CERN Accelerating science

Experiments at CERN
Title	Exposure of CR39 Stacks to Oxygen and Sulphur Beams at the CERN-SPS
Experiment	WA86
Greybook	See WA86 experiment
Approved	03 June 1987
Status	Finished
Collaboration	ION/PLASTIC-1
Accelerator	CERN SPS
Abstract	We plan to expose 8 stacks of CR39 sheets to oxygen and sulphur ions of 60 and 200 GeV at the CERN-SPS. The main purpose of the exposures is the calibration of the CR39 sheets used for a large area experimental search for magnetic monopoles at the Gran Sasso Laboratory (experiment MACRO). The stacks have 20 layers of CR39, each layer 13 cm x 7 cm and 1.4 mm thick. A copper absorber is located after the first 6 layers. We require exposures of about 2000 tracks per cm$^2$ over the entire area of the stack with a uniform illumination. The standard beam used for the emulsion experiments is normally adequate for this purpose. We have performed one exposure to sulphur ions. The etched tracks have been measured automatically with the Elbeck image analyser system. We measured the incoming sulphur ions as well as the nuclear fragments produced in the copper absorber. Clean separation among the peaks due to the various fragments is obtained (there is no indication of nuclei with fractional electric charge). These measurements allow a good calibration of the response of CR39. We find that the response of the CR39 made commercially by the Intercast Company of Parma, Italy, is adequate; the response of that made in the production line specifically designed for CR39 to be used as track-etch material is clearly superior and with lower threshold &lbrk.Z/$\beta$=6&rbrk. Further exposures will calibrate the newly made material; we will also expose the old CR39 in order to see the effects of aging. Until this moment we have seen no effect of aging for the material made almost 2 years ago.
Related document(s)	CERN-SPSC-87-17  (SPSC-P-228)

Contact: Vanderhaeghe, G