Hans Jostlein, May 24, Large Liquid Argon Purity Demonstration— Phase I: Gas Flushing -What -Why ? -How ? -When ? -Define “Success”

Hans Jostlein, May 24, What ? We were told to prove that we can achieve adequate liquid Argon purity in a tank that cannot be evacuated.

Hans Jostlein, May 24, Two Phases We could think of splitting this task into two phases: Phase I: go from atmosphere to “pure enough gas” in a large tank, without evacuation Phase II: Validate a design for a very large LArTPC by using the same design concept in a 150 ton LArTPC (Phase II will not be discussed here)

Hans Jostlein, May 24, Phase I “Go from atmosphere to “pure enough gas” in a large tank, without evacuation” Elements: --a large tank of only “industrial cleanliness” --Flushing (maybe 10 volumes) --gas analysis : Oxygen, Nitrogen, Water, Organics ?

Hans Jostlein, May 24, A Large Tank of only “Industrial Cleanliness” Use the village water tank (equivalent to a 1 kton LAr tank) Tank Preparations: --take out the muck --pressure wash --leak test; fix large leaks --ventilate for a few days to dry it out

Hans Jostlein, May 24, Flushing Strategy In the past we focused on proving the “Argon Piston” concept, Which promises to cut the number of required volume changes in half. This is nice, but not essential It is essential to get to “pure Argon Gas” within a reasonable time and at a cost. Each volume change is 1 ton of Argon gas. Ten volume changes take about a tanker truck and cost about 10 k$

Hans Jostlein, May 24, Flushing with Perfect Mixing The Argon Piston does not work in a tank without thermal insulation. Convection motion mixes the gas very quickly.. Let’s use this to our advantage. Use a blower to assure fast and perfect mixing of the gas in the tank at all times. It takes only a modest fan to do that. Now each volume change takes the contaminants down by a factor “e”. Ten volume changes take them down by a factor e^10 = 22,000 Oxygen will be down to 10 ppm, nitrogen to 30 ppm More volume changes yield lower contamination, Possibly limited by outgassing, virtual leaks, and real leaks.

Hans Jostlein, May 24, Monitoring The levels of O2, N2, and Water will be tracked in the exhaust stream. They will drop exponentially with time, until limited by outgassing, virtual leaks, and real leaks A plot of contamination versus time will show clearly how far this process can be pushed.

Hans Jostlein, May 24, Defining Success / I We will define target levels of O2, N2, and Water. The most conservative target would be to require that the contaminants are compatible with the target electron lifetime after filling, without further gas or liquid purification in the tank. This is almost certainly too conservative and not the best strategy for a large detector. We know we can remove oxygen and water from the liquid very effectively. We also know that much more oxygen and water come with the liquid Argon tanker trucks than with the initial gas atmosphere.

Hans Jostlein, May 24, Defining Success / II We will define target levels of O2, N2, and Water. A more reasonable target would be to require that the contaminants are smal compared to those that come with the liquid Argon tanker trucks. If LAr has 2 ppm Oxygen, then the gas in the tank should have less than (2 ppm X 1000) = 2,000 ppm

Hans Jostlein, May 24, I think we can do much better than that !