Page History

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Contents:
17 Feb 2011 - ACIS peaks and sigmas
24 Mar 2011 - ACIS line fluxes
04 May 2011 - XIS peaks versus COR
04 May 2011 - IACHEC plots: ACIS & XIS peaks, FWHMs & line fluxes
21 Jun 2011 - Is line centroid a good proxy for CTI?
17 Oct 2011 - Figures for paper?
31 Oct 2011 - Trailing charge
31 Oct 2011 - Figures for paper
21 Nov 2011 - OLD Schematic figures for paper
02 Dec 2011 - CTI change at -120C and -90C on ACIS
06 20 Dec 2011 - Schematic figures for paper
Anchoranchor1anchor117 Feb 2011 - Catherine's attempt to duplicate Bev's monthly XIS plots for ACIS I3 (FI) and S3 (BI). Each data point is a fit to 0.1 years worth of cold ACIS calibration source data, filtered to include only the upper corner regions like XIS and grades G02346. After some testing as to which fitting procedures were less sensitive to background variations (important for ACIS probably not as much for XIS), and robust against low signal-to-noise data, I chose to use a Gaussian plus a linear background component (mpfitfun.pro with some limits to prevent non-physical fits).

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02 Feb 2012 - XIS Perseus analysis for non-CTI changes
09 Feb 2012 - XIS Perseus analysis for non-CTI changes, part II
05 Sep 2012 - ACIS fits with Gehrels weighting
05 Sep 2012 - cal source plots
14 Sep 2012 - XIS fits with Gehrels weighting
14 Sep 2012 - XIS background trend from night Earth data
24 Sep 2012 - new cal source plots
25 Sep 2012 - perseus intercepts
31 Oct 2012 - XIS BG trend from night Earth data, updated
31 Oct 2012 - XIS + ACIS background spectra with lines ID'd
17 Jan 2014 - XIS + ACIS calibration source spectra overplotted
17 Jan 2014 - XIS + ACIS background spectra with lines ID'd, version 2
13 Mar 2014 - new cal source plots

SPENVIS work has its own page: spenvis

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17 Feb 2011 - Catherine's attempt to duplicate Bev's monthly XIS plots for ACIS I3 (FI) and S3 (BI). Each data point is a fit to 0.1 years worth of cold ACIS calibration source data, filtered to include only the upper corner regions like XIS and grades G02346. After some testing as to which fitting procedures were less sensitive to background variations (important for ACIS probably not as much for XIS), and robust against low signal-to-noise data, I chose to use a Gaussian plus a linear background component (mpfitfun.pro with some limits to prevent non-physical fits).

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24 Mar 2011 - CEG - The line normalizations that come out of the above fits. The first is a linear plot of the normalization versus time showing the obvious signature of radioactive decay. (Edit added later: line normalizations is bad terminology. What I mean is the counts under the peak (Gaussian norm * Gaussian sigma * 2.51) divided by the exposure time)

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Then comparing the data to the expected half-life of 2.737 years for Fe-55. There is clearly a slow reduction in quantum efficiency of 5-10% over the entire 11 years.

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To confirm the source of the quantum efficiency reduction, here is the same plot, but for fits from the data in the lower corners of the CCD - closest to the framestore. There is no reduction in quantum efficiency for these data, indicating that the drop is due to increased CTI. Increased CTI leads to more charge trailing and more events morphing from acceptible to bad grades. CTI correction (the default in standard processing but not used here), would remove most of the QE drop.

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May 4, 2011 - Bev

XIS peak location vs Cut Off Rigidity for recent times (201101).
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while the last points of xis3 (FI) seem a bit odd, but neither the FI nor the BI are well fit with a line. The peak locations are not a function of the background variations.

Here are plots of the xis1 (BI) high

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Then comparing the data to the expected half-life of 2.737 years for Fe-55. There is clearly a slow reduction in quantum efficiency of 5-10% over the entire 11 years.

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To confirm the source of the quantum efficiency reduction, here is the same plot, but for fits from the data in the lower corners of the CCD - closest to the framestore. There is no reduction in quantum efficiency for these data, indicating that the drop is due to increased CTI. Increased CTI leads to more charge trailing and more events morphing from acceptible to bad grades. CTI correction (the default in standard processing but not used here), would remove most of the QE drop.

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XIS peak location vs Cut Off Rigidity for recent times (201101).
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while the last points of xis3 (FI) seem a bit odd, but neither the FI nor the BI are well fit with a line. The peak locations are not a function of the background variations.

Here are plots of the xis1 (BI) high energy count rate vs cut off rigidity to compare to the ACIS s3 (BI) high energy reject rates used to track the background levels for ACIS.

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ACIS has a known slow change in the gain as a function of time as measured very close to the framestore where CTI should be negligible. For all of the CCDs except I0 and I2 it is monotonically decreasing at a rate of ~1 ADU/yr at 5.9 keV. (The gain change on I0 and I2 is pathological with jumps and annual trends that aren't relevant, so I don't use them here.) See http://space.mit.edu.ezproxyberklee.flo.org/~cgrant/gain^{Image Removed} and http://space.mit.edu.ezproxyberklee.flo.org/~cgrant/line^{Image Removed} for example plots.

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ACIS trailing charge plots, to be compared to the XIS equivalent here (http://space.mit.edu.ezproxyberklee.flo.org/XIS/monitor/ccdperf/^{Image Removed})

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Oct 31, 2011 - Catherine

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At my review, Mark and I talked about the problem of separating the different radiation environment from the different focal plane temperatures. I remembered that we had taken data with ACIS at -90C at two different times, in Sept 1999 and Aug 2005, so we can at least see how different the CTI evolution is on ACIS at both temperatures.

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ACIS peak vs temperature for S2 and S3

The top panel is for ACIS-S2, the bottom for ACIS-S3. (There's isn't any data for I3 in 1999, so I've switch so S2 which is also an FI device but has higher CTI.) The data points are showing the centroid pulseheight as a function of focal plane temperature (measured in the same regions and the same way as everything above.) The later data has lower pulseheights which is consistent with the CTI increase. For both devices the size of the increase is larger at -90C than it is at -120C.

More specifically...

S3 at -119C, the peak drops by 0.8%
S3 at -90C, the peak drops by 2.1%
S2 at -119C, the peak drops by 2.0%
S2 at -90C, the peak drops by 9.9%

For S3, the drop is 2.7 times faster at -90C than at -120C. For S2, the drop is 5.1 times faster at -90C than at -120C. To compare to XIS, the FI CCDs on XIS drop 5 times faster than ACIS, the BI CCDs drop 9 times faster than ACIS. (The XIS numbers are with charge injection on, but before the BI charge injection was increased.) So the difference in CTI evolution between ACIS and XIS may be entirely due to the focal plane temperature?

(The FWHM of ACIS-S2 at -90C is so large that the Mn-K line is hopelessly entangled with the Mn-Kbeta and Ti-K lines, so I haven't extended this analysis to FWHM.)

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Schematic figures for paper (v2)

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ACIS schematic PS

so we can at least see how different the CTI evolution is on ACIS at both temperatures.

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ACIS peak vs temperature for S2 and S3

The top panel is for ACIS-S2, the bottom for ACIS-S3. (There's isn't any data for I3 in 1999, so I've switch so S2 which is also an FI device but has higher CTI.) The data points are showing the centroid pulseheight as a function of focal plane temperature (measured in the same regions and the same way as everything above.) The later data has lower pulseheights which is consistent with the CTI increase. For both devices the size of the increase is larger at -90C than it is at -120C.

More specifically...

S3 at -119C, the peak drops by 0.8%
S3 at -90C, the peak drops by 2.1%
S2 at -119C, the peak drops by 2.0%
S2 at -90C, the peak drops by 9.9%

For S3, the drop is 2.7 times faster at -90C than at -120C. For S2, the drop is 5.1 times faster at -90C than at -120C. To compare to XIS, the FI CCDs on XIS drop 5 times faster than ACIS, the BI CCDs drop 9 times faster than ACIS. (The XIS numbers are with charge injection on, but before the BI charge injection was increased.) So the difference in CTI evolution between ACIS and XIS may be entirely due to the focal plane temperature?

(The FWHM of ACIS-S2 at -90C is so large that the Mn-K line is hopelessly entangled with the Mn-Kbeta and Ti-K lines, so I haven't extended this analysis to FWHM.)

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Dec 20, 2011 - Eric (updated from Dec 06, 2011)

Schematic figures for paper (v3)

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ACIS schematic PS

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XIS schematic PS

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Feb 02, 2012 - Eric

Analysis of XIS3 Perseus data from 0<ACTY<128, to see how well we might constrain non-CTI gain changes. Line centroid is fit to 0.1%, might have issues from differing kT. These data have been gain- and CTI-corrected, so this is just a proof of concept.

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XIS3 Perseus spectrum PDF

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Perseus model spectra with kT = 4 keV and 7 keV

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Feb 09, 2012 - Eric

Analysis of XIS1,3 Perseus data, re-PHA'd and re-graded by Bev. GRADE_BEV=0,2,3,4,6 were used along with PHA_BEV, which have no CTI or gain correction. A powerlaw+Gaussian was fit to the Fe XXV K line complex and best-fit center is plotted for segments 1 and 2 (=B and C), and 128-row bins at the bottom, middle, and top of the CCD.

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XIS1 Perseus line center trend PDF
XIS1 Perseus fit spectra PDF

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XIS3 Perseus line center trend PDF
XIS3 Perseus fit spectra PDF

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Sep 05, 2012 - Catherine

Figures 6 and 9 (ACIS peaks and FWHMs vs time) using Gehrels weighting in the fitting and showing the error bars. In general, the errors bars are very small. Gehrels weighting doesn't change the results much.

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Sep 05, 2012 - Bev

calibration source plots. I fit the peak in adu for each quad separately, then re-processed using the main fe55 peak as the gain, then plotted quads A&D combined. I normalized by dividing by the total number of counts in the spectrum from 0 to 10 keV but only plotted 1 to 10. g02346 events only.

both side by side
both stacked
acis only
xis only

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Sep 14, 2012 - Catherine

Figures 5 (xis peaks vs time), 8 (xis fwhm vs time), 12 (xis peak vs cor) and 13 (xis fwhm vs for) using Gehrels weighting in the fits and showing the error bars. The Gehrels results are similar to what's in the paper except for fwhm vs time which increasing more slowly in the Gehrels fits.

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Sep 14, 2012 - Eric

Trend of the XIS NXB from night Earth data, extracting a 512x512 box from the chip center, using only COR2>6 data with normal SCI on (XIS1 at 2 keV level). XIS1 has a clear downward slope of -0.003 cts/s/yr +/- 20%, or about 3% per year. XIS0,3 are consistent with no change. Perhaps this is actually a gain issue with XIS1.

Look at the PDF also.

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Update post-meeting: Now including all COR2, 5-15 keV (to reduce gain effects around 7 keV). XIS1 still changes by 4% +/- 1% per year, though with lots of scatter. +/-1-sigma limits for FIs: +0%/-1% (XIS0), +0.5%/-0.5% (XIS3).

Look at the PDF also.

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XIS NXB spectra from Tawa et al 2008 (Fig 1):

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Sep 24, 2012 - Bev

New version of cal source plots.

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eps version for .tex.

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Sep 25, 2012 - Bev

I took the intercept of peak vs row for the main iron line in the perseus data
and fit it versus time. The summary is that the intercept is dropping less than half a percent per year for the higher CI levels and less than 1 percent per year for the original, lower, BI level.

CCD	quad	CI		adu/year	error (edu/year)
XIS1	c0	higher CI	3 SRs	-5.39	21.81
XIS1	c0	original CI	12 SRs	-15.24	1.56
XIS1	c1	higher CI	3 SRs	1.63	3.59
XIS1	c1	original CI	12 SRs	-8.94	0.47
XIS1	c2	higher CI	3 SRs	-2.42	4.03
XIS1	c2	original CI	12 SRs	-11.25	0.48
XIS1	c3	higher CI	3 SRs	6.52	10.35
XIS1	c3	original CI	12 SRs	-11.54	1.59
XIS3	c0	FI CI	13 SRs	-5.41	0.95
XIS3	c1	FI CI	13 SRs	-3.66	0.32
XIS3	c2	FI CI	13 SRs	-3.54	0.26
XIS3	c3	FI CI	12 SRs	-5.07	0.82

ps of plots. individual eps files available on request.

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Oct 31, 2012 - Eric

Trend of the XIS NXB from night Earth data, extracting all but the cal source regions and bad regions of each chip, using all COR2 data with normal SCI on (XIS1 at 2 keV level). See previous post.

Here it is in 4 week bins, with the XIS1 y errorbars corresponding to the counting statistics. First using FTOOL lcurve:

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Second doing this by hand in xselect by and-ing a 4 week time range with the GTIs:

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I don't understand the scatter; each bin contains about 50 ksec of data, 1000's of counts, and should span a similar distribution of COR2, yet there is an intrinsic ~ 25% scatter, far higher than the < 5% quoted by Tawa. Restricting COR2>=10 does not change this, nor do larger time bins. Perhaps something is wrong with the GTIs and thus the effective exposure time calculation.

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