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Technical University Braunsweig, Germany
Researchers at the Institut fur Hochfrequenztechnik have produced high-Tc SQUIDs with noise
level of (6 ~ 7) x 10'3 Fq/ with a l//knee of 5 Hz. A magnetometer was constructed with one of
these devices and used to detect the timing signals from an electromechanical clock.
Giessen University, Germany
In the past, they have collaborate with Phillips, Hamburg, along with some interaction with
Domier.
CNR Rome, Italy
Constructed 9-channel gradiometer system with noise levels of 20 fT/. With technology learned at
NBS, Boulder, their dc SQUIDs had En = 8.5 x 10'31 Joule/Hz. The CNR works closely with
Elettronica S.p.A. They have a major project to develop new SQUID sensors for imaging neural
and cardiac activity among other biomagnetic diagnostic techniques. This has led to a 28-channel
neuromagnetometer system. The dc SQUIDs (currently supplied by IBM) connect to 17 axial
gradiometers and
1 1 planar gradiometers. System performance will be announced at the 1990
Applied Superconductivity Conference.
Warsaw Pact
Most groups fall into the University and Government laboratory category. However there are
three groups marketing SQUID components and are so designated.
Soviet
The Soviet Union has had a long history of activity in SQUID devices. They are especially strong
in the theoretical understanding of the quantum mechanical nature of SQUID devices. A list of
references to Soviet activity can be found in the article “Superconductor Electronics: New
Prospects” by Likharev. There is also significant Soviet activity in high temperature
superconductivity including high-Tc SQUIDs. The Joint Institute for Nuclear Research in Dubna
is purported to be manufacturing commercial grade SQUID electronics.
Institute of Radioengineering & Electronics, Moscow
In 1987, the Institute was using a single channel SQUID magnetometer with a noise level of
10 fT/ in an unshielded urban environment. Support equipment include a computer for initial data
processing and dynamic image processing. By the middle of 1989, the Institute had constructed a
high-Tc SQUID and successfully took MCG (cardiac) data. The SQUID operated at 77 K with a
noise level ~5,000 fT/.
Edward Godik, Institute director said (at the 1989 New York Biomagnetism Conference) that the
magnetic imaging group has completed their dc SQUID electronics. They are in the process of
building a multi-channel system and would like to work with a commercial company on a 50/50
basis. Dr. Matlashov gave the following performance for their dc SQUID:
= 5 x 10'
Joule/Hz, Linput = 0.6 mH, with the 10" knee at 0.2 Hz. With a detection coil (gradiometer order
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not mentioned) attached, the intrinsic field noise was 8 fT/ with actual values being 20 fT/. The
gradiometer was mechanically balanced to better than 1000 ppm and electronic balancing with an
IBM PC/AT (clone) was used to improve rejection of uniform fields to better than 10 ppm. Since
then, the Institute has fabricated Nb-A10x-Nb dc SQUIDs with flux resolution of
~2 x 10"6 Fo/. Configured as a gradiometer, magnetic field sensitivities of 10 fT/ have been
achieved.
Kurchatov Institute of Atomic Energy, Moscow
Their main interest is in MEG. The Kurchatov facility is a new two story wooden building. Inside
is an aluminum eddy current (rf) shielded room 5 cm thick. Their magnetometer is an asymmetric
first derivative gradiometer. They are using both Zimmerman style two-hole sensors and
apparently also have a BTi rf SQUID sensor. They have constructed SQUID sensors of their own
design. These devices are were developed in am associated electronics institute (perhaps the
Institute of Radioengineering & Electronics in Moscow). Electronic balancing has been used to
suppress low frequency noise by 40 dB.
In the past, researchers from the Institute (Ozhogin, Shabonov, etc.) have worked with the 7-
channel biomagnetometer system at Helsinki that uses IBM dc SQUIDs. Dr. Shabonov feels all
planar devices are the way to go. They participated in aspects of the preliminary design of the
Helsinki 24 channel system. Ozhogin has written a Russian language text on biomagnetism and so
edits a Soviet journal on high temperature superconductivity.
USSR Academy of Sciences
Kholodov et al (Institute of Higher Nervous Activity and Neurophysiology) describe a dc SQUID
magnetometer system with sensitivity of 40 fT/. Other work is described in the proceedings of the
17m International Conference on Low Temperature Physics, Bondarenko et al.
Alexandr M. Gorbach (Institute of Higher Nervous Activity & Neurophysiology) has built an
optically pumped magnetometer for MCG work. Its sensitivity is 100 picoTesla. He has authored
a book (in Russian) on magnetometers. On page 80 is a photo that appears to be that of the BTi
model 601 SQUID biomagnetometer that was diverted to the Soviet Union in 1984.
Joint Institute for Nuclear Research, Dubna
The Joint Institute for Nuclear Research, Dubna, USSR constructed a SQUID with noise levels
less than 50 mF()/. They have recently constructed a rf-biased YBa2Cu307 _ cj SQUID. Operating
at 78 K, the energy sensitivity is 9 x 10'2^ Joule/Hz, with an equivalent field noise of -400 fT/ (f
> 100 Hz). As a gradiometer consisting of two SQUIDs in opposition (9 cm baseline), its
sensitivity is 3,000 fT/meter/ in the white noise region (> 10 Hz). The system has been used for
magnetocardiography. The same group has recently developed a single-hole version with
outstanding properties. Used for magnetocardiography measurements in a single room, the basic
magnetometer has a l//knee at
1 Hz and an ultimate field sensitivity of
~1 15 fT/ (equivalent to 3 x 10'4 Fq/). The radio frequency electronics used were “identical to the
low-temperature SQUID electronics fabricated commercially by the Physics Facilities Division of
the JINR.”
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Ukrainian Academy of Sciences
Early work in the 1970’s by the Physicotechnical Institute for Low Temperatures led to a
<10'3 Fq/ thin-film SQUID. This Institute has published many papers of SQUID magnetometers,
including papers on biomagnetism and geophysical applications.
The Institute of Cybernetics reported on a niobium tunnel junction device with noise levels of
30 mF()/. More recently, they have constructed a YBa2Cu3(>7 _ci high-Tc SQUID operating at
77K with Ejsj < 10'28 Joule/Hz. The Institute is actively promoting its technology to interested
parties in view of a potential joint effort in scientific research, manufacturing or marketing. In
particular, they describe a high-Tc rf SQUID magnetometer with a magnetic field sensitivity of
400 - 800 fT/ at 77 K. Its intrinsic noise level (0.1 - 150 Hz) is stated to be < 10 fT/
( 200 mFo/). The accompanying dewar claims to have a >30 day hold time. The rf SQUID
electronics offer a 120 dB dynamic range. The Institute also offers YBCO powders and precursor
materials for sale.
Moscow State University
The department of Physics has been active in constructing SQUID sensors for at least the last five
years producing both rf and dc SQUIDs operating at the 10'31 Joule/Hz level.
Sektion Physik, Friedrick-Schiller-Universitt Jena — Manufacturer, Germany
The group leader, Professor Albrecht, has more than a decades experience in constructing thin-
film tunnel-junction (dc) SQUIDs with noise levels less than 100 mF()/ (< 60 fT/).
Using a planar dc thin film SQUID with an integrated transformer connected to a second order
gradiometer, sensitivities of 20 fT/ have been achieved. The device is a multiloop thin film tunnel
junction (Nb-NbOx-Pb) dc SQUID with an input impedance of 0.7 mH, 3.8 x 10~2 A/Fq and a
flux noise of 1x10'^ Fq/. The junction dimensions were 2.6 m x 2.6 m. The latest SQUID sensor
from the Jena group, the model “UJ 111” has an energy sensitivity of 2.9 x
1 0'31 Joule/Hz
(2 x
10'6 Fq/ into a 0.9 mH input coil), note: these performance figures are comparable with the best
dc SQUID commercially available in the West. Their construction is felt to be superior (in terms
of reliability) to those supplied to Helsinki by IBM.
Albrecht’s group has been supplying most of eastern bloc with niobium and NbN Josephson
junctions and is now selling these devices commercially. Customers outside the Warsaw Pact
include Helsinki University of Technology, Tampere University and Wurtzberg University.
According to Prof. Williamson, the Jena devices have equivalent performances to BTi’s dc
SQUIDs. These SQUIDs have been used to construct a 5-channel biomagnetometer with
mechanical balance of 100 ppm and field noise of 20 fT/.
Czechoslovakia
Czechoslovakian Academy of Sciences, Prague— Potential Manufacturer
The Physics Institute constructed a 440 MHz rf SQUID with a sensitivity of 2.6 x 10’29
Joule/Hz. A review paper by M. Odehnal gives extensive references to work in Warsaw Pact
countries.
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The Slovak Academy of Sciences have advertised a laboratory rf SQUID system for sale that is
comparable to commercially available rf SQUID systems. No customers names are known.
Institute of Physics, Prague
Incorporated SQUIDs into a susceptometer and built a three-axis geophysical magnetometer with
a sensitivity better than 100 fT/.
Slovak Academy of Sciences, Bratislava
The Institute of Electrical Engineering, Electro-Physical Research Centre is known to be
conducting theoretical, experimental and applied research on the JoSephson effect and
superconducting electronics.
Poland
Polish Academy of Sciences, Wroclaw, Poland— Potential Manufacturer
Early activity at the Institute of Physics is described in articles in the Review of Scientific
Instruments. These devices may be in use in a hospital for biomagnetic applications. The Instytut
Niskich Temperatur, has advertised a laboratory rf SQUID system for sale (with a digital
fluxcounting accessory). Their early SQUID sensors were based on the S.H.E. Corp. point
contact model TSQ SQUID sensor. They have coated a point contact SQUID with NbN, giving
the sensor the potential to operate above 10 K.
Finland
Helsinki University of Technology, Helsinki, Finland— Potential Manufacturer
In 1976, Professor Olli Lounasmaa’s group constructed 7-channel gradiometer for
magnetoencephalography. The system uses IBM dc SQUIDs (supplied by C. Tesche, IBM,
Yorktown Heights) with a sensitivity of 5 mF()/ and extremely low
1 If noise. These all thin-film
devices are considered to be the world’s best. Operating in the Helsinki magnetically shielded
room, system performance is 5~6 fT/. The dc SQUID electronics were designed by HUT
personnel. With a dynamic range > 100 dB (1 Fq maximum), the electronics features two ranges
and three different slew rates. An impedance damping circuit allow the first derivative coils to
operate at full system sensitivity. It should be noted that there has been Soviet access to this
system and others in the past.
The Helsinki group (headed by Professor Lounasmaa) completed a 24 channel system in 1989
with Soviet (Drs. Ozhogin and Shabonov of the Kurchatov Institute of Atomic Energy, among
others) participated in the early stages of the system design. The 24 channel system uses planar dc
SQUIDs (supplied by IBM after Soviet involvement ceased) integrated with planar orthogonal
planar first derivative detection coils. It is serving as a test bed for a 100 channel planar
gradiometer system. The 100 channel system is intended to be commercially available. At this
point, IBM is considering extending their collaboration with the Finns and supplying dc SQUIDs
for the first 100 channel system.
It is unclear whether or not IBM would be involved in any
follow-on systems.
The Finns have the capability to produce their own chips. Their current SQUID chip is a single
large wafer with two planar first-order gradiometers oriented perpendicularly to each other
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