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The Future of Dark-Matter Axion Searches

The Future of Dark-Matter Axion Searches. Darin Kinion (LLNL/UC Berkeley) December 9, 2004. Axions and the Strong-CP Problem. Axion properties. The “axion window”. The parameter space is bounded both in mass and coupling constant. How to detect dark-matter axions (Sikivie, 1983).

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The Future of Dark-Matter Axion Searches

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  1. The Future of Dark-Matter Axion Searches Darin Kinion (LLNL/UC Berkeley) December 9, 2004

  2. Axions and the Strong-CP Problem

  3. Axion properties

  4. The “axion window” The parameter space is bounded both in mass and coupling constant.

  5. How to detect dark-matter axions (Sikivie, 1983)

  6. Axion Dark-Matter Experiment (ADMX) • Located at LLNL (Livermore, CA) • ADMX Collaboration – LLNL, UF, UCB and NRAO • Started data taking in February 1996.

  7. ADMX receiver and data candidates Data from 725 – 800 MHz world’s quietest radio receiver To date, all candidates have either disappeared upon re-scanning or have been linked to external interference

  8. Current ADMX limits Astrophysics Particle Physics ra»rhalo¼ 0.45 GeV/cm3 Definitive experiment requires relaxing the constraint on the axion halo density as well as achieving sensitivity to DFSZ model axions.

  9. 1.5 K pumped LHe 2.0 K GaAs HFET amp The ADMX upgrade plan Goal : Increase the sensitivity (scan rate) by lowering the system noise temperature Phase I – Improve TN with lower noise microwave amplifiers Phase II – Improve Ts with a dilution refrigerator

  10. Phase I Upgrade – SQUID Amplifiers

  11. Microstrip amplifiers

  12. Field-free region Field cancellation coil Force compensation coil Main Magnet 1K Pot Cavity 50 cm ADMX hardware design for Phase I Longitudinal field on axis

  13. Summary of ADMX • Current experiment is sensitive to KSVZ axions if they dominate the local galactic halo density • Phase I upgrade is underway to improve sensitivity by replacing GaAs HFET amps with SQUIDs. • Phase II upgrade would provide an order-of-magnitude improvement in sensitivity by cooling the cavity and SQUID to < 100 mK. • Long-term development plan involves higher-frequency cavities and amplifiers.

  14. Other axion searches • The Kyoto Rydberg Atom detector • The CERN Axion Solar Telescope CERN Sun

  15. CAST (projected) Summary of axion exclusion regions ADMX Upgrade

  16. Summary • The Peccei-Quinn mechanism remains the most compelling solution to the Strong-CP problem in QCD • ADMX is currently exploring the lowest decade of the axion window at KSVZ sensitivity • The goal of the two-phase ADMX upgrade is to cover the lowest two decades of the axion window with sensitivity to DFSZ axions comprising a fraction of the galactic halo

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