Abb. 1 Typischer Ausgangspuls bei 2.5 kV Betriebsspannung

Abb. 2 Typische Verstärkungscharakteristik

Abb. 3 Zählrate ggn. Betriebsspannung

Abb. 4 Verstärkung als Funktion der Zählrate

Abb. 5 Typische PHD bei 2.6 kV (3000 cps)

Abb. 6 Typische PHD ggn. Betriebsspannung

The demonstration of absence of force for the Aharonov-Bohm effect (Fig. 1) and the Kapitza-Dirac effect (Fig. 2) happened decades after their predictions [1,2]. In these two experiments, the particle detection was done with Dr. Sjuts electron multipliers.

The required temporal resolution of 1 nanosecond is provided by the Dr. Sjuts detector. Given the need to detect the arrival time of individual electron for the first experiment and the low count rate (0.1/s) for the second experiment, the electron had to be counted.

Both experiments called for nanosecond timing, while for the Kapitz-Dirac experiment this had to be combined with a spatial resolution of mircrometers. A narrow metal slit was placed in front of a channel electron multiplier and translated to obtain the spatial resolution. The comparison to a quantum mechanical calculation showed (inset Fig.2) that the detector had a flat response as a function of position; no background subtraction was needed. Most of the time the laser was off (10 nanosecond pulses with a 50 Hz repetition rate), which meant that the signal had to be filtered out of a strong backgrond with coincidence measurement techniques.