Alphasprayer

The Alphasprayer is a small, directional radiation device that becomes decisive evidence in the investigation of a robot’s death. Found clenched in the robot’s hand and held against its skull, it explains how the robot’s positronic brain was irreversibly destroyed; its traceable origin at a power plant leaves a further question about how it was obtained.

Construction and Operation

The device is described as a shiny ovoid roughly two inches long and half an inch wide, with a mica window at one end. Its casing is made of head-alloy and contains a narrow longitudinal pit; a fragment of plutonium salt sits at the bottom, while a thin mica cover closes the pit. Because mica is transparent to alpha particles, radiation escapes in a hard spray in one direction. The construction makes the Alphasprayer a focused emitter rather than a general-purpose source of radiation.

Baley recognizes the instrument from handling several during physics laboratory courses. He does not need a dictionary or handbook to identify its components and operation, and his recognition helps turn the object at the scene into an intelligible cause of death. The device’s technical explanation is therefore part of the investigation, not a detached description: its materials and directional design account for the particular damage found on the robot.

Use in the Robot’s Destruction

Dr. Gerrigel reports that the robot was lying prone, already irreversibly deactivated when he examined it. The Alphasprayer remained in its partly clenched right fist, which touched the robot’s skull as though contact with the head had been its final act. The position of the object links its physical presence to the fatal event.

Baley confirms that the mica end had been placed against the robot’s head. Dr. Gerrigel agrees: the radiation immediately randomized the robot’s positronic brain paths, producing what he calls instant death. The sequence is starkly specific—window against skull, concentrated radiation, randomized brain paths—and supplies a mechanical explanation for a death that might otherwise remain opaque. The Alphasprayer is not a legal instrument for killing robots, although it has many other uses; its application here is thus both technically effective and explicitly unlawful.

Evidence and Investigation

The Commissioner confirms that there is no uncertainty about the identification. Counters detected the Alphasprayer from ten feet away, and photographic film in the storeroom was fogged. Those separate traces support the conclusion that the object emitted radiation and make the identification more than a visual guess. The Commissioner calls the matter cut and dried, even as the investigation continues to ask where the weapon came from.

Baley asks whether the Alphasprayer has been traced. The answer is that it came from one of the power plants, but the plant has no explanation for its disappearance. The investigation can therefore establish a source without establishing the circumstances of the loss. The device’s evidentiary role shifts from explaining the robot’s destruction to pointing toward an unresolved chain of access and responsibility.

Narrative Significance

The Alphasprayer’s importance rests on the gap between what its physical evidence proves and what it leaves unanswered. Its dimensions, mica window, radiation traces, and position against the robot’s skull make the immediate cause of deactivation unusually concrete. Yet tracing it to a power plant does not identify who removed it or how it reached the scene. A single object thus closes one question—the mechanism of destruction—while keeping another open: the route by which the weapon was acquired.