Isotopic effects observed in fragmentation reactions induced by protons, deuterons, and α particles of incident energies between 660 MeV and 15.3 GeV on 112 Sn and 124 Sn targets are discussed. The exponential scaling of the yield ratios with the third component of the fragment isospin t3 = (N − Z)/2 is observed in all reactions, with scaling parameters that depend on the incident energy. Breakup temperatures for these reactions are deduced from double ratios of isotopic yields and tested for their relation with the isoscaling parameters.The quantum statistical (QSM) and the statistical multifragmentation (SMM) models are used for interpreting the results. The observed isoscaling can be understood as a consequence of a statistical origin of the emitted fragments in these reactions. The SMM analysis shows that the exponent describing the isoscaling behavior is proportional to the strength of the symmetry term of the fragment binding energy. Using this result, a symmetry-term coefficient γ ≈ 22.5 MeV for fragments at breakup is deduced from the experimental data. This is close to the standard value and supports SMM assumptions for the breakup configuration. An alternative method of determining the symmetry-energy coefficient, by using isotope distribution widths, is also discussed.

No abstract

No abstract

No abstract

A carbon resistance thermometer with very convenient characteristics has been developed. It allows accurate measurement of temperatures and temperature differences over a wide temperature range using a Wheatstone bridge. By varying the ratios of the constituents in the carbon mixture, the resistance and sensitivity can be varied more or less predictably. A sixth degree polynomial, fitted to calibration points in liquid helium, hydrogen and nitrogen only, gives an accurate (R, T ) relation over the whole temperature region. This is demonstrated with a calibration against a gas thermometer.In a separate experiment the superconducting transition temperature of lead has been determined. By interpolating with the polynomial without reference to the gas thermometer, a value of 7 . 1 9 0 "~ has been obtained, in very good agreement with literature.