LUX & LZ Dark Matter Experiments @ Sanford Lab / DUSELlux.brown.edu/talks/091116_lux_lz_gaitskell.pdf•Robert Svoboda, Mani Tripathi, Richard Lander •UC Santa Barbara •Harry Nelson

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


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)


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


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 / 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


Events

14

9 keVr neutron event


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


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


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


Sanford LabLUX Surface Facility


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


Sanford LabDavis Underground Laboratory


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


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


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-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


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)


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


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)


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


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


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


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


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


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


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

Documents

LUX & LZ Dark Matter Experiments @ Sanford Lab / DUSELlux.brown.edu/talks/091116_lux_lz_gaitskell.pdf•Robert Svoboda, Mani Tripathi, Richard Lander •UC Santa Barbara •Harry Nelson