The registration temperature effect for lightly ionizing particles in CR-39

Plastic track detectors have been used for years to measure the elemental composition of ultraheavy cosmic rays. Recently, it has been discovered that the response of these detectors can be drastically affected by detector temperature at the time particles are recorded. The authors have investigated this effect in CR-39 for relativistic Fe and Kr ions as well as for stopping He ions. The effect for these lightly ionizing particles is smaller and opposite in sign to that reported earlier for more intensely ionizing particles. The results reported here indicate that the detector temperature should be controlled to ±100C in cosmic ray experiments designed to measure charge composition below Z=40. Thermal modeling of NRL's [Naval Research Laboratory] Heavy Ions in Space experiment indicates that this degree of temperature control is being achieved. (author)