Optically Pumped Potassium Magnetometer / Gradiometer / VLF
New Generation Potassium System
Terraplus is proud to announce a new generation of Potassium systems --
the highest sensitivity and absolute accuracy optically pumped
magnetometers available. The new GSMP-40 system extends these
characteristics to the next generation of even higher performance
The upgraded v6.0 system is the highest sensitivity and absolute
accuracy magnetometer / gradiometer available. It is designed for
specialized mobile and stationary applications that require the most
demanding survey specifications.
Integrated GPS option (the only system with fully built-in GPS)
20 times per second sampling rate
“Walking” mode for acquisition of high density data
Enhanced memory (increased by 8 times to 4 Mbytes standard and
expandable to 32 Mbytes)
Programmable base station (for scheduling base stations in one of
Optional DGPS real-time and post-time processing (for meter to
sub-meter positioning accuracy)
Rapid data transfer (using the advanced GEMLinkW software)
Internet-based upgrades (from the office or field)
A Different Approach to Optically Pumped
Acquisition of very high resolution and accuracy data. Potassium
systems are substantially more sensitive than other optically pumped
magnetometers / gradiometers.
Location of very weakly magnetic objects or small-size anomalies. This
is a key requirement in applications, such as UXO / EOD and
archeology, where success depends on the ability to map and
characterize the smallest contrasts in magnetic physical properties.
High quality results in areas with high gradients. New small diameter
(40mm) sensors optimize magnetic measurements for sensitivity and
Proven reliability and predictability of results. The natural physics
of Potassium narrow line spectra minimizes heading and orientation
errors to negligible levels.
Minimization of maintenance costs. Once a system is purchased, there
is no need to return it for periodic optical alignment. This
significantly reduces servicing and shipping costs over the lifetime
of an instrument.
Enhanced survey efficiency. The GSMP-40 minimizes operating
requirements, such as warm up and lock times, that slow surveys
Fast response to changing magnetic fields - for moving and stationary
While some of the principles of Terraplus' unique optically pumped
Potassium magnetometer are similar to other optically pumped systems,
the Potassium approach differs significantly in terms of the underlying
physics. The main difference is that Potassium is characterized by
widely-spaced, non-overlapping spectral lines. Spectral lines provide
the basis for measurement in all optically pumped systems. From an
instrumentation perspective, narrow, non-overlapping spectra provide a
number of benefits: Enable the electronics to easily lock on a
pre-defined spectral line. This, in turn, translates into very high
sensitivity and maximum bandwidth (i.e. the “size” of geophysical
features that can be resolved with the system). Minimal heading errors.
These errors occur due to variations in alignment of the sensor head in
the magnetic field. With Potassium errors are less than 0.1 nT. With
other optically pumped systems, the heading error is 1 to 2 nT and can
completely overwhelm the real magnetic response. Reductions in heading
errors also translate into improved gradient measurements. As indicated,
the GSMP-40 does not introduce orientation “noise” into measurements.
The result is that the gradient measurements are very high quality --
both in dynamic and static environments.
Advancing the Field of Potassium Magnetometry
Recent developments with small sensor designs have increased gradient
tolerance by five times while maintaining the industry standard in
sensitivity and absolute accuracy.
Theory of Operation
A typical alkali vapour magnetometer consists of a glass cell containing
an evaporated alkali metal (i.e. alkali atoms).
According to quantum theory, there is a set distribution of valence
electrons within every population of alkali atoms. These electrons
reside in two energy levels as represented by the numbers 1 and 2 in the
Light of a specific wavelength is applied to the vapour cell to excite
electrons from level 2 to 3 only. This process (called polarization)
reduces the number of atoms with electrons at level 2. The result is
that the cell stops absorbing light and turns from opaque to
Electrons at level 3 are not stable and spontaneously decay back to
levels 1 and 2. Eventually, level 1 becomes fully populated and level 2
is fully depopulated.
At this point, RF de-polarization comes into play. Here, we apply RF
power of a wavelength that corresponds to the energy difference between
levels 1 and 2 to move electrons from level 1 back to level 2.
The significance of de-polarization is that the energy difference
between levels 1 and 2 (i.e. the frequency of the RF depolarizing field)
is directly proportional to the magnetic field.
The system detects the fluctuation of light intensity (i.e. modulation)
as the cell becomes opaque and transparent, and measures the
corresponding frequency. The frequency value is then converted to
magnetic field units.
Performance (40 mm sensors)
||< 0.002 nT
||20,000 to 120,000 nT
||Over 13,000 nT/m
||1 to 20 readings / sec
||-20C to +55C
Manual: Coordinates, time, date and reading stored automatically at
minimum 1 / sec and maximum 20 / sec intervals.
Base Station: Time, date and reading at same intervals as manual mode.
Remote Control: Optional remote control using RS-232 interface.
Input / Output: RS-232 or analog (optional) output using 6-pin
Storage - 4Mbytes (# of Readings)
Base Station: 699,050
Walking Mag: 299,593
Console: 223 x 69 x 240mm
Sensor: 145 x 65mm (ext.) cylinder
Electronics Box: 310 x 75 x 90mm
Console: 2.1 kg
Sensor and Electronics Box: 2.4 kg
GSMP-40 console, electronics box, GEMLinkW software, batteries, harness,
charger, sensor with cable, 24V battery belt, RS-232 cable, staff,
instruction manual and shipping case.
Frequency Range: Up to 3 stations between 15 to 30.0 kHz
Parameters: Vertical in-phase and out-of-phase components as % of total
field. 2 relative components of the horizontal field.
Resolution: 0.1% of total field