Project Management Institute

The superconducting super collider

the physics and the facilities

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THE SUPERCONDUCTING SUPER COLLIDER

The Physics and the Facilities

Neil Baggett, Director's Office, SSC Laboratory, Dallas, Texas

INTRODUCTION

The Superconducting Super Collider (SSC) will be the worlds largest and most energetic particle accelerator. It is designed to explore the basic nature of matter and energy at distance scales far smaller than is possible with existing facilities.

To build the SSC and to provide the center for exploiting its scientific promise, the SSC Laboratory was established in January 1989. The SSC Laboratory has two principal goals: to create a premier international high energy physics laboratory by the year 2000, and to create an international resource for all levels of scientific education.

PHYSICS AT THE SSC

Since the earliest times, people have been curious about what material objects are made of and what holds them together. These simple-sounding questions are as keenly interesting and vital to us today as they ever were, and are in fact the central questions of what is Called “elementary particle physics” or “high energy physics. ” Can matter be broken down into some finally unbreakable smallest parts? Can the known forces that affect matter be reduced to just one, or a few, primary interactions? If so, what are these fundamental constituents of matter and basic forces?

Deep in the heart of Ellis County, Texas, a huge machine is being built to further investigate these profound mysteries. Called the Superconducting Super Collider, it will accelerate intense beams of protons to the highest energies currently attainable and bring them into head-on collision. Teams of physicists from all corners of the earth will detect and analyze the plentiful bursts of subnuclear particles produced in these collisions and try to learn more about their ultimate makeup and their interactions.

We have known for a century that ordinary matter in the world around us is made of atoms and molecules, Each atom consists of a small, dense nucleus surrounded by a cloud of much lighter electrons, The heavy nucleus consists of neutrons and protons bound tightly together by a force much stronger than the familiar electrical and gravitational forces. Just within the last two decades, physicists have peeled away one more layer of the “nuclear onion,” to find that these protons and neutrons, once thought fundamental, actually are composed of still smaller objects called “quarks.”

This revelation came as a relief, because, along with the familiar neutrons, protons, and electrons, which make up the world of stable matter, a bewildering array of other particles had been produced in high energy collisions; particles that were undeniably real but seemed to have no understandable role in nature. These “elementary” particles lived only a tiny fraction of a second before decaying rapidly into stable ones. Now they could at least be explained as combinations of a few simpler particles, the quarks. The electron is apparently on an equal footing with the quark: both seem to be “fundamental” or “elementary” parts of matter, although physicists are now a bit wary of using these terms.

Nevertheless, today we talk about the “standard model” of elementary particles, a fairly simple picture that describes what we have learned about the basic structure of matter in this century (see Figure 1). In the standard model there are three basic “families” of particles, each family consisting of two quarks and two leptons (the electron is the most Familiar lepton). Only two of the quarks, called “Up” and “Down,” are needed to construct protons and neutrons; hence, these two plus the electron are sufficient to build our entire world and most of the matter in the known universe. The other quarks combine with the “Up” and “Down” quarks and with each other to form the exotic particles mentioned above and probably other particles that have not yet been observed. One of the quarks, the “Top” quark, has not yet been found, although it's existence is confidently predicted and it has been the object of an intensive search in the past few years. It is already known that the “top,” if it does exist, must be heavier than any known particle, and thus it may not be found until the SSC comes into operation. Another member of the third family, the “tau neutrino,” also has not yet been observed.

The quarks and leptons are affected by a few basic forces: strong, electromagnetic, weak, and gravitational (see Figure 2). The gravitational and electromagnetic forces are the best known, but the others are equally important to the makeup of the universe. The strong force binds quarks into “hadrons,” which include the neutrons and protons of stable matter, and the weak force is responsible for radioactivity, including most of the decays of the unstable particles. In particular, the electron neutrino, which feels only the weak force, plays a significant role in the energy balance of the sun and other stars. Each force is transmitted by a force carrier called a gauge boson: the photon (familiar to us in the form of radiation; for example, light, radio, television, radar, X-rays) carries the electromagnetic force, eight gluons carry the strong force between quarks, the W and Z bosons carry the weak force, and the as yet unobserved graviton is presumed to transmit the force of gravity.

Although the standard model has greatly simplified our picture of matter, it still leaves many questions unanswered. Where is the long-awaited top quark, and why is it so much heavier than the other quarks? It may not be found until the SSC provides the higher energy needed to produce it. At the SSC design luminosity, tens of millions of t-quarks should be produced each year.

why do the quarks and leptons fall into three neat families? Is there an underlying connection: could both quarks and leptons be made of yet smaller entities? If so, perhaps there are more such families. At the SSC it will be possible to probe for quark substructure at an energy scale of about half the total collision energy.

The Elementary Parts of Matter

Figure 1. The Elementary Parts of Matter

Why are there four completely independent forces? A major goal of physicists is to unify these forces, i.e., to explain them as different aspects of a single fundamental interaction. The electric and magnetic forces seemed to be quite independent phenomena until they were unified by James Clerk Maxwell in the last century (with major technological implications for society). More recently, this electromagnetic force has been related to the weak force: at much, much higher energies than we can hope to achieve, it is expected that these two interactions will merge into one “electroweak” force. At our lower energy scale, however, this beautiful symmetry is broken, and the single electroweak force “freezes out” into the two quite different forces we know as electromagnetic and weak. They have very different strengths, and the electromagnetic force carrier (the photon) is massless, while the weak bosons (W and Z) are very heavy. As a result, the electromagnetic force has an infinite range, while the weak force reaches only over nuclear distances.

The Basic Forces of the Universe

Figure 2. The Basic Forces of the Universe

The cause of this electroweak symmetry breaking at low energies must be explained before electroweak unification can be completely understood, and this is a central issue for the standard model. Various explanations have been proposed: the simplest predicts the existence of a new, massive neutral particle called the Higgs boson. If discovered, it would explain the electroweak symmetry breaking—and perhaps even the origin of all particle masses.

Even if the Higgs does not exist, some other new phenomenon must be found to explain electroweak unification, since the present electroweak theory is known to be incomplete. At energies above about 1 TeV (one trillion electron volts), it makes predictions that are logically inconsistent. The whole subject of electroweak symmetry breaking is a major topic for the SSC, which will open up the energy region around 1 TeV and is ideally suited to this investigation.

Of course there could also be new forces, as yet unknown to us, and that would mean new gauge bosons to carry them. The SSC will be able to search for new gauge bosons up to a mass of about one-quarter of the total available energy in the proton-proton collisions.

Some theorists have conjectured about the existence of a new set of elementary particles, “supersymmetric particles, ” that are identical to the known quarks, leptons, and gauge bosons except for a difference in spin of one-half unit. If this theoretical speculation were to prove correct, an entirely new form of matter could be produced and studied at the SSC.

When two protons collide, there is some probability that the constituents of each proton will themselves interact

Figure 3. When two protons collide, there is some probability that the constituents of each proton will themselves interact.

THE SSC RESEARCH FACILITY

How will all this fundamental research be done? By clashing proton beams together in head-on collisions at an energy 20 times higher than the most powerful existing accelerator can provide. A proton circulating in the SSC collider may be thought of as a vehicle carrying its quarks and gluon constituents. When two protons collide, there is some probability that the constituents of each proton will themselves interact (see Figure 3).

The collision of these constituents at high energy will be a primary objective of SSC experiments. Although the protons in the SSC collider rings will have a definite energy of 20 TeV, a proton's energy is shared among its constituents. The energy of the constituents varies, but each typically carries only a small fraction of the total proton energy. To produce significant yields of interesting events, it is necessary to accelerate intense beams of protons to an energy about 20 times greater than the energy of interest.

At 54 miles around, the SSC will be the world's biggest accelerator, as well as its most powerful. It will be a 20 TeV x 20 TeV proton-proton collider with a design luminosity of 1033 cm-2sec-l, yielding more than 108 collisions per second. The quarks and gluons inside the protons will collide at energies of about 1 TeV, the energy scale at which theory predicts new phenomena will appear as mentioned above.

The initial configuration of the SSC will include four interaction regions for experiments (see Figure 4). Four more interaction regions, located in beam bypasses in both the west and east sides of the ring, may be added as part of a future upgrade. In addition, the potential for increasing the peak luminosity of the SSC to above 1034 cm-2sec-1 is being evaluated.

The physical scale of the SSC is more than ten times larger than the largest collider now operating, i.e., the Tevatron at Fermilab. As a result, controlling the cost of the SSC without sacrificing performance goals has required detailed design studies and significant research and development, particularly for the superconducting magnets and other collider systems.

SSC DETECTORS

To detect the results of proton-proton collisions at the SSC, sophisticated experimental apparatus will be required. Detectors must sift through the 108 high energy collisions that will take place each second and identify and record the collisions of interest. The largest detectors at the SSC will be bigger and more complex than any detector now in operation. The very high rate of interactions will challenge both detector operation and data handling capabilities. Current plans call for two large general-purpose detectors and several smaller ones with more specialized goals. Each of the large detectors will be a sizable project in itself, built over a period of several years by a large international consortium of universities and laboratories, and involving hundreds of scientists, engineers, and technicians.

Weighing 30,000 tons or more, each detector will be as large as a several-story building and is apt to cost upwards of half a billion dollars. Many of the particles produced in the collisions will be electrically charged and, hence, detectable by their ionization of the detector medium. Most uncharged particles will interact and produce showers of secondary particles that can be detected. But some will be neutral and will interact very weakly, and their presence must be indirectly observed; for example, by finding an imbalance in the energy or momentum of the charged particles. Thus, it is important that all the charged particles be observed; any gaps in angular coverage would seriously compromise the sensitivity to weakly interacting neutrals, such as neutrinos, which often help to signal new physics.

Typically, the innermost layer of a general-purpose detector is a small vertex chamber surrounding the interaction point, designed to track charged particles with the highest possible resolution as they emerge in dense showers from the proton collisions. One of the vertex detector's most important tasks is to measure the lifetimes of very short-lived particles; hence, it is placed as close to the interaction point as the radiation load will allow. The next layer is usually a larger tracking chamber, which follows each particle's trajectory over a distance sufficient to measure its momentum as it curves through a magnetic field. Surrounding the tracking chamber is likely to be a calorimeter to measure each particle's energy. Large and dense, the calorimeter is designed to contain most particles, sampling the ionization energy deposited by each one as it comes to rest. The outermost layer of the typical detector consists of thick plates of steel, interspersed with tracking chambers or scintillators. This part of the detector is designed to identify muons, which do not interact very strongly and, hence, pass right through the inner layers. Muons, like neutrinos, are often important signals of new physics, and so muon chambers are an important part of the overall detector system.

Not all SSC detectors will be so gargantuan. Many physics questions can be addressed with smaller, simpler, and less expensive devices. Small detectors can be placed far downstream from an interaction point, to look at particles coming out at small angles; for example, to measure the total proton-proton interaction rate at these new energies or to look at “soft” scattering processes, essentially glancing collisions of the protons. Other experiments may focus on the study of specific known particles that can be produced more copiously at the SSC than at other accelerators. Particles made of the bottom quark, for example, can be useful in studying known but ill-understood phenomena such as CP violation.

DETECTOR CHALLENGES

The big experiments at the SSC will present a challenge to particle detector technology in terms of size, complexity, and cost on a scale 5-10 times larger than that of any detectors now available (see Figure 5).

A Schematic of the Superconducting Super Collider

Figure 4. A Schematic of the Superconducting Super Collider

The large numbers of charged particles produced in each collision and the high rate of collisions at the SSC will severely strain the capabilities of conventional tracking devices. Some of the particles will be produced in closely spaced clusters called “jets ,” and untangling these tracks will challenge pattern recognition software. Candidate technologies for tracking include silicon strip detectors, wire chambers, and scintillating glass fibers.

The unprecedented high energy of the SSC will produce secondary particles that also have very high energies, requiring larger magnetic field regions to bend them enough to measure their momenta. In the same way, thicker calorimeters will be needed to contain the high energies, and so the overall scale of the detectors will be enormous, requiring many more detector segments and readout electronic channels than ever before. Systems engineering and integration is a significant challenge for this class of detector, with so many components to assemble, support, power, read out, and interface. For example, the precise alignment of hundreds of thousands of tracking elements distributed throughout the huge detector volume will surely be a daunting task.

At rates of 100 million interactions per second, with hundreds of charged particles produced in each interaction, radiation damage will be a serious concern for detector elements, especially the inner ones. For example, at 10 cm from the beam, a vertex detector would see about half a megarad in one year of operation. Radiation-hardened silicon devices are among the contenders that might perform successfully in this environment.

Data reduction will be an essential element of any SSC experiment. Collisions will take place every 16 nanoseconds, much more frequently than in any existing collider. The detector must be “triggered” by fast electronics to identify interactions that may be of interest without being swamped by the intense stream of uninteresting collisions.

Triggering usually proceeds in several stages. The first level of decision takes place every 16 nanoseconds, storing a fraction of the data for further analysis. The next level of decision might be made every 50 microseconds, and a third level, every 10 milliseconds. At each stage, most events must be eliminated to reduce to a manageable level the amount of data that must be stored. At the same time, it is important not to lose interesting new kinds of events whose signatures may not be known initially. The triggering process will finally keep only 10 to 100 of the 100 million interactions that will occur each second.

A General-Purpose Particle Detector

Figure 5. A General-Purpose Particle Detector

TEAM RESEARCH

Collaboration is essential to scientific research on this scale. A group of physicists from several universities or labs first conceive of an experiment to address questions such as those discussed above, make a preliminary conceptual design, and then propose it to the SSC Laboratory. The proposals are studied in detail by laboratory staff and its scientific advisory committee, while the experimenters strive to refine their ideas and to build a sufficiently large and capable collaboration of scientists and engineers to turn ideas into reality.

Scientists from many countries will participate, just as they already participate in high energy physics research at existing facilities. Submitting such proposals is a highly competitive affair, and the process of selecting the best of them will take from two to three years.

Schematic Location of SCC Facilities

Figure 6. Schematic Location of SCC Facilities

The Collider Ring

Figure 7. The Collider Ring

During this time each detector concept will evolve into a detailed engineering design, and those selected will require the same kind of thorough project management that an accelerator construction project needs. The R&D for such a detector will take about three years, the construction perhaps six, and component testing and calibration, system installation and commissioning will round out the decade. Then the detector will operate for another decade, perhaps with major upgrades along the way (for example, to cope with increased machine luminosity). Thus, a budding scientist could devote a good fraction of his career to one SSC detector.

THE SITE AND COLLIDER TUNNEL

The SSC will be built in Ellis County, Texas, about an hour's drive south of Dallas/Fort Worth in a gently rolling landscape (see Figure 6). The site has geological characteristics that are well suited to tunnel boring.

The land shown within dotted lines (see Figure 7). will be acquired by the state of Texas under stratified fee; that is, the right to bore and instrument the collider tunnel will be obtained but surface rights will not. The land shown within solid lines, 62 percent of the total, will be acquired under fee simple, which includes both surface and underground rights.

The collider ring consists of four main elements: the north arc, the south arc, the west complex, and the east complex. The ring is subdivided into ten 5.4-mile-long sectors: four in each arc, one in the east, and one in the west complex. Each sector will have a service area (E) at its center and an auxiliary service area (F) at its end; each sector will use about 50 acres at the surface above the tunnel. The “E” service areas will support cryogenics in the tunnel, magnet power supplies, electrical power and control systems, personnel and equipment access, and various other utilities. At half of the “E” areas, a 55-foot-diameter shaft will be dug to permit insertion of superconducting magnets in the tunnel. The “F” areas will provide support for tunnel ventilation, electrical power and control, and tunnel drainage. A 15-foot-diameter shaft will be located at each “F” area.

The collider ring tunnel will be excavated primarily by tunnel-boring machines. The finished internal diameter of the tunnel will be about 12 feet; the width at floor level will be about 10 feet. At many locations around the ring, there will be alcoves and niches for cryogenic and electrical apparatus.

THE ACCELERATORS

Five accelerators working in close harmony will actually be needed to bring about the final collisions of two 20-TeV proton beams (see Figure 8). The first four accelerators, collectively referred to as the injector complex, will accelerate protons by stages, each handing off the beam to the next, like ever faster runners in a relay race. The final injector, called the High Energy Booster (HEB), will be a sizable machine in its own right, accelerating protons to 2 TeV, twice the energy of the highest energy proton machine now operating. It will inject the protons into the collider itself, the big ring, where they will be taken up to the final energy of 20 TeV, held there in a coasting orbit for many hours, and brought into collision each time they pass the intersection points, where the detectors will be set up for physics research.

The collider itself will consist of two rings of superconducting magnets, one 0.8 m above the other, that will intersect at four points around the ring to provide collisions for experiments. Each ring will have two nearly semicircular arcs, one north and one south, and two clusters of long, straight sections, east and west. One straight section of each cluster will be used to inject or remove the beam and to provide space for radio frequency cavities (for acceleration of the beam in the collider rings). In the other part, the beams will be brought into collision in two interaction regions. These will be located on one leg of a diamond-shaped bypass; the other leg will be available. for a future upgrade.

The precise layout of the injector complex has been determined not only by physics considerations but also by the site. The HEB will be at approximately the same depth as the collider ring. There will be one utility straight section in the HEB for transferring beams into both collider rings. The significant surface elevation change over the area of the HEB means that the HEB could not reasonably be located near the surface. However, the smaller Linac, low energy booster (LEB), and medium energy booster (MEB) can all be accommodated near the surface. Beams will be transferred down from the MEB to the HEB through two transfer lines. The HEB and the MEB are tangent to a line through the test beam area, so beams from both the HEB and the MEB could potentially be extracted to produce secondary beams. In the initial configuration, only beams derived from the MEB will be available; beams from the HEB could be made available in a future upgrade.

The Five Accelerators

Figure 8. The Five Accelerators

SUPERCONDUCTING MAGNETS FOR THE COLLIDER

The collider's superconducting magnet system bends and focuses the proton beams in the storage rings and guides the beams into collision at the interaction points. The critical elements in this system are the thousands of superconducting collider dipole magnets that must operate with very high reliability during the lifetime of the SSC. All the collider magnets will be required to survive more than 10.000 accelerator cycles, in which the field varies by a factor of ten, from that required at the 2 TeV injection energy to the 20 TeV collision energy. In. addition, the magnets will be required to withstand about 50 thermal cycles from room temperature to the operating temperature of about 4°K. Finally, the magnetic field must ensure reliable storage of the beam at injection, during ramping to 20 TeV, and for day-long stretches at the collision energy.

The magnetic field will be created by currents in both inner and outer magnet coil layers. Superconducting cable must be carefully positioned in a cosine theta distribution (measured from the horizontal midplane) to provide the dipole field while keeping other components of the field within tolerance.

A technician at Brookhaven Laboratory examines a dipole magnet designed for the SSC

A technician at Brookhaven Laboratory examines a dipole magnet designed for the SSC.

The major components of a collider dipole are the coils of NbTi superconductor in a copper matrix, the stainless steel collar that holds the coils rigidly in place under the strong magnetic forces, and the cold iron yoke. This cold mass is encased in a stainless tube and mounted in a cryostat that uses a folded support system to keep heat leaks to a minimum. Dipole magnets of two lengths-about 15 m and 13 m—are required for the collider lattice. The operating field at 20 TeV is about 6.6 T at a temperature of 4.35°K.

The main emphasis of the dipole magnet research and development program over the last few years has been on the mechanical design and quench behavior of the magnets. The substantial magnetic forces on the conductor can cause it to move very slightly, giving rise to local heating and thereby quenching a magnet, i.e., causing a sudden transition from the superconducting to the normally conducting state, with a finite electrical resistance. Magnets have been instrumented to determine the location of quenches and to measure the forces on the collars constraining the coils. The results have been compared with model calculations to obtain a fundamental understanding of the mechanical behavior of the magnets. The lesson learned is that preventing conductor motion is imperative. Achieving that aim requires detailed designs and calculations as well as strict adherence to quality control standards.

An acceptable dipole magnet must not quench below the operating field during initial testing or after thermal cycling. It must also:

  • Remain useful for at least 25 years;
  • Withstand 50 thermal cycles, while retaining allowable field qualities;
  • Withstand 100 quenches; and
  • Withstand 20,000 magnetic cycles.

To determine the ability of the magnets to meet these requirements, accelerated life tests will be performed on prototype collider dipoles in the next two years.

CRYOGENIC SYSTEMS

The SSC will apply superconductivity on a scale vastly larger than any previous application. An extensive cryogenic system is required to provide cooling for the superconducting magnets. The system must be highly reliable to ensure availability of the SSC for research.

The size of the SSC is such that a single centralized cryogenic system is not appropriate. Instead, a number of independent units will be employed for the collider and for the high energy booster. However, although these units can operate separately, they will be interconnected for redundancy to help ensure reliable operation. The collider will have ten cryogenic sectors with a liquid helium refrigeration plant located at the midpoint of each (at the “E” service areas). Refrigeration equipment could be incorporated in the “F” areas if required as part of a future upgrade (for example, to increase the luminosity).

To cool the magnets, single-phase helium at 4.15°K and 3-4 atmospheres will be fed into a 4-km string of magnets on either side of the refrigerator. It will flow through the magnets in series and be re-cooled periodically to maintain the operating temperature of 4.35°K or lower in all magnets. At the end of the string, the helium flow will be reversed and returned to the refrigerator.

Large amounts of cryogens are needed to cool the magnets. For example, the liquid helium inventory in the collider magnets will be about 45,000 liters. In addition to providing for steady state operation, the refrigeration plant must function effectively and reliably under a number of other conditions: cooldown of the magnets from ambient temperature to 80°K and then to about 4°K, warmup of part of the ring, and possibly operation at temperatures below the nominal operating temperature to condition the magnets. It may also be necessary to shift the load from one sector to another for repairs. Recovery from a quench, which dumps the helium inventory in a half cell and raises the temperature to 20°K, must be as fast as possible.

BEAM INSTRUMENTATION AND CONTROLS

An extremely precise and sophisticated control system is required to deliver beams of the right energy to the right place at the right time. Instrumentation and diagnostics will be needed not only during routine operation but also for commissioning and for improving machine performance. Diagnosis of faults is also a major function of the overall instrumentation and control system.

Some SSC Parameters

A few key parameters of the SSC are given below. Some 17,000 bunches of protons circulate in opposite directions around the two collider rings, each bunch making a complete revolution in about one-third of a millisecond. Thus, bunches are crossing 60 million times per second at each interaction point. Only a small fraction of the protons in each bunch actually collide, most passing through without touching. Nevertheless, with 1010 protons per bunch, there are 100 million proton collisions each second. This rate is determined by the luminosity, roughly the product of the current in one beam and the density in the other, and the proton-proton interaction cross section, which is estimated to be about 100 millibars at 20 TeV.
Proton energy 20 TeV
Circumference of rings 87.120 kilometers
Proton bunches per ring 17,424
Protons per bunch 0.75 x 1010
Protons per ring 1.3 X1014
Proton orbit frequency around collider 3,400 revolutions/second
Bunch spacing 5 meters
Proton beam diameter 5 microns
Luminosity 1 x 1033 cm-2 sec-1
Proton interactions per second 108
Total number of superconducting magnets (collider plus high energy booster) 12,123
Dipole length and weight 15.8 meters and 5,000 kilograms
Total length of superconducting cable 25,000 kilometers
Total weight of iron in magnets 44,000 tons
Liquid helium required for refrigeration 2 million liters
Liquid nitrogen required for refrigeration 1 million liters

Beam instrumentation must measure the proton beam's position and intensity at many locations around the rings, measure the beam profile, and detect beam loss. A variety of instruments will be used. Beam position monitors, located at most quadruple magnets, contain electrodes above, below, and on either side of the beam. Processing the signals from these four electrodes will allow accurate measurement and control of the position. Beam intensity monitors will measure the total circulating current in all rings. The transverse size of the beam will be measured at a few locations around each ring either with flying wire scanners, which move a very thin wire at a known rate through the beam and use a detector to measure the interaction products, or with synchrotrons radiation light monitors, routinely used in electron-positron colliders. Beam loss monitors, simple gas-filled tubes sensitive to ionizing radiation, will be placed around the rings (about every 30 m in the collider) to detect radiation from beam losses. The monitors will both protect against radiation damage from beam loss and aid in tuning the machine.

Beam instrumentation, power supplies, vacuum systems, and cryogenic systems must all be monitored and synchronized. For many subsystems, local control will be needed during construction or maintenance. The safety of personnel and equipment must be guaranteed at all times, even if communication to a central control point is lost. The control system is made up of sensors connected to a hierarchy of computers. The accelerator complex will contain a total of 140,000 monitor and control points. Information from local sensing elements will be acquired, filtered, processed, and delivered to a higher level computer for additional processing. Ultimately, the information will go to human operators in the central control complex.

OPERATIONS CYCLES

The Linac will be commissioned first, then the LEB, the MEB, the HEB, and finally the collider. Collider operation may be divided into four time periods: initial commissioning, initial operation for experiments with gradual improvements in reliability and performance, sustained operation for experiments, and upgraded operation.

The injector complex will function in two modes: injecting beams into the collider and providing external beams (initially from the medium energy booster and later from the high energy booster) to the test beam area. A complete high energy booster cycle takes about 2 minutes, and filling one of the collider rings with protons takes about 15 minutes. At design luminosity, the storage time in the collider rings will be about one day. Thus test beams can be provided during most of each day.

CONCLUSION

A lot has happened since the SSC laboratory was founded in January 1989, but a lot more has to happen before the first protons collide. The laboratory staff has grown from a few pioneers to 750 people, the project design has been thoroughly revised and adapted to the specific site in Texas, all major accelerator parameters have been fixed, detailed design leading to construction is underway and the process of defining the initial research program has begun. The big job of managing this project, to complete it within the next eight years and within budget, are discussed in the next two sub-articles in this issue. We at the SSC Laboratory are proud and excited to be helping this technical colossus to take shape beneath the golden wheat fields of Texas and, at the dawn of the twenty-first century, to become a primary international center for basic research at the frontier of physics.

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Neil Baggett, Ph.D., is a physicist in the Directorate at the SSC Laboratory. Among various administrative activities, be serves as Secretary to the Scientific Policy Committee and the Program Advisory Committee.

Dr. Baggett joined the SSCL in October 1989, with more than twenty years experience in physics research and administration. The first half of his career was devoted to research in experimental high-energy physics at Heidelberg University in Germany, Imperial College in England, and Purdue University, USA. Since 1977 be has worked in science administration, including service as a research program manager in the High Energy Physics Division at the U.S. Department of Energy and as a special assistant for high energy physics in the Director's Office at Brookhaven National Laboratory.

Dr. Baggett is a member of the American Physical Society and the American Association for the Advancement of Science. He holds a BS in physics and mathematics from Tulane University and a Ph.D. in physics from the University of Maryland.

This material has been reproduced with the permission of the copyright owner. Unauthorized reproduction of this material is strictly prohibited. For permission to reproduce this material, please contact PMI.

November 1990

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