|20070614||DOMINANT calibration using GDOM calibration page uploaded|
In order to improve our knowledge about photon absorption and reflection
inside DOM module, we developed full Monte-Carlo simulator based on
Geant4 (DOMINANT). The DOMINANT traces
photon path with refraction and reflection at the boundaries between
different materials (ice and glass, etc.) (*1) and absorption inside
the glass and gel. It also simulates photons from charged particles,
for example, the cherenkov photons which produced by direct muon hits
inside the DOM sphere.
(*1: 2005/02/10 Now we artificially exclude these reflection and refraction, because of a bug inside the program. )
How to construct PMT solid
In order to obtain actual hit point of photons at PMT photo cathode, we constructed geometrical shape of PMT as one of the G4VSolid. Because our PMT shape is represented by some combination of Constructive Solid Geometry (CSG) Solids, we used G4UnionSolid to construct PMT.
Absorption Length vs wave length of photons in glass and gel
The DOMINANT requires absorption length and refractive index for all materials. Elisa Resconi measured the penetration ratios of glass and gel. We calculated the absorption length from her data.
Using the DOMINANT, we generated acceptance table for our 13inch DOM. Because the Photonics calculates an amplitude / 1m^2, the photon beam is injected to the DOM from 1m^2 beam spot with an off-axis angle theta. The acceptances as a function of wavelength and off-axis angle are obtained as follows.
The colors of spots indicates off-axis angle, angle between beam direction and PMT axis. 0 degree means beam injected from top of the photo-cathode of PMT. Taking a careful look of the figure, each shape of acceptance curve looks similar. It may be good approximation to separate these two variables, wavelength and off-axis angle, as follows:
within all range of our assuming wavelength.
The acceptance of photons as a function of wavelength
The wavelength_acceptance is defined as follows
at off-axis angle theta = 0.
QE convolution (acceptance of photo-electrons)
Convoluting the acceptance table and QE curve, we can get acceptance of photo-electrons as a function of wavelength. This table would be used by AMANDA simulator.
The acceptance of photo-electrons is calculated by
The acceptance of photons as a function of injection angle
The angle acceptance is calculated by
as a function of injection angle theta (at DOM local coordinate) and
Ray trace&BG sim
PMT Handy c++ sim
Back to the
Chiba Icecube Home