\begin{quotation} {\it Objective:} Derive the HETGS(HRC-I) effective area and compare it to HRMA, HETG, and HRC-I measurements and predictions. HRC-I effects that must be understood include: quantum efficiency, quantum efficiency, and quantum efficiency. {\it Publication(s):} Flanagan {\it et al.}\cite{flanagan98} \end{quotation} \subsection{HETG/HRC-I Tests at XRCF} HETG was tested in combination with the HRC-I in Phase 2 at XRCF. The complete series consisted of one focus check at 1.254 keV, 33 effective area tests in a defocussed configuration, and one monochromator scan with 4 energies centered on 1.54 keV. These are listed in Table~\ref{tbl:hrc_tests}, along with the energy and range of dispersed orders on the detector. Figure~\ref{fig:hrc_image} shows the HRC-I with the HEG and MEG grating dispersion pattern at 7~keV. The HRC-I detector is square and the image of Figure~1 is presented in detector coordinates. The dispersion direction for the gratings is aligned approximately parallel to a diagonal of the detector, so that the number of orders detected is limited by the detector size and the intensity of the high orders. In general, the zero order position was displaced from the nominal imaging aim point in order to minimize accumulated dose in that region. Note that the direction of the bias angle of the microchannel plate is toward the top in the figure, and is not symmetric with respect to the dispersion direction. Details of the HRC-I and calibration information are given in this and prior conferences\cite{kenter96,kenter97,murray97}. From Table~\ref{tbl:hrc_tests} it is evident that HEG 2nd order is only available on the detector for energies of 1.7~keV and above. For the MEG gratings, 2nd order was suppressed and measurable at only a few energies, but third order was detectable at 1.49~keV and above. Energies below 1.254~keV were not analyzed for either grating since there were no higher orders falling on the detector. The breakdown of order by energy is given in Table~\ref{tbl:hrc_orders}. \begin{table}[h]\centering \begin{tabular}{|c|c|c|c|c|c|} \hline\hline Run ID & TRW ID & Energy & HEG orders & MEG Orders & Comments \\ \hline\hline i0810621 & G-HHI-EA-7.048 & 7.0 & +6 to-6 & +3 to -5 & \\ \hline i0811327 & G-HHI-EA-99.059 & 7.0 & +4 to -4 & +3 to -5 & \\ \hline i0810657 & G-HHI-EA-7.047 & 6.3 & +6 to -5 & +8 to -5 \\ \hline i0811342 & G-HHI-EA-99.060 & 6.3 & +4 to -4 & +8 to -3 & \\ \hline i0810725 & G-HHI-EA-7.046 & 5.76 & +5 to -5 & +8 to -5 & \\ \hline i0811356 & G-HHI-EA-99.061 & 5.76 & +4 to -4 & +5 to -5 & \\ \hline i0810804 & G-HHI-EA-7.045-1 & 5.66 & +5 to -5 & +8 to -9 & \\ \hline i0810756 & G-HHI-EA-7.045 & 5.66 & +5 to -5 & +5 to -7 & \\ \hline i0810831 & G-HHI-EA-7.044 & 5.48 & +5 to -4 & +7 to -5 & \\ \hline i0810855 & G-HHI-EA-7.043 & 5.32 & +5 to -4 & +7 to -8 & \\ \hline i0810916 & G-HHI-EA-7.042 & 5.25 & +5 to -4 & +8 to -7 & \\ \hline i0810936 & G-HHI-EA-7.041 & 5.13 & +4 to -4 & +5 to -5 & \\ \hline i0810950 & G-HHI-EA-7.040 & 5.05999 & +4 to -4 & +6 to -5 & \\ \hline i0811005 & G-HHI-EA-7.039 & 4.96 & +4 to -4 & +5 to -7 & \\ \hline i0811019 & G-HHI-EA-7.038 & 4.9 & +4 to -4 & +7 to -8 & \\ \hline i0811037 & G-HHI-EA-7.037 & 4.8 & +4 to -4 & +7 to -5 & \\ \hline i0811054 & G-HHI-EA-7.036 & 4.59999 & +4 to -4 & +7 to -5 & \\ \hline i0811114 & G-HHI-EA-7.035 & 4.51 & +4 to -4 & +7 to -5 & \\ \hline i0811132 & G-HHI-EA-7.034 & 4.0 & +4 to -4 & +7 to -7 & \\ \hline i0811155 & G-HHI-EA-7.033 & 3.5 & +3 to -3 & +7 to -6 & MEG 2 overlaps HEG 1. Not corrected. \\ \hline i0811238 & G-HHI-EA-7.032 & 2.29& +2 to -2 & +4 to -4 & \\ \hline i0811414 & G-HHI-EA-7.031 & 1.95 & +2 to -1 & +4 to -4 & \\ \hline i0811434 & G-HHI-EA-7.030 & 1.7 & +2 to -1 & +3 to -3 & \\ \hline i0940311 & G-HHI-EA-9.018 & 1.48693 & & +3 to -3 & MEG only. Has contaminant line.. \\ \hline i0911019 & G-HHI-EA-6.002 & 1.254 & & +2 to -2 & MEG only. EIPS - broad line. \\ \hline i0911034 & G-HHI-EA-6.003 & 1.254 & +1 to -1 & & HEG only. EIPS - broad line. \\ \hline i0910739 & G-HHI-FC-1.003-Q1 & 1.254 & +1 to -1 & +2 to -2 & \\ \hline i0910817 & G-HHI-FC-1.003-Q2 & 1.254 & +1 to -1 & +2 to -2 & \\ \hline i0910854 & G-HHI-FC-1.003-Q3 & 1.254 & +1 to -1 & +2 to -2 & \\ \hline i0910931 & G-HHI-FC-1.003-Q4 & 1.254 & +1 to -1 & +2 to -2 & \\ \hline i0940337 & G-HHI-9.019 & 1.17595 & & +1 to -1 & MEG only. W contaminant line. \\ \hline i0811452 & G-HHI-10.003 & 1.54 & +1 to -1 & +3 to -2 & Energy scan; analysis complete. \\ \hline i0940357 & G-HHI-9.020 & 0.95996 & & & Not analyzed \\ \hline i0902304 & G-HHI-6.004 & 0.9297 & & & Not analyzed. MEG only. \\ \hline i0902318 & G-HHI-6.006 & 0.9297 & & & Not analyzed. HEG only. \\ \hline i0940427 & G-HHI-9.021 & 0.75996 & & & Not analyzed \\ \hline i0901229 & G-HHI-6.005 & 0.705 & & & Not analyzed \\ \hline i0940505 & G-HHI-9.022 & 0.70499 & & & Not analyzed \\ \hline i0900251 & G-HHI-6.001 & 0.5249 & & & Not analyzed. MEG only. \\ \hline i0900336 & G-HHI-6.001-b & 0.5249 & & & Not analyzed. MEG only. Contains O. \\ \hline\hline \end{tabular} \caption{\small \label{tbl:hrc_tests} Summary of HETG + HRC-I higher order data. } \end{table} \begin{table}[h]\centering \begin{tabular}{|c|c|c|c|} \hline\hline Order & HEG Energy range & MEG Energy range & Comments \\ \hline\hline 2 & 1.7 to 7.0 & 1.254, 1.7, 1.95, 2.29 & not sufficiently detectable at other energies\\ \hline 3 & 3.5 to 7.0 & 1.48693 to 7.0 & \\ \hline 4 & 4.0 to 7.0 & 1.95 to 6.3 & not sufficiently detectable at 7.0\\ \hline 5 & 5.25 to 7.0 & 3.5 to 7.0 & \\ \hline 6 & 6.3 and 7.0 only & 3.5 to 6.3 except 5.13 & \\ \hline 7 & & 3.5 to 5.76 except 5.05999, 5.13 & \\ \hline 8 & & 4.9, 5.25, 5.32, 5.66, 5.76, 6.3 & \\ \hline 9 & & 5.66 only & \\ \hline\hline \end{tabular} \caption{\small \label{tbl:hrc_orders} Energy ranges of the measured HETG + HRC-I higher orders.} \end{table} \begin{figure}[t] \vspace{0.8true in} \special{psfile=hrcdata.ps hoffset = 0 voffset = -350 hscale =70 vscale =70 angle = 0} \vspace{3.5true in} \hspace*{0 true in}\vbox { \hsize 6.0 true in \caption{\small \label{fig:hrc_image} HETG + HRC-I test at 7~keV. Positive orders are dispersed toward the upper left in the figure. The large box, top right, is used to estimate detector background. The small boxes around zero order sample mirror-scattered events. The data have been ``cleaned'' to remove saturated events.}} \vspace{0.8true in} \end{figure} \subsection{Processing the Raw HRC-I Data} The HRC data were processed in several steps. The raw data files were screened for lost major frames, converted from telemetry format and degapped. Two sets of event lists were then created, with different rejection criteria based on the saturation levels of the electronics (4096 for the amplifiers and 255 for the pulse height). This approach was prompted by considering the testing conditions early in Phase 2. In the first day of the HETG + HRC-I tests, the detector high voltage was set at a relatively high level and there was a considerably higher fraction of saturated events. This unusual saturation level\cite{murray97} was decreased on subsequent days (the high voltage was lowered) and has been eliminated in the flight instrument. Since readout saturation can also result in incorrect position assignment of the events (of order 1/2~mm or less), two separate analyses were performed on the data. In the case of ``cleaned'' data, all events with pulse height above 254 or with amplifier value above 4090 were rejected. In the second case, saturated events were included in the analysis (for which the data were termed ``uncleaned''). There is evidence to suggest a higher proportion of saturated events in bright orders relative to faint orders. (This is currently under study.) The data were processed with several steps. Assuming a compressed raw data file, file.rd.gz: \begin{verbatim} gunzip -c file.rd.gz | tm2ftm | nftm2prd -S/dev/null | nprd2epr -u1.0517 -v1. 0363 | nepr\_sel -a4090 -P254 > file.nepr \end{verbatim} \begin{itemize} \item{gunzip: uncompress the raw data file} \item{tm2ftm: screen out lost major frames} \item{nftm2prd: decom step} \item{ --S/dev/null: don't look at rate data} \item{nprd2epr: degap and make event list (where 1.0517 and 1.0363 are the u,v degap parameters)} \item{nepr\_sel --a4090 --P254 : set amplifier saturation value 4090, set upper PHA value 255.} \item{file.nepr: event list file} \end{itemize} \subsection{Selection of Source and Background Regions} The technique employed for selecting regions of the grating readout was to display each dataset with SAOtng\cite{saotng}. Each order of interest was captured in a simple rectangular box region, and the number of events within each box was determined. In order to estimate the effects of background and mirror scattering, several ``background'' regions were selected, as illustrated in Figure~\ref{fig:hrc_image}. The largest box, distant from the zero order, is assumed to reflect approximately detector backgound. The next largest box, while distant from the zero order, nevertheless was found to have a higher ($\sim 2$ times) background rate and is assumed to contain mirror-scattered photons. The selection of small boxes centered among zero and 1st order had a much higher ($\sim 8$ times) background rate, which is presumed due to mirror scattering around the zero order. (The c program which counts the events within the box region is /nfs/wiwaxia/h2/kaf/hrc/src/ssm/fits/nepr\_sel\_kaf.c.) In the analysis, the simple detector background was used for background subtraction for all orders. This is appropriate for the distant high orders, but there may be mirror-scattered photons captured within the first order regions. Mirror scattering is on the 1\% level or less, and by using the measured ``scattered rate'', we found that corrections to the ratios systematically increase it by 0.5\% to a few percent, a negligible effect given the counting statistics and other errors. We have neglected this correction. %%\subsection{Alternative Processing and Analysis} %% It is possible to attempt this analysis with the ASC pipeline %%products that are currently available. The event lists include saturated %%events, but if these uncleaned events are acceptable, then IRAF can be %%employed directly. The commands are: %%\begin{itemize} %%\item{ncl} %%\item{xray} %%\item{xplot} %%\item{ximtool ----> choose SAOIMAGE} %%\item{display "pipeline\_file\_evt.qp[block=32]" 1 zscale- zrange- %%z1=0. z2=3. %% ---> this should display whole image. Choose and save a region using SAOIMAGE.} %%\item{fixsaoreg} %%\item{ximages} %%\item{plcreate} %% region descriptor: my\_phy.reg\\ %% reference image file: pipline\_file\_evt.qp\\ %% output mask data file : mine ---> now it creates mine.pl\\ %%\item{pllist mine.pl ---> shows you what your mask looks like} %%\item{xspatial} %%\item{imcnts} %% source image file: pipeline\_file\_evt.qp \\ %% source region descriptor: mine.pl \\ %% bkg image file or cts/pixel: pipeline\_file\_evt.qp --->can use 0.\\ %% bkg region descriptor: bkg.pl (if you created one)\\ %% root name: neg1\_order ---> now it creates neg1\_order\_cnt.tab \\ %%\item{tables} %%\item{ttools} %%\item{tprint neg1\_order\_cnt prpar+ > neg1\_order.ascii ---> for ascii file %%of results} %%\end{itemize} %% In order to filter out the saturated events, tow approaches might be %%taken. First, select the allowed amplifier and pulse height ranges %%within the qpoe file. Alternatively, work with the pipeline product %%pipline\_file\_evt.fits %%and FTOOLS to do the filtering. Finally, convert the saved fits file to %%a qp file with fits2qp, and procedd as described above. \subsection{Corrections and Errors} Flat field tests to measure detector spatial uniformity were not performed with the settings used on the day on which most of the HETG + HRC data were taken. However, the HRC-I was known to be {\it more} uniform than on subsequent days, for which uniformity data are available\cite{murray97} at 4.5~keV and 1.49~keV. At 4.5~keV, the HRC-I was found to be uniform to better than 5\% over the central region. At 1.49~keV, the detector QE was not as uniform as at the higher energy, but was flat at the 10\% level over the central region\cite{murray97} out to a radius of 30 to 35~mm. Beyond this radius the QE dropped by $\sim 20$\%. No detector uniformity corrections have been applied to the measured ratios. It has been noted that the bias angle is not symmetric with respect to the dispersion direction. This can result in an asymmetric detection efficiency of a positive order with respect to its negative counterpart. The angle dependence of the QE is estimated to result in a difference\cite{HRCwebCalib} of at most a few percent, and correcting for bias angle has been neglected. In order to examine the potential effects of bias angle on the result, the ratio of the +1 order to the -1 order was taken. Any systematic asymmetry would most likely be ascribed to grating asymmetry in these orders, detector asymmetry due to bias angle, or to nonuniform QE effects across the detector (known to be small). The result is given in Figure~\ref{fig:hrc_hegasym} for the HEG grating, which is more likely than the MEG to show intrinsic asymmetry and which disperses across more of the HRC-I surface. The plot reflects asymmetry due to all effects: the asymmetry is obviously very small in comparison with other errors. Thus, neglect of bias angle and detector uniformity corrections is acceptable. Table~\ref{tbl:hrc_effects} gives a summary of the various effects that have been discussed and their impact on the results. \begin{table}[h]\centering \begin{tabular}{|c|c|c|} \hline\hline Error & magnitude & Comments \\ \hline\hline Counting Statistics & 10\% to 30\% & accounted for in analysis\\ \hline Background subtraction & up to 3\%, systematic & only detector background used \\ \hline bias angle & few percent & neglected \\ \hline detector QE nonuniformity & 5 to 10\% within 35~mm radius; edges drop by 20\% & neglected \\ \hline Event saturation & 10 \% to 40\% systematic & accounted for: all events included \\ \hline\hline \end{tabular} \caption{\small \label{tbl:hrc_effects} Corrections, Systematic Effects and Errors for HETG + HRC-I} \end{table} \begin{figure} % following was fig2_new.ps \psfig{figure=hrc_heg_asym.ps,height=9cm} \caption{\small \label{fig:hrc_hegasym} Ratio of +1 to -1 for HEG grating on HRC-I. In general, departures from unity are expected to be caused by intrinsic grating asymmetry, detector nonuniformity, or bias angle effects.} \end{figure}