21404619
The Cold Mass Support System and the Helium Cooling System for the MICE Focusing Solenoid
The heart of the absorber focus coil (AFC) module for the muon ionization cooling experiment (MICE) is the two-coil superconducting solenoid that surrounds the muon absorber. The superconducting magnet focuses the muons that are cooled using ionization cooling, in order to improve the efficiency of cooling. The coils of the magnet may either be run in the solenoid mode (both coils operate at the same polarity) or the gradient (the coils operate at opposite polarity). The AFC magnet cold mass support system is designed to carry a longitudinal force up to 700 kN. The AFC module will be cooled using three pulse tube coolers that produce 1.5 W of cooling at 4.2 K. One of the coolers will be used to cool the liquid (hydrogen or helium) absorber used for ionization cooling. The other two coolers will cool the superconducting solenoid. This report will describe the MICE AFC magnet. The cold mass supports will be discussed. The reasons for using a pulsed tube cooler to cool this superconducting magnet will also be discussed.
94844521
ACTIVE CENTER TAP QUENCH PROTECTION
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.
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. >
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.
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.
123010874
Production of the new resonances in hadronic collisions
SummaryThe variation with energy and with Feynman’s variablex of the production of ψ and ψ’ is a sensitive test of their production mechanism. A simple parton model predicts that at relatively low energies production nearx=0 is strongly favoured and that the invariant crosssection atx=0 increases by two orders of magnitude between BNL and ISR energies. A sharp increase is also predicted for the ratio of ψ or ψ’ production to the nonresonant lepton pair background.RiassuntoLa variazione della produzione di ψ e ψ’ con l’energia e con la variabilex di Feynman è un test sensibile del loro meccanismo di produzione. Un semplice modello a partoni predice che ad energie relativamente basse la produzione pressox=0 è fortemente favorita e che la sezione d’urto adx=0 aumenta di due ordini di grandezza fra la energia del BNL e quella degli ISR. Si predice anche un netto incremento per il rapporto tra la produzione di ψ o ψ’ e il fondo di coppie leptoniche non risonante.
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.
120490134
Pomeron couplings in the presence of Reggeon loops
Abstract We examine the effect of reggeon loop corrections to the five-point function in the double-Regge limit. Using the Gribov reggeon calculus we first discuss the reggeon triangle insertion in the double-Regge pole vertex. This is seen to give rise to an inverse square root branch point in the plane of the azimuthal angle. Making specific smoothness assumptions we obtain constraints that require the vanishing of certain triple-Regge vertices. We discuss possible implications for the Brower-Weis decoupling theorem.