Rogowski coil: Pulsed beam current diagnostic at extremes.

Short current pulses are increasingly prevalent in electronics devices such as accelerator machines, digital communication, electromagnetic pulse generators and others. Rogowski coil detectors are used to monitor them in order to know the intensity and temporal behaviour. Currently, electromagnetic stresses in biological samples are applied by linear transmission line, and as a consequence Rogowski coils by linear structure are developed. The last developments have exhibited response rise time increased of more 100 ps $vs.$ an input pulse by rise time of about 250 ps. Clearly, measurements with faster rise times would be more appropriate and for this reason appropriate homemade probes have been made. The input pulse was generated by a 50 $\Omega$ coaxial line 2 m long by a fast switch (Reed relay h12). Two different Rogowski coils were done and compared, by 210 and 22 rings, whose capacitance values $vs.$ ground and between ring and ring, were different. The capacitance values resulted lower for the 22-turns coil. With this Rogowski coil the rise time of the response was only slightly higher, by 50 ps, than the input one.