123535745
The structure of dual green functions
Abstract We exhibit a simple relationship between the position space and momentum space singularity structure of off-shell dual amplitudes. This scheme is naturally described in terms of amplitudes which couple to the external sources via pairs of “confined” states.
120539667
Anomaly cancellations in supersymmetric D = 10 gauge theory and superstring theory☆
Abstract Supersymmetric ten-dimensional Yang-Mills theory coupled to N = 1, D = 10 supergravity has gauge and gravitational anomalies that can be partially cancelled by the addition of suitable local interactions. The remaining pieces of all the anomalies cancel if the gauge group is SO(32) or E 8 × E 8 . These cancellations are automatically incorporated in the type I superstring theory based on SO(32). A superstring theory for E 8 × E 8 has not yet been constructed.
121062482
N=4 Yang-Mills and N=8 Supergravity as Limits of String Theories
The formulation of supersymmetric string theories in ten dimensions is generalized to incorporate compactified dimensions. Expressions for the one-loop four-particle S -matrix elements of N = 4 Yang-Mills and N = 8 supergravity in four dimensions are obtained by studying the string-theory loop amplitudes in the limit that the radii of the compactified dimensions and the Regge slope parameter simultaneously approach zero. If certain patterns that emerge should persist in the higher orders of perturbation theory, then N = 4 Yang-Mills in four dimensions would be ultraviolet finite to all orders, whereas N = 8 supergravity in four dimensions would have ultraviolet divergences starting at three loops.
9607753
Anomalous creation of branes
In certain circumstances when two branes pass through each other a third brane is produced stretching between them. We explain this phenomenon by the use of chains of dualities and the inflow of charge that is required for the absence of chiral gauge anomalies when pairs of D-branes intersect.
121755839
PHASE CONTOURS AND BOOTSTRAPS. I.
123230985
Off-shell states in the dual model
Abstract We present a class of Lorentz invariant, gauge invariant off-shell amplitudes for the ordinary Veneziano and Ramond-Neveu-Schwarz dual models. They correspond to interactions with the string which are local in space-time.
120781819
Cryogenic techniques for large superconducting magnets in space
Abstract A large superconducting magnet is proposed for use in a particle astrophysics experiment, ASTROMAG, which is to be mounted on the US Space Station. This experiment will have a two-coil superconducting magnet with coils which are 1.3 to 1.7 m in diameter. The two-coil magnet will have zero net magnetic dipole moment. The field 15 m from the magnet will approach earth's field in low earth orbit. The issue of high T c superconductor will be discussed in the paper. The reasons for using conventional niobium-titanium superconductor cooled with superfluid helium will be presented. Since the purpose of the magnet is to do particle astrophysics, the superconducting coils must be located close to the charged particle detectors. The trade-off between the particle physics possible and the cryogenic insulation around the coils is discussed. As a result, the ASTROMAG magnet coils will be operated outside the superfluid helium storage tank. The fountain effect pumping system which will be used to cool the coil is described in the report. Two methods for extending the operating life of the superfluid helium dewar are discussed. These include: (1) operation with a third shield cooled to 90 K with a sterling cycle cryocooler and (2) a hybrid cryogenic system where there are three hydrogen-cooled shields and cryostat support heat intercept points. Both methods will extend the ASTROMAG cryogenic operating life from 2 years to almost 4 years.
55437946
Various Magnet Options for a Delta Launched Version of Astromag
This Report compares various superconducting magnet options for use in a particle astrophysics experiment to be launched with a Delta rocket into a sun synchronous orbit and an earth trailing solar orbit. The goals of the experiment are to study the incidence of anti particles coming from deep space and to study populations of light nuclei (up to atomic number 8) and gammas from deep space. The proposed superconducting coils, which would be made with an aluminum stabilized niobium titanium superconductor, would be cooled using stored super fluid helium. Both a sun synchronous orbit and an earth trailing solar orbit permit one to shield the magnet and cryogen vessel behind the solar panels. This permits one to reduce the temperature of the cryostat outer vessel that increases to cryogen life time for the experiment. A number of superconducting coil and cryostat options were looked at in terms of total magnet and cryostat mass, cryogen life time, complexity and overall particle astrophysics capability for attached detectors.
121794117
THE ROLE OF QUENCH BACK IN QUENCH PROTECTION OF A SUPERCONDUCTING SOLENOID
Abstract This report demonstrates the role of quench back in the quench protection of high current density superconducting solenoid magnets with well-coupled shorted secondary circuits. The phenomenon of ‘quench back’ can be used to greatly reduce the size of an external quench protection resistor or even to eliminate the need for an external quench protection system altogether. A comparison is made with conventional magnet quench protection systems with and without a closely coupled secondary circuit.
120458015
LARGE SUPERCONDUCTING DETECTOR MAGNETS WITH ULTRA THIN COILS FOR USE IN HIGH ENERGY ACCELERATORS AND STORAGE RINGS
LARGE SUPERCONDUCTING DETECTOR MAGNETS WITH ULTRA THIN COILS FOR USE IN HIGH ENERGY ACCELERATORS MiD STORAGE RINGS. H. A, Green Lawrence Bemeley Laboratory llo1.versity of California Beme1ey, california MASlIR This paper describes the development of a ni!W class of large superconducting soleiwid magJ!l!ts. High energy physics on colJ,iding beam machines sometimes require the use of thin coH' solenoid magnets. ,The development of these ,magnets bas proceeded with the substitution of li'ght materials for heavy materials and by ,inCrea9ing the current density in the coils. The Lawrence Beme1ey Laboratory bas developed a 1:adtca1 approach to the pEOblem by ba'ldng the co11 operate at very high cur1:ent, densities. This approach and its implications are described in detail. Introduction Recent'developments in colliding beam physics have prompted the development of thin superconductiog solenoid magnets for use ia these experiments. The development of thin m3g0ets can be traced starting with PLUTO, the fi1:st superconducting magnet which was used to do colliding beam physics. The evolution of thin coil technology can be trsced by comparing PLUTO (which is not a thin superconducting magnet) with three other superconductiog magnets which have been built OT are being built for colliding beam experiments. All tbree of these magnets are 'designed to be thin to some degtee. A comparative' study of the four magnets illustrstes the trend of thin supercooducting co11 development over tbe last two D1: three years. first, Doe sees tbe substitution of lighter materials for heavier msterials in the CERN magnet. Then ooe sees the abandoDlll!nt of cryogeoic stsbility wben the batb cryostat is replaced witb tbe tubular cooling system in the CELLO magnet. F1oslly, tbe conductive bore tube concept is introduced in order to make a radical improvement in the ,protection' of thin solenoid magnets against burnout. This is the basis of the TPC magnet design proposed by the Lawrence Berkeley Laboratory (LBL). Over half of this pap'er will be devoted to the LBL magnet 'technique. Since the LBL tecb- nique is a radical departure from conventioosl technique, this paper will present tbe theory of the conductive bore tube and discuss the resulta of experiments on LBL test coils. Three test c.oils· have been c.onstruc.ted at LBL. Two of these coUs, each with a diameter of one meter. have been fully tested and the results are presented herein. Preliminsry tests on the third test 'magnet, which bas a diameter of two meters, are described. The results' of these tests show the viability of the LBL two-phase tubular cooling system and the conductive bore tube for diverting the magnetic current from the superconducting coil. The LBL technique ia applicable to magnets in a variety of sizes. The radiation thickness attainable is a function of diameter and central induction. Thia relaticoship is sbown in this pape::. In addition, one can apply light sUperconductors and conductive bore tubes. This can, in principle, result in reduction of the radiation thickness of solenoids whicb bave a diam- eter below a certain value. t a The development of thin solenoid technology The 'development of thin nagnet technology can be traced by comparing four colliding beam detector solenoids which have been built or are about to te built. The first of these magnets is PLUTO. This magnet, which makes no effort to bj! thin, was built in 1971 using tbe conductor and stabilization technology used in the large bubble cbsmber(l). The second magnet, ISR, built by Horpurgoat' CERN' in 1976, Bub Q !ltuted a cryt;>genica11y stabilized allllll1J1um conductor for th~ ciJpperc< iductor normally used l ). The vacuum ve,.sela and cryostat vessels are also msde of aluminum; The third step iil this progression is the msgnet, proposed for the CELLO elCPertment by !;aclsy and',Karlsrube using ilitrinaically stable aluminum conductor which operates 'at current densitieS' of 1.4 x 108 &-2(3). The fourth step 1n the progress10n is represented by the magni!t proposed for the time projectiOn cblllltJer (TPC) experiment by the Lawrence Beme1ey Laboratol.y(4). This magDet, uses superconductor at very high matrix current densities (about 109 Am- 2 h' - The msgriet uses a tVo-pbase tubular COOling system. The ,four magnets ':e clllllpsred in Table 1. The PLUTO magnet bas the largest central inductiOn 'and ~est free wI ,. ,The TPC magnet has both the,largest free volume and stored eaergy. The ISR '!liagnet bas the alliallest stored energy end i t has a central induction of 1.S T lik'l the CELLO ana' TPC magnets. The thiekeBt magnet from a radiation standpOint is' the PLUTO magnet. The,' thinnest magnet ia the TPC magnet. * Work performed urier tbe auspices of U.S. Energy Research and Develo~,,\,!l'S ~~ois~st1oi? .. ' UI.:j ~ ,(Ial l 110. 1 ,ur ,U'.I~' t..U
45506633
The superconducting solenoid magnets for MICE
The Muon Ionization Cooling Experiment (MICE) is a channel of superconducting solenoid magnets. The magnets in MICE are around the RF cavities, absorbers (liquid or solid) and the primary particle detectors [1], [2]. The MICE superconducting solenoid system consists of eighteen coils that are grouped in three types of magnet assemblies. The cooling channel consists of two complete cell of an SFOFO cooling channel. Each cell consists of a focusing coil pair around an absorber and a coupling coil around a RF cavity that re-accelerates the muons to their original momentum. At the ends of the experiment are uniform field solenoids for the particle detectors and a set of matching coils used to match the muon beam to the cooling cells. Three absorbers are used instead of two in order to shield the detectors from dark currents generated by the RF cavities at high operating acceleration gradients.