Model 611 alphaMETER

The detector is a silicon-diffused junction (DJ) with a sensitive surface area of 450 square mm. As this detector requires a dry, dark environment to operate, it is sealed behind a thin opaque film or membrane. This film is 0.25 mil aluminized mylar, and thus is of sufficiently low density to efficiently pass alpha particles while excluding water vapour and light. This fragile sealing/alpha particle window is protected from mechanical damage behind a plastic grill located approximately 12mm from the open end of the sensitive volume.

The other end of the alphaMETER is fitted with a 4 conductor sealed twist-lock type electrical connector. This connector and its mate provide power to, and communications with, the internal electronic systems. When deployed, this connector-pair are protected from the environment by a plastic boot that supports the cable, and forms a seal between the top of the alphaMETER and the connecting cable.

The internal electronics include a pulse amplifier/conditioner and the power regulator circuits as one of the printed circuit boards, while the other circuit board contains a real-time clock and calendar, a non-volatile data memory, and a micro-processor. The micro-processor performs all necessary house-keeping functions, as well as the pulse counting and communications. Each micro-processor has a unique serial number installed in it’s permanent memory (ROM); it is this unique number that allows each alphaMETER to be addressed individually, even though numerous units may be connected to a central computer’s RS-232 serial communications port.