Polarization SYS#224, 225. Hiroshi Nagai (NAOJ) With the help by K. Nakanishi (JAO/NAOJ), Y.-W. Tang (ASIAA), E. Chapillon (ASIAA -> French ARC-node)

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1 Polarization SS#224, 225 Hiroshi Nagai (NAOJ With the help by K. Nakanishi (JAO/NAOJ,.-W. Tang (ASIAA, E. Chapillon (ASIAA -> French ARC-node

2 erification ites On-axis (#224 Instruental polarization (D-ter < 10% Residual after calibration <1% -> 0.1% error on a polarization iage These apply over 30 deg in aziuth or elevation and with a calibration interval 4 hours Off-axis (#225 D-ter within the -6dB priary bea < 10% after the subtraction of on-axis D-ter Residual after calibration and after on-axis D-ter has been reoved < 2% -> This stateent should be revisited These apply over a range of antenna elevation of 5 to 80 degrees and with a calibration interval of 20 days

3 What s D-ters? Mostly originates in antenna and frontend Typically a few % at on-axis field i U Q D D I i U Q D D I U Q I U Q I n n n n n n = = = = cos(2 sin(2 ( cos(2 sin(2 ( sin(2 cos(2 sin(2 cos(2 * * * * * * D D = = The D ters: fraction of the input signal voltage in one polarization that leaks into the output of the other polarization.

4 On-axis requireents ALMA Scientific Specifications and Requireents Polarized flux error (σ p < 0.1% There are two D-ters for each of ~50 antennas. (in total 100 independent D-ters If the residual error after D-ter calibration per antenna is ~1%, the polarized flux error on a iage will be 0.1% (=1%/sqrt(100. Assuing 10% calibration accuracy, the D-ter shall be <10%. These applies over a typical calibration cycle (4- hrs.

5 Off-axis requireents There is no scientific constraint on the off-axis polarization in ALMA Scientific Specifications and Requireents. SysTech Requireents (by D. Slaek assue that the off-axis D-ter requireent applies after the on-axis D-ter has been reoved by calibration. (D off -D on <10%, and residual D off after the calibration and after on-axis D-ter reoved < 2% Above stateent is not very clear, but, for the oent, we test: (D off -D on <10% the polarized flux error at off-axis is not greater than 0.1% on a polarization iage after the on-axis calibration.

6 On-axis: Procedure Observe a bright polarized quasar over a wide range of parallactic angle (>90deg?? and then separate source polarization and D-ters The source ust be polarized at a level of few % See the polarization calibrator list (CS-2721 Typical observation: 3in x 6 scans / frq. tuning Appropriate parallactic angle range is to be tested (CS-2910 For the stability check, observe two polarized quasars separated by >4 hrs in hour angle. Copare two D-ter solutions to check the stability

7 Exaple of D-ters B3, D04 B6, DA42 Real Real Iag B7, D04 Real Iag Typically few % Meets the requireent Iag

8 Exaple of polarization iage Stokes Q (left and U (right ap after the D-ter calibration. The rs on the iages are <<0.1% of Stokes I Meets the requireent

9 Stability Blue (Dx and red (Dy are solutions fro , and cyan (Dx and pink (Dy are solutions fro 3c279. Two solutions agree within a level of ~0.5%. Meets the requireent

10 On-axis Status B3 B6 B7 Observa tion Analysis Observa tion Analysis Observa tion Analysis D-ter level Done Done Done Done Done Done Error on pol. Iage Done Done Done Done Done Done Stability Done Done Done Done Done Not All observations were in TDM ode at two frequency tunings with 12- array. Future works FDM ode ore frequency tunings Band 4,8,9 7 array

11 Off-axis: Procedure Mosaicing to cover the -6dB contour So far we have tested within -3dB 9 x 9 osaic at several parallactic angles

12 Exaple of off-axis D-ters D-ter level is as large as 15% at soe frequency in bands 3 and 6. D off -D on >10%: does not eet the requireent Band-7 D-ter level is good. ~5% at the -3dB contour

13 Error on Polarization Iage Band 6 < 0.1% of Stokes I within -3dB contour Meets the requireent

14 Status B3 B6 B7 Observa tion Analysis Observa tion Analysis Observa tion Analysis D-ter level Error on pol. Iage Stability Not Not Not Not Not Not All observations were within -3dB contour in TDM ode at one frequency tunings with 12 array Future works Out to -6dB contour FDM ode ore frequency tunings Band 4,8,9 Stability 7 array

15 Hand-over? Basic script for data analysis is attached in the report #224, but there is still roo for iproveents I can continue to work on these polarization verification with an agreeent by EA Porject Manager (S. Iguchi. I believe K. Nakanishi will also continue to work in CS side.