Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session Q11: Axions |
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Sponsoring Units: DPF Chair: Karl van Bibber, University of California, Berkeley Room: Governor's Square 17 |
Monday, April 15, 2013 10:45AM - 10:57AM |
Q11.00001: Status and Overview of The Axion Dark Matter Experiment (ADMX) Gray Rybka The axion is a hypothetical particle that could both explain why the strong force is CP invariant and also account for the cold dark matter in the universe. ADMX is a direct search for dark-matter axions by their resonant conversion into photons in a microwave cavity permeated by a magnetic field, and amplified by quantum-limited amplifiers. An upgrade that will enable ADMX to be sensitive to axion models even with the most pessimistic axion-photon couplings is nearly complete. An overview of ADMX and the status of the upgrade will be presented. [Preview Abstract] |
Monday, April 15, 2013 10:57AM - 11:09AM |
Q11.00002: Construction of the Axion Dark Matter Experiment (ADMX) Upgrade Dmitry Lyapustin Axions are hypothetical elementary particles that may help provide the answer as to why QCD preserves the discrete symmetries P and CP. Light axions also have properties that make them ideal dark-matter candidates. The Axion Dark Matter eXperiment (ADMX), has been at the forefront of the search for dark-matter axions for over a decade, and is currently being upgraded to dramatically improve its sensitivity. 2013 is a particularly exciting year for ADMX as construction is nearly complete and we will soon move to commissioning followed by data-taking in the summer. I will begin by motivating the existence of axions, then discuss ADMX and its previous results, and highlight the improvements that have been made to the latest phase of ADMX. [Preview Abstract] |
Monday, April 15, 2013 11:09AM - 11:21AM |
Q11.00003: The ADMX ultra-low noise receiver Christian Boutan The Axion Dark Matter eXperiment (ADMX) searches for dark-matter axions by looking for their resonant conversion to microwave photons in a strong magnetic field. Given the current experimental setup the axion-photon conversion power is expected to be below a yoctowatt. Detecting such feeble signals above the thermal and electronic noise background requires a very sensitive microwave receiver. To ensure a fully characterized data pipeline, synthetic axion waveforms are simulated and periodically injected through the cavity and receiver chain. Here I discuss the calibration of the ADMX receiver and real-time analysis performed by the DAQ. [Preview Abstract] |
Monday, April 15, 2013 11:21AM - 11:33AM |
Q11.00004: Galactic-halo motivated searches for dark-matter axions with ADMX Michael Hotz Axions are a compelling cold-dark matter candidate, and the Axion Dark Matter eXperiment (ADMX) is the most sensitive detector for an axion component of the Milky Way's dark-matter halo. It may well be that our Milky Way's dark-matter halo is richer and more complicated than the isothermal-sphere approximation assumed in the majority of direct dark-matter searches. These richer, more complicated halo models, as an a priori within the ADMX analysis, could perhaps increase the experiment sensitivity. In this talk I discuss these more complicated halo models and their effect on the ADMX analysis. Some of these halo models include the ``caustic ring'' and ``dark-disk'' halos. [Preview Abstract] |
Monday, April 15, 2013 11:33AM - 11:45AM |
Q11.00005: A variable-resolution search for non-virialized halo axions J. Hoskins Flows of non-thermalized halo axion dark matter would be characterized by very low velocity dispersion and perhaps a higher than average local density. The Axion Dark Matter eXperiment (ADMX) High Resolution (HR) Channel searches for these flows by converting the axions into microwave photons and looking for a peak in the power spectrum with spectral broadening of order 1 Hz or lower. With a resolution as fine as 40 mHz, the HR Channel would be sensitive to such a population of axions. Performing searches at different resolutions permits axion density limits to be placed on flows of varying dispersions. Here we present preliminary results for a range of sub-hertz resolution searches in the 800 MHz range (3.3 micro-eV). [Preview Abstract] |
Monday, April 15, 2013 11:45AM - 11:57AM |
Q11.00006: The ADMX-HF (High Frequency) Experiment K.W. Lehnert For many years, the Axion Dark Matter eXperiment (ADMX) has searched for dark-matter axions by their resonant conversion to photons in a high-Q microwave cavity embedded in a strong magnetic field; to date focusing on the $\sim$1 GHz range, or $m_a\sim$ few micro-eV. A second platform, ADMX-HF is now being constructed at Yale University which will focus on technology development and a first look at data in the $\sim$10 GHz range. Consisting of a 9T superconducting magnet (40~cm long x 14~cm diameter), a dilution refrigerator and a quantum-limited receiver based on Josephson Parametric Amplifiers (JPA) ADMX-HF is projected to achieve sensitivity within the axion model band, despite its smaller volume than ADMX. ADMX-HF is a collaboration of Yale, JILA/Colorado, UC Berkeley and LLNL, and by agreement will create a unified data set with ADMX. [Preview Abstract] |
Monday, April 15, 2013 11:57AM - 12:09PM |
Q11.00007: A Josephson Parametric Amplifier (JPA) for the ADMX-HF Experiment Mehmet Ali Anil ADMX-HF is a second experimental ADMX platform being built up at Yale University, specifically designed as a test-bed for new concepts and data-taking at higher frequencies, and thus masses, in the search for dark-matter axions. In its first generation ADMX-HF will operate with a microwave cavity tunable between 4 and 8 GHz. In this frequency band, Josephson Parametric Amplifiers (JPA) recently developed at the University of Colorado provide quantum-limited microwave amplification, critical for detecting the weak signal associated with axion to photon conversion. These amplifiers are particularly well suited to ADMX-HF because they have a bandwidth well matched to the width of the cavity resonance and this band is tunable with magnetic field over the 4 to 8 GHz band of the axion cavity. For these reasons, the Colorado amplifiers will be deployed in ADMX-HF. In this talk, we will describe the operation of these amplifiers and the technical challenges associated with deploying them in ADMX-HF. [Preview Abstract] |
Monday, April 15, 2013 12:09PM - 12:21PM |
Q11.00008: Progress towards a Hybrid Superconducting Microwave Cavity for ADMX Gianpaolo Carosi Dark-matter axions can be detected by their resonant conversion into photons using microwave resonant cavities in an axial magnetic field. This is the basis of both the ADMX and ADMX-HF experiments currently under construction. The axion-photon conversion power is directly related to the quality factor (Q) of the microwave cavity used. To date copper cavities have been used with Q $\sim 10^5$ at frequencies of 1 GHz. However, superconducting cavities can regularly be made with Q $> 10^9$. Here we describe progress of R\&D efforts to make hybrid cavities with a superconducting barrel and normal copper end-caps that can maintain their superconducting properties and an enhanced Q in a magnetic field. [Preview Abstract] |
Monday, April 15, 2013 12:21PM - 12:33PM |
Q11.00009: Results of a High-Frequency Resonant Cavity Design Study for ADMX I. Stern The Axion Dark Matter eXperiment (ADMX) has conducted axion searches in the mass range of 1.9--3.6 $\mu $eV (460--860 MHz). A design study for large volume high-frequency resonant cavities was performed to enable further exploration of axions at frequencies \textgreater 1 GHz. Two frequency-increasing tuning techniques, photonic band-gap resonators and multi-vane tuning configurations, were investigated. Photonic band-gap resonators consist of an array of tuning posts in a regular pattern that are manipulated to vary the TM modes (the only modes that interact with the axion). The multi-vane tuning method rotates radially-oriented vanes to partition the cavity into regions which mimics the mode response of strongly coupled segmented cavities. The study compares the dynamic frequency tuning range, mode form factor, and cavity quality factor ($Q)$ of various designs. Findings of the study will be presented. [Preview Abstract] |
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