One module of the ten new 'supergondolas' for the UA 1 experiment at CERN's proton- antiproton collider. It contains 38 2-mm layers and 24 5-mm layers of depleted uran ium absorber interspersed with 62 boxes of containing TMP, an organic liquid which can contain free electrons at room temperature. Each supergondola contains 16 such mo dules. This revolutionary new method of calorimetry (measurement of energy de position) could go on to become a standard technique in the detectors of tomorrow.
(Photo CERN 224.6.88)
MORIOND Fifth force fervour Was Newton right in thinking that the pull of gravity on a body is governed by its inertial mass? If he was, then all bodies have the same free fall acceleration, as Galileo tried to check in his classic but not very accurate experiments at the leaning tower of Pisa. This equivalence of inertial and gravitational mass went on to be come a basic principle in Einstein's general theory of relativity, and so is a cornerstone in our under standing of the Universe. Successive experiments have checked this out to a precision of one part per billion under certain conditions. However several years ago some physicists began to think along different lines when a reana- lysis of Eotvos' classic 1922 ex periments found tiny systematic ef ganic liquid which can contain free must be perfectly clean, free of all fects, hinting at a possible tiny electrons. UA1's upgrade called for impurities which would otherwise matter-dependent repulsive force 13,000 litres of TMP, the largest capture signal electrons. Before as acting against gravity. quantity ever used so far. sembly, all box components are As matter is characterized by its Particle showers are created in ultrasonically cleaned in hot deion- nuclear composition, such an effect sheets of depleted uranium, 300 ized water and then baked out un has implications for protons and tons in all. The increased neutron der vacuum at 900°. The boxes are neutrons. Perhaps there is a fifth yield in the uranium ensures more laser welded and after initial stack force at work, supplementing the equal responses from strongly in ing are rinsed with hot ultrapure well known mechanisms of gravity, teracting particles and electrons water, dried with pure argon, electromagnetism and the strong ('compensation'), improving also baked out at 300° under vacuum and weak nuclear forces. However the hadronic energy resolution. and then filled with pure TMP, pre while ingenious theorists can The TMP is contained in 34,000 viously cleaned using silica gel and dream up a framework for such a 3 mm-thick stainless steel boxes molecular filters. force, it is not a vital part of ongo fitted with all the necessary elec The perfection of all these tech ing physics ideas. trodes, high voltage feedthroughs, niques is the result of a heroic ef New experiments looking for filling pipes, etc. and manufactured fort. In tests last year, the first non-Newtonian gravity were cov by industry. The 40 cm-deep su- complete modules gave excellent ered in the Moriond workshop permodules are built up using alter results, in particular giving the 'Tests of Fundamental Laws of nate layers of uranium and TMP same results for electrons and po Physics', held recently in Les Arcs boxes. In the electromagnetic sec sitrons. This is promising for the in the French Alps. The studies fall tion a position detector is inserted new physics runs, and perhaps into two categories - those looking with horizontal and vertical strip el points to a new path for exper for composition-dependent forces ectrodes to localize the shower. imental physics. and those searching for terrestrial To function properly, the TMP deviations from the classical gravi-
10 CERN Courier, May 1989 BDH Limited, Advanced Materials Division Contact: BDH Limited, Broom Road, Poole, Dorset BH12 4NN, England. Tel: (0202) 745520. Fax: (0202) 738299. Telex: 41186 or 418123 TETRA G. No room any more for a fifth force? Strength of an additional composition-dependent force (vertical axis) plotted against the mix ing parameter relating this force to neutron and proton numbers. Unlike before (April 1988, page 11), there is now no region where positive and negative results are compatible. The lowest curve is from a lead- copper beam balance measurement by C. Speake and T. Quinn at the Bureau Inter national des Poids et Measures, Sevres, near Paris.
objects falling towards the sun, but X=1000 m (2d) extending the validity of the limit.
\ A possible resolution of the ap // v ;\ / i y 1 i\ '•• \ ' - A. ; parent discrepancies between dif S-/ / \\ \ / ! / , - - V \ / ferent results has been proposed
y . by Goldman, Nieto and Hughs us ing a two component model in •^y ^ ••^y--' spired by quantum gravity. How ever the E6t-VVash Experiment \\ ~\ ~' ~ - - - ~ ~~ ~~ — — • showed that with the ranges which A \ ~~~ ~ — - — - — might be inferred from geophysical experiments, this model is not compatible with the resultant com position-dependent couplings. "/''-• With new composition-depend ent experiments not confirming earlier positive results, the compo sition-independent experimental sit uation is not yet resolved either. Don Eckhardt summarized the sta tus of the Air Force Geophysics Lab tower experiment which last year hinted at a small deviation from Newtonian inverse-square tational pull which decreases as the complete. gravitation. The technique is to square of the separation. (Devia Pier Bizzeti covered the Flor- measure gravity on the ground sur tions from this inverse square law ence/INFN 'Vallombrosa Experi rounding the tower, extrapolate the are well known in extraterrestrial ment' which floats a 10-cm nylon gravitational field up the tower and physics and are understood from ball on a stratified solution of po compare with measured values. general relativity.) tassium bromide. After many sys During the past year scrutiny has Four composition-dependent ex tematic and auxiliary studies, no uncovered some biases in the periments were discussed. Riley fifth force effects are seen. ground survey which decreased the Newman reported on a study by an Eric Adelberger and Chris Stubbs discrepancy. Additional measure Irvine group using a balance to presented results from the Wa ments are needed at another tow compare the acceleration of lead shington 'Eot-Wash' project. Signi er. and copper to that of lead. ficant apparatus improvements Such an experiment, by a Colo Measurements and systematics have led to a 25-fold increase in rado team, was discussed by Tim were completed with the experi sensitivity over the 1987 results. Niebauer and Clyde Speake. Efforts menters blind to the results during They use a four-mass beryllium- began last August on a 300 metre 260 hours to eliminate any subjec copper or beryllium-aluminium tor tower with studies of how vibra tive bias. A null result emerged. sion balance rotating relative to a tions could affect the gravimeter A positive result reported last hill or a lead source, and new data measurements. The conclusion year by the Washington group ('the clearly precludes a composition- was that under appropriate weath Index experiment') was taken up by dependent effect of the strength er conditions, the measurements Paul Boynton. A further year's originally suggested. They have are unaffected. Preliminary data work has revealed several system also been able to test the equiva taken above 100 metres was in atic effects but does not modify lence of gravitational and inertial reasonable agreement with the the original result. Upgraded equip mass for the Earth's gravity to a Newtonian prediction. However fi ment has improved sensitivity by level of less than 3 x 10"11, reach nal conclusions await more ground an order of magnitude, and new ing the same sensitivity as previous measurements in the immediate vi measurements should soon be measurements which compared cinity of the tower to take care of
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© 1989 Huntington Laboratories Now completed at Fermilab is the 250 MeV proton synchrotron for the Loma Linda Med ical Center in California. After tests at Fermi lab it will be shipped to Loma Linda this summer. the enormous sensitivity to even slight local gravity anomalies. An experiment by a Lawrence Livermore team using a 465 metre tower at the Nevada Test Site was described by Paul Kasameyer and Jim Thomas. A ground survey of 280 measurements made within 2.6 km of the tower was combined with 60,000 measurements from a gravity data base of the Western United States maintained by the U.S. Geological Survey. A prelimi nary analysis was consistent with Newtonian theory. Mike Gorman and Richard Hughes presented a composition- independent study by a collabora tion working in Greenland. Instead of going up a tower, they went down a 1700 metre borehole into the ice cap, comparing the extrapo lation of surface gravity with under for several years. ground measurements. Their com FERMILAB Treatment has also been avail parison is perturbed by effects Medical machine able at the Lawrence Berkeley Lab from the ice-rock interface and the oratory, using first the 184-inch cy calculated ice density shows al takes shape clotron and later the Bevalac, and most a 4% deviation from the in at laboratories in Sweden, the verse-square law. However they USSR, Japan, Switzerland, and Ca cannot rule out the effect being due The proton synchrotron being built nada, and has recently begun in to gravitational anomalies in the at Fermilab for the Loma Linda Uni South Africa. However all this worki rock substrata, and are seriously versity Medical Center, California, has made use of accelerators built considering moving to a better lo has been completed. Beam has for research and subsequently ad cation in Antarctica. been accelerated to the maximum apted for therapy. Plans for new 'fifth force' experi design energy of 250 MeV and ex The rapid development in the ments include measurements of the tracted. Commissioning studies are last few years of new imaging free fall of electrons and positrons underway and will last until July, methods has made it possible to as well as protons and antiprotons. when the accelerator will be dis locate a tumour with high preci Theoretical presentations looked at mantled and shipped to Loma Linda sion, complementing the dose lo the open possibilities and their im for installation. calization possible with protons. plications. The use of protons for cancer In April, 1986, Loma Linda and Summarizing, Frank Calaprice of therapy was first suggested by Ro Fermilab agreed that Fermilab Princeton could point to the pro bert Wilson in a famous paper pub would design and build a synchro gress over the past year with lished in 1946. The great advan tron with a maximum energy of 'many beautiful experiments'. The tage of protons or other heavy 250 MeV to be used specifically remaining 'serious discrepancies' charged particles is the localization for therapy. Fermilab personnel are being examined by ongoing ex of dose because the particle dumps have also contributed to the design periments. most of its energy at the end of its of the remainder of the Loma Linda trajectory (the Bragg peak). The cy facility. Science Applications Inter Workshop report from Orrin clotron Wilson built at Harvard has national Corporation was chosen Fackler and Marshall Mugge been used for this type of therapy as an industrial partner.
14 CERN Courier, May 1989