35576414
The mechanical and thermal design for the MICE detector solenoid magnet system
The detector solenoid for MICE surrounds a scintillating fiber tracker that is used to analyze the muon beam within the detector. There are two detector magnets for measuring the beam emittance entering and leaving the cooling channel that forms the central part of the experiment. The field in the region of the fiber detectors must be from 2.8 to 4 T and uniform to better than 1 percent over a volume that is 300 mm in diameter by 1000 mm long. The portion of the detector magnet that is around the uniform field section of the magnet consists of two short end coils and a long center coil. In addition, in the direction of the MICE cooling channel, there are two additional coils that are used to match the muon beam in the cooling channel to the beam required for the detectors. Each detector magnet module, with its five coils, will have a design stored-energy of about 4 MJ. Each detector magnet is designed to be cooled using three 1.5 W coolers. This report presents the mechanical and electrical parameters for the detector magnet system.
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. >
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
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.
94844521
ACTIVE CENTER TAP QUENCH PROTECTION
120397444
The inclusion of fermions in dual N-point functions
Abstract Dual amplitudes of the five-point function for two fermions and three scalar bosons are constructed, and are used to obtain a consistent procedure for inclusing two fermions in the general N -point function.
15478688
The influence of world-sheet boundaries on critical closed string theory
Abstract This paper considers interactions between closed strings and open strings satisfying either Neumann or constant (point-like) Dirichlet boundary conditions in a BRST formalism in the critical dimension. With Neumann conditions this reproduces the well-known stringy version of the Higgs mechanism. With Dirichlet conditions the open-string states correspond to either auxiliary or Lagrange multiplier target-space fields and their coupling to the closed-string sector leads to constraints on the closed-string spectrum.
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.
1662741
D-brane interactions in type IIB plane-wave background
The cylinder diagrams that determine the static interactions between pairs of Dp-branes in the type IIB plane wave background are evaluated. The resulting expressions are elegant generalizations of the flat-space formulae that depend on the value of the Ramond-Ramond flux of the background in a non-trivial manner. If each of the interacting D-branes separately preserves half the supersymmetries, the closed-string and open-string descriptions consistently transform into each other under a modular transformation. These results are derived for configurations of euclidean signature D(p+1)-instantons but also generalize to lorentzian signature Dp-branes.
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.