Search for solar axions with the CAST experiment Biljana Lakić (Rudjer Bošković Institute, Zagreb) for the CAST Collaboration Time and Matter 2010, 04-08

Search for solar axions with theSearch for solar axions with theCASTCAST experiment experiment

Search for solar axions with theSearch for solar axions with theCASTCAST experiment experiment

Biljana LakiBiljana Lakićć(Rudjer Bo(Rudjer Bošškovikovićć Institute, Institute, Zagreb Zagreb))

for the for the

CAST CollaborationCAST Collaboration

Time andTime and Matter 20 Matter 201010, , 0404--0808 OctoberOctober 20 201010, , BudvaBudva,, Montenegro Montenegro

TAMTAM20201010, , 0404--0808 OctOct 20 201010, , BudvaBudvaBiljana LakiBiljana Lakićć 22

CASTCAST:: CERN Axion Solar Telescope CERN Axion Solar Telescope

CAST Collaboration

CEA Saclay -- CERN -- Dogus University -- Lawrence Livermore National Laboratory -- Max-Planck-Institut for Solar System Research/Katlenberg-Lindau -- Max-Planck-Institut für extraterrestrische Physik -- Max-Planck-Institut für Physik -- National Center for Scientific Research Demokritos -- NTUA Athens -- Institut Ruđer Bošković Zagreb -- Institute for Nuclear Research (Moscow) -- TU Darmstadt -- University of British Columbia -- University of Chicago -- Universität Frankfurt -- Universität Freiburg -- University of Patras -- University of Thessaloniki -- Universita di Trieste --Universidad de Zaragoza

21 institutions, 84 scientists21 institutions, 84 scientists


CASTCAST:: CERN Axion Solar Telescope CERN Axion Solar Telescope

CASTCAST


Outline:Outline:

AxionsAxions

TheoryTheory

Experimental searchesExperimental searches

The CAST experimentThe CAST experiment

PhysicsPhysics

SetupSetup

Results and prospectsResults and prospects

AxionAxion is is named after a brand of named after a brand of washing washing powderpowder (it cleaned up a long-standing (it cleaned up a long-standing problem in theoretical physics)problem in theoretical physics)

TAMTAM20201010, , 0404--0808 OctOct 20 201010, , BudvaBudva

AxionsAxions were introduced to solve the were introduced to solve the Strong CP ProblemStrong CP Problem::

It is well known that the weak nuclear force violates the CP It is well known that the weak nuclear force violates the CP symmetry (more matter than antimatter in the Universe) symmetry (more matter than antimatter in the Universe)

Strong CP problem: strong nuclear force theory violates the CP Strong CP problem: strong nuclear force theory violates the CP symmetry symmetry

It should be observable in the measurements of the electric dipole It should be observable in the measurements of the electric dipole moment of the neutron (nEDM)moment of the neutron (nEDM)

Strong experimental bound on nEDM requires Strong experimental bound on nEDM requires 10 10-9 -9

55Biljana LakiBiljana Lakićć

AxionsAxions

a

μνa GG

~

8s

CP strong MdetArg

(QCD vacuum + EW quark mixing)(QCD vacuum + EW quark mixing)


Peccei-Quinn solution:Peccei-Quinn solution:

In 1977, Peccei and Quinn proposed an elegant solution: a In 1977, Peccei and Quinn proposed an elegant solution: a new global new global chiral U(1)chiral U(1)PQPQ symmetry spontaneously broken at scale symmetry spontaneously broken at scale ffaa

Associated pseudo-Goldstone boson is Associated pseudo-Goldstone boson is axionaxion

ParameterParameter is re-interpreted as dynamical variable (scalar field) and is is re-interpreted as dynamical variable (scalar field) and is

absorbed in the definition of the axion field: absorbed in the definition of the axion field:

No more CP violation in the theory! The only thing left is to find axions…No more CP violation in the theory! The only thing left is to find axions…


AxionsAxions

a

μνa

aaa

μνa GGa

fGG

~

8

~

8ss

strongCP

afxa


AxionsAxions

08.092.1213

42

2 N

E

fwz

wz

N

E

fg

aaa

Axion mass and couplingsAxion mass and couplings

axions generically couple to gluons axions generically couple to gluons

and mix with pionsand mix with pions

massmass::aa

a ff

fmm

GeV10eV6

6

couplings to photons, nucleons and electrons (optional)couplings to photons, nucleons and electrons (optional)

axion-photon coupling axion-photon coupling has two contributions:has two contributions:

axion-photon coupling via triangle loopaxion-photon coupling via triangle loop

axion-pion mixingaxion-pion mixing


AxionsAxions

Axion models:Axion models: standard axion model (standard axion model (ffa a ffweakweak) excluded experimentally) excluded experimentally

invisible axion models (invisible axion models (ffaa >>>>ffweakweak, , gg ~ ~1/1/ffaa, , mmaa ~1/~1/ffaa))

KSVZ KSVZ (Kim, Shifman, Vainshtein, Zakharov)(Kim, Shifman, Vainshtein, Zakharov)

DFSZ (Dine, Fischler, Srednicki, Zhitnitskii) DFSZ (Dine, Fischler, Srednicki, Zhitnitskii)

AxionAxion properties properties::

very low mass and coupling constant (very low mass and coupling constant (ffaa >>>>ffweakweak, , gg ~ ~1/1/ffaa, , mmaa ~1/~1/ffaa)) practically stable practically stable neutral pseudoscalar neutral pseudoscalar candidate for dark mattercandidate for dark matter


AxionsAxions are candidates for the are candidates for the Dark Matter of the UniverseDark Matter of the Universe (axions produced in the (axions produced in the early Universe)early Universe)


AxionsAxions

Cold Dark Matter (CDM)Cold Dark Matter (CDM):: responsible for small-scale responsible for small-scale

structuresstructures (WIMPs, axions …) (WIMPs, axions …) axion as CDM: coherent axion as CDM: coherent

oscillations of the axion fieldoscillations of the axion fieldHot Dark Matter (HDM)Hot Dark Matter (HDM):: neutrinos, axions …neutrinos, axions … axions as HDM: thermal relics axions as HDM: thermal relics

(in analogy to neutrinos)(in analogy to neutrinos)

CDMCDM

HDMHDM

Cosmological limit: Cosmological limit: 1010-5 -5 eVeV mma a 1 eV1 eV


AxionsAxions from astrophysical sourcesfrom astrophysical sources

Low mass, weakly interacting particles Low mass, weakly interacting particles (neutrinos, gravitons, axions etc.) are (neutrinos, gravitons, axions etc.) are produced in hot stellar plasma and can produced in hot stellar plasma and can transport energy out of stars.transport energy out of stars.

The couplings of these particles with The couplings of these particles with ordinary matter and radiation are ordinary matter and radiation are bounded by the constraint that stellar bounded by the constraint that stellar lifetimes do not conflict with the lifetimes do not conflict with the observations.observations.

For axion-photon coupling, the most For axion-photon coupling, the most restrictive astrophysical limit derives restrictive astrophysical limit derives from globular cluster (GC) stars, by from globular cluster (GC) stars, by comparing the number of horizontal comparing the number of horizontal branch (HB) stars with the number of branch (HB) stars with the number of red giants. red giants.


AxionsAxions


AxionsAxions

AAstrophysical and cosmological limitsstrophysical and cosmological limits::

Globular clusters Globular clusters (a - (a - coupling) coupling)

LaboratoryLaboratory Tel.Tel.

Axion dark matter possible Axion dark matter possible (Late inflation scenario)(Late inflation scenario)

DM ok Too much DM DM ok Too much DM (String scenario) (String scenario)

Hot dark matter limitsHot dark matter limits (a - (a - coupling) coupling)


AxionsAxions

Experimental searches Experimental searches (a-(a- coupling) coupling)::Laser experiments:Laser experiments:

Photon regeneration (“invisible light Photon regeneration (“invisible light shining through wall”)shining through wall”)

Polarization experiments (PVLAS)Polarization experiments (PVLAS)

Search for dark matter axions:Search for dark matter axions:

Microwave cavity experiments Microwave cavity experiments (ADMX)(ADMX)

Search for solar axions:Search for solar axions:

Bragg + crystal Bragg + crystal (SOLAX, COSME, (SOLAX, COSME, DAMA)DAMA)

Helioscope (Helioscope (SUMIKOSUMIKO, , CASTCAST))



CASTCAST:: Physics PhysicsPrinciple of the Axion helioscope Principle of the Axion helioscope Sikivie, Phys. Rev. Lett 51 (1983)Sikivie, Phys. Rev. Lett 51 (1983)

a thermal photon converts into an a thermal photon converts into an axion in the Coulomb fieldsaxion in the Coulomb fields of of nuclei and electrons in the solar nuclei and electrons in the solar plasma (plasma (Primakoff processPrimakoff process))

Sun:Sun: an axion converts into a an axion converts into a photon in a strong photon in a strong transverse magnetic fieldtransverse magnetic field

Earth:Earth:

aγaa

aγ dEtAP

dE

dΦN

-expected number of photons-expected number of photons

A = detector effective areaA = detector effective area

t = measurement timet = measurement time



CAST: PhysicsCAST: Physics

- differential axion flux at the Earth:- differential axion flux at the Earth:

112keV2051

48122

11010 keVscm

keV

GeV1010026

./E

.aaγ

a

a

ae

/Eg.

dE

dΦ


2

GeV10

g110

aγ

EEaa = 4.2 keV = 4.2 keV



qLee/Γq

BgP L/ΓLΓaγ

γa cos214

1

22

22

2

a

aγ

E

mmq

2

22

L

πEmm

L

πEmπqL a

γaa

γ

22 22

conversion probabilityconversion probability in gas in gas (in vacuum: (in vacuum: = 0, = 0, mm=0):=0):

LL=magnet length, =magnet length, =absorption coeff.=absorption coeff.

(K)

(mbar)020(eV)

T

P .mγ

axion-photon momentum transfer axion-photon momentum transfer

effective photon mass (T=1.8 K)effective photon mass (T=1.8 K)

coherencecoherence condition condition for for aa → → conversion conversion

ga=10-10 GeV-1

In case of vacuum, coherence is lost for In case of vacuum, coherence is lost for mma a > 0.02 > 0.02

eV. It can be restored with the presence of a buffer eV. It can be restored with the presence of a buffer gas, but only for a narrow mass range.gas, but only for a narrow mass range.



Novel techniqueNovel technique (developed by CAST) for (developed by CAST) for observing axion solar signature: Off-resonance observing axion solar signature: Off-resonance spectraspectra

S = Shift S = Shift from the from the

resonanceresonance

S = 0S = 0

S = S = 33FWHMFWHM

S = FWHMS = FWHM

S = FWHM/2S = FWHM/2



CAST operation:CAST operation:

Phase IPhase I

VVacuum in the magnet bores: acuum in the magnet bores: mmaa < 2.3 < 2.31010-2 -2 eV eV (during 2003 (during 2003

and 2004) and 2004)

Phase IIPhase II

44He gas pressure increased from He gas pressure increased from 0 - 0 - 1414 mbar: mbar: mmaa < 0. < 0.3939 eV eV

(during 2005 and 2006)(during 2005 and 2006)

33He gas pressure increased from He gas pressure increased from 1414 - - 120120 mbar: mbar: mmaa < < 11..16 eV16 eV

((2008 – 20102008 – 2010))

CAST CAST exclusion plotexclusion plot


CAST: PhysicsCAST: PhysicsWorldWorld exclusion plotexclusion plot

CAST and ADMX enter the CAST and ADMX enter the theoretically favoured QCD axion theoretically favoured QCD axion region (“Axion models”)region (“Axion models”)

The rest of the parameter space The rest of the parameter space belongs to axion-like particles belongs to axion-like particles (ALPs): particles with two-photon (ALPs): particles with two-photon couplingcoupling

PVLAS result in 2006: PVLAS result in 2006: a “signal” with possible particle a “signal” with possible particle

interpretation in the region excluded interpretation in the region excluded by stellar loss arguments and CAST by stellar loss arguments and CAST limit limit numerous theoretical numerous theoretical papers and experimental projects!papers and experimental projects!

after upgrades, the signal was lostafter upgrades, the signal was lost


AAstrophysical and cosmological limitsstrophysical and cosmological limits::

Globular clusters Globular clusters (a - (a - coupling) coupling)

LaboratoryLaboratory Tel.Tel.

Axion dark matter possible Axion dark matter possible (Late inflation scenario)(Late inflation scenario)

DM ok Too much DM DM ok Too much DM (String scenario) (String scenario)

Hot dark matter limitsHot dark matter limits (a - (a - coupling) coupling)

CASTCAST ADMXADMX



CASTCAST:: Setup Setup LHC test magnet (B=9 T, L=9.26 m)

Rotating platform (hor. ±40, ver. ±8)

X-ray detectors

X-ray Focusing Device

LHC test magnet (B=9 T, L=9.26 m)

Rotating platform (hor. ±40, ver. ±8)

X-ray detectors

X-ray Focusing Device

Sunset Sunset DetectorsDetectors Sunrise Sunrise

DetectorsDetectors

LHC test magnetLHC test magnet

Exposure time: Exposure time: 22××1.5h per day 1.5h per day


CASTCAST:: Setup Setup

… … one solar tracking (1.5 h) …one solar tracking (1.5 h) …


CASTCAST:: Tracking precision Tracking precision

GRID measurementsGRID measurements

Horizontal and vertical encoders determine the magnet orientationHorizontal and vertical encoders determine the magnet orientation

Correlation between encoder value-magnet orientation has been established for a Correlation between encoder value-magnet orientation has been established for a number of points (GRID)number of points (GRID)

Periodical measurements show that CAST points to the Sun within the required Periodical measurements show that CAST points to the Sun within the required precisionprecision

Comparison of March 2010 and Comparison of March 2010 and September 2002 GRID. The September 2002 GRID. The required precision of 1 arcmin is required precision of 1 arcmin is indicated by the green circle, indicated by the green circle, while the red one represents the while the red one represents the 10% of the Sun projected at 10 m. 10% of the Sun projected at 10 m.



Solar filmingSolar filming

Twice per year (March and September) we can film the Sun through the windowTwice per year (March and September) we can film the Sun through the window

A camera is placed on top of the magnet and is aligned with the bore axisA camera is placed on top of the magnet and is aligned with the bore axis

Corrections for visible light refractions are taken into accountCorrections for visible light refractions are taken into account

Since March 2008, 2 independent systems are in use Since March 2008, 2 independent systems are in use


… … Sun, airplane, sunspot …Sun, airplane, sunspot …



CASTCAST:: Detectors before 2007 Detectors before 2007

pn-CCD chippn-CCD chip

X-ray telescope + CCD (X-ray telescope + CCD (sunrise sidesunrise side))

from 43 mm (LHC magnet ∅aperture) to ~3 mm ∅

signal-to-noise improvement (up to 200!)

0.18 counts/h (1-7 keV)0.18 counts/h (1-7 keV)

44He phaseHe phase

20020064 pixels (164 pixels (13 cm3 cm22))

Pixel size: 150Pixel size: 150150 150 mm22


CASTCAST:: Detectors before 2007 Detectors before 2007

unshielded Micromegas (unshielded Micromegas (sunrise sidesunrise side))

shielded TPC (shielded TPC (sunset sidesunset side))

25 counts/h (2-10 keV)25 counts/h (2-10 keV)

85 counts/h (2-12 keV)85 counts/h (2-12 keV)

Covering both magnet boresCovering both magnet bores

Geometry: 30cmGeometry: 30cm 15cm 15cm 10cm10cm

Gas: Ar 95%, CHGas: Ar 95%, CH44 5% 5%

44He phaseHe phase


CASTCAST:: Detectors after 2007 Detectors after 2007 33He phaseHe phase

Micromesh5µm copper

Kapton 50 µm

Readout pads

Sunrise sideSunrise side: CCD+Telescope & shielded : CCD+Telescope & shielded Microbulk Microbulk MM MM

Sunset sideSunset side: 2 shielded : 2 shielded Microbulk Microbulk MM MM

MicrobulkMicrobulk: : new technique, high radio-purity materials, very low backgroundnew technique, high radio-purity materials, very low background

MM 2 counts/h (2-10 keV)

CCD 0.18 count/h (1-7 keV)

sunrisesunrise

sunsetsunset

In 2010, a In 2010, a “5“5thth line” line” was added: was added: a 3.5 a 3.5 μμm aluminized Mylar foil m aluminized Mylar foil (transparent to X-rays) is placed (transparent to X-rays) is placed on the sunrise Micromegas line on the sunrise Micromegas line to deflect to deflect visible photonsvisible photons on an on an angle of 90angle of 90oo, towards the , towards the PMTPMT

Low energy axionsLow energy axions


CASTCAST:: Gas system for the Gas system for the 33He phase He phase

33He gas systemHe gas system Accuracy in measuring the quantity of gas Accuracy in measuring the quantity of gas

introduced in the cold boreintroduced in the cold bore (100ppm) (100ppm) Flexible operation modes (stepping and Flexible operation modes (stepping and

ramping)ramping) Hermetic system to avoid loss of Hermetic system to avoid loss of 33HeHe Absence of thermo-acoustic oscillationsAbsence of thermo-acoustic oscillations Protection of cold thin X-ray windows Protection of cold thin X-ray windows

during a quenchduring a quench

33He phaseHe phase

X-ray windowsX-ray windows High X-ray transmission (polypropylene 15 High X-ray transmission (polypropylene 15 m)m) Robust (strongback mesh)Robust (strongback mesh) Minimum He leakageMinimum He leakage Mechanical endurance toMechanical endurance to sudden rise of pressuresudden rise of pressure


Magnet quench: Magnet quench: superconducting magnet resistive transitionsuperconducting magnet resistive transition

CASTCAST:: Magnet quenchMagnet quench


CASTCAST:: Simulations for theSimulations for the 33He phase He phase

Simulations & new instrumentation Simulations & new instrumentation have been essential in understanding have been essential in understanding 33He systemHe system

in CAST temperature and density in CAST temperature and density conditions, conditions, 33He He is not an ideal gasis not an ideal gas (Van (Van der Waals forces)der Waals forces)

convergence between simulation convergence between simulation results & experimental data results & experimental data

Knowledge of gas density / setting Knowledge of gas density / setting reproducibility possiblereproducibility possible

Gas density stable along magnet boreGas density stable along magnet bore

Coherence length slowly Coherence length slowly decreases with increasing densitydecreases with increasing density


COUNTS SEEN IN ALL STEPS

OF SAME DENSITY

counts/

step

CCD MM MMs MMs

Repetition m_i Det 1 Det 2 Det 3 Det 4 OUTCOME

0 1 4 0 0 CANDIDATE

1 0 0 0 0 NO CANDIDATE



CASTCAST:: Phase II data taking Phase II data taking

Phase II data taking is demanding and excitingPhase II data taking is demanding and exciting

Every day a new pressure setting Every day a new pressure setting every day a new experiment ! every day a new experiment !

Daily quick-look analysis shows if we have a “candidate”Daily quick-look analysis shows if we have a “candidate”



Sunrise MicromegasSunrise Micromegas

Tracking (red) and Tracking (red) and background (blue) background (blue) spectra in 2010spectra in 2010

2010 counts in 2010 counts in different pressure different pressure settings: tracking (red), settings: tracking (red), background (blue)background (blue)


Sunset MicromegasSunset Micromegas


2010 counts in different 2010 counts in different pressure settings: pressure settings: background (red), background (red), tracking (blue)tracking (blue)


one single tracking one single tracking backgroundbackgroundintegrated trackings integrated trackings

CCDCCDCASTCAST:: Phase II analysis Phase II analysis


CASTCAST:: First First 33He phase results He phase results

no signal over background observed yetno signal over background observed yet


CAST: CAST: Additional Additional PhysicsPhysics

Search for Search for monoenergetic 14.4 keV axionsmonoenergetic 14.4 keV axions

strong emission of 14.4 keV axions is expected from de-excitation of strong emission of 14.4 keV axions is expected from de-excitation of thermally excited thermally excited 5757Fe nuclei in the SunFe nuclei in the Sun

TPC data from phase I were used TPC data from phase I were used


Calorimeter :Calorimeter : Results :Results :

1)1) 77Li* Li* →→ 77Li + a (478 keV) Li + a (478 keV)

77Be + eBe + e-- →→ 77Li* + Li* + ννee

2)2) p + d p + d →→ 33He + a (5.5 MeV) He + a (5.5 MeV)


Search for Search for monoenergetic monoenergetic high-energyhigh-energy axion axions s


Kaluza – Klein axionsKaluza – Klein axions

Due to the coherence condition, CAST could be sensitive to the existence of Due to the coherence condition, CAST could be sensitive to the existence of large extra dimensions large extra dimensions particular Kaluza-Klein states particular Kaluza-Klein states

Low energy solar axions Low energy solar axions

Sun could be a Sun could be a strong strong source of low energy axions (in the visible – UV) source of low energy axions (in the visible – UV) created below sunspots. created below sunspots.

CAST CAST isis complementary (and competitive complementary (and competitive)) with laboratory–based with laboratory–based experimentsexperiments



CAST published physics resultsCAST published physics results

For For mmaa<0.02 eV: <0.02 eV: ggaaγγ0.88 0.88 1010-10-10 GeV GeV-1-1

JCAP04(2007)010JCAP04(2007)010

PRL (2005) 94, 121301PRL (2005) 94, 121301

For For mmaa<0.39 eV typical upper limit: <0.39 eV typical upper limit: ggaaγγ2.2 2.2 1010-10-10 GeV GeV-1-1

JCAP 0902:008,2009JCAP 0902:008,2009

CAST byproducts:CAST byproducts:High Energy Axions: Data taking with a HE calorimeterHigh Energy Axions: Data taking with a HE calorimeter

JCAP 1003:032,2010JCAP 1003:032,2010 14.4 keV Axions: TPC data 14.4 keV Axions: TPC data

JCAP 0912:002,2009JCAP 0912:002,2009Low Energy (visible) Axions: Data taking with a PMT Low Energy (visible) Axions: Data taking with a PMT

arXiv:0809.4581arXiv:0809.4581


CAST outreachCAST outreach

Organization of Axion workshops Organization of Axion workshops

11stst Joint ILIAS-CAST-CERN Axion Training Workshop 2005, CERN Joint ILIAS-CAST-CERN Axion Training Workshop 2005, CERN

22ndnd Joint ILIAS-CAST-CERN Axion Training Workshop 2006, Patras Joint ILIAS-CAST-CERN Axion Training Workshop 2006, Patras

33rdrd Joint ILIAS-CERN-DESY Axion-WIMPs training-workshop 2007, Patras Joint ILIAS-CERN-DESY Axion-WIMPs training-workshop 2007, Patras

44thth Patras Workshop on Axions, WIMPs and WISPs 2008, DESY Patras Workshop on Axions, WIMPs and WISPs 2008, DESY

55thth Patras Workshop on Axions, WIMPs and WISPs 2009, Durham Patras Workshop on Axions, WIMPs and WISPs 2009, Durham

66thth Patras Workshop on Axions, WIMPs and WISPs 2010, Zurich Patras Workshop on Axions, WIMPs and WISPs 2010, Zurich

1313thth April 2010: CAST 10 April 2010: CAST 10th th anniversaryanniversary


CAST will finish the planned program by July 2011CAST will finish the planned program by July 2011

Proposal in preparation for the period 2011 – 2013Proposal in preparation for the period 2011 – 2013

Improve vacuum limit Improve vacuum limit

low noise Micromegas detectorslow noise Micromegas detectors

low tresholdlow treshold

Search for chameleons, paraphotons, low energy axions ...Search for chameleons, paraphotons, low energy axions ...

R&D towards R&D towards New Generation Axion Helioscope New Generation Axion Helioscope (detectors, optics, magnet)(detectors, optics, magnet)

coupling constant dependence:coupling constant dependence:

CAST prospectsCAST prospects

systemtracking

8/1

detector

8/1

magnet

4/12/1 tbABLga



AAxion helioscopesxion helioscopes prospects prospects

Ongoing R&D on magnets at CERN Ongoing R&D on magnets at CERN

Possible Possible after 2013after 2013: :

B=13 T, L=4 m, B=13 T, L=4 m, =10 cm=10 cm

Development of x-ray optics (high efficiency)Development of x-ray optics (high efficiency)

Midterm scenarioMidterm scenario

Ongoing R&D on magnets at CERN Ongoing R&D on magnets at CERN

Possible Possible after 2016 + after 2016 + “some funds”: “some funds”:

B=14 T, L=8 m, B=14 T, L=8 m, =14 cm=14 cm

Development of x-ray optics (high efficiency)Development of x-ray optics (high efficiency)

Longer term scenarioLonger term scenario

And more …And more …


ConclusionsConclusions CAST provides the best experimental CAST provides the best experimental

limit on axion-photon coupling limit on axion-photon coupling constant over a broad range of axion constant over a broad range of axion masses.masses.

CAST Collaboration has gained a lot CAST Collaboration has gained a lot of experience in axion helioscope of experience in axion helioscope searches. searches. R&D on superconducting magnets R&D on superconducting magnets can lead to much more sensitive can lead to much more sensitive helioscopes.helioscopes.

Future helioscope experiments and Future helioscope experiments and Microwave cavity searches (ADMX) Microwave cavity searches (ADMX) could cover a big part of QCD axion could cover a big part of QCD axion model region until 2020. model region until 2020.

Documents

Search for solar axions with the CAST experiment Biljana Lakić (Rudjer Bošković Institute, Zagreb) for the CAST Collaboration Time and Matter 2010, 04-08