Measurement of neutron cross sections and resonance parameters of ~(169)Tm below 100 eV
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The neutron total cross-sections of thulium(169Tm) were measured in the neutron energy region from 0.01 eV to 100 eV by using the time-of-flight method at the Pohang Neutron Facility,which consists of an electron linac,a water-cooled tantalum target with a water moderator,and a 12 m time of flight path.Two thulium plates with different thicknesses were used for the neutron transmission measurement.The background level was determined by using a notch-filter of Co,In,and Cd sheets.The present measurement was compared with the previous ones,and a new set of resonance parameters of 169Tm isotope was obtained from the transmission rate by using the SAMMY code,with a comparison with the recommended parameters by Mughabghab.Keywords:
Thulium
Neutron Transport
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Neutron induced thermal cross-section of naturally occurring Tantalum (Ta) has been analyzed by using four different Ta samples with thickness 4.0, 2.0, 1.0 and 0.5 mm (respectively equivalent to 0.0224, 0.0111, 0.0055, and 0.0025 atoms/barn) at the Pohang Neutron Facility, Republic of Korea. The PNF consists of a 100 MeV electron linear accelerator (LINAC), a water cooled Tantalum (Ta) target, 12.06 m TOF path length, four position automatic sample changer controlled remotely by the CAMAC data acquisitions systems, and a 6LiZnS(Ag) inorganic scintillator as a neutron detector. The distance from the water cooled Ta target to the sample changer is 5.4 m. To reduce the gamma flash originated from the neutron target we have employed a neutron-gamma separation system based on their different pulse shape. The samples were highly pure (~99.9 %). In order to estimate the background and also to calibrate the energy we used notch filter of Cobalt (Co), Indium (In), and Cadmium (Cd) that has a large resonance peaks within our analyzed energy region. The area of the each samples of notch filter was 100 Ã 100 mm, and the thickness were 0.5 mm for Co and Cd; and 0.2 mm for the In. To get more events, experiments were done around 110 hours. The unwanted events were deleted from the real events by fitting with black resonances events of notch filter. The weighted mean of the measured thermal total neutron cross-section of Ta was compared with the existing experimental as well as evaluated nuclear data files.
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AbstractThe total neutron cross section of Pu240 has been measured at the 1 ev resonance using a crystal spectrometer with good resolution. A detailed analysis was made of the shape of the resonance to obtain the Breit-Wigner level width parameter. The level width was determined to be (32.3 ± 1.5) mv, and the resonance energy was (1.056 ± 0.003) ev.
Plutonium-240
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Nuclear data
Neutron Transport
Barn
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Abstract Neutron transmission measurements were carried out on an oxide sample enriched to 92.20 % 122Sn at a 190-m station with the neutron time-of-flight method. The resonance energies and neutron widths were determined for 21 resonances between 1.5 and 30 keV by a shape analysis and the following average resonance parameters for s-wave neutrons were obtained: D0 = 1.17 ± keV, S0 × 104 = 0.30 ± , R1 = 5.60 ± 0.05 fm. The s-wave neutron strength function of 122Sn is greater than the theoretical prediction of the doorway state model.
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Time-of-Flight
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A new array of four Deuterated Benzene (${\mathrm{C}}_{6}{\mathrm{D}}_{6}$) detectors has been installed at the Gaerttner Linear Accelerator Center at Rensselaer Polytechnic Institute for the purpose of measuring neutron capture cross sections in the keV region. Measurements were performed on samples of $^{181}\mathrm{Ta}$ in the unresolved resonance region (URR) using a filtered-beam technique, by which a 30 cm iron filter was placed in a white-spectrum neutron beam to remove all time-dependent $\ensuremath{\gamma}$-ray background and all neutrons except those transmitted through resonance-potential interference ``windows'' in the iron. The resulting filtered beam was effectively a quasimonoenergetic neutron source, which was used for performing measurements on isotopes with narrow level spacings in the URR. The capture cross-section results obtained for two thicknesses of tantalum are in agreement with those documented in the JEFF-3.2 library, as are the average resonance parameters obtained via a fit to the data using the sammy-fitacs code.
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