The drift cell is situated within a vacuum chamber made of stainless steel. The chamber can be evacuated by a turbomolecular pump backed with a rotary pump to a level of about 1 x 10^{-7} mbar. The pressure of the working gases inside the chamber is measured by a Pfeiffer CMR 362 capacitive gauge and ranged between 5 and 1000 Pa in the measurements. Electrons emitted from the Mg disk fly towards the collector under the influence of an accelerating voltage that is applied to the cathode. This voltage is established by a BK Precision 9185B power supply. Its value is adjusted according to the required reduced electric field (E/N) for the given experiment and the actual value of the gap during the scanning process, where E/N is ensured to be fixed. The collector current is amplified by a high speed current amplifier (type Femto HCA-400M) connected to the collector, with a virtually grounded input, and is recorded by a digital oscilloscope (type Picoscope 6403B) with sub-ns time resolution. Data collection is triggered by a photodiode that senses the laser light pulses. The low light pulse energy necessitates averaging over typically 20000 to 150000 pulses. The experiment is fully controlled by a computer using LabView software.