Recording defocused point spectra

Sometimes people want to record point spectra with the beam defocused so as to minimize radiation damage. This is possible, if the sample is homogenous enough. To increase the spot size to a diameter of $D$, you need to defocus by a distance of $\Delta f=D\delta_{r_{N}}/\lambda$, where $\delta_{r_{N}}$ is the outermost zone width of the zone plate and $\lambda=(1239.852 \mbox{eV}\cdot\mbox{nm})/E$ is the x-ray wavelength. Because the microscope calculates the focus at a particular photon energy based on the alignment file, to get a defocused spetrum you need to deliberately record a defocused alignment:

• With your sample in place, record its x-ray focus position (see Sec. 2.8).
• Move ZSTG downstream by $\Delta f$ using the dialog Move $\rightarrow$ Stepper.
• Record sample in X-ray focus (see Sec. 2.8).
• Begin recording your defocused point spectra.

To get the sample back into focus, just move your sample upstream by the same distance $\Delta f$. You should then double-check that you are still in the x-ray focus.