Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session K16: Axions at ADMX |
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Sponsoring Units: DPF Chair: Kevork N. Abazajian, Univ of California, Irvine Room: 251D |
Sunday, April 17, 2016 1:30PM - 1:42PM |
K16.00001: Hunting for axion dark matter with the ADMX project Gianpaolo Carosi The axion is a hypothetical particle that explains why the strong force is CP invariant and could also account for the cold dark matter in the universe. The Axion Dark Matter eXperiment (ADMX) directly searches for dark-matter axions by looking for their resonant conversion into detectable photons in a microwave cavity permeated by a strong magnetic field. This experiment, currently a “Generation 2” DOE Dark Matter Project, is now preparing for operations with enough sensitivity to either detect the "QCD axion" or reject that hypothesis at high confidence over a large range of potential axion masses. This talk will give an overview of the ADMX project and technology, its search plan and some of the various R\&D projects that are being undertaken to extend its sensitivity. [Preview Abstract] |
Sunday, April 17, 2016 1:42PM - 1:54PM |
K16.00002: The Axion Dark Matter eXperiment Cryogenic System Hannah LeTourneau The Axion Dark Matter eXperiment (ADMX) searches for dark matter axions by looking for their resonant conversion to photons in a microwave cavity in a high magnetic field. The mass of the axion (unknown) determines the frequency at which the axion couples to the magnetic field, so the cavity is tuned through a wide range of frequencies while measuring the power deposited in it with ultra-sensitive quantum electronics. The dominant systematic noise is from the noise temperature of the electronics; during the last data run they were cooled to 1.5K with a pumped He-4 refrigerator. Currently, we are installing a large dilution refrigerator, which will cool the cavity and first stage amplifiers to $\approx$100 mK. I will discuss our progress, describe some of the challenges we have faced and how we have overcome them, and describe our plans for operation. [Preview Abstract] |
Sunday, April 17, 2016 1:54PM - 2:06PM |
K16.00003: ADMX Receiver and Analysis Ana Malagon ADMX looks for the excess radiation deposited into a cavity from the conversion of a dark matter axion into a microwave photon. The sensitivity of the experiment increases by reducing the background thermal noise and minimizing the electronic noise of the readout system. The axion masses that the experiment can detect are determined by the resonant frequency of the cavity mode of interest, which is tuned using a two rod configuration. One can also increase the search rate by measuring the output from two cavity modes at once, which requires two separate readout schemes. I will discuss the ADMX dual-channel receiver which has been upgraded to have near quantum-limited sensitivity on both channels, and describe how the correct modes are verified, using simulations, in the presence of dense electromagnetic structure. I conclude by describing upgrades to the ADMX analysis which allow for real-time exclusion limits. [Preview Abstract] |
Sunday, April 17, 2016 2:06PM - 2:18PM |
K16.00004: Tunable microstrip SQUID amplifiers for the Gen 2 Axion Dark Matter eXperiment (ADMX) Sean O'Kelley, Gene Hilton, John Clarke We present a series of tunable microstrip SQUID (Superconducting Quantum Interference Device) amplifiers (MSAs) for installation in ADMX. The axion dark matter candidate is detected via Primakoff conversion to a microwave photon in a high-Q ($\approx $100,000) tunable microwave cavity cooled with a dilution refrigerator in a 7-tesla magnetic field. The microwave photon frequency $\nu $ is a function of the unknown axion mass, so both the cavity and amplifier must be scanned over a wide frequency range. An MSA is a linear, phase-preserving amplifier consisting of a square washer loop, fabricated from a thin Nb film, incorporating two Josephson tunnel junctions with resistive shunts to prevent hysteresis. The input is coupled via a microstrip made from a square Nb coil deposited over the washer with an intervening insulating layer. Tunability is achieved by terminating the microstrip with GaAs varactors that operate below 100 mK. By varying the varactor capacitance with a bias voltage, the resonant frequency is varied by up to a factor of 2. We demonstrate several devices operating below 100 mK, matched to the discrete operating bands of ADMX at frequencies ranging from 560 MHz to 1 GHz. The MSAs exhibit gains exceeding 20 dB and the associated noise temperatures, measured with a hot/cold load, approach the standard quantum limit ($h\mathrm{\nu }{/k}_{B})$. [Preview Abstract] |
Sunday, April 17, 2016 2:18PM - 2:30PM |
K16.00005: Searching for low mass axions with an LC-circuit N. Crisosto, P. Sikivie, N.S. Sullivan, D.B. Tanner Axions are a promising cold dark matter candidate. Axion haloscopes such as ADMX, which use the conversion of axions to photons in the presence of a magnetic field, are used to search for axions which decay into microwave photons. To search for lighter, low frequency axions in the unexplored sub 10$^7$ eV (50 MHz) range a tunable LC circuit has been proposed. Progress in the development of such an LC circuit based search will be presented. The use of both electrical and mechanical tuning mechanisms will be included. [Preview Abstract] |
Sunday, April 17, 2016 2:30PM - 2:42PM |
K16.00006: Status and Early Results from the Axion Dark Matter eXperiment - High Frequency (ADMX-HF) Samantha Lewis The axion was originally proposed as a solution to the Strong-CP problem of the Standard Model. A sufficiently light axion ($1-1000~ \mu$eV) also represents an excellent cold dark matter candidate. Such axions may be detected by their resonant conversion to photons in a high-$Q$ microwave cavity permeated by a strong magnetic field. Previous experiments have probed the first decade in mass using this method. ADMX-HF was designed and built as an innovation test-bed and a data pathfinder for the second decade in mass range. The experiment, initially configured with a 9-tesla magnet, dilution refrigerator, 2-liter tunable copper cavity, and a Josephson Parametric Amplifier, is now operational with a system noise temperature approximately twice the Standard Quantum Limit. Preliminary data in the $25~\mu$eV range (on the order of 6 GHz in resonant frequency) will be presented, as well as an overview of ongoing R\&D on new cavity and amplifier technologies that will be validated in situ within the next few years. [Preview Abstract] |
Sunday, April 17, 2016 2:42PM - 2:54PM |
K16.00007: Josephson parametric amplifiers for the ADMX-HF experiment Maxime Malnou, Daniel Palken, Gene Hilton, Leila Vale, Konrad Lehnert Dark matter search in the ADMX-HF experiment aims at detecting power generated by the axion-photon conversion, of a few hundred of yoctowatts, in the 4 -- 12 GHz band [1]. The sensitivity of detection directly depends on the amplifier noise temperature, and therefore requires state of the art microwave amplifiers. In contrast to amplifiers with dissipation on-chip, superconducting Josephson parametric amplifiers (JPA) reach and even circumvent the quantum limit. Over the past years, we have developed JPAs fabricated with arrays of superconducting quantum interference devices [2,3]. Their gain, bandwidth and tunability are particularly well suited for efficient amplification in the band of interest. In this talk we will present numerical modeling of the behavior of our amplifiers, along with the first results from new designs that cover the 4-12 GHz band. Finally, we will present the ongoing work to increase the gain-bandwidth product and gain stability of our amplifiers. References: [1] T. M. Shokair et al, Int. J. Mod. Phys. A 29, 1443004 (2014) [2] Castellanos-Beltran, M. A., et al. Nature Physics 4.12 (2008): 929-931 [3] Mallet, F., et al. Physical Review Letters 106.22 (2011): 220502 [Preview Abstract] |
Sunday, April 17, 2016 2:54PM - 3:06PM |
K16.00008: Microwave Cavity R\&D for ADMX-HF Maria Simanovskaia, Kelly Backes, Gianpaolo Carosi, Saad Kenany, Samantha Lewis, Jaben Root, Karl van Bibber Dark matter axions may be detected by their resonant conversion to photons in a tunable microwave cavity permeated by a strong magnetic field. The Axion Dark Matter eXperiment - High Frequency is both a test-bed for innovative cavity and amplifier concepts and a data pathfinder for the 5-25 GHz range. We are focusing on two major issues in the microwave cavity axion search. The first is increasing the cavity quality factor, Q, which enters linearly into the signal power and thus mass scan rate. Toward this end, we are developing a RF plasma deposition technique for making and characterizing superconducting NbTiN thin films. Multilayers of these thin films deposited on cylindrical surfaces of the microwave cavity may improve the Q by an order of magnitude. The second is applying Photonic Band Gap structures to make resonators of higher frequency and isolate the desired TM$_{010}$ mode. The density of mode crossings between the axion-coupling TM$_{010}$ mode and axion-noncoupling TE and TEM modes is the greatest limitation to the experiment's mass scan rate through loss of continuous frequency coverage. [Preview Abstract] |
Sunday, April 17, 2016 3:06PM - 3:18PM |
K16.00009: Enhancing the ADMX-HF Search Rate via Quantum Squeezing Daniel Palken, Maxime Malnou, Konrad Lehnert ADMX-HF seeks to detect dark matter axions in the 4-12 GHz band by reading out the state of a microwave cavity [1]. Utilizing a quantum-limited, phase-insensitive amplifier such as a Josephson Parametric Amplifier (JPA) [2] to read out both quadratures of the putative axion signal adds a full quantum of noise atop that signal. The two halves of that quantum are attributed to the noncommutation of the quadrature operators with the cavity Hamiltonian and with one another. We propose a method whereby both halves of this quantum may be circumvented. A JPA is used to create a squeezed microwave state and inject it into the axion cavity, whereupon an axion field, if present, displaces the squeezed state in phase space. The squeezed state then decays out of the cavity, and a second JPA is used for a phase-sensitive readout of only the squeezed quadrature of the field. A single quadrature measurement need not add noise [3], and, because the cavity field will be prepared in an approximate eigenstate of one quadrature operator, and not of its Hamiltonian, that half-quantum is averted as well. The limiting factor in this protocol will be the efficient transport of the squeezed microwave state between the JPAs and the axion cavity. We estimate that with currently achievable efficiency, we can increase the axion search rate by a factor of four. $\backslash $pard[1] T.M. Shokair et al., Int. J. Mod. Phys. A 29, 144304 (2014). 2] M.A. Castellanos-Beltran and K.W. Lehnert, Appl. Phys. Lett. 91, 083509 (2007). 3] C.M. Caves, Phys. Ref. D 26, 1817 (1982). [Preview Abstract] |
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