Tissue dosage from a point source of fission neutrons in air

1969 ◽  
Vol 26 (6) ◽  
pp. 625-626
Author(s):  
I. V. Goryachev ◽  
�. I. Zeinalov ◽  
V. I. Kukhtebich ◽  
G. M. Obaturov ◽  
L. A. Trykov ◽  
...  
Keyword(s):  
Point Source ◽  
Fission Neutrons

A THEOREM ON NEUTRON MULTIPLICATION

1947 ◽  
Vol 25a (4) ◽  
pp. 276-292 ◽  
Author(s):  
G. Placzek ◽  
G. Volkoff
Keyword(s):  
Point Source ◽  
Asymptotic Form ◽  
Homogeneous Medium ◽  
Integral Form ◽  
Exact Expression ◽  
Neutron Distribution ◽  
Chain Reaction ◽  
Neutron Multiplication ◽  
Fission Neutrons ◽  
The Fourier Transform

The asymptotic behaviour of the neutron distribution due to a point source in an infinite homogeneous medium in which a convergent chain reaction (multiplication constant k<1) takes place is investigated without special assumptions about the properties of the medium and the mechanism of neutron diffusion. It is shown under very general assumptions that at large distances r from the point source the neutron distribution always has the form[Formula: see text]General expressions for the constants μ and A of this asymptotic form of the distribution are given for any k<1 in terms of the Fourier transform of the spatial distribution of primary fission neutrons. These expressions reduce to particularly simple form for (1 − k) << 1. The exact expression for the neutron distribution throughout the medium is given in integral form. Four special frequently occurring cases are discussed as illustrations of the general result.

Slowing Down Distribution of U235 Fission Neutrons from a Point Source in Light Water

1955 ◽  
Vol 26 (8) ◽  
pp. 1013-1017 ◽  
Author(s):  
J. E. Hill ◽  
L. D. Roberts ◽  
T. E. Fitch
Keyword(s):  
Point Source ◽  
Light Water ◽  
Slowing Down ◽  
U235 Fission ◽  
Fission Neutrons

Fine Structural Changes in the Microvasculature of the Mouse Pinna: Aging and Radiation Injury

1974 ◽  
Vol 32 ◽  
pp. 54-55
Author(s):  
S. Phyllis Steamer ◽  
Rosemarie L. Devine
Keyword(s):  
Structural Changes ◽  
Radiation Treatment ◽  
Arterial Stenosis ◽  
Ultrastructural Changes ◽  
Vascular Effects ◽  
Microvascular Changes ◽  
Surrounding Connective Tissue ◽  
Fission Neutrons ◽  
Total Body

The importance of radiation damage to the skin and its vasculature was recognized by the early radiologists. In more recent studies, vascular effects were shown to involve the endothelium as well as the surrounding connective tissue. Microvascular changes in the mouse pinna were studied in vivo and recorded photographically over a period of 12-18 months. Radiation treatment at 110 days of age was total body exposure to either 240 rad fission neutrons or 855 rad 60Co gamma rays. After in vivo observations in control and irradiated mice, animals were sacrificed for examination of changes in vascular fine structure. Vessels were selected from regions of specific interest that had been identified on photomicrographs. Prominent ultrastructural changes can be attributed to aging as well as to radiation treatment. Of principal concern were determinations of ultrastructural changes associated with venous dilatations, segmental arterial stenosis and tortuosities of both veins and arteries, effects that had been identified on the basis of light microscopic observations. Tortuosities and irregularly dilated vein segments were related to both aging and radiation changes but arterial stenosis was observed only in irradiated animals.

The Fine Structure of Irradiated Mouse Heart

1976 ◽  
Vol 34 ◽  
pp. 184-185
Author(s):  
Vivian V. Yang ◽  
S. Phyllis Stearner
Keyword(s):  
Microscopic Level ◽  
Ultrastructural Changes ◽  
Mouse Heart ◽  
Blood Vessel Wall ◽  
Histopathological Changes ◽  
Light Microscopic Level ◽  
Γ Rays ◽  
Fission Neutrons ◽  
Total Body

The heart is generally considered a radioresistant organ, and has received relatively little study after total-body irradiation with doses below the acutely lethal range. Some late damage in the irradiated heart has been described at the light microscopic level. However, since the dimensions of many important structures of the blood vessel wall are submicroscopic, investigators have turned to the electron microscope for adequate visualization of histopathological changes. Our studies are designed to evaluate ultrastructural changes in the mouse heart, particularly in the capillaries and muscle fibers, for 18 months after total-body exposure, and to compare the effects of 240 rad fission neutrons and 788 rad 60Co γ-rays.Three animals from each irradiated group and three control mice were sacrificed by ether inhalation at 4 days, and at 1, 3, 6, 12, and 18 months after irradiation. The thorax was opened and the heart was fixed briefly in situwith Karnofsky's fixative.

XRMF applications of a monolithic, polycapillary, focusing x-ray optic

1996 ◽  
Vol 54 ◽  
pp. 240-241
Author(s):  
D. A. Carpenter ◽  
Ning Gao ◽  
G. J. Havrilla
Keyword(s):  
Trace Elements ◽  
Point Source ◽  
Focal Spot ◽  
Fluorescence Analysis ◽  
X Rays ◽  
Focal Distance ◽  
Spot Diameter ◽  
X Ray ◽  
Focal Spot Diameter

A monolithic, polycapillary, x-ray optic was adapted to a laboratory-based x-ray microprobe to evaluate the potential of the optic for x-ray micro fluorescence analysis. The polycapillary was capable of collecting x-rays over a 6 degree angle from a point source and focusing them to a spot approximately 40 µm diameter. The high intensities expected from this capillary should be useful for determining and mapping minor to trace elements in materials. Fig. 1 shows a sketch of the capillary with important dimensions.The microprobe had previously been used with straight and with tapered monocapillaries. Alignment of the monocapillaries with the focal spot was accomplished by electromagnetically scanning the focal spot over the beveled anode. With the polycapillary it was also necessary to manually adjust the distance between the focal spot and the polycapillary.The focal distance and focal spot diameter of the polycapillary were determined from a series of edge scans.

STUDIES OF PHOTONUCLEAR REACTIONS AND PHOTON ACTIVATION ANALYSIS IN THE GIANT DIPOLE RESONANCE REGION USING MICROTRONS

2007 ◽  
Vol 14 (1) ◽  
pp. 42 ◽  
Author(s):  
TRAN DUC THIEP ◽  
NGUYEN VAN DO ◽  
NGUYEN KHAC THI ◽  
TRUONG THI AN ◽  
NGUYEN NGOC SON
Keyword(s):  
Activation Analysis ◽  
Giant Dipole Resonance ◽  
Resonance Region ◽  
Photon Activation Analysis ◽  
Photon Flux ◽  
Photon Activation ◽  
Applied Physics ◽  
Dipole Resonance ◽  
Giant Dipole Resonance Region ◽  
Fission Neutrons

Mictrorons are accelerators of electrons and are simultaneous sources of bremsstrahlung photon flux and fission neutrons. In 1982, a microtron of seventeen trajectories Microtron MT - 17 was put into operation at the National Institute of Physics of Vietnam. Though very modest, microtons are very useful for developing countries such as Vietnam in both fundamental and applied physics research. During the recent years by using the above mentioned MT - 17 and microtrons from other institutes we have carried out different investigations. In this report we present some results obtained in the studies of photonuclear reactions and photon activation analysis in the giant dipole resonance region.

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