112605859
The Phenix Detector magnet subsystem
The PHENIX [Photon Electron New Heavy Ion Experiment] Detector is one of two large detectors presently under construction for RHIC (Relativistic Heavy Ion Collider) located at Brookhaven National Laboratory. Its primary goal is to detect a new phase of matter; the quark-gluon plasma. In order to achieve this objective, the PHENIX Detector utilizes a complex magnet subsystem which is comprised of two large magnets identified as the Central Magnet (CM) and the Muon Magnet (MM). Muon Identifier steel is also included as part of this package. The entire magnet subsystem stands over 10 meters tall and weighs in excess of 1900 tons (see Fig. 1). Magnet size alone provided many technical challenges throughout the design and fabrication of the project. In addition, interaction with foreign collaborators provided the authors with new areas to address and problems to solve. Russian collaborators would fabricate a large fraction of the steel required and Japanese collaborators would supply the first coil. This paper will describe the overall design of the PHENIX magnet subsystem and discuss its present fabrication status.
118956013
Beam-dump/diagnostics box for a 10-kA 50-MeV, 50-ns electron beam
We have developed a dump for the ATA beam that consists of a series of carbon plates whose collective thickness totals approximately 1.5 ranges at 50 MeV. The energy dissipated in the plates is radiated to a water-cooled wall. The dump is designed to dissipate up to 175 kW of average power. A small hole along the axis of the plates forms a beamlet that passes through an energy analyzer. The analyzer consists of a 60/sup 0/ bending magnet and two high-sensitivity beam-current/position monitors. The ratio of the beamlet current to full current is used to estimate the beam emittance.
114809658
Magnet coil electrical gaskets of high compliance and ampacity
Coils employed in the magnets of the PHENIX Detector, presently under construction for RHIC (Relativistic Heavy Ion Collider) at the Brookhaven National Laboratory, are massive (weight {approximately} 8000 kG each). For that reason we subdivided them into a series of manageable subcoils that we will subsequent bolt together. Electrical terminals attached to the subcoils conductors are rigidly embedded and precisely located during vacuum impregnation. However; we anticipate some misalignment and nonuniform gaping to occur between terminals at assembly. We have elected to use electrical gaskets of compliance and ampacity between the bolted terminals to enhance the current carrying capability of the electrical joints. This paper describes the material candidates selected, the tests performed, and the relative ranking of the materials tested.
113304388
The PEP-II-Factory septum quadrupole magnets
The PEP-II B-Factory is presently engaged design and fabrication of several unique magnets referred to as septum quadrupoles. This family of magnets is required to contain a low energy beam of positrons (3.1 GeV) and a high energy electron beam (9.0 GeV) in adjacent beam pipes housed within a common magnet. One beam will be focused while the other passes through an almost field free region. To do this, an asymmetric magnet must be designed having a pure, high quality quadrupole field in the magnet aperture and an adjacent low field bypass channel. A current sheet or ``septum`` coil must be placed between these two regions to produce the desired magnetic results. Design of this high current density septum coil presents many challenges since space between the two vacuum beam pipes where the coil must reside is very limited. This paper will describe the overall design of the septum quadrupoles and the solutions employed to achieve the required magnetic performance.
120851342
A long electromagnetic wiggler for the PALADIN free-electron laser experiments
A report is presented of the design, fabrication, and testing of a 25.6-m-long wiggler for a free-electron-laser (FEL) experiment. It is a DC iron-core electromagnetic wiggler that incorporates a number of important and unique features: permanent magnets are used to suppress saturation in the iron and extend the linear operating range; steering-free excitation allows real-time adjustment of the field taper without causing beam steering; and wiggle-plane focusing is produced by curved pole tips. The magnitude of random pole-to-pole field errors is minimized by a mechanical design concept that reduces tolerance stackup in critical locations. Three five-meter sections of this wiggler design were tested individually, and when connected together the measurements show exceptionally low levels of random errors. Detailed analysis of the error distribution has shown that the errors are not truly random, and the net effect on steering is much less than would be expected from random errors of the same magnitude. Analysis is still in progress to identify the cause of this beneficial effect. >
123058959
Dark energy and the cosmological constant: a brief introduction
The recently observed acceleration of the expansion of the universe is a topic of intense interest. The favoured causes are the 'cosmological constant' or 'dark energy'. The former, which appears in the Einstein equations as the term λgμν, provides an extremely simple, well-defined mechanism for the acceleration. However, there is a school of thought that suggests that the cosmological constant is inadequate to explain fully the evolution of the universe and should be replaced by a slowly varying scalar field—the aforementioned dark energy. The situation is complicated by the circumstance that the expression for the cosmological constant is precisely that of the zero-point energy of a quantum field, ogμν. This strongly suggests the two are related. There are several problems here. The calculated value of the various contributions to o may be as much as 120 orders of magnitude greater than the observed value of λ. How these contributions add up to so minute a quantity is a major part of what is commonly termed 'the cosmological constant problem'. Traces of dark energy have yet to be found. We review some of the history and problems associated with the concepts of the cosmological constant and dark energy, provide a brief review of the relevant cosmology and review possible candidates for dark energy.
122505813
Comment on Coleman's theory of gravitation
The similarity of Coleman's theory (see abstr. A66860 of 1971) to a special case of a class of theories presented by Papapetrou (1954) is discussed.
123501567
Bianchi IV metric with electromagnetic field
An exact solution of the Einstein equations with an electromagnetic field source and Bianchi IV symmetry is described. This solution possesses, in the limiting case of vanishing source tensor, a previously discovered vacuum metric.