Muon rate

This page provides a way to determine the background rate in the determination of the muon lifetime. For long intervals, the rate of double events is not due to the same muon decaying in the plastic scintillator but it is caused by random transits of different muons which come at a rate of about one per minute per cm². Ours is a 2" detector so the cross section is about 25 cm².

The plastic scintillator is connected to a LeCroy 623A discriminator. The threshold should be set high enough to suppress the detection of radioactive decay. The output of this discriminator is the external trigger of the oscilloscope. A new image is displayed when an external trigger is detected twice within 9 microseconds.

The discriminator uses ECL levels with logic 1 at -1.75 V. An H11N2 optocoupler is used to translate this to TTL levels for an Arduino microcontroller. This counts all events incoming pulses using an interrupt routine. It has an Ethernet shield for connectivity to internet. The measurements made in this page will display a new current number together with a time stamp. The number in the Arduino counter is limited to 65535 after which it will restart at zero.

Use these data to estimate the background in the distribution of decay events. Remember that accuracy depends on the number of counts N. When the rate is random, the estimate of the relative error is (√N)/N. But sometimes there is a non-random contribution from electrical interference. When such disturbances occur, this should be apparent on the oscilloscope images.