118295670
Progress on Superconducting Magnets for the MICE Cooling Channel
MICE Note 274 Progress on the Superconducting Magnets for the MICE Cooling Channel M. A. Green a , S. P. Virostek a , D. Li a , M. S. Zisman a , L. Wang b , H. Pan b , H. Wu b , X. L. Guo b , F. Y. Xu b , X. K. Liu, S. X. Zheng b , T. Bradshaw c , D. E. Baynham c , J. Cobb d , W. Lau d , P. Lau d , and S. Q. Yang d , a) Lawrence Berkeley National Laboratory, Berkeley CA 94720, USA b) Institute of Cryogenic and Superconductivity Technology, HIT, Harbin, China c) Rutherford Appleton Laboratory, Chilton Didcot OX11-0QX, UK d) Physics Department Design Office, Oxford University, Oxford OX1-3RH, UK Corresponding Author: Michael A. Green at magreen@lbl.gov Abstract. The muon ionization cooling experiment (MICE) consists of a target, a beam line, a pion decay channel, the MICE cooling channel. Superconducting magnets are used in the pion decay channel and the MICE cooling channel. This report describes the MICE cooling channel magnets and the progress in the design and fabrication of these magnets. The MICE cooling channel consists of three types of superconducting solenoids; the spectrometer solenoids, the coupling solenoids and the focusing solenoids. The three types of magnets are being fabricated in the United States, China, and the United Kingdom respectively. The spectrometer magnets are used to analyze the muon beam before and after muon cooling. The coupling magnets couple the focusing sections and keep the muon beam contained within the iris of the RF cavities that are used to recover the muon momentum lost during ionization cooling. The focusing magnets focus the muon beam in the center of a liquid hydrogen absorber. The first of the cooling channel magnets will be operational in MICE in the spring of 2010. 1. Introduction to the MICE Cooling Channel The next generation of particle physics accelerators will involve the acceleration and collision of high- energy leptons. There are limits on how much the lowest mass stable lepton (electrons and positrons with a rest mass of 0.51 MeV) can be bent in a magnetic field. The next lowest mass lepton is the muon (rest mass ~100 MeV). High-energy muons can be bent without the synchrotron radiation that comes from bending electrons or positrons. Muons are produced from the decay of pions, which are produced when protons collide with a fixed target. Muons produced this way have a high emittance. The development of a neutrino factory or a muon collider requires that muon-beams be cooled (reducing their emittance by removing the transverse momentum while retaining the momentum in the direction of the beam). Because a muon has a short lifetime (~2.1 µs at rest), the methods used for cooling positrons and anti protons cannot be employed. The only method that can be applied that will cool muons within their lifetime is ionization cooling. Demonstrating muon ionization cooling is essential to the development of muon accelerators and storage rings [1], [2]. The muon ionization cooling experiment (MICE) is designed to demonstrate muon cooling in a magnet configuration that is useful for a neutrino factory [3], [4].
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.
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
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. >
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.
122366617
Ten-dimensional supersymmetric Yang-Mills theory with SO(8)-covariant light-cone superfields
Abstract The ten-dimensional supersymmetric Yang-Mills theory is formulated in terms of light-cone superfields that transform as vectors under the group of transverse Lorentz transformations (SO(8)). These superfields are constrained by a projection condition, which is solved explicitly. The superfield action is obtained by comparing its component expansion with the usual light-cone gauge component action.
119955549
Point-like structure and off-shell dual strings
Abstract We argue that in a consistent off-shell dual formalism the amplitude for the emission of a scalar off-shell state by a string consists of two components. One of these contains the particle poles in the off-shell leg and the other is intimately related to the insertion of a point-like energy density on the string. As a result, the amplitude for a string to emit a zero momentum scalar state into the vacuum (which may be relevant for spontaneous symmetry breaking) is described by the amplitude for a finite fraction of the energy in the string to collapse to a spatial point at some time (this fraction and its space-time position being integrated over). The off-shell amplitudes have an elegant formulation in terms of a set of “confined modes” which can be assigned quark flavour quantum numbers to reproduce the Chan-Paton scheme. We suggest the dual model be modified by allowing for the coupling of scalar closed strings to the vacuum and the resulting effect on the space-time structure of dual Green functions is described. We find that even the emission of a single zero-momentum closed string modifies the elastic amplitude in a significant manner, leading to a power-behaved fixed-angle cross section in contrast to the usual exponential decrease of the dual model. This arises from point-like scattering between energy densities accumulating in the colliding strings. The relationship between the fixed angle and Regge limits is discussed. The fixed angle behaviour is found to be the asymptotic limit in momentum transfer of a fixed pole that arises in the Regge limit.
125837974
The hexagon gauge anomaly in type 1 superstring theory
Abstract Hexagon diagrams with external on-mass-shell Yang-Mills gauge particles are investigated in type I superstring theory. Both the annulus and the Mobius-strip diagrams are shown to give anomalies, implying that spurious longitudinal modes cannot be consistently decoupled. However, the anomalies cancel when the two diagrams are added together if the gauge group is chosen to be SO(32). In carrying out the analysis, two different regulators are considered, but the same conclusions emerge in both cases. We point out where various terms in the low-energy effective action originate in superstring diagrams.
16315344
Connections between M-Theory and Superstrings
Many features of M-theory follow directly from the strong algebraic constraints associated with the symmetries of the theory rather than specific details of any microscopic model, such as the matrix model. Certain of these properties must be inevitable consequences of eleven-dimensional supersymmetry. Others may depend on assuming the validity of the intricate web of duality inter-relationships between the perturbative string theories.