The present specification describes systems and methods for the simultaneous detection of radioactive materials such as neutrons, muons and gamma rays based on thin gap chamber technology. A thin-gap chamber (TGC) is disclosed having a thermal neutron absorber material, such as 10B4C or 10B8C, which interacts with neutrons to emit heavy particles. The heavy particles, in turn, interact with the gas present in chamber to produce ionization that is converted into a measurable signal. The TGC is embedded in a neutron moderating medium. The detector systems are fabricated from commercially available construction materials and are easy to manufacture at a reasonable cost when compared to conventional He-3 neutron detector systems.