To register slow neutrons, counters filled with gaseous 3He are widely used. The counter is a cylinder with a diameter of D = 25 mm, filled with gas at a pressure of 10 atm. and a temperature of 300 K. The reaction 3He(n,p)3H occurs in the counter, the cross section of which for registered neutrons is s = 5400 barn. Calculate the fraction of registered neutrons, assuming that neutrons in the counter move along its diameter.

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