diff --git a/body.tex b/body.tex index 478ca24..78e11b8 100644 --- a/body.tex +++ b/body.tex @@ -383,6 +383,7 @@ \subsubsection{Charge transfer \end{centering} \end{figure} +\clearpage \paragraph{Parallel CTI}\label{parallel-cti} The CTI along the parallel direction is consistent between Run 6 and @@ -408,6 +409,7 @@ \subsubsection{Charge transfer \end{centering} \end{figure} +\clearpage \subsection{Dark metrics}\label{dark-metrics} \subsubsection{Dark current}\label{dark-current} @@ -435,6 +437,7 @@ \subsubsection{Dark current}\label{dark-current} Unexpectedly, the dark current was significantly less in Run 7 than Run 6 (Fig.~\ref{fig:dark}). We do not attach particular significance to the finding because this could be the result of improved shrouding on the camera in the Level 3 white room relative to the IR2 clean room SLAC. +\clearpage \subsubsection{Bright defects}\label{bright-defects} Bright defects are localized regions or individual pixels that produce abnormally high signal levels, even in the absence of light. These defects are typically caused by imperfections in the semiconductor material or manufacturing process of the CCD. Bright defects can manifest as ``hot pixels" with consistently high dark current, small clusters of pixels with elevated dark current, or as ``hot columns" (pixels along the same column that have high dark current). @@ -461,6 +464,7 @@ \subsubsection{Bright defects}\label{bright-defects} \end{centering} \end{figure} +\clearpage \subsection{Flat pair metrics}\label{flat-pair-metrics} \begin{figure}[ht] @@ -470,6 +474,7 @@ \subsection{Flat pair metrics}\label{flat-pair-metrics} \end{centering} \end{figure} +\clearpage \subsubsection{Linearity and PTC turnoff}\label{linearity-and-ptc-turnoff} Linearity turnoff and PTC turnoff are two closely related metrics used @@ -507,6 +512,7 @@ \subsubsection{Linearity and PTC turnoff}\label{linearity-and-ptc-turnoff} \end{centering} \end{figure} +\clearpage \subsubsection{PTC Gain}\label{ptc-gain} PTC gain is the conversion factor between digital output signal and the the number of electrons generated in the pixels of the CCD. It is one of the key parameters derived from the Photon Transfer @@ -522,6 +528,7 @@ \subsubsection{PTC Gain}\label{ptc-gain} PTC gain measurements agree extremely closely across all sensors in the focal plane. +\clearpage \subsubsection{Brighter fatter coefficients}\label{brighter-fatter-a00-coefficient} @@ -556,6 +563,7 @@ \subsubsection{Brighter fatter coefficients}\label{brighter-fatter-a00-coefficie However, the differences in the brighter-fatter $a_{00}$ coefficient between Run 6 and Run 7 show that the magnitude of $a_{00}$ decreased for most of the outliers, which implies an improvement in imaging for those pixels. +\clearpage \subsubsection{Row-means variance}\label{row-means-var} Row-means variance is a metric that measures the mean row-to-row variance of differences between a pair of flats. By computing variance of means of differenced rows at each flux level, we can measure any changes in gain row-by-row and also changes in correlated noise along with row. @@ -576,6 +584,7 @@ \subsubsection{Row-means variance}\label{row-means-var} \end{centering} \end{figure} +\clearpage \subsubsection{Divisadero Tearing} Divisadero tearing (or Rabbit ears) is manifested as signal variations near amplifier boundaries, connected features that are often jagged \cite{2020arXiv200209439J,2024SPIE13103E..0WU}. These variations are on the order of \textasciitilde1\% relative to the flat field signal. To quantify divisadero tearing in a given column, we measure the column signal, and compare it to the mean column signal from flat fields. @@ -596,6 +605,7 @@ \subsubsection{Divisadero Tearing} \label{fig:divisidero_diff_baseline} \end{figure} +\clearpage \subsubsection{Dark defects}\label{dark-defects} Dark defects are localized regions or individual pixels that produce abnormally low signal levels, even in the presence of light. Similar to bright pixels, dark pixels are also quantified in dark columns over 50 pixel contiguous regions. These @@ -633,6 +643,7 @@ \subsubsection{Dark defects}\label{dark-defects} In both instances, the contamination of dark pixels across the focal plane is \leq 10 pixels per amplifier on average. There is a measurable improvement in the dark pixel counts, decreasing by one pixel per amplifier between Run 6 and Run 7. +\clearpage \subsection{Persistence}\label{initPersistenceChar} Persistence is a feature of CCDs and how they are operated involving charge trapped in the @@ -684,6 +695,7 @@ \subsection{Persistence}\label{initPersistenceChar} \label{fig:persistence-decay-comp} \end{figure} +\clearpage \subsection{Differences between Run 6 and Run 7}\label{differences-from-previous-runs} All camera performance metrics from the summit show close agreement with SLAC IR2 tests. PTC/full-well metrics were consistent, and no significant bright cosmetic defects developed. Dark cosmetic defects are difficult to quantify due to the edge sensor effects, though the consistency in CTI measurements would indicate that dark defects did not change from previous runs. Dark current and Divisadero tearing show improved performance compared to Run 6, while the Persistence feature is still prominent in e2v sensors. @@ -1233,18 +1245,12 @@ \subsection{Summary}\label{summary:optimization} v27 incorporated guider functionalities, including ParallelFlushG and ReadGFrame. However, the noRG change was inadvertently included. Consequently, we abandoned this version and switched to v28. +\item \href{https://rubinobs.atlassian.net/browse/LSSTCAM-5}{v28 sequencer files merged v26noRG and + v27.} +\item\href{https://rubinobs.atlassian.net/browse/LSSTCAM-34}{v29 introduced changes to speed up the guider.} \item - v28 sequencer files merged v26noRG and - v27. \url{https://rubinobs.atlassian.net/browse/LSSTCAM-5} -\item - v29 introduced changes to speed up the guider. - \url{https://rubinobs.atlassian.net/browse/LSSTCAM-34} -\item - v30 primarily focused on e2v. We introduced a new approach to NopSf - for e2v CCDs - \url{https://github.com/lsst-camera-dh/sequencer-files/pull/17}. To - align timing with the ITL version, a change was made. - \url{https://github.com/lsst-camera-dh/sequencer-files/pull/18} + \href{https://github.com/lsst-camera-dh/sequencer-files/pull/17}{v30 primarily focused on e2v}. We introduced a new approach to NopSf + for e2v CCDs. \href{https://github.com/lsst-camera-dh/sequencer-files/pull/18}{T align timing with the ITL version, a change was made.} \end{itemize} We also disabled IDLE\_FLUSH to improve the thermal situation and the Divisadero tearing. @@ -1300,6 +1306,8 @@ \subsubsection{Stability flat metrics}\label{sec:finalstability-flat-metrics} \label{fig:finalChar-SCTI-hist} \end{figure} +\clearpage + \paragraph{Parallel CTI}\label{sec:finalChar-parallel-cti} @@ -1321,6 +1329,8 @@ \subsubsection{Stability flat metrics}\label{sec:finalstability-flat-metrics} \label{fig:finalChar-PCTI-hist} \end{figure} +\clearpage + \subsubsection{Dark metrics}\label{final-dark-metrics} \paragraph{Dark current}\label{sec:finaldark-current} @@ -1335,6 +1345,7 @@ \subsubsection{Dark metrics}\label{final-dark-metrics} \end{figure} The reduction in dark current in the subset of rafts is indicative of successful light leak mitigation, and lowers the dark current on local rafts to levels similar to the rest of the focal plane. +\clearpage \paragraph{Bright defects}\label{final-bright-defects} @@ -1349,6 +1360,7 @@ \subsubsection{Dark metrics}\label{final-dark-metrics} For additional discussion about defect stability, see Section~\ref{defect-stability}. +\clearpage \subsubsection{Flat pair metrics} \begin{figure}[ht] @@ -1357,6 +1369,7 @@ \subsubsection{Flat pair metrics} \caption{Comparison of PTCs from initial and final Run 7 conditions, evaluated on a central detector and amplifier.} \label{fig:finalChar-PTCComparison} \end{figure} +\clearpage \paragraph{Linearity and PTC turnoff}\label{final-linearity-and-ptc-turnoff} @@ -1389,6 +1402,7 @@ \subsubsection{Flat pair metrics} \end{figure} +\clearpage \paragraph{PTC Gain}\label{final-ptc-gain} PTC Gain was extracted from the PTC runs. PTC gain is extremely comparable between initial and final Run 7 conditions, with a minor increase in gain observed in e2v sensors. @@ -1409,6 +1423,7 @@ \subsubsection{Flat pair metrics} \label{fig:finalChar-PTCGain_HistComp} \end{figure} +\clearpage \paragraph{Brighter fatter $a_{00}$ coefficient}\label{final-brighter-fatter-a00-coefficient} The relative strength of the brighter-fatter effect, quantified by $a_{00}$ following the model from \cite{2019A&A...629A..36A}, is modified in the final Run 7 operating conditions by the lower parallel swing for e2v sensors. We observe an extremely high consistency for ITL sensors. @@ -1429,6 +1444,7 @@ \subsubsection{Flat pair metrics} \label{fig:finalChar-PTC_A00_E2VComp} \end{figure} +\clearpage \paragraph{Brighter-Fatter Correlation}\label{final-brighter-fatter-correlation} The strength of the brighter fatter correlation was extracted from the PTC runs. In both instances, the correlation is extremely consistent across initial and final Run 7 operating conditions. @@ -1450,6 +1466,7 @@ \subsubsection{Flat pair metrics} \end{figure} +\clearpage \paragraph{Row-means variance}\label{final-row-means-var} Row means variance is extracted from the PTC runs, and shows an extremely tight correlation when comparing the initial and final operating conditions of Run 7. ITL sensors show an extremely tight agreement, while e2v sensors show a lower row-means variance by \textasciitilde1.8\% in the final operating conditions. @@ -1461,6 +1478,7 @@ \subsubsection{Flat pair metrics} \label{fig:finalChar-RowMeanVarSlope-5x5} \end{figure} +\clearpage \paragraph{Divisadero Tearing}\label{final-divisadero-tearing} Divisadero tearing measurements were extracted from the B protocols, and are significantly different for e2v sensors in the final operating condition. The change in Divisadero strength is driven by idle flush, which is described in detail in Section~\ref{section:disablingIDLEFLUSH}. The e2v sensors show a 60.7\% decrease in the original Divisadero signal under the final operating conditions. ITL sensors show a 0.2\% increase in the original Divisadero signal under the final operating conditions. @@ -1474,6 +1492,7 @@ \subsubsection{Flat pair metrics} In Figure \ref{fig:finalChar-Divisadero-5x5}, several e2v sensors do not follow the global trend of decreased Divisadero signal. +\clearpage \paragraph{Dark defects}\label{final-dark-defects} Dark defects in LSSTCam were extracted using the B protocols, and are contaminated by the picture frame effect regardless of operating conditions (see Sec.~\ref{dark-defects} for additional discussion). When applying a 9 pixel mask to the edges of each sensor, the picture frame signal is removed, leaving true dark defects acquired by the analysis pipeline. @@ -1495,6 +1514,7 @@ \subsubsection{Flat pair metrics} \label{fig:finalChar:darkDefectsComparison} \end{figure} +\clearpage \subsubsection{Persistence}\label{final-persistence} The primary optimization target of Run 7 was to mitigate persistence, described in Section~\ref{persistence-optimization-1}. The major change in the final camera operating conditions to combat persistence is decreased parallel swing. This change is applied to the e2v sensors only, as they are the subset of sensors that exhibit \geq 1 ADU persistence when using the Run 7 initial operating parameters.