CAST: "Blind" telescope looks at the Sun. Marin Karuza, University of Rijeka Imperial College, London,

Transcription

1 CAST: "Blind" telescope looks at the Sun

2 CAST: "Blind" telescope looks at the Sun Introduction Looking for axions and not only Outlook

3 Introduction CAST Cern Axion Solar Telescope Why blind? Not sensitive to the EM waves. NASA, ESA and the Hubble Heritage Team (STScI/AURA) CAST, Cern Axion Solar Telescope

4 Why use blind telescope? 95% Universe is dark. Ann Feild (STScI)

5 Where to look for the dark matter? In the brightest object in the sky! Sun as seen from Geneva, Switzerland. Solar evolution constrains the total exotica flux to less than 10%

6 How does Sun produce exotic particles? From two photons! Primakoff effect directly Primakoff effect Examples: Axion Chameleon...

7 How are exotic particles detected? WISP Weakly Interacting Slim Particles --> weak or non existent interaction with matter - best chance by converting them back to photons - a photon has to be provided (electric or magnetic field) Inverse Primakoff effect

8 Reconversion: Virtual photon - a photon has to be provided - choice: magnetic field - --> spare LHC magnet - 45 mm bore diameter - ~10 m long - B ~ 9 T

9 How are exotic particles detected? - integration time, moving platform that follows the Sun - 8 deg to 8 deg 2x 1500 sec per day (at sunset and sunrise)

10 The Cern Axion Solar Telescope γ axion, chameleon, Sunset detectors 2 MicroMegas Detectors X B γ

11 The Cern Axion Solar Telescope axion, chameleon, γ γ Sunrise detectors B Up to 2013: MicroMegas, CCD & MPE XRT Since 2014: MicroMegas & LLNL XRT, InGrid & MPE XRT X

12 Sun filming and moon filming periodically used to check the correct orientation of the magnet to the sun

13 Sun filming and moon filming periodically used to check the correct orientation of the magnet to the sun Expensive and heavy movable platform with low duty cycle if interested only in the visible range

14 Sun and moon filming pictures

15 Does CAST follow the Sun? Sun 9 mrad

16 Physics CAST is searching for solar axions using the inverse Primakoff effect Photons in the sun are converted to axions via the Primakoff effect Back-conversion of axions into x-ray photons in a strong magnetic field via the inverse Primakoff effect P. Sikivie, PRL 51, (1983)

17 Physics: Expected signal Solar axion luminosity Axion flux on earth Expected number of photons (1-10 kev) and A = 14.5 cm 2

18 Detectors: Micromegas Micro-Mesh Gaseous Structure Characterized at Zaragoza: good gain uniformity in the active area & excellent energy resolution (13% FWHM at 5.9 kev).

19 Detectors: Micromegas Performance Sunrise Micromegas Sunset Micromegas Taking data since 4 th September Gain & energy resolution stable Preliminary analysis of the first 240 hours in a wide active area gives a background level compatible with Sunset values: (0.8 ± 0.2) x 10-6 kev -1 cm -2 s -1 Newly-designed scintillator veto system installed in September 2013 Better than 90% efficiency New veto system reduced background by 50% Accumulated background data during 2013 and 2014 data takings resulted in an unprecedented level of (1.00 ± 0.05) x 10-6 kev -1 cm -2 s -1 in the [2-7] kev range (75% signal efficiency)

20 Detectors: Micromegas Axion Results Search for Solar Axions by the CERN Axion Solar Telescope with He 3 Buffer Gas: Closing the Hot Dark Matter Gap, M Arik, et. al. Phys. Rev. Lett. 112 (9),

21 CAST Axion Outlook 2015 run

22 Physics: Chameleons New searches in vacuum : Chameleons Chameleons are Dark Energy candidates to explain the acceleration of the expansion of the Universe. Their mass depends on the energy density of the environment Solar Chameleons Can be created by the Primakoff effect in the tachocline region of the Sun (R~0.7R ʘ ). Philippe Brax Spectrum of back-converted photons in the CAST magnet inside 16 mm2 for B tacho = 10T, n=1 They can be converted to X-ray photons in CAST via the inverse Primakoff effect (like axions) Detector requirements: Low energy threshold Low background Good energy resolution

23 Detectors: Status Silicon Drift Detector

24 Detectors: SDD Preliminary results

25 Detectors: SDD Preliminary results Publication under preparation Results of bsdd compatible with the null hypothesis Limit to β γ at 95% C.L. Valid for 1 β m 10 6 P R E L I M I N A R Y

26 Radiation pressure Theoretical calculations Experimental status S. Baum, G. Cantatore, D. Hoffmann, M. Karuza, Y.K. Semertzidis, A. Upadhye, K. Zioutas, arxiv:

27 Chameleons: Theory Chameleons are scalar WISPs with effective mass dependent on local matter density. Interesting DE candidates since they evade the constraints coming from "fifth force" experiments. Chameleons couple to Photons Directly to matter Coupling to matter Coupling to photons matter density (local)

28 Chameleons: Theory Production Chameleons produced that leave the Sun. Solar tachocline B = 30T Solar magnetic field In a dense medium chameleons get large effective mass. If their total energy is smaller than their effective mass in a medium they try to penetrate, they will get reflected, resulting in the equivalent of radiation pressure.

29 Chameleons: Theory Travel to Earth Chameleons produced that leave the Sun. Solar tachocline B = 30T Solar magnetic field In a dense medium chameleons get large effective mass. If their total energy is smaller than their effective mass in a medium they try to penetrate, they will get reflected, resulting in the equivalent of radiation pressure.

30 Radiation pressure

31 Radiation pressure n from 1 to 8 gold coated membrane horizontal lines show experimental limits

32 Radiation pressure Experiment sensor chameleon flux Unfortunately chameleon flux too small for such an experiment! More sensitive experiment needed.

33 Radiation pressure Experiment chameleons Use thin stoichiometric silicon nitride membrane as a sensing element Commercially available "large" area, up to 5x5 mm nm High stress High resonant frequency High mechanical Q ~ 10 6

34 Radiation pressure Experiment Information on membrane position Fabry Perot cavity Two mirrors r = 5 cm R = D = 85 mm Finesse ~

35 Radiation pressure Experiment Information on membrane position Fabry Perot cavity Two mirrors r = 5 cm R = D = 85 mm Finesse ~

36 Radiation pressure Experiment Fabry Perot cavity - coupling 50% of light into the cavity - successful lock (PDH technique) - modulation directly on laser crystal - modulation directly on laser crystal

37 Radiation pressure Experiment mirror Information on membrane position Fabry Perot cavity Two mirrors r = 5 cm R = D = 85 mm Finesse ~ membrane

38 - membrane misalignment and shift couples the TEM mn cavity modes via scattering - splitting of degenerate modes and avoided crossings - linear combinations of nearby TEM mn modes become new cavity modes - good agreement with theory Radiation pressure Experiment

39 Radiation pressure Experiment chameleons Position with chameleons Initial position - 30 nm membrane data --> 10 nm corresponds to 25 MHz - 25 Hz --> m

40 Radiation pressure Experiment -control the membrane by light (cooling)

41 Radiation pressure Experiment Resolved sideband cooling - cooling by factor 300, equivalent temperature 1 K reached Effective damping Detected position noise spectrum Karuza et al., New J. Phys. 14, (2012) Mechanical frequency shift

42 - what can we do? Radiation pressure Experiment

43 Radiation pressure Experiment - what have we done? - all the "easy" steps, mechanics, FP cavity in the lab - to do list - move the chamber to CAST - lock the cavity in the experimental hall - insert the membrane angular precision ~ 10 urad - align to the CAST beam and X-ray telescope

44 Outlook Sunrise detectors Up to 2013: MicroMegas, CCD & MPE XRT Since 2014: MicroMegas & LLNL XRT, InGrid & MPE XRT RadPres & MPE XRT

45 Physics (core bussines) Marin Karuza, University of Rijeka London,