119655108
The effect of muon decay on the design of dipoles and quadrupoles for a muon collider
The decay of muons to neutrinos and electrons can cause heating in the superconducting dipoles and quadrupoles in the muon collider acceleration rings and the colliding beam ring. The problem is particularly acute in the colliding beam ring where heating in the magnets can be as high as 2.4 kW per meter in the bending magnets of muon collider ring with 2 TeV mu plus and mu minus beams with 2.22×1012 particles per bunch at a repetition rate of 30 Hz. The energy deposited within the helium temperature region must be reduced at least three orders of magnitude in order for the refrigeration system to begin to keep up with the heat load. Beam heating from muon decay will require changes in dipole design from the traditional cosine theta (or intersecting ellipse) design used in the SSC magnets. Some dipole and quadrupole design options are presented in this report for both the accelerator rings and the colliding beam rings.
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.
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. >
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
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.
121636206
DUALITY AND DIFFRACTION DISSOCIATION
We discuss diffraction dissociation in the context of a dual model. We show how direct-channel resonances in the Pomeranchukon-particle amplitude build the Pomeranchukon in the crossed channel. A result of the enforcement of the Harari-Freund conjecture for particle-particle amplitudes is that the Pomeranchukon-Pomeranchukon-Reggeon coupling is small. The model is tested phenomenologically by the analysis of ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}p({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})$ of Lipes, Robertson, and Zweig and by baryon missing-mass data at various energies. It is also tested phenomenologically by the behavior of missing-mass diffraction production peaks, which are predicted to level off or dip near the forward direction as a consequence of the vanishing of the triple-Pomeranchukon coupling.
126329025
Superstrings Tie Up the Physical Forces
Progress towards understanding the three nongravitational forces – the strong, electromagnetic and weak forces – has been rapid over the last 20 years. The electromagnetic and weak forces are now understood as different aspects of the same force, related by a symmetry not seen in low energy experiments but becoming apparent at high energy.
2191534
Symmetry breaking at enhanced symmetry points
The influence of world-sheet boundary condensates on the toroidal compactification of bosonic string theories is considered. At the special points in the moduli space at which the closed-string theory possesses an enhanced unbroken G × G symmetry (where G is a semi-simple product of simply laced groups) a scalar boundary condensate parameterizes the coset G × G/G. Fluctuations around this background define an open-string generalization of the corresponding chiral nonlinear sigma model. Tree-level scattering amplitudes of on-shell massless states (‘pions’) reduce to the amplitudes of the principal chiral model for the group G in the low energy limit. Furthermore, the condition for the vanishing of the renormalization group beta function at one loop results in the familiar equation of motion for that model. The quantum corrections to the open-string theory generate a mixing of open and closed strings so that the coset-space pions mix with the closed-string G × G gauge fields, resulting in a Higgs-like breakdown of the symmetry to the diagonal G group. The case of non-oriented strings is also discussed.
119025667
Quantum Corrections to Eleven-Dimensional Supergravity