A Cosmic Ray Muon Spectrometer Using Pressurized Gaseous Cherenkov Radiators

Abstract: In this work, we propose a new approach to cosmic ray muon momentum measurement using multiple pressurized gaseous Cherenkov radiators. Knowledge of cosmic ray muon momentum has the potential to significantly improve and expand the use of a variety of recently developed muon-based radiographic techniques. However, existing muon tomography systems rely only on muon tracking and have no momentum measurement capabilities which reduces the image resolution and requires longer measurement times. A fieldable cosmic ray muon spectrometer with momentum measurement capabilities for use in muon scattering tomography is currently missing. We address this challenge by optimally varying the pressure of multiple gaseous Cherenkov radiators and identifying the radiators that are triggered by muons that have momentum higher than the Cherenkov threshold momentum. We evaluate the proposed concept through Geant4 simulations and demonstrate that the cosmic ray muon momentum spectrum can be reconstructed with sufficient accuracy and resolution for two scenarios: (i) a perfect Cherenkov muon spectrometer and (ii) a practical spectrometer where noise is introduced in the form of scintillation and transition radiation photons. To quantify the accuracy of spectrometer, the concept of true and false classifications are introduced. The fraction of true classification is investigated for each momentum level in a practical radiator. The average classification rate for momentum range of 0.2 to 7.0 GeV/c with uncertainty of 1 GeV/c is approximately 85%.