 R
& D |
|
| Biomagnetism | |
| Development
of babySQUID® for Neonatal Brain Assessment -NIH |
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| HTS
Ferritometer® -NIH |
|
| Low
Cost Cryosusceptometer -NIH |
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| Intestinal
Ischemica SQUID instrumentation - NIH |
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| Developing
Instrumentation for Fetal Cardiac Monitoring- NIH |
|
| Simultaneous
Fetal Echocardiography and Magnetocardiography -NIH |
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| Transvaginal
Probe for Fetal Magnetocardiography -NIH |
|
| SQUID-Controlled
Noise Reduction Coils for Fetal Magnetocardiography -NIH |
|
| Inverted
SQUID Microscope for Neuroscience Research -NIH |
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| Geomagnetism and UXO (Unexploded Ordenance) | |
| UXO
instrumentation - ONR |
|
| Pipeline
assessment-GRI |
|
| Non-Destructive Test and Evaluation | |
| Airframe
Scanner -NASA |
|
| SQUID
Array for Rate of Hidden Corrosion in Aging Aircraft -AFOSR |
|
| Electromagnetic Sensing | |
| Photonic
Band Gap (Microwave) |
|
| Microwave
Near Field Measurements |
|
| Optical
Magnetometer Operating in Earth's Field |
|
| Other R&D | |
| Mixed
Stage Cryocooler |
|
| Rack
Mounted Cryogenic Platform |
|
| Spray
cooler 77K |
|
| Cryocooled
SQUID sensors |
|
| Consulting Services | |
Biomagnetism R&D
Development of babySQUID® for Neonatal Brain Assessment
Detection of cortical function in newborns is needed for clinical intervention
in the early stages of neurological disorders, before external signs appear
and the conditions develop and worsen. Identifying how infants learn is
of interest to many sectors of society, but such studies rely heavily
on behavioral analyses. Having a direct measure of cortical activity would
provide precise information on the dynamic response in the brain during
learning processes.
babySQUID® showing patient, bed and optical mapping system
Under NIH SBIR funding (SBIR grant 5R44NS038806-04), Tristan developed
a novel, high-resolution magnetoencephalography (MEG) system, called babySQUID®,
for evaluating neurological impairments of preterm and term babies. This
is a portable, non-invasive MEG system that can be used next to the bedside
of any neonatal care unit without a cumbersome magnetically shielded room.
The system is the size and shape of an examination table. Unprecedented
spatial resolution and sensitivity was provided by a closely spaced array
of superconducting MEG sensors housed 6 mm below the outer surface of
the headrest. Additional details of babySQUID® can be found at
http://www.tristantech.com/prod_baby.html
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HTS Ferritometer®
In conjunction with Columbia University's Presbyterian Hospital, the HTS
Ferritometer® program funded by the NIH under an R01 grant (R01 DK57209/CFRA#93849
subgrant #1) to develop a HTS SQUID-based replacement for Tristan's LTS
Ferritometer® (http://www.tristantech.com/prod_biomagnet_liver_fe.html).
A HTS SQUID sensor was coupled to a detection coil fashioned from a HTS
YBCO superconducting film deposited on a flexible substrate. The magnetic,
necessary for applying a mT strength field to the liver, was a NdFeB (neodynium-iron-boron)
permanent magnet. Clinical trials of the prototype system are underway
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Low Cost Cryosusceptometer
In conjunction with Case Western Reserve University and Children's Hospital
in Oakland, CA (CHO), and funded by the NIH under an SBIR grant (2R44
DK066736-02), the low-cost cryosusceptometer program eliminated the use
of SQUID sensors, replacing them with a proprietary magnetic sensor. Closed
cycle refrigeration is used to eliminate the need for transfer of cryogenic
liquids, reducing operating costs and improving ease-of-use.
{Low-cost_Cryosus.jpg}
Clinical trials of the prototype system (including sensor system, closed
cycle refrigerator, cryostat gantry, patient bed, computer control and
analysis system) are about to begin. Measurements from the low-cost cryosusceptometer
will be compared to CHO's LTS Ferritometer® (http://www.childrenshospitaloakland.org/hedco.html).
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Instrumentation for detection of Intestinal Ischemica
Intestinal ischemia is difficult to diagnose and usually fatal. Other
less serious intestinal disorders, such as Crohn's disease, ulcerative
colitis, and irritable bowel are also difficult to diagnose. Previous
work on animals at Vanderbilt University has shown that electrical activity
in the small intestine is highly sensitive to changes in arterial oxygen
delivery and arterial blood supply. These changes are large and occur
within minutes of creation of the ischemic bowel.
{Array2lowres.jpg} {gutSQUID patient.jpg}
Detection coils set showing axial and vector channels Patient measurement.
Preliminary magnetic measurements were made on normal human subjects using
a novel, superconducting vector magnetometer that was developed during
this project. The resultant system was delivered to Dr. Richards at Vanderbilt
University Medical School. Additional information on the resultant research
can be found at http://www.vanderbilt.edu/biomag/.
This work has shown that non-invasive measurements can be made of electrical
activity in the intestine and that the magnetic signal is consistent with
published data taken electrically. This program was funded by the NIH
under a SBIR grant (7R44 DK049435-04).
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Developing Instrumentation for Fetal Cardiac Monitoring
There is a strong need to assess the physiological development of the
fetus, as more pre- and full-term babies survive with possible disorders.
In conjunction with the University of Wisconsin and the Medical College
of Wisconsin, the program was funded by the NIH under a SBIR grant (1
R43 HD043542 -01). Tristan evaluated the feasibility of developing a new,
non-invasive fetal magnetocardiography (fMCG) sensor, based on high temperature
superconductors (HTS). This involved the construction of a proof-of-principle
HTS axial gradiometer fMCG system using electronic gradiometers. Measurements
in a magnetically shielded room showed sufficient sensitivity for fMCG
measurements. As part of the program, HTS planar gradiometers were investigated
and found to allow real-time unshielded measurements of adult MCG's.
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Simultaneous Fetal Electrocardiography and Magnetocardiography
Electrophysiological and mechanical interactions in the fetus are largely
unstudied. There is an established need to enhance the current echocardiography/Doppler
capabilities of recognizing the fetus at risk of life threatening cardiac
complications. In conjunction with the University of Wisconsin and the
Medical College of Wisconsin, this program is funded by the NIH under
a SBIR grant (12R44HL082017-02), this program is developing an fMCG vector
gradiometer instrument specifically designed for combined use with echocardiography
for the characterization of the intrauterine clinical condition of fetuses
with life-threatening arrhythmias, acquired heart failure, and structural
congenital heart disease. Direct simultaneous comparison of fetal magnetocardiography
using Superconducting Quantum Interference Device (SQUID) magnetometry
and Doppler will allow, for the first time, assessment of electromechanical
disturbances associated with heart failure and severe arrhythmia. This
instrument will directly address the fetal cardiac disorders that effect
about 1-3% of all pregnancies.
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Transvaginal Probe for Fetal Magnetocardiography
Extending the Instrumentation for Fetal Cardiac Monitoring and Simultaneous
Fetal Electrocardiography and Magnetocardiography R&D efforts, and
in conjunction with the University of Wisconsin and the Medical College
of Wisconsin, this program (funded by the NIH under SBIR grant 1R43HD055091-01),
is aimed at developing an instrument for transvaginal fetal cardiac and
brain electromagnetic activity at gestations younger than what can be
achieved using present technology of transabdomenal fetal signal recording.
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SQUID-Controlled Noise Reduction Coils for Fetal Magnetocardiography
The infrastructure requirements (cost, weight, size, cramped interior
spaces, etc,) for magnetically shielded rooms (MSRs) have inhibited the
diffusion of biomagnetic instrumentation. Under NIH SBIR funding (1 R43
HD45106 -01), Tristan, in conjunction with Wisconsin researchers, developed
a novel noise cancellation system utilizing Helmholtz coils and proprietary
feedback electronics to achieve 70 dB reduction of powerline frequencies.
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Inverted SQUID Microscope for Neuroscience Research
This program was funded by the NIH under a SBIR grant (2 R44 NS046964-02)
is to develop a prototype inverted SQUID microscope for neuroscience research.
The signal levels are expected to be much weaker (100-500 fT/ÖHz)
than signals in the area of non-destructive evaluation (> 1 pT) where
SQUID microscopes have been used previously. The prototype system is an
8-channel magnetometer-SQUID sensory array, each magnetometer being about
0.6 mm in diameter with a field sensitivity around 70 fT/ÖHz or better
with the detection coils at a distance of 200 µm away from the neurons
and glial cells to be studied. The microscope is similar to an inverted
optical microscope except the objective is replaced by an array of superconducting
miniature magnetic field sensing coils. Tristan's cryocooled liquid ballast
refrigeration technology (link to cryocooled SQUID sensors) is used to
avoid the need for daily cryogen transfers.
{Inverted_Microscope.jpg}
Other applications for the inverted microscope are (1) electrical currents
from single neurons and glial cells in culture, (2) efficiency of bonding
of antigens and magnetically tagged antibodies (immunoassay), and (3)
movements and conformational changes of a small number of magnetically
tagged molecules in a cell for studying signaling pathways. The proposed
SQUID microscope should be useful in both academic setting and industry
for understanding the electrophysiology of small cells that are difficult
to study with electrodes, for drug discovery and for studying second-messenger
systems.
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Geomagnetism & UXO
UXO instrumentation
In conjunction with Blackhawk Geometrics, Oak Ridge National Laboratory
and Battelle (funded by the U.S. Naval Surface Warfare Center contract
N00174-98-C-0026 and subsequent contracts), Tristan developed a HTS SQUID
magnetometer system for standoff detection and classification of surface
and buried unexploded ordinance (UXO). The 8-element tensor system
http://www.tristantech.com/prod_tensor.html was used in conjunction with
a transient electromagnetic field generator to perform TEM measurements
on various UXO objects. This work is being extended to placement on an
airborne platform
{UXO_data.jpg}
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Pipeline assessment
This program, funded by the Gas Research Institute, was to design a SQUID-based
Magnetic Telescope consisting of a superconducting source coil encircling
a superconductive pickup loop that inductively couples magnetic flux to
a SQUID sensor. There are several advantages to using superconducting
technology for inspection of buried pipelines. The magnetic field of a
supercurrent oscillating at several hertz in a source coil penetrates
the overburden to detect defects in a pipe wall. The generated magnetic
field can penetrate to depths in excess of 6 feet to illuminate defects
in buried pipelines. In addition, defects can be detected in the entire
circumference of the pipe, i.e. in the under side, and not just in the
areas near the detection equipment. This technique can precisely locate
flaws for subsequent excavation and repair. Changes in wall thickness
and diameter, as well as bends and plug valves, are not deterrent factors
for a Magnetic Telescope.
{Mag_Telescope.jpg}
Under separate funding from a major East Coast Utility, Tristan developed
a magnetic inspection system for liquefied natural gas (LNG) piping to
distinguish between ferrous and non-ferrous bolts situated beneath thick
insulation layers.
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Non-Destructive Test and Evaluation
Quantitative Nondestructive Evaluation of Aerostructures Using New High
Temperature SQUID Sensors
The goal of this NASA funded subcontract from Magnesensors (San Diego,
CA) was to develop a new, portable NDE instrumentation capable of detecting
deep level flaws in multi-layer aerostructures. The system integrated
the latest technology for operating HTS in an unshielded environment with
some of the most advanced eddy current techniques to produce a new, portable
NDE instrument for scanning airframes for hidden defects. Deliverables
included a unique compact liquid nitrogen dewar capable of cooling a HTS
SQUID sensor array while oriented in any (including inverted) orientation,
a remotely operable, non-magnetic scanning arm and a data acquisition
system for remote operation of all aspects of the scanning system. The
system also included a horizontal (Bx & By) field generator.
{NASA_scanner.jpg}
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SQUID Array for Measurements of Hidden Corrosion in Aging Aircraft
In conjunction with Vanderbilt University and under funding by the Air
Force Office of Scientific Research under a STTR grant (F456220-00-C0006),
Tristan developed a new laboratory instrument that that incorporated a
2-dimensional array of SQUID magnetometers suitable for quantifying the
rate at which various forms of corrosion damage accumulate in a range
of aerospace structures. This technique will allow determination of instantaneous
rates of hidden corrosion in aluminum aerospace structures, such as crevice
corrosion in an aircraft lap joint or exfoliation corrosion in the midplane
of a thick wing plank. The system has greatly increased "scanning"
speeds for more precise spatio-temporal measurements.
{AFOSR_Corrosion.jpg}
The design incorporates important technical innovations, including the
use of fractional-turn SQUID sensors, improved scanning technology, and
advanced analysis software. The instrument incorporates a 16-channel SQUID
magnetometer system, an 8-element tensor array for noise reduction, a
magnetic shield and scanning stage, and an environmental controlled corrosion
cell system. The metrics developed allows the imaging of the "instantaneous"
level of magnetic activity, as well as cumulative magnetic activity, indicating
regions of high activity. This instrument was designed to provide data
on hidden corrosion rates that will reduce the probability of hidden corrosion
contributing to the failure of a structurally significant element. Its
applications will be in inspection planning and maintenance, cost reduction,
and increased aircraft safety and availability.
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Electromagnetic Sensing
Microwave Frequency Photonic Band Gap Resonator
This program, funded by the U.S Department of Defense, developed a high
Q, low phase noise resonator filter based on a Superconducting Photonic
Band Gap Structure. Details of this microwave frequency device can be
found at http://www.tristantech.com/technotes_photo.html .
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Microwave Near Field Measurements
Under DOD SBIR funding (SBIR grant F33615-03-M-5429), Tristan developed
a resonant microwave technique for characterization of the electronic
properties of wide bandgap semiconductors used for RF applications in
the X-band. A 94 GHz Fabry-Perot resonator was used to perform measurements
on a number of substrates and epitaxial wafers with varying growth/processing
parameters. Correlate the DC resistivity and wafer's growth/processing
parameters with the dielectric constant and losses at 94 GHz. SiC substrates
with and without GaN epilayers.
SiC ingot inside the 94 GHz resonator -{SiC_in_SRA.jpg}
2D scan of high resistivity 450 micron thick SiC wafer. Effects due to
edge of sample holder can be seen at corners of scan.
{SiC_data.jpg}
A variable temperature platform, able to accommodate 50 mm diameter, 2
mm thick wafers for high frequency EM measurements in the 25 to 600°C
temperature range was also designed.
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Optical Magnetometer
In conjunction with researchers at Princeton University, a new fT-level
atomic magnetometer technology was developed under US Department of Defense
funding (STTR grant N00014-04-M-0254). The device was a two-channel unshielded
atomic magnetometer that was constructed and tested at Tristan. It demonstrated
sensitivity of 2 pT/rt-Hz while operating in an industrial environment
with noise level as high as 5 nT/rt-Hz. The intrinsic sensitivity level
of the magnetometer constructed at Tristan was equal to 10 fT/rt-Hz. The
major sources of noise were identified and a plan for the next generation
system operating on an airborne platform developed.
[opt_mag_cells.jpg}
Dual Cell Atomic Magnetometer
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Other R&D
Mixed State Cryocoolers
More than a decade ago, Tristan developed the first mixed stage (Gifford-McMahon/Joule-Thomson)
cryocooler that routinely achieved 2 K. The technology developed by Tristan
is now routinely used in the cryocooler industry.
{2K_cooler.JPG}
Rack mounted Cryogenic Platform
The electronic benefits of using cryogenically cooled and/or superconducting
electronics-and 4 K electronics in particular-comes from higher potential
speeds, higher signal to noise and lower thermal noise. Use of cryogenically
cooled and/or superconducting electronics for shipboard, airborne, and
long life stationary applications prohibits the use of liquid cryogens.
In this DoD funded SBIR program, we are in the process of designing and
(in Phase II) constructing a Rack Mounted Cryogenic Platform (RMCP) that
will satisfy the need for packaging of signal transfer hardware for cryogenically
cooled RF receivers and other superconducting electronics (SCE)
Spray Cooler
There are a number of situations (e.g., X-ray crystallography) where it
is desirable to vary the temperature of a sample without direct contact
to the sample. Directing a temperature regulated gas stream at the sample
can accomplish this task. Tristan developed a OEM spray cooler system
for a private customer that provided a wide temperature range with the
ability to rapidly change the sampe temperature.
{cryomech1.jpg}
In the CryoStreamÔ Cryogenic Spray Cooler, clean, dry nitrogen gas
flows through two separate gas flow paths. One path goes through a regulating
valve, through a gas flow meter, and then to the Cooling Unit where the
gas is cooled by a closed-cycle cryocooler. This cold gas then continues
to a separate region inside the vacuum can where the temperature of the
gas can be regulated to any desired temperature between -200 ºC and
+100 ºC. The gas then flows through an insulated, flexible tube to
a nozzle where the cold gas coming exiting the nozzle can be used to cool
(or heat) a sample.
Cryocooled SQUID sensors
A compact 77 K pulse tube refrigerator was used to successfully operate
a HTS SQUID sensor without the need for liquid cryogens.
{A_SQUID_data.jpg}
a) in zero field. -100 dB = 25 fT/ÖHz. b) in Earth's field. -100
dB = 250 fT/ÖHz.
The figure above shows operation of a Tristan model HTM-8 HTS SQUID magnetometer
(50 fT/ÖHz sensitivity) in both zero and 0.5 gauss (Earth's field)
environments. The upper trace in both figures is that of the SQUID magnetometer
measured in a liquid nitrogen bath. The lower trace is the same SQUID
connected to the 77 K pulse tube. As can be seen, for all frequencies
above 20 Hz, Tristan's implementation of direct cryocooling of a HTS SQUID
sensor introduces no magnetic noise. Even at 1 Hz, the induced field noise
from the cryocooler is only a factor of 10 above SQUID noise. Tristan
is continuing its efforts to improve <20 Hz performance. This technology
is being used in Tristan's {put in link to} Low Cost Cryosusceptometer.
Tristan has also developed a series of cryocooled LTS SQUID magnetometers
using a 1/10th watt Gifford-MacMahon cycle refrigeration. The GM cryocooler
first liquefies helium gas and then sufficient refrigeration to keep the
helium liquefied during system operation. Depending on the configuration
of the detection coils, the design allows measurements to be taken at
or near SQUID sensitivity without the cryocooler inducing magnetic or
vibrational noise.
{DRM300.jpg}
For ultra-sensitive measurements, the cryocooler can be turned off. There
is sufficient liquid helium ballast to operate the SQUID magnetometer
system for more than a day without restarting the cryocooler. This technology
is used both in Tristan's model DRM-300 rock magnetometer (http://www.tristantech.com/pdf/DRM-300datasheetv1.pdf)
and a series of OEM susceptometers.
Consulting
Tristan has performed contract R&D for a number of private companies
and research organizations, both in the United States and in foreign countries
in areas ranging from underground detection and corrosion analyses to
custom biomedical products. Contact Tristan for details regarding assistance
in the areas of cryogenics, magnetic sensing and electronics.
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Internal R&D
Since its original founding in 1991, Tristan and its key personnel have
produced a number of custom measurement systems for a variety of applications.
Some of them are listed here:
· Multiple single- and multi-channel SQUID magnetometers for NDE
and paleoarcheology use. These are state-of-the-art systems, some with
spatial resolutions approaching 1 µm.
· High Speed Data Acquisition System for SQUID electronics. These
electronics, developed for a major telecom supplier offered > 100 kSample/second
acquisition of 24 bit words for a large (? 70 channel) SQUID array. The
data acquisition system had the capability of storing over ¼ terabyte
of data.
· A six-channel system for Vanderbilt University for general
purpose NDE studies. Comprised of a magnetometer, dewar, electronics,
software and multiple magnets, this system has extremely high sensitivity
(10-14 tesla) and sub-mm resolution.
· A three-channel Superconducting (SQUID) NDE system for use
by a large Japanese steel company, comprising magnetometer probe,
dewar, superconducting magnets, custom electronics, and custom software.
Using a welding robot, this compact system is scanned over samples.
· A dual-channel magnetometer system for use by a private company
to study materials for nuclear-fuel rod integrity. The package includes
a magnetometer probe, dewar, computer controlled sample scanner, electronics
and software.
· A compact (12") six-channel high sensitivity susceptometer
capable of generating tesla fields and operating in both vertical and
horizontal orientations. The ultra-compact system, when attached to the
end of a robot arm, is used by a large Japanese nuclear reactor inspection
company for scanning the interior of nuclear pressure vessels.
{TeaPot.jpg}
· The first commercial scanning magnetic microscope (SMM-1000)
to study small electronic circuits and material samples. This comprised
a dewar, cryogenic sample handling stage, magnetometer, custom software,
vacuum system, and custom electronics. It is comparable to a SEM in complexity.
Nine detection coils were fabricated in a linear array with 100 µm
coil separation. Spatial resolution was at the µm level.
{1000_system.jpg}
· A DC and AC susceptibility variable temperature and field
platform. Twelve systems were made. These systems integrated SQUID
magnetometers, sample motion control, sub-mK thermal control from 2 -
350 K, variable applied fields to 17 T and truly user friendly automated
control software. This product demonstrated Tristan's ability to produce
state-of-the-art complex analysis equipment with minimal user requirements.
· An AC susceptibility variable field platform for an OEM customer.
These systems offered closed cycle refrigeration along with automated
sample insertion and measurements. The automated sample handling allowed
up to 96 samples to be measured without human intervention.
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