The temporary construction opening (TCO) on ProtoDUNE-SP is closed! The operation went smoothly and on schedule, starting on April 30th and finishing on June 12th.
The first order of business was protecting the delicate TPC and photon detector system from light, dust and other potential contaminants or hazards that the welding and grinding operations might generate. A team of CERN technicians built a buffer room around the TCO, effectively creating a separate, isolated environment inside the cryostat for the work.
CERN Neutrino Platform design staff designed a two-piece TCO door: a six-meter-high section to cover the top portion of the TCO, and a two-meter-high section for the bottom. Installing the top section first allowed access through the TCO for a good portion of the installation period, reducing the need to use the small access hole at the top of the cryostat.
For each piece, CERN technicians first bolted and welded the outer steel structure to the rest of the cryostat. As each piece was completed, a crew from Gabadi, the firm that had installed the insulation panels and welded the inner corrugated membrane for the cryostat, returned to set the two insulation layers in place and weld this last portion of the membrane shut. For the bottom piece, the crew had to enter the cryostat via the access hole at the top — the only entrance still available!
Actemium, a Gabadi subcontractor, together with CERN staff performed final leak checks the week of June 11th. The ball now passes to the ProtoDUNE-SP crew for the final assembly of the second drift volume and installation of all the cryogenic instrumentation — the purity monitors, temperature gradient monitors, cameras, and high voltage feedthrough. This is expected to take the rest of the month of June. July and August will be dedicated to purging, cooling, filling, and commissioning the cryogenic system, with the end of August as the target date for activation of the detector and first beam data.