Collimation of deuterium / 3-helium fusion products for advanced spacecraft propulsion and power

Current space exploration has transpired through the use of chemical rockets, and they have served us well, but they have their limitations. Exploration of the outer solar system, Jupiter and beyond will most likely require a new generation of propulsion system. One potential technology class to provide spacecraft propulsion and power systems involve thermonuclear fusion plasma systems. In this class it is well accepted that d-He3 fusion is the most promising of the fuel candidates for spacecraft applications as the 14.7 MeV protons carry up to 80% of the total fusion power while ‘s have energies less than 4 MeV. The other minor fusion products from secondary d-d reactions consisting of 3He, n, p, and 3H also have energies less than 4 MeV. Furthermore there are two main fusion subsets namely, Magnetic Confinement Fusion devices and Inertial Electrostatic Confinement (or IEC) Fusion devices. Magnetic Confinement Fusion devices are characterized by complex geometries and prohibitive structural mass compromising spacecraft use at this stage of exploration. While generating energy from a lightweight and reliable fusion source is important, another critical issue is harnessing this energy into usable power and/or propulsion. IEC fusion is a method of fusion plasma confinement that uses a series of biased electrodes that accelerate a uniform spherical beam of ions into a hollow cathode typically comprised of a gridded structure with high transparency. The inertia of the imploding ion beam compresses the ions at the center of the cathode increasing the density to the point where fusion occurs. Since the velocity distributions of fusion particles in an IEC are essentially isotropic and carry no net momentum, a means of redirecting the velocity of the particles is necessary to efficiently extract energy and provide power or create thrust. There are classes of advanced fuel fusion reactions where direct-energy conversion based on electrostatically-biased collector plates is impossible due to potential limits, material structure limitations, and IEC geometry. Thermal conversion systems are also inefficient for this application. A method of converting the isotropic IEC into a collimated flow of fusion products solves these issues and allows direct energy conversion. An efficient traveling wave direct energy converter has been proposed and studied by Momota , Shu and further studied by evaluated with numerical simulations by Ishikawa and others. One of the conventional methods of collimating charged particles is to surround the particle source with an applied magnetic channel. Charged particles are trapped and move along the lines of flux. By introducing expanding lines of force gradually along the magnetic channel, the velocity component perpendicular to the lines of force is transferred to the parallel one. However, efficient operation of the IEC requires a null magnetic field at the core of the device. In order to achieve this, Momota and Miley have proposed a pair of magnetic coils anti-parallel to the magnetic channel creating a null hexapole magnetic field region necessary for the IEC fusion core. Numerically, collimation of 300 eV electrons without a stabilization coil was demonstrated to approach 95% at a profile corresponding to Vsolenoid = 20.0V, Ifloating = 2.78A, Isolenoid = 4.05A while collimation of electrons with stabilization coil present was demonstrated to reach 69% at a profile corresponding to Vsolenoid = 7.0V, Istab = 1.1A, Ifloating = 1.1A, Isolenoid = 1.45A. Experimentally, collimation of electrons with stabilization coil present was demonstrated experimentally to be 35% at 100 eV and reach a peak of 39.6% at 50eV with a profile corresponding to Vsolenoid = 7.0V, Istab = 1.1A, Ifloating = 1.1A, Isolenoid = 1.45A and collimation of 300 eV electrons without a stabilization coil was demonstrated to approach 49% at a profile corresponding to Vsolenoid = 20.0V, Ifloating = 2.78A, Isolenoid = 4.05A 6.4% of the 300eV electrons’ initial velocity is directed to the collector plates. The remaining electrons are trapped by the collimator’s magnetic field. These particles oscillate around the null field region several hundred times and eventually escape to the collector plates. At a solenoid voltage profile of 7 Volts, 100 eV electrons are collimated with wall and perpendicular component losses of 31%. Increasing the electron energy beyond 100 eV increases the wall losses by 25% at 300 eV. Ultimately it was determined that a field strength deriving from 9.5 MAT/m would be required to collimate 14.7 MeV fusion protons from d-3He fueled IEC fusion core. The concept of the proton collimator has been proven to be effective to transform an isotropic source into a collimated flow of particles ripe for direct energy conversion.

The interpersonal and mental health implications of the coherence of coming out narratives for a sample of gay men in committed romantic relationships

The coming out process has been conceptualized as a developmental imperative for those who will eventually accept their same-sex attractions. It is widely accepted that homophobia, heterosexism, and homonegativity are cultural realities that may complicate this developmental process for gay men. The current study views coming out as an extra-developmental life task that is at best a stressful event, and at worst traumatic when coming out results in the rupture of salient relationships with parents, siblings, and/or close friends. To date, the minority stress model (Meyer, 1995; 2003) has been utilized as an organizing framework for how to empirically examine external stressors and mental health disparities for lesbians, gay men, and bisexual individuals in the United States. The current study builds on this literature by focusing on the influence of how gay men make sense of and represent the coming out process in a semi-structured interview, more specifically, by examining the legacy of the coming out process on indicators of wellness. In a two-part process, this study first employs the framework well articulated in the adult attachment literature of coherence of narratives to explore both variation and implications of the coming out experience for a sample of gay men (n = 60) in romantic relationships (n = 30). In particular, this study employed constructs identified in the adult attachment literature, namely Preoccupied and Dismissing current state of mind, to code a Coming Out Interview (COI). In the present study current state of mind refers to the degree of coherent discourse produced about coming out experiences as relayed during the COI. Multilevel analyses tested the extent to which these COI dimensions, as revealed through an analysis of coming out narratives in the COI, were associated with relationship quality, including self-reported satisfaction and observed emotional tone in a standard laboratory interaction task and self-reported symptoms of psychopathology. In addition, multilevel analyses also assessed the Acceptance by primary relationship figures at the time of disclosure, as well as the degree of Outness at the time of the study. Results revealed that participant’s narratives on the COI varied with regard to Preoccupied and Dismissing current state of mind, suggesting that the AAI coding system provides a viable organizing framework for extracting meaning from coming out narratives as related to attachment relevant constructs. Multilevel modeling revealed construct validity of the attachment dimensions assessed via the COI; attachment (i.e., Preoccupied and Dismissing current state of mind) as assessed via the Adult Attachment Interview (AAI) was significantly correlated with the corresponding COI variables. These finding suggest both methodological and conceptual convergence between these two measures. However, with one exception, COI Preoccupied and Dismissing current state of mind did not predict relationship outcomes or self-reported internalizing and externalizing symptoms. However, further analyses revealed that the degree to which one is out to others moderated the relationship between COI Preoccupied and internalizing. Specifically, for those who were less out to others, there was a significant and positive relationship between Preoccupied current state of mind towards coming out and internalizing symptoms. In addition, the degree of perceived acceptance of sexual orientation by salient relationship figures at the time of disclosure emerged as a predictor of mental health. In particular, Acceptance was significantly negatively related to internalizing symptoms. Overall, the results offer preliminary support that gay men’s narratives do reflect variation as assessed by attachment dimensions and highlights the role of Acceptance by salient relationship figures at the time of disclosure. Still, for the most part, current state of mind towards coming out in this study was not associated with relationship quality and self-reported indicators of mental health. This finding may be a function of low statistical power given the modest sample size. However, the relationship between Preoccupied current state of mind and mental health (i.e., internalizing) appears to depend on degree of Outness. In addition, the response of primary relationships figures to coming out may be a relevant factor in shaping mental health outcomes for gay men. Limitations and suggestions for future research and clinical intervention are offered.