Partial cross sections of the 89 Y(p, γ ) 90 Zr reaction have been measured to investigate the γ -ray strength function in the neutron-magic nucleus 90 Zr. For five proton energies between E p = 3.65 MeV and E p = 4.70 MeV, partial cross sections for the population of seven discrete states in 90 Zr have been determined by means of in-beam γ -ray spectroscopy. Since these γ -ray transitions are dominantly of E1 character, the present measurement allows an access to the low-lying dipole strength in 90 Zr.A γ -ray strength function based on the experimental data could be extracted, which is used to describe the total and partial cross sections of this reaction by Hauser-Feshbach calculations successfully. Significant differences with respect to previously measured strength functions from photoabsorption data point towards deviations from the Brink-Axel hypothesis relating the photo-excitation and de-excitation strength functions.

Background: Deviations between experimental data of charged-particle-induced reactions and calculations within the statistical model are frequently found. An extended data base is needed to address the uncertainties regarding the nuclear-physics input parameters in order to understand the nucleosynthesis of the neutron-deficient p nuclei. Purpose: A measurement of total cross-section values of the 130 Ba(p,γ ) 131 La reaction at low proton energies allows a stringent test of statistical model predictions with different proton+nucleus optical model potentials. Since no experimental data are available for proton-capture reactions in this mass region around A ≈ 130, this measurement can be an important input to test the global applicability of proton+nucleus optical model potentials. Method: The total reaction cross-section values were measured by means of the activation method. After the irradiation with protons, the reaction yield was determined by use of γ -ray spectroscopy using two clover-type high-purity germanium detectors. In total, cross-section values for eight different proton energies could be determined in the energy range between 3.6 MeV E p 5.0 MeV, thus, inside the astrophysically relevant energy region. Results: The measured cross-section values were compared to Hauser-Feshbach calculations using the statistical model codes TALYS and SMARAGD with different proton+nucleus optical model potentials. With the semimicroscopic JLM proton+nucleus optical model potential used in the SMARAGD code, the absolute cross-section values are reproduced well, but the energy dependence is too steep at the lowest energies. The best description is given by a TALYS calculation using the semimicroscopic Bauge proton+nucleus optical model potential using a constant renormalization factor. Conclusions: The statistical model calculation using the Bauge semimicroscopic proton+nucleus optical model potential deviates by a constant factor of 2.1 from the experimental data. Using this model, an experimentally supported stellar reaction rate for proton capture on the p nucleus 130 Ba was calculated. At astrophysical temperatures, an increase in the stellar reaction rate of 68% compared to rates obtained from the widely used NON-SMOKER code is found. This measurement extends the scarce experimental data base for charged-particle-induced reactions, which can be helpful to derive a more globally applicable proton+nucleus optical model potential.

T h i s report documents response characteristics and the development of dose algorithms for the Hanford Combination Neutron Dosimeter (HCND) implemented on January 1, 1995. The HCND was accredited under the U.S. Department o f Energy (DOE) Laboratory Accreditation Program (DOELAP) during 1994. The HCND employs two neutron dose components consisting o f 1) an albedo thermoluminescent dosimeter (TLD) , and 2) a track-etch dosimeter (TED). Response characteristics of these two dosimeter components were measured under the low-scatter conditions of the Hanford 318 Building Calibration Laboratory, and under the high-scatter conditions in the workplace a t the Plutonium Finishing Plant (PFP). The majority of personnel neutron dose a t Hanford (currently and historically) occurs a t the PFP. National Institute of Standards and Techno1 ogy (NIST) 'traceable sources were used t o characterize dosimeter response i n the laboratory. A t the PFP, neutron spectra and dose-measuring instruments, including a mu1 tisphere spectrometer, tissue equivalent proportional counters, and specially calibrated rem meters, were used t o determine the neutron dose under several configurations from three different plutonium sources: 1) plutonium tetrafluoride, 2) plutonium metal , and 3) plutonium oxide. In addition,

Background: Uncertainties in adopted models of particle + nucleus optical-model potentials directly influence the accuracy in the theoretical predictions of reaction rates as they are needed for reaction-network calculations in, for instance, y-process nucleosynthesis. The improvement of the a + nucleus optical-model potential is hampered by the lack of experimental data at astrophysically relevant energies especially for heavier nuclei. Purpose: Measuring the l87R e(a,n)190Ir reaction cross section at sub-Coulomb energies extends the scarce experimental data available in this mass region and helps understanding the energy dependence of the imaginary part of the a + nucleus optical-model potential at low energies. Method: Applying the activation method, after the irradiation of natural rhenium targets with a-particle energies of 12.4 to 14.1 MeV, the reaction yield and thus the reaction cross section were determined via y-ray spectroscopy by using the Cologne Clover Counting Setup and the method of y y coincidences. Results: Cross-section values at five energies close to the astrophysically relevant energy region were measured. Statistical model calculations revealed discrepancies between the experimental values and predictions based on widely used a+nucleus optical-model potentials. However, an excellent reproduction of the measured crosssection values could be achieved from calculations based on the so-called Sauerwein-Rauscher a + nucleus optical-model potential. Conclusion:The results obtained indicate that the energy dependence of the imaginary part of the a + nucleus optical-model potential can be described by an exponential decrease. Successful reproductions of measured cross sections at low energies for a-induced reactions in the mass range 141 < A < 187 confirm the global character of the Sauerwein-Rauscher potential.