Design and performance of simple targeting efficiency monitors for high energy physics experimental areas

Simple radiation monitors of coaxial ionization chambers are used at Fermi National Accelerator Laboratory to measure targeting efficiency of the external proton beam as it impinges on secondary particle production targets in the experimental areas. In some cases the system replaces the traditional target telescope formed of three scintillation counters connected in triple coincidence. When the target monitor is recessed in shielding, target-in, target out ratios of over 100 are achieved. A single, unshielded monitor residing near the target yields a ratio of 10 for 300 GeV incident protons on a tungsten target 120 mils in diameter by 2 in. long. A companion background monitor allows this ratio to be increased by at least an order of magnitude. Evidence indicates that these simple detectors, properly located, constitute a viable target monitoring system which has operated with incident proton beams having intensity rates ranging from less than 1011 protons sec-1 to greater than 1013 protons in 20 μsec