The main vertical bends in H4 are B3/B4 (+41 mr, 6 MBN's) at the bottom of TT81 and B6/B7 (-41 mr, 6 MBN's) at the top of TT81 .
A general problem at low energy is the stability and precision of low currents
in the rectifiers .
At high energy two rectifiers are needed for B3/B4 .The same is of course also
true for B6/B7.
At low energy higher stability and precision is obtained if one works only with
one rectifer i.e. with doubled currents.
In order to obtain that with a minimum change of the effective bend point the
following layout has been adopted.
The values above indicates in meters the distance from the first element of B3.
In the low energy "wiggling" mode B3=B6=0 and only B4 and B7 are used. This means that the effective bending point is moved 0.75 m downstream . As the total bending angle is 41 mr we get a shift of - 750 *0.041mm = -30 mm at the level of B3/B4. The magnification to C6 being -1 implies that the shif at the level of C6 is 30 mm.