Our data was collected each day over the course of three weeks. We recorded the number of muons detected by our muon counter and observed the sun for varying numbers of sunspots. We also collected data from the World Wide Web of the planetary k index and sunspot number (www.sec.noaa.gov).
We
use a scintillation device with a photomultiplier to record when a muon enters
the detector, and when it decays into an electron and neutrino. Inside the
detector is a large organic crystalline lattice. When a muon enters the
detector, it collides with atoms in crystal, causing electrons in the atoms to
be "kicked up" into higher energy levels. When they return to their ground
state, these energized electrons emit light. Likewise, when the muon decays
into an electron, the electron will cause other electrons in the lattice to be
energized. Their subsequent return to ground state will also emit light. The
time difference between the light emitted from the muon's entry to into the
detector and when it decays can be measured. This quantity is defined as the
muons decay time in our reference frame.
However, the intensity of light emitted by electrons when the muon enters and
decays is not significant enough for us to measure. A photomultiplier must be
used to amplify the intensity of the signal. This device converts the energy
of the emitted photon into an electrical signal. A photon emitted by an
excited electron collides with a photocathode, freeing an electron. The
photomultiplier tube is composed of a series of metal plates. Electrons
between these plates are successively accelerated through the space between the
plates. An electron on a plate will cause electrons to "jump off" the next
plate. These electrons are, in turn, accelerated to the next plate. At the
end of the plates, the photons have created enough electrons to produce a
measurable signal.
The scintillation counter is linked to hardware and software devices that
create a histogram of entry and decay events. Because muons have a lifetime of
2.2 microseconds, we assume all muons will decay within 1 ms from the time it
is first detected. Therefore, a logic gate is connected to the photomultiplier
and will only register an event if the time between the muon entering and
decaying is less than 1 ms. Through this screening, we weed out events that
could be caused by charged particles that do not decay (such as electrons).
The computer compiles the data from the logic gate and plots it on a linear
histogram that categorizes events according to the time it takes for each muon
to decay.
We
used a small telescope (see Figure 3 on the following page) with a solar filter
to observe the sun and count the number of dark dots on its surface. This
number is the number of sunspots that we count for each day, even though it is
possible that the number of sunspots varies during a day. We were, of course,
unable to do this observation on cloudy days. This definitely affected the
completeness of our data.
Due to the high number of cloudy days and the fact that we failed to see any
sunspots through the telescope, we were forced to compile our sunspot data from
the World Wide Web. We took this data from a site maintained by dxl.solar.org.
The data on this site was gathered from the United State Government's Space
Environment Center.
We also record this value from the world wide web site maintained by dxl.solar.org. This site displays the Ap indices calculated from satellite data.