A Journey through particle detectors
Krista Smith, Cesar da Silva
Los Alamos National Lab
A summary of particle detectors
CERN high school on particle detectors :
http://hst-archive.web.cern.ch/default.htm
Thompson Experiment - 1895
Cathode rays were a mystery back in the late XIX century.
The ray could be bent by electrical field like charged spheres. Later he measured how the ray was deflected by different electrical fields and concluded :
“we have in the cathode rays matter in a new state, a state in which the subdivision of matter is carried very much further than in the ordinary gaseous state: a state in which all matter... is of one and the same kind; this matter being the substance from which all the chemical elements are built up.”
Scintillator – Crookes 1903
A scintillator is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate (i.e. re-emit the absorbed energy in the form of light).
First scintillator made by Crooks was a ZnS screen where he could see light from alpha particles.
Today, many materials (plastic, liquids, etc) are used for particle scintillation.
Rutherford Experiment - 1911
The solid angle distribution of alpha particles reflected by the gold foil indicates that the matter is concentrated in the nucleus of the atom.
Measure ion pairs inside a hermetically sealed box.
Victor Hass in 1911 brought an electrometer to a balloon and confirm previous observations that air ionization grows with altitude. After find the result was the same during a sun eclipse he conclude the particles were coming from space, not the sun. That is how cosmic rays were discovered.
Electrometer – Wulf 1909
Charles Wilson found that when an ionizing particle passes through the chamber, water vapor condenses on the resulting ions and the trail of the particle is visible in the vapor cloud.
Cloud Chamber - 1911
Bubble Chamber – Glaser, 1952
A cylinder filled with liquid (usually hydrogen) just below its boiling point. A piston decreases its pressure and the liquid enters in a metastable phase.
When a subatomic charged particle cross the liquid it forms bubbles which can be seen.
Spark Chamber
A stack of metal plates placed in a sealed box filled with a gas such as helium, neon or a mixture of the two. When a charged particle from a cosmic ray travels through the box, it ionizes the gas between the plates.
Wire or Drift Chamber – Charpak 1968
Muon Tracker – LANL, UNM, … 1999
A wire chamber made by LANL and collaborators for the PHENIX Experiment in BNL.
This is just the smaller of the 6 chamber stations built.
MicroOmega Chamber – Charpak 1991
Evolution from the Drift Chambers where higher gains and smaller time were obtained by placing a micromesh 100 microns from readout strips.
Hugo is leading A MicroOmega project for sPHENIX.
Gas Electron Multiplier – Sauli 1997
Similar to MicroOmegas but using foils with holes to obtain even larger charge gain.