Presentation on theme: "Polarization Angle Calibration by the Wiregrid rotation Osamu Tajima (KEK) Presented by Hogan Nguyen (FNAL)"— Presentation transcript:
Polarization Angle Calibration by the Wiregrid rotation Osamu Tajima (KEK) Presented by Hogan Nguyen (FNAL)
Osamu’s Idea to Optimize All Modules Simultaneously in a Compact Footprint The first sparse grid to show proof-of-principle The current grid: -motorized -no position encoding (sorry) -protection cover not shown
Sparse Wiregrid on the Deck ! Q1 U1 U2 Q2 Fitting PDF f(t; A0, A1, A2, w, d1, d2) = A0 + A1 cos(wt – d1) + A2 cos(2wt – d2) d2 polarization angle A2 demod gain (* w was treated as common fixed parameter for all the horns, its value is obtained from central horn fitting) Wiregrid was rotated counter clockwise (look sky from the module)
Comparison with Other Calibrations Wiregrid Moon Wiregrid TauA Moon TauA Syst. diff. in Q1 & Q2 Syst. diff. in Q1 & Q2 2-3 deg. Diff. in all diodes ?
Comparison with Other Calibrations (cont.) Wiregrid Moon Wiregrid TauA Moon TauA Syst. diff. in Q1 & Q2 Syst. diff. in Q1 & Q2 2-3 deg. Diff. in all diodes ?
Relative Demod Amplitude RQ_0000 Q U U Q RQ_0001 Q U U Q RQ_0002 Q U U Q RQ_0003 Q U U Q RQ_0004 Q U U Q RQ_0005 Q U U Q RQ_0006 Q U U Q RQ_0007 Q U U Q RQ_0008 Q U U Q RQ_0009 Q U U Q RQ_0010 Q U U Q RQ_0011 Q U U Q RQ_0012 Q U U Q RQ_0013 Q U U Q RQ_0014 Q U U Q RQ_0015 Q U U Q Possible systematic error has not been estimated, yet
Ratio of Relative Demod Amplitude to Relative gain obtained from skydips (normalized to center horn Q1) Q1 U1U2Q2 Q1 U1U2Q2 ratio deg. Further Investigations are necessary to have conclusion Most of them are lower than 1 while skydip uncertainty ~10% Demod TP differences ? TauA/skydip seems to have same tendency How about Moon demod/TP ? Outer radius ratio seems to be small !? Wiregrid signal is not uniform on the array ? Difference of solid angles from wire to ground screen, or other reason ? All Diodes average
Summary We obtained Polarization angle and relative demod gain (signal height) by the sparse wiregrid calibration Polarization Angle – Can be measured with less than 3 deg. accuracy while we have not finished all syst. error study – Wiregrid Moon : Several deg. diff for Q1 and Q2 – Wiregrid TauA : consistent while 2-3 deg. offsets Relative Demod Gain – Cross checks with other calibrations are important
Possible Syst. Error Sources Due to the protection UHMW-PE cover, its rotation effect is visible in total power clearly Its systematic effect have to be estimated Fitting can be improved, too (e.g. leakage is taken into account) Wiregrid polarization signal is obtained from the reflection from all directions. However, top direction is sky temp.(10K) while both sides and bottom are 300K. It might make systematic for amplitude and pol. angle. These possible bias have to be estimated. Contribution from 300K depends on the focal plane position, so magnitude of polarization signal may depend on the position within the array
Following plots are Demod (w/ fitting curves) and TP