AMO - Atomic, Molecular & Optical Science

The AMO instrument is situated on one of the soft X-ray branches of the LCLS that delivers intense ultra short pulses of X-rays from the FEL. Instrumentation is designed to minimize losses and deliver the maximum possible X-ray intensity to the interaction region. Gaseous targets of atoms, molecules, clusters, or nanoscale objects such as protein crystals or viruses are typically used in the AMO instrument with electron and ion spectrometers as well as large area detectors for X-ray diffraction measurements. Science performed with the AMO instrumentation includes fundamental studies of light-matter interactions in the extreme X-ray intensity of the LCLS FEL beam, time-resolved photoionization, X-ray diffraction of nanocrystals and single shot imaging of non-reproducible objects.

In order to maintain the high peak brightness of the LCLS X-ray pulse, a minimal set of optics is used to deliver the beam to the target in the AMO instrument. In addition to the three soft X-ray offset mirrors (SOMS) that deliver the beam to the soft X-ray branches, two planar-elliptically bent Kirkpatrick Baez mirrors are used to focus the beam to approximately ~5 µm² in the first interaction region within the high-field physics or LAMP chamber. The mirrors can be bent to various radii, allowing the focus to be moved along the beam or the size of the beam in the interaction region varied as desired by the experiment. At the more downstream interaction region in the Diagnostics chamber or other user supplied chamber such as Cookie Box, foci of ~30-50 µm² can be achieved.

A high powered synchronized optical laser is available for all experiments in the AMO instrument and a variety of wavelengths has been used for different experiments. An 800 nm beam is typically delivered to the hutch with wavelength conversion carried out in the hutch with doubling and tripling crystals for shorter wavelengths and an optical parametric amplifier (OPA) for longer wavelengths available. Additional lasers have been installed in the hutch (i.e. a Nd:YAG laser) for specific experiments, and all special cases should be discussed directly with hutch staff.