History from August 1995

Clark achieves 50 tesla !! (August 1995)


We at the Clark University pulsed magnetic field laboratory are proud to announce that we have reached 50 T in an 18.2 mm bore with our pulsed magnetic field apparatus. The pulse has an 11.5 ms rise time which I believe makes it one of the longest 50 T pulses in the world. The system can be used in a crowbar mode with a thyristor switch giving it a 50 ms fall time or with a mechanical switch in a symmetrical mode. We are presently limited to 43 T using the thyristor switch, but we will upgrade the thyristor as soon as additional funds are found. The energy comes from a 350 kJ capacitor bank with a maximum voltage of 5000 V. The 50 tesla pulse was reached by charging the bank to 4500 V and the current at maximum field was 12330 A.

The magnet is internally reinforced with S-glass and was designed under the direction of Fritz Herlach and Luc van Bockstal, and built by Liang Li at the Katholieke University in Leuven, Belgium while Prof. Agosta was visiting last summer. We used two types of wire in the construction, Glidcop for the first eight layers and soft copper for the outer six layers. The magnet also has a 2 cm thick layer of steel ribbon wound on the outside for external reinforcement. We are very grateful to the Leuven group for their help while we were building our capacitor bank and for our first high field magnet described above. Other groups were also very generous to us with either apparatus or advice. Below I first list the people who offered advice to us:

Fritz Herlach and his group at Katholieke University,Leuven, Belgium

Dwight Rickel and Heinrich Boenig, NHMFL, Los Alamos
Greg Boebinger, AT&T Bell Labs
Si Foner and Emanuel Bobrov, FBNML, MIT

And the companies that donated equipment to us:
ASEA Brown Boveri(ABB), Pittsburgh, PA
ABB Industrial Systems, Inc., New Berlin, WI
Raytheon Co., Lexington, MA
Amacoil, Inc., Aston, PA
Analog Devices, Norwood, MA

Our general funding during this period came from the Air Force URI program and the NHMFL.

The pulsed field apparatus will be used to study novel superconducting systems and magnetic materials down to 0.360 K in conjunction with our existing cryogenic apparatus.

Regards from the the group: Dave Howe, Sergei Ivanov, Chuck Mielke, Tom Coffey and Chuck Agosta

---