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There is a problem w/ your write-up. Check that you have valied entries for \$CAID and \$Campn in your analysis.php file. If that checks out, then Contact Stansberry"; return ; } // get first matching task $row = mysql_fetch_array($result); $title = $row["title"]; $princ = $row["principal"]; $deputy= $row["deputy"]; $campn0 = $row["campn0"]; $aorkeys = $row["aorkeys"]; // get real name of principal, deputies $princ = ioc_get_person($princ); $princ = $princ[0]; $deps = explode(",",$deputy); foreach ($deps as $depty) { $depty = trim($depty); $depty = ioc_get_person($depty); $depty = $depty[0]; $depty = explode(",",$depty); $depty = $depty[0]; // last names only $deplist[] = $depty; } $deplist = implode(", ", $deplist); $caid = sprintf("%03d",$caid); $file = "mips-".$caid.$campn.".analysis.php"; // if more matches, append the AORKEYS from those $numrows = mysql_num_rows($result); if ($numrows > 1) { $aorkeys = " " . $numrows . " Task Executions: ". $aorkeys; for ($i=0;$i < mysql_num_rows($result); $i++) { $row = mysql_fetch_array($result); $morekeys = $row["aorkeys"]; $aorkeys = $aorkeys .'; '.$morekeys; } } // END PHP. ?> <? echo "MIPS-$caid, Campaign $campn IOC/SV Analysis"; ?>

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Task Outcome Summary

DATA STATUS: Nominal
TASK OUTCOME: Nominal

Abstract

The goal of this task is to determine the best detector bias for the MIPS 70um and 160um arrays. Four performance criteria, (responsivity, dark current, read noise, and source repeatability) were checked as a function of bias. A total of five bias settings were tested for each array. The results are presented below.

Analysis

The following steps were followed in analyzing the data:
1) V2.31 of mips_sloper was used to reduce the data. We used flags -l -j CamG
for the stim-calibrated dark data and -l -q -j CamG for the read noise
data. The 160um read noise data also included a -y flag, to output the
data in 2x28 rather than 3x20 format. The stim-calibrated darks were
also run through mips_sloper with the flags -d -C CamG.
2) We used get_rdnoise_new.pro on the
70um data to calculate read noise and dark current. We set n_dce_rej=10.
We also used the bad70 flag that Karl G added to the get_rdnoise program
to exclude the B-side of the array and readout 4,4 on the A-side. The
get_rdnoise routine does not handle the 160um data properly yet, so
improvements will be needed. For now, the measured read noise values
are about 6000 e at 15mV bias and a factor of 10 worse at 30mV bias.
These numbers are tremendously higher than what was seen on the ground.
3) The stim-calibrated dark data were run through the IDL program
mips246_stimcal.pro with flag
'skip=10' to determine the mean stim brightness and the stim repeatability. This program determines the array mean for each of the stim flashes,
ignoring the first 'skip' flashes, and then determines the mean of
these mean brightnesses. It also takes the brightness of each
odd-numbered flash, divides that number by the average of the adjacent
even-numbered flashes, and then calculates the standard deviation of
these normalized values. This is not the best way of assessing stim
repeatability, but it does provide a crude first estimate. It is
a quantitative representation of the array-average brightness plots
presented by John S below.
4) Karl Misselt performed a stim repeatability assessment, using the
same methodology used in his earlier report on 70um stim repeatability.
Details and plots will follow in a later version of this writeup.
5) The stim-calibrated dark data were run through the IDL program
mips246_darkcal.pro. This
program determines the array mean for each of the dark DCEs, then
calculates the mean and standard deviation of these array means.
It is possible to set the number of DCEs to ignore after each stim
flash, to minimize the effect of stim latents. In practice, since
the cosmic ray filtering is not perfect, I used the skip parameter
as best I could to clean out the effect of bad DCEs. A median
filter would have been more effective and will be implemented later,
when there is more time to reanalyze the data. I will also try
using the -q flag in mips_sloper, for 3sigma rather than 5sigma
cosmic ray filtering. For now, the dark levels from the read noise
data are probably a more accurate assessment of dark levels, even
though they are not stim-calibrated. I record the time since the
last thermal anneal in the tables below so that an eyeball correction
can be made for the effect of cosmic rays. This post-anneal time
is also useful in looking at Karl's stim repeatability results.
6) These results can be combined with insights into the effects of bias
voltage on the dynamic range of the detector, the linearity of the
data ramps, and the behavior of the B-side of the 70um array in
deciding how best to set the detector bias.

Results

For each bias voltage, we measured a set of 50 10s dark DCEs. The IDL program get_rdnoise_new provided measurements of the dark current and read noise for each of these biases. The results are as follows:

AORID 70Bias 160Bias 70ReadNoise 70DarkCurrent 160ReadNoise 160DarkCurrent
         (mV)   (mV)      (e)         (e/s)         (e)          (e/s)
7152640   30    15   385 +/- 156  583 +/- 208       TBD           TBD
7155200   30    20   381 +/- 132  617 +/- 233       TBD           TBD
7152896   35    20
7155456   35    25   644 +/- 217  472 +/- 163       TBD           TBD
7153152   40    25   531 +/- 202  718 +/- 270       TBD           TBD
7153408   40    30   538 +/- 183  697 +/- 257       TBD           TBD
7155712   40    35   721 +/- 266  654 +/- 228       TBD           TBD
7152384   45    35   783 +/- 293  615 +/- 210       TBD           TBD
7155968   45    15   829 +/- 340  773 +/- 261       TBD           TBD
7154688   50    15   871 +/- 351  773 +/- 268       TBD           TBD

For each bias voltage, we measured 278 DCEs with a stim flash on the 2nd DCE and every 6 DCEs after that, for a total of 47 stim flashes. The IDL routines mips246_stimcal and mips246_darkcal and Karl Misselt's stim repeatability routine provided the following results:

70um Analysis:
AORID 70Bias 160Bias   Mean Stim      Stim   K.Misselt     Dark     Time Since
         (mV)   (mV)   (DN/s)        StdDev  StimRep(%)   (DN/s)    70um Anneal
                                            2stim 4stim                 (h)
7152640   30    15    9106 +/- 296   .0138   8.7   8.8  105 +/- 18       0
7155200   30    20    8872 +/-  78   .00863  7.0   7.0   86 +/- 20       1
7152896   35    20                                                       0
7155456   35    25   10477 +/- 178   .0103   7.4   7.3  103 +/- 37       1
7153152   40    25   11404 +/- 388   .00811  9.8   9.5   78 +/-158       0
7153408   40    30   11664 +/- 161   .0122   9.6   9.4  109 +/- 31       0
7155712   40    35   13102 +/- 305   .00767  6.9   6.7  140 +/- 66       1
7152384   45    35   13022 +/- 302   .0116   9.7   9.3  122 +/- 91       0
7155968   45    15   15366 +/- 408   .00770  6.6   6.2  154 +/- 21       1
7154688   50    15   14727 +/- 684   .0130   9.4   9.0  140 +/- 81       0

John Stansberry has produced plots of brightness vs DCE number for the stim-calibrated dark data. This includes array averages and is very useful for assessing stim repeatability and responsivity drifts. For the 160um data, the repeatability is good for 15mV and 20mV bias and becomes terrible starting at 25mV bias (in great part due to heavy saturation at this and higher biases). For the 70um array, there is no obvious trends in repeatability with bias voltage. These plots are presented below:

160um_15mV.jpg 160um_20mV.jpg 160um_25mV.jpg 70um_30mV.jpg 70um_35mV.jpg 70um_45mV.jpg 70um_50mV.jpg

Conclusions

It is pretty clear that we want to reduce the 160um bias to either 15 or 20mV, with 15mV being slightly favored. The main criteria in this assessment are the ramp shapes and the stim repeatability. From John S's plots, the repeatability looks to be slightly better at 15mV, and we think that we can make it better by increasing the stim brightness by about 30%. We will have Karl M perform his stim repeatability analysis on the 15mV and 20mV stim data to make this more definitive. For the 70um array, the responsivity and noise both grow roughly linearly with bias. This is a bit surprising since ground tests showed that responsivity grows with the square of the detector bias, as expected by detector physics. The stim repeatability is noticeably better an hour after an anneal than it is immediately following an anneal, but there is no obvious dependence on bias voltage. The plan for campaign J is to update the mips-irs patch block to use a 160um bias voltage of 15mV and a 70um bias voltage of 55mV. We will explore 70um bias voltages from 55-70 mV in that campaign, in addition to a number of noise-mitigating strategies for the B-side of the 70um array.

Output and Deliverable Products

None

Actions Following Analysis

None