R. G. Korteling

The liquid to vapor phase transition in excited nuclei

The thermal component of the 8 GeV/c pi+ Au data of the ISiS Collaboration is shown to follow the scaling predicted by Fishers model when Coulomb energy is taken into account. Critical exponents tau and sigma, the critical point (p(c),rho(c),T(c)), surface energy coefficient c(0), enthalpy of evaporation DeltaH, and critical compressibility factor C(F)(c) are determined. For the first time, the experimental phase diagrams, (p,T) and (T,rho), describing the liquid vapor coexistence of finite neutral nuclear matter have been constructed.

Signals for a transition from surface to bulk emission in thermal multifragmentation.

Excitation-energy-gated two-fragment correlation functions have been studied between E(*)/A = (2-9)A MeV for equilibriumlike sources formed in 8-10 GeV/c pi(-) and p+197Au reactions. Comparison with an N-body Coulomb-trajectory code shows an order of magnitude decrease in the fragment emission time in the interval E(*)/A = (2-5)A MeV, followed by a nearly constant breakup time at higher excitation energy. The decrease in emission time is strongly correlated with the onset of multifragmentation and thermally induced radial expansion, consistent with a transition from surface-dominated to bulk emission expected for spinodal decomposition.

The measurement of 10Be concentrations with a tandem accelerator

Abstract An FN tandem accelerator has been used to measure the 10Be concentrations in natural samples. An injector of low mass resolution is used to allow 9BeO− and 10BeO− to be injected simultaneously into the accelerator and the 10Be/9Be ratio of the sample i compared directly to that of a standard. The advantages and disadvantages of this simultaneous measurement approach are discussed. Details of our measurement system and examples of results are presented.

An ion injection system for use in Tandem accelerator radioisotope dating devices

Abstract A system designed to accept ion beams from a Cs sputter source and inject them into a Tandem Van de Graaff accelerator is described. Several modes of operation of the device are possible, including simultaneous injection of two or more isotopes, continuous injection of two isotopes with pulsed injection of a third, and sequential injection. The application of the system to radioisotope dating studies is discussed.

Silicon detector ΔE, E particle identification: a theoretically based analysis algorithm and remarks on the fundamental limits to the resolution of particle type by ΔE, E measurements☆

Abstract The wide range of validity for a parameterless ΔE, E particle identification algorithm based on integrating Bragg curves using the Bethe-Bloch equation with a universal effective charge term is illustrated with detector telescope data for H through Mg. An analysis of straggling in the ΔE detector for this data is used to investigate the validity of theoretical straggling expressions which can then be used to investigate the fundamental limits to ΔE, E particle identification.

Thermal excitation of heavy nuclei with 5–15 GeV/c antiproton, proton and pion beams

Abstract Excitation-energy distributions have been derived from measurements of 5.0–14.6 GeV/c antiproton, proton and pion reactions with 197 Au target nuclei, using the ISiS 4 π detector array. The maximum probability for producing high excitation-energy events is found for the 8 GeV/c antiproton beam relative to other hadrons, 3 He and p beams from LEAR. For protons and pions, the excitation-energy distributions are nearly independent of hadron type and beam momentum above about 8 GeV/c. The excitation energy enhancement for p beams and the saturation effect are qualitatively consistent with intranuclear cascade code predictions. For all systems studied, maximum cluster sizes are observed for residues with E ∗ /A∼6 MeV.

Heating nuclear matter with GeV 3He beams

Abstract The heating curve for hot nuclei formed in the 4.8 GeV 3 He+ nat Ag, 197 Au reactions has been derived from reconstructed excitation-energy distributions and temperatures based on 2,3 H/ 3,4 He isotope ratios. Intranuclear-cascade predictions over-estimate the excitation-energy distributions for hot thermal-like residues, but are in general agreement with the data when contributions from preequilibrium emission are included. Both targets exhibit nearly an identical temperature vs. excitation energy dependence. The heating curve initially increases rapidly, undergoes a slope change near E ∗ /A = 2–3 MeV, and then follows a gradual monotonic increase up to E ∗ /A = 10 MeV. The results are in qualitative agreement with predictions of EES and SMM multifragmentation models.

Breakup time scale studied in the 8 GeV/c pi- + 197Au reaction

Experimental data from the reaction of an 8.0 GeV/c pi- beam incident on a 197Au target have been analyzed in order to investigate the integrated breakup time scale for hot residues. Alpha-particle energy spectra and particle angular distributions supported by a momentum tensor analysis suggest that at large excitation energy, above 3-5 MeV/nucleon, light-charged particles are emitted prior to or at the same time as the emission of the heavy fragments. Comparison with the SMM and GEMINI models is presented. A binary fission-like mechanism fits the experimental data at low excitation energies, but seems unable to reproduce the data at excitation energies above 3-5 MeV/nucleon.

Large-angle proton emission in the 9Be(p, 2p) reaction at 300 MeV

Abstract A 9 Be(p, 2p) coincidence experiment performed to further elucidate the reaction mechanism for the production of energetic wide-angle protons in intermediate-energy proton-induced reac- tions is reported. Detectors in a coplanar geometry were used to measure coincidences between trigger protons at 90° to the beam and forward-angle protons on the opposite side of the beam. The incident proton energy was 300 MeV. We report both the inclusive spectra for the trigger protons and the differential mean multiplicities for the coincidence events. The outgoing proton energies were measured using NaI detectors. Trigger protons were grouped into 10 MeV bins covering the kinetic energy range from 55 to 155 MeV. The forward protons were measured over a kinetic energy range of 65–280 MeV and an angular range of 14–60° with respect to the beam. The present results are compared with two previous experiments which covered a more restrictive kinematical range. Calculations are performed with both phase-space and direct knockout models, and compared with experiment. Observation of angle and energy correlation effects suggested by knockout models indicate that such direct mechanisms provide a significant contribution to energetic wide-angle inclusive proton spectra.

Tracking the phase-transition energy in the disassembly of hot nuclei

In efforts to determine phase transitions in the disintegration of highly excited heavy nuclei, a popular practice is to parametrise the yields of isotopes as a function of temperature in the form