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31 March 2016

Experimental Hall B

The cryogenic service tower has been installed on the CLAS12 Torus magnet in Hall B. The lines for magnet cryogens and the main current bus are being connected. After a leak check, the magnet will be ready for an initial vacuum pump-down. In parallel, the cryogenics distribution can that serves as interface between the End Station Refrigerator and the CLAS12 magnets has arrived and is being checked. The Experimental Readiness Review needed prior to the cool-down is set for April 13. The in-field checkout is ongoing for the control logic and instrument readouts for the magnet, the main power supply for the Torus has been tested, and installation of the various parts of the vacuum pumping system is well underway.

The fifth coil (of five) for the CLAS12 Solenoid is nearing the half-way point in winding. Leaks in the helium cooling channel of the bobbin holding the first four coils resulted in schedule delay. The involvement of subject matter experts at Jefferson Lab was critical to development of a leak repair plan, including fabrication of critical parts in our machine shop. The components needed for the Solenoid cold mass assembly are arriving steadily at the vendor, ETI. The Manufacturing Readiness Review of the cold mass assembly procedures is scheduled for March 30.

Experimental Hall C

Work progresses for the motion controls for subsystems on the Super High Momentum Spectrometer (SHMS) in Hall C. The shield house incorporates two very heavy concrete doors, which are opened and closed with the assistance of electric motors. The system logic was tested and then modified to assure that the doors will stop moving if the person operating them lets go of the control button. In addition, new motor drivers for the collimators on both of the Hall C spectrometers have been installed and configured to work with the existing motors. The collimator box for the SHMS will soon be put in place, completing the spectrometer's vacuum-channel connection between the HB and Q1 magnets.

Major components of all three remaining SHMS magnets are back in the vendor, Sigmaphi, magnet factory in France. The helium vessel that contains the Q3 coil just returned from the metalwork shop. The Q2 magnet is on its transatlantic shipping cradle and is being outfitted with a Cryo-Control Reservoir (CCR). The dipole, most advanced of the three, now has its nitrogen supply/return manifold installed. Once the leak-checking of the nitrogen system is complete, the end-caps will be welded onto the dipole vacuum vessel, concluding the factory assembly of that magnet. Equipment is being readied for checking its magnetic field before it is shipped to Jefferson Lab. Plans for rigging and final assembly of the magnets in Hall C are well-advanced.

10 March 2016

nstallation work in Hall B is very busy and presents many overhead hazards. Detector work is proceeding with the cabling of the Low Threshold Cerenkov Counter. Torus magnet activities include installation of the cabling raceways as well as additional infrastructure and support services, such as Low Conductivity Water, electrical, cryogenic piping and gas systems. With all of these overhead activities, it is important that precautions be taken to prevent tools and equipment from falling. Examples of solutions that will reduce risk are to tether tooling when possible, organize and safely store/transport tools and materials, and maintain good housekeeping in your work area.

2 March 2016

Sigma Phi, the French company building the Dipole, Q2 and Q3 magnets, has made significant progress with assembly over the last month. The Dipole is currently slowed down by problems with fitting the liquid nitrogen supply and return manifolds to the thermal shields. Q2 is also experiencing some delay as a different subcontractor is behind schedule producing the cradle needed for the next assembly step. All other internal components of the Dipole are permanently fixed in place, and Q2, with the coil now suspended by the barrel portion of its vacuum vessel, is not far behind. Preparation is moving ahead for the cryogenic, vacuum and instrumentation interface systems of both the Dipole and Q2 magnets. The Dipole interface "Cryogenic-Control Reservoir" will be attached to the magnet in Hall C, whereas the systems for the Q2 and Q3 magnets will be integrated in the factory.

On the Jefferson Lab site, checkout of the Super High Momentum Spectrometer detectors, trigger system and electronics continues. Field mapping of the HB magnet has been performed, so that final components of the beamline may be designed. Important improvements to the superconducting magnet power and protection systems were engineered during the recent extensive testing of the HB magnet. Those improvements, as well as software patches, are being applied to the controls for the other magnets.

24 February 2016

The design of the downstream support structure for the Central Time of Flight (CTOF) detector for CLAS12, as well as that of the installation arm, is now underway. The light fiber bundle to distribute monitoring laser light to the CTOF slats is on order, and the transport crates to move the slats to Hall B have been received. Timing measurements of the assembled CTOF slats have been used to determine the best discriminator settings for timing resolution. Refurbishment of the last of the six sectors of the Low Threshold Cerenkov Counter (LTCC) is complete, with the windows attached and pressure and leak tests passed. Installation of five of the six LTCC sectors has been done, with the sixth sector staged for installation. Installation of the Forward TOF panel 2 sectors is planned for early March, which will complete the Forward Carriage part of CLAS12. The first article is expected to arrive soon for the remaining fast electronic modules, the crate trigger processors, needed to complete the data acquisition and triggering systems for Hall B.

17 February 2016

In November 2015, the heating element for the current lead mass flow overheated the lexan-like cover around the Super High Momentum Spectrometer Q1 magnet leads in Hall C, causing a small fire. The thermometers of the lead mass flow heaters were cross-connected so that the thermostat controls were not properly matched to the correct heater. The top of the cryo can is congested with piping, valves and associated wiring, so tracing the lines visually is difficult. This is compounded when equipment is similar and not labelled or otherwise identifiable. The system initial setup was done in February 2015, and parties are not aware of any changes that were made to this setup since then.

    Statement of Lessons Learned:
  1. Although hard to accomplish, maintaining a clean and organized work space will aid in the workers' ability to navigate to various hard to reach areas within congested work areas.
  2. Whenever possible, purchase systems as a single unit. This will eliminate the possibility of getting the wire connected improperly during the installation process.
  3. As per the fire extinguisher training, when you see or suspect a fire, pull the closest fire alarm in a timely manner, and the appropriately trained personnel will respond to your area.
  4. Whether temporary or permanent systems, design and fabrication need to conform to established engineering principles, including the identification and mitigation of hazards.
  5. Conformance with the lab procedures for fabrication and modification of electrical equipment that is not listed by a Nationally Recognized Testing Laboratory will ensure that a subject matter expert's review is completed, so that potential hazards can be identified and mitigated.

11 February 2016

Now that the Horizontal Bend magnet is running at full current, the magnetic fields it generates are being "mapped" (carefully measured at each position in a three-dimensional grid). Detailed knowledge of the main field within the bore of the magnet is needed, so that physicists can interpret the data that comes from the spectrometer during experiments. It is also necessary to have a good measurement of the field outside this particular magnet, because it can deflect the primary electron beam during some experiments. Devices that minimize or counteract this deflection must be designed now, using the measured field as a guide.

In France, the repair of the damaged inner thermal shield of the dipole magnet was completed relatively quickly, so the vendor chose not to divert attention to making early measurements of this magnet's field. The entire shield is made up of an inner cylinder, an outer cylinder, and two endcaps that connect the cylinders. Both the inner and outer surfaces of the shield assembly get a covering of aluminized mylar super insulation -- like many layers of 'space blanket'. All of these parts are in place now, and welding has begun to hold them permanently in position. The pipes that supply liquid nitrogen to cool the shields are being joined by welding, too. Once they have been certified leak-free, the thick outer vacuum vessel will be sealed by welding its two endcaps in place. At this point, in just a few weeks, the dipole factory assembly will be finished and it will start a series of magnetic and leak tests before being readied for shipment to Jefferson Lab's Hall C. The first of the two identical quadrupole magnets, Q2 and Q3, is only several weeks behind the dipole in the same fabrication process. All of its parts are ready and are being put together in a trial fit now. Some of the shield subassemblies for the last quadrupole magnet still need final welding details for mounting brackets, and a final leak check. They will arrive at the magnet vendor's factory only after space becomes available."

3 February 2016

The main support legs have been installed on the Torus magnet for CLAS12 that is being assembled in Hall B. The weight of the magnet has been transferred to the legs, following which the assembly "spit" and its two blue support stands have been removed. Next steps include a detailed survey and then adjustment of the positions of the magnet coils proper, relative to the vacuum jackets. Once this is complete, the thermal shield and hub cryostat can be added to the currently exposed cold hub at the center of the magnet. The Torus Service Tower will be added at that point. It supplies cryogens to the magnet and also serves as a cooled conduit for the two main power leads and for the various instrumentation wires coming from the magnet internals and measuring pressures, temperatures and voltages across splices. The Distribution Can for cryogens, which acts as the interface between both magnets and the End Station Refrigerator, is undergoing final manufacturing checks at the vendor in Chicago. The in-field checkout has begun for the control logic and instrument readouts for the magnet, and ordering, testing and installation of the various parts of the vacuum pumping system is well underway.

The vendor for the Solenoid magnet for CLAS12 has epoxy-impregnated both of the two "Intermediate" coils. Preparations and trial runs are underway for the major subsequent step, which is cooling the two Inner coils and then inserting them into machined cavities in the winding bobbin for the Intermediate coils to form the main four-coil winding pack for the Solenoid. The bobbin for the fifth, or "Shield", coil has been delivered to the vendor and set up on the winding machine. Insulating layers and the guide pieces for the power leads are being attached to this bobbin, after which the Shield coil will be wound and then epoxy-impregnated. The parts for the Solenoid cold mass assembly are on order in anticipation of the next step in Solenoid assembly after Shield coil winding is complete. In this step, the five coils are joined into one assembly by suspending the bobbin with the four Inner and Intermediate coils inside of the bobbin for the Shield coil. This "cold mass" assembly is then covered with a radiation screen and multi-layer insulation. The final major step in building the Solenoid will involve insertion of this cold mass assembly into the outer vacuum cryostat, which is being procured.

27 January 2016

In Hall B, the magnet support legs were installed and the bases grouted on the Torus magnet. The plan is for the "spit," which has served as the temporary support for the magnet during the coil installation phase, to be removed later this week.

With snow falling and Jefferson Lab about to close early, on Friday, Jan. 22, the Horizontal Bend magnet in Hall C successfully reached a major goal following months of analyses, testing and review. After "training" at lower currents, the magnet was operated at 4,000 Amps, the current required for running the new Super High Momentum Spectrometer at its highest momentum.

20 January 2016

Power-testing of the Super High Momentum Spectrometer Horizontal Bend (HB) magnet has resumed after engineers implemented further modifications to improve the response time of the power supply's quench-detection circuitry. When this magnet reaches the current required for 11 GeV/c operation, its magnetic field will be mapped, and the magnet construction contract with Michigan State University will be complete.

The SHMS dipole magnet assembly has progressed to the point that the coil, in its helium vessel, is now surrounded by the cylindrical outer insulation, thermal shield and vacuum vessel. The weight of the coil is now permanently held by the outer vessel rather than by temporary tooling. The full assembly is more than thirteen feet long and five feet in diameter. The inner thermal shield was damaged during insertion, so magnetic-field mapping will proceed while the repairs are made to the shield. In Hall C, the huge iron yoke which will contain the dipole magnet has been leveled and opened. It is now ready and waiting for delivery of the magnet.

13 January 2016

12 GeV Hall B: Non-Magnet Update
The first article is expected to arrive soon for the remaining fast electronic modules, the crate trigger processors, needed to complete the data acquisition and triggering systems for Hall B. The installation and check-out of the balance of the VXS crates and controllers together with the fiber optic networks for data and trigger data transmission is wrapping up in the hall. The construction of the upstream support structure for the Central Time of-Flight (CTOF) for the CLAS12 spectrometer has been completed, as has fabrication of most parts for its light monitoring system and of its transport crates. Refurbishment of the last of the six sectors of the Low Threshold Cerenkov Counter (LTCC) is nearly complete, with the windows being attached, after which pressure and leak tests remain. Installation of the LTCC and the Forward Time of Flight panel 2 sectors is planned for February 2016, which will complete the Forward Carriage part of CLAS12.

6 January 2016

Hall B is prepping for the installation of the Torus magnet support legs. Up to this point, the Torus assembly has been taking place with the Torus on a "spit." This allowed for rotation of the magnet, which increased efficiency and safety during this phase of construction. The legs are the permanent support and will be installed in the near future. Hall C continues incremental testing and measurements of the horizontal bend (HB) magnet. This activity is part of the final acceptance tests of this superconducting magnet.

 

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