Status of the ADMX and ADMX-HF experiments

The Axion Dark Matter eXperiment (ADMX) is in the midst of an upgrade to reduce its system noise temperature. ADMX-HF (High Frequency) is a second platform specifically designed for higher mass axions and will serve as an innovation test-bed. Both will be commissioning in 2013 and taking data shortly thereafter. The principle of the experiment, current experimental limits and the status of the ADMX/ADMX-HF program will be described. R&D on hybrid superconducting cavities will be discussed as one example of an innovation to greatly enhance sensitivity.Comment: 4 pages, 3 figures, Contribution to the 8th Patras Workshop on Axions, WIMPs and WISPs, Chicago, IL, USA, 201

Characterization of the HAYSTAC axion dark matter search cavity using microwave measurement and simulation techniques

Many searches for axion cold dark matter rely on the use of tunable electromagnetic resonators. Current detectors operate at or near microwave frequencies and use cylindrical cavities with cylindrical tuning rods. The cavity performance strongly impacts the signal power of the detector, which is expected to be very small even under optimal conditions. There is strong motivation to characterize these microwave cavities and improve their performance in order to maximize the achievable signal power. We present the results of a study characterizing the HAYSTAC (Haloscope At Yale Sensitive to Axion Cold dark matter) cavity using bead perturbation measurements and detailed 3D electromagnetic simulations. This is the first use of bead perturbation methods to characterize an axion haloscope cavity. In this study, we measured impacts of misalignments on the order of 0.001 in and demonstrated that the same impacts can be predicted using electromagnetic simulations. We also performed a detailed study of mode crossings and hybridization between the TM$_{010}$ mode used in operation and other cavity modes. This mixing limits the tuning range of the cavity that can be used during an axion search. By characterizing each mode crossing in detail, we show that some mode crossings are benign and are potentially still useful for data collection. The level of observed agreement between measurements and simulations demonstrates that finite element modeling can capture non-ideal cavity behavior and the impacts of very small imperfections. 3D electromagnetic simulations and bead perturbation measurements are standard tools in the microwave engineering community, but they have been underutilized in axion cavity design. This work demonstrates their potential to improve understanding of existing cavities and to optimize future designs.Comment: 22 pages, 8 figures The following article has been submitted to Review of Scientific Instruments. v2: added changes made during the review proces

Generation and search of axion-like light particle using intense crystalline field

Intense electric field $\sim 10^{10}-10^{11}$ V/cm in crystal has been known for a long time and has wide applications. We study the conversion of axion-like light particle and photon in the intense electric field in crystal. We find that the conversion of axion-like particle and photon happens for energy larger than keV range. We propose search of axion-like light particle using the intense crystalline field. We discuss the solar axion search experiment and a variety of shining-through-wall experiment using crystalline field. Due to the intense crystalline field which corresponds to magnetic field $\sim 10^4-10^5$ Tesla these experiments are very interesting. In particular these experiments can probe the mass range of axion-like particle from eV to keV.Comment: 3 figures, 5 pages, references added, publication versio

Analysis of single-photon and linear amplifier detectors for microwave cavity dark matter axion searches

We show that at higher frequencies, and thus higher axion masses, single-photon detectors become competitive and ultimately favored, when compared to quantum-limited linear amplifiers, as the detector technology in microwave cavity experimental searches for galactic halo dark matter axions. The cross-over point in this comparison is of order 10 GHz ($\sim 40\ \mu$eV), not far above the frequencies of current searches.Comment: 5 pages, 1 figure new version address comments receive

An x-ray detector using PIN photodiodes for the axion helioscope

An x-ray detector for a solar axion search was developed. The detector is operated at 60K in a cryostat of a superconducting magnet. Special care was paid to microphonic noise immunity and mechanical structure against thermal contraction. The detector consists of an array of PIN photodiodes and tailor made preamplifiers. The size of each PIN photodiode is $11\times 11\times 0.5\ {\rm mm^3}$ and 16 pieces are used for the detector. The detector consists of two parts, the front-end part being operated at a temperature of 60K and the main part in room temperature. Under these circumstances, the detector achieved 1.0 keV resolution in FWHM, 2.5 keV threshold and 6\times 10^{-5} counts sec^{-1} keV^{-1} cm^{-2} background level.Comment: 8 pages, 5 figures, submitted to Nucl. Instr. Meth.