Prompt neutron polarization asymmetries in photofission of Th-232, U-233,U-235,U-238, Np-237, and Pu-239,Pu-240

作者：Mueller J M^*; Ahmed M W; France R H III; Johnson M S; Karwowski H J; Myers L S; Randrup J; Sikora M H; Spraker M C; Stave S; Tompkins J R; Vogt R; Weller H R; Whisnant C S; Zimmerman W R

来源：Physical Review C, 2014, 89(3): 034615.

DOI：10.1103/PhysRevC.89.034615

Photofission experiments were performed on targets of Th-232, U-233,U-235,U-238, Np-237, and Pu-239,Pu-240 using nearly 100% linearly polarized, high intensity (similar to 5 x 10(6)gamma/s), and nearly-monoenergetic gamma -ray beams having energies between 5.3 and 7.6 MeV at the High Intensity gamma -ray Source ( HI gamma S) located at Duke University and Triangle Universities Nuclear Laboratory. An array of 12-18 liquid scintillator detectors was used to measure prompt fission neutron yields parallel and perpendicular to the plane of beam polarization. Polarization asymmetries, the differences between the in- plane and out-of- plane yields divided by their sums, were measured. Asymmetries close to zero were found for U-233,U-235, Np-237, and Pu-239 while significant asymmetries (similar to 0.2-0.5) were found for Th-232, U-238, and Pu-240. Predictions based on previously measured photofission fragment angular distributions combined with a model of prompt neutron emission agree well with the experimental results.

• 出版日期2014-3-19