LBNE builds 35-ton prototype cryostat

Construction workers examine the concrete support for the 35-ton membrane cryostat for the LBNE project. Photo: Barry Norris

The Long-Baseline Neutrino Experiment is moving ahead with its prototyping activities for a liquid-argon far detector.

The LBNE far detector will require a cryostat to hold between 5,000 and 17,000 tons of liquid argon at 89 K – a significantly larger volume than any existing liquid-argon detector. The LBNE project team is currently constructing a 35-ton-capacity prototype cryostat at PPD’s PC-4 facility with the primary purpose of verifying that the high purity levels achieved last year in the Liquid Argon Purity Demonstrator, LAPD, are reproducible in a non-evacuated cryostat of the type planned for the LBNE detector.

Cryogenic engineers David Montanari and Terry Tope are coordinating the prototype’s construction. Physicist Alan Hahn will coordinate the testing program.

Given its size, the detector cryostat will need to be constructed on site by welding together modular pieces to form a single membrane. While this technique is commonly used in the construction of the enormous cryostats used in commercial storage of liquid natural gas, that industry’s requirements are very different from LBNE’s, said Montanari. The prototype must demonstrate that this type of construction can meet LBNE’s purity requirements without prior evacuation.

The reinforced concrete housing for the prototype was completed in May. Staff from the vendor Ishikawajima-Harima Heavy Industries is onsite to train Fermilab welders and technicians and to supervise the cryostat construction, which is expected to span a couple of months. According to Montanari, the prototype has been designed to share many components with LAPD, enabling the two programs to run in parallel. In particular, he said, the prototype will share LAPD’s liquid-argon purification system – an expensive item.

Expanding the scope of the 35-ton prototyping program to track cosmic rays and test light-collection schemes is under consideration. This would require insertion of a reduced-scale time projection chamber into the cryostat in a second phase.

“We have to wait to find out whether we will be building LAr1,” Hahn said, referring to the planned 1,000-ton-capacity prototype intended to test the full installation process and operation of the detector. “If not, we’ll need to test the TPC and photon-detection designs in this one.”

—Anne Heavey