pass arm cavity and molecular gas properties to res gas function

* pass the cavity struct computed with arm_cavity to residual_gas_cavity instead of having it compute the parameters again
* pass the properties of the molecular species separately so that the function can be generalized for multiple species

gwinc/ifo/noises.py

@@ -763,7 +763,9 @@ class ExcessGas(nb.Noise):
     )
 
     def calc(self):
-        n = noise.residualgas.residual_gas_cavity(self.freq, self.ifo)
+        cavity = arm_cavity(self.ifo)
+        n = noise.residualgas.residual_gas_cavity(
+            self.freq, self.ifo, cavity, self.ifo.Infrastructure.ResidualGas)
         # FIXME HACK: it's unclear if a phase noise in the arms like
         # the excess gas noise should get the same dhdL strain
         # calibration as the other displacement noises.  However, we

gwinc/noise/residualgas.py

@@ -7,7 +7,7 @@ from numpy import sqrt, log, pi
 from .. import const
 
 
-def residual_gas_cavity(f, ifo):
+def residual_gas_cavity(f, ifo, cavity, species):
     """Residual gas noise strain spectrum in an evacuated cavity.
 
     Noise caused by the passage of residual gas molecules through the
@@ -15,6 +15,8 @@ def residual_gas_cavity(f, ifo):
 
     :f: frequency array in Hz
     :ifo: gwinc IFO structure
+    :cavity: arm cavity structure
+    :species: molecular species structure
 
     :returns: arm displacement noise power spectrum at :f:
 
@@ -28,26 +30,19 @@ def residual_gas_cavity(f, ifo):
     expansion of exp, to speed it up.
 
     """
-    Lambda = ifo.Laser.Wavelength
     L = ifo.Infrastructure.Length
     kT = ifo.Infrastructure.Temp * const.kB
-    P = ifo.Infrastructure.ResidualGas.pressure
-    M = ifo.Infrastructure.ResidualGas.mass
-    alpha = ifo.Infrastructure.ResidualGas.polarizability
-    R1 = ifo.Optics.Curvature.ITM
-    R2 = ifo.Optics.Curvature.ETM
-
-    rho = P /(kT)                                   # number density of Gas
-    v0 = sqrt(2*kT / M)                             # mean speed of Gas
-
-    g1 = 1 - L/R1                                   # first resonator g-parameter of the ITM
-    g2 = 1 - L/R2                                   # second resonator g-parameter of the ETM
-    waist = L * Lambda / pi
-    waist = waist * sqrt(((g1*g2)*(1-g1*g2))/((g1+g2-2*g1*g2)**2))
-    waist = sqrt(waist)                             # Gaussian beam waist size
-    zr = pi*waist**2 / Lambda                       # Rayleigh range
-    z1 = -((g2*(1-g1))/(g1+g2-2*g1*g2))*L           # location of ITM relative to the waist
-    z2 =  ((g1*(1-g2))/(g1+g2-2*g1*g2))*L           # location of ETM relative to the waist
+    P = species.pressure
+    M = species.mass
+    alpha = species.polarizability
+
+    rho = P / (kT)                   # number density of Gas
+    v0 = sqrt(2*kT / M)              # mean speed of Gas
+
+    waist = cavity.w0                # Gaussian beam waist size
+    zr = cavity.zr                   # Rayleigh range
+    z1 = -cavity.zBeam_ITM           # location of ITM relative to the waist
+    z2 = cavity.zBeam_ETM            # location of ETM relative to the waist
 
     # The exponential of Eq. 1 of P940008 is expanded to first order; this
     # can be integrated analytically