PPC (Photon Propagation Code)

This page was written by Martin Wolf with minor updates from Dima. Some of the content is outdated, i.g., the cmake no longer makes the ppc-cli. It is still possible to compile the stand-alone executable with “make gpu” or “make cpu” in the private/ppc/gpu directory. Please refer to the web pages linked below for more explanation on using the stand-alone ppc application. Much of the discussion there also applies to the icetray module.

To start using the icetray module right away, take a look at the run.py script that can be configured to process nugen/corsika data and simulate flashers/standard candles. Use the script “make.sh” to compile all parts of the icetray module at once.

Introduction

PPC was written by Dima (Dmitry Chirkin). It computes the propagation of (Cherenkov) photons inside the ice, in a “real time” fashion, i.e. without the use of binning and tables (as is done in Photonics). It uses the six-parameter ice model from Kurt Woschnagg [WOS2006]. For an explanation of the used formulas in ice.cxx see the paper by Dima [CHI2009]. For the Cerenkov light production a parametrization by C.H. Wiebusch [WIE1995] (pages 92-96) is used.

The project’s website by Dima can be found at https://icecube.wisc.edu/~dima/work/WISC/ppc/.

There is also a wiki page about ppc.

PPC can be used as standalone application (ppc-cli) and as IceTray module (i3ppc).

Using PPC as standalone application

PPC as standalone application (ppc-cli) can be used for three different things:

  1. printing out the used ice model parameters By invoking “WFLA=wavelength ppc-cli -”, e.g. “WFLA=380 ppc-cli -”, with the wave length of the light in nanometers, ppc prints out a table with depth, absorption coefficient, scattering coefficient, respectively.

  2. Read in charged tracks from STDIN and produce photons according to these tracks, propagate them and print out hits to STDOUT when photons hit a DOM. By invoking “ppc-cli seed”, ppc gets the seed value for the random generator from the command line argument. Afterwards, it reads in the track data from STDIN. Each line represents one track. The track format is defined by the F2K format [F2K2000] and is as follows:

    TR int int name x y z theta phi length energy time

    TR stands for track and is a character constant. The first two integer values are not used by ppc. The name column specifies the track type. Possible values are: “amu+”, “amu-” and “amu” for muons, “delta”, “brems”, “epair”, “e+”, “e-” and “e” for electromagnetic cascades and “munu” and “hadr” for hadronic cascades. x, y and z are the vector components of the track’s initial position in meters. theta and phi is the track’s theta and phi angle in degree, respectively. length is the length of the track in meter. It is only required for muons because cascades are treated as point-like sources. energy is the track’s initial energy in GeV. time is the track’s initial time in nanoseconds.

    When a produced and propagated photon hits a DOM ppc prints out that hit in the following format:

    HIT string_no om_no time n_z

    HIT is a character constant. string_no is the number of the string that was hit. om_no is the number of the DOM that was hit. time is the time in nanoseconds when the DOM was hit. n_z is the z component of the photon’s unit direction vector when it was hitting the DOM.

  3. Producing a flasher run by flashing one DOM. By invoking

    WFLA=405 ppc-cli string_no dom_no num seed

    with four arguments it produces a flasher run by flashing one specific DOM. string_no and dom_no is the string and DOM number, respectively. num is the number of photons that should be produced. seed is the seed value for the random number generator.

    ppc sets that DOM as source for all produced photons. It initiates the ice with a wavelength of 405 nm. The average theta angle of all emitted photons will be 90 degrees. The phi angles of the emitted photons are randomly drawn (0 < phi < 2PI).

    When a photon hits a DOM the same output than described in number 2 is produced.

References

[WOS2006]

Optical properties of deep glacial ice at the South Pole, Kurt Woschnagg et al., Journal Of Geophysical Research, VOL. 111, D13203, 2006

[CHI2009]

Study of ice transparency with IceCube flashers, Dmitry Chirkin, IceCube internal report 200911002

[WIE1995]

Ph.D. thesis, The Detection Of Faint Light in Deep Underwater Neutrino Telescopes, C.W. Wiebusch, 1995

[F2K2000]

F2000: A standard AMANDA offline event format, https://www.zeuthen.desy.de/~steffenp/f2000/