https://www.slb.com/services/characterization/testing/multiphase/vx_technology.aspx https://www.slb.com/services/characterization/testing/multip... https://www

https://www.slb.com/services/characterization/testing/multiphase/vx_technology.aspx https://www.slb.com/services/characterization/testing/multip... https://www.tracerco.com/ https://www.tracerco.com/ The Vx meter uses Barium-133. I think tracerco uses cesium. However they are really small amount, but because its nuclear stuff you have to get a bunch of permits and stuff.