Setup

As can be seen in the schematic illustration, the active components of the Sevan detector are three plastic scintillation counters. The photomultipliers (PMTs) are not directly connected to the scintillator planes. Here, scintillation light spreads out through the air within light tight cones.

Between the outer plastic scintillators of 100 x 100 x 5 cm³ there are placed two 4.5 cm thick lead absorbers and a scintillator stack of 50 x 50 x 20 cm³.

Data Acquisition (DAQ) electronics provides registration and storage of all logical combinations of the detector signals for further off-line analysis. Muons produce a signal traversing either all three scintillators or in the outer region the upper and lower only. Incoming neutral particles as gammas and neutrons can produce charged particles only in the thick 20 cm scintillator resulting in scintillation light. Low energy electrons and gammas can produce a signal in the upper scintillator only. Their shower particles are absorbed in lead layer. Inclined particles, which do not hit the upper but give a signal only in the lower scintillator plane cannot be specified, charged and neutral particles are possible.

 

Data structure

The data sets available via Cosmic@Web contain: time, year/month/day/hour, particle rates for 8 trigger conditions, atmospheric pressure, temperature. More detailed information can be found in the description of the dataset.

 

Possible Student Exercises

• Estimate the particle rates for all 8 coincidence (trigger) conditions in dependence on time and compare the results.
• Analyse the dependency of the particle rates on atmospheric pressure and temperature.
• Compare the results of different years.
• Search for extreme solar events which produce so-called Ground Level Enhancements (GLEs) and lead to an increased cosmic particle rate within a few hours.
• Search for Forbush Decreases caused by strong solar winds, that reduce the rate of cosmic particles.

The last two proposals require an atmospheric pressure correction of the particle rates. References to GLEs and Forbush events can be found on the internet.

 

Example Diagrams

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

 
Muon Rate - Time - Atmospheric Pressure Diagram


This xy diagram shows the muon rates between July 2012 and May 2019. Color-coded is the prevailing atmospheric pressure at the time of measurement.
A muon signal is a signal that was measured either in all three scintillator layers or only in the upper and lower plate in the outer area. The exact settings can be found on the Session-ID SEVAN-Aragats.

• What is noticeable about the measured value distribution? What can be concluded from this, what is the physical explanation?

 

Muon Rate - Time - Atmospheric Pressure Diagram


This xy diagram shows the rates of various particles over the course of several years (2012-2019). The rate of low-energy particles is shown in blue, the muon rate in green and the rate of high-energy electrons or positrons in red.
The exact settings can be found on the session ID SEVAN-Aragats.

• What does this distribution show us? How can this be explained?