A comparative study of the gain characteristics of image intensifiers

Abstract

We report measurements of dynamic range, gain profile and absolute gain of three second-generation image intensifiers under pulsed illumination. One electrostatically focused (Mullard 1330) and two proximity focused (Varo 9732 and Photek microchannel plate 140) image intensifiers have been characterized. The dynamic ranges were found to be 240, 560, and 400 for the Mullard, Varo, and Photek tubes, respectively, for all gain settings. At a microchannel plate bias voltage of 900 V the radiant gain for these tubes is 4 x IO' , 3 x lo' , and 2x io3, respectively. The sensitivity and dynamic range of the charge-coupled device camera recording system were found to be superior to that of conventional highspeed film (Kodak TMAX).

Characterization of an X-ray streak camera at 18.2 nm

“…The transmission of the step wedge was measured with the cooled CCD camera at an arbitrary wavelength of 700 nm. The dynamic range of the CCD camera had previously been checked at that wavelength [3]. From the transmission data at 700 nm, the thickness of each step was calculated using the absorption coefficients of copper, and the transmittance at 18.2nm was then obtained from the step thickness and the absorption coefficient at 18.2 nm [6].…”

“…As an example, figure 3(a) shows the streaked 18.2 nm line intensity generated by a 5 Jj50 ps laser pulse (400 ps x-ray pulse) and attenuated by the step wedge. The transmitted signal per step was determined at the maximum x-ray intensity and was corrected for the gain profile of the image intensifier [3]. For each shot a set of four data points was thus obtained, corresponding to the four attenuation steps of the wedge.…”

“…This pulse broadening as a function of step transmission is shown in figure 3(b). The lower limit of the dynamic range is given by the lowest detectable signal from the image intensifier as recorded by the cooled CCD camera [3]. The upper limit is determined by the intensity value (relative illuminance or absolute current density) at which a 20% broadening of the recorded pulse width can be observed x-ray pulse duration and have no effect in static operation mode [7].…”

“…This simple model follows from the conservation of the number of electrons emitted from the cathode and dispersed on the phosphor. The signal S is measured in relative units (counts) which are proportional to the incident photon density [3]. The relationship between counts and incident photon flux is specified by the manufacturer of the CCD chip (Photometrics).…”

“…Here, we restrict ourselves to the dynamic behaviour of the Kentech x-ray streak camera itself. The results for the image intensifier and the CCD camera are reported in a separate paper [3].…”