LDX Project Status

September 14, 1999

Helium Vessel

Ability Engineering has performed several more welding samples of the Inconel 625 helium vessel, and good estimates of shrinkage expected during weld closure are now available. First attempts to make controlled end welds of the small torus radius showed reasonable shrinkage but unexpected distortion. After intensive consultations between PSFC and Ability, we have decided to fully vacuum anneal the half elbows (at 1900-2000 deg F) to relieve internal stresses produces during cold formation. To date, two trial elbows have been annealed. Fixtures for machining the elbow ends have been completed, and complete procedures for the final closure welds will be established using these trial elbows prior to enclosure of the floating coil.

 

Floating Coil Cryostat

Ability has completed preliminary sketches of the bayonets and the docking station. Sketches of the vessel portion of the docking station and an observation dome are nearly formalized. Ability is now receiving quotations for the spinning of the outer vacuum vessel torus halves. These quotes are being evaluated and revised to be compatible with the required tolerances and the final machining for equatorial welding. Ability completed initial testing of the manufacturing technique for the lead heat shield. Shield test pieces have been made from silver brazed and copper flame-sprayed monel screen. Lead sheets have been successfully cold-welded to both sides of the treated screen. Flat models made of two lead sheets and monel screen survived thermal cycling. The samples have been sent to the PSFC for structural examination. A final model of the shield will be shock loaded to qualify the shield for 10 G collisions.

 

Floating Coil Conductor

IGC delivered the completed LDX conductor to Everson. Prior to winding the floating coil, several conductor test samples were sent to Brookhaven National Laboratory for testing. These samples are representative of the final conductor located at (1) the take-up spool layer transition region, (2) the middle of the spool, away from the transition region, and (3) the straight section of the soldering line, prior to take-up. The first tests conducted by BNL measured conductor performance of the transition and curved samples at nominal background fields of 4, 5 and 6 Tesla. (A photograph of the test probe was shown in an earlier update.) The test samples are clamped tightly to a G-10 fiberglass insulating spacer in order to secure the sample against magnetostatic forces when energized with currents up to 6 kA. In one sample, the superconducting cable protruded approximately 0.5 mm from the copper channel within a localized region about 1 cm in length. The strong clamping created a localized high-stress region as evidenced by local crushing of the G-10 spacer. In this region, the conductor critical current was measured to be about 50% of the expected value based on our single-strand tests. In the remainder of the samples the superconducting cable was properly seated within the Cu channel and the conductor performed as expected. The sample having the protruding superconducting cable will be examined at MIT. Additional tests will occur during the next few weeks after the protruding cable is resoldered to be flush within the copper channel.

 

Floating Coil Winding

Everson Electric has completed the installation of the major components of the winding tooling, including the payoff station, the insulating station and the winding machine. Everson has completed a dummy winding using bare copper channel. Protective copper sheets, which will be impregnated with the winding, have been trial-soldered and measured ultrasonically at MIT for quality of the solder bond. The quality of the solder bond in these sheets was found to be inconsistent, and Everson is modifying the sheet soldering process in accordance with comments from MIT to use a combination of heaters, clamping and a lower-melting-temperature solder. Everson is now completing new sheet soldering samples for additional testing at MIT. In addition, a revised and improved design for the copper sheets was completed by MIT. The inner sheet has been moved from the coil ID to a location between the first and second winding layers. Also, strain relief and additional through holes are now incorporated into the sheet design to keep cool down and operating loads from appearing across the soldered joints. Winding transition ramps have been fabricated from G-10. A fixture is being prepared to help guide the conductor while winding the pancake portion of the winding. The coil form is being checked for leak integrity, as it provides containment for the epoxy during impregnation after winding. It is anticipated that F-coil winding will begin as soon as the conductor tests are completed at BNL.

 

Vacuum Vessel

The vessel was thoroughly cleaned, and installation of the vacuum pumping system began. The first pump down occurred on September 14, and leak-checking of the vessel has begun.

Test cryostat

The cryostat vacuum space has been pumped out. The cryostat insulation was tested with the cryostat filled with liquid nitrogen. No cold spots were found on the outer surface of the cryostat. A small leak into vacuum space was discovered but our vacuum pumping can maintain an acceptable vacuum (10-4 torr) in the cryostat vacuum space containing MLI insulation. New thermal insulation has been installed inside the cryostat below its cover (styrofoam plates with aluminum foil) plus aluminum baffles below the Styrofoam plug. New supports for the mandrel of the floating coil were being fabricated and mounted and the cryostat cover was modified with new o-ring Viton seals. The vapor-cooled current leads have been equipped with extension OFHC leads and mounted to the cover plate.

Simplified Launcher

R. Ellis (PPPL) completed the conceptual design for the simplified launcher. The design review for the launcher system will be held on September 21.

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Last updated: Tue, Apr 25, 2000