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0001 # Generation of Material Tables
0002
0003 Guide to generate material property tables for XML files for `DD4hep`.
0004
0005 ## Procedure
0006
0007 1. Build executables from source in `src/` by running `make`.
0008 2. Execute `bin/generate_material_tables`. This will produce XML nodes for each
0009 material and optical-surface property table, which can be copied into any
0010 relevant XML files. Plots of the property tables will also be produced, but note
0011 that step 3 will extend or override these plots; always refer to the plots from
0012 step 3 in place of those from step 2, since in some cases, the step 2 tables are
0013 out of date
0014 3. Extrapolate tables to broader ranges using `scripts/extrapolate_material_tables.py`;
0015 these tables should be used in place of the ones from step 2
0016
0017 ## Code
0018 - [`src/g4dRIChOptics.hh`](../src/g4dRIChOptics.hh): Common class hierarchy for
0019 dRICH material optical properties, originally from
0020 [cisbani/dRICh](https://github.com/cisbani/dRICh)
0021 - [`text/drich-materials.txt`](../text/drich-materials.txt): Geant4 text-file
0022 description of materials, needed along with `src/g4dRIChOptics.hh` for the
0023 generation of property tables
0024 - [`src/generate_material_tables.cpp`](../src/generate_material_tables.cpp):
0025 Executable for generating the XML nodes and plots
0026 - [`scripts/extrapolate_material_tables.py`](../scripts/extrapolate_material_tables.py):
0027 Extrapolate material property tables beyond `g4dRIChOptics`
0028 - [`src/surfaceEnums.h`](../src/surfaceEnums.h): helper methods for Geant4 surface
0029 properties
0030
0031 # Material Property Tables Status
0032
0033 ## Aerogel
0034 ### Material
0035 - using CLAS12 experimental points rescaled by Alessio/GEMC, in range 200 to 660 nm
0036 - except for absorption length, where we use data from Aerogel Factory
0037 - needed to do curve fits for extrapolation
0038 - [x] **EXTRAPOLATION**: refractive index
0039 - fit to 2nd order Sellmeier function
0040 - upper limit 660 nm extrapolated to 1000 nm
0041 - [x] **EXTRAPOLATION**: absorption length
0042 - linear fit to 870 nm and above only
0043 - upper limit extrapolated to 1000 nm
0044 - [x] **EXTRAPOLATION**: Rayleigh scattering length
0045 - fit to `lambda^4` dependence
0046 - upper limit 660 nm extrapolated to 1000 nm
0047 ### Surface
0048 - [ ] **TODO**
0049
0050 ## Airgap
0051 - using common `AirOptical`
0052 - no effect switching to `C2F6` (which disables it)
0053 - no extrapolation
0054
0055 ## Acrylic Filter
0056 ### Material
0057 - using (adjustable) cutoff of 300 nm
0058 - no effect switching to `C2F6` (which disables it)
0059 - no extrapolation
0060 ### Surface
0061 - [ ] **TODO**
0062
0063 ## Gas
0064 ### Material
0065 - currently 200-700nm, 10 points
0066 - straightforward to adjust in Evaristo's code, `g4dRIChOptics.hh`
0067 - [x] **EXTRAPOLATION**: refractive index
0068 - extrapolated to 200-1000nm, 16 points
0069 - done for both C2F6 and C4F10
0070 - [x] **EXTRAPOLATION**: absorption length
0071 - is constant
0072 - same range as refractive index
0073 - done for both C2F6 and C4F10
0074 - [ ] **TODO**: use Rayleigh scattering length?
0075 - also is constant, but not used in `epic`
0076 ### Surface
0077 - [ ] **TODO**?
0078
0079 ## Mirror
0080 ### Material
0081 - same as filter material
0082 - [ ] **TODO**: update to a more realistic material
0083 ### Surface
0084 - model exists from Evaristo's code, but we are not using this since reflectivity seems too low
0085 - instead, using constant 0.9 reflectivity for all wavelengths: 1-7 eV = 177-1240nm
0086 - no extrapolation, since wavelength range is large enough
0087 - [ ] **TODO**: update to a more realistic model or measurement
0088
0089 ## Sensors
0090 ### Material
0091 - Material is currently `AirOptical`, to correctly model the gas/sensor optical boundary
0092 - [ ] **TODO**: do this more correctly
0093 ### Surface
0094 - table `EFFICIENCY` is set to constant 1 for all wavelengths 1-7 eV = 177-1240nm
0095 - actual quantum efficiency is applied downstream in reconstruction
