Point-Source Helicity Injection Current Drive System for the Pegasus Toroidal Experiment

Recent Pegasus experiments are developing solenoid-free startup techniques using point-source magnetic helicity injection. These plasma sources, called “plasma guns”, ionize a stream of gas in a discharge channel, and bias this channel with respect to an external electrode, driving current along the plasma stream, which relaxes into a tokamak-like equilibrium. The relaxed discharges formed by these injectors exhibit high current amplification, which is the ratio of total toroidal current to the gun-driven current. The development and present design of these injectors are described, and time traces from a typical discharge are presented.     

The dynomak: An advanced spheromak reactor concept with imposed-dynamo current drive and next-generation nuclear power technologies

A high-β spheromak reactor concept has been formulated with an estimated overnight capital cost that is competitive with conventional power sources. This reactor concept utilizes recently discovered imposed-dynamo current drive (IDCD) and a molten salt (FLiBe) blanket system for first wall cooling, neutron moderation and tritium breeding. Currently available materials and ITER-developed cryogenic pumping systems were implemented in this concept from the basis of technological feasibility. A tritium breeding ratio (TBR) of greater than 1.1 has been calculated using a Monte Carlo N-Particle (MCNP5) neutron transport simulation. High temperature superconducting tapes (YBCO) were used for the equilibrium coil set, substantially reducing the recirculating power fraction when compared to previous spheromak reactor studies. Using zirconium hydride for neutron shielding, a limiting equilibrium coil lifetime of at least thirty full-power years has been achieved. The primary FLiBe loop was coupled to a supercritical carbon dioxide Brayton cycle due to attractive economics and high thermal efficiencies. With these advancements, an electrical output of 1000 MW from a thermal output of 2486 MW was achieved, yielding an overall plant efficiency of approximately 40%.     

Dendrimers with Attached Helical Peptides

The attachment of peptides to the surface of spherical dendrimers via graft polymerization is described here (see Figure). It is shown that the resulting peptide dendrimers display greatly enhanced helicity compared to non‐dendrimer‐based analogues. This effect is attributed to aggregation of peptide segments on the dendrimer surface.     

Development of Amphipathic Antimicrobial Peptide Foldamers Based on Magainin 2 Sequence

Magainin 2 ( Mag 2 ), which is isolated from the skin of frogs, is a representative antimicrobial peptide (AMP), exerts its antimicrobial activity via microbial membrane disruption. It has been reported that both the amphipathicity and helical structure of Mag 2 play an important role in its antimicrobial activity. In this study, we revealed that the sequence of 17 amino acid residues in Mag 2 (peptide 7 ) is required to exert sufficient activity. We also designed a set of Mag 2 derivatives, based on enhancement of helicity and/or amphipathicity, by incorporation of α,α-disubstituted amino acid residues into the Mag 2 fragment, and evaluated their preferred secondary structures and their antimicrobial activities against both Gram-positive and Gram-negative bacteria. As a result, peptide 11 formed a stable helical structure in solution, and possessed potent antimicrobial activities against both Gram-positive and Gram-negative bacteria without significant cytotoxicity.     

Internal Fields in Helicity Injected Torus with Steady Inductive Helicity Injection (HIT-SI) Discharges

The Helicity Injected Torus with Steady Inductive Helicity Injection (HIT-SI) consists of an axisymmetric flux conserver and two half-torus magnetic helicity injectors, mounted on either side of the axisymmetric confinement region (Jarboe et al., 2006, Phys. Rev. Lett., 97, 115003). Current and flux are driven sinusoidally with time in each injector, injecting both power and magnetic helicity into the HIT-SI device, with the goal of forming and sustaining a spheromak in the confinement region. Recent HIT-SI results include formation of discharges with toroidal spheromak current 1.5 times the injector current amplitude, development of a Taylor-state model for the magnetic fields in HIT-SI discharges, and direct measurement of the portion of the induced injector electric field that drives current in the confinement region.     

CAMORRA: A C++ library for recursive computation of particle scattering amplitudes

We present a new Monte Carlo tool that computes full tree-level matrix elements in high-energy physics. The program accepts user-defined models and has no restrictions on the process multiplicity. To achieve acceptable performance, CAMORRA evaluates the matrix elements in a recursive way by combining off-shell currents. Furthermore, CAMORRA can be used to compute amplitudes involving continuous color and helicity final states.

Program summary

Program title: CAMORRACatalogue identifier: AEHN_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHN_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: GPL version 2No. of lines in distributed program, including test data, etc.: 252 572No. of bytes in distributed program, including test data, etc.: 1 711 469Distribution format: tar.gzProgramming language: C++Computer: AllOperating system: Tested on Linux and Mac OS, but should work on any systemClassification: 4.4Nature of problem: Current recursive matrix element computation programs are confined to standard model amplitudes, whereas many new physics signatures and backgrounds at hadron colliders are associated with multi-parton final states.Solution method: The library applies the Berends–Giele/Caravaglios–Moretti recursive algorithm in a generic way applicable to a wide range of quantum field theories. It allows the user to define a new physics model and consequently compute its predicted scattering amplitudes with exponential growth of the computing time with process multiplicity rather than factorial growth.Restrictions: There are no built-in restrictions on process complexity.Unusual features: CAMORRA can cope with Majorana fermions.Running time: A ten-gluon amplitude typically takes 9 ms per event.