Session G12: Axions II

Live

ALPS II is a light shining through walls experiment which searches for axions and axion-like particles (ALPs). It utilizes two aligned optical cavities inside two 120 m long strings of HERA dipole magnets. The first cavity amplifies a laser field which produces a stream of ALPs while the second one, behind a light-tight wall, amplifies a regenerated field produced by the ALPs. The experiment requires to keep both cavities aligned and in resonance with each other to maximize the regenerated field amplitude. I will report on the length and alignment sensing and control scheme as well as the integrated signal sensing and veto scheme which is currently being installed and which will be used for the first upcoming science runs.   

Live

HAYSTAC [1] is a dark matter detector that searches for an axion-induced power excess spectrally coincident with the resonance of a microwave cavity immersed in a strong magnetic field. The current HAYSTAC cavity achieves frequency tunability over the 3.6 - 5.8 GHz window via its single, off-center tuning rod. Probing higher frequencies, however, introduces unique challenges. In particular, smaller volumes, lower quality factors, and higher densities of intruder modes decrease sensitivity and increase operational complexity. Through electromagnetic simulations, we found that a seven-rod design will allow HAYSTAC to probe higher axion masses while maintaining axion sensitivity greater than that of the standard single-rod design for the cavity frequency range 5.5 - 7.4 GHz. We present the characterization of this constructed seven-rod cavity. This cavity will allow HAYSTAC to probe a well-motivated frequency range [2]. [1] B. M. Brubaker et al., First Results from a Microwave Cavity Axion Search at 24 micro-eV, PRL 118, 061392 (2017). [2] V. B. Klaer and G. D. Moore, The dark-matter axion mass, JCAP 11, 049 (2017).   

Axion Dark Matter Searches with AMO techniques

We have developed a system for measuring nuclear spin energy splittings with unprecedented stability and sensitivity. Using this we have begun a search for axionic dark matter across a wide-range of masses, including the particularly interesting ``Fuzzy’’ dark matter scenario. Our system consists of highly polarized Helium 3 and Neon 21, whose precession is monitored by a colocated spin-exchange-relaxation-free Rb-magnetometer. The Rb magnetometer readout allows very sensitive measurement of the nuclear-spin magnetization, but also introduces large shifts in their energy levels. Understanding and controlling these shifts is the main experimental issue in our system. I will discuss the experimental challenges and our solutions thus far, as well as showing preliminary results of searching for ``Fuzzy’’ dark matter axions with this system.   

Analysis of the APEX Experiment Data

The A Prime Experiment (APEX) at Jefferson Lab took data for the search for the dark matter force mediator, A', in the mass range 160-230 MeV decaying to electron-positron pairs with statistics corresponding to the signal sensitivity on the level of coupling constant 10$^{\mathrm{-9}}$. We will present the results on the magnetic optics for accurate reconstruction of the particle momenta for the APEX configuration of the High Resolution Spectrometers (HRS) with a septum magnet. Preliminary results show that angular reconstruction could be accomplished with a precision of 0.5 msr or better.   

On Demand

Haloscopes search for dark matter axions via their conversion to photons in an applied magnetic field. The Haloscope at Yale Sensitive to Axion CDM (HAYSTAC) uses a copper cylindrical cavity with an off-axis tuning rod to resonantly enhance the converted photon signal. The lowest order transverse magnetic mode (the TM$_{010}$) is tuned to search over a range of potential axion masses. This process is complicated by other fundamental cavity modes which interfere with the TM$_{010}$ mode, reducing the achievable signal power and sensitivity. Current experiments tolerate these mode crossings, but the problem worsens at higher frequencies. Photonic Band Gap (PBG)-based resonators allow for the confinement of TM modes while eliminating unwanted modes. We have developed a tunable PBG resonator which eliminates transverse electric (TE) modes and tunes the TM$_{010}$ from 7.3 to 9.3 GHz. This work will present results from an improved prototype aluminum structure and will discuss ongoing research on future designs.   

Superconducting Microwave Cavities for the Axion Dark Matter Experiment (ADMX)

The Axion Dark Matter eXperiment (ADMX) searches for Axions, a hypothetical dark matter candidate, through conversion to photons in a high magnetic field that are subsequently detected within a resonant cavity. The rate that this detector is able to scan potential axion masses (or photon frequency) depends linearly on the cavity quality factor. Though Superconducting Radio Frequency cavities (SRF) have been shown to have several orders of magnitude higher quality factor than copper, their quality factors typically degrade in the high magnetic fields required for Axion detection. Type II superconducting thin films have shown the potential for improved quality factors beyond that of bulk superconductors in a high magnetic field. In this work, we present our progress on studying different superconducting cavity materials for future ADMX searches.   

Improving the search for axion dark matter with cavity arrays and squeezed vacuum for ADMX

The search for QCD axion dark matter with the Axion Dark Matter Experiment (ADMX) requires quantum-limited microwave detectors. Unfortunately, microwave signal power and noise scales unfavorably for detection of higher mass axion signals. Above 1 GHz, detection sensitivity is limited by intrinsic properties of resonant modes: signal power weakens for small-volume high frequency modes while vacuum shot noise increases with frequency. We approach these interrelated challenges by coherently adding signals from multiple resonant cavities, thereby increasing the overall detector volume. Furthermore, we develop Josephson parametric amplifiers to improve signal-to-noise beyond the standard quantum limit by driving multiple cavity systems with squeezed vacuum. These microwave engineering and quantum optics techniques address frequency scaling limitations of resonant detectors and will advance higher mass axion searches at accelerated scan rates.   

Searching for axion dark matter with the ADMX Sidecar cavity

The ADMX Sidecar system is an in-situ testbed for technologies which may be incorporated into future ADMX runs while also taking science data. This talk will detail the status of the current data run which comprises the first use of a ‘clamshell’ cavity in ADMX and the use of a near quantum limited Traveling Wave Parametric Amplifier (TWPA).   

Not Participating

There is compelling evidence for the existence of vast quantities of dark matter throughout the universe, however its identity remains a mystery. While weakly interacting massive particles (WIMPs) have been the focus of direct detection searches for several decades, there is growing interest in ultra-light, wave-like dark matter. The Dark Matter Radio (DM Radio) is a sensitive search for axion and hidden photon dark matter covering the peV to $\mu$eV mass range. The DM Radio Pathfinder is a proof-of-concept detector operating in a liquid helium bath. The detector consists of a superconducting, tunable lumped-element LC resonator with dc SQUID readout. The Pathfinder experiment has two main goals: to serve as a technology development platform for the full-sized cubic meter DM Radio, and to search a new portion of hidden photon parameter space. We present the design and preliminary data from the Pathfinder, which will search for hidden photon dark matter between 100 kHz and 10 MHz in its full scan.