Cosmic Ray Hodoscope Cosmic Ray Hodoscope
An array of scintillation counters detects the passage of cosmic rays through the apparatus. A row of LEDs lights up to indicate the direction of the particle.
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Twelve slabs of plastic scintillator are each viewed by
a photomultiplier. The passage of a charged particle through the
scintillator creates an electrical signal. A coincidence in time of
signals in diametrically opposed slabs indicates that a cosmic ray has
crossed the apparatus. This causes a bell to ring and the line of LEDs
connecting the two slabs is illuminated for a short time.
Click the picture for a larger picture. |
Many people will not realise that they are constantly being traversed by ionizing radiation. Primary cosmic rays, mostly protons, arrive at the upper atmosphere from outer space. There they undergo nuclear reactions with the air molecules which result in the creation of a large number of secondary particles. The ones that reach the earth, and trigger the hodoscope, are mainly muons. The direction of the muons at sea level is predominantly vertical, although occasionally even horizontal muons will be detected.
The apparatus is self-contained, and should begin operating as soon as the mains lead is connected.
All parts of the apparatus are permanently fixed to the frame.
The equipment is heavy, and requires four people to lift, for example to load into a lorry for transport. Wheels and suspension should mean that it can be installed in its operating position without difficulty. The photomultipliers generate the required high voltages internally, so there is no high voltage hazard.
The apparatus is mounted on wheels and has a good suspension. However it should be handled with care as the scintillators could be broken or the light connections damaged.
Weight : 75 kg
Dimensions : 1000x1000x1200 mm
Barney Brooks, Department of Physics, Oxford University, Nuclear and Astrophysics Laboratory, Keble Road, Oxford OX1 3RH
Tel: 01865 273245
email: b.brooks1@physics.ox.ac.uk