Search

Dark matter is one of biggest open questions in physics today. In attempts to answer this question, many ultra-sensitive particle detectors have been developed to search for dark matter interactions here on Earth. In this chapter, we introduce the question of dark matter and describe in detail one such detector that searches for it: XENON1T. While XENON1T was designed to primarily search for the WIMP, a particularly well-motivated dark matter candidate, we explain that its low background level, low energy threshold, and large exposure allow us to use XENON1T to search for other signals physics beyond the Standard Model, including other dark matter candidates. This thesis focuses on the search of three such signals using XENON1T: solar axions, an enhanced neutrino magnetic moment, and bosonic dark matter.

If they exist, axion-like particles (ALPs) can be produced in the core of magnetars. As they propagate, they then convert to photons in the magnetosphere, leading to possible signatures in the X-ray photon spectrum. Moreover, since ALPs only mix with the parallel mode of the photon, interesting modifications to the photon polarization are also possible. We determine these effects by computing the Stokes parameters in the presence of ALPs and show that the relevant quantity factorizes into a product of the ALP-to-photon conversion probability and a factor that depends on the initial mixture of ALPs and photons at the surface of the magnetar.

Topologically ordered media demand a new understanding of the emergent properties of quantum matter. This is a fundamental and technological feat. Topological insulators and Weyl semimetals are materials with topological order. Here we will focus on how these materials interact with sources of the electromagnetic field. We start from the effective field theory of Maxwell’s electrodynamics extended by a so-called magnetoelectric term, namely axion electrodynamics and summarize some results we have found exploiting a Green’s function approach to solve for the electromagnetic fields. Signals of the magnetolectric effect are minute compared with other electromagnetic responses, therefore precision measurements are required for its detection. Our formulation can be used for topological insulators and Weyl semimetals with planar, cylindrical and spherical geometries interacting with general charges, currents and boundary conditions. Our formulation is exemplified by: (i) the issue of Casimir effect involving a planar topological insulator, (ii) Vavilov-Cherenkov radiation produced in the forward- and backward-direction of a charged particle traversing a planar interface of two magnetoelectric media and (iii) the electromagnetic fields induced by a static electric charge near the surface of a Weyl semimetal. All three applications can yield observable signals that are within experimental sensitivities.

We present the design of a tunable high-Q photonic bandgap (PBG) cavity, made from a periodic arrangement of dielectric rods in a woodpile like structure. We know that the axion signal rate diminishes as we move to higher axion mass searches. High quality factor achieved with this type of cavity will enable higher mass axion search with improved signal sensitivity and faster scanning rate. Quality factor in excess of the axion-Q will enable us to design interesting experiments such as the quantum non-demolition (QND) measurement of itinerant microwave photons using superconducting qubits and stimulated emission of photons.

The Axion Dark Matter eXperiment (ADMX) relies equally on a low physical temperature T and low amplifier noise temperature TN to achieve a high Signal-to-Noise Ratio (SNR). The low noise amplifier is a Microstrip SQUID Amplifier (MSA) with TN of 200 mK, which compares favorably with the best available cryogenic transistor-based amplifiers with a TN of 1.5 K, allowing a search rate up to 56 times faster, depending on T. Here we present the operating principles of the MSA and some practical considerations of MSA design in a way we hope is accessible to those not otherwise familiar with superconducting electronics or amplifier design.

Haloscope axion dark matter search experiments typically consider arrays of multiple cavities to increase the detection volume in exploring high mass regions. We, IBS/CAPP at KAIST, introduce a new concept, multiple-cell cavity, which is superior to conventional multiple-cavity design in terms of detection volume, simplicity of the experimental setup, and facilitation of the phase-matching mechanism. This idea is promising for detecting high frequency axion dark matter with enhanced experimental sensitivities. We present the characteristics of this design and demonstrate the experimental feasibility using a double-cell cavity.

The axion is a consequence of the PQ mechanism to solve the strong-CP problem and has been considered as an attractive candidate for cold dark matter. The Center for Axion and Precision Physics Research (CAPP) of the Institute for Basic Science (IBS) in South Korea has completed the construction of the infrastructure for axion dark matter search experiments. Multiple experiments are currently under preparation for parallel operation targeting at different mass ranges. The ultimate goal of our center is to be sensitive to the QCD axion models over a wide range of axion mass. The current approaches to achieve this goal are three folds: commissioning high-field magnets, designing high frequency cavities, and developing low noise amplifiers. We present the status of the experiments and discuss future prospects.

CAPP-PACE is a pilot experiment of IBS/CAPP for direct detection of axions with a mass around 10 μeV based on Sikivie’s microwave cavity scheme. The detector is equipped with an 8 T superconducting magnet and employs a dilution refrigerator that lowers the physical temperature of a high Q-factor split-type cavity to less than 45 mK. The frequency tuning system utilizes piezoelectric actuators with interchangeable sapphire and copper rods. The feeble signal ( 10−24 W) from the cavity is amplified and transmitted through the RF receiver chain with a HEMT amplifier whose noise temperature is around 1 K. I will present the results of CAPP’s first physics data runs in the axion mass range from 2.45 to 2.75 GHz and discuss our future plans and R&D projects.

The QUAX proposal studies the interaction of dark matter axions with electrons. As the effect of axions can be described as an effective magnetic field, the signal is a magnetization oscillation of a sample. To detect it, the material is placed in a resonant cavity and polarized with a static magnetic field. Here we describe the operation of such a device, with a resonance frequency of 14 GHz, corresponding to an axion mass ma = 58 μeV. Eventually some recent developments on the resonant cavities design and test are detailed.

High Temperature Superconducting (HTS) materials are now becoming incorporated into magnets that are being used for a variety of physics applications. Axion detection is a particularly attractive application for these conductors and there is significant promise that reliable systems can be built. However, there are still many challenges that are presently unresolved when it comes to building magnets of this scale from these materials. In particular, when a superconducting magnet quenches the energy stored in the magnetic field is converted into heat. If not controlled properly, the energy can be deposited in a non-uniform manner that results in excessive heating in some regions and damage to the magnet. For magnets using traditional Low Temperature Superconductors (LTS) methods of protecting the magnet during quench have been relatively well developed. For the HTS materials this development is presently underway, but no demonstrations protecting coils of the size needed for axion detection have yet been published.

The ADMX experiment is an axion haloscope using a microwave cavity in a strong magnetic field to search for dark matter axions. I will present on results from our run 1A in which we excluded the range of axion–photon couplings predicted by QCD axions for axion masses between 2.66 and 2.81 μeV. These results marked the first time a haloscope experiment achieved sensitivity to the well-motivated DFSZ axion. In addition, I will provide updates on the search for axions in the 2.82–3.31 μeV madss range with the ADMX experiment.

Relic axions generated after cosmic inflation may have a mass of around 100 μeV. While being an excellent candidate for cold dark matter, axions of this range are hardly covered by existing detection techniques, which are based on electromagnetic resonance of 3D cavities. A dielectric haloscope is a promising alternative technique for a search in this mass range. The MADMAX collaboration is aiming to build a dielectric haloscope that is sensitive to post-inflation QCD axions. Here, we present the principle, current status, and future plans of the MADMAX experiment.

An axion is a particle that could resolve some issues with strong interaction CP symmetry and dark matter. A tunable microwave cavity permeated by a strong external magnetic field can be used to detect axions. The Axion Dark Matter eXperiment (ADMX) has developed a four-cavity array design to explore the axion mass range of 5–9 μeV. Tuning of each cavity frequency is done primarily by a coarse tuning rod, with a fine tuning rod used to lock frequencies together. Aluminum prototypes at 1:3 scale have been built and tested. At 300 K, the TM010 frequency varied from 4.4 to 6.4 GHz and crossed three TE modes. Electroplating pure aluminum on the cavity improved the Q factor by 27%. Preliminary results from 4.2 K test showed a 2% reduction of resonant frequency and an improvement in Q by a factor of 2.7 compared to the 300 K values.

Precision frequency metrology can overcome critical challenges in axion dark matter searches based on the power detection method. Using a generalization of the standard axion haloscope approach onto a case with two resonant modes, it is demonstrated how dark matter axion signal is converted into resonant mode phase fluctuations. The method is not only sensitive enough in principle to achieve the predicted model bands, but also remove the main complications such as the need for strong magnetic fields, large cavity volumes, and quantum sensors making the whole experiment much more cost effective.

The Axion Resonant InterAction Detection Experiment (ARIADNE) is a collaborative effort to search for the QCD axion using nuclear magnetic resonance (NMR), where the axion acts as a mediator of spin-dependent forces between an unpolarized tungsten source mass and a sample of polarized helium-3 gas. Since the experiment involves precision measurement of a small magnetization, it relies on limiting ordinary magnetic noise with superconducting magnetic shielding. In addition to the shielding, proper characterization of the noise level from other sources is crucial. We investigate one such noise source in detail: the magnetic noise due to impurities and Johnson noise in the tungsten source mass.