PHYS01200804001 Sohrab Abbas - Homi Bhabha National Institute

I
I
max min
C I
max
I
min
. (42)
The beam contrast equals unity for the O-beam, in ideal case. The contrast values calculated for the
H beam with the illumination of the entire Bormann fan, lie below about 0.5. Further, Due to the
extremely low phase space density of neutron beams (10 -14 ), one observes pure single particle selfinterferences.
Using Eq.(39b), the two intensities (Eqs.(41a-41b)) can be written as
I 4I (y, t) 1
I (y, t)
ttt 2
O H H
I I (y, t) 1
2I (y, t)
ttt
H H H
2
(43)
for χ = 0 and
I 0
ttt
O
I I (y, t)
ttt
H
H
(44)
for χ = . For χ = , the sum of the O and H intensities appears in the H-beam and corresponds to
the total intensity diffracted by the mirror, since the two forward diffracted beams from the mirror
are lost to the interferometer (Fig.7). At χ = 0, the two intensities exhibit extrema in addition to
those caused by the extrema in I H (y,t), discussed earlier. Thus in the region y 2