First CPA and field cage inserted into SP cryostat

The assembly in the cryostat. The TCO is too narrow for the assembly to fit through in its normal configuration, so the crew had to use ratchet straps (still attached in the image) to pull the field cages together. The panels overlap due to height constraints. Credit: J Meier

Milestone achieved: As of the evening of November 22, 2017 a joint CERN/Ash River team smoothly and successfully installed the first of three cathode plane assemblies (CPA), complete with its attached Field Cage (FC) assemblies, on its supporting beam inside the ProtoDUNE-SP cryostat at CERN.

When complete, the 7 x 6 m2 cathode plane, made up of the three CPA modules, as they are called, will bisect the ProtoDUNE-SP TPC, dividing it into two equal-sized drift volumes. The plane will provide an equipotential surface at –180 kV as well as a constant bias voltage and current to the FC resistor-divider chains.

The three CPAs, each made up of six panels, were constructed earlier this year by Steve Magill and Frank Skrzecz of ANL and their team. During a similar timeframe, Mike Wilking and Kevin Wood were assembling the FC frames at Stony Brook. The teams independently completed the CPA and FC components and shipped them to CERN in mid-July.

On November 7th Magill and Skrzecz arrived at CERN, unpacked the stored CPA panels, and assembled them in the cleanroom outside the cryostat. Following that, a combined team of CERN riggers and Bill Miller, Jerry Meier and Tom Weber of Ash River lifted the CPA onto a support rail. Once the quality assurance tests on the HV and CPA field shaping strips were complete, the team lifted the four FC frames and assembled them together into the first complete module. Finally, the CERN/Ash River team inserted the module through the Temporary Construction Opening (TCO) and onto its supporting beam in the cryostat. Et voilà!