IEEE Spectrum November, 2014 - 60

filled Dewar vessel and an RF amplifier in a small aluminum
box. On New Year's Eve, they tested it. Cohen later offered
this account: "Finally we were ready to look at the easiest bio-
magnetic signal: the signal from the human heart, because it
was large and regular. Jim stripped down to his shorts, and
it was his heart that we first looked at. The resulting MCG
[magnetocardiogram] signal exceeded my best expectations.
It was as clear as a conventional ECG [electrocardiogram], and
several orders of magnitude better than the MCG from a coil
detector. Although I didn't realize it, a new era had arrived
in biomagnetism."
Cohen likened his own effort with the copper coils to "try-
ing to explore a new continent...using a rowboat." The SQUID,
he said, gave him "a powerboat."
Cohen and Zimmerman's experiment
was the first use of a SQUID on a living
subject. Though the apparatus wasn't
ready for clinical use, the results turned
both men into true believers about the
medical applications of the SQUID.
Cohen next began using SQUIDs for
measuring the tiny magnetic fields in
the brain-even trickier to detect than
those from the heart. Meanwhile, in San
Diego, SHE shifted its focus to design-
ing SQUIDs specifically for medical use;
eventually, the company changed its
COME TO MIT FOR A SEMESTER
name to Biomagnetic Technologies and
sold SQUIDs for performing magneto-
ADVANCED STUDY PROGRAM
encephalograms, or MEGs.
Enroll in regular MIT courses through this non-matriculating, nonAround the time of his visit with
degree program. Participate on a full or part-time basis for one or more
Cohen, Zimmerman was offered a job at
semesters. Earn grades, MIT credit, and a certificate of completion.
the National Bureau of Standards (now
BRING MIT TO YOU
the National Institute of Standards and
Technology) at its facility in Boulder, Colo.
ONLINE X PROGRAMS
He resigned from SHE due to a possible
Interact with professionals from around the world without disrupting
conflict of interest, but he never let up
your work-life balance. Online courses designed to advance your
on making the SQUID more portable and
career at your own pace with a flexible schedule that meets the
responsive. He also helped create the first
needs of a global workforce.
arrays of SQUIDs, for taking measure-
Tackling the Challenges of Big Data
ments over a wider area. With Martin
Designed for engineers, technical managers, and entrepreneurs
Reite at the Colorado Health Sciences
looking to understand new Big Data technologies and concepts to
Center, for instance, he designed a SQUID
apply in their work, and to gain perspective on current trends and
array for MEGs; Reite used the apparatus
future capabilities. Two new sessions: Nov. 4, 2014 & Feb. 3, 2015.
to study the brain's auditory response.
If Zimmerman's work on SQUIDs was
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groundbreaking, his keen interest in
refrigeration was equally important. The
lack of good cooling technology, he real-
ized,
was one of the main things holding
To learn more about what MIT Professional Education
back
the
adoption of the SQUID in indus-
can offer you and your company, visit us today at:
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http://professionaleducation.mit.edu/ieee2014
commercial refrigerators were too big
and, worse, contained magnetic com-
ponents, which could overwhelm the
faint signals the SQUID was supposed to
detect. Zimmerman spent more than a

In late 1969, Zimmerman was con-
tacted by physicist David Cohen, who had become intrigued by
biomagnetism and was experimenting with measuring electri-
cal fields of the human heart and brain using copper coils. To
do this, Cohen built a large magnetically shielded room and
took hundreds of passes of each subject, using signal averag-
ing to eke out a decent signal-to-noise ratio. "I badly needed
a better detector and had heard about Zimmerman and his
SQUID," Cohen recently recalled.
In late December 1969, Zimmerman visited the Francis
Bitter National Magnet Laboratory at MIT to meet with Cohen.
Zimmerman had with him a portable SQUID demonstrator
that he'd built; it consisted of an RF SQUID in a small helium-
co nti n u e d f ro m pag e 4 4 |

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Table of Contents for the Digital Edition of IEEE Spectrum November, 2014