STAX. Paolo SPAGNOLO. INFN - Pisa

Transcription

1 + STAX Paolo SPAGNOLO INFN - Pisa

2 + Phys. Dark Univ. 12, 37 (2016) Physics of the Dark Universe 12 (2016) Contents lists available at ScienceDirect Physics of the Dark Universe journal homepage: Axion-like particle searches with sub-thz photons L.M. Capparelli a, G. Cavoto b, J. Ferretti c, F. Giazotto d, A.D. Polosa c,e,, P. Spagnolo f a Department of Physics and Astronomy, University of California Los Angeles, 475 Portola Plaza, Los Angeles, CA 90095, USA b INFN Sezione di Roma, P.le Aldo Moro 5, I Roma, Italy c Dipartimento di Fisica and INFN, Sapienza Università di Roma, P.le Aldo Moro 5, I Roma, Italy d NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, I Pisa, Italy e CERN-TH, CH-1211 Geneva 23, Switzerland f INFN Sezione di Pisa, Largo Bruno Pontecorvo, 3, Pisa, Italy article info abstract Article history: Received 23 October 2015 Received in revised form 28 January 2016 Accepted 29 January 2016 Keywords: Axion-like particles Dark-matter constituents Paraphotons Chameleons Light-Shining-through-Wall experiments We propose a variation, based on very low energy and extremely intense photon sources, on the well established technique of Light-Shining-through-Wall (LSW) experiments for axion-like particle searches. With radiation sources at 30 GHz, we compute that present laboratory exclusion limits on axion-like particles might be improved by at least four orders of magnitude, for masses m a mev. This could motivate research and development programs on dedicated single-photon sub-thz detectors Elsevier B.V. All rights reserved. Presented at ICHEP16

3 Axions Experiments 3 classes of experiments: Haloscopic, Helioscopic, LSW Axion, like neutral pion couples to two photons via Primakoff effect) Detected in a magnetic field H ma < 3x10-3 ev from SN1987 Yellow band represent theoretical predictions from DFSZ and KSVZ axion models Haloscopic: cavity Helioscopic depend on stellar models CAST (best limit at the moment) and IAXO (next CERN exp.) use LHC dipoles <E> ~4.2 KeV

4 Light Shining through a Wall Experiments P. Sikivie, Phys. Rev. Lett. 51, 1415 (1983) LAB experiment Laser Source Higher Luminosity Double process Rate ~ G 4 Ṅ evts / Ṅ P!a P a! Ṅ G 4 H 4 L 4 Sensitivity where G is on the G linear (unknown) with L photon axion and H, quartic root co of luminosity (not depending on E γ ) The STAX key points are: - High Luminosity ( gyrotrons in the SubTHz region) - intense H ~ 15 Tesla with L ~ 50 cm dipole - Sub-THz single photon detector using TES Optimal Working Point ~ 30 GHz

5 Light Shining through a Wall Experiments: ALPS Ex: ALPS Desy use the Hera dipoles N~ photons/s

6 High Luminosity Photon Sources photon-axion conversion probability depends on luminosity, not energy sub-thz Reference: 30 GHz ~ 120 µev ~ 1 cm n Klystrons and gyrotrons sources in the GHz range. n Power exceeding 1 MW in this frequency range n Luminosity up to γ/s in CW n Lasers commonly used in LSW experiments ~ γ/s

7 Gyrotrons 7 P(MW)$x$ν" 2 (GHz 2 )$=$const.$ The$opera)ng$region$of$gyrotrons$ Now beyond 1 MW power

8 STAX Experiment L L Dipole Magnet Dipole Magnet Gyrotron H Wall H Single Photon Detector Fabry Perot Cavity Photon Flux Axion Flux Dilution Refrigerator Magnetic field: H = 15 T, L = 0.5 m Source: gyrotron; P 100 kw, Φ γ = s -1, ε γ = 120 µev (ν 30 GHz) Fabry-Perot cavity: Q 10 4 Sub-THz single-photon detection based on TES technology, η 1 Possible second FP cavity behind the wall to enhance axion-photon conversion rate P. Sikivie, D.B. Tanner and K. Van Bibber, Phys. Rev. Lett. 98, (2007)

9 STAX detector n Sub-THz single photon detector etch of a generic hot-electron bolometer. A superconducting bridge made of a low-temperature sup n Transition Edge Sensor TES: ultra-low critical temperature superconductor bridge between two superconducting electrodes. TES coupled to a log periodic antenna. n TES operates within its superconducting transition. DC bias voltage applied. When TES absorbs an incoming photon, it heats up above critical temperature Tc. Change of resistance and current flowing in the circuit, measured by a SQUID n Material: choice of a Superconductor with low critical temperature (Tc 20 mk) to have a good energy resolution α-w or bilayer Ti-Au or Ti-Cu n TES bridge Ti-Cu (gap ~20 µev), superconducting electrodes Nb (gap ~ 1 mev) n Very high efficiency n Ultra low background/dark count

10 STAX detector n Tailoring TES active volume to reduce thermal capacitance ( μm 3 ) E 0.3 p k B T 2 c C e C = γ V T V ~ 300x40x20 nm 3 n low-noise SQUID readout electronics optimization (operating at 80 mk) n Sensitivity δt = δe /C e thermalization T(t) = exp( t /τ) τ = C e /G ic hot-electron bolometer. A superconducting bridge made of a low-temper

11 Noise n Dark count rate (phonon noise) < 6x10-10 s -1 n Black Body: at 10mK peaked around 0.6 GHz with a negligible rate of m -2 s -1 photons irradiated n Cosmic bkg: 1µ/cm -2 /min with 10 ev released in 10nm of material saturates the TES, bkg. under control translated in a negligible dead time of the TES ~ 0.1% N d = Z 1 p eff 2 E T / E exp( x 2 /2) dx. where βeff = 1/!eff is the effective detection bandwidth, and ET is the discrimination threshold energy. is determined by the detector bias or by the readout electronics. = 1 p 2 Z 1 (E T h )/ E exp( x 2 /2) dx.

12 Scheme of the temperatures in the experimental dilution cryostat set-up Figure 8 Scheme of the experimental setup of the TES based on a dilution refrigerator. The cryostat metallic shields reside at different temperatures from 300 K to below 10 mk. The enclosure containing the TES element is at the fridge base temperature whereas the readout SQUID amplifier is kept at 80 mk to improve its noise performance. Input microwave radiation is fed into the fridge, and thereby into the TES detector, via coaxial cables while the low-frequency output signal coming from the SQUID is read via conventional DC lines.

13 Alternative choices to boost the experiment n Work with a new concept Fabry Perot to enhance the Q factor n An upgrade in Q translates into the need of a lower power of the source P/Q 2 Ṅ evts / Ṅ P!a P a! x Q 2 n Fabry Perot with where Q exceeding G is the 10(unknown) have been recently develoved with superconducting cavities n Material choice need to be shaped to work in this particular environment n Low temp n High B field n High Q and lower P can drive the use of other (more refined and easier to handle) photon sources than gyrotrons (klystrons?) n or also to a lighter B fiels (split coil vs solenoid?)

14 P a = g 2 H 2 sin2 qx L x 2 qx 2 q x = m2 a 2E Exclusion Plot Axion-Like Particle. STAX: Time: s, H = 15 T, Lx = 0.5 m Q = 10 4,Eγ = 118 μev, N = γ/s, P = 100 kw 10-6 ALPS(LSW) CAST 10-9 g (GeV -1 ) STAX ALPS II 2x x STAX 2: P = 1 MW, Q reg = 10 4 QCD Axion Inclusion M a (mev)

15 Parameter ALPS STAX galps / gstax STAX II galps / gstaxii Laser Power 0.8 W 100 kw MW 188 Photon Energy ev 124 μev μev 11.7 Cavity Q- factor H * Lx 22 T m 7.5 T m T m 0.3 Detection Efficiency Detector Noise Combined Improvement sec sec sec ~ 10 4 ~ 8x10 5

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17 Tc of Cu/Al bilayers (2) 4/9 alpha=max(t/r dr/dt) Cu(nm) Al(nm) Tc (mk) Rn (ohm) alpha Yuri Venturini

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19 Next Steps n Cu/Ti up down to Tc ~ 20mK n Coupling with a SQUID read-out n Test with a 30 GHz photon source n R&D of the Fabry Perot n Design of the log periodic antenna n R&D of the Fabry Perot n Magnet design

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27 Search for dark photons at STAX L.M. Capparelli et al., Phys. Dark Univ. 12, 37 (2016) 27 n Exclusion limits STAX may achieve in case of null result n STAX limits compared to n ALPS LSW results Phys. Lett. B 689, 149 (2010) n CROWS results Phys. Rev. D 88, (2013) n Spring-8 results Phys. Lett. B 722, 301 (2013) n XENON10 results Phys. Lett. B 689, 149 (2010) n Constraints on dark photons from measurements of the CMB Astrophys. J. 473, 576 (1996) n Searches for modifications of Coulomb s Law Phys. Rev. Lett. 61, 2285 (1988)

28 3 years R&D project Facilities located between INFN-Pisa and NEST-Pisa possibility to use INFN S.Piero Labs 2

29 Financial Plan and Requests Description Quantity Unit Price Cost cryogen-free dilution refrigerator SQUID amplifiers mw Gunn oscillator radiation sources vector network analyser mw NbTi superconducting coaxial cables Tb disk storage CPU (HS06 units) Consumables per year travel cost per year publication cost per year personnel per year Total

30 Financial Plan and Requests Description Total cryogen-free dilution refrigerator SQUID amplifiers radiation sources vector analyser superconducting coaxial cables Storage CPU Consumables travel cost publication cost personnel Total