The methods employed and the results obtained from measurements and calculations of the detection efficiency for the neutron detectors used at Triangle Universities Nuclear Laboratory (TUNL) in the simultaneous determination of the 1S0 neutron–neutron and neutron–proton scattering lengths ann and anp, respectively, are described. Typical values for the detector efficiency were 0.3. Very good agreement between the different experimental methods and between data and calculation has been obtained in the neutron energy range below En=13MeV.

A liquid scintillation detector aimed for neutron energy and fluence measurements in the energy region below 20MeV has been calibrated using monoenergetic and white spectrum neutron fields. Careful measurements of the proton light output function and the response matrix have been performed allowing for the application of unfolding techniques using existing codes. The response matrix is used to characterize monoenergetic neutron fields produced by the T(d,n) reaction at low deuteron energies.

When the quasi-monoenergetic DD neutron source is used in scattering experiments, the scattering fractions of monoenergetic and continuous breakup neutrons are superimposed at low neutron energies. In order to extend the data analysis to this energy region, the two fractions have to be separated. The separation can be achieved with an “abnormal” scattering geometry, i.e. a long distance between target and sample (more than 2m) and a short flight path between sample and detector (below 1m). Another possibility is the use of a “normal” scattering geometry, i.e. a short distance between target and sample (below 20cm) and a long flight path (12m), and a separation of the two scattering fractions by a complete Monte Carlo simulation. The advantages and shortcomings of the two methods are discussed in detail. Double-differential cross-sections of vanadium measured at similar energies around 10.2MeV and determined by the two different methods are compared and discussed.

Five scintillation detectors of different scintillator size and type were characterized. The pulse height scale was calibrated in terms of electron light output units using photon sources. The response functions for time-of-flight (TOF)-selected monoenergetic neutrons were experimentally determined and also simulated with the NRESP code over a wide energy range. A comparison of the measured and calculated response functions allows individual characteristics of the detectors to be determined and the response matrix to be reliably derived. Various applications are discussed.

The analysis of (e,e′n) experiments at the Darmstadt superconducting electron linear accelerator S-DALINAC required the calculation of neutron response functions for the NE213 liquid scintillation detectors used. In an open geometry, these response functions can be obtained using the Monte Carlo codes NRESP7 and NEFF7. However, for more complex geometries, an extended version of the Monte Carlo code MCNP exists. This extended version of the MCNP code was improved upon by adding individual light-output functions for charged particles. In addition, more than one volume can be defined as a scintillator, thus allowing the simultaneous calculation of the response for multiple detector setups. With the implementation of 12C(n,n′3α) reactions, all relevant reactions for neutron energies En<20MeV are now taken into consideration. The results of these calculations were compared to experimental data using monoenergetic neutrons in an open geometry and a 252Cf neutron source in the complex Darmstadt setup, where in both cases excellent agreement was found.

Differential neutron elastic-scattering cross sections of elemental chromium are measured from 4.5 {approx} 10 MeV in steps of {approx} 0.5 MeV and at {ge} 40 scattering angles distributed between {approx} 17{degree}--160{degree}. Concurrently differential cross sections for the inelastic neutron excitation of the yrast 2{sup +} (1.434 MeV) level in {sup d52}Cr are determined. In addition, broad inelastically-scattered neutron groups are observed corresponding to composite excitation of levels up to {approx} 5.5 MeV in the various chromium isotopes. These experimental results are combined with low-energy values previously reported from this laboratory, with recent {approx} 8 {yields} 15 MeV data measured at the Physikalisch-Technische Bundesanstalt and with a 21.6 MeV result from the literature to form an extensive neutron-scattering data base which is interpreted in the context of spherical-optical and coupled-channels (rotational and vibrational) models. These models reasonably describe the observables but indicate rather large energy-dependent parameter trends at low energies similar to those previously reported near the peak of the S{sub o} strength function in studies at this laboratory. The physical implications of the measurements and models are discussed including deformation, coupling, dispersive and asymmetry effects.