NEWS staff and visiting scientists in celebrating the on-time, under-budget completion of the $260 million project. New Fermilab "It has taken seven years to reach this dedication day-a long time," said Fermilab director John Peoples, whose 10 year term in office has spanned the entire project. machine dedicated The new main injector will, literally, be a major boost for Fermilab's centrepiece machine -the superconductingTevatron proton syn­ chrotron and proton-antiproton collider. In 1991 a $2.2 million challenge grant from the state of Illinois enabled Fermilab to take the first steps towards building the new main injectors. Federal funding was approved in October 1991, and construction got underway in 1993. The main injector team worked together so well that a new storage ring - the antiproton recycler - was added to the accelerator com­ plex without increasing the total project budget or delaying its scheduled completion. The recycler, which shares the new, 2 mile, circular tunnel with the main injector, uses permanent magnets to retrieve, store and literally recycle antiprotons that would previ­ ously have been discarded. TheTevatron, which began operations in Fermilab's new 2 mile circumference, 150 GeV main injector (foregound) injects particles 1983, was previously fed by Fermilab's origi­ into the larger Tevatron. nal main ring, closed in 1997 after 25 years of service. The Tevatron and the main ring shared The world's newest particle accelerator - Secretary Bill Richardson, the Speaker of the the same 4 mile circumference tunnel. As the Fermilab's 150 GeV main injector - officially House of Representatives Dennis Hastert and Tevatron injector, the main ring was a bottle­ began its career on 1 June. The US Energy Illinois Governor George Ryan joined Fermilab neck in the antiproton supply. A "family album" photograph of the LEP hits 100 final module of superconducting CERN's LEP electron-positron collider walked accelerating onto the stage for its 1999 season and, after cavities for its customary greeting at the Z resonance CERN's LEP (45 GeV per beam), impressed the waiting electron-positron audience by quickly taking a shot of electrons collider. These to a record 100 GeV.This showed how cavities power smoothly its complement of 288 supercon­ LEP beams to ducting accelerating cavities can pull together, 100 GeV. supplying 3.15 GV (3.3 GV without beam). Soon after, colliding beams were estab­ lished with 98 GeV electrons and positrons for ties (1-2 inverse picobarns per day). 80.5 GeV in 1996 with more superconducting radiofrequency tests. After these spectacular Just 10 years ago, LEP began operations accelerating power. Last year, LEP ran rou­ opening fireworks, high-energy physics got equipped with room temperature copper tinely at 94.5 GeV per beam. under way with 96 GeV electron and positron radiofrequency accelerating cavities, supply­ At these new high energies, the LEP experi­ beams. Collision rates were high, with lumi­ ing 45 GeV per beam. From 1995, equipped ments are treading on potentially very fertile nosities well above 1031 cm~2s~\ with sizable with superconducting cavities, LEP's beam physics ground and could soon reveal what beam currents and good integrated luminosi- energy was increased to 65 GeV, then to makes the electroweak theory tick. CERN Courier July 1999 5 NEWS Magnetic detector sees cosmic-ray anomalies Proton Flux P mim Flux -* 10 •2 10 10 r * o $* ! J* r % \ I -3 1 f f./&*L 1 1 r'/f: I 1 I IK f 09<( f0 -S 1; Ci 4 V* I 1 *. V W .* *, * V -6 O W r * v» i •7 -7- • 0.3 2 10 J >'1 10 to H 1 m »0 Kinetic Energy (GeV) Kinetic Energy (GeV) £ner^y ^VW) F/^. 1; Expected cosmic-ray proton Fig. 2: Cosmic-ray proton distribution Fig. 3: Antiparticle puzzle. In the equatorial distribution with latitude at an altitude of measured by the AMS experiment aboard region, AMS sees about four times as many 400 km. the Space Shuttle at various latitudes. low-energy positrons as it does electrons. As reported briefly in the June issue (p6), the for antinuclei above the screen of the atmos­ moving upwards as downwards. It is as Alpha Magnetic Spectrometer (AMS) presents phere, but a sample of almost 3 million though these particles are confined in a mag­ several intriguing effects, which include unex­ cosmic helium nuclei arriving from outer netic toroid around the equator. pected distributions of cosmic-ray particles, space did not reveal one helium antinucleus. A similar effect is found with electrons, but from its 1998 trial Space Shuttle flight. AMS sees no primordial antimatter, but 3 mil­ here it is interesting to compare the levels of From 2 to 12 June 1998, AMS was the lion nuclei is not many and the search electrons and their antiparticles - positrons. If primary payload of NASA's Space Shuttle continues. However, AMS did see several other cosmic-ray electrons and positrons are cre­ Discovery in orbit 400 km above the Earth. unexpected effects, which show that the ated in pairs by high-energy gamma rays, This was a shakedown mission prior to behaviour of cosmic rays is much more com­ there should be as many electrons as there deployingAMS on the International Space plicated than had been thought. are positrons. However, in the equatorial Station in a few years time. In orbit, AMS was able to intercept cosmic region AMS sees about four times as many AMS is a sophisticated magnetic detector rays arriving at different latitudes as the Earth low-energy positrons as it does electrons. of the type normally used in high-energy turned. Cosmic-ray protons have a range of AMS also looked at the distribution of physics laboratories. During the 10 day voy­ energies and the Earth's magnetic field helium nuclei. In a final conundrum, around age, AMS recorded the tracks of millions of should repel less energetic particles.This the equator and at low energies, AMS only cosmic-ray particles. It was the first time that terrestrial magnetic repulsion becomes sees the helium-3 isotope. Helium-3 is very such a sophisticated physics detector had weaker at higher latitudes, and more particles rare on Earth but was one of the protonuclei been deployed in space and the first time so of low energy should be seen nearer the formed during the one minute, or so, of the much information on cosmic particles had poles, with a magnetic cut-off at each latitude universe's primordial nucleosynthesis. been recorded.The first results from this mis­ (figure 1). However, AMS finds that, below a AMS is a major international collaboration sion have been eagerly awaited. certain proton energy for each latitude, there covering Europe, the US, China and Taiwan The advertised goal of AMS was to search is no magnetic cut-off and the distribution and is led by Sam Ting of MIT - longtime for signs of cosmic antimatter. In a universe increases strongly instead (figure 2). spokesman of the L3 experiment at CERN's created from a Big Bang that must have gen­ When the Space Shuttle flips over, AMS can LEP electron-positron collider. erated matter and antimatter in equal initial also collect cosmic particles moving upwards, amounts, there should be signs of this primor­ away from the Earth. Few high-energy, Correction dial antimatter, with antinuclei built of upwards-moving protons are seen, but the Last month we unfortunately misspelled the antiprotons and antineutrons. However, our spectrum fills up rapidly for lower-energy name of Eberhard Keil, who did such a universe appears to be built up entirely of particles. In a band extending over 4000 km thorough job in coordinating the reports from matter and no experiment has ever detected at the Space Shuttle orbit altitude of 400 km, the 1999 Particle Accelerator Conference. any primordial antimatter. AMS set out to look below about 6 GeV AMS saw as many protons 6 CERN Courier July 1999 NEWS transferred to the beam and then dissipated by synchrotron radiation. Accelerating power for the LHC Proton beams lose little energy in this way. The main role of the LHC cavities is to keep the many proton bunches tightly bunched to ensure high luminosity-at the collision points and to deliver power to the beam during energy ramping. Matching these radio- frequency conditions using conventional copper cavities would lead to unacceptable displacement of the beam crossing points. Superconducting cavities with small losses and large stored energy are the best solution. This leads to a design using single-cell accel­ erating cavities with large beam tubes, similar to those considered for the new generation of electron-positron colliders. The LHC will use eight cavities per beam, each capable of delivering 2 MV (an acceler­ ating field of 5 MV/m) at 400 MHz.The cavities will operate at 4.5 K (the LHC mag­ A protoype cryomodule containing superconducting accelerating cavities for CERN's LHC nets will use superfluid helium at 1.8 K). For proton collider. the LHC they will be grouped in fours in cryo- modules, with two cryomodules per beam, For CERN's new LHC proton collider, supercon­ of the more expensive solid niobium.The LHC and installed in a long, straight section of the ducting magnets will not be the only super­ is set to use this technology from the outset. machine where the interbeam distance will be conducting technology in the 27 km ring. The LHC's radiofrequency must be a mul­ increased from the normal 195 to 420 mm. When the collider was commissioned in tiple of 200 MHz, the operating frequency of The cavities are being made by spinning and 1989, the energy of CERN's LEP the upstream SPS synchrotron, to allow rapid electron-beam welding, with the surface nio­ electron-positron collider was 50 GeV per transfer of many SPS proton bunches, but not bium being added by magnetron sputtering.