The Totaln−pScattering Cross Section at 4.75 Mev

Abstract

Attenuation measurements in good geometry on polyethylene and graphite scatterers with transmissions from 0.30 to 0.65 have been made. A thin-walled gas target was used, producing forward d-d neutrons at a mean energy of 4.749=h0.009 Mev. Care was taken to minimize uncertainties arising from neutrons of other energies, from unshadowed background, and from impurities in the samples. The geometry was such that multiple scattering-in contributed no more than 0.12 percent to the total uncertainty. Checks against ratedependent sensitivity of the detector revealed no effects greater than 0.15 percent. The total n-p scattering cross section deduced from the measurements is 1.690=1=0.0066 barns, where the probable error has been increased from the statistical error of 0.002 4 barn to include the energy uncertainty and estimates of possible systematic effects. Values of ro s (n~p \ the singlet effective range of the n-p interaction, obtained from this result for several potential shapes, are compared with corresponding values of r^p~p\ The validity of the hypothesis of charge independence is found to depend on the potential shape assumed.

Templates of expected measurement uncertainties for total neutron cross-section observables

“…Tunable mono-energetic neutron sources can be used to measure transmission at discrete neutron energies. Such sources can be created at charged particle accelerators with neutron-production reactions such as D(d,n) 3 He [11][12][13][14], T(p,n) 3 He [15,16], and T(d,n) 4 He [11]. Transmission measurements with mono-energetic neutron sources were most popular in the 1950s through the 1970s.…”

“…In the case of mono-energetic neutron source measurements, the background is split into three componentsin-scattering, room return, and unattenuated neutrons produced anywhere but in the gas cell or solid target [13]. In-scattering occurs when a neutron is scattered at a forward angle and still reaches the detector.…”

Templates of expected measurement uncertainties for neutron-induced capture and charged-particle production cross section observables

“…Reactors can be used to perform measurements in a thermal spectrum, such as at the Budapest Research Reactor [6]. For HER measurements, reactions such as D(d, n) 3 He [11][12][13][14], T(p, n) 3 He [15,16], T(d, n) 4 He [11], 7 Li(p, n) [17,18], and even 18 O(p, n) [3] can be used. The Associated Particle (AP) technique [19] is often used to quantify the neutron flux for in-beam measurements, where the detection of the charged-particle product of the neutronproduction reaction acts as a trigger to record the signal from any reactions that occur.…”

“…Many of the detector systems require a lot of material near the sample (such as the vacuum chamber and detector housing) which the neutrons can interact with. Scattered neutrons can also interact directly with the detector materials, resulting in additional charged particles produced via reactions such as 28 Si(n, p), 28 Si(n, α), 12,13 C(n, p), and 12,13 C(n, α). These energy-dependent backgrounds can be measured and subtracted out [88,93], suppressed with data analysis thresholds [94,101], or characterized by Monte Carlo simulations using MCNP or GEANT and subtracted [102].…”

“…For example, if two samples are irradiated together, they will share the same t i value and δt i will be fully positively correlated between the two samples. The correlation induced by the time factor, f , should be calculated using equation (13).…”