Use at beamline (windows or leroy)

The main use for this code is to enable the conversion from the tif files that the SITK writes and various datafiles written by LabView into fits files. At the same time, it can provide a quicklook of the data to diagnose problems before the next frame is taken.

The software is installed on both the windows computer and on leroy.

Data directories

When starting to take data, select (or make) a directory on the windows copmuter inside the Dropbox folder. This way, data gets synced to leroy automatically and you cna work with Python on either the windows computer or leroy as you like. Additionally, we can use Dropbox to immidiately transfer the data to other machines. Hopefully, leroy will be nfs mounted at some point, too…

Conversion and Analysis

Start the IPython command prompt on windows or on leroy by typing ipython --matplotlib in the terminal. All the following code then can be executed in IPython. First, import the module with the code for the X-ray polarimetry beamline:

>>> import xpolbeamline

Then, create an object that remembers the path to the raw data and the statsfile so you don’t have to type it every time. File path can be absolute or relative to the current working directory.

Warning

In Python, \ is an escape character for strings, for example \n mean “newline” or \t means TAB. On Windows \ is also used to separate directories. Thus, when you type the pathnames into the Python command line, you need to escape the \ with another \ like this: C:\\Users\\name.

So, let’s make an object that remembers our directories:

>>> myrun = xpolbeamline.UI(inpath='C:\\Users\\name\\Dropbox\\xpoldata\\3Oct17',
...             statspath='C:\\Users\\name\\Dropbox\\xpolstats\\stats_10_03_17.txt')

In general, white spaces and indentation at the beginning of code lines are important in Python, but here we just break the line inside of the ( ... ) because the pathnames just happen to be too long to fit, so that’s OK.

After LabView has written a the tif and txt file to that directory, we can just do:

>>> myrun.convert_display_newest()

to convert the most recently modified tif file in that directory to a fits image and event list and display diagnostic quick view plots.

The plots are interactive, there are little buttons on the top that allow you to zoom in and out, pan, or save the image to a file.

Using IPython

Both Python and IPython have extensive documentation. Essentially, IPython is just an enhanced shell for Python. Anything that can be done in plain Python, can be done in IPython, too, but the shell is a little nicer and supports additional features, e.g. in plain Python plotting windows as blocking, while IPython has the --matplotlib mode where plotting windows do not block the console.

Here are a few quick tricks:

• IPython autocompletes with the TAB key: myrun.<TAB> will list all members of the run object, in case you do not remember the exact name of a function.
• In the shell, use the “up arrow” and “down arrow” keys to find the most recently used commands. Edit and execute again as needed.
• Quick access to documentation: myrun.convert_display? will print the documentation for the method in the terminal (typically exit by pressing “q” like in the “less” program on the unix terminal).

Reference / API

xpolbeamline.ui Module

This module provides a quick interface for file conversion and quicklook display with sensible defaults for most things. Use this while taking data on the beamline, when time is short and a “good-enough” analysis with no knobs to turn is all you need.

Classes

UI(inpath, statspath[, outpath])

Simple User Interface to the xpolbeamline package

Class Inheritance Diagram