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Forum: Processes Involving Optical Photons
Re: Question Sciintillation Emission Spectrum table (Ron Mathis)
Date: 21 Jan, 2010
From: Benton Pahlka <Benton Pahlka>

Hi Ron,

I have found the same issue and I tend to agree that the interpolation isn't great. To fix this problem, I read my arrays of inputs from external text files with a value for each integer wavelength (or energy). From 200 nm to 700 nm for example, I have 500 entries.

You can generate these files with any kind of plot digitizer available on the internet. This reduces the interpolation distance and gives a smoother spectrum.

In my opinion, because all my inputs are in principle highly wavelength dependent, I do this for all my input files. In the end, I compare this with measurements from a spectrophotometer which has around 1 nm resolution. For me, 1 nm resolution is good enough.

The other advantage is that I don't have the warnings that G4 produces with values being out of range which gives me more confidence that I've read the values in correctly.

Cheers,

Benton

On Thu, 21 Jan 2010 17:47:42 GMT, Ron Mathis wrote:

> Hello, I am trying to insert an Emission Spectrum table for the
> scintillator I am using. The resulting spectrum of the optical photons
> at the photocathode consists of disconnected sections of points, many of
> which have the wrong slope or a negative slope when it should be
> positive etc. The number of disconnected sections matches the number of
> entries in the table. If the number of entries is changed the number of
> disconnected sections changes accordingly. It is behaving as if the
> interpolation between points is not working correctly. The following is
> the code I am using.
> 
>   G4Material* EJ260 = new G4Material("EJ260",density= 1.023*g/cm3, nel=2);
>   EJ260->AddElement(H, natoms=10);
>   EJ260->AddElement(C, natoms= 9); 
> 
>  const G4int NUMej = 26;
>   G4double ej_PhotonEnergy[NUMej] = {2.07*eV, 2.088*eV, 2.111*eV, 2.133*eV,
>                                      2.156*eV, 2.18*eV, 2.204*eV, 2.229*eV,
>                                      2.254*eV, 2.28*eV, 2.307*eV, 2.334*eV,
>                                      2.362*eV, 2.39*eV, 2.42*eV, 2.449*eV,
>                                      2.48*eV, 2.511*eV, 2.544*eV, 2.577*eV,
>                                      2.61*eV, 2.645*eV, 2.681*eV, 2.718*eV,
>                                      2.756*eV, 4.5*eV};
>   G4double scint_FAST[NUMej] = {0., 0.01, 0.02, 0.03, 0.04, 0.05, 0.06,
>                                 0.085, 0.12, 0.16, 0.22, 0.28, 0.32, 
>                                 0.36, 0.44, 0.6, 0.83, 1.0, 0.9, 0.62, 
>                                 0.36, 0.12, 0.01, 0., 0., 0.};
>   G4double ej_RIND[NUMej] = {1.58, 1.58, 1.58, 1.58, 1.58, 1.58, 1.58, 
>                              1.58, 1.58, 1.58, 1.58, 1.58, 1.58, 1.58,
>                              1.58, 1.58, 1.58, 1.58, 1.58, 1.58, 1.58,
>                              1.58, 1.58, 1.58, 1.58, 1.58};  // refractive index
>   G4double ej_ABSL[NUMej] = {2.*m, 2.*m, 2.*m, 2.*m, 2.*m, 2.*m, 2.*m, 
>                              2.*m, 2.*m, 2.*m, 2.*m, 2.*m, 2.*m, 2.*m,
>                              2.*m, 2.*m, 2.*m, 2.*m, 2.*m, 2.*m, 2.*m,
>                              2.*m, 2.*m, 2.*m, 2.*m, 2.*m};
>                              // atten length (Absorption Length)
>   G4MaterialPropertiesTable* EJ260_mt = new G4MaterialPropertiesTable();
>   EJ260_mt->AddProperty(
>             "FASTCOMPONENT", ej_PhotonEnergy, scint_FAST, NUMej);
>   EJ260_mt->AddProperty("RINDEX", ej_PhotonEnergy, ej_RIND, NUMej);
>   EJ260_mt->AddProperty("ABSLENGTH", ej_PhotonEnergy, ej_ABSL, NUMej);
> 
>   EJ260_mt->AddConstProperty("SCINTILLATIONYIELD", 9200./MeV);
>   EJ260_mt->AddConstProperty("RESOLUTIONSCALE", 2.0);//Broaden distribution
>   EJ260_mt->AddConstProperty("FASTTIMECONSTANT", 9.2*ns);
>   EJ260_mt->AddConstProperty("YIELDRATIO", 1.0); //No slow component
>   EJ260->SetMaterialPropertiesTable(EJ260_mt);
> 
> Any suggestions? Thank you for your help Ron Mathis
> 

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