56376565
Superconducting Magnets for a Muon Collider
Superconducting Magnets for a Muon Collider Michael A. Green Ernest Orlando Lawrence Berkeley National Laboratory University of California Berkeley CA. 94720 The existence of a muon collider will be dependent on the use of superconducting magnets. Superconducting magnets for the µ - µ + collider will be found in the following locations: the π - π + capture system, the muon phase rotation system, the muon cooling system, the recirculating acceleration system, the collider ring, and the collider detector system. This report describes superconducting magnets for each of these sections except the detector. In addition to superconducting magnets, superconducting RF cavities will be found in the recirculating accelerator sections and the collider ring. The use of superconducting magnets is dictated by the need for high magnetic fields in order to reduce the length of various machine components. The performance of all of the superconducting magnets will be affected the energy deposited from muon decay products. 1 . INTRODUCTION The proposed muon collider[1-5] consists of the following components: 1) a 10 GeV proton source that generates about 1.5 x 10 1 5 protons per second, 2) a target section that produces and captures pions, 3) a section where the pions decay to muons that are phase rotated to compact bunch, 4) a muon cooling section where the muon emitance is reduced three orders of magnitude, 5) several rings to accelerate muons to 2 TeV, 6) the collider ring, and 7) the detector. Superconducting magnets will be found in all of these sections except for the proton source. This report describes the superconducting solenoids in the pion capture system around the target. A brief description of the solenoids needed in the phase rotation and the muon cooling sections is presented. Dipole and quadrupoles for the recirculating accelerator rings and the collider ring are also described. This report does not include any discussion about superconducting magnets that are part of the detector system around the collider collision point. A muon decays to two neutrinos and electron or positron (depending on the charge state of the original muon). Roughly forty percent of the muon energy ends up in the decay electron or positron. The energy in the electron or positron can be deposited in various parts of the muon collider and its subsystems. The problem of muon decay is at its worst in the collider ring, but it is a problem for superconducting magnets and RF cavities throughout the muon collider subsystems. Muons have a life time that is dictated by its energy. The mean life of a muon at rest is about 2.197 µs. At the collider full energy the of 2 TeV, the muons will have a mean life of 41.6 ms. This means that the repetition rate for the muon collider must be of the order of the muon life time in the collider ring if high colliding ring luminocities are to be maintained. In order to maintain a luminocity of 10 3 5 cm -2 s -1 in a collider ring with a ∫* of 3 mm at the collision point, over 1.2 x 10 1 4 muons per second must be created and stored in a ring with 7 T bending magnets. The collider ring must have two bunches (one of each charge state) of 2x10 1 2 muons per bunch at a repetition rate of 30 Hz in order to have the desired luminocity at the collision point. This work was performed with the support of the Office of High Energy and Nuclear Physics, United States Department of Energy under contract number DE-AC03-76SF00098.
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
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. >
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.
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.
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.
122046299
Duality Constraints on Inclusive Reactions. II. The Role of the Harari-Freund Conjecture
We present a scheme for the generalization of the two-component theory of Harari and Freund to multiparticle amplitudes and, in particular, to inclusive reactions. Our scheme is based on duality and borrows the terminology of dual perturbation theory but we do not restrict our generalizations to any specific model. We obtain a criterion for the absence of secondary (nonscaling) Regge contributions in inclusive reactions. We show how inclusive reactions may approach their limiting values from below, in contrast to total cross sections which always have positive secondary contributions. The scheme suggests a novel interpretation of diffraction dissociation which we discuss in a separate paper.
120524357
Point-like particles and off-shell supersymmetry algebras
Abstract The reparametrization invariant action, describing supersymmetric particles, is shown to have a non-local symmetry and consequently an enlarged, N = 2, supersymmetry invariance with a central charge. The construction of multiplets of states only involves physical operators - there are no auxiliary states in the theory, even though the supersymmetry algebra applies off-shell. The free field action is described in terms of superfields which are Clifford operators. Comments are made about analogous string theories.
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.
125092124
Quantum Gravity and Particle Physics