Bias of X-ray generator

Bias is useful for the increase of intensity?
Focus size:
Bias and focus size was tested for MacScience M18XCE (rotating anode). Its range was from 0 to 80 V, and the foucus image is...

It seems to be useful for the increase of brightness.
Effect of bias for intensity counts is tested by using reflection images.
Sample:

C36 H40 O12 S2
SPG: P212121
a = 10.903(2)
b = 13.068(2)
c = 24.400(4)
V = 3476.5(11)
50 kV-180 mA 4 sec-expose
omega-width=0.3 degree.

Digital maps of this spot
(total 9 images) are here!		   
Overall image
Spot close-up
Method:

10 Frames sets are measured changing bias from 0 to 250 V (9 sets: 0, 20, 40, 60, 80, 100, 150, 200, 250 V), and the total counts, peak top and intensity are compared through 8 spots. (Bruker AXS SMART)
   [These values do NOT reflect the proper intensity of each reflection. Only, counts on 2D-plane.]
Results: