Development of Far-infrared Spectrophotometers based on Superconducting Tunnel Junction for the Cosmic Background Neutrino Decay (COBAND) Experiment Sep 17-19, 2016 / Epochal Tsukuba Yuji Takeuchi (Univ. of Tsukuba) on behalf of COBAND Collaboration 1
COBAND (COsmic BAckground Neutrino Decay) Heavier neutrinos ( 2 , 3 ) are not stable Neutrino can decay through the loop diagrams ─ γ 𝑋 𝜉 1,2 𝜉 3 e, 𝜈, 𝜐 However, the lifetime is expected to be much longer than the age of the universe We search for neutrino decay using Cosmic Background Neutrino (C B) as the neutrino source 𝟐𝟐𝟏 𝐝𝐧 𝟒 Τ 𝝇(𝝃 𝟒 + ത 𝝃 𝟒 )~ 2
3 COBAND Collaboration Members (As of Sep. 2016) Shin-Hong Kim, Yuji Takeuchi, Kenichi Takemasa, Kazuki Nagata, Kota Kasahara, Shunsuke Yagi, Rena Wakasa, Yoichi Otsuka (Univ. of Tsukuba), Hirokazu Ikeda, Takehiko Wada, Koichi Nagase (JAXA/ISAS), Shuji Matsuura (Kwansei gakuin Univ), Yasuo Arai, Ikuo Kurachi, Masashi Hazumi (KEK), Takuo Yoshida ， Chisa Asano ， Takahiro Nakamura (Univ. of Fukui), Satoshi Mima, Kenji Kiuchi (RIKEN), H.Ishino, A.Kibayashi (Okayama Univ.), Yukihiro Kato (Kindai University), Go Fujii, Shigetomo Shiki, Masahiro Ukibe, Masataka Ohkubo (AIST), Shoji Kawahito (Shizuoka Univ.), Erik Ramberg, Paul Rubinov, Dmitri Sergatskov (Fermilab) ， Soo-Bong Kim (Seoul National University) 3
Motivation of -decay search in C B 3 Lifetime • Standard Model expectation: 𝜐 = Ο(10 43 ) yr𝑡 𝜐 = Ο(10 12 ) yr𝑡 • Experimental lower limit: -Right symmetric model predicts 𝜐 = Ο(10 17 ) yr𝑡 for • Left 𝑀 - 𝑋 𝑆 mixing angle 𝜂 ~0.02 𝑋 If we observed the neutrino radiative decay at the lifetime much shorter than the SM expectation, it would be Physics beyond the Standard Model • Direct detection of C 𝜉 B • Determination of the neutrino mass • 2 − 𝑛 1,2 2 – 𝑛 3 = 𝑛 3 ൗ 2𝐹 𝛿 3 lifetime in Ο 10 13 − 10 17 yr𝑡 Aiming at a sensitivity to 4
Expected photon wavelength spectrum from C B decays distribution in ν 3 → 𝜉 2 + 𝛿 If assume 𝑛 1 ≪ 𝑛 2 < 𝑛 3 , 𝒏 𝟒 = 𝟔𝟏 𝐧𝐟𝐖 Sharp Edge with 𝑛 3 ~50𝑛𝑓𝑊 from 1.9K smearing dN /d (a.u.) neutrino oscillation Red Shift effect measurements [ m] 10 100 500 100 10 50 20 5 E [meV] 50𝜈𝑛(25meV) No other source has such a sharp edge structure!! 5
C 𝜉 B radiative decay and Backgrounds Surface brightness I [MJy/sr] Zodiacal Emission CMB ZE 𝐽 𝜉 ~8MJy/sr AKARI COBE Cosmic Infrared ZL Background (CIB) 𝐽 𝜉 ~0.1~0.5MJy/sr ISD C B decay C B decay DGL 𝜐 = 5 × 10 12 yr𝑡 SL 𝐽 𝜉 ~0.5MJy/sr wavelength [ m] excluded 𝜐 = 1 × 10 14 yr s E [meV] Expected 𝑭 𝜹 spectrum 𝐽 𝜉 ~25kJy/sr for 𝑛 3 = 50meV at λ ＝ 50μm 10 −26 𝑋 𝑛 2 ⋅ 𝐼𝑨 Τ 1Jy = 6
Proposal for COBAND Rocket Experiment Aiming at a sensitivity to 𝜉 lifetime for 𝜐 𝜉 3 = Ο 10 14 yr𝑡 JAXA sounding rocket S-520 http://www.isas.jaxa.jp/e/enterp/rockets/ sounding/s520.shtml Diameter: 520mm Payload: 100kg Altitude: 300km 200 -sec measurement at altitude of 200~300km • Telescope with diameter of 15cm and focal length of 1m • All optics (mirrors, filters, shutters and grating) will be • cooled at ~1.8K 7
Proposal for COBAND Rocket Experiment At the focal point, diffraction grating covering =40-80 80 m (16- 31meV) V) and array of photo-detector pixels of 50(in n wa wavelength ngth distr tributi bution on) ) x 8(in spatial ial distr tributi bution on) ) are placed Each pixel counts ounts FIR phot oton ons in =40−80 m ( Δ𝜇 = 0.8𝜈𝑛 ) Sensitive area of 100 100 mx100 x100 m m for each pixel (100 00 ra rad d x 100 ra rad d in viewing angle) Nb/Al-STJ array 𝜇 Δ𝜄 8 rows 50 columns 𝜇 = 40 − 80𝜈m 𝐹 𝛿 = 16~31meV 8
Sensitivity to neutrino decay Parameters in the rocket experiment simulation are assumed. x100 improvement! Current lower limit (S.H.Kim 2012) 3 lifetime at 4-6 10 14 yrs if no neutrino decay Can set lower limit on • 3 lifetime were 2 10 14 yrs, the signal significance would be at 5 level If • 9
Requirements for the photo-detector in the rocket experiment Zodiacal Emission CIB summary from Matsuura et al.(2011) • 𝑱 𝒂𝑭 =8MJy/sr Surface brightness I [MJy/sr] Zodiacal Emission CMB × 10 -17 W / 8pix 1.1 @ =50 m Zodiacal Light ISD Neutrino Decay C B decay DGL SL • 𝑱 𝝃 =25kJy/sr Integrated flux from galaxy counts × 10 -20 W / 8pix 3.3 wavelength [ m] @ =50 m 𝜐 = 1 × 10 14 yr𝑡 𝒏 𝟒 = 𝟔𝟏 𝐧𝐟𝐖 10
Noise Equivalent Power (NEP) Requirements for the photo-detector Neutrino decay ( 𝑛 3 = 50 meV , 𝜐 𝜉 = 10 14 yrs): : 𝑱 𝝃 =25k 5kJy/ Jy/sr sr @ @ =50 50 m 𝟐𝟔𝒅𝒏 𝟑 𝟑 × 𝚬𝝃 𝟑𝟔 𝒍𝑲𝒛 𝒕𝒔 × 𝟗 × 𝟐𝟏 −𝟗 𝒕𝒔 × 𝝆 Τ Τ 𝑸 𝑶𝑬 = 𝟐𝟏 −𝟑𝟏 𝑿 𝟗𝒒𝒋𝒚 Τ = 𝟒. 𝟒 × Zodiacal emission: 𝑱 𝝃 =8MJy/ MJy/sr sr @ @ =50 50 m 𝟐𝟏 −𝟐𝟖 𝑿 𝟗𝒒𝒋𝒚 𝑸 𝒂𝑭 = 𝟐. 𝟐 × Τ Shot noise in P ZE integrated over an interval t – Fluctuation in number of photons with energy 𝜗 𝛿 : 𝜗 𝛿 𝑄 𝑎𝐹 Δ𝑢 𝑂𝐹𝑄 × Δ𝑢 ≪ 𝜗 𝛿 𝑄 𝑎𝐹 Δ𝑢 ≪ 𝑄 𝑂𝐸 Δ𝑢 2Δ𝑢 Δ𝑢 >200sec 10 −20 ) 𝑋 𝐼𝑨 for 1pix Τ NEP ~O( 11
Existing FIR photo-detectors Operatio ration NEP NEP Detect De ctors ors ( μm ) Temp. p. (W/ W/Hz Hz 1/ 1/2 ) Monolithic 50-110 2.2K ～ 10 -17 Akari-FIS Ge:Ga Stressed Herschel- 60-210 0.3K ~0.9 × 10 -17 Ge:Ga PACS Need more than 2 orders improvement from existing photoconductor-based detectors 10 −20 ) 𝑋 We are trying to achieve NEP ~O( 𝐼𝑨 by using Τ • Superconducting tunneling junction detector • FIR single -photon counting technique 12
Superconducting Tunnel Junction (STJ) Detector Superconductor / Insulator /Superconductor • Josephson junction device E 2 Superconductor 300nm Insulator N s (E) E) Super perconduct onductor or Super perconduct onductor or Insulator Δ: Superconducting gap energy A constant bias voltage (|V|<2 Δ ) is applied across the junction. A photon absorbed in the superconductor breaks Cooper pairs and creates tunneling current of quasi-particles proportional to the deposited photon energy. • Much lower gap energy ( Δ) than FIR photon Can detect FIR photon • Faster response (~ s) Suitable for single-photon counting 13
STJ energy resolution 𝐹 𝛿 Signal = Number of quasi-particles : N q.p. = 𝐻 1.7Δ Resolution = Statistical fluctuation in number of quasi-particles 𝜏 𝐹 = 1.7Δ 𝐺𝐹 Δ: Superconducting gap energy F: Fano factor E: Photon energy Nb/Al-STJ G: Back-tunneling gain • Well -established • Δ~ 0.6meV by the proximity effect from Al • Operation temperature < 400mK • Back -tunnelling gain G~10 • N q.p. =25meV/1.7Δ 10~ 250 E /E~0.1 for E=25meV 25 meV single-photon detection is feasible in principle 14
STJ response to pulsed laser V 0 T~300mK 300mK R 0 =1M VIS laser through STJ V optical fiber 100uV/DIV Refrig. 4us/DIV Nb/Al-STJ response to pulsed laser (465nm) CRAVITY Nb/Al-STJ 100 m sq. Nb/Al-STJ has ~1 s response time. • We can improve NEP by photon counting in 1 s integration time – However we need faster readout system than f>1MHz 15
Nb/Al-STJ development at CRAVITY 50 m sq. Nb/Al-STJ fabricated at CRAVITY I Leakage akage 100nA T~300mK 10nA w/ B field 0.1nA 1nA V 500pA/DIV 100pA Temperature(K) 0.2mV/DIV 0.7 0.3 0.4 0.5 0.6 I leak ~200pA for 50 m sq. STJ, and achieved 50pA for 20 m sq. • The shot noise from the leak current in case of i leak =50pA, =0.6meV and • G=10 1.7Δ 2𝑗 𝑀 10 −19 𝑋 𝐼𝑨 ( Without photon counting) Τ NEP = 𝑓 ~ 4 × G Photon counting will yield improvement by more than one order. • 16
100x100 m 2 Nb/Al-STJ response to 465nm pulsed laser Laser pulse trigger 2V/DIV 40μs/DIV 10M Charge 465nm laser shaper sensitive amp. through optical pre-amp. fiber STJ Response se is consi sist stent t to 10-photo ton T~350m detect ction on in STJ ( 3 He sorption) We observed NIR-VIS laser pulse at few-photon level with a charge-sensitive amplifier placed at the room temperature. Due to the readout noise, a FIR single-photon detection is not achieved yet. Need ultra -low noise readout system for STJ signal Considering a cryogenic pre -amplifier placed close to STJ 17
FD-SOI-MOSFET at Cryogenic temperature FD-SOI : F ully D epleted – S illicon O n I nsulator Very thin channel layer in MOSFET No floating body effect caused by charge accumulation in the body FD-SOI-MOSFET is reported to work at 4K JAXA/ISIS AIPC 1185,286-289(2009) J Low Temp Phys 167, 602 (2012 ) Channel W Channel L 18
Recommend
More recommend
