The white light propagates through the target, with shorter (bluer) wavelengths arriving first, and longer (redder) wavelengths arriving later. A camera that captures the dispersed white light.A diffraction grating that disperses the white light pulse after it goes through the target.A "target", usually YAG or SiNx, that gets put in the path of both the white light and LCLS x-ray beam.A laser setup that creates a chirped white-light ps-length pulse concurrently with the pump.I will proceed describing mode 2.Ī "timetool" is composed of the following elements: If you are running in option #1, ignore the rest of this page and get help (ask your PoC). spectral encoding (also called "transmission" mode), where the X-rays change the transmission of a material and a chirped laser probes it by a change in the spectral components of the transmitted laser.spatial encoding (also called "reflection" mode), where the X-rays change the reflectivity of a material and a laser probes that change by the incident angle of its wavefront or.The tool measures the time difference between laser and FEL by one of two methods: The TT signal comes in the form of a 2D camera image, one for each event (x-ray pulse). Principle of Operationīefore embarking on timetool analysis, it is useful to understand how the thing works. That code can probably do what you want, and can act as a template if it does not.Įnough rambling. If you wish to re-process the timetool signal, this page explains how the 'tool works, and presents the use of psana-python code that can assist you in this endeavor. Or you are a hater of black boxes and need to do all analysis yourself. Or you are using 3rd party software that needs to process the raw signal for some reason. Maybe the tool was not set up quite right, and you suspect errors in the default analysis. In many cases, however, re-processing of the timetool is desirable. Lucky you! The information here on how the timetool works may still be of interest, and if you have decided to just trust the DAQ, you have a lot of free time on your hands now – so why not learn about it? Then you can blindly use the results provided by LCLS. You will still need to calibrate the timetool: read the section on calibration to understand why and how. In most cases, if the timetool has been set up properly, it is possible to simply use the DAQ's default analysis to extract this difference in arrival time. The timetool is used to measure the inherent jitter in the arrival time between an optical laser and LCLS x-ray pulse.
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