XPCS Analysis 8-ID

This Wiki page is dedicated towards providing documentation on 8-ID XPCS Data Analysis and Visualization

Overview

The sections below provide description of Visualization of XPCS results followed by the Data Reduction/Analysis of Raw Data to yield Correlation functions.

XPCS metadata and results are primarily saved into a HDF5 file format based on a Data Exchange format defined at the APS.

MetaData File

The concept is as follows: There are groups in the HDF5 file that are part of the Data Acquisition and these are categorized into the following:

/measurement

/measurement/instrument /measurement/instrument/acquisition/

/measurement/instrument/detector/ /measurement/instrument/detector/roi/ /measurement/instrument/detector/kinetics/

/measurement/instrument/source_begin/

/measurement/sample/

The above groups each contain several HDF5 datasets or parameters which have a scalar, vector, ND arrays or string attributes. The above are present in every metadata HDF5 file associated with each data acquisition. This file is saved in the same directory/folder as the raw detector images file itself.

Analysis Parameters

When a data set is processed which primarily means some sort of a correlation analysis, then the parameters that are needed to analyze the data such as:

• user defined mask
• wave vector maps (called as qmaps) where each wave vector or an azimuthal angle is characterized by a unique integer in what is called as a digitized map
• look up table that links the integers in the qmaps to the q/phi values
• Start and end frame numbers to be processed which could be a subset of the frames collected
• More intricate (meaning ones that are not changed from their defaults often) analysis parameters such as the multitau delay level, striding and averaging frames prior to correlation
• location of the file in the local as well as in a remote file system
• A very critical field which defines where the output of the computation - the results - are saved in the HDF5 file.

The above parameters (data sets) are saved in the HDF5 file in a special group called "/xpcs". Often, a user analyzes a given data set more than once if not several times which could each be under different conditions such as varying one or more of the above analysis parameters. While there might be a short sighted convenience seen in keeping these different analysis into separate HDF5 files, the concept of maintaining groups in the same HDF5 file has a higher value as the user will readily know all the different analysis or processing that are done to a given data set.

Embracing that idea, the current implementation defines the first time analysis group as "/xpcs" and the output of this analysis is saved into a group that is defined under "/xpcs/output_data" which usually points to a group named "/exchange".

For every subsequent analysis that is performed, the XPCS group is called "/xpcs_N" where N=1,2,3,4,..... In the same way as described above, "/xpcs_N/output_data" points to "/exchange_N".

Section 2

Section 4

1. dadga
2. agdga
3. test
4. help

Beamline Summary

Date	Start Time	Duration	Task	Status
12/7	1:00 PM	1 Day	cadmus	DONE
12/14	1:00 PM	1 Day	echo	DONE
12/21	1:00 PM	1 Day	overhead comfort displays	DONE
12/22	1:00 PM	1 Day	demeter	DONE
1/3	1:00 PM	1 Day	phoenix	DONE
Run 2017-1 (or April/May shutdown)	TBD	TBD	other MCR systems as approved by AOP	DONE

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