lux & lz dark matter experiments @ sanford lab /...
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LUX & LZ Dark Matter Experiments
@ Sanford Lab / DUSEL
Rick Gaitskell, Joint Spokesperson, LUX Collaboration
US Spokesperson, LUX ZEPLIN (LZ) CollaborationParticle Astrophysics Group, Brown University, Department of Physics
(Supported by US DOE HEP)see information at
http://luxdarkmatter.org http://particleastro.brown.edu/
Dark Matter, Sept 2007 Rick Gaitskell, Brown University, DOE
DM Direct Search Progress Over Time (2009)
~1 event kg-1 day-1
~1 event 1 tonne-1 yr-1
2
(Gross Masses kg)
ZEPLIN III.1
ZEPLIN III.2
LZ-S 1500kg
LZ 20t
CDMS Soudan 2008
LUX 350kg
XENON 100kgSuperCDMS
25 kgXMASS 800kgWARP 140kg
SuperCDMS 125 kgXENON 1000kg
σ=10-48
CDMS Soudan 2009
LUX Collaboration, 2009 Gaitskell <>
Evolution
From XENON10/ZEPLIN to LUX Self shielding much improved Fiducial Region
• 5 kg -> 100 kg Overall Increase sensitivity by ~100x
XENON1022 kg / Fiducial 5.4 kg
LUX350 kg / Fiducial 100 kg
LUX Collaboration, 2009 Gaitskell <>
Experiment vs Project
LUX allows us to directly test many of the critical technologies for large Xe detectorsThe methods used are “industrial” scaleNecessary for multi-tonne scale aimed DUSEL
We are aiming to reduce PROJECT RISKSNot looking to introduce fundamentally new tech.Necessary evil - caused by large scale/$ deploymentCounter cultural
LUX Experiment / Rick Gaitskell / Brown University 5
The LUX CollaborationCollaboration meeting, Homestake, March 2009Xenon10, CDMS
SNO, Borexino, Xenon10, CDMS
Xenon10, CLEAN-DEAP
SNO, KamLAND
Xenon10
EXO
Zeplin II
Double Chooz, CDF
Zeplin II
Formed in 2007, fully funded DOE/NSF in 2008
Majorana, CLEAN-DEAP
Harvard (June 2009)Masahiro Morii
Bob Jacobsen Professor
South Dakota School of Mines and Technology (August 2009)Xinhua BaiMark Hanardt
Gaitskell - Brown University / LUX 6
LUX Detector - OverviewLUX Detector
Liquid Xenon TPC• Primary scintillation signal• Secondary proportional electroluminescence
signal from drifted ionisation electrons intothe gas phase
Single phe sensitivity 3D imaging with cm precision
350 kg of Xe• 300 kg active, 100 kg fiducial
2 arrays of 61 PMTs
LUX 0.1 has permitted to demonstrate many subsystems for the past 12 monthsOperations at Case Western
From October 2009 onward next 6 months, program = full LUX assemblyAt Texas A&M since early 2009Now Reassembling at Sanford Lab (South Dakota)
Gaitskell - Brown University / LUX 7
LUX Detector - Overview
Titanium Vessels
Dodecagonal field cage+ PTFE reflector panels
PMT holding copper plates
Counterweight
Feed-throughs for cables / pipesLN bath column
Radiation shield
49 cm59 cm
Cathode grid
Anode grid
Gaitskell - Brown University / LUX
WIMP Sensitivity
8
In < 2 live days we will surpass sensitivity of all existing results for dark matter direct detection experiments
Focus on discovery ... if dark matter cross section is factor 10 below current best 90% CL search limits ...
LUX Experiment / Rick Gaitskell / Brown University
LUX 350 kg / 100 kg Fiducial 100 days / WIMP Discovery
9
Simulated LUX data(100 kg fiducial, 100 days)
mX = 100 GeV/c2
σ = 5 10-45 cm2
Red - Example of WIMP Signal if cross-section is 1/10th of current best limits (90% CL)
Blue - All ER background events in fiducial region after 100 live-days
Gaitskell - Brown University / LUX 10
LUX Detector - Internals
122 2" PMT R8778 175 nm, QE > ~30%U/Th ~9/3 mBq/PMTAll tested in LUX 0.1 program
Dodecagonal field cage+ PTFE reflector panels
Copper PMT holding plate
HV Grids in place and tested
Assembly taking place at Texas A&M since early 2009
Gaitskell - Brown University / LUX 11
Gaitskell - Brown University / LUX 12
Gaitskell / LUX Collaboration
LUX0.1 Overview
13
LN
LUX0.1Al filler
LXe can
Vac. can
Cold Head
Gas Lines
Detector
Nitrogen GasLines
Thermosyphon
Cryostat
• Surface run at Case Western Reserve University• Full assembly of LUX subsystems:
‣ Cryogenics‣ Recirculation‣ Slow control & safety systems‣ Electronics chain‣ PMT mounts and resistor-chain bases‣ Analysis software
• 60 kg Xe total mass (260 kg Aluminum filler displacer)• 4 PMT operation, 5 cm active Xe region
5 0 5 10 15 20 25 30 35 40 45 5010
0
10
20
30
40
50
60
µs
mV
LUX 0.1 Run009 POD Mode Event
S1 = 14.3pheS2 = 4088phe
Baseline
ch 1ch 2ch 3ch 4
Gaitskell / LUX Collaboration
Events
14
9 keVr neutron event
Gaitskell / LUX Collaboration
83mKr Based Calibration
15
McKinsey talk
0 20 40 60 80 100 120
10
10
100
Recirculation Time [hours]
Elec
tron
Drif
t Len
gth
[m]
Purification vs. Time, Run009
2 error bars1 error bars
Gaitskell / LUX Collaboration
Xenon Purity
16
• ~9 hr time constant for purification
• > 2 m electron drift length achieved(> 1000 us) with 60kg target
•Errors dominated by use of 5 cm test cell drift within large cryostat
0.2 tonnes circulation per day
Gaitskell / LUX Collaboration
Heat Exchanger Operates >96% Efficient
17
Demonstrated - 18 W required to circulate 0.4 tonnes of Xe a dayEvaporate Liquid > Gas / Purification -> Re-condense Liquid
Gaitskell - Brown University / LUX 18
Sanford LabLUX Surface Facility
Gaitskell - Brown University / LUX 19
Sanford Lab – LUX Surface Facility
Full-scale test of LUXassembly and deployment 350 kg Xe 122 PMTs Titanium cryostat Full DAQ system
Refurb supported entirely by SDSTA funds
Exact duplicate of the underground layout for all major systems Smaller d=3m water tank, permits data taking with manageable background (Brown MC) CL 1k clean room, will be relocated underground
Summary schedule (2009): Jul 8: Began demolition / clean-up Jul 14: Began new construction End Oct: Full beneficial occupancyNov 1: Start full detector assembly programJan: Detector operation with full payload See larger version next slide
Gaitskell - Brown University / LUX 20
Sanford LabDavis Underground Laboratory
LUX Experiment / Rick Gaitskell / Brown University 21
LUX 1.0 – Davis Laboratory (4850L)Construction/excavation design completed
New 300’ access/safety tunnel to be excavatedShared access with Majorana facility, also to be excavated
Two storey, dedicated LUX 55’ x 30’ x 32’ facility, CL 100kIncludes CL 1k clean room, control room, counting facility
1964
Beneficial occupancy: May 2010
Rendering by J. Thomson
Lab
Mine shaft
Majorana
LUX
Mechanical& Electrical Services
200 m
Gaitskell - Brown University / LUX 22
Sanford Lab – Davis Laboratory Layout (Side View)
Rendering by J. Thomson
Control Room Clean Room
Water Tank CountingFacility
Access
Tunnel
LUX Experiment / Rick Gaitskell / Brown University
1964 / 2009 “They want to fill the cavern with what ?*?”
23
1964
Gaitskell - Brown University / LUX 24
Sanford Lab – State of the Davis CavernAug 24: Equipment commissioning completeAug 31: Began excavation of new driftSep 10: Steel structures removal completeNov 15: Detailed Outfitting docs 100% completeJan 20: Excavation completeMar 25: Rock support & wall finish completeMar 30: Begin Lab outfittingMay 05: Davis cavern ready
Davis CavernMay 22, 2009
Davis CavernSep 01, 2009
Davis CavernAug 24, 2009
Davis CavernAug 20, 2009
now
Level 4850Aug 25, 2009
Dark Matter, Sept 2007 Rick Gaitskell, Brown University, DOE
DM Direct Search Progress Over Time (2009)
~1 event kg-1 day-1
~1 event 1 tonne-1 yr-1
25
(Gross Masses kg)
ZEPLIN III.1
ZEPLIN III.2
LZ-S 1500kg
LZ 20t
CDMS Soudan 2008
LUX 350kg
XENON 100kgSuperCDMS
25 kgXMASS 800kgWARP 140kg
SuperCDMS 125 kgXENON 1000kg
σ=10-48
CDMS Soudan 2009
LUX Dark Matter Rick Gaitskell, Brown University, DOE
The LZ program
• LZ: LUX + ZEPLIN III + new US and European groups• LZS (Sanford): 1.5 ton instrument for Sanford Lab, just proposed.• LZD (DUSEL): Scale based on technically feasibility, cost.
26
20-tons
2 m0.85 m0.5 m
LZS 1.5 tons
LZD
4 x LUX scale
LUX 300 kg@ Sanford Lab.
LUX Dark Matter Rick Gaitskell, Brown University, DOE
LUX-ZEPLIN Collaboration for LZ-Sanford and LZ-DUSEL•Brown University
•Richard Gaitskell•Caltech
•Bob McKeown•Case Western Reserve University
•Thomas Shutt, Dan Akerib,Mike Dragowksi•Harvard
•Masahiro Morii•Imperial College, London
•Tim Sumner, Henrique Araujo•ITEP, Moscow
•Dmitri Akimov•Lawrence Berkeley National Laboratory
•Bob Jacobsen, Henrik von der Lippe. Jim Siegrist•Lawrence Livermore National Laboratory
•Adam Bernstein•LIP, Coimbra
•Isabel Lopes•Moscow State Engineering Physics Institute
•Alex Bolozdynya•South Dakota School of Mines & Tech
•Xinhau Bai•STFC Rutherford Appleton Laboratory
•Pawel Majewski•STFC Daresbury Laboratory
•John Simpson•Texas A&M
•James White•UC Berkeley
•Bob Jacobsen•UC Davis
•Robert Svoboda, Mani Tripathi, Richard Lander•UC Santa Barbara
•Harry Nelson•University of Edinburgh
•Alex Murphy•University of Maryland
•Carter Hall •University of Rochester
•Frank Wolfs•University of South Dakota
•Dongming Mei
International collaboration, with expertise in dark matter search, noble gas techniques, water detectors, high energy physics and large scale deployments (under/above grounds).
Includes PIs/Senior Researchers fromEXO, XENON10, LUX, ZEPLIN II, III, CDMS I, II, SNO, SuperK, Kamland, Borexino, IMB.
27
LUX Collaboration, 2009 Gaitskell <>
KEY ISSUES
Focus on a few key issues that are being highlighted in Q&A
de Viveiros - Brown University November 2009 v04 <>
Larger Detectors – Gamma BackgroundsEvolution of fiducial volume: more mass → more self-shielding
Larger total mass leads to larger fraction available for fiducial volume
PMT radioactivity reduction subdominant for large detectors PMT radioactivity (per area) is important for ≤ 1T detectors
• x1/10 reduction in PMT activity in LUX => x2.5 increase in fiducial volume Improvement due to reduction of PMT radioactivity (per area) is subdominant for larger detectors (≥10T)
• x1/10 reduction in PMT activity in 20T => 10% increase in fiducial volume
Gamma backgrounds
LUX (350 kg)= 33% fiducial
volume
20T>70% fiducial
volumeLUX350 kg
3T10T 20T
Maximum fiducial fraction for0.7 events in 300 days (same as LUX)
LUX Dark Matter Rick Gaitskell, Brown University, DOE
PMT Evolution
30
LED Calibrationgain = 4.5 106
σ/µ = 35%
•PMTs for LUX 350 120 x 2” Hamamatsu R8778 U/Th 9/3 mBq/PMT QE 35%
•Baseline PMTs for LZ-S and LZ-D DUSEL R&D for 3” PMTs for LXe Hamamatsu R11065mod development 3" PMTs. LZ have tested photo-performance/sensitivity/LXe operation -
same as R8778 Factor 2 improvement in bg for standard PMT Goal through further materials selection ~1/1 mBq/PMT XMASS/Suzuki (2008) achieved 2” R8778mod <0.7/<1.0 mBq/
PMT
R8778
R11065
LUX Dark Matter Rick Gaitskell, Brown University, DOE
Light collection at large scales
•PTFE walls: extraordinarily reflective at 175 nm (7eV) Should be verified independently.
•Rayleigh scattering not yet dominant Light collection independent of size (with low absorption) well past 100 tons.
•We predict > 70% light collection with top/bottom PMT coverage.•Absorption: Need ~0.1 ppb of common gasses, comparable to requirements for charge
drift
31
0.1 ppb: 1 km => <2% loss
LXe
Gaitskell / Fiorucci - Brown University November 2009 v01 <>
Titanium for Vessel - Low Radioactivity
Conventional U/Th/K activities are low - dependent on Grade of Ti (90% upper limits) U < 0.25 mBq/kg Th < 0.2 mBq/kg K < 1.3 mBq/kg
Cosmogenic: 46Ti (n,p) 46Sc Half Life 84 d Two γ at ~1 MeV Same “danger” as 60Co
Results from simulation (ACTIVIA): Expect 1.65 +/- 0.45 mBq/kg after 150 days at Sanford Surface altitude + Similar contribution from slow-going muon capture on Ti (not in MC)
Counted Samples Average: ~4.8 mBq/kg Corresponds to ~15% of LUX ER budget (5% after 130 days underground)
Gaitskell / Fiorucci - Brown University November 2009 v01 <>
Activities Intrinsic to Xenon - Cosmogenics
Activation by muon-induced neutrons underground (4.3 km.w.e) Of particular interest: “naked β” emitters inside Xe volume
Results from Simulation (ACTIVIA): Three main naked β emitters produced:
• 126I (λ = 13 d) 0.2 β event in [0 – 20 keVee] /1 tonne Xe /1000 days• 129mTe (λ = 33 d) 0.05 β event in [0 – 20 keVee] /1 tonne Xe /1000 days• 3H (λ = 4503 d) ~60 β events in [0 – 20 keVee] /1 tonne Xe /1000 days
Rates before ER discrimination (> 99.5%)
Effect of Purification System: LUX 350kg: entire volume circulated every ~24 h I, Te, 3H all very efficiently eliminated, before they have a chance to decay in the active Xe volume (especially 3H)
Event Rates not dangerous even at 20 tonne scale
Gaitskell / Fiorucci - Brown University November 2009 v01 <>
Radon
Measurements at Sanford Surface Lab: ~5 Bq/m3 (window) to 40 Bq/m3 (first floor, no ventilation) Ventilation system ensures 5 Bq/m3 level in entire lab space
Measurements underground Davis Cavern without ventilation: 350 – 600 Bq/m3 range Studies of
Detector assembly will take place at the Surface Facility clean roomDavis Water Tank is an efficient Rn shield
Contribution of external Rn to detector background negligible Air-tight cowling and feed-throughs isolate water + detector from lab atmosphere N2 gas purge system above water level N2 stripping in the water purification system Stable thermal gradient in the tank prevents Rn from diffusing from the edges
Gaitskell / Fiorucci - Brown University November 2009 v01 <>
85Kr
Existing chromatographic (charcoal) system developed for XENON10 (2006) by Shutt/Case Western achieved < 3 ppt 85Kr Compare with 140 ppt for distillation system
36
CWRU chromatographic system removing Kr from Xe
120 cycles 26 kg Xe for XENON10<3 ppt (10-12) Kr
<6·10-23 85Kr
200626 kg
2010350 kg
Bolozdynya, Brusov, Shutt, Dahl, Kwong NIM A 579 (2007) 50
LUX Dark Matter Rick Gaitskell, Brown University, DOE
Xe Procurement
•Xe procurement. World production ~45 tons/year
•Xe price typically in range ~$0.5-0.7M/tonne over last 30 years 3 episodes where price spiked - typically takes 18-24 months for price to recover to normal
range
•Recent spike >$5M/tonne in 2007/8. Factors causing: 14 tonnes of Xe acquired in a single purchasing campaign by two industrial manufacturers -
associated with a new 45 nm Si chip fab process. Since re-tasked using different gas. Perception of tight market lead to longer term contracts being established Speculation
•Pricing has returned to more usual values now Reasonable to expect acquisition programs to achieve <~$1M/tonne
37
LUX Experiment / Rick Gaitskell / Brown University 38
LZ Program – LZ20, ultimate search?Electron Recoil signal limited by p-p solar neutrinos
Subdominant with current background rejection
Nuclear Recoil background: coherent neutrino scattering 8B solar neutrinosAtmospheric neutrinosDiffuse cosmic supernova background
LZ20 reaches this fundamental limit for direct WIMP searches
Electron Recoils
LZ20 also sensitive to ββ0ν decay in natural xenon up to lifetimes of ~1.3 1026 years !
L. Strigariastro-ph/0903.3630
Nuclear Recoils
LUX Dark Matter Rick Gaitskell, Brown University, DOE
Challenges toward 20 tonne•Purity: Charge and light collection
• Ensure that scale of purification system well matched to target size
•Enhanced radiopurity requirements, Rn, Kr. mBq requirements in Xe target compare to µBq goals in targets achieved for neutrino
experiments (SNO, Borexino).
•Active scintillator outer shield Goal - 90% neutron, 90-99% gamma tag: increase fiducial mass to ~90%, reduces potential
systematics.
•High voltage Cathode: <=250 kV feed through Baseline: Xe e drift works well at 0.5 kV/cm (x 2 m drift for 20 tonne) Continue to investigate improvements associated with higher drift fields / ZEP III
•Mechanics / safety associated with large liquid noble targets •Application of proven principles, but need development for 20 tonne scale. Need high level of assurance for positive dark matter detection
•Xe procurement. World production ~45 tons/year
39
LUX Experiment / Rick Gaitskell / Brown University 40
Projections based onKnown background levels Previously obtained e- attenuation
lengths and discrimination factors
Fiducial volumes selected to match < 1 NR event in full exposure
LZ Program - WIMP Sensitivity
LUX (constr: 2008-2009, ops: 2010-2011) 100 kg x 300 days
LZ3 (constr: 2010-2011, ops: 2012-2013) 1,500 kg x 500 days
LZ20 (constr: 2013-2015, ops: 2016-2019) 13,500 kg x 1,000 days
10 events sensitivity
1 event sensitivity
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