SCNT: Scintillator and wavelength shifter (WLS) additive optical data

                Titles:  SCNT: Scintillator and wavelength shifter (WLS) additive optical data
                ==============================================================================
 
Contact:  N. Tagg, Oxford
 

 
Titles Files
------------
 
scintillator.dat
 
 
Verification
------------
 
SCNT
------
 
Description
-----------
 
The SCNT banks contain data describing the properties of scintillator,
wavelength-shifter, or simply an absorber.  These are called
'additives', and can be added to the materials in the MEDA bank.

The bank number is used as the ID number of a given medium.
 
Data Words - SCNT
-------------------
 
        Fixed length Database Header.  See titles_dbhdr.html
 
        Data types: B(bit), I, F, D(double), H(hollerith 4 char)
 
1   H NAME              The name of the additive.
 
6   F QE                The quantum efficiency of the scintillator, in units of photons/MeV.
                        This is used in computing the photon yield for an ionizing particle.
	                See note 1.

7   F BIRKS             The Birk's constant of the scintillator, in Mev/cm

8   I NUM_TIME_COMPONENTS  The number of components in the emission time spectrum

9   F TIME_COMPONENTS   Array with decay time data, KSCNT_NUM_TIME_COMPONENTS words.
		        See note 2.

19  I EMM_MODE          Mode flag for how to interpret emission spectrum data. See note 3.

20  I EMM_N             Number of components in the emission profile data. See note 3.

21  F EMM_DATA          Array of emission spectrum data. See note 3.
			Synonyms: EMM_WAVELENGTHS = EMM_DATA 
	                          EMM_SPECTRUM    = EMM_DATA + 20

61  I ABS_N             Number of points in absorption spectrum. See note 4.

62  F ABS_WAVELENGTHS   Array of KSCNT_ABS_N wavelengths in the absorption spectrum. In nanometers

82  F ABS_SPECTRUM      Array of KSCNT_ABS_N absorption lengths, in cm.

92  I WLSQE_N           Number of words in WLS quantum efficiency spectrum

93  F WLSQE_WAVELENGTHS Array of KSCNT_WLSQE_N wavelengths. In nanometers

113 F WLSQE_SPECTRUM    Array of KSCNT_WLSQE_N quantum efficiencies. See note 5

 
Notes
-----
 
1)   Scintillation light. If KSCNT_QE is non-zero, the additive will be
     treated like scintillator. Ionizing particles will generate
     scintillation photons in the associated medium. The number of photons
     created by a track of energy deposition dE and track length dX is:

	NPHOT = concentration * KSCNT_QE * dE / (1 + KSCNT_BIRKS * dE/dX)

     where the concentration is taken from the associated MEDA bank.

	
2)   Decay time.  The scintillator or wavelength shifter is assumed to
     emit light over time with an probability described as the sum of
     several exponentials.

     Example: a fluor with two decay components, described by:
	I(t)t = 0.3 exp(-t/10ns) + 0.7 exp(-t/20ns)
        is represented as:
        KSCNT_NUM_TIME_COMPONENTS = 2
        KSCNT_TIME_COMPONENTS:
  	  0.3 10.0
	  0.7 20.0

3)   Emission spectrum. The emission spectrum of the additive can be
     described in one of two ways:

	EMM_MODE = 0   The emission is chosen from a user-defined spectrum.  
                       There are KSCNT_EMM_N wavelengths at
	               position KSCNT_EMM_WAVELENGTHS and KSCNT_EMM_N 
                       intensities at position KSCNT_EMM_SPECTRUM.

	EMM_MODE = 1   The emission spectrum is represented by a sum of Gaussian peaks. 
                       There are KSCNT_EMM_N such peaks. Each peak is represented by 
                       three values: Fractional intensity, mean wavelength, and width.
		       E.g. 1   
			    1.0   450.  10.   
			would represent a single line source centered at 450 nm with 
                       an RMS width of 10 nm.

     In both cases, the spectrum is normalized at run-time.

4)   Absorption spectrum. This should be filled for both scintillator
     and WLS.  KSCNT_ABS_N points of absorption length can be given, just
     like for the MEDA banks.

     Absorption for the medium is treated as an admixture with the basic
     medium.  If the concentration of additive is zero, the absorption
     is just like that described in the medium. If the concentration is
     set to 1, the absorption is set to that of the additive. If in
     between, the absorption is a linear admixture of the two.

5)   WLS QE.  If the medium acts as a wavelength shifter (i.e. it has a
     chance of re-emitting a photon after absorbing it) the WLSQE
     should be set to non-zero.  The WLSQE is set as a function of the
     incident photon wavelength.  The SPECTRUM words should vary from 0
     to 1, where 1 represents a perfect wavelength shifter (all photons
     are re-emitted).