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The nEXO detector: design overview Andrea Pocar University of - - PowerPoint PPT Presentation

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TAUP 2019 16th International Conference on Topics in Astroparticle and Underground Physics 9-13 September, 2019 Toyama, Japan The nEXO detector: design overview Andrea Pocar University of Massachusetts, Amherst Andrea Pocar - UMass

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Andrea Pocar - UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019

Andrea Pocar

University of Massachusetts, Amherst

The nEXO detector: design overview

TAUP 2019 — 16th International Conference on Topics in Astroparticle and Underground Physics 9-13 September, 2019 — Toyama, Japan

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019

  • Neutrinoless double beta decay
  • Tonne-scale experiments: nEXO
  • The nEXO detector
  • concept and design
  • from EXO-200 to nEXO: new technology
  • sensitivity
  • Outlook

2

Outline β β

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 3

0νββ decay and neutrino mass (Seesaw I mechanism)

“tonne-scale” 
 (T1/2~1028 y)

1 T 0ν

1/2

= G0ν(Q, Z)|M0ν|2 < mββ >2

current experiments


(~100 kg, T1/2~1026 y)

  • bservation of 0νββ decay
  • massive, Majorana neutrinos
  • lepton number violation (ΔL = 2)
  • new mass mechanism
  • new mass scale

0νββ rate

  • absolute neutrino mass 


(model dependent)

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 4

Dura lex, sed lex

NA = 6.022 × 1023

  • DBD candidate isotopes: 48→150 grams/mole
  • 1028 nuclei = 16,600 moles → 800—2,500 kg
  • Real-life non-idealities: 


detection efficiency, isotopic fraction, backgrounds, detector live time, ….

  • Need ~tonne(s) of DBD-decaying isotope

Amedeo Avogadro

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 5

The nEXO detector (artist view in the SNOLAB cryopit)

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 6

Liquid Xenon Time Projection Chambers (TPCs)

Liquid xenon TPC’s

  • active self-shielding (improves with size)
  • good energy resolution 


combining ionization+scintillation

  • particle ID (scintillation vs. ionization)
  • event topology (single-/multi-site events)

Scale-up: EXO-200 (200 kg) ➔ nEXO (5,000 kg)

  • Monolythic
  • In-line purification of xenon

2.5MeV γ attenuation length: 8.5cm:

β, ββ

γ

see R Saldanha, in Neutrino #20 for details on the physics case for nEXO

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 7

from EXO-200 to nEXO

EXO-200 concluded its operations in Dec 2018

see M. Jewell, in Neutrino #7 for latest EXO-200 results

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 8

nEXO: a 5-tonne LXe TPC

1.3 m electron drift d i a m e t e r 
 ( 1 . 3 m ) charge readout pads (anode) SiPM ‘staves’ coating the barrel (behind the field cage) cathode in-xenon cold electronics (charge and SiPMs)

Cathode placed at one end of the cylinder to maximize the continuous volume of LXe

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 9

Cryogenics, xenon purity

Cryogenics

LXe vessel immersed in >30 tonnes of HFE7000 fluid 
 (design inherited from EXO-200)

  • light-weight xenon vessel
  • gamma-ray and neutron shielding
  • thermal stability

Xenon purity (chemical and radioactive)

  • >10 ms drifting electron lifetime …… minimal use of plastics
  • ~5 ms reached by EXO-200 (with thin teflon reflectors)
  • 600 steady-state radon atoms in the bulk
  • ~200 steady state atoms achieved in EXO-200
  • need to limit decays of radon progeny at the cathode
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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 10

nEXO publications: detector, sensitivity, R&D

  • "Simulation of charge readout with segmented tiles in nEXO"

arXiv:1907.07512

  • "Characterization of the Hamamatsu VUV4 MPPCs for nEXO"

arXiv:1903.03663, Nucl Inst Meth A 940 371 (2019)

  • “Imaging individual Ba atoms in solid xenon for barium

tagging in nEXO” Nature 569 (2019) 203 *

  • "Study of Silicon Photomultiplier Performance in External

Electric Fields“ JINST 13 (2018) T09006

  • “VUV-sensitive Silicon Photomultipliers for Xe Scintillation

Light Detection in nEXO” IEEE Trans NS 65 (2018) 2823

  • “nEXO pCDR” arXiv:1805.11142 (2018)
  • "Sensitivity and Discovery Potential of nEXO to 0νββ decay"
  • Phys. Rev. C 97 065503 (2018)
  • "Characterization of an Ionization Readout Tile for nEXO“

J.Inst. 13 P01006 (2018)

  • "Characterization of Silicon Photomultipliers for nEXO“

IEEE Trans. NS 62 1825 (2015) * Not nEXO baseline

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 11

nEXO TPC: highlights

SiPM arrays charge collection tiles

10 cm ~6 cm

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 12

Ionization charge detection

Prototype 3mm pitch, crossed strips deposited on a 10 cm x 10 cm quartz tile produced and tested in liquid xenon.

JINST 13, P01006 (2018)

10 μm 3 mm Bi-207 source

no shielding Frisch grid

80 fF at crossings 0.86 pF between adjacent strips

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 13

Ionization charge readout details

arXiv:1907.07512

The sensitivity only mildly depends on the chosen pitch of the strips Proper inclusion of the induction signals allows a ~20-30% sensitivity boost

Flow chart of the simulation of electron drift and readout in nEXO

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 14

Scintillation light detection

  • ~ 1500 V bias
  • Low gain (G~200)
  • Large (dG/G)/dT ~ 5%/K
  • Large (dG/G)/(dV/V) ~ 15
  • VUV photon detection efficiency per area,

25%*

  • Low leakage current at LXe temperature

* Accounting for inactive area

  • 30 - 80 V bias
  • High Gain (105 – 106)
  • Lower (dG/G)/dT ~ 0.6%/K
  • Lower (dG/G)/(dV/V) ~ 0.3
  • VUV photon detection efficiency

per area, up to 15%

  • Dark noise and correlated noise

EXO-200 used 500 Bare LAAPDs. Noise increases with capacitance, while signal size remains constant, difficult to reach σ/E ~ 1%. Individual photon counting with high gain and low noise. Resolution limited by dark counts and correlated avalanches nEXO uses VUV-sensitive SiPMs

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 15

Photon detection efficiency

To achieve 1% energy resolution, an

  • verall 3% photon detection efficiency is

required, consisting of two parts:

  • PDE of SiPMs
  • Photon transport efficiency

A, Jamil, et al. IEEE Trans.Nucl.Sci. 65, 2823 (2018)

  • G. Gallina et al. Nucl. Instrum. Meth., 940, 371 (2019)

nEXO goal see T. Brunner, in New Technologies #1 for more details on photosensor development for nEXO Some 1cm2 VUV devices meet nEXO specs, with a bias of ~30V

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 16

Scintillation light mirrors

The absence of a traditional’ teflon reflector together with the placement

  • f SiPMs on the xenon vessel barrel behind the TPC field cage requires

the electrodes, especially the field shaping rings, to be made reflective

Losses in photon transport efficiency need to be compensated with increased SiPM PDE Looking at thin-film aluminized electrodes

Measurements of SiPM reflectivity in LXe also ongoing

see T. Brunner, in New Technologies #1 for more details on photosensor development for nEXO see T. McElroy, in DM 14 New Ideas in Sub-GeV dark matter for “post-nEXO” ideas on light detection

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 17

Cold, in-LXe readout electronics

<1% energy resolution background discrimination 200 electrons rms 2 MS/s

prototype charge readout system

Six 1cm2 FBK SiPM on a ceramic carrier board

R= 0.12 SPE

p r e l i m i n a r y

Charge Light ASIC development at BNL and SLAC

(alternative approach developed at IHEP)

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 18

nEXO sensitivity vs. exposure (preliminary baseline)

  • gA= gAfree=-1.2723
  • Band is the envelope of NME:

EDF: T.R. Rodríguez and G. Martínez-Pinedo, PRL 105, 252503 (2010) ISM: J. Menendez et al., Nucl Phys A 818, 139 (2009) IBM-2: J. Barea, J. Kotila, and F. Iachello, PRC 91, 034304 (2015) QRPA: F. Šimkovic et al., PRC 87 045501 (2013) SkyrmeQRPA: M.T. Mustonen and J. Engel PRC 87 064302 (2013)

5.0x1025 yr
 arXiv1906.02723

see J Orrell, poster 422 for details on the background models and control for nEXO

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 19

Outlook

  • The search for LNV and 0νββ decay continues to be a central mission of the

nuclear/particle/fundamental symmetries community worldwide

  • Xenon is a prime candidate for a tonne-scale 0ν DBD experiment
  • EXO-200 was the first 100-kg -scale experiment to run. 


It has inspired the 25-fold scale up, nEXO, and concluded its run in December 2018 with rich analysis still ongoing

  • Liquid xenon TPC’s have successfully scaled up 100-fold in ~15 years
  • The nEXO design is mature and grounded in proven technology. The nEXO

design is ready and mature and aims at becoming a leading technology with very substantial US and international support

  • nEXO has developed a firm 5-tonne detector ‘baseline’, inclusive of a

detailed background model and solid (somewhat conservative) sensitivity estimation.
 R&D on critical detector items steadily progressing

stay hungry, my friend

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 20

The nEXO collaboration

University of Alabama, Tuscaloosa AL, USA — M Hughes, P Nakarmi, O Nusair, I Ostrovskiy, 
 A Piepke, AK Soma, V Veeraraghavan University of Bern, Switzerland — J-L Vuilleumier University of British Columbia, Vancouver BC, Canada — G Gallina, R Krücken, Y Lan Brookhaven National Laboratory, Upton NY, USA — A. Bolotnikov, M Chiu, G Giacomini, V Radeka, 
 E Raguzin, S Rescia, T Tsang, M. Worcester University of California, Irvine, Irvine CA, USA — M Moe California Institute of Technology, Pasadena CA, USA — P Vogel Carleton University, Ottawa ON, Canada — I Badhrees, B Chana, D Goeldi, R Gornea, T Koffas, 
 C Vivo-Vilches Colorado School of Mines, Golden CO, USA — K Leach, C Natzke Colorado State University, Fort Collins CO, USA — A Craycraft, D Fairbank, W Fairbank, A Iverson, 
 J Todd, T Wager Drexel University, Philadelphia PA, USA — MJ Dolinski, P Gautam, EV Hansen, M Richman,
 P Weigel Duke University, Durham NC, USA — PS Barbeau Friedrich-Alexander-University Erlangen, Nuremberg, Germany — G Anton, J Hößl, T Michel, 
 S Schmidt, M Wagenpfeil, W G Wrede, T Ziegler IBS Center for Underground Physics, Daejeon, South Korea — DS Leonard IHEP Beijing, People’s Republic of China — GF Cao, WR Cen, YY Ding, XS Jiang, P Lv, Z Ning, 
 XL Sun, T Tolba, W Wei, LJ Wen, WH Wu, J Zhao ITEP Moscow, Russia — V Belov, A Karelin, A Kuchenkov, V Stekhanov, O Zeldovich University of Illinois, Urbana-Champaign IL, USA — D Beck, M Coon, J Echevers, S Li, L Yang Indiana University, Bloomington IN, USA — SJ Daugherty, G Visser Laurentian University, Sudbury ON, Canada — E Caden, B Cleveland, A Der Mesrobian-Kabakian, 
 J Farine, C Licciardi, A Robinson, M Walent, U Wichoski Lawrence Livermore National Laboratory, Livermore CA, USA — JP Brodsky, M Heffner, A House, 
 S Sangiorgio, T Stiegler University of Massachusetts, Amherst MA, USA — S Feyzbakhsh, KS Kumar, O Njoya, A Pocar, 
 M Tarka, S Thibado McGill University, Montreal QC, Canada — S Al Kharusi, T Brunner, C. Chambers, D Chen, 
 L Darroch, Y Ito, K Murray, T Nguyen, T Totev University of North Carolina, Wilmington, USA — T Daniels Oak Ridge National Laboratory, Oak Ridge TN, USA — L Fabris, RJ Newby Pacific Northwest National Laboratory, Richland, WA, USA — IJ Arnquist, ML di Vacri, EW Hoppe, 
 JL Orrell, GS Ortega, CT Overman, R Saldanha, R Tsang Rensselaer Polytechnic Institute, Troy NY, USA — E Brown, A Fucarino, K Odgers, A Tidball Université de Sherbrooke, QC, Canada — SA Charlebois, D Danovitch, H Dautet, R Fontaine,
 F Nolet, S Parent, J-F Pratte, T Rossignol, N Roy, G St-Hilaire, J Sylvestre, F Vachon SLAC National Accelerator Laboratory, Menlo Park CA, USA — A. Breuer, R Conley, A Dragone, 
 G Haller, J Hasi, LJ Kaufman, C Kenney, B Mong, A Odian, M Oriunno, A Pena Perez, PC Rowson, 
 J Segal, K Skarpaas VIII University of South Dakota, Vermillion SD, USA — T Bhatta, A Larson, R MacLellan Stanford University, Stanford CA, USA — R DeVoe, G Gratta, M Jewell, S Kravitz, BG Lenardo, 
 G Li, M Patel, M Weber TRIUMF, Vancouver BC, Canada — J Dilling, Y Lan, F Retière, M Ward Yale University, New Haven CT, USA — A Jamil, Z Li, DC Moore, Q Xia

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Andrea Pocar — UMass Amherst TAUP — Toyama, Japan — 9-13 September 2019 21

EXO-200 papers

  • G. Anton et al. “Measurement of the scintillation and ionization response of liquid xenon at MeV energies 


in the EXO-200 experiment” arXiv:1908.04128

  • G. Anton et al. “Search for Neutrinoless Double-Beta Decay with the Complete EXO-200 Dataset” arXiv:1906.02723
  • S. Delaquis et al. "Deep Neural Networks for Energy and Position Reconstruction in EXO-200” JINST 13 (2018) P08023

J.B. Albert et al. "Search for nucleon decays with EXO-200” PRD97(2018) 072007 J.B. Albert et al. "Search for 0νββDecay with the Upgraded EXO-200 Detector” PRL120(2018) 072701 D.S. Leonard et al. "Trace radioactive impurities in final construction materials for EXO-200” NIMA 871 (2017) 169 J.B. Albert et al. "Searches for Double Beta Decay of134Xe with EXO-200” PRD96 (2017) 092001 J.B. Albert et al. "Measurement of the Drift Velocity and Transverse Diffusion of Electrons in Liquid Xenon with the EXO-200 Detector” PRC95 (2017) 025502 C.G. Davis et al. "An Optimal Energy Estimator to Reduce Correlated Noise for the EXO-200 Light Readout” JINST11(2016) P07015 J.B. Albert et al. "Cosmogenic Backgrounds to 0νββ in EXO-200” J. Cosmol. Astropart. Phys. 4 (2016) 029 J.B. Albert et al. "First Search for Lorentz and CPT Violation in ββ Decay with EXO-200” PRD 93 (2016) 072001 J.B. Albert et al. "Search for 2νββ decay of 136Xe to the 01+ excited state of 136Ba with EXO-200” PRC 93 (2016) 035501 J.B. Albert et al. "Measurements of the ion fraction and mobility of alpha and beta decay products in LXe using EXO-200” PRC 92 (2015) 045504. J.B. Albert et al. "Investigation of radioactivity-induced backgrounds in EXO-200” PRC 92 (2015) 015503 J.B. Albert, et al. "Search for Majoron-emitting modes of ββ decay of136Xe with EXO-200” PRD 90 (2014) 092004 J.B. Albert, et al. "Search for Majorana neutrinos with the first two years of EXO-200 data” Nature 510 (2014) 229 J.B. Albert, et al. "An improved measurement of the 2νββhalf-life of 136Xe with EXO-200” PRC 89 (2014) 015502

  • M. Auger, et al. "Search for Neutrinoless ββ Decay in136Xe with EXO-200” PRL 109 (2012) 032505
  • M. Auger, et al. "The EXO-200 detector, part I: Detector design and construction” J. Inst7(2012) P05010
  • A. Dobi, et al. "Xenon purity analysis for EXO-200 via mass spectrometry” NIM A675(2012) 40
  • N. Ackerman, et al. "Observation of Two-Neutrino ββ Decay in Xe-136 with EXO-200” PRL 107 (2011) 212501
  • A. Dobi, et al. "A Xenon Gas Purity Monitor for EXO" NIM A 659 (2011) 215
  • F. LePort, et al. "A magnetically-driven piston pump for ultra-clean applications" Rev. Sci. Inst. 82 (2011) 105114
  • R. Neilson, et al. "Characterization of large area APDs for the EXO-200 detector" NIM A 608 (2009) 6875
  • D. Leonard, et al. "Systematic study of trace radioactive impurities in candidate construction materials

for EXO-200" Nucl. Ins. Meth. A 591 (2008) 490