122796888
Magnetic measurements at Lawrence Berkeley Laboratory
Recent magnetic measurement activities at LBL have been concentrated in two separate areas, electromagnets and permanent magnets for the Advanced Light Source (ALS), and superconducting magnets for the Superconducting Super Collider Laboratory (SSCL). A survey of the many different measurement systems is presented. These include AC magnetic measurements of an ALS booster dipole engineering model magnet, dipole moment measurements of permanent magnet blocks for ALS wigglers and undulators, permeability measurements of samples destined for wiggler and undulator poles, harmonic error analysis of SSC one-meter model dipoles and quadrupoles and five-meter long SSC prototype quadrupoles, harmonic error analysis of ALS dipoles, quadrupoles, and sextupoles, precision Hall probe mapping of ALS storage ring combined function magnets, and the design of the ALS insertion device magnetic mapping system. A Unix-based data acquisition system that is being developed for the SSC is also described. Probes used for magnetic measurements include Helmholtz coils, integral coils, point coils, bucking harmonic analysis coils, several different types of Hall probes, and nuclear magnetic resonance magnetometers. >
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. >
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.
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.
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
94844521
ACTIVE CENTER TAP QUENCH PROTECTION
16813327
Light cone supersymmetry and d-branes
Abstract D-brane boundary states for type II superstrings are constructed by enforcing the conditions that preserve half of the space-time supersymmetry. A light-cone coordinate frame is used where time is identified as one of the coordinates transverse to the brane's (euclidean) world-volume so that the p -brane is treated as a ( p + 1)-instanton. The boundary states have the superspace interpretation of top or bottom states in a light-cone string superfield. The presence of a non-trivial open-string boundary condensate give rise to the familiar D-brane source terms that determine the (linearized) Born-Infeld-like effective actions for p -branes and the (linearized) equations of motion for the massless fields implied by the usual p -brane ansatze. The ‘energy’ due to closed string exchange between separate D-branes is calculated (to lowest order in the string coupling) in situations with pairs of parallel, intersecting as well as orthogonal branes - in which case the unbroken supersymmetry may be reduced. Configurations of more than two branes are also considered in situations in which the supersymmetry is reduced to 1 8 or 1 16 of the full amount. The Ward identities resulting from the non-linearly realized broken space-time supersymmetry in the presence of a D-brane are also discussed.
34616942
Unification of forces and particles in superstring theories
Superstring field theories have emerged as potentially consistent quantum field theories that unify gravity with the other fundamental forces in an almost unique manner. They are based on the dynamics of string-like fundamental quanta rather than the point-like quanta of more familiar relativistic ‘point field theories’ such as Yang-Mills gauge theory or general relativity. In these theories the observed fundamental particles, such as the leptons and quarks, may arise as the ground states of a string. This amounts to a profound generalization of the conventional field theory framework.
120075255
The quantum mechanics of the gauge-invariant O(2) Heisenberg model
The two-dimensional gauge-invariant O(2) Heisenberg (classical X-Y) model is discussed in terms of a Hamiltonian formulation on a one-dimensional spatial lattice with continuous “time”. Particular emphasis is placed on the spectrum of the model and the behaviour of the Wilson loop (which is relevant to the confinement properties). The entire energy spectrum as well as the eigenfunctions of the model are determined in a certain coupling regime by applying a WKB method suitable for periodic potentials. 
 
A tight binding (periodic Gaussian) approximation to the quantum Hamiltonian and its wave functional is introduced. The Wilson loop is explicitly calculated in terms of this approximation and is seen to be crucially influenced by the periodicity of the wave functional. The dominant contributions to be Wilson loop correspond to cross sections through the centres of vortices.
108681531
A 2-MeV microwave thermionic gun
A high-gradient, S-band microwave gun with a thermionic cathode is being developed in a collaborative effort by AET, Varian, and SSRL. A prototype design using an upgraded Varian dispenser cathode mounted with thermal isolation directly in the first half-cell of a 1-1/2 cell, side-coupled, standing-wave cavity has been fabricated and is being tested. Optimization of the cavity shape and beam formation was done using SUPERFISH, MASK, and PARMELA. An overview of design details, as well as the status of in-progress beam tests, will be presented. 9 refs., 6 figs.
124124262
SUPERSTRINGS AND THE UNIFICATION OF THE PHYSICAL FORCES