Transcript ArDM

Cracow Epiphany Conference 2010
The Argon Dark Matter
Experiment
Małgorzata Harańczyk
IFJ PAN Kraków
Sławomir Mania
University of Silesia
Collaboration
Switzerland
ETH Zurich
Zurich University
Spain
University of Granada
CIEMAT
Poland
Soltan Institute for Nuclear Studies, Warszawa
H. Niewodniczański Institute of Nuclear Physics , Kraków
University of Silesia
England
University of Sheffield
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Outline
• Conceptual design of the ArDM detector
• Small R&D test setup with LEM readout
• Status of the experiment
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ArDM
• New generation WIMP detector (simultaneous
measurement of light and charge)
• 850 kg liquid Argon detector
• Measurement of WIMP recoil energy spectrum
Energy threshold ~30 keV, 3-D imaging,
Trigger rate below 1 kHz
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Conceptual design
A WIMP collides
with Argon inside
the detector…
…transmitting its kinetic
energy to the nucleus…
…the Argon nucleus
recoils….
Scintillation light and ionization
electrons are produced from
interactions with neighbouring
Argon atoms
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light + charge
signals
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Conceptual design
• Large volume high electric field,
Extraction of the ionization electrons
from the liquid into the gas phase
• Large area position sensitive charge
readout with LEM’s (3rd-dimension from
drift time)
• Large area VUV sensitive light readout
with good time resolution (also used for
trigger)
Efficient liquid argon purification system
Careful choice of detector materials (to
keep low the background due to natural
radioactivity)
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Conceptual design
80 cm
120cm
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First test – May 2009
•
22Na
and 137Cs sources
• Only half (7) of the PMTs were installed
• No drift electric field
-Light yield is consistent with
expectations (0.5 p.e./keV with 7 PMTs);
-First successful detection of 50 keV
signal in 1t detector;
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Small setup for charge readout R&D
Small double-phase argon TPC
Max drift length 20 cm (0.5 kV/cm)
One LEM 1 mm x 10 cm x10 cm
Large Electron Multiplier
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Small R&D setup
Before …
and after measurements .
A few days long run of stable work with 34 kV/cm in LEM holes
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3D event imaging
Typical cosmic muon
event
the charge readout with striped LEM and
anode plates (2D)
+
the light signal to define t0 drift time
=
a precise 3D reconstruction of the event
Data were taken by MH and SM
during tests at CERN in summer 2009
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3D event imaging
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The near future
• Next test of the ArDM detector foreseen in
February 2010
14 PMT, drift electric field to measure ionization
• Tests of new types of LEMs are going on with a
small test setup
(the full size prototype is still in a design phase)
• Detector ready for underground operation by
the end of 2010
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SUN LAB
The Sieroszowice Underground LABoratory
-one of three possible locations for
the underground ArDM operation
KGHM copper mine
in the west-southern Poland
Salt cavern
1 km below the surface
2200 m.w.e
very low level of natural
radioactivity background !
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Acknowledgements
We want to express our gratitude to Andre Rubbia, and Alberto
Marchionni for making it possible to work with ArDM team in CERN.
We would like to thank Filippo Resnati, and Devis Lussi for
the kind hospitality extended to us.
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Background rejection
Neutrons:
from radioactive elements in materials
and from cosmic muons
Electrons/Gammas:
from radioactive elements
⇒ Neutron events look like WIMP-events
⇒ in Liquid argon e/g events look different
from WIMP-events
– Different shape of the scintillation light
(ratio fast/slow components)
– Different light/charge ratios
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