Determination of neutron cross sections and resonance parameters for the osmium isotopes 186, 187, and 188, /sup 205/Tl, /sup 32/S, the stable tellurium isotopes and of the 82 keV inelastic cross section for /sup 238/U. Progress report, November 1, 1979-September 30, 1980. [Denison Univ. , Granville, Ohio]

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

Study of the 232Th(n,f) Cross section at NCSR ‘Demokritos’ using Micromegas Detectors

HNPS Proceedings ◽

10.12681/hnps.2994 ◽

2020 ◽

Vol 27 ◽

pp. 106

Author(s):

Sotirios Chasapoglou ◽

A. Tsantiri ◽

A. Kalamara ◽

M. Kokkoris ◽

V. Michalopoulou ◽

...

Keyword(s):

Cross Section ◽

Cross Sections ◽

Nuclear Reactions ◽

Detection Efficiency ◽

High Energy ◽

Tandem Accelerator ◽

Line Detector ◽

Accelerator Driven Systems ◽

The Masses

The accurate knowledge of neutron-induced fission cross sections in actinides, is of great importance when it comes to the design of fast nuclear reactors, as well as accelerator driven systems. Specifically for the 232Th(n,f) case, the existing experimental datasets are quite discrepant in both the low and high energy MeV regions, thus leading to poor evaluations, a fact that in turn implies the need for more accurate measurements.In the present work, the total cross section of the 232Th(n,f) reaction has been measured relative to the 235U(n,f) and 238U(n,f) ones, at incident energies of 7.2, 8.4, 9.9 MeV and 14.8, 16.5, 17.8 MeV utilizing the 2H(d,n) and 3H(d,n) reactions respectively, which generally yield quasi-monoenergetic neutron beams. The experiments were performed at the 5.5 MV Tandem accelerator laboratory of N.C.S.R. “Demokritos”, using a Micromegas detector assembly and an ultra thin ThO2 target, especially prepared for fission measurements at n_ToF, CERN during its first phase of operations, using the painting technique. The masses of all actinide samples were determined via α-spectroscopy. The produced fission yields along with the results obtained from activation foils were studied in parallel, using both the NeusDesc [1] and MCNP5 [2] codes, taking into consideration competing nuclear reactions (e.g. deuteron break up), along with neutron elastic and inelastic scattering with the beam line, detector housing and experimental hall materials. Since the 232Th(n,f) reaction has a relatively low energy threshold and can thus be affected by parasitic neutrons originating from a variety of sources, the thorough characterization of the neutron flux impinging on the targets is a prerequisite for accurate cross-section measurements, especially in the absence of time-of-flight capabilities. Additional Monte-Carlo simulations were also performed coupling both GEF [3] and FLUKA [4] codes for the determination of the detection efficiency.

Activation cross section of the (n,2n) reaction on Hf isotopes

HNPS Proceedings ◽

10.12681/hnps.1906 ◽

2019 ◽

Vol 23 ◽

pp. 47

Author(s):

A. Kalamara ◽

M. Serris ◽

A. Spiliotis ◽

D. Sigalos ◽

N. Patronis ◽

...

Keyword(s):

Cross Section ◽

Cross Sections ◽

Reaction Cross Section ◽

Beam Energy ◽

Reaction Cross ◽

Activation Technique ◽

Incident Neutron ◽

Activation Cross Section ◽

Reference Reaction

Cross sections of the 174Hf(n,2n)173Hf and 176Hf(n,2n)175Hf reactions have been experimentally determined relative to the 27Al(n,α)24Na reference reaction at incident neutron energies of 15.3 and 17.1 MeV by means of the activation technique. The irradiations were carried out at the 5 MV tandem T11/25 Accelerator Laboratory of NCSR "Demokritos" with monoenergetic neutron beams provided via the 3H(d,n)4He reaction, using a new Ti-tritiated target of 373 GBq activity. In the determination of the 176Hf(n,2n)175Hf reaction cross section the contamination of the 174Hf(n,γ)175Hf and 177Hf(n,3n)175Hf reactions has been taken into account. Moreover, the neutron beam energy has been studied by means of Monte Carlo simulation codes and the neutron flux has been determined via the 27Al(n,α)24Na reference reaction.

Determination of the absorption cross-sections of higher order iodine oxides at 355 nm and 532 nm

10.5194/acp-2020-456 ◽

2020 ◽

Cited By ~ 1

Author(s):

Thomas R. Lewis ◽

Juan Carlos Gómez Martin ◽

Mark A. Blitz ◽

Carlos A. Cuevas ◽

John M. C. Plane ◽

...

Keyword(s):

Cross Section ◽

Cross Sections ◽

Atmospheric Chemistry ◽

Absorption Cross Section ◽

Absorption Cross ◽

Time Resolved ◽

Flight Mass Spectrometry ◽

Iodine Oxides ◽

Photo Ionization

Abstract. Iodine oxides (IxOy) play an important role in the atmospheric chemistry of iodine. They are initiators of new particle formation events in the coastal and polar boundary layer and act as iodine reservoirs in tropospheric ozone-depleting chemical cycles. Despite the importance of the aforementioned processes, the photochemistry of these molecules has not been studied in detail previously. Here, we report the first determination of the absorption cross sections of IxOy, x = 2, 3, 5, y = 1–12 at λ = 355 nm by combining pulsed laser photolysis of I2/O3 gas mixtures in air with time-resolved photo-ionization time-of-flight mass spectrometry, using NO2 actinometry for signal calibration. The oxides selected for absorption cross section determinations are those presenting the strongest signals in the mass spectra, where signals containing 4 iodine atoms are absent. The method is validated by measuring the absorption cross section of IO at 355 nm, σ355 nm, IO = (1.2 ± 0.1) × 10–18 cm2, which is found to be in good agreement with the most recent literature. The results obtained are: σ355 nm, I2O3