literature

Design of a Variable Length Muon Shield in Area 1

Aug 1, 1970
15 pages
Report number:
  • FERMILAB-TM-0262

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Abstract:
It is argued that the circumstances of normal operation will exert heavy pressures to operate the neutrino beam in Area 1 at 200 GeV most of the time and that consequently it is very important to try to achieve maximum operating intensity for 200-GeV operation, without sacrificing the 500-GeV capabilities of the area. To accomplish this, a tunnel running about half the length of the 1000-meter dirt shield is proposed which is left open as an extension of the decay region for 200-GeV operation. It is terminated with a hadron dump for the 200-GeV muon beam. For use at 500-GeV, the tunnel is plugged by one of several methods and hadron dump at the front end restores the full 1000-meter shield. The tunnel can be either a pipe into which perchloroethylene is pumped to fill it and from which it can be emptied into a separate reservoir, or else a subway passage that can be plugged by "railway cars" carrying concrete plugs, or with stations into which iron plugs may be moved laterally. More detailed analysis is required to decide among these methods, all of which appear to satisfy the prime requirements. An overall increase in intensity of neutrinos by a factor averaging about 2 is obtained in this way for 200-GeV operation.
  • high or else, if made of dense material like iron, they could be inserted and withdrawn laterally. Iron being four times as dense as soil, only a quarter of the tunnel length would need to be filled with the plugs. The axial plug system could very well utilize ordinary concrete, of density 2. Another possibility is uranium hexafluoride, which is available from the AEC for the cost of transportation only, already canned in cylinders 3 ft. in diameter and 15 ft. long, of density 5. This material is undesirable on the grounds of toxicity and environmental hazard in case of a spill. If the concrete plug is inserted from the end, it is difficult to avoid long leakage paths along the surface of the plug, which must have some clearance from the tunnel wall. It is possible to avoid these, but expensive
    • K. The
    • which deserve further investigation: one liquid, perchloroethylene, and two solids, concrete and iron. SYSTEM CONSIDERED AS AN EXPERIMENTAL SETUP The iron-plug system has one advantage not shared by the other systems. It provides unequaled facilities for measuring and monitoring the muon flux in the shield. It also permits the design of experiments to study the properties of muons up to 500 GeV, including the rangeenergy relations. It would allow extensive studies on shielding and on the scattering of high-energy muons and might lead to information that would enable more effective shields to be designed. Plug systems have the advantages of being safe, free from noxious substances and environmental hazards, and straightforward in conception and exe cution. In addition, the plug materials are not activated by the hadron beam, since they are exposed only to muons and neutrinos and -IO- TM-2 62 2271 are removed when hadrons are present they, therefore, avoid the radioactive disposal problem that residues of liquids in the pipe would pose. VI. SUMMARY It seems likely that at least one of the above systems can be designed to produce an economical and feasible system to vary the length of the shield. While it is too soon to estimate costs, it does not seem unreasonable to put an upper limit of about $
      • V. the Iron-Plug