In the light of present knowledge, the total number of unanswered problems in high energy physics which might be investigated with facilities in the range of energy between 30 and 200 BeV appears to be enormous. In addition to the obvious scientific merit of such intermediate energy facilities, there are also questions of geographic distribution to be considered. The presently existing high energy laboratories, although operating as fully national facilities, do exhibit certain regional characteristics. Some of the difficulties of the university-based research groups (cf. Chapter IX) can be reduced when the distances are hundreds, rather than thousands, of miles. In the face of these positive arguments for constructing a "sub-frontier" accelerator, or of raising the energy of some of the existing ones, there remains the hard fact that the time interval between the initiation of plans for such facilities and their initial impact on physics is of the order of 10 years. By that time, the regions of energy of most significant interest will be considerably higher than they are today. Furthermore, under continuing fiscal restrictions, proposals for new accelerator facilities must be carefully weighed against the further development of the NAL. Additional target areas and associated facilities at this laboratory must receive very high priority in the future; alternatives must be thoroughly reviewed for their contribution to the overall program in high energy physics. In the light of these considerations it is difficult at the present time to justify the construction of new accelerator facilities that depend upon conventional technology for an energy range below that of the 200 BeV accelerator. But the application of one of the new technologies offers the possibility of a very meaningful contribution to the entire program. A modernization program using new techniques, or a "pilot" model of a new concept in design, could test and evaluate the technology considered best suited for reaching much higher energies besides maintaining the vitality of some of the laboratories where there now exist large investments in site, ancillary equipment, and experienced personnel. The methods whereby some of our leading high energy laboratories could be thus improved to provide facilities more significant for research in the period some 10 years hence cannot be defined today. The outcome of the technological developments now being pursued will probably determine the choices to be made. (All are synchrotrons except those marked * which are linear accelerators.) PPA Bevatron ZGS AGS Cornell SLAC Western Europe: Saturne Nimrod CERN-PS Bonn DESY NINA U.S.S.R.: Princeton-Pennsylvania Accelerator, Princeton, New Jersey Alternating Gradient Synchrotron, Brookhaven National Cornell University, Ithaca, New York Cambridge Electron Accelerator, Harvard University, Stanford Linear Accelerator Center, Stanford, California Commissariat a L'Energie Atomique, Saclay, France Deutsches Elektronen-Synchrotron, Hamburg, Germany ITEP JINR Serpukhov Kharkov Yerevan Institute of Theoretical and Experimental Physics, Moscow Institute of Physics (GKAE), Yerevan, Armenian SSR TABLE II STORAGE RING PROJECTS DESIGNED PRIMARILY FOR ELEMENTARY PARTICLE PHYSICS EXPERIMENTS* Comment First working storage ring. Experimental program complete. Shutdown in 1968. Very high current designed to permit strong interaction physics experiments. FY 1971. R&D in progress. Proposed for Use of the synchrotron as a storage ring yielding Experimental program in progress. Storage studies in progress. Experimental program Design goals similar to proposed Stanford 2 BeV Operation expected in 1971. Under construction. CERN 30 BeV PP 40 *Other projects, designed primarily for beam dynamics studies, Kharkov (USSR) Shutdown July 1967. Physics experiments in progress. Construction of physical plant is complete. Ring tunnel complete. The project involves use *Ceased doing physics research, end 1967; self supporting through medical fees since then. May be closed down in "about a year or so." **NSF support ceased three years ago; however, occasional running done since then by state funds. VI. SUBSIDIARY EQUIPMENT FOR HIGH ENERGY PHYSICS EXPERIMENTS High energy physics experiments require specialized equipment which has to be continuously adapted to the changing needs of the experimentalist and to evolving technology. Some of this equipment is almost as complex as an accelerator and requires several years for construction. Typical of the facilities provided at an accelerator laboratory are one or more bubble chambers, large spectrometers and components for spark chamber and counter systems, on-line data-handling computing systems, and beam transport components (bending magnets, quadrupoles, particle separators, etc.) for both extracted primary beams and the secondary beams emanating from various target stations. Other equipment is provided by the experimental groups. A forecast of the requirements in this area is essential for proper planning. A. Detectors Five years ago the detection equipment used in most experiments was either a hydrogen bubble chamber or a combination of scintillation counters which could feed signals into electronic logic and recording devices. In the intervening years, a very large evolution has taken place in both pictorial and electronic detection. 1. Pictorial Detection Techniques. The hydrogen bubble chamber has been the most productive single tool of detection used in high energy physics research during the past decade. Its virtues are that the detecting medium is of sufficiently high density to permit copious interactions, and that these interactions can be analyzed with excellent spatial resolution. The recent successful operation of bubble chambers containing mixtures of liquid neon and liquid hydrogen means that the density of the medium can be varied continuously from that of pure liquid hydrogen (i.e., protons) to that of liquid neon. The higher density mixtures give greater stopping power of the charged tracks and higher probability of converting gamma rays at the cost of sacrificing some spatial resolution. Another advantage given by the bubble chamber is that all charged particles emitted in any direction leave visible tracks. Consequently, it is an exceedingly useful device to high energy physicists faced with new energies, new particle beams, or particularly rare processes. Because a large amount of information for every interaction is preserved on film the physicist can find and establish the existence of a previously |