Diagnostic Evaluation of NuMI Hadron Monitor Ion Chambers

The performance of the NuMI Hadron Monitor ion chambers was evaluated. Possible sources of ion chamber performance degradation are discussed, based upon analysis of Monitor data. The quality of the signal is reviewed, and it is concluded that the Monitor still functions for its main tasks. Repair is not possible, but replacement of the Hadron Monitor during the 2017 summer shutdown was not deemed necessary. Lastly, a diagnostic apparatus for potential impurity of the helium gas inside the chamber has been designed and installed. A vacuum chamber is connected to the Hadron Monitor exhaust line to collect gas samples. These samples are analyzed by a GCMS (gas chromatograph-mass spectrometer).