LDX Project Status

September 2, 2003


The charging station of the F-coil was received from Ability Engineering on May 30 (see June, 2003 report). Since delivery, the station bottom was removed from the station cylinder and cleaned. This allowed all necessary equipment for installation and rotation of the F-coil at the charging station to be assembled.

Before sending the floating coil to MIT, Ability Engineering performed several vacuum tests using a helium leak detector. No leaks were found between the the cryostat vacuum space and the surrounding atmosphere. A small helium leak of about 2x10^-7 std cc/sec was found at 500 psi helium pressure in the high pressure helium line (that connects to the inner cold helium vessel). The most plausible explanation is that the leak is in the filling line or in the filling valve (and not in the helium vessel since the helium vessel had been leak tested at 2000 psi and has received a stamp of a high pressure vessel). Additionally, a leak was discovered in the heat exchanger circuit (this circuit was leak tested several times before the final closure of the cryostat).

After detailed consideration of these problems it was decided to do the necessary repairs at MIT. The F-coil was safely delivered to MIT by FedEx Custom Critical on August 8.

[Photo: The floating coil located on the charging station rotating

The F-coil was then installed onto the charging station rotating table. Rotation of the F-coil was found to be acceptable. All penetrations through the charging station were found to line up with the ports in the F-coil. The F-coil was then moved from the LDX cell into the engineering shop (across the street), where the vacuum repairs will be made.


Russian customs finally cleared the charging coil and the container with the C-coil was shipped from St. Petersburg on August 12. The ship transported the coil to Antwerp, where the cargo was reloaded to a ship which will go from Antwerp to Baltimore. As of today (September 2) ship is close to Baltimore and will be unloaded around September 5 and then be sent to Boston by truck.

All equipment for the installation of the charging coil below the LDX vacuum chamber has been received from the vendors.


An analytical model has been developed that explains nearly all of the experimental results obtained during the 77K and 17K test campaigns on the LDX L-coil. The model features a single short across the inner section of the upper and lower coil pancakes and eddy current circulation due to inductive coupling with the copper cooling fins on the coil support plate. The model value for the resistance of the copper cooling fins indicates that the radial cuts that were introduced into the cooling fins effectively reduced, but could not entirely eliminate these eddy currents. The analytical model for the L-coil with soon be inserted into the larger, outer model for levitated operation of the F-coil to investigate the behavior of the levitation control system algorithm.


Competitive bids are being solicited to provide additionalelectrical service to the LDX cell. This electrical service will beused to power magnet power supplies, the helium recovery system compressors, several vacuum pumping systems, the L-coil cryocooler, the ECRH power supply cabinets, several diagnostic cabinets, and to provide better distribution of general utility power to the cell. The ECRH supplies have been moved into the LDX area.

Work has also begun to re-activate a pair of ac / dc power convertors for use with the Helmholtz coil pair. The convertors was previously used in the Tara experiment.


The supported-mode catcher has been tested at the full weight of the floating coil. Some refinements are needed in the drive system, and these will be made during the next week when it is removed from the LDX vacuum chamber.