LDX Project Status

February 4, 2000

Helium Vessel

Ability finished the practice welding of inner diameter of the Inconel half elbows containing the dummy coil form. Weld shrinkage and temperature rise of the inner wall of the dummy coil were measured. The temperature rise with a protective stainless steel shield (93 - 117 deg F) was significantly lower than without it (170 - 235 deg F), and we have decided to use the protective shield for the real weld to minimize coil heating. The practice weld on the outer diameter will be completed after modifying the welding positioner to allow reduced speed. Both top and bottom half-tori have been fully x-rayed, and the radial welds accepted. The dimensions of one half-torus has been successfully blacksmithed to adjust it to acceptable tolerances (approximately 0.010 - 0.012 inch). The next steps are to adjust the other half, to machine the datum surface on the bottom of the lower half torus, and to make weld preps according to the practice welding.


Floating Coil Cryostat

Dr. Garnier visited Ability Engineering on January 10 - 13 to supervise the manufacturing of the fiberglass shield sample. A half elbow was use as the mold to practice the shield model. The resulting fiberglass shield, including dummy cooling tubes and shaped lead plates appeared to be excellent. Copper strip thermal bridges were soldered to lead plates and to the cooling tubes by low temperature indium solder. The upper cover of three layers of glass cloth will be finished later using the vacuum bagging technique.


Floating Coil Winding

The LDX floating coil winding operation at Everson Electric was interrupted on January 10, when the insulating tape that is wound around the conductor jammed in the taping machine. This accident damaged the conductor about 91 meters from one end. A total of 15 turns had already been wound in the pancake portion of the winding at the time of the accident. It was determined that the conductor is sufficiently long to eliminate the 91 m length. Since January 10 we have evaluated possible taping machine modifications that would (1) minimize the possibility a tape jam and (2) if a jam does occur, prevent the jam from forcing excessive strains in the conductor. The concepts for these modifications were provided by MIT, but the detailed implementation will be performed by Everson. We visited Everson on February 2, to evaluate changes they had made to the taping machine. These changes included:

  1. Eliminating unflanged idlers in the tape path. A flanged idler perhaps would have prevented the jam in the first place.
  2. Slowing the taping head rotational speed. This reduces the inertia in the head.
  3. Adding a +/- vertical displacement sensor which trips a relay, which, in turn, trips the drive power to the taping head motor.
  4. Increasing the supported conductor span in the center of which the taping loads are applied. This increases the allowable conductor displacement before excessive strains are reached. This allowable displacement must accommodate both the setpoint displacement and the additional displacement caused after the sensor trips but before the head stops.
  5. Consider adding a brake to the taping head drive belt, if required.

Everson has implemented steps 1 - 4 above. During the visit, we observed that the displacement sensor which Everson had implemented was, in fact tripping the system off line before excessive strain is forced into the conductor for some angular positions of the taping head. The sensor, however, was desensitized at taping angles near horizontal due to friction in the sensing mechanism. The recommended fix was to implement either a simpler sensor concept which was given to Everson (preferred) or modification of the existing sensor to eliminate the friction. Everson will implement the suggested change and report progress on February 4. If the changes are successful, winding will restart using the written recovery procedure during the week of February 7.



Work on the final design is continuing. Long-stroke aluminum air cylinders have considerably simplified the mechanism for launcher motion. Plans are underway for the final design review at the end of February.


Charging Coil

The final details of the contract with STC "SINTEZ" of Efremov (Russia) to manufacture the charging-coil is nearly complete and will be shortly signed by both sides. "SINTEZ" has now started to design the coil. Darren Garnier and Alex Zhukovsky visited Efremov (St. Petersburg) and their sub-contractors in the charging-coil project (Cable Institute and Bochvar Institute, Moscow) on January 16 - 22. At Efremov, they observed the pilot plant, the cryogenic test facility and had discussions with the main engineering staff involved in the charging -coil project. As a result of these discussions an interface document was issued. Darren and Alex also visited "Cryovacs" the company which will produce the charging-coil cryostat. They observed a technology that Cryovacs has developed to make highly reflective surfaces that will reduce the heat leak into the cryostat and therefore reduce the liquid helium consumption of the coil. In Moscow, Darren and Alex also visited the Cable Institute who will make the NbTi conductor for the charging-coil (a 1.2 mm strand conductor that is soldered into a Cu C-channel and is surrounded by Kapton and glass insulation). They also met with Bochvar representatives who will build HTS current leads for charging-coil. As a result of the visit and discussions Darren and Alex formed the impression that the charging-coil will be manufactured by a very professional and experienced staff of various companies. In addition it was made clear that SINTEZ has considerable experience in organizing complex projects that require the cooperation of several venders. A detailed report about the Russian visit is being written.

Webmaster: D. Garnier
Last updated: Tue, Apr 25, 2000