The Mark I, also known as the SLAC-LBL Magnetic Detector, was a particle detector that operated at the interaction point of the SPEAR collider from 1973 to 1977. It was the first 4π detector, i.e.
The Mark I, or the SLAC-LBL Magnetic Detector, served as a particle detector operating at the SPEAR collider's interaction point between 1973 and 1977. This device was the first of its kind to be a 4π detector, namely