This is a Teledyne Isotopes 2x2x6 inch NaI(Tl) detector with integral voltage divider and gain adjustment with resolution of 9.3% or better at 661.66 keV. An external preamplifier is required for operation such as ORTEC model 113, Canberra 1405, or Canberra 2005. The Integral Series solid crystal assemblies manufactured by Isotopes, Inc. are single hermetically sealed units consisting of a crystal optically coupled to a photomultiplier tube. An internal magnetic shield is included as basic equipment with each Integral Series crystal. This internal magnetic shield is sufficient protection against the earth's field. A voltage divider is also be supplied with each tube. Aluminum housing; 1/32 inch wall thickness. Photomultiplier model numbers DuMont 6292, RCA 8053, and EMI 9536B are compatible with these crystal assemblies.