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#Tasco timetool freezes software
#Tasco timetool freezes code
#Tasco timetool freezes free

It is important, however, to keep an eye on the TT signal and make sure it doesn't drift off the camera! Also, the white light pulse is only ~1 ps long! To change the delay "window" the TT is looking at, a delay stage is used to move the white light in time to keep it matched to the x-rays. That's fine, because the typical jitter in arrival times between x-rays and laser at LCLS is much less than that. The TT has about ~1 ps of dynamic range in a given physical setup. The edge is big with respect to the camera. The etalon is especially bad here – it's amplitude and frequency will depend on the target. The nearly-constant sine-like wave is undesirable background due to an etalon effect inside the TT target.

Boom! An edge! The edge moves back and forth on the camera screen depending on the relative time delay between the laser and x-rays.

The blue line is a raw projection, the green is an ROI'd projection (recommended!). If you take a projection of this image along the y-axis, you obtain a trace similar to this: Here's what the raw signal looks like, typically: The white light, now "imprinted" with the x-ray pulse, is dispersed by a diffraction grating onto a camera. This causes the index of refraction of the material to change, and generates an edge in the white light power profile (in time, and therefore also spectrally, due to the chirp).

Somewhere in the middle of passing through the target, the x-rays join the party, hitting the target at the same place, but for a shorter temporal duration (~50 fs is typical). 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.

#Tasco timetool freezes code

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.

#Tasco timetool freezes software

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.

#Tasco timetool freezes free

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.