1 files changed, 2 insertions, 0 deletions
diff --git a/optics.py b/optics.py
index 6bf86ff..dea5a20 100644
--- a/optics.py
+++ b/optics.py
@@ -49,6 +49,8 @@ r7081hqe_photocathode.set('reflect_diffuse', 1.0 - r7081hqe_photocathode.detect[
 
 # water data comes from 'lightwater_sno' material in the SNO+ optics database
 water = Material('water')
+water.density = 1.0 # g/cm^3
+water.composition = { 'H' : 0.1119, 'O' : 0.8881 } # fraction by mass
 water.absorption_length = \
     np.array([[ 200. ,   57.51539993],
               [ 220. ,   64.22219849],