Experimental demonstration of fusion-relevant conditions in magnetized liner inertial fusion.

This Letter presents results from the first fully integrated experiments testing the magnetized liner inertial fusion concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)], in which a cylinder of deuterium gas with a preimposed 10 Taxial magnetic field is heated by Z beamlet, a 2.5 kJ, 1 TW laser, and magnetically imploded by a 19 MA, 100 ns rise time current on the Z facility. Despite a predicted peak implosion velocity of only 70 km = s, the fuel reaches a stagnation temperature of approximately 3 keV, with T(e) ≈ T(i), and produces up to 2 x 10(12) thermonuclear deuterium-deuterium neutrons. X-ray emission indicates a hot fuel region with full width at half maximum ranging from 60 to 120 µm over a 6 mm height and lasting approximately 2 ns. Greater than 10(10) secondary deuterium-tritium neutrons were observed, indicating significant fuel magnetization given that the estimated radial areal density of the plasma is only 2 mg = cm(2).

Understanding fuel magnetization and mix using secondary nuclear reactions in magneto-inertial fusion.

Magnetizing the fuel in inertial confinement fusion relaxes ignition requirements by reducing thermal conductivity and changing the physics of burn product confinement. Diagnosing the level of fuel magnetization during burn is critical to understanding target performance in magneto-inertial fusion (MIF) implosions. In pure deuterium fusion plasma, 1.01 MeV tritons are emitted during deuterium-deuterium fusion and can undergo secondary deuterium-tritium reactions before exiting the fuel. Increasing the fuel magnetization elongates the path lengths through the fuel of some of the tritons, enhancing their probability of reaction. Based on this feature, a method to diagnose fuel magnetization using the ratio of overall deuterium-tritium to deuterium-deuterium neutron yields is developed. Analysis of anisotropies in the secondary neutron energy spectra further constrain the measurement. Secondary reactions also are shown to provide an upper bound for the volumetric fuel-pusher mix in MIF. The analysis is applied to recent MIF experiments [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z Pulsed Power Facility, indicating that significant magnetic confinement of charged burn products was achieved and suggesting a relatively low-mix environment. Both of these are essential features of future ignition-scale MIF designs.

Architecture, implementation, and testing of a multiple-shell gas injection system for high current implosions on the Z accelerator.

Tests are ongoing to conduct ~20 MA z-pinch implosions on the Z accelerator at Sandia National Laboratory using Ar, Kr, and D2 gas puffs as the imploding loads. The relatively high cost of operations on a machine of this scale imposes stringent requirements on the functionality, reliability, and safety of gas puff hardware. Here we describe the development of a prototype gas puff system including the multiple-shell nozzles, electromagnetic drivers for each nozzle's valve, a UV pre-ionizer, and an inductive isolator to isolate the ~2.4 MV machine voltage pulse present at the gas load from the necessary electrical and fluid connections made to the puff system from outside the Z vacuum chamber. This paper shows how the assembly couples to the overall Z system and presents data taken to validate the functionality of the overall system.

Is tubuloglomerular feedback a tool to prevent nephron oxygen deficiency?

The purpose of the study was to analyze whether rhythmic oscillations of proximal tubular pressure and distal fluid conductivity at the renal surface are induced by oxygen deficiency of thick ascending limb (TAL) segments. Oxygen pressure was measured in halothane anesthetized Munich-Wistar rats by a multi-wire micro-gold electrode at the kidney surface. Signals from wires placed upon glomeruli and tubuli exhibited pO2 oscillations with exactly the same frequency (in mean 30 mHz) as have been described for proximal tubular pressures or distal fluid conductivities. This supports our suggestion that a limited oxygen supply to the nephron forces TAL segments to oscillate between aerobic and anaerobic energy production. A switch to glycolysis reduces TAL's transport efficiency dramatically. At the macula densa, the terminal end of the TAL segment, the thereby elevated sodium concentration operates as a switch by means of the TGF to adapt the filtered load to the oxygen supply of the individual nephron. In this way proximal tubules may also be protected from oxygen deficiency, which is essential due to their low glycolytic capacity. An enhanced halothane concentration of 2% or the use of barbiturates, such as Inactin, blocks oscillations completely as furosemide blocks oscillations as well as the feedback response. Reduction of the hematocrit by exchange transfusion mainly reduces supratubular pO2 values, and to a lesser extent also reduces supraglomerular pressures. This demonstrates that oxygen shunt diffusion in the kidney cortex and medulla is a prerequisite for both the function of a sensor to measure pO2 and oxygen capacity to regulate erythropoietin secretion and to enable an effective adjustment of blood flow to the metabolic and functional demands of the kidney.

Use of the umbilical area for placement of a urinary stoma.

Children with myelodysplasia are best managed in medical centers by a team consisting of a urologist, an orthopedist, a neurosurgeon, a pediatrician, a social worker, an orthotic technician and physical therapists. A co-operative approach aids in the selection of a urinary diversion stoma site which will not interfere with the multiple orthopedic procedures these children must undergo. The urologic and orthopedic complications and benefits of 24 patients with umbilical stoma are compared with 24 patients with matched right lower quadrant stoma. The incidence of urologic complications is equal, while the orthopedic advantages manifest by the first group vastly outweigh the problems encountered in the second group. We advocate the use of a midline stoma site for urinary diversion in children with myelodysplasia.