Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session J2: Dark Matter IV |
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Sponsoring Units: DPF DNP Chair: Aaron Roodman, SLAC National Accelerator Laboratory Room: Holiday 1 |
Sunday, April 12, 2015 10:45AM - 10:57AM |
J2.00001: ADMX overview and new limits on axion mass 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 over the past few years has undergone~upgrades to dramatically improve its sensitivity. 2014 was a particularly exciting year for ADMX as we collected the first production data from this new generation of the experiment.~I will discuss the data set, go over the analysis method, and present new exclusion limits on the axion mass. [Preview Abstract] |
Sunday, April 12, 2015 10:57AM - 11:09AM |
J2.00002: Status of the Axion Dark Matter Experiment -- High Frequency (ADMX-HF) Benjamin Brubaker The axion is a well-motivated cold dark matter candidate first postulated to explain the absence of CP violation in strong interactions. Dark matter axions may be detected via their resonant conversion into photons in a high-$Q$ microwave cavity permeated by a strong magnetic field. The Axion Dark Matter eXperiment (ADMX) has used this technique to exclude axion models in the few $\mu$eV mass range. Much of axion dark matter parameter space has until recently been beyond the reach of experiment, but advances in amplifier technology have enabled quantum-limited axion detection around 20~$\mu$eV (5~GHz). ADMX-HF (high-frequency) at Yale, which recently took its first data, will have sufficient sensitivity to probe this region of parameter space. This talk will discuss the design, current status, and projected sensitivity of ADMX-HF, which serves as both an innovation test bed and a pathfinder search at high frequencies. [Preview Abstract] |
Sunday, April 12, 2015 11:09AM - 11:21AM |
J2.00003: The ADMX Site and Dilution Refrigerator James Sloan The ADMX experiment searches for axions by looking for their resonant conversion to detectable photons with a frequency that directly corresponds to the axion mass (a currently unknown value). Fundamentally, the RF photon detection is relatively straightforward; the exceptional technical challenge of ADMX is achieving the sensitivity required to discern the extremely weak ($\sim$10$^{-22}$W) photon signal above the system noise. Greater sensitivity is achieved by either lowering the physical and amplifier noise or by integrating for longer time over a given frequency range. Noise temperatures approaching the quantum limit are achieved by operating quantum electronics, SQUIDs and JPAs, at very low physical temperatures. In the past ADMX has achieved $\sim$1.5K physical temperatures by operating with pumped $^{4}$He. The addition of a $^{3}$He/$^{4}$He dilution refrigerator into ADMX will lower the physical temperatures to $\sim$100mK, dramatically increasing the scan rate and sensitivity. I will discuss the site and hardware modifications to ADMX to accommodate the dilution refrigerator and will report on the commissioning operations of the dilution refrigerator. [Preview Abstract] |
Sunday, April 12, 2015 11:21AM - 11:33AM |
J2.00004: Improved tunable microstrip SQUID amplifiers for the Axion Dark Matter eXperiment Sean O'Kelley, J{\O}rn Hansen, Gene Hilton, Jan-Michael Mol, John Clarke We describe a series of tunable microstrip SQUID (Superconducting QUantum Interference Device) amplifiers (MSAs) used as the photon detector in the Axion Dark Matter eXperiment (ADMX). Cooled to 100mK or lower, an optimized MSA approaches the quantum limit of detection. The axion dark matter candidate would be detected via Primakoff conversion to a microwave photon in a high-Q ($\approx $ 10$^{\mathrm{5}})$ tunable microwave cavity, cooled to 1.6 K or lower, in the presence of a 7-tesla magnetic field. The MSA consists of a square loop of thin Nb film, incorporating two resistively shunted Josephson tunnel junctions biased to the voltage state, flux-coupled to a resonant microstrip. The photon frequency is determined by the unknown axion mass, so the cavity and amplifier must be tunable over a broad frequency range. MSA tunability is achieved by terminating the microstrip with a GaAs varactor diode that operates at cryogenic temperatures. This voltage-controlled capacitance enables us to vary the resonant microstrip mode from nearly $\lambda $/2 to $\lambda $/4. We demonstrate gains exceeding 20 dB, at frequencies above 900 MHz. With proper design of the microwave environment, a noise temperature of 1/2 to 1/4 of the physical temperature is demonstrated. [Preview Abstract] |
Sunday, April 12, 2015 11:33AM - 11:45AM |
J2.00005: The ADMX Sidecar cavity and receiver-chain~ 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. If ADMX rules out axions in the 500MHz - 2GHz frequency range, new technologies and cavity geometries will need to be explored to find higher mass axions. ADMX Sidecar is a higher frequency pathfinder experiment that uses a miniature resonant cavity to search for axions in the 2 GHz - 10 GHz frequency range. The Sidecar cavity shares the magnetic field and cryogenics of the main experiment but the data pipeline and receiver-chain are new and independent of the existing infrastructure. Unlike the main experiment, which uses gear-boxes and fiberglass shafts to translate the motion of room temperature motors into the cryogenic space, piezoelectric motors are used to adjust the Sidecar tuning rod position and antenna depth. Here I discuss the design, construction and status of ADMX Sidecar. [Preview Abstract] |
Sunday, April 12, 2015 11:45AM - 11:57AM |
J2.00006: ADMX Microwave Cavity R{\&}D Status Ian Stern The Axion Dark Matter eXperiment (ADMX), a direct-detection axion search, has begun taking data with a redesigned system. Earlier phases conducted axion searches in the mass range of 1.9-3.5 $\mu $eV (460-850 MHz) setting upper limits below the theoretical KSVZ coupling strength of the axion to two photons. The current upgrades will allow ADMX to detect axions with even the most pessimistic (DFSZ) couplings in this frequency range. In order to expand the mass reach of the detector, ADMX is conducting extensive research and development of microwave cavities. Prototype development programs include photonic band-gaps, multi-vane cavities, partitioned cavities, in-phase coupled cavities, and superconducting hybrid cavities. Additional studies include techniques for mode detection and mode-crossing suppression, and strategic planning. The various projects are in different phases of analysis, fabrication, and/or testing. The current status and near term objectives will be presented. [Preview Abstract] |
Sunday, April 12, 2015 11:57AM - 12:09PM |
J2.00007: Active Resonators for ADMX Ana Malagon The Axion Dark Matter experiment (ADMX) searches for dark matter axion particles converting into detectable photons in a microwave resonator immersed in a strong magnetic field. Here we will discuss a recently proposed technique to use active feedback in resonators as a way to increase the sensitivity of dark matter axion searches. We will briefly overview the theoretical motivation for axions and the current experimental setup of ADMX, then describe the principles of the active feedback system. Finally, we will discuss an active resonator prototype which demonstrates the improvement in signal to noise ratio. [Preview Abstract] |
Sunday, April 12, 2015 12:09PM - 12:21PM |
J2.00008: ABSTRACT WITHDRAWN |
Sunday, April 12, 2015 12:21PM - 12:33PM |
J2.00009: ABSTRACT WITHDRAWN |
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