Shantanu Menon Thomas Irons Michael Jacoutot

Cosmic Rays  High energy particles (mainly protons) from outer space.  Have up to 10 million times more energy than particles accelerated even by large particle accelerators, such as the LHC.  Collides with particles of atmosphere and decay into new products in a extensive cascade of particles. One of the particle types produced is the muon.

Muons  Elementary particle – belongs to same family as electrons. Has a negative charge, and about 200 times the mass of an electron.  raining down per square meter per minute on earth.  Lifetime of 2.2μs.  Ionise air that they are in direct contact with when travelling.

Principles of a Spark Chamber  Popular in the 70’s as a way of detecting particles formed in cosmic air showers.  Consists of a series of metal plates in an airtight box, filled with an inert gas (Helium, neon, argon, or a mixture of these)  As a charged particle travels through, it ionises this gas.  A trigger system quickly applies a high voltage to the plates, creating a strong electric field.  A spark forms along the path of least resistance i.e- the ionisation trail left by the particle. This shows the exact trajectory of the particle

Design Of Detector Coincidence detector Scintillator MaterialPhotomultiplier Tube Conducting Unit Gas Connector Tube Scintillator MaterialPhotomultiplier Tube

Scintillator Material  Special materials that emit photons when ionising radiation (e.g. Cosmic-ray muon) passes through it.  Normally generates photons in the visible range.  Variety of materials i.e. crystals or plastics – we use plastic scintillator

Photomultiplier Tube  Turns an input signal of photons into an electronic signal

High-Voltage Supply  Aluminium Plates at 6500 V.  A high-speed semiconductor switches from low voltage of PM circuit to high voltage of chamber.  High voltage necessary so that a spark travels across the ionised air between plates.

Coincidence  Only muons are penetrating enough to pass through the entire chamber.  Therefore, if a signal is detected at the top scintillator and the bottom scintillator, the particle must be a muon.  Only when the coincidence unit (a series of logic gates) detect simultaneous signals from the top and bottom of the chamber, will it switch on the High Voltage supply and cause the chamber to spark.

ADC CONICIDENCE HV Switch (Solid State) HV Supply (EHT)

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