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12 GeV Updates

15 February 2017

After completion of the beam run to demonstrate the Key Performance Parameter (KPP) for the Hall B scope of the 12 GeV Upgrade project, the hall has been busy preparing for the arrival of the Solenoid magnet. This activity requires a temporary de-installation of some of the detectors that were installed for the KPP demonstration. There will be an increase in overhead work during this preparation period.

Hall C is getting ready for the Hall C KPP demonstration beam run in March. The Q3 quadrupole magnet is cold and power testing is well underway. Cool down of the Dipole magnet is nearing completion, and low power testing will start in a few days. The Hall C beam line has been installed with the assistance of the Survey and Alignment group.

8 February 2017

Starting on Feb. 3, high-energy beam was delivered to the upgraded CLAS12 spectrometer for the first time. The beam delivery and the performance of the new Hall B spectrometer was quite impressive, as was the commitment of the Accelerator Operations crew and the CLAS12 collaboration in reaching this important event. Beam delivery throughout the weekend was of high quality. All components of CLAS12 (Torus, Detectors, Electronics, Data Acquisition) worked well, and the CLAS12 team was poised for real-time analysis, monitored through event displays and histograms that had been vetted in advance using cosmic rays. This beam run was focused on demonstrating the Key Performance Parameter (KPP) required for completion of this part of the 12 GeV Upgrade Project. The CLAS12 data from the weekend run has been reviewed by DOE, and concurrence that the KPP has been met was received on Feb. 7, 2017. Congratulations to everyone involved in the achievement of this important milestone!

Thanks to the talented efforts of many hard-working individuals during a dedicated period of leak-checking, pressure-tests and welding, the in-place assembly of the Super High Momentum Spectrometer dipole magnet in Hall C has been completely finished. The magnet is now being slowly cooled down, a process that is expected to take about two weeks. The Q3 quadrupole magnet was also pressure-tested and is cooled down. It is filled with liquid helium, fully instrumented and connected to its power supply. Following verification of the interlocks and instrument readings, the low-power testing of Q3 has begun. Final alignment is underway for all of the SHMS magnets, the target scattering chamber, and the upstream and downstream beam pipes. When all five spectrometer magnets are tested and operational, all vacuum systems closed, and the last detector and concrete blocks installed, Hall C will be ready for its beam run to demonstrate the KPP required for completion of this part of the 12 GeV Upgrade Project.

1 February 2017

The Central Time of Flight (CTOF) detector was installed on a temporary stand in Hall B for the upcoming first beam run for CLAS12. The stand reproduces the points on the Solenoid cryostat to which the CTOF must attach in its final configuration following magnet arrival and commissioning. The CTOF was subsequently cabled, brought to operating voltage and checked for light leaks. The High Threshold Cherenkov Counter (HTCC) was moved from its construction area in the TEDF Building to Hall B and placed on the beamline. The tungsten Moeller shield cone was then added, and the HTCC was rolled into place and hooked up to signal and high-voltage cables, after which circulation of the carbon dioxide operating gas was started. The Silicon Vertex Tracker was then brought to Hall B from the Experimental Equipment Lab cleanroom. After some adjustment, it was rolled into its space inside the CTOF, which in turn had been rolled downstream close to the HTCC. The CTOF was stopped just short of what will be its final operating position in the future in order to accommodate a temporary target for the first beam run. This target is a carbon fiber that is mounted onto a beam harp and placed just at the entrance to the HTCC gas volume. The upstream and downstream sections of beamline were added and pumped out. Finally, some lead bricks were placed at the spot on the existing tagger magnet where the beamline exits to act as extra shielding for the upcoming first beam-tuning exercises.

25 January 2017

Hall B and Hall C saw increased work activities in preparation for the demonstration of each Key Performance Parameter for the 12 GeV Upgrade Project and commissioning runs scheduled for this spring. Hall B completed the installation of the Central Time of Flight and High-Threshold Cherenkov Counter detectors. Work continues on the instrumentation/controls and gas systems needed to support detector operations. Hall C saw progress in both the Dipole and Q3 magnet installations and commissioning. Significant items of note were the completion of the pressure and leak testing of the liquid nitrogen and helium circuits for the Q3 magnet; both systems passed.

18 January 2017

In-place assembly and testing are proceeding on Hall C's three newest superconducting magnets in the Super High Momentum Spectrometer (SHMS). The Q2 quadrupole magnet has reached 106 percent of the current required for the maximum SHMS momentum (11 GeV/c). Stable operation for 11 GeV/c physics has been demonstrated, and final acceptance tests are underway. Welding of the cryogenic helium pipes between the dipole magnet and its service can has been finished and leak-checked, and the first-pass weld of the nitrogen lines is done. The dipole helium circuit has passed its pressure test. Leak-checks of the Q3 magnet vacuum system are underway. Pressure-testing of the Q3 helium and nitrogen circuits will come next. At the same time, connection and checkout of the Q3 and dipole instrumentation systems are moving forward.

With all but one of the SHMS detectors in place, a cosmic-ray trigger has been set up to collect signals from the detectors and exercise the data-acquisition hardware and the event-reconstruction software. Stands for the beam pipe downstream of the recently installed target are in place, and much of the vacuum pipe has been erected. Limit switches and wiring to allow remotely controlled rotation of the SHMS is being prepared.

12 January 2017

The Torus magnet for CLAS12 has been parked at a temperature of 80 Kelvin for the past two months awaiting the upcoming beam run in Hall B. t will be brought back down to liquid helium temperature at the end of January to prepare for the run. The drift chambers have all been suspended from the Torus cryostat and had their services attached, and the Forward Carriage has been rolled upstream to its operating position next to the Torus.

The five coils of the Solenoid magnet have now been spliced into one continuous circuit, and the resulting magnet "cold mass" has been covered with reflecting aluminum foil. The radiation shields are now being fit to the outer circumference of this assembly. After this step, the multi-layer insulation blankets will be added and then the entire assembly will be suspended inside the cryostat outer shell; eight suspension links are welded to the cryostat and then attached to the cold mass by insulating links in this step. The conical end regions and the bore tubes of both the radiation screen and the cryostat were prepared earlier and will be attached after the cold mass is suspended from the cryostat outer shell in order to close the cryostat. Planning for shipping the Solenoid to Jefferson Lab is well underway, including the final steps in the design of the shipping cradle and isolation springs needed for the road trip to Virginia.

4 January 2017

As the 12 GeV upgrade project nears the commissioning phase for Halls B and C, the last of the scheduled modules of the Accelerator Readiness Review (ARR) is scheduled for Jan. 9 and 10. The ARR committee is charged with determining if Jefferson Lab is prepared to deliver beam for the commissioning and operation of Experimental End Stations (Halls) B and C, and the experimental equipment associated with the 12 GeV Upgrade Project, in a safe and efficient manner. To this end, both halls are continuing with the installation of the remaining magnets, detectors, beamline components and associated infrastructure/services.

In Hall B, the Central Time of Flight has been placed on the mock-up support stand, and installation is underway. Hall B also continues working the various detectors' gas delivery systems and remaining utilities. Hall C has installed the beamline supports and continues with hookup of the Q3 and dipole magnets.