What is LAPD?

Liquid Argon Time Projection Chambers (LArTPCs) offer an opportunity for novel neutrino physics. They can provide bubble-chamber quality event images by drifting ionization electrons created by the passage of charged particles through the liquid to high voltage readout planes. Since argon is relatively cheap and plentiful, one can conceive of detectors with multi-kiloton volumes of liquid argon.

A principal challenge for large LArTPCs is the removal of electronegative impurities such as oxygen and water that capture the ionization electrons.  Currently, liquid argon vessels are evacuated to remove the oxygen and water present in the ambient air prior to filling with liquid argon.  As physics requirements dictate larger cryogenic vessels to hold bigger detectors, the mechanical strength required to resist the external pressure of evacuation becomes prohibitively costly.

The Liquid Argon Purity Demonstration (LAPD) will attempt to achieve the ultra high purity required by LArTPCs in a vessel that cannot be evacuated.  Prior to filling with liquid argon the air will be removed from the tank by purging with argon gas.  The volume of the tank is 22,000 liters.  Dispersed throughout these 22,000 liters of liquid argon, a mere 0.00075 grams of oxygen can be tolerated. 

How does the Mechanical Department support LAPD?

The PPD Mechanical Department is currently designing and fabricating the cryogenic infrastructure for operation in the 2^nd half of 2010. 

For more information: LArTCP website