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The 755R uses DC SQUID (Superconducting
Quantum Interference Detector) magnetic field sensors to measure rock magnetism.
The SQUIDS measure the current induced in three orthogonal pick-up coils
within the cylindrical unit, with a noise level of less than 10-9
emu (10-7 A/m for a 10cc volume rock). Presently, we are measuring
1 inch diameter drill cores, 1 inch and 0.5 inch long, as well as 1cc cubic
sediment samples with this system. The measurement routines are PC-driven
with comprehensive software.
The Model 2900 Micromag AGM is a highly
sensitive measurement system, capable of measuring hysteresis properties
on a wide range of sample types and strengths. It utilizes an alternating
gradient field to exert a force on a sample that results in a deflection
of the sample within the field. This deflection is measured by a pizeoelectric
sensing element mounted on the probe arm, and signals are carried to a
PC connected to the magnetometer. Analysis is done through a comprehensive
software package. Magnetic properties such as coercivity, coercivity of
remanence, saturation magnetization and magnetization of remanence are
routinely measured by students working for the Paleomagnetic Research Group.
Pictured here is the P1 (fine) probe
inside the AGM with a typical sample on the probe's stage. The stage sits
between two electromagnets housed in the magnetometer assembly. The pizeoelectric
sensing element is situated at the top of the probe. Typical samples include
carbonate sediments from the Eastern Equitorial Pacific (pictured here),
sandstones and basalts from the High Canadian Arctic, and basalts from
the Hawaiian-Emperor Chain.
The fluxgate magnetometer allows for the
measurement of magnetic fields over a wide range of values, along three
orthogonal directions with a compact probe. Four selectable measurement
ranges (1, 10, 100, 1000 mOe) are available. Fields up to 1300 mOe can
be measured before probe saturation. Resolution is on the order of 10-6
Oe (0.1 gamma).
The
KLY-4S
Spinner Kappabridge is the world's most sensitive commercially available
laboratory instrument for measuring anisotropy of magnetic susceptibility
(AMS) as well as bulk susceptibilty in weak variable magnetic fields. The
KLY-4S Kappabridge consists of the pick-up unit and control unit connected
with a PC computer via RS-232 interface. The instrument represents a super-precise
fully automatic inductivity bridge. It is equipped with automatic zeroing
system and automatic compensation of the thermal drift of the bridge unbalance
as well as automatic switching of appropriate measuring range. The measuring
coil is designed as 6th-order compensated solenoid with an outstanding
field homogeneity. The digital part of the instrument is based on microelectronic
components, with the microprocessor controlling all the Kappabridge functions.
The KLY-4S sensitivity is 2 x 10-8 SI, measuring field range
is 3 to 450 A/m.
The Model TD-48 Thermal Demagnetizer
is a large-capacity thermal specimen demagnetizer. Special shielding permits
cooling of one batch of specimens while a second batch is heating. The
cooling chamber (forefront of the picture) has additional shields that
limit the maximum internal field to less than 10 gammas. The sample boat
has two titanium trays capable of holding three rows of various sized samples.
Ceramic endcaps on the sample boat fit snuggly in the vestibules of the
ends of the oven chambers, eliminating the need for oven doors. Total demagnitization
(heating and cooling) times range from 1 hour to 2.5 hours, depending on
the temperature of demagnetization desired. It is possible to demagnetize
samples at a temperature range between 50 - 700 degrees C.
The SI-4 AF Demagnetizer is capable of alternating
field demagnetization of samples, as well as ARM and IRM generation. The
unit is controlled by a front panel logic keyboard. Demagnetization steps
can be set by the user to a desired value. The AC coil shield is a 3 nested
layer shield that limits the maximum internal field to less than 10 nT
when oriented E-W in the ambient geomagnetic field.