Photoneutron Cross Sections for Au Revisited: Measurements with Laser Compton Scattering γ-Rays and Data Reduction by a Least-Squares Method

Abstract

Photoneutron cross section measurements were made for Au in the entire energy range of the (,n) channel based on a direct neutron counting with quasi-monochromatic -rays produced in inverse Compton scattering of laser photons with relativistic electrons. The data were analyzed by a least-squares method to deduce photoneutron cross sections. The analysis significantly reduced experimental uncertainties compared with those resulting from the photon difference method. The result is compared with the previous data by direct neutron counting with -rays produced in positron annihilation in flight and by photoactivation with bremsstrahlung. The present data are in good agreement with the previous data near the neutron threshold, while there remain some discrepancies between the present and the previous data above 10 MeV.

γdecay from the quasicontinuum ofAu197,198

“…A later photoactivation experiment, performed at the S-DALINAC (Darmstadt), has provided more precise data for energies close to the (γ,n) threshold [46]. Recent photoneutron cross section measurements have been carried out at the National Institute for Advanced Industrial Science and Technology (AIST) with monoenergetic photon beams He, 197,198 Au from this work and from (γ,n) reactions [43][44][45][46][47]. The data are modeled with a combination of the EGLO model and four SLO components (model A).…”

“…They are chosen among the values suggested in Refs. [43][44][45][46][47] and give a reliable description of the photoneutron data between E γ ∼ 10.0 MeV and the resonance peak. However, this parametrization underestimates the γ SF at the neutron threshold.…”

“…produced with a more advanced technique: laser Compton backscattering (LCS) [47]. Thanks to the use of a highly efficient neutron detector for direct neutron counting and to the improved energy resolution, the 197 Au(γ,n) cross section has been determined with considerably reduced uncertainty from the neutron threshold up to 14.5 MeV where the (γ,2n) channel opens.…”

Photodisintegration ofBe9through the1/2+state and cluster dipole resonance

“…There are two methods for deconvoluting the integral of Eq. (1) to obtain σ (E γ ), the Taylor expansion method [24] and the least-squares method [27]. We summarize the Taylor expansion method which has long been used in (γ , n) cross section measurements for heavy nuclei (see [24] and references therein).…”

Photoneutron cross sections for neodymium isotopes: Toward a unified understanding of(γ,n)and(n,γ)reactions in the rare earth region

“…More details of the neutron detection can be found in Ref. [24]. Neutron detection efficiencies of the three rings were remeasured after the present experiment using a calibrated 252 Cf source with an emission rate of 2.27 × 10 4 s −1 with 2.2% uncertainty at the National Metrology Institute of Japan.…”