XENON1T: a ton scale Dark Matter Experiment

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Elena Aprile on behalf of the XENON collaboration

UCLA Dark Matter 2010, February 26, 2010

The XENON Dark Matter Project Roadmap

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XENON10Achieved (2007) σSI=8.8 x10-44 cm2

XENON100 Projected (2010) σSI~2x10-45 cm2

past(2005 - 2007)

current (2008-2010)

future(2011- 2015)

XENON1TGoal: σSI <10-46 cm2

Spin-Independent Projected Sensitivity

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Spin-Dependent Projected Sensitivity

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Constraints on WIMP Mass

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10-45 cm210-44 cm2

• XENON100 is working very well. It is the largest mass and lowest background DM experiment accumulating statistics. The fiducialization allowed by the 3D TPC, the active LXe veto and the S2/S1 discrimination allow for a background free target of many tens of Kg mass.

• Within 2010 XENON100 will a) either see a signal or b) will significantly constraint WIMP models for both SI and SD cross-section compared to current situation. Continued improvement in sensitivity with several targets will be essential for the field.

• Based on our understanding and progress achieved with critical technologies a Xe two-phase detector at the ton scale is feasible and can be realized within a few years. The risks and the costs are fully understood.

• With a strong international collaboration, with continued support from the National Science Foundation, with 50 - 50 share of resources between US and foreign groups, the goal is an experiment working before the middle of 2010.

• Three key factors have accelerated our roadmap towards XENON1T: 1) cost of Xe material; 2) QUPID development; 3) foreign collaborators with guaranteed funding.

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The case for XENON1T

• XENON1T is in line with PASAG recommendation of a vigorous pre-DUSEL program of G2 experiments to push technologies while achieving great science

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XENON1T Cryostat and Detector

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• Design follows closely the approach tested with XENON10 and XENON100, with improvements in several areas:

• Cryostat and Detector Vessels: Lower radioactivity

• PMTs & Cabling: Lower radioactivity QUPIDs ( see Arisakas’ talk)

• Cryogenics: Cryocooler with Heat Exchanger ( see next slide )

• Xe storage and filling: Liquid Phase (MEG experience)

• Efficient background reduction based on:

• 3D event imaging of a TPC

• self-shielding of the dense LXe

• Charge & Light discrimination

• Technical proposal in preparation with full costing and risk assessment, especially for the water shield option

• Capital cost ~8 M$ shared 50-50 between US and foreign

Cu or Ti Vessel

3” QUPID(121 + 121)

PTFE

XENON1T Cryogenics and Purification System

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• Baseline design based on single 200 W Pulse Tube Refrigerator (as in XENON100 and in the MEG experiments)

• Differences:

• Improved thermal insulation. Keep heat losses below 50 W

• Filling and Recovery in liquid phase (as in MEG experiment) however gas phase recirculation-purification

• Use of efficient Heat Exchanger to evaporate and recondense Xe gas for recirculation (Tested at CU)

• With PC150 PTR, with largeer pump and getter, gas flow rate would be ~300 SLPM

• No need for liquid recirculation

Test Set-up at Columbia

Heat Exchanger Performance

96.6 % Efficiency

Cryocooler PDC08: 29WSystem Heat Loss: 12.5 W

XENON1T Gas & Liquid Storage Systems

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Gas Storage: 8 Tanks250 liter each

60 bars360 kg each

Liquid Storage:1 Tank1000 liter

<20 W Thermal Loss1 PTR (PC150)

MEG Experiment

MEGExperiment

Expected Gamma-Background

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(1 Year, Multi-hit Cut, no S2/S1 Cut)

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WIMP Signal and Gamma Background

Gamma rays: < 0.07 /ton-year

Neutrons: < 0.1 /ton-year

Kr85: < 1 /ton-year for 1ppt Kr/Xe

Irreducible background from pp solar neutrino ~0.5 event /ton/year

Location for the XENON1T Experiment

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• LNGS with a water tank acting as shield and muon veto

• LSM with a polyethilene-lead shield and plastic scintillators for muon veto

Collaboration is studying two options for site and shield

Muon-induced Neutrons

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Water Shield at LNGS

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Solid Shield at LSM

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XENON1T at LNGS

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LNGS HALL B

WARP ICARUSXENON1T

XENON1T