RESEARCH
ABOVE. The world's most powerful electromagnet, housed i n t h e l o w temperature laboratory at thé University of California, n o w operates in the 100,000 gauss region. Designed by William F . G i a u q u e , N o b e l Laureate in chemistry, a n d D a v i d N. L y o n , both of t h e University of California, the magnet will b e used for new experiments near absolute zero. Here, the m a g n e t is seen a t the completion of winding of the coil. The spacers provide annular space for cooling fluid. RIGHT. Giauque ( left) and Lyon inspect the m a g n e t housed in t h e large vertical tube between the two horizontal pipes. T h e eight-inch pipes are copper a n d carry the coolant in below, out above. Coolant pipes also c a r r y direct current for t h e magnet and are electrically insulated from the housing near trie bellows joints. C u r r e n t then goes to magnet through b u s bars running from pipes to lower part of magnet housing. T h e area shown is in the laboratory's sub-basement. The working floor for the electromagnet is directly a b o v e sub-basemen) 1 :
Closer to Nothing Most powerful electromagnet allows closer a p proach to absolute zero, opens new fields of research A HE WORLD'S most powerful, continuously operating electromagnet is now operating at the University of California's Berkeley campus. The magnet, located in the laboratory of Nobel L a u r e a t e William F. G i a u q u e , will b e used to attack problems in lowtemperature physical chemistry. Physically, t h e m a g n e t is small comp a r e d with the giants in the cyclotrons a n d bevatrons, but it is big in other ways. It is big in the magnetic field it p r o d u c e s , and it is even bigger in its potential for fundamental research. T h e magnet h a s a copper spiral b a n d 3 / 4 inch wide and 1 / 4 inch thick. Externally, it is about 2 feet long and 1 5 inches in diameter. The magnet will produce a field of 96,700 gauss which is uniform t o within 0.1 Cr over a working volume of some 3 0 cubic inches. Circulating 2200 gallons of kerosene per minute«removes heat generated by the 6000 kvv. input. '• Absolute Z e r o . In the sub-base26
C&EN
JULY
2 8,
1958
ment of Giauque's n e w $2 million laboratory, the magnet, sealed in a vault and blanketed with inert gas, will b e used to produce' temperatures a p proaching absolute zero by the technique of adiabatic demagnetization. A paramagnetic salt, for example, can b e brought to liquid helium temperature and then, by boiling off helium u n d e r vacuum, to within a degree or so of absolute zero. With most of the molecules' vibrational motion thus removed, only t h e magnetic disorder remains. When t h e magnet is turned on, the ordering gives off heat which is removed by the boiling helium. Then, b y thermally insulating the salt from the helium a n d turning off the magnet, the returning disorder cools the salt further to within a fraction of a degree of absolute zero. And the more powerful the electromagnet is, t h e closer the approach. • V e r s a t i l e . What fields will use this powerful new tool? G i a u q u e himself
feels that t h e possibilities are almost endless. Only a few of the potentialities can be foreseen, of course, but among them will b e an extension of Giauque's work on entropy measurement. Vibratory energy and the magnetic disorder can b e removed separately; thus accurate entropy determinations at low temperatures can be m a d e . Another project slated for early work is t h e exploration of nuclear alignment of radioéléments. Glenn T. Seaborg's chemistry g r o u p in the University's Radiation Laboratory would like t o answer the question: From what part (magnetically speaking) of the radioactive nucleus do the particles emerge? With a high, uniform magnetic field and low temperature, the nuclei c a n be aligned so that the geometry of particle emission can be studied. As the first magnet goes into operation, Giauque and his staff already have plans for adding one or two more magnets to extend the usefulness of the laboratory a n d to increase the volume of work that can be undertaken. For Giauque's laboratory will not only carry out its own research program, b u t will undertake work for other research groups.
