Publications

Publications by members of the Experimental Subatomic Physics group.

Photofission of actinide nuclei in the quasideuteron and lower part of the Δ energy region

The total photofission cross sections for the actinide nuclei 232Th, 233U, 235U, 238U, and 237Np have been measured from 68 to 264 MeV using tagged photons at the Saskatchewan Accelerator Laboratory. The fission fragments were detected using parallel-plate avalanche detectors. The results show that the fission probability for 238U is 20% lower than that for 237Np and 40% higher than that for 232Th. Less significant differences were also found among the individual uranium isotopes. These results contradict the assumption that the fission probability for 238U is approximately equal to unity in this energy range. It has also been observed that the fission probability as a function of energy for all these isotopes is constant, with the exception of that for 232Th, which increases with energy, although it seems to be reaching a saturation value. Comparison between the total photofission cross section for 237Np and the photoabsorption cross sections for lighter nuclei shows a behavior consistent with a broadening of the Δ resonance with increasing atomic mass.

Author(s): 
J. C. Sanabria, B. L. Berman, C. Cetina, P. L. Cole, G. Feldman, N. R. Kolb, R. E. Pywell, J. M. Vogt, V. G. Nedorezov, A. S. Sudov, and G. Ya. Kezerashvili
Journal Reference: 
Phys. Rev. C 61, 034604 (2000)

Segmented detector for recoil neutrons in the p(γ,n)π<sup>+</sup> reaction

A segmented neutron detector has been constructed and used for recoil neutron (6–13 MeV) measurements of the reaction γp→nπ+ very close to threshold. BC-505 liquid scintillator was used to allow pulse shape discrimination between neutrons and photons. A measurement of the absolute efficiency of the detector was performed using stopped pions in the reaction πp→nγ. Results of the efficiency calibration are compared to a Monte Carlo simulation.

Author(s): 
E Korkmaz, G.V O'Rielly, D.A Hutcheon, G Feldman, D Jordan, N.R Kolb, R.E Pywell, G.A Retzlaff, B.D Sawatzky, D.M Skopik, J.M Vogt, E Cairns, U Giesen, L Holm, A.K Opper, F.M Rozon, J Soukup
Journal Reference: 
Nucl. Inst. Meth. in Phys. Res. A 431 (1999) 446-454

The response of plastic scintillator to protons and deuterons

Data on the absolute light output L(E) of plastic scintillator, in equivalent electron energy, to protons with energies up to 20 MeV have been fitted with the parameterization L(E)=A Integral from 0 to R Ln( 1+α dE/dx) dx where E is the initial particle energy, dE/dx is the specific energy loss, R is the particle range, and α is the only free parameter. The scaling factor A has been expressed in terms of α and the specific energy loss for a minimum ionizing particle, producing an absolute response curve. The best-fit value was determined to be α = (0.025±0.002) g cm−2MeV−1 which gives a normalization of A = 41.0 MeV/(g/cm2). The results of the parameterization were compared with absolute response data for protons up to 150 MeV, and deuterons up to 120 MeV, with excellent agreement being observed.

Author(s): 
G.V. O'Rielly, N.R. Kolb, R.E. Pywell
Journal Reference: 
Nucl. Inst. Meth. in Phys. Res. A 368 (1996) 745

The photon tagging facility at the Saskatchewan Accelerator Laboratory

A photon tagging facility has been constructed for use with the c.w. electron beam at the Saskatchewan Accelerator Laboratory (SAL). The facility consists of a “clam-shell” type magnetic spectrometer with a 62 channel plastic scintillator focal plane detector allowing a post-bremsstrahlung electron energy resolution of 1%. Specialized focal plane and coincidence electronics have been designed and constructed at SAL and allows experiments to be performed with average tagged photon rates of greater than 1 × 108/s.

Author(s): 
J.M. Vogt, R.E. Pywell, D.M. Skopik, E.L. Hallin, J.C. Bergstrom, H.S. Caplan, K.I. Blomqvist, W. Del Bianco, J.W. Jury
Journal Reference: 
Nucl. Inst. Meth. in Phys. Res. A 324 (1993) 328

The Saskatchewan-Alberta large acceptance detector for photonuclear physics

The Saskatchewan-Alberta Large Acceptance Detector (SALAD) is a 4π detector designed and built for studies of photonuclear reactions with a tagged photon beam. The design and performance of the detector are described. Its characteristics have been studied by examining p-p elastic scattering with a proton beam at TRIUMF.

Author(s): 
E.B. Cairns, J. Cameron, W.C. Choi, H. Fielding, P. Green, L. Greeniaus, E.D. Hackett, L. Holm, N.R. Kolb, E. Korkmaz, P. Langill, W.J. McDonald, D. Mack, W. Olsen, B. Peterson, N.L. Rodning, J. Soukup, J. Zhu, D. Hutcheon, H.S. Caplan, R.E. Pywell, et.al
Journal Reference: 
Nucl. Inst. Meth. in Phys. Res. A 321 (1992) 109

Response of a BaF<sub>2</sub> detector to photons from 75 to 200 MeV

A large cylindrical BaF2, crystal 22.9 cm long and 12.7 cm in diameter, was calibrated with monochromatic photons from the tagged-photon facility at the Saskatchewan Accelerator Laboratory. The measured spectra for the energy deposited in the crystal from the resulting electromagnetic shower compares very well with predictions of the Monte Carlo shower simulation code EGS4. A method for establishing a transferable energy calibration using cosmic ray muons is also presented.

Author(s): 
J. Clayton, W. Benenson, N. Levinsky, J.D. Stevenson, M.F. Mohar, E. Hallin, J.C. Bergstrom, H.S. Caplan, R.E. Pywell, D.M. Skopik, J.M. Vogt
Journal Reference: 
Nucl. Inst. Meth. in Phys. Res. A 608 (2009) 417

A measurement of the <sup>18</sup>O photonuclear cross sections as a test of a bremsstrahlung unfolding technique

The 18O[(γ, n) + 2(γ, 2n)] and 18O(γ, p) cross sections have been measured using the bremsstrahlung yield-curve technique. Unfolding of the yield curves to obtain the cross sections is carried out using the Variable-Bin-Penfold-Leiss technique. The results obtained agree very well with the results obtained using monoenergetic photons. The accuracy of the bremsstrahlung yield-curve technique and the resolution obtainable with this technique are thereby established.

Author(s): 
R.E. Pywell, M.N. Thompson, B.L. Berman
Journal Reference: 
Nucl. Inst. Meth. in Phys. Res. A 178 (1980) 479

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