The cylinder that is part of the air drive came from an air-operated door at the Bevatron that is no longer needed. The bearings and shaft under the chair came from the Bevatron Biomed Facility overhead rail system. Another part was scavenged from salvage. By necessity, Cepeda's device is an object of absolute precision. Tumors in the eye are extraordinarily tiny, typically one centimeter or less in diameter, and can be located next to the optic nerve.
Sight is lost if, during treatment, the beam hits the optic nerve.
So, the patient positioner must be able to move and hold the patient's head with a wiggle room of less than one millimeter. For a patient, sitting in this chair at the business end of a proton beam can be a scary experience. Cepeda did what he could to minimize the trauma. To help immobilize the head, the patient must close his or her mouth on a bite block. By locking the jaw in place, the head too becomes locked in place.