W. Del Bianco

The photon tagging facility at the Saskatchewan Accelerator Laboratory

Abstract 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.

Angular distributions of the 2h(d, γ)4he reaction

Abstract Angular distributions of γ-rays from the 2 H(d, γ) 4 He reaction have been measured at the deuteron energies E d = 6.05, 8.96 and 11.67 MeV with a 12.7 cm × 15.2 cm NaI(Tl) crystal enclosed in a Cerenkov anticoincidence shield. A least-square fit of the angular distributions indicates that the differential cross section is proportional to sin 2 θ cos 2 θ and that the process proceeds through an E2 transition of the type 1 D 2 → 1 S 0 .

Search for the parity-forbidden heavy-particle width Γ′dα of the Ex = 3.562 MeV state in 6Li

Abstract Alpha-particle capture by deuterium has been investigated at excitation energies in 6 Li close to the J π = 0 + , T = 1, E x , = 3.562 MeV state. A search for resonance γ-rays from this state has yielded a negative result and an upper limit for the heavy-particle width Γ ′ d α ≦ 0.017 eV.

On the parameters which characterize the design of a windowless gas target

Abstract The theory relevant to the flow of gases through tubes and orifices has been reviewed and presented in a form suitable for practical applications. The viscous flow of gases through tubes and orifices has been measured for He, N 2 , and Ar. The results compare favourably with the theory and the results of other experiments. A four-stage windowless gas target has been designed and its performance evaluated. Overall pressure ratios of the order of 10 7 for He and 3×10 8 for N 2 and Ar have been obtained.

Deuteron photodisintegration by 20.3 MeV linearly polarized γ-rays

Abstract Linearly polarized γ-rays from the 3 H(p, γ ) 4 He reaction have been used to measure the relative neutron yield of the 2 H(γ, n)H reaction at θ n = 90° and at φ n = 0°, 45° and 90°. The 20,3 MeV γ-rays were monitored by a 12.7 diameter × 15.2 cm long NaI(Tl) crystal. A 6.3 cm diameter × 6.3 cm long NE230 scintillator was used both as a deuterium target and a proton detector, and a 30.5 cm diameter × 15.2 cm long NE213 scintillator was employed to detect the photoneutrons. The energy of the protons and the time of flight of the neutrons from the 2 H(γ, n)H reaction were measured in coincidence and the events recorded in a bidimensional spectrum. The ratio a b of the coefficients of the angular distribution of the 2 H(γ, n)H reaction and the quantity Σ(90°) were obtained from the ratio of the photoneutron yields at φ n = 90° and 0° and found to be a / b = 0.063−0.076 ± 0.036 and Σ = 0.913−0.925 ± 0.051.

Measurement of the 50Cr(γ, n)49Cr cross section with monochromatic γ-rays

Abstract The 50 Cr(γ, n) 49 Cr cross section has been measured over the energy range E γ = 20.43 to E γ = 22.22 MeV using monochromatic γ-rays from the 3 H(p, γ) 4 He reaction and detecting the resulting 49 Cr positon activity. The γ-rays were monitored by a 12.7 cm × 15.2 cm NaI(Tl) crystal. The positon activity was determined by a coincidence detector consisting of two 7.62 cm × 7.62 cm NaI(Tl) crystals set on the annihilation radiation photopeaks. The γ-ray energy resolution was less than 110 keV over the whole energy range. Structure in the cross section was not observed.

A windowless gas target for nuclear research

A windowless gas target has been built for the purpose of studying the 2H(α, γ)6Li reaction and other radiative capture reactions characterized by small cross sections. Special features of the target are the possibility of detecting recoil nuclei emitted at θ=0°, recirculation and purification of the gas, and electronic control and stabilization of the gas pressure. The maximum pressure in the target depends on the sizes of orifices and tubes and on the molecular weight of the gas and can vary from a few Torr to several hundred Torr.

Stopping power of alpha particles in deuterium gas

Abstract This article describes an accurate measurement of the stopping power of α-particles in deuterium gas at energies E α ⩽5.5 MeV. Such a measurement was required for an experiment presently under way in this laboratory 1 ) aimed at obtaining information on the parity non-conserving ΔT =1 nuclear interaction 2 ).

The 9Be(d, γ0)11B reaction in the region of the giant dipole resonance

The 90° yield of the 9Be(d, γ0)11B reaction has been measured at deuteron energies ranging from 2.86 to 11.92 MeV in steps of 250 keV. Angular distributions have been obtained at Ed = 2.96, 6.87, 8.89 and 9.65 MeV. The γ-rays have been detected with a 23 cm × 23 cm NaI(Tl) crystal spectrometer enclosed in a plastic-scintillator anticoincidence shield. Evidence of structure has been observed in the excitation curve at Ed ≈ 3.4 and 9.65 MeV corresponding to excitation energies Eexc = 18.6 and 23.7 MeV, respectively. The angular distributions are typical of E1 transitions with a maximum at θL ≈ 90°. A calculation of the differential cross section of the inverse reaction, considered as a one-step direct process, gives results incompatible with the experiment and suggests that the 9Be(d,γ0)11B reaction proceeds through excitation of the T = 12 component of the giant dipole resonance in 11B.

Reduction of cosmic ray background in a NaI crystal with a Čerenkov anticoincidence shield

Abstract The cosmic ray background in a 5″ dia.×6″ long NaI(Tl) crystal was reduced by enclosing it in a Cerenkov anticoincidence shield surrounded by a 4″ thick layer of lead. The reduction factor was 26 between 10 and 30 MeV and 61 between 15 and 97 MeV.