimental confirmation crucial for its use in DM searches.
The Migdal In Galactic Dark mAtter expLoration (MIGDAL) experiment aims to achieve the direct observation of the Migdal effect in nuclear scattering. This work describes the design, construction, calibration, and operation of the MIGDAL optical time projection chamber. It covers preliminary tests that informed the design, including feasibility studies of the micro-pattern technologies used. Details of the detector components, readout noise, and optical system distortions are evaluated. The experiment’s simulation stack is discussed, highlighting a novel method for simulating secondary NR cascades. Additionally, the MIGDAL detector's response to low and high ionisation density tracks from charged particles is showcased, demonstrating its capability to resolve Migdal-like topologies while rejecting coincident events. The MIGDAL detector technology shows great promise, and this thesis explores its potential in a very competitive area of physics.
The Migdal In Galactic Dark mAtter expLoration (MIGDAL) experiment aims to achieve the direct observation of the Migdal effect in nuclear scattering. This work describes the design, construction, calibration, and operation of the MIGDAL optical time projection chamber. It covers preliminary tests that informed the design, including feasibility studies of the micro-pattern technologies used. Details of the detector components, readout noise, and optical system distortions are evaluated. The experiment’s simulation stack is discussed, highlighting a novel method for simulating secondary NR cascades. Additionally, the MIGDAL detector's response to low and high ionisation density tracks from charged particles is showcased, demonstrating its capability to resolve Migdal-like topologies while rejecting coincident events. The MIGDAL detector technology shows great promise, and this thesis explores its potential in a very competitive area of physics.
Version
Open Access
Date Issued
2024-02
Date Awarded
2024-06
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Araujo, Henrique
Majewski, Pawel
Sponsor
Science and Technology Facilities Council (Great Britain)
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)