The single photon counting x-ray CCD camera spectrometer is used in laser-plasma interaction experiments as a simple tool to study the K-shell x-ray generation [1-7]. Since these spectrometers require almost no alignment, they are a useful tool to study the x-ray flux variations in laser-plasma interaction experiments. The idea behind the working of this spectrometer is that the number of electron-hole pairs (or signal) generated in a single pixel of CCD camera by a single x-ray photon is proportional to the energy of x-ray photon. Therefore, a CCD detector enables the spectrum of the impinging x-ray radiation to be obtained without further dispersive devices. If a histogram of the signal from all the pixels is generated, the spectrum of the incident x-ray photons will show up in addition to the background noise of the CCD camera.

Since the basic assumption of this method is that all the energy of the x-ray photon is deposited in a single pixel, the number of photons incident on the CCD camera should be much smaller than the number of pixels so that the average number of photons per pixel<< 1. This ensures that there will be very few two or higher photon events. In laser plasma experiments, x-ray flux is very high and therefore, the number of photons have to be reduced for this method to work. This can be achieved by using Pb shielding and has been demonstrated to work even in the Peta Watt range laser plasma experiments [4]. However, despite all the precautions taken to reduce the photon flux and minimise two photon events, the problem of one photon depositing energy in several neighboring pixels has to be tackled. If such cases are not handled carefully, they lead to reduced resolution of the spectrometer. More recently, methods have been devised to consider such events more efficiently and improve the resolution. In this paper, we compare two methods of counting x-ray events and their effect on the generated spectrum.