Nanospectroscopy beamline - XPEEM operation mode

XPEEM IMAGING

The sample is illuminated with x-rays or UV radiation, to excite photoemission. IL and P1 image the specimen image produced by the objective. A slit is inserted in the dispersive plane of the analyzer, in order select the desired energy of the photoelectrons. The specimen image is finally projected onto the detector by the action of P2 and P3. The contrast aperture in the diffraction plane limits the angular acceptance for optimum lateral resolution.

SPELEEM operation: XPEEM imaging mode

OPERATIVE INSTRUCTIONS

Prepare the beamline!
- Set the undulator gap, phase and modulator current for the desired energy, using the macro /BEAMLINE/GAP_VS_ENERGY or the calculate gap utility in BCS Java. Enter these settings in the "beamline controls" window of UMeasure, selecting the "undulator" tab.
- Set the monochromator energy to the desired value through the "beamline controls" window of UMeasure, selecting the "monochromator" tab. Make sure that the correct grating is inserted and set for the energy range of interest.
- Align the photon beam on the sample, as explained in refocussing mirror alignment.
Prepare the microscope!
- Using LEEM insert the desired contrast aperture, and the energy slit in place. Set the STV and the focus, using LEEM and clicking the "autofocus" checkbox. When this is done, turn off the e-gun by closing the Wehnelt and open the beamline.
- Set the approporate STV. In order to fine tune the focus, you can do a focus series using a dedicated macro.
- Use "ACQUIRE" to make a single image. Once acquisition is complete, the program will offer you to save the image.
- If the acquisition times are too long, sample drift may occur; use the macro ../MOVIES/SEQUENCE to acquire a sequence of images, which can be co-added later with a drift correction algorithm.