B10(n,α)Li<

Abstract

u-particle yields from the 08(n, QVLi, Li* reactions have been measured at eight angles between 0 and 150 for neutron energies between 200 and 1250 keV. A thick natural lithium target bombarded by a pulsed proton beam provided a neutron-energy continuum. n particles from the two reactions were distinguished by measuring the sum of n-particle and neutron flight times as well as O.-particle energies. Yield data were converted to c.m. differential cross sections and each angular distribution was fitted with a series of Legendre polynomials.Coefficients of the Po terms are compared with other measurements.The coefficients of the higher order terms are qualitatively interpreted in terms of the level structure of 1 B.[NUCLEAR REACTIONS DB(s, ua), ioB(s, u&); E=0.2-1.25 Mev, measured o(8)]

The standard branching ratio10B(n,α0) to10B(n,α1)

“…6 ) The cos ()-distribution in arbitrary units is shown in Fig. 9 as an example for an incident neutron energy of 520 ke V after the conversion of both the pulseheight and the angular distribution into the eMS system.…”

Work on the neutron standards since the completion of the standards evaluation

“…In the upper part of the figure, the integrated cross sections for the last 2 ENDF/B evaluations are shown for reference on the structure I Figure 6. Measurements of the 10 B(n,α 0 γ)/ 10 B(n,α 1 γ) branching ratio by Bevilacqua compared with evaluations and experimental work by [19], [20], ORNL [21] and ORELA [22] reactions. As can be seen in figure 7, the data agree very well with that obtained from the standard cross sections.…”

The neutron cross section standards, evaluations and applications

“…For many of the older measurements not using sophisticated gridded chambers, corrections for lost events are a strong function of the angular distribution of the reaction products. Measurements [SEA76,HAM09] of these angular distributions exist. Friesenhahn et al [FRI74] have produced thin self-supporting boron films for which there is a high probability that both the reaction products will escape from the film so that summing of the alpha and 7 Li energies can occur.…”

“…This arises due to the frequent difficulty in separating these events from those leaving 7 Li in its ground state. However, a number of measurements [DAV61,MAC68], [SEA76] of the 10 B(n, α 1 γ ) 7 Li cross section have relied on the detection of the reaction products and the separation of the ground state and first excited state groups. Both NaI and Ge (Li) detectors have been used to implement the 10 B(n, α 1 γ ) 7 Li cross section.…”