16197404
A gas of D-instantons
Abstract A D-instanton is a space-time event associated with world-sheet boundaries that contributes non-perturbative effects of order e −const. κ to closed-string amplitudes. Some properties of a gas of D-instantons are discussed in this paper.
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.
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.
121755839
PHASE CONTOURS AND BOOTSTRAPS. I.
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.
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.
36460570
Progress on the design and fabrication of the mice spectrometer solenoids
The Muon Ionization Cooling Experiment (MICE) will demonstrate ionization cooling in a short section of a realistic cooling channel using a muon beam at Rutherford Appleton Laboratory (RAL) in the UK. A five-coil, superconducting spectrometer solenoid magnet at each end of the cooling channel will provide a 4 T uniform field region for the scintillating fiber tracker within the magnet bore tubes. The tracker modules are used to measure the muon beam emittance as it enters and exits the cooling channel. The cold mass for the 400 mm warm bore magnet consists of two sections: a three-coil spectrometer magnet and a two-coil matching section that matches the uniform field of the solenoid into the MICE cooling channel. The spectrometer solenoid detailed design and analysis has been completed, and the fabrication of the magnets is well under way. The primary features of the spectrometer solenoid magnet and mechanical designs are presented along with a summary of key fabrication issues and photos of the construction.
122748175
Calculation of the pressure rise in the cooling tube of a two-phase cooling system during a quench of an indirectly cooled superconducting magnet
Large superconducting detector magnets are indirectly cooled with two-phase helium flowing in cooling tubes attached to the coil or its support structure. Large detector magnets often quench such that most of the magnet stored energy ends up as heat stored in the coil package. The time constant for energy deposition in the coil and support structure is often quite short. This paper presents a method for calculating the peak pressure rise in the magnet two-phase cooling tube during a magnet quench. A comparison of calculated peak pressure rise and measured pressure rise for the PEP-4 solenoid is presented in this report. >
111279616
Quench protection for a 2-MJ magnet
A superconducting solenoid with conductive bore tube has been used at energies up to 1.9-MJ to test various methods of quench protection. The methods all involve shifting the main coil current to the conductive bore tube and include (1) allowing the quench to evolve naturally, (2) interrupting the primary circuit while providing a varistor used as a shunt across the coil, and (3) turning the entire magnet normal by dumping a short pulse of current from a capacitor bank through the windings.
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.
122379741
The UCLA Phi Factory Detector, the Integration of Superconducting Compensation Solenoids and the Final Focus Interaction Region Quadrupoles
Abstract The proposed Phi Factory for the University of California at Los Angeles (UCLA) is a small 510 MeV electron-positron colliding beam storage ring with high luminosity (greater than 10 32 cm −2 s −1 ). In order to do high quality Phi physics, a particle detector system with a large solid angle (preferably greater than 98 percent) is required. Particle detection and analysis will be done within a 0.5 tesla solenoidal magnetic field. The solenoidal field within the detector causes coupling between beam oscillations in the horizontal and vertical directions. Therefore, compensation solenoids are required to keep the circulating particle beams from seeing the effects of the field from the main detector solenoid. Since high luminosity and a large solid angle are required, the detectors and a pair of compensation solenoids must be integrated with the final focus quadrupoles within the detector straight section. This report describes the design of two tapered, 0.5 tesla, superconducting compensation solenoids which must go around six rare earth permanent final focus quadrupoles or six superconducting quadrupoles on either side of the beam collision point. A cryogenic cooling system for these two solenoids, which will be coupled with the cooling system for the primary detector solenoid, is also described.