LIDINE, SLAC National Accelerator, 24th September 2017 NEXT experiment 0 νββ search with High pressure Xe gas TPC Neus López March IFIC (Spain), UTA (US) a next on behalf of the NEXT collaboration
State of the art Future experiments to explore the IH require (m ββ ～ 10meV) : 1) Large masses ( tonne scale) : technology must be scalable and cheap 2) Background in the range of 1 event/tonne/yr (to cover the IH in a reasonable time): large background reduction needed wrt to current state of the art 1 / 2 ] − 1 = G 0 ν ( Q, Z ) | M 0 ν | 2 m 2 [ T 0 ν ββ � X � m i U 2 � m ββ = � ei 2 i
Content NEXT-100 ( ～ 100 kg) Prototypes ( ～ 1 kg) sensitivity: 6x10 25 yr [2009 - 2014] [2018 - 2020’s] Demonstration of Neutrinoless double detector concept beta decay searches [<1% FWHM, NEXT-NEW ( ～ 5 kg) imaging] [2015 - 2018] Underground and radio- pure operations, background, 2 νββ 3
Content NEXT-tonne future generation: With a background rate of ～ 1c/tonne/year will cover in 6 years the IH * ongoing R&D on Single Molecule Fluorescent imaging for Barium NEXT-100 ( ～ 100 kg) Prototypes ( ～ 1 kg) tagging (A.McDonald talk later) sensitivity: 6x10 25 yr [2009 - 2014] [2018 - 2020’s] Demonstration of * ongoing R&D with gaseous mixtures can provide low di ff usion, Neutrinoless double detector concept improving rejection by a factor x4. (C. Henriques talk later) beta decay searches [<1% FWHM, NEXT-NEW ( ～ 5 kg) imaging] [2015 - 2018] Underground and radio- pure operations, background, 2 νββ 4
Content NEXT-WHITE (NEW) Detector description Detector calibration 5
a next : N eutrino E xperiment with a X enon T PC ‣ High pressure Xenon gas, electroluminescent TPC with readouts for calorimetry and imaging . ✦ Isotope: 136 Xe (easy to enrich and to purify) ✦ Electroluminescence used to amplify the ionization signal (linear process, huge gain) ✦ Excellent energy resolution: <1% FWHM at the Q-value (the resolution due to Fano factor fl uctuations of Xe Gas at Q-value is 0.3% FWHM) ✦ Easy to scale up ✦ Low background rate: 4x 10 -4 c/keV/kg/yr ✦ Event topology reconstruction : electrons travel 15cm each (15bar) on average ✦ Single Molecule Fluorescent imaging for Barium tagging 6
NEXT concept ‣ Energetic electron leaves a high-density ‣ Energy plane made of PMTs deposition at the end of its track measures energy and start of the event (t0) ‣ Results in distinct topological signatures for signal and background events of the ‣ Tracking plane made of SiPMs, same energy reconstructs the event topology. 7
NEXT concept ‣ Energetic electron leaves a high-density ‣ Energy plane made of PMTs deposition at the end of its track measures energy and start of the event (t0) ‣ Results in distinct topological signatures for signal and background events of the ‣ Tracking plane made of SiPMs, same energy Background rejection of 76% for 68% signal e ffi ciency reconstructs the event topology. 5
Underground and radio-pure operations. NEW TPC Goal is to measure: background, 2 νββ Time Projection Chamber: Pressure vessel: 5 kg active region(@10bar), 50 cm drift length 316-Ti steel, 30 bar max pressure Energy plane: 12 PMTs, operating at vacuum. 30% coverage Tracking plane: 1,800 SiPMs, 1 cm pitch Mother can: Inner shield: 12 cm copper plate that copper, 6 cm thick Outer shield: separates pressure from lead, 20 cm thick vacuum and ads shielding. 9
NEW Field Cage Gate mesh Fused silica interwoven anode steel mesh (22kV) Coated with ITO (grounded) and with TPB Cathode grid Stainless-steel (SS) wire spaced 1cm Te fl on light (50kV) tube Coated with TPB Cu rings 10
NEW sensors: Energy and Tracking planes s a p p h i r e w i n d ow s t e fl o n m a s k s t o coated with TPB increase light collection Gain ～ 10 6 Gain ～ 10 6 easy to calibrate easy to calibrate with spe with spe Kapton (radiopure) 12 R11410-10 PMTs (Hamamatsu) 1792 SiPMs (SENSL) ✦ Excellent response (low noise very low ✦ 28 Kapton Dice Boards with 64 SiPMs dark current) in gas. each (1cm pitch) ✦ Radiopure (less than 1 mBq/PMT in ✦ SENSL SiPMs most radiopure in the 11 Tl-208 and Bi-214) market
NEW Calibration: 83 Kr ‣ Kr leaves a point-like deposition of 41.5 keV , uniformly distributed in the detector ‣ Detector characterization: drift velocity ( z dependence ), e- attachment ( lifetime ), geometric corrections to energy ~1.6 ms Gas impurities reduce lifetime Light collection depends on the and impact energy measurements position of the event (solid angle (z dependance) e ff ects and TPB inhomogeneities) 12
NEW Calibration 83 Kr: energy resolution y r a n i m i l e r P ‣ 5% FWHM energy resolution → 1/ √ E extrapolation yields 0.65% FWHM resolution at Q-value ‣ 4% FWHM (0.5% FWHM at Q-value ) up to 100mm radius Full active volume r < 100mm, drift time < 100µs 13
y r a n NEW Calibration: 22 Na i m i l e r P x-rays ‣ Good energy resolution maintained at higher Single-escape Photo-peak energies (511 keV gamma from 22 Na) ‣ Lifetime corrections from x-rays, Geometrical corrections from 83 Kr Compton edge ‣ 2.3% FWHM ( 1.05% FWHM at Q ββ ) energy resolution for 511 keV γ Xenon x-rays Select 22 Na photo-peak events 29.7 keV 33.8 keV 14
y r a n i m i l e NEW tracking reconstruction r P ‣ Observe the two stopping electron tracks (at 1.6MeV) from a Co56 source emitted from a common vertex, characteristic of double beta decays ‣ Powerful handle for single-electron background suppression >1.02 MeV γ -ray from 200 Co-56 calibration source 0.14 150 0.12 100 Energy (a.u.) Y pos (mm) 50 0.10 e - 0.16 200 0 0.08 150 0.14 -50 e + 0.06 -100 100 0.12 Energy (a.u.) 0.04 detector Y pos (mm) -150 50 -200 0.10 0.02 0 -200 -150 -100 -50 0 50 100 150 200 Two 0.51 MeV annihilation 50 X pos (mm) − 0.08 γ -rays escape 100 − 0.06 150 − Reconstruction with ML-EM 0.04 200 − provides well-de fi ned tracks 15 200 150 100 50 0 50 100 150 200 − − − − X pos (mm)
y r a n i m i NEW Background: 222 Rn l e r P ‣ 214 Bi (present in the 222 Rn decay chain) is one of the major background sources in NEXT. ‣ 222 Rn emanates from detector materials and is present in the air ‣ We have measured the alpha energy for the three alpha markers ( 222 Rn, 218 Po, 214 Po) Rate (Hz) T 1/2 = 3.9 d from 222 Rn 10 Hot getter ‣ Alpha production rate measured in 1 NEW during normal (hot getter) operations point to very low 222 Rn- 1 − 10 ( 222 Rn i n d u c e d b a c k g r o u n d s f o r source) NEXT-100, <10 -4 c/ (keV ⋅ kg ⋅ yr) 6 mHz Hot getter Cold getter 2 − (low) 10 17-03-30 17-04-06 17-04-13 17-04-20 17-04-27 17-05-04 17-05-11 16 Date
Summary ‣ Demonstrate the ability to scale up xenon TPC technology (NEXT100 is a key step in scaling up) ‣ Demonstrate the ability to maintain good energy resolution near 0.5% FWHM at Q-value ‣ Background rejection: - topological signature provides additional rejection; new reconstruction methods and DNN -based event classi fi cation [arXiv:1609.06202] under investigation - reduce di ff usion with coolant gas : see C. Henriques talk - Ba tagging would provide essentially zero-background: see A. MacDonald talk ‣ Continue radiopurity campaign measurements and selection of radiopure materials ‣ Exploring the IH appears feasible ( tonne scale experiments with negligible backgrounds ) but will require an intense experimental e ff ort ( ～ 10 years) and a serious investment. 17
Thanks for your attention! a next IFIC Valencia • Zaragoza • Politécnica Valencia • Santiago de Compostela • Girona Coimbra • • Texas A.M • Texas JINR A. Nariño Aveiro Arlington, • Fermilab • Argonne • Iowa state Co-spokepersons: D. Nygren (UTA) & J.J. Gómez-Cadenas (IFIC)
NEW Field Cage design ✦ 3 regions: drift ( ～ 500V/cm), EL (E/p = 2 kV/cm/bar (575 ph./e-)), bu ff er ✦ HDPE of 49 cm external diameter that provides electric insulation from the vessel 10cm Anode Gate Cathode 0V -22kV -50kV (-7kV) (-28kV)
NEXT100 sensitivity JHEP 1605 (2016) 159 * positive measurement Expect a half-life of 6 x 10 25 years [80-160meV] for an exposure of 275 kg yr. Screening of detector components (initial Still ample room for improvement! Tl, Bi activities) + selection, the overall background rate is estimated to be: 45 < 4 x 10 -4 counts/(keV kg yr)
NEXT prototypes NEXT-DEMO (IFIC) NEXT-DBDM (LBNL) ✦ Energy resolution (19 1” PMTs) ✦ Energy resolution (19 1” PMTs) ✦ ～ 1kg Xe gas at 10-15 bar ✦ Tracking (256 SiPMs) ✦ Also measured response of HPXe to ✦ ～ 1.5 kg of Xenon 1 bar nuclear recoils
NEXT-DEMO tracking/energy plane
NEXT-DEMO energy resolution NEXT-DEMO NEXT-DBDM ✦ 662 keV gammas from 137 Cs ✦ 511 keV gammas fro 22 Na ✦ 1.0% FWHM resolution in small ✦ 1.6% FWHM resolution over large fi ducial volume fi ducial volume ✦ Extrapolates to 0.5% HWHM at Q- ✦ Extrapolates to 0.63% FWHM at value Q-value
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