  We demonstrate the effectiveness of two techniques for using x-rays to
evaluate the amount of charge diffusion in charge coupled devices (CCDs). We
quantify the degree of charge diffusion with two parameters: sigma_d, the
standard deviation for a Gaussian diffusion model, and Q, a ratio of the point
spread function (PSF) peak to its wings. sigma_d and Q are determined by
fitting a model to a pixel energy histogram, and by summing the PSF of all
x-ray events, respectively. Using seven test devices, we investigate the
precision of these two techniques and demonstrate that they produce compatible
results. The histogram fitting method is sensitive to the structure of the
electric field within these devices, in addition to the inherent charge
diffusion properties. The Q ratio is a very simple parameter to measure and
provides an easily accessible method for quickly evaluating a CCD's diffusion
length.
