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.

　　It is expected that from the beginning of 2003, the MINOS experiment will start to detect if neutrino has changed to another kind of neutrino, namely, t neutrino. Such a change is also called oscillation, a clear evidence proving that neutrino has mass. Based on this change, scientists can calculate how much the neutrino mass is.

Content of MINOS Int'l Cooperation from 1995 – 1997

　　The MINOS international cooperation came into being in February 1995. As IHEP is very experienced in fabricating large quantities of streamer tubes and large steel plates, Professor S. G. Wojciki , spokesman of the MINOS international cooperation worked out in August 1995, together with IHEP scientists, the program for the initial work to be undertaken by IHEP during the R & D and upgrading stage of MINOS. It comprised the following parts:

　　1. Development and improvement of new brand plastic streamer tubes

　　As early as 1985, IHEP had succeeded in developing the plastic streamer tube and setting up a workshop for its mass production. 3,000 square meters’ plastic streamer tubes were provided for ALEPH experiment, which operated well for many years. In this respect, we have a fairly good experimental foundation in terms of the team, equipment and rich experience, which put us to the forefront in the world. During the experiment on neutrino oscillation, large quantities of plastic streamer tubes totaling 38000 square meters will be used, which have to be fireproof and high heat resisting. Therefore higher demands were made on the plastics, the gas and the mode of readout to be used. In order to develop the fireproof and high heat resisting new brand streamer tubes for mass production, the technological process will have to be chosen and the working conditions and performance of the streamer tubes fixed.

　　According to plan, the production of streamer tubes would be carried out in the following three stages:

　　The first stage was preparation which covered the re-assembly, repair and reconstruction of the machines used by ALEPH, the study of the melting point of plastics and the fabrication of molds for the new brand extruded plastics, and the technology (The extruded plastics was originally fabricated in Shanghai and later by Beijing No. 7 Plastics Manufacturer.) and the fabrication of pin cap up (originally planned to be imported from abroad, but now it has been decided to be homemade).

　　The second stage was the study of the technological process for mass production of plastic streamer tubes using machine and the test of the produced prototypes in batches.

　　The third stage was the test of various schemes, including the composition of different gases, the study of all possible schemes of the wire/strip readout modes, the selection of the graphite layer with specific resistance, the choice of different working conditions and the study of signal performance.

　　2. Joint designing and fabrication of large steel plates with Xinhe Shipyard

　　The detector used in the experiment on neutrino oscillation is composed of 600 layers of 4 cm thick steel plates (8 m × 8 cm) and 600 layers of counters. The 8 m×8 m×4cm steel plate was made by piecing together the 2 m wide by 2 cm thick steel plates vertically to ensure its flatness and the uniformity of the magnetic property. IHEP boasts the experience in making the yoke of BES and m absorbing magnet of SDC at FNAL. It follows that evaluation can be made of the feasible mass production and the price on the basis of the trial-production of a prototype. As the law of Minnesota forbids the importation of iron products from outside, the MINOS Collaboration Group had to cancel the plan to fabricate the iron plates in China.

　　3. Monte Carlo simulation of neutrino oscillation