Performance of the SPS beam spectrometer chambers under very high fluxes

Five beam spectrometers each consisting of four 100*100 mm/sup 2/, 1 mm wire spacing, multiwire proportional chambers, are operational in the secondary beams of the CERN SPS. To determine the ultimate performance of the chambers and associated electronics, capable of working at a threshold of 0.5 mu A and transmitting signals on 500 m twisted pair cables at rates of 25 MHz/wire, the authors have studied the behaviour of the chambers under very high beam fluxes ( approximately 10/sup 7/ particles/s). Up to 10/sup 5/ particles/(mm /sup 2/.s) efficiencies as high as 90% can be reached. (4 refs).