|
|
|
Spatial Resolution
This describes the ability of an optical system to image or to reproduce small structures. The spatial resolution can be defined as limiting resolution or FWHM.
Streak Tube
The streak tube is the key component of a streak camera. This vacuum tube consist of a photocathode, a focusing system, deflection plates and a phosphor screen. Electrons generated by the photocathode are accelerated towards the phosphor screen. When passing the deflection plates, they can be deviated orthogonally to the propagation direction before they hit onto the phosphor screen. The image on the phosphor screen can be shifted proportionally to the applied deflection voltage. Streak tubes may be built with one pair of deflection plates or with two pairs that are oriented orthogonally with respect to each other.
Streak Unit
see sweep unit
Sweep Speed
A voltage ramp applied to the deflection plates results in a moving image on the streak tube phosphor screen. The speed of this movement is called sweep speed typically given in time units per dimension units (example ps/mm). This simplifies the conversion from position information into the time information of the measured signals.
Sweep Speed non-linearity
The sweep speed of an image that moves over the phosphor screen may change slightly along the sweep direction. This sweep speed variation referred to its mean speed is called sweep speed non-linearity. The sweep speed non-linearity may depend on the selected sweep speed and the screen position.
Sweep Unit
Part of a streak camera that provides the deflection voltages to drive the deflection plates of the streak tube. The sweep unit offers a range of selectable sweep speeds. The sweep unit might be integrated in the streak camera body or it might be a separate and exchangeable module. Sweep units are separated in two different types according to the temporal behaviour of the deflection voltage. Sweep units generating a linear voltage ramp after each trigger pulse are called triggered sweep units (TSU). If a high frequency sinusoidal voltage is generated, the corresponding unit is called synchroscan sweep unit (SSU).
Synchronization
Synchronization generally describes the temporal coincidence of two processes or signals. Related to streak cameras synchronization means the coincidence between the electron deflection and the optical signal that has to be measured. Related to high-speed cameras synchronization describes the capture of individual images controlled by an external signal.
Synchroscan
In synchroscan mode a sinusoidal sweep voltage is applied to the deflection plates of a streak tube. This mode allows to operate the streak system at high deflection frequencies of 40 to 250MHz. As many sweeps can be superimposed on the phosphor screen, this technique allows to measure very faint signals.