9850713
A 20 T hybrid solenoid for the collection of pions for a muon collider
In order to generate intense muon beams for a muon collider, intense pion beams must be produced in a stationary proton beam target. The pions produced by the target must be captured before they can go through phase rotation and decay into muons. A 20 T solenoid with a clear bore of 150 mm can capture particles with a transverse momentum of 225 MeV/c or less. As the captured particles leave the capture solenoid, the magnetic induction is decreased to 5 T while the beam pipe diameter increases to 300 mm. Phase rotation of the pions and the decay of the pions to muons will occur at 5 T. The capture solenoid and the solenoids just downstream from the capture solenoid are subject to high heat loads (up to 4.8 MW) and radiation loads from the target. The conventional inner solenoid of the 20 T hybrid magnet system and the water cooled absorber will absorb virtually all of the particle energy from the target thus protecting the superconducting part of the solenoid system from excessive radiation heating. This report also describes the solenoid magnets from the capture zone to the solenoidal beam channel within the phase rotation RF cavities.
24392991
The Engineering Design of the 1.5 m Diameter Solenoid for the MICE RFCC Modules
The RF coupling coil (RFCC) module of MICE is where muons that have been cooled within the MICE absorber focus (AFC) modules are re-accelerated to their original longitudinal momentum. The RFCC module consists of four 201.25 MHz RF cavities in a 1.4 meter diameter vacuum vessel. The muons are kept within the RF cavities by the magnetic field generated by a superconducting coupling solenoid that goes around the RF cavities. The coupling solenoid will be cooled using a pair of 4 K pulse tube cooler that will generate 1.5 W of cooling at 4.2 K. The magnet will be powered using a 300 A two-quadrant power supply. This report describes the ICST engineering design of the coupling solenoid for MICE.
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. >
94844521
ACTIVE CENTER TAP QUENCH PROTECTION
123081787
PROGRESS ON THE SUPERCONDUCTING MAGNET FOR THE TIME PROJECTION CHAMBER EXPERIMENT (TPC) AT PEP
The TPC (Time Projection Chamber) experiment at PEP will have a two meter inside diameter superconducting magnet which creatests a 1.5 T uniform solenoidal field for the TPC. The superconducting magnet coil, cryostat, cooling system, and the TPC gas pressure vessel (which operatests at 11 atm) were designed to be about two thirds of a radiation length thick. As a result, a high current density coil design was chosen. The magnet is cooled by forced flow two phase helium. The TPC magnet is the largest adiabatically stable superconducting magnet built to date. The paper presents the parameters of the TPC thin solenoid and its subsystems. Tests results from the Spring 1980 cryogenic tes are presented. The topics to be dealt with in the paper are cryogenic services and the tests of magnet subsystems such as the folded current leads. Large thin superconducting magnet technology will be important to large detectors to be used on LEP.
118834673
A Design for a Combined Function Superconducting Dipole for a Muon Collider FFAG Accelerator
The acceleration stages for a muon collider require that the muons be accelerated within a given ring in fewer than twenty turns. One type of accelerator that appears to be attractive for a synchrotron that accelerates the muon a factor of four in energy in a few turns is the Fixed Field Alternating Gradient (FFAG) type of accelerator. As the energy of the muon beam increases, the muons move toward a higher field region of a DC combined function dipole. The following dipole and quadrupole magnet characteristics are required for a muon FFAG machine to be successful: (1) The dipole will be a fixed field dipole with an impressed quadrupole and sextupole field. There may or may not be separate quadrupoles that mayor may not have added sextupole windings. (2) The horizontal aperture of the required good field region is wider than the vertical aperture of the required good field region. (3) The magnet is relatively short, so that the conventional SSC type of superconducting dipole or quadrupole ends can not be used. The field at the end of the magnet must fall off abruptly within the distance of less than one vertical aperture. For a magnet that is 400more » mm long, the end region can be no more than 80 mm long. (4) The structure of the integrated field within the end region must be the same as the structure of the two-dimensional filed at the center of the magnet. A very preliminary design concept for a FFAG combined function dipole is presented in this paper.« less
119400372
Locality and currents for the dual string
Abstract We wish to describe the coupling of a local current to the dual string as the amplitude for the string to collapse to a point. At the quantum level we note that states which are localized in the transverse directions are forced by the gauge constraints to have longitudinal extension. The best we can do in the conventional model is, therefore, to construct off-shell states which have zero helicity (but no unique spin). We calculate the propagator for such states and compare it with the model of Schwarz. In their respective critical dimensions (26 for the string and 16 for the off-shell model of Schwarz) the two results become identical. We also calculate the Green functions for the coupling of one of our off-shell states to any number of on-shell particles by means of the functional formalism. Our results have a close connection with the previous models of Schwarz and Wu and of Corrigan and Fairlie.
16340985
D-brane Wess-Zumino actions, T-duality and the cosmological constant
Abstract A geometrical formulation of the T-duality rules for type II superstring Ramond-Ramond fields is presented. This is used to derive the Wess-Zumino terms in superstring D-brane actions, including terms proportional to the mass parameter of the IIA theory, thereby completing partial results in the literature. For non-abelian world-volume gauge groups the massive type IIA D-brane actions contain non-abelian Chern-Simons terms for the Born-Infeld gauge potential, implying a quantization of the IIA cosmological constant.
122251395
Average properties of dual resonances
Abstract As a consequence of the strong interaction (A.F.S.) scaling of dual amplitudes, we find that the average total width of a high mass resonance approaches a constant which is less than 1/π(GeV) 2 . We also obtain a logarithmic increase of the average multiplicity coming from the decay of dual resonances.
119238279
Modular properties of two-loop maximal supergravity and connections with string theory
The low-momentum expansion of the two-loop four-graviton scattering amplitude in eleven-dimensional supergravity compactified on a circle and a two-torus is considered up to terms of order S6 4 (where S is a Mandelstam invariant and is the linearized Weyl curvature). In the case of the toroidal compactification the coefficient of each term in the low energy expansion is generically a sum of a number of SL(2, )-invariant functions of the complex structure of the torus. Each such function satisfies a separate Poisson equation on moduli space with particular source terms that are bilinear in coefficients of lower order terms, consistent with qualitative arguments based on supersymmetry. Comparison is made with the low-energy expansion of type II string theories in ten and nine dimensions. Although the detailed behaviour of the string amplitude is not generally expected to be reproduced by supergravity perturbation theory to all orders, for the terms considered here we find agreement with direct results from string perturbation theory. These results point to a fascinating pattern of interrelated Poisson equations for the IIB coefficients at higher orders in the momentum expansion which may have a significance beyond the particular methods by which they were motivated.
2191534
Symmetry breaking at enhanced symmetry points
The influence of world-sheet boundary condensates on the toroidal compactification of bosonic string theories is considered. At the special points in the moduli space at which the closed-string theory possesses an enhanced unbroken G × G symmetry (where G is a semi-simple product of simply laced groups) a scalar boundary condensate parameterizes the coset G × G/G. Fluctuations around this background define an open-string generalization of the corresponding chiral nonlinear sigma model. Tree-level scattering amplitudes of on-shell massless states (‘pions’) reduce to the amplitudes of the principal chiral model for the group G in the low energy limit. Furthermore, the condition for the vanishing of the renormalization group beta function at one loop results in the familiar equation of motion for that model. The quantum corrections to the open-string theory generate a mixing of open and closed strings so that the coset-space pions mix with the closed-string G × G gauge fields, resulting in a Higgs-like breakdown of the symmetry to the diagonal G group. The case of non-oriented strings is also discussed.