Magnetics in Archaeology
Magnetics are an increasingly key exploration method for archaeological applications. Main benefits lie in the ability to resolve details non-invasively, the wide range of artifacts and cultural affects that are detectable, and the low-cost of magnetics in comparison to other geophysical methods. Having detailed knowledge of a site prior to investigation reduces excavation costs while ensuring that no part of the site is missed. In addition, as many projects are time sensitive, availability of a rapid, effective method may mean the difference between recovery and non-recovery. GEM’s unique Overhauser & Potassium magnetometer/gradiometer systems combine data quality, survey efficiency,…
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GEMLink+ – Much More than Communication Software
GEMLink+ pre-processing software, which is provided with every magnetometer system GEM Systems manufactures provides diurnal correction, profile plotting and some basic mapping and modeling functions. GEMLink+ provides all of the data visualization features needed by the geoscientist to quickly assess the data quality of an acquired data set. Since the Earth’s magnetic field varies with time, a base station magnetometer is needed to monitor and record the variations with time. Applying the “diurnal” corrections is another function of the GEMLink+ software. GEMLink+ can import and export Google KMZ files too; the only caveat is that co-ordinates need to be in…
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Potassium Vapour Magnetometers – A Short Summary (Part 3)
Broad Line Versus Narrow Line Spectra Potassium and Rubidium have 6 spectral lines of various intensities, Cesium 133 14 and Helium 4 just one but very wide. Width of the spectral line depends on many parameters such as the size of cells, collision of the atoms with the walls of the cells, collision with buffer gas, spin exchange, etc. Contemporary Cs and Rb magnetometers have wide overlapping spectral lines. A composite spectral line is not symmetrical but the position of its peak depends on the geometry of the sensor and the applied magnetic field. There is a large shift in…
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Potassium Vapour Magnetometers – A Short Summary (Part 2)
By Dr. Ivan Hrvoic, President, GEM Systems, Inc. Optical Pumping of Alkali Vapours Only unpaired and free electrons exhibit spin with the features described above. Vapours of the alkali group of elements have a single, unpaired electron in their valence shell and they can be readily used as sources of electrons with spins. Helium gas in the other hand needs to be ionized in order to eliminate one electron from the valance shell; the remaining electron then behaves as an unpaired electron. In ground state 2 S1/2 the electron has 2 energy levels, or -1/2 or +1/2 spins. To polarize…
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Potassium Vapour Magnetometers – A Short Summary (Part 1)
By Dr. Ivan Hrvoic, President, GEM Systems, Inc. Introduction This paper is intended to provide a short overview for professionals and students who are interested in learning more about potassium magnetometers and their differences from other types of magnetometers available today. Key topics include: Physical overview of quantum magnetometers Optical pumping of alkali vapours Broad line Cesium, Rubidium and Helium versus narrow line Potassium Standard and super-resolution K-sensors and systems Future directions This paper is based on more than 10 years of research and development into the topic by GEM Systems, Inc. as well as other published results from the…
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Using Ultra High Sensitivity Magnetometers to combat Poaching
The group that oversees anti-rhino poaching operations along the western front of the Kruger National Park in South Africa has been looking for a means to improve the detection of armed insurgents. Infra-red sensing has limitations in day-time, due to high ambient temperatures and lack of penetration through vegetation cover. The area is vast (2,000 sq. km’s) but airborne investigations are only launched once there is some information as to the whereabouts of insurgents. Tree and bush cover is dense, and poachers can easily avoid visual detection from the air by taking cover. An item as small as rifle will…
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Are there Earthquakes in Canada?
Earthquakes are among the most devastating natural disasters – particularly as there are no ways to prevent them.Earthquakes occur along active faults in the earth’s crust, when the tectonic plates which comprise this crust slide past each other, collide, or diverge. The Haiti earthquake in 2010 was one of the worst natural disasters in recent years. This magnitude 7.0 earthquake led to over 100,000 deaths from the initial event, aftershocks, and the cholera outbreak resulting from disruption in health services. The tsunami which causedmassivedestruction in Japan in 2011 was caused by a magnitude 9.0 earthquake deep under the ocean. This…
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How Magnets and Gravity are Used in Mineral Exploration
Magnetic and gravity surveys differ from traditional seismic surveys in that they are passive, rather than aggressive. Instead of causing detonations or pressure waves, they measure variations in the magnetic and gravitational fields of the Earth. Although both can be used for minerals exploration, they have different strengths and weaknesses and often should be used together to give a more complete map of a potential mining location. The two methods use some common equipment. Aircraft can be used to create large-scale maps of both the magnetic and gravitational anomalies in a large region. Teams on the ground can visit points…
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Different Methods of Geophysical Surveys Used in Mineral Prospecting
Reflection Seismology What it is Reflection Seismology (called “seismic” in the minerals industry) is the practice of inducing a vibration in the Earth’s surface, and analyzing the reflection. The vibration is induced using a vibration machine or a series of dynamite blasts. This creates a seismic wave that travels to the Earth’s mantle, the ball of molten rock below are feet. The mantle reflects the wave back up to the surface, where they are measured. What it is good for Hydrocarbons. Oil, gas, and coal occur in stratified sedimentary rock. This is because they were originally biomass, like forests or…
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Requirements for Obtaining High Accuracy with Proton Magnetometers Part 5
Signal-to-Noise Ratio Limited S/N ratio will make measurement of the average period uncertain. Relative accuracy or repeatability of measurement, а prerequisite for absolute accuracy, depends to a large extent on S/N ratio of the obtained precession signal. Obviously, an effort must be made tо use all thе available information from the noisy precession signal, therefore usually all thе zero crossings are taken and used for calculation of the result. Sensor Cleanliness Obviously, any ferromagnetic inclusion in the sensor or its immediate vicinity may influence the field and cause erroneous result. Presence of AC Magnetic Fields AC magnetic fields caused by…
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