scholarly journals Th232 (n,2n)Th231 CROSS SECTION FROM THRESHOLD TO 20.4 MEV

1961 ◽  
Vol 39 (3) ◽  
pp. 689-696 ◽  
Author(s):  
J. P. Butler ◽  
D. C. Santry
Keyword(s):  
Cross Section ◽  
Threshold Energy ◽  
Activation Method ◽  
Excitation Curve ◽  
Graaff Accelerator ◽  
A Value ◽  
Maximum Value ◽  
Van De Graaff

The excitation curve for the reaction Th232 (n,2n) Th231 has been measured by the activation method from the threshold energy, 6.34 Mev, to 20.4 Mev, relative to the known cross section for the S32 (n,p)P32 reaction. Monoenergetic neutrons were obtained from the D (d,n) He3 and T (d,n) He4 reactions employing a Tandem Van de Graaff accelerator. From threshold to 9.0 Mev, the (n,2n) cross section rises rapidly, reaching its maximum value of 1.88 ± 0.09 barns in the region of 9.5 to 11.0 Mev. Above 11.5 Mev the (n,2n) cross section decreases due to competition of the (n,3n) and (n,2nf) reactions and at 20.4 Mev it has a value of 0.225 ± 0.015 barns.

EXCITATION CURVES FOR THE REACTIONS Al27(n, α)Na24 AND Mg24(n, p)Na24

1963 ◽  
Vol 41 (2) ◽  
pp. 372-383 ◽  
Author(s):  
J. P. Butler ◽  
D. C. Santry
Keyword(s):  
Cross Section ◽  
Neutron Spectrum ◽  
Cross Sections ◽  
Effective Cross Section ◽  
Fission Neutron ◽  
Activation Method ◽  
Graaff Accelerator ◽  
Fission Neutron Spectrum ◽  
Van De Graaff ◽  
Threshold Energies

Excitation curves for the reactions Al27(n, α)Na24 and Mg24(n, p)Na24 have been measured by the activation method from near threshold energies to 20.3 Mev. The measurements are relative to the known cross section for the reaction S32(n, p)P32. Monoenergetic neutrons were obtained from the D(d, n)He3, T(d, n)He4, and the T(p, n)He3 reactions employing a Tandem Van de Graaff accelerator or 125-kev accelerator. Cross sections for both reactions rise above the minimum detectable value of 0.02 mb near 5 Mev and reach maximum values of 126 mb for the Al(n, α)Na24 reaction and 205 mb for the Mg24(n, p)Na24 reaction at 13.5 Mev. Above this energy both cross sections decrease. From the excitation curves effective cross-section values for a fission-neutron spectrum have been calculated as 0.61 ± 0.03 mb for the (n, α) reaction and 1.34 ± 0.07 mb for the (n, p) reaction.

Cross Section Measurements for the 103Rh(n,n′)103Rhm Reaction from 0.122 to 14.74 MeV

1974 ◽  
Vol 52 (15) ◽  
pp. 1421-1428 ◽  
Author(s):  
D. C. Santry ◽  
J. P. Butler
Keyword(s):  
Neutron Flux ◽  
Cross Section ◽  
Neutron Spectrum ◽  
Cross Sections ◽  
Energy Levels ◽  
Effective Cross Section ◽  
Fission Neutron ◽  
Activation Method ◽  
Excitation Curve ◽  
Fission Neutron Spectrum

Cross sections for the production of 103Rhm were measured by the activation method. At energies below 5.3 MeV the neutron flux was measured with a calibrated neutron long counter, while at higher energies, measurements were made relative to the known cross section for the 32S(n,p)32P reaction. The shape of the Rh excitation curve is discussed in terms of known energy levels in 103Rh. An effective cross section for a 235U fission neutron spectrum calculated from the measured excitation curve is 724 ± 43 mb.

FLOW OF GAS THROUGH A TUBE OF CONSTANT CROSS-SECTION WITH HEAT EXCHANGE THROUGH THE TUBE WALLS

1945 ◽  
Vol 23a (1) ◽  
pp. 1-11 ◽  
Author(s):  
B. Szczeniowski
Keyword(s):  
Heat Exchange ◽  
Cross Section ◽  
Stream Velocity ◽  
Constant Cross Section ◽  
Velocity Of Sound ◽  
Heat Conductance ◽  
A Value ◽  
Maximum Value ◽  
Theoretical Investigations ◽  
Present View

The influence of the exchange of heat between a gas flowing through a tube and the outside atmosphere on the pressure in the gas stream is usually overlooked. Theoretical investigations show, however, that this influence is marked in the case of large stream velocities, approximating the velocity of sound. In addition, the theory permits us to state that the heat exchange is possible only when the stream velocity is maintained beyond certain limits. For stream velocities within these limits, heat exchange is not possible.The conclusion is reached that the velocity of flow in the tube, if the tube is heated or cooled, shows a natural and permanent tendency to reach the velocity of sound, after which the heat exchange is no longer possible.Finally, this theoretical investigation shows that the present view that the heat conductance coefficient increases continually with the stream velocity is wrong. This coefficient will be equal to zero when the stream velocity reaches the velocity of sound. This means that it will reach a certain maximum value corresponding to a value of stream velocity which is not exactly known but which will be less than that of sound.

Cross sections for the 93Nb(n,2n)92mNb reaction

1990 ◽  
Vol 68 (7-8) ◽  
pp. 582-586 ◽  
Author(s):  
D. C. Santry ◽  
R. D. Werner
Keyword(s):  
Cross Section ◽  
Neutron Spectrum ◽  
Cross Sections ◽  
Threshold Energy ◽  
Effective Cross Section ◽  
Fission Neutron ◽  
Transfer Standard ◽  
Fission Neutron Spectrum ◽  
Maximum Value ◽  
The Cross

The cross section of the 93Nb(n,2n)92mNb reaction has been studied by use of the activation method from the threshold energy of 8.8–19.8 MeV. Measurements are relative to the known cross-section values for the reactions H(n,n)H, 32S(n,p)32p, and 27Al(n,α)24Na. The cross-section value increases smoothly with energy and reaches a maximum value of 444 ± 18 mb at about 14.5 MeV then decreases to values of 293 ± 14 mb at 19.8 MeV. An effective cross-section value for a fission neutron spectrum calculated from the results is 0.321 ± 0.019 mb. The activation of Nb as a transfer standard for 14 MeV neutrons is discussed.

THERMAL NEUTRON CAPTURE CROSS SECTION OF Ce142

1956 ◽  
Vol 34 (8) ◽  
pp. 1023-1026 ◽  
Author(s):  
L. P. Roy ◽  
L. Yaffe
Keyword(s):  
Thermal Neutron ◽  
Cross Section ◽  
Neutron Capture ◽  
Capture Cross Section ◽  
Activation Method ◽  
Thermal Neutron Capture ◽  
Capture Cross ◽  
Neutron Capture Cross Section ◽  
A Value ◽  
The Cross

The cross section of Ce142 has been determined by the activation method and found to be 0.95 ± 0.05 barns relative to a value of σCo59 = 36.3 barns. Disintegration rates were determined by a 4π counter. The value obtained agrees with that of Katcoff etal. (1949) also obtained by the activation method but differs markedly from that of Pomerance (1952).

scholarly journals The Origin of the Elements

2012 ◽  
Author(s):  
Shelley R. Lesher ◽  
A. Arend
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Neutron Capture ◽  
Recent Experiment ◽  
Nuclear Reactions ◽  
Astrophysical Interest ◽  
Graaff Accelerator ◽  
Unstable Nuclei ◽  
Van De Graaff ◽  
The Cross

There are about 35 nuclei found in nature, which are not susceptible to neutron capture and are explained by the p-process. The modeling for this process requires thousands of nuclear reactions involving both stable and unstable nuclei including (α,α), (α,p) and (α,γ) reactions. In a recent experiment, the cross section of the reaction 120Te(α,p)123I was measured in the energy range of astrophysical interest for the p-process. The α beam from the Notre Dame FN Tandem Van de Graaff accelerator bombarded highly enriched self-supporting 120Te targets and the γ-rays from the activated 123I was counted with a pair of Ge clover detectors in close geometry. 

Low-energy displacement damage and the effect on the AEM of Ceramics

1990 ◽  
Vol 48 (4) ◽  
pp. 822-823
Author(s):  
D. G. Howitt ◽  
D.L. Medlin ◽  
M. M. Cluckie
Keyword(s):  
Carbon Atom ◽  
Cross Section ◽  
High Voltage ◽  
Analytical Electron Microscopy ◽  
Threshold Energy ◽  
Ceramic Materials ◽  
Small Displacement ◽  
A Value ◽  
Beam Currents

The observation that the signal from light elements such as carbon, oxygen, and nitrogen decreases in strength with time is to be expected for displacement in ceramic materials at high voltage, not only because the momentum transfer from an electron is more favorable, but also because the lattices are often full of defects. Even though the sensitivities of these materials can be below that of close parked metals at high voltage, during analytical electron microscopy the beam currents are sufficiently intense that the effect can be substantial. The loss rates for the signal are however quite predictable in the early stages and need not interfere with quantitative assessments of composition.An example of the loss of carbon signal from titanium carbide is shown in Figure 1 and a determination of the overall cross-section for carbon loss at 100 keV indicates a value close to 0.3 barns. This is about the cross-section for carbon displacement at 20 eV which is a conservative estimate of the binding energy for carbon in the lattice. Early experiments on vanadium carbide (Venables, 1969) indicate a similar overall cross-section however the threshold energy for the electrons to induce the damage is about only 5 eV. These results are consistent with the transfer of about 5 eV from an incident electron inducing a very small displacement of the carbon atom, of the order of an interatomic distance, with a damage cross-section of about 200 barns. Since the process needs to be repeated several times before the carbon atom is lost from the specimen the measured cross-section is proportionality reduced.

EXCITATION CURVES FOR THE (n, 2n), (n, p), AND (n, nα) REACTIONS OF 65Cu

1966 ◽  
Vol 44 (5) ◽  
pp. 1183-1193 ◽  
Author(s):  
D. C. Santry ◽  
J. P. Butler
Keyword(s):  
Cross Section ◽  
Neutron Spectrum ◽  
Cross Sections ◽  
Effective Cross Section ◽  
Fission Neutron ◽  
A Value ◽  
Fission Neutron Spectrum ◽  
Maximum Value ◽  
Section Curve ◽  
Threshold Energies

Cross sections for the reactions 65Cu (n, 2n)64Cu, 65Cu(n, p)65Ni, and 65Cu(n, nα)61Co have been measured by the activation method from threshold energies up to 20.2 MeV. The measurements are relative to the known cross section for the reaction 32S(n, p)32P. The (n, 2n) cross-section curve increases smoothly with energy and reaches a maximum value of 1 085 ± 60 mb at about 18 MeV. The (n, p) reaction reaches a maximum value of 21.7 ± 1.2 mb at 13.9 MeV. The (n, nα) reaction has a minimum detectable value of 0.3 ± 0.1 mb near 14 MeV and increases to a value of 18.9 ± 0.9 mb at 19.8 MeV. Effective cross-section values for a fission-neutron spectrum calculated from these results are 0.251 ± 0.018 mb for the (n, 2n) reaction and 0.523 ± 0.030 mb for the (n, p) reaction.

Specimen Preparation of Near Surface Ion Irradiated Samples

1985 ◽  
Vol 43 ◽  
pp. 170-171
Author(s):  
K. F. Russell ◽  
L. L. Horton
Keyword(s):  
Radiation Damage ◽  
Heavy Ions ◽  
Target Material ◽  
Metal Alloys ◽  
Specimen Surface ◽  
Specimen Preparation ◽  
Particle Accelerators ◽  
Near Surface ◽  
Graaff Accelerator ◽  
Van De Graaff

Beams of heavy ions from particle accelerators are used to produce radiation damage in metal alloys. The damaged layer extends several microns below the surface of the specimen with the maximum damage and depth dependent upon the energy of the ions, type of ions, and target material. Using 4 MeV heavy ions from a Van de Graaff accelerator causes peak damage approximately 1 μm below the specimen surface. To study this area, it is necessary to remove a thickness of approximately 1 μm of damaged metal from the surface (referred to as “sectioning“) and to electropolish this region to electron transparency from the unirradiated surface (referred to as “backthinning“). We have developed electropolishing techniques to obtain electron transparent regions at any depth below the surface of a standard TEM disk. These techniques may be applied wherever TEM information is needed at a specific subsurface position.

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