W. H. Geist

The [sup 3]He([rvec d],p)[sup 4 Breve; ]He reaction at low energies

Angular distributions of cross sections and complete sets of analyzing powers for the [sup 3]He([rvec d],p)[sup 4]He reaction have been measured at five energies between E[sub d]=60 and 641 keV. The energy dependence of the cross section was also measured from 245 to 685 keV, and the absolute cross section was determined at E[sub d]=426thinspkeV. The data have been included in an [ital R]-matrix analysis of the [sup 5]Li system. The bare-nuclear cross section derived from the [ital R]-matrix parametrization was used to determine the electron screening potential. [copyright] [ital 1999] [ital The American Physical Society]

Proton-deuteron elastic scattering at low energies

We present measurements of differential cross sections and the analyzing powers A{sub y}, iT{sub 11}, T{sub 20}, T{sub 21}, and T{sub 22} at E{sub c.m.}=431.3keV. In addition, an excitation function of iT{sub 11}({theta}{sub c.m.}=87.8{sup o}) for 431.3{<=}E{sub c.m.}{<=}2000keV is presented. These data are compared to calculations employing realistic nucleon-nucleon interactions, both with and without three-nucleon forces. Excellent agreement with the tensor analyzing powers and cross section is found, while the A{sub y} and iT{sub 11} data are found to be underpredicted by the calculations.

Possible three-nucleon force effects in D–P scattering at low energies

Abstract We present measurements of the analyzing powers A y and iT 11 for proton–deuteron scattering at E c.m. =432 keV. Calculations using a realistic nucleon-nucleon potential (Argonne V18) are found to underpredict both analyzing powers by ≈40%. The inclusion of the Urbana three-nucleon interaction does not significantly modify the calculated analyzing powers. Due to its short range, it is difficult for this three-nucleon interaction to affect A y and iT 11 at this low energy. The origin of the discrepancy remains an open question.

A proton polarimeter for 3He(d,p)4He polarization transfer studies

Abstract A compact polarimeter has been constructed and calibrated to measure the polarization of 13–16 MeV protons, such as those emitted from the 3 He(d,p) 4 He reaction near the E d =430 keV resonance. The polarimeter uses p- 4 He elastic scattering as an analyzer. It consists of a 4 He gas cell pressurized to 2.76 MPa and a left–right pair of CsI detectors collimated at 65° to maximize the figure of merit for the device. The effective analyzing power and efficiency of the polarimeter have been measured as a function of energy using a collimated polarized proton beam. These measured values are in good agreement with a Monte Carlo computer simulation that forms the basis for the calibration curve for the device. Preliminary results from the 3 He(d,p) 4 He reaction with polarized deuterons confirm that the proton polarimeter can be used to determine polarization transfer coefficients near the low-energy resonance.

Ion implanted 3He targets for very low energy experiments

Abstract Helium-3 was implanted into tantalum and aluminum foils at implant energies ranging from 7 to 20 keV and with ion fluences exceeding 10 19 ions/cm 2 for the purpose of producing targets for nuclear reaction experiments. The effects of implant energy, fluence, and temperature on target thickness were studied. The foils were bombarded with deuterons to initiate the 3 He(d,p) 4 He reaction near the 430 keV resonance to determine target thicknesses, thickness lifetimes, and to study the properties of this reaction as a polarization analyzer. Results indicate that these targets can be used in an efficient low-energy polarization analyzer.

A target chamber for the study of low-energy reactions

Abstract A scattering chamber, biased by as much as 200 kV, has been designed, built and used successfully to accelerate low-energy beams with good energy resolution from the Triangle Universities Nuclear Laboratory atomic-beam polarized-ion source and minitandem accelerator. It is equipped to contain charged-particle and gamma-ray detectors which are used to detect reaction products with high resolution. In operation, the analog signals are sent via fiber-optic lines to signal-handling electronics at ground potential.

A deuteron tensor polarimeter for low-energy experiments

A deuteron tensor polarimeter utilizing the 3He(d,p)4He reaction has been calibrated at energies between 113 and 323 keV using implanted 3He targets. It provides an efficient determination of polarization at deuteron energies between 100 and 700 keV due to the presence of the 32+ resonance at Ed = 430 keV. In an energy range around the resonance the tensor analyzing power Ayy = 0.5 at all angles and Azz is −0.85 at a mean angle of 17.5°.

The use of the 3He(d↘,p)4He reaction for polarimetry at low energies

Angular distributions of tensor analyzing powers Ayy and Azz have been measured in 3He(d,p)4He reaction in the 130 to 322 keV energy range. The reaction proves to be very efficient and easy to use to determine polarization of deuteron beams.

Studies of the D state of {sup 6}Li using the FSU polarized {sup 6}Li Beam

One way to quantify the D-state component of the wave function of a nucleus is by the quantity η, the ratio of the D- and S-state asymptotic normalization constants. Analyses of the analyzing powers from transfer reactions induced by polarized ions have been useful for the determination of η in the A=2−4 systems. In an effort to determine η for the d+α relative motion in 6Li we have measured analyzing powers for (6Li,d) reactions on 58Ni and 40Ca at E(6Li)=34 MeV. The experiments were performed at Florida State University using the Optically Pumped Polarized Lithium Ion Source. We compared the data with the results of well-constrained DWBA calculations assuming a direct α-particle transfer mechanism. With η the only free parameter in the calculations, a best fit to the tensor analyzing power data results in an average value of η=+0.0003±0.0009, much smaller than previous determinations.