XENON Dark Matter Experiment (NSF/DOE) - Brown …gaitskell.brown.edu/physics/talks/0602_Homestake_DUSEL/0602_XEN… · XENON Dark Matter Experiment (NSF/DOE) Rick Gaitskell ... only

Gaitskell

XENON

Dark Matter Experiment

(NSF/DOE)

Rick GaitskellParticle Astrophysics Group, Brown University, Department of Physics

(Supported by US DOE HEP)

see XENON information at http://www.astro.columbia.edu/~lxe/XENON/

http://xenon.brown.edu/ v10

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The XENON Collaboration

Columbia University Elena Aprile (Spokesperson), Karl-Ludwig Giboni, Sharmila Kamat,

Kaixuan Ni, Masaki Yamashita, Marie-ElenaBrown University

Richard Gaitskell, Simon Fiorucci, Peter Sorensen, Luiz DeViveirosUniversity of Florida

Laura Baudis, Jesse Angle, David Day, Joerg Orboeck, Aaron Manalaysay Lawrence Livermore National Laboratory

Adam Bernstein, Chris Hagmann Celeste WinantCase Western Reserve University

Tom Shutt, John Kwong, Alexander Bolozdynya, Eric Dahl Paul BrusovRice University

Uwe Oberlack, Peter Shagin, Roman Gomez Yale University

Daniel McKinsey, Richard Hasty, Angel ManzurGran Sasso National Laboratory, Italy

Francesco Arneodo and Alfredo Ferella University of Coimbra, Portugal

Jose A.M. Lopes and Joaquim Santos

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XENON10 - Homestake - 9 February 2006 Rick Gaitskell, Brown University, DOE

XENON - 10 kg

XENON - 100 kg

XENON - 1T

CDMS IIZEPLIN I

EDELWEISS

DAMA

Dark Matter Goals• XENON10 - Sensitivity curve corresponds to

~2 dm evts/10 kg/month Equivalent CDMSII Goal for mass >100 GeV

(Latest 2005 CDMSII result is x10 above this level)

With only 30 live-days x 10 kg fiducial - Zero events - would reach XENON10 sensitivity goal (90% CL), but we would like to do physics!

Important goal of XENON10 prototype underground is to establish clear performance of systems

• XENON100 - Sensitivity curve corresponds to ~2 dm evts/100 kg/month

Background Simulations for XENON10 indicate it could reach b/g suppression necessary to reach this sensitivity limit, but with 10 kg target would only give ~2 dm evts/10kg/year - no physics.

• XENON1T 10-46 cm2 ~1 dm evts/1 tonne/month

• NOTE THAT GOAL IS TO DO PHYSICS ON WIMP (rates/month), NOT SIMPLY SET A DETECTION LIMIT

SUSY TheoryModels

Dark Matter Data Plotterhttp://dmtools.brown.edu

CDMS II goal

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http://dmtools.brown.edu

http://dmtools.brown.edu

Known Unknown - Direct Detection - Nov 2005 Rick Gaitskell, Brown University

DM Direct Search Progress Over Time (2006)

Based on Review Article: Gaitskell, Ann. Rev. Nucl. and Part. Sci. 54 (2004) 315-359

~1 event kg-1 day-1

~1 event 100 kg-1 yr-1

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Known Unknown - Direct Detection - Nov 2005 Rick Gaitskell, Brown University

Signature of Signal vs Background

Detectors must effectively discriminate between

Nuclear Recoils (Neutrons, WIMPs)

Electron Recoils (gammas, betas)

Much of dark matter detector effort is being focused on techniques that can discriminate between these two types of backgrounds

Attisha (Brown)

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Gaitskell

XENON Event Discrimination: Electron or Nuclear Recoil?

EGC

Cathode

Grid

AnodeEAG

EAG > EGC

Liquid phase

Gas phase

Within the xenon target:

• Neutrons, WIMPs => Slow nuclear recoils => strong columnar recombination

=> Primary Scintillation (S1) preserved, but Ionization (S2) strongly suppressed

• γ, e-, µ, (etc) => Fast electron recoils =>

=> Weaker S1, Stronger S2

PMT Array(not all tubes shown)

Ionization signal from nuclear recoil too small to be directly detected => extract charges from liquid to gas and detect much larger proportional scintillation signal => dual phase

Simultaneously detect (array of UV PMTs) primary (S1) and proportional (S2) light => Distinctly different S2 / S1 ratio for e / n recoils provide basis for event-by-event discrimination.

Challenge: ultra pure liquid and high drift field to preserve small electron signal (~20 electrons) ; efficient extraction into gas; efficient detection of small primary light signal (~ 200 photons) associated with 16 keVr

Light SignalUV ~175 nmphotons

Time

Primary

Proportional

Interaction (WIMP or Electron)

Liq. Surface

e-e-

e-e-

e-e-

e-e-

e-e-

e-e-

Electron Drift~2 mm/µs

0–150 µsdepending on

depth

~40 ns width

~1 µs width

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New Highlights

• Nuclear Recoil Scintillation (Primary Light) Efficiency Determined Low energy recoil calibration 10-50 keVr (QF 12-20% rel to zero field keVee signal) (~6-10 primary photons per keVr) Aprile at al., Phys. Rev. D 72 (2005) 072006

• Nuclear Recoil Ionization Efficiency Determined Electron signal from NR higher than expected 20-100 keVr ~3-5 electron in liquid per keVr (~250 secondary photons per liquid electron extracted into gas) Aprile et al., PRL, astro-ph/0601552

• XENON3 (6 kg target) LXe (40 PMT) - Test systems for “10” Full checkout of cryogenics, HV, DAQ systems Fall 2005 Operated with PMT arrays located above and below LXe

• Position reconstruction/Discrimination verified

• Verified photoelectron/keVee & /keVr numbers— Using γ sources and neutron scattering at defined angles

• XENON10 (14 kg target) LXe (90 PMT) - Underground Deployment Dec/Jan - Upgraded chamber to full complement of PMTs at Nevis Labs (Columbia) Currently performance testing prior to shipping to LNGS this month

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10.4 keV nuclear recoils

Lindhard

Hitachi

Nuclear Recoil Scintillation Efficiency

• Time of (ToF) and PSD used to resolve neutron/gamma

• Scintillation efficiency at low nuclear recoil energy was measured, which supports a bi-excitonic collision model

• At higher energy recoils, our results are consistent with most of the other results

Aprile et al., Phys. Rev. D 72 (2005) 072006

BoratedPolyethylene

Pb

Columbia RARAFp(t,3He)n2.4 MeV neutrons

LXe

L=20 cm

BC501A

BC501A

[Columbia/Yale]

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Columbia/Brown

Case Western

Gamma Events 1 kg LXe Tests Nuclear Recoil

Columbia/Brown

Case Western

Aprile et al., PRL, astro-ph/0601552

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Event Discrimination

• Nuclear Recoil Discrimination Non gaussian tails due to edge effects which can be eliminated with multiPMT xy cuts Data taken with 2 kV/cm drift field

Aprile et al., PRL, astro-ph/0601552

nucl

ear

reco

ils

elec

tron

reco

ils

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Drift 10 cm (50μs)

• background events mostly happen near the edge (maximum r) and surface (top/bottom) → efficiently reduce them by fiducial volume cut

• electric field lines near the edge are not uniform and straight → those events mimic nuclear recoils and have to be removed

• WIMPs do not multiply scatter. (Multiple scattering of neutrons can be used as tag on background)

Hamamatsu R8520 PMT:Compact metal channel: 2.5 cm square x 3.5 cmLow background: 3 mBq U-238/Th-232Quantum Efficiency: >20% @ 178 nm

XENON3 3D position sensitive dual phase detector

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XENON3 Event

• XENON3 Event 100 keV nucl recoil evt Σ Top PMTs: Blue trace (gas)

Σ Bottom PMTs: Red trace (liq)

• First Signal, S1 Primary Scintillation S1 phe ~50 ns wide Bottom PMTs see most phe

(Top suffer loss at liq. surf.)

• Second Signal, S2 Electron Drift liq. ~30 µs

-> extract into gas-> Electroluminescence“z” position

S2 phe ~1.5 us wide See “Hot Spot” position

“x-y” position

[Luiz de Viveiros, Brown]

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XENON3 Neutron Scattering at Fixed Angles

LXe

BC501A

BC501A

XENON Collaboration

d(d,3He)n

22 keVr

55 keVr


• Direct Calibration of Nuclear Recoils Er = 22 and 55 keVr 0.75 phe/keVr

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XENON3 Position Reconstruction

edge events well reconstructed

vacuum cryostatLXe

PTFE

chamber

Co-57

Preliminary Algorithms already achieving <1 cm position resolution.Simulations suggest σxy~2 mm should be possible at 20 keVr.

Z→

direct light collection is not uniform

along Z

a small fraction of charges lost

Lifetime 280 +/- 53 μs[Kaixuan Ni, Columbia]

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• XENON10 now running above ground at Nevis Columbia Lab Testing prior to shipping to LNGS 48 PMTs on top, 41 on bottom, 20 cm diameter, 15 cm drift length, 14 kg LXe

XENON10 detector 14 kg LXe

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XENON10 R&D Milestones: Summary

+ PMTs operation in LXe+ > 1 meter λe in LXe+ Operating ~1 kV/cm electric field+ Electron extraction to gas phase+ Efficient & Reliable Cryogenic System+ Nuclear recoil Scintillation Efficiency (10-55 keVr) + Nuclear recoil Ionization Efficiency + Electron/Nuclear recoil discrimination+ Kr removal for XENON10+ Electric Field / Light Collection Simulations+ Background Simulations + Materials Screening for XENON10+ Assembly of XENON10 System+ Low Activity PMTs and Alternatives Readouts

AchievedAchievedAchievedAchievedAchievedAchievedAchievedAchieved

1 kg purification achievedTools Developed_Done for XENON10

Tools Developed_Done for XENON10All major components screened

AchievedVerified Hamamatsu #’s

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XENON10 at LNGS: Gran Sasso National Laboratory

XENON10

Main Halls ~100 m long x 15 m high

XENON10 Shield: Updated Specifications & Action Items

15 November 2005

Action Items

(1) Full Engineering Drawing of XENON10 Shield, pursuant to this doc. (LNGS Engineering)(2) Specification of requisite Steel Plate thickness (ceiling) (LNGS Engineering)(3) Location of the XENON10 Shield in the box (included, section IV below)(4a) Specification of necessary structural penetrations (LNGS Engineering)(4b) Instrumentation feed-through spec. necessary machining (XENON Collaboration)

Specifications

This brief note summarizes the requirements for construction of the XENON10 shield, with new dimensions as agreed at the 051109 XENON Executive meeting.

Figure 1 below is drawn to scale. The outer I-beam structure is not included. The slide-out section is outlined in red; Pb sub-structure is shown only at the junction, except for the inner 50 mm Pb plates on the ceiling.

Figure 1. Side View Schematic of XENON10 Shield

I. Structure

We would like to minimize the number of bolts which penetrate to the inside of the shield; at the same time, we would like to have the flexibility to remove some Poly, should a re-configuration of the inner shield be necessary. The proposed solution is to have 50 mm thick sheets of Poly (structural) pressed and bolted against the Pb (fig. 1), and 150 mm bricks of Poly (non-structural) stacked inside, to give a total thickness of 200 mm Poly. Adequately supporting the Poly bricks would be easier due to the substantially lower mass, whereas the lateral support of the Pb is provided by (the sandwich of) the Polyethylene plates on the inside, and steel plates on the outside.

II. Slide-Out

For the slide-out L-shaped sliding section, the Pb will step toward the center (i.e. like stairs) along all 6 interfaces that comprise the join (marked in red above). This will allow for easier mating of the sections, viv-a-vis reduced sensitivity to the brick dimensional tolerance, while reducing the

Ex-LUNA Building 5 x 7 m (h 4 m) Detector+ 2.5 x 8 m Box Assembly Space+ 2.5 x 6 m Box Analysis

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XENON10 “Intrinsic” Backgrounds (Monte Carlos)

Stainless from inner + outer vessel + PMT0.11 dru in 10.3 kg fiducial LXe 0-50 keVee (17.3 kg gross volume)

[Joerg Oberlach, U. FLORIDA]

Effect of Position Cuts on Upper (gas) PMT BackgroundsEvent Rates 10-50 keVeeHamamatsu R8520 <3 mBq/PMT


dru == /keV/kg/day

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Review of XENON Thesis Research April 2005 D SILVERMAN

DM Mass From Direct DetectionWIMP Mass Spectroscopy

10 events above threshold 1000 events above threshold

• Comparisons above assume same # of events in each experiment, (not constant cross section). Also we assume WIMP velocity v0=230 km/s.

• At all masses, more events -> Better sensitivity to MD

Undergraduate Senior Thesis, Brown

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Homestake for Dark Matter Experiments

• Depth is critical, because of muon generating high energy neutrons that are able to punch-through conventional shielding.

D.M. Mei and A. Hime, (astro-ph/0512125)

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Homestake Water Shield (see T Shutt Talk)

• MRI Proposal submitted (Jan 06) for high purity water shield (16m x 11m x h10 m) capable of housing multiple dark matter and other low background experiments at Homestake Achieves γ backgrounds of better than 0.01 /keVee/kg/day at low energies (thickness > 3 m) Crucially combination of depth of Homestake 4850 ft and water will ensure that background due to high energy

punch-through neutrons is reduced well below levels required for 1 tonne dm experiments to measure WIMP spectra (σ<~10-46 cm2)

• Very cost effective way of achieving shield for multiple LXe modules to achieve 1 tonne fiducial (XENON1T)

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Proposed Homestake Water Shield

(Side) (Top)

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Homestake Water Shield (see T Shutt Talk)

• MRI Proposal submitted (Jan 06) for high purity water shield (16m x 11m x h10 m) capable of housing multiple dark matter and other low background experiments at Homestake Achieves γ backgrounds of better than 0.01 /keVee/kg/day at low energies (thickness > 3 m) Crucially combination of depth of Homestake 4850 ft and water will ensure that background due to high energy

punch-through neutrons is reduced well below levels required for 1 tonne dm experiments to measure WIMP spectra (σ<~10-46 cm2)

• Very cost effective way of achieving shield for multiple LXe modules to achieve 1 tonne fiducial (XENON1T)

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Homestake Water Shield - Davis Solar Neutrino Cavity

(Side) (Top)Ray Davis taking a dip

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Conclusion

• XENON10 Basic Xenon detector physics now fully characterized XENON10 now being operated at Columbia Labs -> LNGS this month To exceed current best dm sensitivity will require <1 week running

• Goal is for factor 10 improvement over current sensitivity• 3D Event reconstruction will be crucial to assist characterizing backgrounds

• XENON LOI (Elena Aprile) XENON1T will require multiple module deployment

• Homestake Water Shield (Tom Shutt) There is an opportunity to establish a multi-user low background facility

• Provide a strong incentive for locating at Homestake • Very cost effective way of providing ultra low bg environment

Radioactive backgrounds low enough to satisfy dm experiments for at least next 5 years (1 tonne scale)

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XENON1T Multi-module Requirements• The total volume for the 1000 kg of fiducial LXe is relatively modest at ~0.35 m3. The space requirements will be

dominated by the low background shielding required to reduce the external gamma and neutron fluxes incident on the fiducial detector volumes. With current detector designs a single 100 kg detector would be enclosed by a 2.5 m x 2.5 m x 2.5 m shield (external dimensions) constructed of Pb and Polyethylene. (Additional LXe adjacent to the fiducial region, and plastic scintillator surrounding the passive shielding are also

employed for background rejection, acting as anti-coincidence vetoes.) The building for housing a single 100 kg detector and shield would be 6 m x 6 m x 7 m. One way of achieving a

1000 kg fiducial mass would be to replicate 100 kg detector modules within a single shielded volume. The total footprint of a Pb/Poly shield would be ~10 m x 8 m x 3 m height. The building (which would permit

environment control ~ class 2000-5000) in which a shield that could accommodate 10x100 kg modules would be housed would be ~14 m x 12 m x 7 m height. A crane of ~5 tonnes rating would be required to manipulate the shield components.

An alternative is the use of a water shield (instead of Pb/Poly). This could be constructed at lower cost than the conventional Pb/Poly shield, - MRI Proposal Submitted. In this case, cavern of the order of 12 m linear, with a depth of 10 m would be required to house up to 10 detectors.

• Additional staging areas below ground would be required for detector assembly, servicing, and xenon gas recirculation (purification and krypton removal). Also huts for electronics, cryogenics and analysis huts. This would require an addition 150 m2 of space.

• Backup systems would be in place to ensure that the LXe (-100 degC) could be recovered and kept in liquid form, in the event of a power outage. However, a full safety analysis would be necessary focusing on the possibility of a significant fraction of Xe liquid being released into the caverns. 100 kg of liquid Xe corresponds to ~20 m3 of heavier-than-air gas.

• Timescale: The existing XENON10 detector is expected to be operated through 2006 and possibly part of 2007. Funding proposals for future XENON experiments would be expected to be submitted before Sept. 2006, and so construction could begin in 2007, with operation expected in 2008.

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Documents

XENON Dark Matter Experiment (NSF/DOE) - Brown …gaitskell.brown.edu/physics/talks/0602_Homestake_DUSEL/0602_XEN… · XENON Dark Matter Experiment (NSF/DOE) Rick Gaitskell ... only