Kipp & Zonen Brewer Mk III Operator's Manual page 103

Position 7 allows simultaneous observation through slits 3 and 5. Dark count-corrected counts are
stored in the BASIC F() array (refer to the Preliminary Data Reduction document for details). The
following algorithm is used to derive a value for instrument deadtime:
Assume Poisson statistics:
N
N N e τ ⋅
−
= ⋅
0
0
N
1
⎛ ⎞
0
log
τ
= ⋅ ⎜ ⎟
e
N N
⎝ ⎠
0
where:
N is the true count-rate (counts/sec),
o
N is the observed count-rate,
τ is the deadtime (sec). (The BASIC variable T1 is used for τ .)
1. As a first approximation set the true (unknown) count-rates equal to the observed count-
rates:
F ← F
ʹ'
3 3
F ← F
ʹ'
5 5
2. Compute an estimate for deadtime:
1
τ
←
F F
+ ʹ'
3
3. Revise the estimates for the true count-rates:
F
F F e ⋅ ʹ'
ʹ'
← ⋅ 3
3 3
F
⋅ ʹ'
F F e
ʹ'
← ⋅ 5
5 5
4. Iterate steps 2 and 3 until the value for T1 converges.
Deadtime measurements are made at both high and moderate light intensity levels by using two
different neutral-density filter settings (positions 0, 1 for Filterwheel #2); five measurements are
taken at the higher intensity, ten at the lower intensity.
Method:
The command DT is issued.
Following the usual five minute lamp warm-up, and a further 10 minutes for test to run, results will
be printed in a format similar to the following:
FILTER #1/1 AND FILTER #2/0
GMT
191054
191119
191143
191208
191233
48.705 ± .6
100
F F
+ ʹ' ʹ'
3
log
⋅
e
F
ʹ'
5 7
τ
τ
DEADTIME
4.94288936E-08
4.81299056E-08
4.93662915E-08
4.91343971E-08
4.84666031E-08
MKIII OPERATOR'S MANUAL
APPENDIX F FACTORY TESTS