Decay correction for tritium target experiments at Jefferson Lab

The MARATHON experiment ran at Jefferson Lab this spring.  MARATHON will determine the neutron to proton structure function ratio $F_2^n/F_2^p$ by exploiting the mirror symmetry of tritium ($^3$H) and helium ($^3$He), as well as measure the magnitude of the EMC effect in these A = 3 nuclei.  Alongside MARATHON, several other tritium target experiments have or will run in 2018.  In addition to requiring special safety precautions, tritium's radioactive nature presents a unique problem: the composition of the target continually changes due to $^3$H $\rightarrow$ $^3$He decay.  Given the half-life of tritium and the length of the experimental run period, the resulting contamination in the tritium target is non-negligible and must be corrected for.  This talk will discuss the magnitude of the effect and the time-dependent correction used in the data analysis for MARATHON and other tritium target experiments.