The Dark Matter Radio. Kent Irwin for the DM Radio Collaboration. DM Radio Pathfinder

Transcription

1 The Dark Matter Radio Kent Irwin for the DM Radio Collaboration DM Radio Pathfinder

2 Outline Field-like dark matter: axions and hidden photons Fundamental limits on the detection of axions and hidden photons through coupling to electromagnetism Optimal impedance-matching (Broadband? One-pole resonator? Multi-pole?) Optimal coupling to quantum-limited amplifier Optimal scan strategy given different priors (QCD, neutral, etc.) Science reach of electromagnetic searches for axions and hidden photons Extension to photon counting and non-classical measurements The Dark Matter Radio (DM Radio) Design Status of Pathfinder experiment Science reach and plans for Stage II and Stage III

3 Particle-like and field-like dark matter Heavy Particles Number density is small (small occupation) Tiny wavelength No detector-scale coherence Look for scattering of individual particles Light Fields Number density is large (must be bosons) Long wavelength Coherent within detector Look for classical, oscillating background field Detector Detector 3

4 Dark matter candidate: axion (spin 0) Strong CP Problem axion g a photon Neutron Electric Dipole Moment Why is it so small? Solution: is a dynamical field (Peccei-Quinn solution, the axion) Can be detected via inverse Primakoff effect coupling to electromagnetism Frequency: = Bandwidth: ~10 dc magnetic field ADMX Leslie J Rosenberg PNAS 2015;112:

5 Hidden photon: generic vector boson (spin 1) A new photon, but with a mass, and weak coupling Couples to ordinary electromagnetism via kinetic mixing Vector dark matter can be generated in observed dark matter abundance by inflationary fluctuations P. Graham et al., Vector Dark Matter from Inflationary Fluctuations, arxiv: Frequency: = / Bandwidth: ~10 (oscillating E field) CMB photon Hidden Photon DM Hidden photon DM drives EM currents

6 Axions: plenty of room at the bottom f = m a /2 khz MHz GHz THz CAST g [GeV -1 ] SN 1987a -ray Wide range of unexplored parameter space ADMX Axion Haloscopes QCD axion pev nev ev mev m a 6

7 Hidden photons: plenty of room at the bottom f = m ' /2 khz MHz GHz THz 10-6 CMB ( ') precision EM stellar production Wide range of unexplored parameter space CMB ( ' ) ADMX Axion Haloscopes pev nev ev mev m ' 7

8 The fundamental limit on detection axions and hidden photons through electromagnetic coupling First: standard quantum limit measure both quadratures of the electromagnetic field. Minimum 1 photon of noise from Heisenberg Also include thermal noise associated with residual dissipation in practical measurement (~ 1 m 3 volume at ~10 mk ) What is the limit on the science reach set by the optimal impedance and noise match to a quantum-limited amplifier? What is the fundamental limit on coupling to the dark matter field? What is the optimal scan strategy with different priors (QCD, neutral, etc.)? Paper: Chaudhuri et al., Oct. 19, 2017 Extension: photon counting and non-classical measurements of field (squeezing, entanglement) with the above machinery

9 Resonant conversion of axions into photons Pierre Sikivie (1983) Primakoff Conversion Amplifier Expected Signal Magnet Power ~ 10 6 Cavity ADMX experiment Frequency Thanks to John Clarke

10 Idea for subwavelength, lumped-element experiment Workshop Axions 2010, U. Florida, 2010

11 Also: Sikivie, P., N. Sullivan, and D. B. Tanner. "Physical review letters (2014): Also useful for hidden photons: Arias et al., arxiv: Chaudhuri et al., arxiv: v2 Workshop Axions 2010, U. Florida, 2010

12 Model for electromagnetic axion / hidden photon detector SIGNAL SOURCE 1) Inductive/capacitive element coupling to dark matter 2) Residual loss and associated thermal noise 3) Zero-point fluctuation noise MATCHING NETWORK Examples: 1) Single-pole LC resonator 2) Broadband inductive 3) Multi-pole resonator READOUT Amplifier or photon counter ( Phase-insensitive amplifier must add imprecision noise / backaction ) Standard Quantum Limit (SQL): Heisenberg uncertainty when both quadratures of the field are measured. Manifests in: vacuum noise, imprecision noise, backaction. Can do better with photon counting or non-classical states (squeezing, entanglement)

13 Scattering mode impedance matching Imag e of new JPA 10 m Castellanos-Beltran et al., Nature Physics (2008). Parametric amplifier with 0.04 photons of added noise. (similar devices deployed in HAYSTAC) Equivalent circuit model for resonant detector in scattering mode. Resonator tuned by changing capacitance. HEMT, resonant dc SQUID, parametric amplifier (used in ADMX/HAYSTAC) How well can the output impedance of the resonator be matched to the input/noise impedance of the amplifier?

14 Op-amp mode impedance matching Scanned, one-pole resonant RLC input circuit read out by SQUID. (e.g. ADMX, Haystac) Broadband LR circuit. (Kahn et al, PRL 117, (2016) ) Can we do better with a more complex (multipole) matching structure? dc SQUID: op-amp mode flux amplifier

15 Figure of merit for integrated sensitivity Maximize integrated sensitivity across search band, between l and h Figure of merit for scattering system with quantum-limited amplifier: = + 1 n( )= cavity thermal occupation number, 1 is standard quantum limit Includes vacuum noise, amplifier imprecision noise and backaction Similar calculation for op-amp mode Resonator bandwidth Sensitivity bandwidth Resonator line shape/ Thermal noise Amplifier noise floor Example: One-pole LC resonator output noise spectrum. Figure of merit integrates sensitivity at all relevant frequencies. There is significant information outside of the resonator bandwidth, depending on amplifier noise floor.

16 One-pole scanned resonator vs. broadband Ratio of minimum detectable coupling for one-pole resonant resonant (R) and broadband (B) plotted vs rest mass frequency. Value < 1 implies resonator limit stronger than broadband limit Apples-to-apples Assumes same volume, cavity temperature 10 mk. Assumes optimally matched amplifier at standard quantum limit. Assumes optimal scan strategy (not described in this talk). Assumes same total integration time over full science bandwidth. One-pole resonator is better at all frequencies where a resonator can be practically constructed (>~100 Hz) But a one-pole resonator is not optimal.

17 Bode-Fano Limit on Impedance Match A one-pole resonator is always more sensitive than a broadband measurement when it can be built. But a multi-pole resonator can be better still. How much better? Constraint provided by Bode-Fano criterion for matching LR to a quantum-limited amplifier with a real noise impedance: Bode-Fano 1 2 Bode-Fanolimited U 1 ( ), ( ) , ( ) 1 An optimal single-pole resonator can have a figure of merit U that is ~75% of the fundamental limit of a multi-pole circuit (pretty good!)

18 Dark Matter Radio science: axions FREQUENCY AXION-PHOTON COUPLING MASS

19 Dark Matter Radio science: hidden photons FREQUENCY HIDDEN PHOTON-PHOTON MIXING ANGLE MASS

20 Stanford: Arran Phipps, Dale Li, Saptarshi Chaudhuri, Peter Graham, Jeremy Mardon, Hsiao-Mei Cho, Stephen Kuenstner, Carl Dawson, Richard Mule, Max Silva-Feaver, Zach Steffen, Betty Young, Sarah Church, Kent Irwin Berkeley: Surjeet Rajendran Collaborators on DM Radio extensions: Tony Tyson, UC Davis Lyman Page, Princeton

21 Distance Coherence E Coherence freq 0 km 3 km 300 nev 70 MHz 40 km 20 nev 5 MHz 120 km 7 nev 2 MHz 5,000 km 0.2 nev 40 khz Stanford: Arran Phipps, Dale Li, Saptarshi Chaudhuri, Peter Graham, Jeremy Mardon, Hsiao-Mei Cho, Stephen Kuenstner, Carl Dawson, Richard Mule, Max Silva-Feaver, Zach Steffen, Betty Young, Sarah Church, Kent Irwin Berkeley: Surjeet Rajendran Collaborators on DM Radio extensions: Tony Tyson, UC Davis Lyman Page, Princeton

22 Block EMI background with a superconducting shield Superconducting shield Cross-section In the subwavelength limit of DM Radio, you can approximate the signal from axions and hidden photons as an effective stiff ac current filling all space, with frequency f = mc 2 /h (the interaction basis ) To detect this signal, we need to block out ordinary photons with a superconducting shield Hollow, superconducting sheath (like a hollow donut) 22

23 Field from effective axion current Top-Down Cross-section Toroidal coil produces DC magnetic field inside superconducting cylinder (B 0 toroid inside cylinder) Axions interact with DC field, generates effective AC current along direction of applied field 23

24 One-pole resonator implementation: axion Add a tunable lumpedelement resonator to ring up the magnetic fields sourced by local dark matter Tune DM Radio over frequency with insertible dielectric (sapphire) 24

25 Field from effective hidden photon current Hidden photon effective ac current penetrates superconductors 25

26 One-pole resonator implementation: hidden photon Add a tunable lumpedelement resonator to ring up the magnetic fields sourced by local dark matter Tune DM Radio over frequency with insertible dielectric (sapphire) 26

27 DM Radio Pathfinder science reach FREQUENCY HIDDEN PHOTON-PHOTON MIXING ANGLE MASS

28 DM Radio pathfinder experiment 4K Dip Probe Inserts into Cryoperm-lined helium dewar 750 ml Pathfinder now being tested T=4K (Helium Dip Probe) Frequency/Mass Range: 100 khz 10 MHz 500 pev 50 nev Detector inside superconducting shield 67 inches Coupling Range : Readout: DC SQUIDs 9.5 inches Design Overview of the DM Radio Pathfinder Experiment M. Silva, arxiv: ,

29 Toroidal Nb sheath and parallel-plate capacitors 29

30 Nb shield & SQUID amplifier 30

31 DM Radio pathfinder 31

32 DM Radio Pathfinder 32

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35 Superconducting toroidal sheath, superconducting shield, SQUID amplifier, capacitors, probe, electronics, shield, cryogenics: all in place. Broadband cryogenic operation verified: low SQUID noise, very good control over EMI within shield. Now: winding inductors, testing fixed resonators to evaluate Q, material properties. Finite element modeling of probe to determine constraints on coupling. Next: connect tunable dielectric and scan. DM Radio status Support for initial construction of Stage 2 (30 L experiment in dilution refrigerator) from Heising-Simons foundation. Stage 3 full science experiment (~1 m 3 ) in planning stage 35

36 Conclusions 36

37 Conclusions Axions Hidden Photons 37

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39 The dark matter zoo DM mass: Light (field) DM Spin-0 scalar Spin-1 vector Higher spin (tensor) disfavored Heavy (particle) DM WIMPs Etc. etc. Light-field dark matter is a boson 1. Scalar field (spin-0) 2. Pseudoscalar (spin-0, but changes sign under parity inversion) axion 3. Vector (spin-1): hidden photon 4. Pseudovector (spin-1, but changes sign on parity inversion)

40 How to measure effective hidden photon current Hidden photon effective ac current penetrates superconductors Generates a REAL circumferential, quasistatic B-field Screening currents on superconductor surface flow to cancel field in bulk Meissner Effect 40

41 How to measure effective hidden photon current Cut concentric slit at bottom of cylinder Screening currents return on outer surface 41

42 How to measure effective hidden photon current Cut concentric slit at bottom of cylinder Screening currents return on outer surface Add an inductive loop to couple some of the screening current to SQUID 42

43 How to measure effective axion current Toroidal coil produces DC magnetic field inside superconducting cylinder Axions interact with DC field, generates effective AC current along direction of applied field Produces REAL quasi-static AC magnetic field 43

44 How to measure effective axion current Screening currents in superconductor flow to cancel field in bulk Meissner Effect 44

45 How to measure effective axion current Cut a slit from top to bottom of the superconducting cylinder Screening currents continue along outer surface 45

46 How to measure effective axion current Cut a slit from top to bottom of the superconducting cylinder Screening currents continue along outer surface Use inductive loop to couple screening current to SQUID 46