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Unfortunately, right now CXI, XPP, and AMO have different methods for doing this calibration. Talk to your beamline scientist about how to do it and process the results.

Conversion from FLTPOS pixels into ps

Once you do this calibration, it should be possible to write a simple function to give you the corrected delay between x-rays and optical laser. For example, the following code snip was used for an experiment at CXI. NOTE THIS MAY CHANGE GIVEN YOUR HUTCH AND CONVENTIONS. But it should be a good starting point .

def relative_time(edge_position):
    """
    Translate edge position into fs (for cxij8816)
    
    from docs >> fs_result = a + b*x + c*x^2, x is edge position
    """
    a = -0.0013584927458976459
    b =  3.1264188429430901e-06
    c = -1.1172611228659911e-09
    x = tt_pos(evt)
    tt_correction = a + b*x + c*x**2
    time_delay = las_stg(evt)
    return -1000*(time_delay + tt_correction)

Rolling Your Own

Hopefully you now understand how the timetool works, how the DAQ analysis works, and how to access and validate those results. If your DAQ results look unacceptable for some reason, you can try to re-process the timetool signal. If, right now, you are thinking "I need to do that!", you have a general idea of how to go about it. If you need further help, get in touch with the LCLS data analysis group. In general we'd be curious to hear about situations where the DAQ processing does not work and needs improvement.

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