In one of the earlier missions, the Marked One had to go through Lab X-18 in the Dark Valley to collect documents. When the player brings said documents back to the bar, Barkeep looks at them and says that the components to the Kaymanov emitters were manufactured in X-18 itself.
After finding out this information, Marked One must travel through the perils of Wild Territory to the Yantar area, at which point the player must talk with Professor Sakharov. Eventually he will obtain a psi-protection device and be able to fight his way into the lab under the Yantar factory, which is swarming with zombified stalkers and snorks. After turning off the psi-brain or "miracle machine" (which was actually an experimental Kaymanov emitter created after a breakthrough in X-18), he must search the corpse of Ghost to obtain the documents, which will then also be brought to Barkeep.
The Brain ScorcherEdit
Marked One's next job is to go to the Red Forest and turn off the Kaymanov emitters at the Brain Scorcher complex. After battling his way through a horde of brainwashed Monolithian warriors, the player can access the bunker/lab that the control panel is located in and shut off the Brain Scorcher's emitters, disabling the last of the Kaymanovs in the Zone.