on behalf of CAST Collaboration

Transcription

1 S. Cenk YILDIZ Dogus University/Istanbul on behalf of CAST Collaboration 13th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD13) 7-10 October 2013 Siena, Italy

2 Axions and CAST Experiment X-ray Detectors of CAST CCD Micromegas Evolution of CAST Micromegas New Detectors of CAST SDD Ingrid IAXO Future of Solar Axion Search 2

3 Axions and CAST Experiment X-ray Detectors of CAST CCD Micromegas Evolution of CAST Micromegas New Detectors of CAST SDD Ingrid IAXO Future of Solar Axion Search 3

4 Strong CP Problem -> Peccei-Quinn Mechanism -> AXION Pseudoscalar, neutral boson Light Weakly interacting Solar Axion Spectrum Primakoff Effect: In EM fields: Axion <-> Photon P. Sikivie, Phys. Rev. Lett. 51, (1983) 10 g aγ 10 1 GeV 2 4

5 CAST 5

6 Prototype LHC Dipole Magnet B=8.8T, L=9.26m, T=1.8K Built on a movable platform Tracks the sun 1.5h twice a day. 6

7 Phase I : Vacuum (m a < 0.02eV) Phase II : 4 He (0.02eV< m a < 0.39eV) : 3 He (0.39eV< m a < 1.1eV) 2012: 4 He (0.39eV< m a < 0.42eV) : Vacuum Phys.Rev.Lett. 94 (2005) JCAP 0704 (2007) 010 JCAP 0902 (2009) 008 Phys.Rev.Lett. 107 (2011) PRELIMINARY 7

8 Sensitivity of CAST depends on Magnetic field Magnet length Solar tracking time Detector background Detector Efficiency Detector properties Low Background Methods Passive / Active shielding Offline analysis Using radiopure materials X-ray telescopes 8

9 Axions and CAST Experiment X-ray Detectors of CAST CCD Micromegas Evolution of CAST Micromegas New Detectors of CAST SDD Ingrid IAXO Future of Solar Axion Search 9

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11 CCD pn type fully depleted CCD 2.88cm 2 area, 200x64 pixels Running at 130K G. Lutz, Nucl. Instr. Meth. A518 (2004) 201 X-ray telescope One of 6 sections is used Focal length of 160cm Focuses parallel x-rays in a 9mm 2 spot Background reduction: factor of

12 MICRO MEsh GAseous Structure Transparent mesh 2-D strips readout: 106x106, 33.9cm 2 High electron transparency in the mesh Uniform electric field 2 separate readout Electrons collected in the strips: topological information Ions collected in the mesh: time information Energy resolution: 13% 5.96keV I. Giomataris, Nucl. Instr. Meth. A376 (1996) 29 12

13 3 of 4 CAST detectors are Micromegas Sunset Micromegas 2 detectors sharing gas system/shielding/ DAQ Sunrise Micromegas Single detector, near CCD 13

14 Axions and CAST Experiment X-ray Detectors of CAST CCD Micromegas Evolution of CAST Micromegas New Detectors of CAST SDD Ingrid IAXO Future of Solar Axion Search 14

15 Conventional: Mesh and strips are decoupled and connected by mechanical means Bulk Micromegas Inox mesh Kapton pillars between mesh and strips Robust and stable Microbulk Micromegas Mesh/strips produced together by photolitography Better energy/spatial resolution Lower background level Good radiopurity I. Giomataris, Nucl. Instr. Meth. A560 (2006) 460 JINST 5 (2010)

16 Simulations and laboratory test show: The main source of background is environmental gamma radiation. Cosmic muons contribute to the background 2-5 cm lead 10 cm lead Muon Veto 16

17 New electronics: T2K + AFTER Sunset Micromegas Microbulk detectors Updated muon veto Sunrise Micromegas Redesigned detector + shielding Copper chamber Field cages for uniformity 17

18 Unshielded conventional Micromegas 2-5cm lead shielding bulk and microbulk Micromegas 10cm lead Shielding + Muon Veto (2012) 10cm lead Shielding + Extended Muon Veto + AFTER electronics (2013) Canfranc, underground Laboratory (10 cm lead shielding, 4ππ coverage) 18

19 Axions and CAST Experiment X-ray Detectors of CAST CCD Micromegas Evolution of CAST Micromegas New Detectors of CAST SDD Ingrid IAXO Future of Solar Axion Search 19

20 Solar tracking means sensitivity to other solar exotica like chameleons. Chameleons: Particle candidate of the dark energy It s mass vary depending on the density of the medium. Subject to Primakoff conversion Detectable by CAST Energy range: <1keV 20

21 Test run with commercial detector from Amptek: XR-100SDD 16mm 2 Energy 250eV Low count rate -> To be improved by shielding Si 3 N 4 window coated with Al New detector being prepared: PnDetector: 100mm 2 To be placed in custom designed vacuum vessel No window, higher efficiency for low energy 21

22 TimePix Chip: 256x256 pixel, 1.96cm 2 Micromegas on TimePix by photolitograpy Resistive layer to protect TimePix Can detect single electrons Energy resolution: 5% 5.96keV Will be installed instead of CCD, behind the telescope Combined shielding with Sunrise Micromegas Threshold below 1keV 22

23 Axions and CAST Experiment X-ray Detectors of CAST CCD Micromegas Evolution of CAST Micromegas New Detectors of CAST SDD Ingrid IAXO Future of Solar Axion Search 23

24 International AXion Observatory Years of CAST experience / know-how Dedicated toroidal Magnet with 8 bores (similar to ATLAS) X-ray telescopes Low background detectors Letter of Intent: (CERN-SPSC ) IAXO expectation JCAP 06 (2011)

25 Expected to improve CAST limits by 1.5 orders of magnitude 25

26 CAST has been the pioneering axion helioscope in a large part of axion parameter space Over the year significant R&D done on X-ray detectors of CAST, especially Micromegas New detectors will make CAST a player in low energy frontier Experience of CAST will be transferred to the next pioneering experiment: IAXO 26

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