CosMO-Mill

CosMO Mill

The CosMO mill (Cosmic Muon Observer) is permanently installed at DESY Zeuthen. It consists of a rotating frame on which two CosMO detectors are mounted at a fixed distance of 97 cm.

Driven by a stepper motor, the position of the mill arm is changed every hour by 15 degrees within an interval of -90 to 90 degrees. This hourly rotation allows us to study the dependence of the rate of cosmic particles on the zenith angle.

To filter false signals, the two detectors are switched in coincidence. This means that only those signals are evaluated which were measured by both detectors. This coincidence circuit at a detector distance of almost one meter also reduces the aperture angle of the experiment and thus enables a more precise determination of the direction of the particles.

Setup

The CosMO Mill consists of:

two CosMO detectors
a DAQ card,
a wing arm with the two detectors mounted at 97 cm distance,
a step motor and the electronic components to steer the arm,
a notebook to control the angle position and for the accumulation of data with the program muonic.

Data Structure

The datasets available via Cosmic@Web contain: time, atmospheric pressure, temperature, angle position, particle rate. More detailed information can be found in the description of the Dataset.

Possible Student Exercises

Investigate the particle rate in dependence of the zenith angle.
Investigate the influence of weather conditions on the rates.
Compare the measurements from different years.
Compare the mill's rates with those of the Trigger Hodoscope.
Compare with own measurements performed with the CosMO or Kamiokannen experiments.

Example Diagrams

At Cosmic@Web you will find few example diagrams using the Session-ID CosMO-Muehle.

Frequency Distribution of the Muon Rate

This frequency chart, or 1D histogram, shows what muon rate was measured how often.
For this purpose, certain rate ranges were defined and the values that lie within one range were counted. With Cosmic@Web a certain number of such ranges ("bins") can be defined. Here, for example, the rates were divided into 100 ranges.

But how does this distribution come about? What could be the explanation?

Muon Rate - Angle - Atmospheric Pressure Diagram

In this xy diagram, muon rates of several measurements for each angle are plotted. Color-coded is the prevailing atmospheric pressure at the time of measurement.
Overall, however, only the measurements for a specific period of time are considered. This contains a phase with a rather high and one phase with a rather low atmospheric pressure. The exact settings can be found on the session ID CosMO-Muehle.

But what does this diagram tell us? What conclusions can be drawn from this?

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