1. 1 Liquid Argon Dark Matter: Synergies with R&D for Neutrino Detectors: Chemically clean Argon for drifting electrons and light output (Oxygen and H20 relevant for both, N2 relevant for light only) TPC construction and HV feedthroughs Light detection - waveshifting, cryogenic PMTs and Bases Effects of detector materials on Argon purity (H20 and O2)

2. 2 Liquid Argon R & D specific to Dark Matter Search Context is collaboration with Princeton, Temple et al., Approach is to treat general issues: Ar39 background - 1 Bq/kilogram (560 keV max beta) Source of Depleted Argon from Gas Wells in US (~1 kg/day now) Depletion measurements (Bern) limited at x25 below atmosphere Building High Pressure (2500 psi) Ion Chamber at FNAL, with muon veto and low-activity-lead shield to go in NuMI tunnel. We’ve been practicing on a chamber we made, using a shield in the Radiation Counting Lab at Fermilab => electronics noise level is acceptable.

3. 3 Ion Chamber in lead shield at Fermilab Counting Lab. 220 electrons rms noise 39-Ar spectrum flat to 560 keV 560 keV ~ 20,000 electrons 60 keV X-rays (241-Am) in 8.5 Bar Argon

4. 4 Lead Shield for Ion Chamber High Pressure Ion Chamber (Copper body,Titanium bolts)

5. 5 Program to develop general expertise for LAr Dark Matter: 20 kg device at Princeton Device to develop light-collection, TPC design, PMTs (from Hamamatsu), bases, and electronics readout. Fermilab supplying PMT bases, HV feedthroughs, electrostatics design (C.J. Martoff, guest)

6. 6 Next three years: Complete and study 20 kg device. Investigate wave-shifter technology - base materials, WLS chemicals and application techniques Investigate effects of materials on light output and detection - longevity of coatings, effects of impurities in Argon Develop prototype scale (1 meter distances) device Complete Argon system with atmospheric Argon, full size TPC (including HV and light reflectors); partial readout coverage to pursue development of: light sensors, read-out electronics and DAQ.

7. 7 Extras..

8. 8 Argon Liquid Argon Gas Acrylic Steel Bolt Luminescence Region Grid in liquid Anode Field Lines from liquid surface 3-D Study of Electrostatic Asymmetries Dielectric Constant Cryostat Walls at Ground Field Cage C.J.Martoff

9. 9

10. 10 39 Ar Ion chamber vessel