PRIMES
BeamMonitor BM+ with LDS 2.98
47
Revision 01/2018 EN
Review
This function checks whether the results and settings of the caustic measurement are within the reliable range.
OK
Not OK
(in the measuring planes
5 and 15)
Fig. 11.16: Result window of the evaluation function
Under “spread” the average standard deviation of the caustic fit according to the 2
nd
moment method radii
is stated. A “tick” (
) is set if the standard deviation is smaller than 3.5 % and if all of the measuring values
lie within a range of ± 3 * standard deviation.
Valued functions
Test criterion
Positive evaluation
Spread
Average relative standard devia-
tion of the caustic fit according
to the 2nd moment method
Standard deviation < 3.5 %, all measurement values
within a range of ± 3 * standard deviation
Fill factor
The proportion beam diameter
to the measuring window size
In the range 0.3 – 0.6
Z-range
Measuring range in z-direction
At least 4 Rayleigh-lengths
Measurement planes
Number of measurement planes
per Rayleigh length
At least 3 measurement planes per Rayleigh length
(Z
Min
+Z
r
) < Z
0
< (Z
Max
−Z
r
) Minimum measurement range
above and below the focusing
plane
The focus lies within the minimum measurement
range and this range accounts for at least one Ray-
leigh length in every z-direction
Signal/noise ratio
Examines the signal-to-noise
ratio
FocusMonitor: S/N > 40
Signal override
Examines the maximum power
density value
Below 4000 Counts
Tab. 11.1: Criteria for the evaluation
If all criteria are fulfilled, the measuring results have a high reliability. The absolute accuracy can not be stated
from the standard deviation from the fits as all the systematic measuring errors as well as the accuracy of
the calibration are additionally taken into account when it comes to the absolute error.
