Tummajännitteeseen

Tummajännitteeseen, often translated as "dark voltage" or "dark current," is a phenomenon observed in photoelectric devices such as photomultiplier tubes and photodiodes. It refers to the small electrical current that flows through the device even when no incident light is present. This current is not due to the desired photoelectric effect but rather to other internal processes within the device.

The primary sources of tummajännitteeseen include thermionic emission from the photocathode and other internal components, field emission due to strong electric fields, and leakage currents across insulating surfaces. These processes generate charge carriers that are amplified and detected as a current, mimicking a light signal.

This dark current is a significant factor limiting the sensitivity of many photodetectors, as it sets a baseline noise level that can obscure faint light signals. Various techniques are employed to minimize tummajännitteeseen, such as cooling the device to reduce thermionic emission, using materials with lower intrinsic conductivity, and employing specific electrode geometries to reduce field emission. Understanding and controlling tummajännitteeseen is crucial for applications requiring high sensitivity, such as in scientific instrumentation, astronomy, and medical imaging.