The DarkSide-20k program: towards the most sensitive Dark Matter detector
IX Jornadas CPAN Santander 23-25 Octubre 2017
Roberto Santorelli The Dark Matter problem
• The CDM model has been successful explaining CMB, large scale structure etc.. • It ts all the observations with only 6 parameters • A Cold Dark Matter model is necessary for the formation of structure and galaxies in the universe
R. Santorelli - IX Jornadas CPAN 2 DM…where?
WIMPs
Dark Matter Dark Matter Dark Matter Dark Matter Dark Matter Dark Matter
R. Santorelli - IX Jornadas CPAN 3 Detection q,l q
q,l q q q Above ground Collider Underground Underground DM-Experiments
F: SNOLab DEAPCLEAN Picasso I: YangYang COUPP A: GranSasso: KIMS DAMIC XENON C: Boulby CRESST H: Kamioka G: Soudan Drift DAMA/LIBRA XMASS SuperCDMS DarkSide Newage CoGeNT D: Canfranc ArDM B: Modane J: Jinping E: Homestake Rosebud EDELWEISS Panda-X LUX-LZ ANAIS MIMAC CDEX A dream detector
• Large Exposure (Mass Time) : 100s ton year
• Low Energy Threshold : ~10 keVNR
• Event topology : /, ,
• 3D Event Reconstruction : neutrons
• Discrimination between Signal and Backgrounds
: > 99.9…%
• Low Background Rate : <0.1 evt in the exposure
R. Santorelli - IX Jornadas CPAN 6 LAr vs LXe LXe: Density Price ~50% odd isotopes ( 129Xe, ER discrimination 131Xe ) for spin dependent interactions No long-lived radioactive isotopes
LAr: Available in large quantity Radioactive isotopes ER background discrimination 39Ar 1.01 Bq/kg (NIM-A 574 (2007) 83–88) NIM-A 574 (2007) 83–88
R. Santorelli - IX Jornadas CPAN 7 Event discrimination technique in Ar ER-like event NR-like event
S1 only
S1/S2
S2 S2 Due to an enhancement of the recombination process S1 ER S1 NR R. Santorelli - IX Jornadas CPAN 8 ER discrimination and bkg
• Crude Argon from CO2 well in Colorado • Ar-39 suppressed by a factor 1400 (before analysis) • Cryostat and PMTs main RA components of the detector R. Santorelli - IX Jornadas CPAN 9 Physics case • There is a remarkable and unique opportunity of having large exposures (~100 kgyr) in background free mode with an argon TPC: the future scientific program of the DM direct search community must include a dedicated worldwide effort based on this technology!
• At the moment, the dual-phase LAr TPC is the only technology able to exceed the current experimental limits, reaching the neutrino floor
• A DM search with xenon designed to reach the neutrino floor would require a “background-free” exposure of 300 tonyr.
• Considering a β/γ rejection power in xenon of the order of 99.5% and 300 tonyr. Sensitivity limited by
o pp neutrinos (20 events/ton×yr in the 0-10 keVER) o 222Rn (15 events/tonne×yr for every 1 mBq of 222Rn) R. Santorelli - IX Jornadas CPAN 10 Status • In 2015, the CIEMAT-DM group was one of the original proponents of the new DarkSide-20k Collaboration (DS-20k), which plans to build a 20 tonne fiducial dual- phase Ar-TPC at LNGS, reaching an exposure of 100 ton×yr
• The experiment plans to take data from 2021, and is designed to be the most sensitive detector for massive WIMPs (up to 10 TeV/c2)
• In a second stage, the program foresees the construction and operation of the ARGO experiment, with an exposure of 1000 ton×yr (a 300-tonne detector with a 200-tonne fiducial mass) in background free mode
• The sensitivity expected is three orders of magnitude greater than the best result achieved today
• April 2015: LOI to LNGS • March 2016: proposal reviewed by a INFN and the NSF joint panel • April 2016: proposal reviewed by the NSF Particle Astrophysics ranking panel (earning a rating of “Excellent" in both merit categories “Intellectual Merit" and “Broader Impact". • April 2017: funding approval form INFN (40 M€ contribution) • Positive review of the proposal submitted to the US-NSF, capital funding of 13 M$
R. Santorelli - IX Jornadas CPAN 11 Strategy • Dual-phase electroluminescent Ar-TPC based on the DS-20 and ArDM designs (3D reconstruction and fiducialization and multiplicity)
• Electron recoil suppression by a factor in excess of 107 at low energy (internal / contamination)
• Active vetoes (WC+LS) ( and cosmogenics neutrons)
• Optimization of the detector in terms of total mass and setting very stringent limits in terms of radiopurity of the materials (internal fission and α,n neutrons)
• Radiopure silicon-based photosensors (SiPM), with an internal area above 14 m2 o Radiopurity o Photon counting o Detection efficiency o Segmentation, sub-centimeter position resolution and fiducialization
• Threshold <30 keVNR and the neutron background free mode
R. Santorelli - IX Jornadas CPAN 12 Baseline design
• New collaboration with groups from DS-20, ArDM and DEAP-3600. • More than 70 institutions, 350 researchers,
12 countries 8 m 16 m • Data taking from 2021 • 100 tonyr exposure with < 0.1 evt bkg • Sensitivity ~1047 for 1 TeV/c2 WIMP mass
15 m • 30 ton UAr, 20 ton fiducial • Hexagonal shape • 13 m2 SiPM, LY above 8 PE/keV • More than 5 ms mean electron lifetime • WCV (100 20” MCP-PMTs developed for JUNO) • LSV (130 MCP, 13 % photocathode cov,10B) • Extended Argon project: ARIA and URANIA 3 m 13 Sensitivity
R. Santorelli - IX Jornadas CPAN 14 The CIEMAT DM-group Noble liquids technology R&D on charge-light Dark Matter
Postdoc: Staff: Vicente Pesudo MS: Pablo Garcia Engineer: Carmen Milla Pardo Luciano Romero Manuel Daniel Irene Jiménez Cuesta Roberto Santorelli PhD student: María Ruiz Ortega Edgar Sanchez
R. Santorelli - IX Jornadas CPAN 15 CIEMAT at DS-20k
• Veto/TPC design and mechanical construction
• Material screening o ICP-MS at CIEMAT o HpGe at LSC o BiPo (surface contamination) at LSC
• Computing, simulation, calibration sources
• ArDM @ LSC: ton-scale detector
R. Santorelli - IX Jornadas CPAN 16 The CIEMAT at DS-20k
R. Santorelli - IX Jornadas CPAN 17 ArDM: tonne-scale LAr-TPC at the LSC
• Collaboration between CIEMAT, ETH and LSC (RE18) • Low background setup (LSC underground lab) • 2015-2016 Data taking and analysis of the first physics run in single- phase – Validation of detector performances – LY – Study of the backgrounds
• Double-phase EL-TPC • 850 kg active volume (2 t total) • Cryogenic low radioactive PMT arrays (R5912 2×12) • 50 cm passive neutron shield (Poly, 20 ton) • Control of the cryocoolers and cryogenic system fully integrated in the existing PLC • 4x ADC V1720, 8ch, 12bit, 2Vpp, 250MS/s (up to 2.2 kHz trigger rate (289 MB/s – 8 μs digitalization) R. Santorelli - IX Jornadas CPAN 18 R. Santorelli - IX Jornadas CPAN 19 ArDM Phases of the project
Surface operations : Building the ArDM prototype Commissioning the detector cryogenics, purification, HV, electronics, light readout and software Underground - commissioning and RUN-I: Construction and installation of the passive neutron shield Full material screening campaign at LSC Warm/cold GAr and LAr runs 4.7 billion triggers (10% calibration) 83mKr, 57Co, 22Na, 252Cf calibrations LY and attenuation length studies Gamma background assessment ER/NR discrimination through pulse shape Underground - double-phase operations and RUN-II: Hardware upgrades Physics runs Integration ArDM/DarkSide-20k
UAr measurements R. Santorelli - IX Jornadas CPAN 20 Calibration Light yield over 5 months
• Sensitive to low energy ~30 keVee • Good spatial uniformity of the detector • Long-term stability during the commissioning
R. Santorelli - IX Jornadas CPAN 21 Assessment of the gamma bkg • Good data/MC agreement • ER background – Ar-39: the dominant background, 0.95 Bq/kg – γ ray: amount to 26% ER background • High energy background – Muon: 3.5×10 3m 2s 1 – Rn emanation: 65.6 0.4 µHz/liter
ER Rn and Rn progeny spectrum
= .
R. Santorelli - IX Jornadas CPAN 22 ER/NR discrimination 252Cf calibration Signal • Scintillation pulse shape discriminator: region f90
• Rejection power: statistical separation
108 ER Rejection 50% NR Acceptance
Calvo, J., et al. JCAP 2017.03 (2017) R. Santorelli - IX Jornadas CPAN 23 ArDM/DS-20 : UAr studies and SiPM tests at LSC
Services
Geant4 simulations of the background
- Sources: SiPM, PCB, copper, steel, external... - Radioactive chain of 40k, 232Th, 238U, 222Rn - Large number of events simulated to have a significant spectrum in Dart (2 1012).
UAr ~ 0.7 mBq/kg : 5 ~0.2 weeks DAr ~ 0.07 mBq/kg : 3 ~7.7 weeks 24 R. Santorelli - IX Jornadas CPAN 25 The CIEMAT DM-group Noble liquids technology Charge - light Dark Matter
Postdoc: MS: Staff: Vicente Pesudo Carmen Milla Pardo Pablo Garcia Engineer: Irene Jiménez Cuesta Luciano Romero Manuel Daniel María Ruiz Ortega Roberto Santorelli PhD student: Edgar Sanchez R. Santorelli - IX Jornadas CPAN 26 R&D Topics Novel ideas on • light detection / transmission • detector calibration • detector design developments • validate the charge readout studying the dynamics of the positive charge
SiPM characterization at cryogenic temperature
Ar scintillation studies and HP-TPCs
New high voltage system for future large LAr detectors
Measurement of the ion feedback from the gas and
the ion velocity in liquid R. Santorelli - IX Jornadas CPAN 27 Topics
1.0 1.0 Counts of A20 Counts of A20 0.9 0.9 T= 298K T= 77K Vop = 44.1V 0.8 Vop = 53.63V 0.8 Fiber Led 260nm Led 260nm 0.7 Gate 500 ns 1kHz 0.7 Gate 500 ns 1kHz
0.6 0.6
0.5 0.5 Counts
0.4 Counts 0.4 SiPM 0.3 0.3 0.2 0.2
0.1 0.1
0.0 0.0 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 Charge (pC) Charge (pC)
R. Santorelli - IX Jornadas CPAN 28 Conclusions
• LAr-EL TPC gives a remarkable and unique opportunity of having large exposures (~100 kgyr) in background free mode
• Our group is firmly committed to the search for DM as part of a world leading Collaboration, as well as to develop, as a major player, related R&D activities on LAr technology
R. Santorelli - IX Jornadas CPAN 29