M Betz CERN Geneva M Gasior CERN Geneva F Caspers CERN Geneva M Thumm KIT Karlsruhe Gentner day 102011 CERN Geneva Outline Introduction to ID: 784093
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Slide1
Experimental searches for axion like particles
M. Betz
(CERN, Geneva)
M. Gasior (CERN, Geneva)F. Caspers (CERN, Geneva)M. Thumm (KIT, Karlsruhe)
Gentner
day
10/2011, CERN, Geneva
Slide2OutlineIntroduction to AxionsExisting experimental searches around the world
The “microwaves shining through the wall” experiment at CERN2What this talk will be about
M. Betz; Experimental searches for axion like particles, Geneva 2011
Slide3What is an axion?A hypothetical elementary particlePostulated by R. Peccei
, H. Quinn, S. Weinberg and F. Wilczek in 1977 – 1978 to explain the strong CP-violationA candidate for dark matter in our universeAlso a washing detergent
3Introduction
M. Betz; Experimental searches for axion like particles, Geneva 2011
Some propertiesCharge: NoneMass:
10-6 … > 100 eV/c²Mean lifetime: 1017
yearsNo interaction with matter!
Slide4The theory of quantum chromodynamics (QCD) is explicitly CP-violating if one of its parameters θ>0
θ was expected to be
of order 1
Puzzling questions for QCD-physicists:Why is the parameter θ so small? (Fine
tuning problem!)Why is there apparently no CP-violation?
What is an axion?4
The strong CP problemM. Betz; Experimental searches for axion like particles, Geneva 2011
The result was puzzlingCurrent experimental limit:
|dN| < 10
-27 e cm
Experimental verification
QCD neutrons should have an electrical dipole moment in the order of
|d
N
| ≈
θ
10
-16
e cm
Slide5What is an axion?What
if θ is a
dynamical variable?It
would oscillate around zero like a pendulum
This would eliminate CP violating terms from the QCD-LagrangianThe oscillations can be seen as new particle The axion
So far the most elegant and widely accepted solution to the strong CP-problemFor theoretical physics: Problem solved!But in experimental physics:No observation of the axion
yet5A solution to the strong CP problem
M. Betz; Experimental searches for axion like particles, Geneva 2011
From: Fermilab Seminar Ultrasensitive Searches for the Axion Karl van Bibber, LLNL January 30, 2008
Slide6What is an axion?6
Also a candidate for dark matterM. Betz; Experimental searches for axion like particles, Geneva 2011
Some puzzling question for astrophysicists:
Why do clusters of galaxies rotate faster on their outskirts than they should?Why does the cosmic microwave background radiation appear to be distorted?Why is the gravitational
lensing effect stronger than predicted?
All of those points could be explained by assuming there is more matter and energy in our universe than we can seeBut, what is this dark matter made of?
Axions are excellent candidates for dark matter
Note that axions could exist, even if the dark matter theory would be disproven
Slide7The Primakoff Effect7
Axions couple to photons in a strong magnetic fieldM. Betz; Experimental searches for axion like particles, Geneva 2011
From: Fermilab Seminar Ultrasensitive Searches for the Axion Karl van Bibber, LLNL January 30, 2008
* is representing the virtual photons of the magneto-static field
γ can be a photon with energies between μeV (microwave photon) and up to keV
and beyond(gamma quantum)a = axion
All current experimental searches are based on this effect
Slide8Experimental searches around the world
8OverviewM. Betz; Experimental searches for axion like particles, Geneva 2011
Experimental
searches for theaxionLooks for changes in light polarization of a laser beam in a strong magnetic fieldLooks for axions generated in the sun and sent to earth
Looks for dark matter axions, uniformly distributed in our galaxyLooks for photon axion photon conversions in a strong magnetic field
Slide9Laser polarization experimentsLinear polarized laser beam transverses strong magnetic fieldThe component parallel to the magnetic field is converted to hidden particles (primakoff
effect) selective absorptionThe polarization is rotated9
PVLAS (Istituto Nazionale di Fisica Nucleare, Padova, Italy)
M. Betz; Experimental searches for axion like particles, Geneva 2011
The expected effect is tiny
rotation of 3.9 · 10-12 rad≈ width of mechanical pencil leadat the distance of the Moon
Slide10Laser polarization experiments
In 2006 the PVLAS collaboration published their resultsThey claimed to have observed the effect they were looking for
After an update of the detector, the results could not be confirmed
10PVLAS (Istituto Nazionale di Fisica Nucleare, Padova, Italy)M. Betz; Experimental searches for axion like particles, Geneva 2011
http://physicsworld.com/cws/article/news/30423
Nonetheless the publication
in 2006 triggered world wide interest and inspired many new experimental activities
Slide11Axion helioscopesMagnetic field converts photons to axions
inside the sun11The CERN Axion Solar Telescope (CAST)
M. Betz; Experimental searches for axion like particles, Geneva 2011
Magnetic field converts axions
to X-ray photons
axions
photons
Prototype LHC magnet, 10 m long, 9 Tesla on a movable platform
Tracks the sun for 3h / day, 50 days / year
X-ray
focusing system (prototype from the space based X-ray telescope ABRIXAS)
X-ray detectors (
micromegas
, CCD) at both ends of the magnet
Has been running since 2003 and is now waiting for an upgrade in 2012
Slide12Axion helioscopesAssumes: Axions are dark matter, a relic from the big bang and already all around us8 T Magnet converts relic axions to microwave photons
Tunable cavity 460 – 810 MHz to “collect” those photonsSQUID amplifier, system noise temperature TN = 2.5 K, one of the quietest microwave receivers in the worldRunning since 2006 (at LLNL), moved to University of Washington in 2010, upgrade of cryo system this year
12The Dark Matter
eXperiment (ADMX) in WashingtonM. Betz; Experimental searches for axion like particles, Geneva 2011
Slide13Laser LSW experiments13LSW = Light shining through the wall
M. Betz; Experimental searches for axion like particles, Geneva 2011
1020 photons/s
< 1 photon/sSome photons convert to axions (emitting side)axions can pass the wallSome axions convert back to photons (detection side)It seems like light is shining through the wall!
Fabry-Perot cavities allow to enhance the probability: photons make many passesphotons
axionsphotons
(Optical resonator cavities)
Slide14Laser LSW14A lot of activity around the world
M. Betz; Experimental searches for axion like particles, Geneva 2011
ALPS
at DESY (Germany)OSQUAR at CERN (next door)
XAX
at ESRF (France)
GRIM REPR at Fermilab
(USA)
Slide15Experimental searches around the world15Results so far: No
axion has been observed yetM. Betz; Experimental searches for axion like particles, Geneva 2011
Towards a new generation axion
helioscope, Igor G Irastorza7th Patras Workshop on Axions, WIMPs and WISPs
Laser LSW
(ADMX)
Laser polarization
Sensitivity
Mass
Slide16Microwaves shining through the wallWhy microwaves resonators?High
Q-factors around 105 (low loss) are easily achievedEasier construction / alignmentHomodyne
detection methods can be applied (very sensitive)Instruments and know-how exists
But:The “wall” becomes a faraday cage EMI shielding challenge16Cavities become coupled through axions
M. Betz; Experimental searches for axion like particles, Geneva 2011
γ Photona AxionEM. Electromagnetic
Slide17The photon conversion cavities17Prototypes after machining (left) and coating (right)
M. Betz; Experimental searches for axion like particles, Geneva 2011
Material: Brass (non magnetic)
Fine thread tuning screw Coupler (
β=1)
Slide18TE
011 mode, H–field on YZ-planeThe photon conversion cavities
18
Numerical simulation of the TE011 modeM. Betz; Experimental searches for axion like particles, Geneva 2011
Possible location of an inductive coupling loop for the TE011 mode(The loop extends on the XY-plane)
TE
011 mode, E–field on XY-plane
TE011
mode, E–field in X-direction
Tuning screw:(20 mm diameter, fine thread)
Slide19Electromagnetic shielding
Experiment is split into a cryogenic and room temperature part19
Splitting the experiment into two parts
M. Betz; Experimental searches for axion like particles, Geneva 2011Electric / optical converter
Optical / electric converterShielding Box 1Contains the Axion
detection cavity and will later be placed in the cryostat / magnetShieldingBox 1(Cryo.)
Optical FibreCarries the weak signal from Axion conversion to the measurement instruments, unaffected by ambient EM. noise and without comprising the shielding boxes
Shielding Box 2Contains instruments for the detection of weak narrowband microwave signals and will be outside the cryostat / magnetShielding Box 2(Room temp.)
EnvironmentalRF noise
Slide20Electromagnetic shieldingEM absorbing material between shielding layers (non magnetic!)Chain of lowpass
feedtrough filters for supply voltageIf we still see leakage:Power over optical fibreCommercial systems available (JDSU Photonic power module)Efficiency 50 %
(optical electric)We can always add another layer of shielding
20Some practical aspectsM. Betz; Experimental searches for axion like particles, Geneva 2011
High power
Laser diode
VCC
Optical power
converter
Slide21DC – feedtrough filters21
For feeding DC power through the shielding while keeping RF outM. Betz; Experimental searches for axion like particles, Geneva 2011
Measurement with a network analyser in transmission
- 95 dB at 3 GHz
Syfer
SFJNC2000684MX1
Slide22Electromagnetic shielding22Shielding box 1 prototype, containing the receiving cavity
M. Betz; Experimental searches for axion like particles, Geneva 2011
Slide23Debugging of the faraday cagePhase locked RF – Source (3 GHz)Optical receiver for 10 MHz phase lock signal
50 W RF power amplifierCustom made EMI - feed trough filter for AC powerFaraday cage, containing detection partFibre optical converter for control signalsMultimeter for tuning the cavityEmitting cavity
23
The current status in the laboratoryM. Betz; Experimental searches for axion like particles, Geneva 2011
E.M. leakage
test setup
Slide24Electromagnetic shielding24Shielding box 2 prototype, containing the instrumentation
M. Betz; Experimental searches for axion like particles, Geneva 2011
Feedtrough
for optical fibresReceiving cavitySpectrum analyzerLow noise amplifier
E.M. leakage
test setup
Slide25Online diagnosticsTest tones (TX
n)Low power (μW) probe signals Injected in laboratory space and between shielding layersEach one has a slightly
different frequency within the cavity bandwidthMonitoring signal power (RXn
) allows to quantify the attenuation of each shielding layer25Supervising the shielding attenuation with test tonesM. Betz; Experimental searches for axion like particles, Geneva 2011
We need
ONLINE
diagnostics showing, that the shielding performance is really maintained over the full lifetime of the experiment. Degradation is possible due to bad and ageing contacts
If dynamic
range of the receivers is not sufficient, time multiplexing
is an option.
(Sender and receiver in the same shielding shell are not enabled at the same time)
Slide26Online diagnosticsAll possible signal paths are represented as arrowsGreen signals pass one shielding layer and can be used to quantify its attenuation
Red signals pass more than one shielding layer. Observation of a red signal = veto condition on Axion detection26
Possible signal-paths
M. Betz; Experimental searches for axion like particles, Geneva 2011
Attenuation of the Shieldingbox
is measured twice, giving us redundancy
Shieldingbox
Slide27Detecting weak narrowband signals27
Homodyne detection with an commercial vector signal analyserM. Betz; Experimental searches for axion like particles, Geneva 2011
Common reference clock
Vector signal analyser (Agilent N9010A EXA)
To detect signals down to -230
dBm
we need resolution bandwidths in the 10
μ
Hz rangeThis can be
achieved with a FFT on a 24 h time traceFrequency
drifts are unavoidable!
But
by
phase
locking
source
and
analyzer
we
can
eliminate
relative
frequency
errors
Slide28Photon regeneration exp. at CERN28Technical specifications and challenges for hidden photon search
M. Betz; Experimental searches for axion like particles, Geneva 2011
Expected signal power from the receiving cavity
arXiv:0707.2063v1
F. Caspers, J. Jaeckel, A. Ringwald, A Cavity Experiment to Search for Hidden Sector Photons
What we want to achieve (for HSPs):
P
em
50 W = 47 dBm
Signal power into emitting cavity
P
det
10
-26
W =
-230
dBm
Signal power from receiving cavity
Q
23 000
Quality factor emitting cavity
Q‘
23 000
Quality factor receiving cavity
G
≈ 0.5
HSP.
geometry
factor
m
γ
’
12
μ
eV
≈ 3 GHz
Hidden photon mass
ω
0
3 GHz
Cavity resonance frequency
Χ
1.1 ·
10
-9
Coupling factor (exclusion limit)
300 dB
Slide29AcknowledgementsThe author would like to thank the CERN BE and BI-dept. management for support as well as R. Jones and R. Heuer for encouragement
Many thanks to A. Ringwald, A. Lindner and J. Jäckel for a large number of hints as well as and K. Zioutas for having brought the right people in the right moment together as well as haven given very helpful comments
29
M. Betz; Experimental searches for axion like particles, Geneva 2011