A radiation beam analyzer for measuring the distribution and intensity of radiation produced by a CyberKnife®. The analyzer employs a relative small tank of water into which a sensor is placed. The distance between the sensor and the radiation source is not varied. The tank of water is raised and lowered relative to the sensor to simulate the location of a malady within a patient's body. This movement of the tank permits the radiation from the CyberKnife® to be properly calibrated and adjusted for a proper treatment of a malady in a patient.