Recent results from the EDELWEISS-III Dark Matter search
52nd Moriond Conference, 19.03.2017 – 24.03.2017 Very High Energy Phenomena in the Universe
Bernhard Siebenborn
KIT – The Research University in the Helmholtz Association www.kit.edu Direct search for Dark Matter
Ge, CF3I, C3F9 Ge, Si 10% energy Ionization
liquid Xe/Ar Target Heat Al2O3, LiF 100% energy slowest cryogenics
Light 1% energy CaWO4, BGO fastest NaI, liqu.Xe no surface effects
2 Bernhard Siebenborn Direct search for Dark Matter DAMIC CoGeNT, CDMSlite CDEX, Ge, CF3I, C3F9 Ge, Si EDELWEISS, PICO 10% energy SuperCDMS Ionization
DarkSide, DEAP-3600 liquid Xe/Ar Target Heat Al2O3, LiF 100% energy LUX, PandaX-II, slowest CRESST-1 cryogenics XENON100, XENON1T Light 1% energy CaWO4, BGO fastest no surface effects NaI, liqu.Xe CRESST DAMA/LIBRA, DM-Ice, ANAIS, KIMS, SABRE
3 Bernhard Siebenborn Liquid noble gas vs. cryogenic bolometers
EDELWEISS
DAMIC
DAMA/LIBRA CDMSLite2 Cryogenic detectors CRESST(2015) low thresh, high CRESST(2012) energy resolution CDMS-LT
n floor
x 10.000 Liquid noble gas: target mass, low bgd Billard, Strigari, Figueroa-Feliciano PRD 89 (2014)
4 Bernhard Siebenborn EDELWEISS collaboration
CEA Irfu/Iramis (Saclay) CSNSM (Orsay) Institut Néel (Grenoble) IPNL (Lyon) LPN (Marcoussis)
KIT (Karlsruhe)
JINR (Dubna)
University of Oxford
EDELWEISS 2016 @ KIT University of Sheffield
1
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y y
1 1
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sr
2 2 -
Muon intensity, m intensity, Muon 5 m/m2/day 4800 mwe Depth, meters water equivalent (deepest in Europe)
5 Bernhard Siebenborn EDELWEISS-III FID800 detectors
e- WIMP
푈 Q → E WIMP Ion + NTD h
ΔT ~ Eheat = Erecoil + ENTL
Top = 18mK Ø=70mm, h=40mm 2 GeNTDs heat sensors additional heat by drifting charges (Neganov-Trofimov-Luke effect): Electrodes: concentric Al rings
XeF surface treatment: to ensure low leakage 퐸푁푇퐿 = 푁 ∙ 푒 ∙ 푈 2 current (<1 fA) between adjacent electrodes
JLTP(2014)176:182
6 Bernhard Siebenborn EDELWEISS FID800 detectors
Fully InterDigitized ~870g HPGe detectors Challenges: Low event rate: <1 evt/kg/year Ctop=+4V Vtop=-1.5V Small energy deposit: O(keV) NTD Background events by: b, g, n
m - induced background 309 –
e- B 681 (2009) 305 (2009) B681
FID800 Lett
h+ Phys
NTD
Cbott=-4V Vbott=+1.5V Bulk/Fiducial event: Surface event:
Signal on Ctop&Cbott Signal on Cbott&Vbott
7 Bernhard Siebenborn EDELWEISS experimental setup
e+,e-, g, Pb shield
m, Muon Veto Cryostat n, Polyethylene shield
8 Bernhard Siebenborn EDELWEISS DAQ system
FPGA based DAQ system Hardware and software trigger, event based read out Integration of external detectors: Muon-Veto Option to change individual bias voltage 0V±70V
Continuous digitization (100kHz, 16bit), optional: 40MHz, 16bit opticalfiber
detectors analog analog/digital DAQ crate, FPGA ethernet DAQ PCs, software at 18mK amplification at conversion trigger, central clock trigger and event 100K with FET storage detector bias, up to based on Auger and
140V KATRIN crate continuous control
inner shielding cryostat
9 Bernhard Siebenborn
Nuclear recoil calibration - event discrimination
AmBe neutron calibration Clear event-by-event separation electron recoils down to 5 keV energy (nuclear recoils)
Response to nuclear recoils calibrated
Ionization yield Ionization down to the analysis threshold for low-
mass WIMP searches (1 keVee heat = 2.5 keV nuclear rec.)
nuclear recoils
Recoil Energy (keV)
10 Bernhard Siebenborn Event rejection of γ and surface events
g rejection factor: < 5.6 x 10-6 JLTP(2012)167:1056 Updated now to < 2.5 x 10-6 with additional detectors + statistics Surface event rejection (210Pb+210Bi b, 210Po a, 206Pb recoils): < 4 x 10-5 JLTP(2014)176:870 EDELWEISS FID 133Ba calibration (937977 g)
210Pb b 210Po a 206Pb
5 >5000 kg.day 10 kg.day equivalent equivalent
11 Bernhard Siebenborn EDELWEISS-III 2014-2015 science run
161 days of physics data with 24 FIDs: >3000 kgd total exposure
Low ER bkg: 19 FIDs used in first measurement of cosmogenic production of 3H in Ge
arXiv:1607.04560
<0.1dru
8 lowest threshold FIDs used for low-mass
WIMP search
12 Bernhard Siebenborn Low mass WIMP search with likelihood analysis
EPJC(2016)76:548 8 lowest threshold detectors
13 Bernhard Siebenborn Results of the likelihood analysis
EPJC(2016)76:548 FID824 Ionisation
2 m=4GeV/c excluded at 90%CL FID824 Heat
14 Bernhard Siebenborn First results of EDELWEISS-III phase
EDELWEISS III BDT JCAP05 (2016) 019 Improvement by x20 to x150 between 7 and 10 GeV wrt EDELWEISS II EDELWEISS-II DAMA/LIBRA
CoGeNT-2012 Limited by heat-only bkd: CDMSLite2 CoGeNT-2013 identification and rejection using the σ = 230 eV resolution on ionization Ionization resolution is key for rejection Heat resolution is key for low thresholds
EPJC(2016)76:548
15 Bernhard Siebenborn EDELWEISS 2018 goals: 4x100
Challenges: 1. “Heat only” events x100 reduction 2018 goal, 350 kg·d 2. HEMT transistor read out
σion = 200eV 100eV 100 V, actual bgd 3. NTL effect read out
Vbias = 8V 100V 35000 kg·d 4. Improved heat sensors
σheat = 500eV 100eV
JLTP(2015)00376R1
16 Bernhard Siebenborn Challenge 1: Detector R&D: reducing heat only events
Dominant (&reproducible) background at low energy
Noise, cryogenics, stress from detector suspension: excluded as sources of this background Deported NTD Remaining suspect: stress from gluing, avoided via:
Two “deported NTD”, glued on separate sapphire wafer Photo-lithographed high-Ω NbSi TES, sensitive to athermal phonons
NbSi TES
17 Bernhard Siebenborn Challenge 2: Detector R&D: HEMT read out
JFET HEMT Reduced intrinsic noise Lower heat load Operates at 4K stage shorter cabling Reduced capacitance Better SNR JLTP(2016)184:505
Successful HEMT amplifier 241Am calibration Baseline with sub-100 eV resolution RMS 91 eVRMS ionization resolution
A. Phipps et al., arXiv:1611.09712 collaboration between SuperCDMS and EDELWEISS
A. Phipps et al., arXiv: 1611.09712
18 Bernhard Siebenborn Challenge 3: Lower threshold by increased bias voltage Neganov-Trofimov-Luke effect Detector bias upgrade: 푉 = 8V 140V ΔT ~ Eheat = Erecoil + ENTL 푏푖푎푠
ENTL= 푁 ∙ 푒 ∙ 푉푏푖푎푠
Prompt phonons 133Ba calibration V Charge propagation bias NTL amplified 356keV γ-line phonons
Pair creation in Ge: 1 keV 340 e-h+ pairs Sensitivity goal: <100 eV
Ionization signal measured in heat channel No particle discrimination at threshold
19 Bernhard Siebenborn Challenge 3: Lower threshold by increased bias voltage Neganov-Trofimov-Luke effect Detector bias upgrade: 푉 = 8V 140V ΔT ~ Eheat = Erecoil + ENTL 푏푖푎푠
ENTL= 푁 ∙ 푒 ∙ 푉푏푖푎푠
Prompt phonons 133Ba calibration V Charge propagation bias NTL amplified 356keV γ-line phonons
Pair creation in Ge: 1 keV 340 e-h+ pairs Sensitivity goal: <100 eV
Ionization signal measured in heat channel No particle discrimination at threshold Ionization as diagnostic signal at higher energy
20 Bernhard Siebenborn Surface event discrimination by rise time
C1 40MS/s
V2 C1 – C2 ADU
C2
fiducial A. Broniatowski et al. PLB681(2009)305 surface
Rise time as complementary Rise time cut at 450ns surface rejection:
95% „surface“ rejection 4.4% efficiency loss „fiducial“
EDW-III 40MHz digitizer (yet restricted to Eion>100keV)
21 Bernhard Siebenborn Detector R&D and MC studies of charge migration
N. Foerster et al., JLTP(2016)184:845
VB = -VD = 2V
VA = VC = 0V
VB = -VD = 50V
VA = VC = 0V
241Am(g, 60keV) Pb, d=1mm VB = -VD = 2V
VA = VC = 0V
VB = -VD = 50V
VA = VC = 0V
MC
N. Foerster, PhD thesis 2017
22 Bernhard Siebenborn Challenge 4: Detector R&D: Thermal model & heat sensor
J. Billard et al., JLTP(2016)184:299 Better understanding of heat signal Thermal modeling of signal, verified with dedicated R&D Identification of sensitivity to ballistic phonons Identification of parasitic heat capacity
Averaged 1 keV template Best fit 95% C.L. band
Sensitivity of 200 nV/keV (x6 wrt present FIDs) achieved on 250 g test detectors
23 Bernhard Siebenborn EDELWEISS 2018 goal
EDW-III 350 kg.d, EDW-III background assumed
EPJC (2016) 76:548
100V, s=100eV(heat)
8V, s=100eV(ion)
JLTP(2016)184:308
24 Bernhard Siebenborn Conclusion and Outlook
EDELWEISS-III results 2016
100V EDW-III goals 2018
350kg-days
going beyond (35kg x 1000days) 8V no neutron-bgd, 0.1 x Compton
25 Bernhard Siebenborn Conclusion and Outlook
Going beyond: EDELWEISS-III SuperCDMS + results 2016 EDELWEISS at SNOLab
CRESST-3 phase 1
EDW-III goals 2018
CRESST-3 phase 2
35 ton-days
SuperCDMS@SNOLAB
26 Bernhard Siebenborn