Operating Modes for Compulsator Based Electromagnetic Launcher Systems

The compensated pulsed alternator (compulsator) is a versatile power supply capable of interfacing with the electromagnetic launcher in various ways. The method that has been explored at length with several systems is the single phase option. Several variants of this option, some using advanced pulse shaping techniques, have been discussed in prior publications [I-3]. Besides this basic single pulse method of operating there are several other methods each with its pros and cons. The multi-phase option is discussed in this paper. Within the broad class of multi-phase systems there are further sub-classes, namely alternating current drive and unidirectional current drives. Thus the branching of these operating modes gives rise to a variety of operating modes. Each one of these operating modes is described and simulation results are presented.Center for Electromechanic

On the formation of a Hawking-radiation photosphere around microscopic black holes

We show that once a black hole surpasses some critical temperature $T_{crit}$, the emitted Hawking radiation interacts with itself and forms a nearly thermal photosphere. Using QED, we show that the dominant interactions are bremsstrahlung and electron-photon pair production, and we estimate $T_{crit} \sim m_{e}/\alpha^{5/2}$, which when calculated more precisely is found to be $T_{crit} \approx$45 GeV. The formation of the photosphere is purely a particle physics effect, and not a general relativistic effect, since the the photosphere forms roughly $\alpha^{-4}$ Schwarzschild radii away from the black hole. The temperature $T$ of the photosphere decreases with distance from the black hole, and the outer surface is determined by the constraint $T\sim m_{e}$ (for the QED case), since this is the point at which electrons and positrons annihilate, and the remaining photons free stream to infinity. Observational consequences are discussed, and it is found that, although the QED photosphere will not affect the Page-Hawking limits on primordial black holes, which is most important for 100MeV black holes, the inclusion of QCD interactions may significantly effect this limit, since for QCD we estimate $T_{crit}\sim \Lambda_{QCD}$. The photosphere greatly reduces possibility of observing individual black holes with temperatures greater than $T_{crit}$, since the high energy particles emitted from the black hole are processed through the photosphere to a lower energy, where the gamma ray background is much higher. The temperature of the plasma in the photosphere can be extremely high, and this offers interesting possibilities for processes such as symmetry restoration.Comment: Latex, 16 pages, 3 postscript figures, submitted to PRD. Also available at http://fnas08.fnal.gov

Lepton Flavour Violating Leptonic/Semileptonic Decays of Charged Leptons in the Minimal Supersymmetric Standard Model

We consider the leptonic and semileptonic (SL) lepton flavour violating (LFV) decays of the charged leptons in the minimal supersymmetric standard model (MSSM). The formalism for evaluation of branching fractions for the SL LFV charged-lepton decays with one or two pseudoscalar mesons, or one vector meson in the final state, is given. Previous amplitudes for the SL LFV charged-lepton decays in MSSM are improved, for instance the $\gamma$-penguin amplitude is corrected to assure the gauge invariance. The decays are studied not only in the model-independent formulation of the theory in the frame of MSSM, but also within the frame of the minimal supersymmetric SO(10) model within which the parameters of the MSSM are determined. The latter model gives predictions for the neutrino-Dirac Yukawa coupling matrix, once free parameters in the model are appropriately fixed to accommodate the recent neutrino oscillation data. Using this unambiguous neutrino-Dirac Yukawa couplings, we calculate the LFV leptonic and SL decay processes assuming the minimal supergravity scenario. A very detailed numerical analysis is done to constrain the MSSM parameters. Numerical results for SL LFV processes are given, for instance for tau -> e (mu) pi0, tau -> e (mu) eta, tau -> e (mu) eta', tau -> e (mu) rho0, tau -> e (mu) phi, tau -> e (mu) omega, etc.Comment: 36 pages, 3 tables, 5 .eps figure

Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration

Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (p_T), elliptic flow, two-particle correlations, non-statistical fluctuations, and suppression of particle production at high p_T. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted to Nuclear Physics A as a regular article; v3 has minor changes in response to referee comments. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Description of Pulsed Homopolar Generator Technologies for a Fusion Ignition Experiment

The concept for a single-turn tokamak experiment IGNITEX 1 makes possible the realization of a controlled, self-sustained fusion reaction in the near term with relative simplicity and low cost. The IGNITEX tokamak utilizes low-impedance toroidal field (TF) and poloidal field (PF) magnet systems which induce the high-level fields and currents required for fusion ignition. These magnet systems require power supplies that can meet strict operational conditions. Homopolar generators (HPGs) are well suited for operation of a single-turn tokamak because they are inherently high current, low voltage machines which can kinetically store all the energy required for a pulsed discharge. The energy storage is accomplished in a compact manner by using high speed composite flywheel technology and provides the added advantage of keeping electrical grid power requirements very low. Finally, since HPGs are simple de machines, their cost is low and rectifier systems are not necessary. In this paper, the HPG technologies to be utilized in a fusion ignition experiment are described. The various components, materials, and design considerations for the HPG current-collection systems are reviewed, including rotor slip ring, brushes, and actuators. Design, fabrication, and assembly techniques for the lightweight, composite, energy-storage flywheel are given. The status of these HPG technologies relative to IGNITEX power supply requirements are reviewed. The modes of operation of the TF and PF magnet systems are analyzed. Questions of reliability of operation, maintenance, and cost evaluation are also addressed. Finally, the construction and testing of a full-scale prototype IGNITEX HPG power supply module is proposed.Center for Electromechanic

A Study of Operating Modes for Compulsator Based EM Launcher Systems

The compensated pulsed alternator (compulsator) is a versatile power supply capable of interfacing with the electromagnetic launcher in various ways. The method that has been explored at length with several systems is the single phase option. Several variants of this option, some using advanced pulse shaping techniques, have been discussed in prior publications. Besides this basic single pulse method of operating there are several other methods each with its pros and cons. The multiphase option is discussed in this paper. Within the broad class of multi-phase systems there are further sub-classes, namely alternating current drive and unidirectional current drives. Thus the branching of these operating modes gives rise to a variety of operating modes. Each one of these operating modes is described and simulation results are presentedCenter for Electromechanic

Design of a homopolar generator power supply system for the IGNITEX experiment

Pulsed homopolar generator (HPG) power supplies are well suited for driving the single-turn coils of the Ignitex fusion experiment[1] because they are inherently low voltage DC machines capable of high output currents. Basic operation of an HPG is voltage generation across a conductive disk or drum rotating in 1 steady magnetic field. An electrical load is connected across the generated voltage through two sets of sliding electrical contacts or brushes. As pulsed energy stores, kinetic energy of the disk (rotor) is converted into an electrical pulse by the interaction of the armature current with the excitation field. For the Ignitex experiment, a total of 14.6 GJ are required for the 10 s total pulse length, 12 GJ for the toroidal field excitation and 2.6 GJ for the poloidal field coils. The toroidal field supply is composed of 12, one GJ modules each rated at 12.5 MA output current and an open circuit voltage of 30 V. Five generators are used to drive the poloidal fieldcoils. They have stored energies between 40 and 700 MJ each and output ratings from 8 HA at 60 V to 750 kA at 150 v. Pulse shaping for all the generators is accomplished by actively controlling the HPG excitation field during the discharge. Operation of the poloidal field system uses an underdamped coil/generator circuit to >ring> the total current from 22 to -15.7 MA. The Ignitex HPG power supplies use a combination of iron-core machine technology and relatively new composite energy storage flywheel developments. Ironcore HPG technology provides adequate voltage generation and extensively developed current collection techniques which can be used. For the 1 GJ machines, the brushes operate at a 200 11/s slip speed and a current density of 1.25 kA/cm2. These are below state of the art performance levels for pulsed HPGs. Composite flywheel technology allows the 1 GJ modules to be built compact enough to be placed close to the Ignitex coil system and provides a significant cost savings over steel flywheel energy storage. Flywheels for the generators are fiberglass/epoxy composite rims with 3.75 m outer diameters and 1 m axial lengths.Center for Electromechanic

Magnetic System for the Ignitex Fusion Ignition Experiment

Controlled D-T fusion in a tokamak device by ohmic heating alone can be realized with toroidal confinement fields between 15 and 20 T and plasma currents in the 12- to 15-MA range. These conditions are achieved in the IGNITEX concept [1,2) by using a single turn toroidal field coil designed for 20-T operation and a set of five, single turn poloidal field coil pairs located within the plasma bore of the 1.5 m major radius machine (0.5 m minor radius). Total pulse length for the experiment is 10 s, including a 5 s flat-top period. A single-turn configuration for the toroidal field coil was adopted to maximize load-carrying ability and virtually eliminate insulation problems. Peak current for 20-T operation is 150 MA which results in an average inner leg current density of 57 MA/m2, a relatively low value for the field produced. Support of the toroidal field coil includes axial preloading of the inner leg to a 469 MPa compressive stress with an externa 1 hydraulic press structure, a 234 MPa radial compressive preload applied at the top and bottom of the coil by two thermally fitted steel rings, and a 0.8 m diameter compression bar located in the coil central bore. The coil itself is housed in a cryostat for precooling to liquid nitrogen temperature to extend the usable temperature excursion. Time dependent finite element analysis of the single-turn coil indicates that a maximum von Mises stress of 531 MPa will occur in the inner leg region. The analysis also includes time evolution of temperature and current distribution within the coil as well as calculation of energy requirements. Peak temperature after the 10-s pulse will be less than 100°c. A dispersion strengthened copper alloy has been selected as the toroidal coil material for its excel lent combination of yield strength and conductivity, which are 582 MPa and 92% IACS, respectively. The material exhibits a high fatigue limit of 207 MPa. To demonstrate the operation of the single-turn coil at the 20-T level, a 1/6th scaled prototype is proposed using an existing 60 MJ, 9 MA six module hompolar generator (HPG) power supply located at the Center for Electromechanics at The University of Texas at Austin (CEM-UT).Center for Electromechanic

9 MJ/Pulse Air Core Compulsator

One of the most critical issues in taking electromagnetic gun technology from the laboratory to field applications is the compactness and portability of very high energy, pulsed power supplies. The air core compulsator which is under development at CEM-UT addresses these requirements. The rotor of this machine is made from fiber reinforced epoxy composites and spins at a tip speed of 500 m/s which is substantially higher than is possible with a ferromagnetic rotor. The higher tip speed greatly increases the energy density of the rotor thus reducing the size of the prime power source. The special structural features of this machine, the electrical design, and the cooling system design are discussed.Center for Electromechanic