|
The photographs above show WWSL's Cosmic Ray Experimental Modules
at the Florida site, top, at the Oregon site, bottom left, and at the Moscow site, bottom center and right. Click pictures to
enlarge.
Oregon and Moscow setups,
see layout,
consist of two scintillating detectors telescope. The signals from the
detectors are read out to a coincidence unit. The unit selects
events due to cosmic ray particles passing through both detectors.
The output signals from coincidence units are collected by a data
acquisition system and a computer. For study of penetration
properties and composition of cosmic ray, an absorber of variable
thickness (a set of lead or tungsten plates) is sandwiched between
detectors.
The telescope of Florida Cosmic ray lab module,
see Florida telescope layout, consists of two (upper and lower) 4-detector
sections. The lower detector section simultaneously serves as a carrier
for the lower absorber lead (Pb) blocks. The upper absorbers carrier
(table between lover absorbers and upper detector section) is motorized.
Thus, this device serves as a 4-channel telescope, with all 4 channels
registering the flux of the cosmic ray in parallel, but each channel has
different absorber thickness.
The sequence of the thicknesses of the lead absorber blocks for the
lower carrier, in inches is: 0, 8, 4 and 0.5. For the upper carrier
it is 0, 2, 1 and 3 correspondingly. Using a remote control window in
the browser, students can rotate the upper carrier to different
experimental positions. After the selected position of the table
is established, the student takes data from the four channels
simultaneously with the different thicknesses of the absorber.
This gives the student four data points
for each measurement period. Thus, the total number of experimental data
points is sixteen. The advantages of the design are:
- The amount of time needed to collect the experimental data is four
times shorter. It is a very effective use of the student's time for data
collection. Since all four scintillation telescopes are used, all Pb
absorber bricks are in service simultaneously;
- Since the student is able to take data for the four experimental
points concurrently, he/she can immediately observe the effect of
absorption of the cosmic rays (nuclear charged particles) in matter;
- The lead absorbers have been situated to give absorber thicknesses
from 0-4 inches in 0.5 inch increments, and from 4-11 inches in 1 inch
increments.
This is optimal because the maximum changes occur in the region from 0 to 4
inches of Pb-absorber thickness, thus the data region of greatest interest
lies from 0-4 inches;
- It is possible to use this setup to investigate additional effects
of cosmic rays, such as: the study of the cosmic-ray showers in the
atmosphere; study of the muon decay, etc.
Student projects which can be pursued
using these setups can be divided into two groups:
Projects
studying the properties of cosmic rays and the experimental methods
and apparatus of cosmic ray and high energy physics;
Projects
studying the properties of random processes (in this case, the flux
of cosmic ray particles is considered as a generator of random
processes). The first group may
contain the following projects:
- The composition of cosmic rays near the earth's surface;
- The angular distribution of cosmic ray flux;
- Fluctuations in energy loss of charged particles;
- The effect of the detector's dead time on the character of the
statistical distribution of the signals.
The second group may contain
the following projects:
- Properties of Poisson statistics;
- The relationship between binomial, Poisson and normal
distributions;
- Fitting data to different statistical distributions;
- The "waiting time paradox" for Poisson processes;
- Study of correlation in stochastic processes.
With wide choices of projects
available for each experimental setup, educators can select sets of
projects which best suit their students.
|
