SLAC's Cosmic Ray Detector
The SLAC Visitor Center Web cam
There is a web cam in the SLAC visitor center that is aimed at SLAC's Online Cosmic Ray Detector.
Above, you see the picture the web cam saw as of a few seconds ago. It updates about every 15 seconds. (Just hit "Reload" on your browser).
The Cosmic Ray Detector
The Cosmic Ray Detector consists of three pairs of scintillator panels for muon detection. Sets A, B, and C (see below) are oriented with the flat surface of the panels horizontally, at 45°, and vertically, respectively. In each pair, the panels measure 4.875 inches (12.4 cm) wide by 8 inches (20.3 cm) long, and the distance between them is 18.5 inches (47.0 cm). The panels are shielded from light with aluminum foil, black plastic sheets, and black tape. When muons penetrate through these panels, chemicals within will scintillate (emit flashes of light).
Click on above image for a larger view
The light emitted passes through the light guide (D) to a photomultiplier tube (E).
Click on above image for a larger view
The photomultiplier tube amplifies the signal. The base of the tube is connected to the circuit board (F). The circuit is designed to register one count when it receives a signal from both scintillator panels in a set (pair). This implies that a muon has penetrated through both panels. The digital readout (G) displays the number of muons counted.
Click on above image for a larger view
Want to see the detector in action? The following are links to 15-second mpg movies of the detector in operation. The images are dark so you can see the visual displays. The files are large, will take some time to download, and you will need a player to view the files.
