Streak cameras are used to obtain very high temporal resolution of the radiation from sources. Bandwidths up to about 1THz are achievable using drive electronics with much more moderate bandwidths of around 1GHz. This enormous increase in system bandwidth comes from the very nonlinear way the electronics manipulates the image and is similar to that used in an oscilloscope.
Generally only a section of the radiation source is investigated by using a slit at the input to the camera. An image of this slit is swept across the final image plane. In order to manipulate the image in this way an image convertor tube is usually employed. A photocathode converts the image into electrons. These are then imaged onto a phosphor but pass a deflection structure that can sweep the electron image across the phosphor screen. In this way any changes in the light level in time at the cathode become changes in recorded intensity at the phosphor.

In most streak cameras the cathode is imaged onto the phosphor screen with an electrostatic lens. This provides a large distance between the cathode and the screen so that direct line of sight x-rays can be stopped from hitting the screen. In addition the lens provides a drift region in which the electrons can be deflected. The deflection field must be applied so that the potential in the drift region is maintained close to zero volts. To this end the deflection has to be balanced, i.e. there must be an electric field perpendicular to the beam such that the potential on axis is zero. This is achieved by applying equal but opposite potentials to a pair of deflection plates between which the electron beam passes. A ramped voltage is applied to each plate. If a particular electric field is maintained across these plates then the beam is deflected to a certain position on the screen. By ramping the field the beam is swept. The ramp speed is controlled to achieve as linear a sweep rate as possible. By changing the ramp rate the sweep speed is controllable. At slower sweep speeds Kentech has been able to produce MOSFET circuitry. At fast sweep speeds we use an avalanche pulser.

Several factors influence the time resolution of a streak camera. Firstly the electron energy spread from the photocathode, secondly static image size of the slit and thirdly electron beam self field effects.
Kentech can supply x-ray streak cameras in which the deflection speed is greatly increased. When this is combined with a very high extraction field at the cathode, high time resolution is possible. We have also considered pulsing the cathode to achieve higher extraction fields. These techniques, although capable of very high time resolution have a fairly short temporal history and users should consider very carefully whether this approach will achieve their aims.
An alternative approach is to use a standard tube but with somewhat improved sweep speed. Such a system requires careful focussing with the radiation being investigated and careful attention to timing jitter problems.