To measure the density
of a volcanic lake using muons, we need two muon telescopes. One muon telescope
is placed on the lake shore. It measures the muon flux reaching the surface
of the volcanic lake. The second muon telescope is placed at the bottom of
the volcanic lake. It records the muon flux passing through the water column.
The difference in muon flux between the two telescopes can be used to calculate
the total density of the water column.
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This principle is based on the fact
that water in a volcanic lake attenuates or absorbs more muons, and changes
in the difference in muon fluxes at the lake surface and at the lake bottom
can be used to estimate changes in the water density of the volcanic lake.
Changes in the water density of a volcanic lake can indicate the dynamics
of certain geochemical processes that may indicate changes in the internal
structure of the volcano, such as magma movement or the filling and emptying
of hydrothermal reservoirs.
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Principle and method.
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Atmospheric muons are high-energy
particles formed when cosmic rays interact with the upper layers of the Earth's
atmosphere. They penetrate the Earth's surface at various angles.
As they pass through a material, muons are scattered and absorbed. The degree
of attenuation directly depends on the density of the material—in our case,
the density of the water in the volcanic lake. The number of detected muons
is inversely proportional to the density of the water through which they
pass.
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Limitations.
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1. Resolution.
The accuracy of water density measurements depends on the size and sensitivity
of the detector, as well as on the total muon flux, which can be low for
very dense or thick water columns.
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2. Measurement time.
Collecting sufficient muon data for accurate water density measurements
requires longer measurement times. This is especially true for low muon fluxes.
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3. Atmospheric influence.
The muon flux can be affected by atmospheric conditions, which must be taken
into account for accurate measurements using a control muon telescope located
on the lake surface.
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4. Complexity.
Data analysis can be complex, as it may require accounting for scattering
and background noise from other particles.
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In this article, we will focus on
the engineering features of a system for measuring water density in a volcanic
lake.
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1. Selecting a detection system.
Since the operating conditions for a measuring system at the bottom of a
volcanic lake can be extremely harsh (pressures of approximately 20 atmospheres
and temperatures exceeding 100 degrees Celsius), the choice of muon detector
will be limited. The most suitable option would be Geiger-Müller counters,
which can operate at temperatures of up to 150 degrees Celsius.
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Careful attention should also be
paid to the selection of components for the electronic circuit, ensuring
they can operate at high temperatures. The price of such an underwater muon
meter should also be an important factor. It should be as low as possible,
as such a device is practically a one-time use item, especially if used to
measure the density of liquid in a volcanic lake.
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The muon telescope's power supply
system requires careful consideration. High temperatures also limit the choice
of power source.
Powering the telescope via cable is impractical for the harsh conditions
of a highly acidic and high-temperature volcanic lake with a depth of approximately
200 meters.
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There are two options here: using
high-capacity lithium batteries operating at +150°C, or using galvanic
cells that generate electricity while operating in the lake's acidic environment.
A good option would be a combination of such a galvanic cell and a battery.
However, unfortunately, there are currently no batteries that operate at
+150°C.
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Let's consider the issue of transmitting
information from a muon telescope located at the bottom of a volcanic lake.
Two methods can be used here: ultrasound and low-frequency radio (8 kHz).
Each has its advantages and disadvantages. The radio-frequency method allows
the receiving station to be installed far from the shore of the highly acidic
lake. The ultrasound method, however, requires the receiver to be installed
in the aquatic environment of the highly acidic lake. It remains to be seen
which method is less energy-intensive and consumes less battery power.
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The most challenging engineering
challenge is constructing a structure that will allow the muon telescope
to be positioned on the bottom of a volcanic lake in a strictly vertical
position (a deviation of a few degrees is acceptable).
Horizontal deviation is less critical.
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The underwater muon telescope (radiosonde)
will be lowered into a volcanic lake at significant depths in free fall.
We can't predict where it will land, as we don't know the terrain there.
The structure could practically assume any position after reaching the bottom.
A design that allows the muon telescope to assume a vertical position is
needed.
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Once the muon telescope (radiosonde)
reaches its predetermined position, it begins operation.
The designs of the muon telescope, both the onshore and underwater portions,
must be identical in terms of both the Geiger-Müller counter type and
background shielding.
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According to the electrical circuit,
these two components should also be identical. The main components of the
muon telescope's electronic circuit are: a 3.6-volt to 400-volt voltage converter
(for powering the Geiger-Müller counters), a coincidence circuit, an
8-kHz transmitter, and a 3.6-volt and 400-volt voltage control circuit.
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The operating principle of the system
is very simple: Geiger counters register all particles passing through them.
A lead shield filters out particles from the natural gamma background, and
only muons pass through the Geiger-Müller counters. However, two Geiger-Müller
counters are positioned strictly vertically, approximately 60 mm apart. The
only muon that needs to pass through both counters is the one that registers.
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A coincidence circuit, developed
100 years ago, is used for this purpose. This circuit is a logical "AND"
gate. We will devote a separate section to the operation of this circuit,
as the coincidence circuit is the basis for muon detection.
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When a muon passes through both counters
simultaneously, a voltage pulse will appear at the output of the coincidence
circuit. This voltage pulse is fed to the 8 kHz transmitter modulator, and
a radio signal will be emitted via the antenna, which will be received by
a shore-based receiver. The receiving station, located on the shore of the
volcanic lake, processes signals from both the underwater muon telescope
and the muon telescope located on the shore. After collecting the data and
processing the signals, it is possible to determine changes in the density
of the liquid in the volcanic lake.
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