diff --git a/src/cristallina/channels.py b/src/cristallina/channels.py
index b176061..bae3242 100644
--- a/src/cristallina/channels.py
+++ b/src/cristallina/channels.py
@@ -8,8 +8,16 @@ EVR = 'SAR-CVME-TIFALL6:EvtSet'
 # Jungfrau 1.5M detector
 JF = 'JF16T03V01'
 
+# Jungfrau 8M detector
+JF_8M = "JF17T16V01"
+
 # PSSS
 PSSS_X = 'SARFE10-PSSS059:SPECTRUM_X'
 PSSS_Y = 'SARFE10-PSSS059:SPECTRUM_Y'
 PSSS_SUM = 'SARFE10-PSSS059:SPECTRUM_Y_SUM'
 PSSS_COM = 'SARFE10-PSSS059:SPECT-COM'
+
+# Beam position monitors
+PBPS149_intensity = "SAROP31-PBPS149:INTENSITY_UJ"
+PBPS113_intensity = "SAROP31-PBPS113:INTENSITY_UJ"
+PBPS053_intensity = "SARFE10-PBPS053:INTENSITY"
\ No newline at end of file
diff --git a/src/cristallina/utils.py b/src/cristallina/utils.py
index 906c939..cc866aa 100644
--- a/src/cristallina/utils.py
+++ b/src/cristallina/utils.py
@@ -638,12 +638,10 @@ def gauss_fit(x, y, fit_details=None, plot=None):
 def xray_transmission(energy, thickness, material="Si", density=[]):
     """Calculate x-ray tranmission for given energy, thickness and material. Default material is Si. Add material=element as a string for another material. Density as optional parameter"""
 
-    mu = material_mu(material, energy)
-
     if density == []:
         mu_array = material_mu(material, energy)
     else:
-        mu_array = material_mu(formula, energy, density=density)
+        mu_array = material_mu(material, energy, density=density)
 
     trans = np.exp(
         -0.1 * (thickness * 1000) * mu_array