Brief Introduction

MINOS (Main Injector Neutrino Oscillation Search) is the second experiment in the NuMI neutrino research program. Under this program, the main 120 GeV injector of the Tevatron collider at FNAL emits proton beam to the target 360 m away. The secondary particles of pon and Kaon produced by the target decay into neutrino beam during flight. The first experiment of the NuMI neutrino research program is COSMOS (Cosmologically Significant Mass Oscillation Search). Its detector was installed 1 km away from the neutrino target to detect t leptons produced by m neutrino oscillation using nuclear emulsion. MINOS detector was placed 700 m deep underground in the Soudan Mine of Minnesota, 730 km away from the neutrino target. These two experiments are to compare the characteristics of the same neutrino beam at two points to detect if the neutrino has changed to t neutrino.

The Soudan Iron Mine had been exploited for over a century and now it has turned into a scenic spot. The rocks on top of the mine screened the cosmic ray from penetrating the ground to such a depth with the exception of only neutrino and a few very high energy cosmic ray muons. In 1981, a 30T detector was installed in the Soudan Mine to search for proton decay. Many years later, the intention to search for proton decay gradually extended to neutrino physics, namely, to intercept neutrinos from outer space or neutrinos produced by the cosmic ray interactions in the atmosphere. In 1993, the 1000T Soudan II detector was built.

MINOS is a large international collaborative project in which nearly 200 scientists of 20 odd research institutions from China, the United States, Britain and Russia have participated. They have been studying neutrino for quite a long time. This new experiment was established on the basis of the neutrino beam and other improved experimental condition available at FNAL where neutrino experiments have been done for more than 20 years. The spokesman for this experiment is Professor S. G. Wojcicki, Department of Physics, Stanford University. He has been studying the weak interaction for 30 odd years. He had joined in the discovery of m neutrino and directed the neutrino experiment for over 20 years.

MINOS detector, weighing 10,000 tons, 50 meters long, was installed in a mountain cave close to the Soudan II detector. It is composed of a regular octagonal magnetized absorbent plate of 4 cm thick by 8 m in diagonal diameter and the alternately placed tracking chambers. It can measure the energy of the electromagnetic shower produced during the interactions of muons, hadrons and neutrons, and it can also identify the modes.