Gray Rybka- ADMX's Ongoing Search for Dark Matter Axions

8/3/2019 Gray Rybka- ADMX's Ongoing Search for Dark Matter Axions

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ADMX's Ongoing Searchfor Dark Matter Axions

Gray RybkaUniversity of Washington

Patras Workshop on Axions, WIMPS and WISPsJuly 15, 2009

Durham


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2Gray Rybka Patras Workshop on Axions, WIMPS and WISPS, Durham July 2009

ADMX

Axion Dark Matter eXperimentUniversity of Washington

LLNLUniversity of Florida

UC BerkeleyNRAO

Sheffield University

1) Axion & Dark Matter Review2) ADMX Phase 1 Technology

3) Science Results4) Future Plans


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Axion Vocabulary Review

Axion neutral pseudoscalar particle invented toexplain why QCD is CP-invariant

Axion Mass (ma) single free parameter in

standard axion (~1/fa)

Axion-Photon Coupling (ga) experimentallyaccessible coupling. Mostly fixed by ma.

ga

Peccei, Quinn, Weinberg, Wilczek, etc.


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Axions as Dark Matter

When Peccei-Quinn symmetry is broken, a large numberof axions are produced. (Vacuum misalignment mechanism)

With the right conditions, this makes enough Axions toaccount for dark matter

ma1 meV

Disfavored

by SN1987a

CAST, stellarlimits

Dark MatterSweet Spot


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Prior Dark Matter Axion Limits

ADMX1996 -

2004

ADMX 1996-2004 showedthat we have the sensitivityneeded for axion dark matter

Only a small region of

phase space hasyet been covered

ADMX Phase 1 (2007-2009)Goals:

1) Develop technology to coverDM axion sweet spot quickly2) Expand current limits onaxions


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Dark Matter Axion Cavity Experiments

You Want:-Large Cavity Volume-High Magnetic Field-High Cavity Q

You Don't Want:-High Thermal Noise-High Amplifier Noise

Dark Matter Axions will convertto photons in a magnetic field.

The measurement is enhanced if thephotons frequency correspond to

the cavity's resonant frequency.Sikivie - 1983


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ADMX Design

Cavity Frequency changed by movingmetal rods (not shown) inside cavity

4m


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ADMX Phase 1 New Technology

Field compensation

magnet for SQUIDsSQUID amplifier

The SQUID allows us to lower ournoise temperature (scan faster)

The compensation coil is necessaryfor the SQUID to function


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SQUID Amplifiers

A SQUID converts a magneticflux into a voltage

Over a small range of flux, itacts as an amplifier

The ADMX SQUID uses a microstripresonator to provide the flux, and is thehighest frequency SQUID to date


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The ADMX SQUID

The ADMX SQUID is all about lowering the noise temperature

With the SQUID, noise is limited only by physical temperature(down to 50 mK)

Semiconductor Limit: 2 K

Phase 1 Amplifier (Now)Noise Temperature: 1K

SQUID limit: 50 mK(Planned)


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Technological Performance

The Magnet Ramps up...

The Compensation CoilCancels the Field...

And the SQUIDstill works!

Magnetic Field vs. Time

Field at SQUID vs. Time

Power Spectrum


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Axions to Power Spectra

SQUID

FrequencyMixer

FrequencyMixer

Po

werRods are moved to tune

mass sensitivity


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Data Analysis

Take a 20 KHz scanEvery 90 Seconds

Raw Power Spectrum Receiver Effects Removed

Combine scans into10 MHz nibble

Rescan low SNR areasand candidate axionsEvery week


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What do Axions Look Like?

Sample Axion:

ma=3.48 eV

KSVZ (Qem=1)

dm 0.4 GeV/cm

3

vdisp=220 km/s

vrel=220 km/s


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What Else Looks Like an Axion?


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Current ADMX Phase 1 Sensitivity

Mode crossing

Continued Scanningthrough Fall 2009


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Aside: Chameleons

Chameleon -Chameleon - Scalar or Pseudoscalar that couples tolocal energy density

Interesting property: Mass depends on density of

material around it

Could be important for Dark Energy.

See P. Brax's talk tomorrow for more

Especially interesting: can be trapped inside cavities


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Aside: Chameleons in ADMX

Excite TE011

E&M Mode

in Cavity

E&M mode exciteschameleon mode

Chameleon modedecays back into E&M mode

PowerIn

PowerOut

Turnoff

power

Wait

With the right couplings, ADMX can see chameleon afterglow effect

Expected: Good coupling sensitivity over small mass rangeAnalysis in progress


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What's Next for ADMX?

ADMX Phase 2 Goal

Explore all reasonable dark matter axion models from 1ev to 10eV

How?

Dilution Refrigeratorallows us to reach temperaturesof 50 mK (We're at ~2 K now)

10 times lower temperature= 100 times faster scan speed

-or-10 times faster scan +10 times more sensitiveto ga

1-10 eV coveredin half a year insteadof 50 years


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ADMX Phase 2 and Beyond

Phase 2 will exploredark matter axions in thelowest decade of

plausible mass.

Ideas are in the worksto cover the next twodecades

Dark matter axionscannot hide forever...


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Conclusions

ADMX Phase 1 will expand Dark Matter axionlimits by 0.5 eV

We have demonstrated the functionality of the

SQUID needed to continue to Phase 2 ADMX Phase 2 (2012) will be able to explore

even pessimistic dark matter axion models overa large mass range.

Documents

Gray Rybka- ADMX's Ongoing Search for Dark Matter Axions