A Python (read-only) implementation of the EventIO data format invented by Konrad Bernloehr as used for example by the IACT extension for CORSIKA: https://www.ikp.kit.edu/corsika

Documentation of the file format: https://www.mpi-hd.mpg.de/hfm/~bernlohr/sim_telarray/Documentation/eventio_en.pdf

Most blocks of the IACT extension and SimTel are implemented. The following blocks are known, but reading their data is not (yet) implemented, because we do not have any test files containing these objects.

If you want support for these objects, please open an issue.

pip install eventio

One may iterate over an instance of IACTFile class in order to retrieve events. Events have a small number of fields. The most important one is the photon_bunches field, which is dictionary mapping telescope ids to a simple structured np.array, containing the typical parameters Cherenkov photon bunches in CORSIKA have, like:

• x, y coordinate in the observation plane (in cm)
• direction cosine cx, cy in x and y direction of the incident angle of the photon
• wavelength lambda of the photon (in nm)
• number of photons associated with this bunch
• the time since the first interaction (in ns, I believe)
• the production height of the photon bunch (called zem)
• a bool flag, whether the photon was scattered in the atmosphere

An event has the following attributes: * header: a namedtuple containing the Corsika Event Header data * end_block: a numpy array containing the Corsika Event End data * time_offset, x_offset, y_offsett, the offset of the array

This prints energy and the number of photons for the first telescope in every event:

import eventio

with eventio.IACTFile('eventio/resources/one_shower.dat') as f:
    for event in f:
        print(event.header.total_energy)
        print(event.photon_bunches[0]['photons'].sum())

If you like to plot the origin of the Cherenkov photons of the first event in file eventio/resources/one_shower.data for the first telescope, have a look into this example

It might look similar to this picture:

an example shower

import eventio

with eventio.SimTelFile('eventio/resources/gamma_test.simtel.gz') as f:

    print(len(f.telescope_descriptions))
    for array_event in f:
        print(array_event['mc_shower']['energy'])

We provide three commandline tools, to look into eventio files.

To get an overview over the structure of a file, use eventio_print_structure, for larger files, you might want to pipe its output into e.g. less:

$ eventio_print_structure eventio/resources/gamma_test.simtel.gz
History[70]
    HistoryCommandLine[71]
    HistoryConfig[72]
    HistoryConfig[72]
    And 127 objects more of the same type
...
RunHeader[2000](run_id=31964)
MCRunHeader[2001]
MCRunHeader[2001]
InputCard[1212]
InputCard[1212]
CameraSettings[2002](telescope_id=1)
CameraOrganization[2003](telescope_id=1)
PixelSettings[2004](telescope_id=1)
DisabledPixels[2005](telescope_id=1)
CameraSoftwareSettings[2006](telescope_id=1)
DriveSettings[2008](telescope_id=1)
PointingCorrection[2007](telescope_id=1)
CameraSettings[2002](telescope_id=2)
CameraOrganization[2003](telescope_id=2)

To get table of all object versions and counts in a file, use eventio_print_object_information, it can also print json if given the --json option

$ eventio_print_object_information eventio/resources/gamma_test.simtel.gz
 Type | Version | Level | #Objects | eventio-class
------------------------------------------------------------
   70 |       1 |     0 |        3 | simtel.objects.History
   71 |       1 |     1 |        3 | simtel.objects.HistoryCommandLine
   72 |       1 |     1 |    32840 | simtel.objects.HistoryConfig
 1212 |       0 |     0 |        2 | iact.objects.InputCard
 2000 |       2 |     0 |        1 | simtel.objects.RunHeader
 2001 |       4 |     0 |        2 | simtel.objects.MCRunHeader
 2002 |       2 |     0 |       98 | simtel.objects.CameraSettings
 2002 |       3 |     0 |       28 | simtel.objects.CameraSettings
 2003 |       1 |     0 |      126 | simtel.objects.CameraOrganization
 2004 |       2 |     0 |      126 | simtel.objects.PixelSettings
 2005 |       0 |     0 |      126 | simtel.objects.DisabledPixels
 2006 |       0 |     0 |      126 | simtel.objects.CameraSoftwareSettings
 2007 |       0 |     0 |      126 | simtel.objects.PointingCorrection
 2008 |       0 |     0 |      126 | simtel.objects.DriveSettings
 2009 |       2 |     1 |       10 | simtel.objects.TriggerInformation
 2010 |       0 |     0 |       10 | simtel.objects.ArrayEvent
 2011 |       1 |     2 |       50 | simtel.objects.TelescopeEventHeader
 2013 |       3 |     2 |       50 | simtel.objects.ADCSamples
 2014 |       5 |     2 |       44 | simtel.objects.ImageParameters
 2016 |       1 |     2 |       49 | simtel.objects.PixelTiming
 2020 |       1 |     0 |      122 | simtel.objects.MCShower
 2021 |       1 |     0 |     1214 | simtel.objects.MCEvent
 2022 |       0 |     0 |      126 | simtel.objects.CameraMonitoring
 2023 |       2 |     0 |      126 | simtel.objects.LaserCalibration
 2026 |       2 |     0 |       21 | simtel.objects.MCPhotoelectronSum
 2027 |       0 |     2 |       93 | simtel.objects.PixelList
 2100 |       0 |     1 |       42 | simtel.objects.TrackingPosition
 2200 |       1 |     1 |       50 | simtel.objects.TelescopeEvent
------------------------------------------------------------

To plot histograms stored in an eventio file (Type 100), use eventio_plot_histograms.

$ eventio_plot_histograms gamma_20deg_180deg_run99___cta-prod3_desert-2150m-Paranal-merged_cone10.simtel.gz

Histogram of Impact distance vs log10(E / TeV)

For more low level access to the items of an EventIO file (or to implement a higher level abstraction like IACTFile) one can use the EventIOFile class which gives access to the objects and subobjects in EventIO files.

This is how our test file looks like in the low level view:

In [3]: with EventIOFile('eventio/resources/one_shower.dat') as f:
   ...:     for obj in f:
   ...:         print(obj)
   ...:         if obj.header.only_subobjects:
   ...:             for subobj in obj:
   ...:                 print('   ', subobj)
CORSIKARunHeader[1200](size=1096, only_subobjects=False, first_byte=16)
CORSIKAInputCard[1212](size=448, only_subobjects=False, first_byte=1128)
CORSIKATelescopeDefinition[1201](size=20, only_subobjects=False, first_byte=1592)
CORSIKAEventHeader[1202](size=1096, only_subobjects=False, first_byte=1628)
CORSIKAArrayOffsets[1203](size=16, only_subobjects=False, first_byte=2740)
CORSIKATelescopeData[1204](size=6136, only_subobjects=True, first_byte=2772)
    IACTPhotons(length=6124, n_bunches=382)
CORSIKAEventEndBlock[1209](size=1096, only_subobjects=False, first_byte=8924)
CORSIKARunEndBlock[1210](size=16, only_subobjects=False, first_byte=10036)