High-resolution neutron fluence spectra have been measured in the National Accelerator Centre's p(66)/Be(40) neutron therapy beam by the pulsed-beam time-of-flight method. ICRU muscle kerma spectra have been derived from the fluence spectra. Spectral changes resulting from different irradiation conditions have been quantified in terms of the average neutron energy and the fractional low-energy (< 16 MeV) contribution. The changes observed with different thicknesses of polyethylene filtration are consistent with changes in quality parameters determined in biological and microdosimetric experiments. The dosimetry parameters (KtissueA150) N and (Wgas) N calculated for the measured spectra agree with the values recommended in the neutron dosimetry protocol. The shapes of the present fluence spectra differ from previous measurements of p(> 40)/Be spectra. In particular, they differ significantly from the spectrum measured by recoil techniques in an identical neutron therapy unit at the Clatterbridge Hospital, UK. The reasons for the difference are not known.

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Isospin properties of dipole excitations in74 Ge are investigated using the (α, α ′ γ) reaction and compared to (γ, γ ′ ) data. The results indicate that the dipole excitations in the energy region of 6 to 9 MeV adhere to the scenario of the recently found splitting of the region of dipole excitations into two separated parts: one at low energy being populated by both isoscalar and isovector probes and the other at high energy, excited only by the electromagnetic probe. RQTBA calculations show a reduction in the isoscalar E1 strength with an increase in excitation energy which is consistent with the measurement.

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