Measuring the energy Influx as a function of the spatial direction is of great interest for many technical and scientific questions.

This is also possible with some conventional probes, but these require shielding against thermal radiation from the environment, especially from the direction of the back of the sensor.

This shielding is usually very compact and many times larger than the actual sensor. In addition, the temperature of each shielding sooner or later increases due to the impact of the energy Influx. It becomes virtually ineffective because it also gives off thermal energy to the sensor through radiation and thus falsifies the measured value.

This problem does not exist with the active thermal probe. Due to the special technology of measuring the energy input and the calorimetric decoupling from the holder and the supply lines of the probe, a probe variant could be designed and manufactured that is able to measure the energy Influx depending on the direction without any shielding.

During the measurement process, the probe is gradually rotated around its longitudinal axis and the energy Influx is measured at different angles of inclination.

The result is a measurement curve that shows the dependency of the energy Influx on the angle of inclination of the probe, as can be seen in the figure below.

The measured values were recorded on an ion source (type Veeco ALS 340L, working gas Ar) at a distance of 300 mm at a pressure of 0.4 Pa and a beam voltage of 2000 V (black curve).

However, this does not yet show that the energy input is dependent on the angle of incidence, but only on the angle of inclination of the probe to the horizontal. Using a La Place transformation, however, it is possible to obtain the dependency of the energy Influx on the angle of incidence, as can be seen in the diagrams below.