SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 14 - JULY 18, 2006

73 NUCLEAR PHYSICS
Includes nuclear particles; and reactor theory.

For space radiation see 93 Space Radiation.

For atomic and molecular physics see 72 Atomic and Molecular Physics.

For elementary particle physics see 77 Physics of Elementary Particles and Fields.

For nuclear astrophysics see 90 Astrophysics.

20060019349 Academy of Sciences (USSR), Moscow, Russian Federation

Stochastic Simulation of Thermoemission from Surfaces of Dusty Grains

Bondareva, A L; Levchenko, V D; Zmievskaya, G I; Jul 13, 2005; 5 pp.; In English; Original contains color illustrations Report No.(s): AD-A446115; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446115;Avail.: CASI: A01, Hardcopy

The thermoemission from dusty grain surfaces is necessary to take into account when processes in dusty plasma are simulated. The thermoemission of electrons can change temperature of electron part of plasma, typical electron velocity and other plasma properties. The kinetic distribution functions of secondary electrons from velocity and distance from dusty grain are calculated. DTIC

Dust; Electron Emission; Simulation; Stochastic Processes

20060019354 Sandia National Labs., Albuquerque, NM USA

Z-Pinch Plasma Neutron Sources

Velikovich, A L; Clark, R W; Davis, J; Chono, Y K; Deeney, C; Coverdale, C A; Ruiz, C; Cooper, G; Franklin, J; Rudakov, L I; Mar 24, 2006; 54 pp.; In English Contract(s)/Grant(s): DE-AC04-94-AL85000; Proj-2480M Report No.(s): AD-A446151; NRL/MR/6720--06-8927; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446151; Avail.: CASI: A04, Hardcopy

Adeuterium gas-puff load imploded by a multi-MA current driver, from a large initial diameter could be a powerful source of fusion neutrons, a plasma neutron source. Unlike the beam-target neutrons produced in Z-pinch plasmas in the 1950s and deuterium-fiber experiments in the 1980s, the neutrons generated in deuterium gas-puffs, with current levels achieved in recent experiments on the SNL Z facility, could contain a substantial fraction of thermonuclear origin. For recent deuterium gas-puff shots on Z, our analytical estimates and 1-D and 2-D simulations predict thermal neutron yields ~5 * 10(exp 13), in fair agreement with the yields measured on Z. It is demonstrated that the hypothesis of a beam-target origin of the observed fusion neutrons implies a very high Z-pinch-driver-to- fast-ions energy transfer efficiency. 5 to 10%, which would make a multi-MA deuterium Z-pinch the most efficient light-ion accelerator. No matter what mechanism is eventually determined to be responsible for generating fusion neutrons in deuterium gas-puff shots on Z, the neutron yield is shown to scale as Y(sub m) ~I(exp4 sub) where is I(sub m) is the peak current of the pinch.

Theoretical estimates and numerical modeling of deuterium gas-puff implosions demonstrate that the yields of thermonuclear fusion neutrons that can be produced on ZR and the next generation machines are sufficiently high to make Plasma Neutron Sources (PNS) the most powerful, cost- and energy-efficient laboratory sources of 2.5 to 14MeV fusion neutron, just like Plasma Radiation Sources (PRS) are the most powerful sources of soft and keV x-rays. In particular, the predicted neutron-producing capability of PNS driven by ZR and ZX accelerators, from ~6 x 10(exp 16) to ~lO(exp 18) matches the projected capability of the NIF laser at thermonuclear energy gains of 1 and 20, respectively. DTIC

Deuterium; Neutron Sources; Neutrons; Nuclear Reactions; Plasmas (Physics); Zeta Pinch

20060019652 Air Force Inst. of Tech., Wright-Patterson AFB, OH USA

Design and Calibration of a X-Ray Millibeam

Silvers, Joseph W; Dec 2005; 136 pp.; In English Report No.(s): AD-A446550; AFIT-CI04-1772; No Copyright; Avail.: CASI: A07, Hardcopy

It has been generally accepted that genetic damage is caused by the deposition of energy within the nucleus of a cell, and the extent of this damage is approximately proportional to the absorbed dose (the linear no-threshold dose-response model).However, recent experiments have shown that genetic alterations, cell death or transformation can occur in cells that receive no direct radiation at all - the so-called bystander effect. The goal of this project was to convert a broad-beam Hewlett-Packard (HP) 43 855B Faxitron x-ray machine into a millibeam configuration that can target small sections of a cell culture dish with a precise dose of radiation. This millibeam provides novel capabilities for radiobiological studies into the mechanisms underlying bystander effects caused by x-rays, a low linear energy transfer (LET) radiation. Air kerma and absorbed dose calibration factors for the HP Faxitron were developed for use in Fricke dosimetry, parallel-plate ionization chambers, Lithium Fluoride thermoluminescent dosimetry (TLD), and EBT OafChromic film to characterize the spatial distribution and accuracy of the doses produced by the Faxitron.Anew film scanning and analysis technique was developed using an off-the-shelf Canon 995OF 16-bit transmission scanner and the free Image software from the National Institute of Health. A multi-layer shield composed of lead and steel was designed to convert the 26.035 cm Faxitron x-ray beam into a millibeam that targets 10 to 60% of the area on a 9-cm diameter cell culture dish. DTIC

Calibrating; Radiation Dosage; X Rays

Source: NASA