Photon flux proportionality
If we compare the photon flux from the two runs with DU target
run 2467 (7770 positrons total)
and
run 2506 (30312 positrons total)
The average photon flux increased from 90 to 350 and the ratio is 350/90 = 3.9 .
In other way if we look at the ratio of the integral number of positrons produced during the runs 30312/7770 = 3.9
The number of neutrons used to do narmalization, i.e. the sum of the number of neutrons in three detectors placed at 0 deg left, 90 deg bottom and 0 deg right changed as follows:
run 2467: SUM(0-90-0) = 518 neutrons
run 2506: SUM(0-90-0) = 2195 neutrons
The neutron number ratio is 2195/518 = 4.2 .
If we consider another run and compare with the run 2467 (see above)
run 2522 (19571 positrons total)
If we look at the ratio of the integral number of positrons produced during the runs 19571/7770 = 2.52
run 2522: SUM(0-90-0) = 1271 neutrons
The neutron number ratio is 1271/518 = 2.45 .
So the relative photon flux change is proportional to the relative number of prompt fission neutrons produced and normalization procedure using the SUM(0-90-0) is correct normalization for the asymmetry calculation.