Update benchmark and fix type instability

README.md

@@ -45,16 +45,15 @@ julia> using MuonLight
 julia> dp = MuonLight.DispersionARCA
 BasicDispersion(350.0, 1.3201, 1.4e-5, 16.2566, -4383.0, 1.1455e6)
 
-julia> @benchmark MuonLight.directlight($dp, R, θ, ϕ) setup=begin; R=(rand()+1)*300; θ=rand()*2π; ϕ=rand()*2π; end
-BenchmarkTools.Trial: 10000 samples with 11 evaluations.
- Range (min … max):  1.004 μs …  37.780 μs  ┊ GC (min … max): 0.00% … 92.37%
- Time  (median):     1.042 μs               ┊ GC (median):    0.00%
- Time  (mean ± σ):   1.062 μs ± 521.187 ns  ┊ GC (mean ± σ):  0.66% ±  1.30%
+julia> @benchmark MuonLight.directlight($dp, $MuonLight.PMTKM3NeT, R, θ, ϕ) setup=begin; R=(rand()+1)*300; θ=rand()*2π; ϕ=rand()*2π; end
+BenchmarkTools.Trial: 10000 samples with 196 evaluations.
+ Range (min … max):  466.199 ns …   6.137 μs  ┊ GC (min … max): 0.00% … 88.89%
+ Time  (median):     477.469 ns               ┊ GC (median):    0.00%
+ Time  (mean ± σ):   488.605 ns ± 175.758 ns  ┊ GC (mean ± σ):  1.25% ±  3.18%
 
-         ▄██▇ ▄▁                                               
-  ▂▂▂▃▅▁█████▁███▆▆▁▆▇▆▅▅▁▄▃▃▃▃▁▄▄▄▃▃▁▃▃▂▂▂▁▂▂▂▂▂▁▂▂▂▂▂▁▂▂▂▂▂ ▃
-  1 μs            Histogram: frequency by time        1.19 μs <
-
- Memory estimate: 1.12 KiB, allocs estimate: 62.
+    ▃▅▆▇██▆▃▁▁▂▃▃▄▄▅▄▃▁▁                                        ▂
+  ▅████████████████████████████▇▇██▆▅▆▆▅▄▅▅▆▅▅▅▄▄▇▄▃▆▅▁▁▅▄▃▃▄▃▅ █
+  466 ns        Histogram: log(frequency) by time        564 ns <
 
+ Memory estimate: 320 bytes, allocs estimate: 7.
 ```

src/MuonLight.jl

@@ -120,7 +120,7 @@ end
 
 Returns the absorption length [m] for a given wavelength [nm].
 """
-absorptionlength = LinearInterpolator(
+const absorptionlength = LinearInterpolator(
     [0, 290, 310, 330, 350, 375, 412, 440, 475, 488, 510, 532, 555, 650, 676, 715, 720, 999999],
     [0.0, 0.0, 11.9, 16.4, 20.6, 29.5, 48.5, 67.5, 59.0, 55.1, 26.1, 19.9, 14.7, 2.8, 2.3, 1.0, 0.0, 0.0],
     NoBoundaries()