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| ## page was renamed from Upgrade 09/Optical Layout <<TableOfContents(4)>> ------ = ►Change in the optical layout = == Overview == The major change in the optical layout is the change of the cavity lengths for PRC and SRC. Since the modulation frequencies of 11MHz and 55MHz are used for the control of the interferometer, the lengths of PRC and SRC are significantly streched. The actual modulation frequency is 11.065399MHz and its integer multiples. (based on the measurement of the MC length on 29th Sept, 2009) This corresponds to the cavity lengths of about 6.8 m and 5.4 m for the PRC and SRC, respectively. For the correct amount of those lengths, visit [[IFO Modeling]] pages. These cavity lengths result in numbers of modifications in the optical configuration: * In order to accomodate longer PRC and SRC, they have to be folded across the several optical tables. * The curvature radii of PRM and SRM are recalculated accordingly. * We are going to employ 2inch flat folding mirrors suspended with Enhanced LIGO/Advanced LIGO style Tip-Tilt suspensions with passive damping using eddy current. |
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| The optical layout in the central part will be changed significantly to house folded recycling cavities. The current layout plan is posted[javascript:void(0);/*1233715079048*/ here]. |
'''[Latest]''' The new optical layout plan as of Dec 18, 2010. This reflects the latest installation of the optics in the vacuum chambers. attachment:101218_40m_upgrade_layout.pdf The main beam (red) and the pick-off beams (pale blue) indicated by three parallel lines has 18mm diameter. This indicates 6w, where w is the beam radius. The waist size of the arm cavity is about 3mm (1/e^2 radius) and the Rayleigh range is about 27m. - To Do: * Output MMT == Archive of the previous layouts == === - Previous layouts by Y. Aso === Previous optical layout by Y. Aso, attachment:40mUpgradeOpticalLayoutPlan01.pdf Zoom of the optical layout by Y. Aso, attachment:layout-zoom.pdf The CAD files canbe found in /cvs/cds/caltech/users/aso/doc/CAD40m/2D/40mUpgradeOpticalLayoutSRMinITMX.dwb This is VariCAD file. VariCAD is installed on rosalba and allegra. . '''*** Now KA switched from VariCAD/dwb to AutoCAD/dwg based work. Reason:''' * The original AutoCAD file is provided by M. Smith. * During the dwg->dwb conversion, a lot of information is lost. * Because of this, it turned out (for KA) that precise work in VariCAD is totally difficult. * Layer function of VariCAD is too weak to work with. === - RSE layout by M. Smith === attachment:40m_opt_layout_Orig_with_comment.pdf = ►Radii of curvature = Here is the Mathematica notebook I wrote to calculate various parameters for the new recycling cavities.[attachment:NewRecyclingCavities.zip attachment:NewRecyclingCavities.zip] The PDF version is here: [attachment:NewRecCav.pdf attachment:NewRecCav.pdf] [attachment:GaussianOpticsTutorial.pdf attachment:GaussianOpticsTutorial.pdf] This notebook explains how the cavity lengths, recycling mirror ROCs, PRM reflectivity are chosen. '''Note: This calculation does not include the effect of the arm cavity. Thus the length of the cavities are slightly different from the actual desired values.''' = ►Effect of the wedge = <<Anchor(wedge)>> All of the main optics have wedge angles of several degrees in order to avoid undesirable interference of back-surface reflections into the main beam. Because of these wedges, we need to design the optical path slightly shifted from the normal angles.In order to incorporate the effect of the wedges, a Mathematica code to calculate the beam deflections has been developed. attachment:wedge_analysis.nb attachment:ITMY_wedge_1deg.png [attachment:wedge.pdf attachment:wedge.pdf] |
Contents
►Change in the optical layout
Overview
The major change in the optical layout is the change of the cavity lengths for PRC and SRC. Since the modulation frequencies of 11MHz and 55MHz are used for the control of the interferometer, the lengths of PRC and SRC are significantly streched.
The actual modulation frequency is 11.065399MHz and its integer multiples. (based on the measurement of the MC length on 29th Sept, 2009)
This corresponds to the cavity lengths of about 6.8 m and 5.4 m for the PRC and SRC, respectively. For the correct amount of those lengths, visit IFO Modeling pages.
These cavity lengths result in numbers of modifications in the optical configuration:
- In order to accomodate longer PRC and SRC, they have to be folded across the several optical tables.
- The curvature radii of PRM and SRM are recalculated accordingly.
- We are going to employ 2inch flat folding mirrors suspended with Enhanced LIGO/Advanced LIGO style Tip-Tilt suspensions with passive damping using eddy current.
New Optical Layout plan
[Latest] The new optical layout plan as of Dec 18, 2010. This reflects the latest installation of the optics in the vacuum chambers.
attachment:101218_40m_upgrade_layout.pdf
The main beam (red) and the pick-off beams (pale blue) indicated by three parallel lines has 18mm diameter. This indicates 6w, where w is the beam radius. The waist size of the arm cavity is about 3mm (1/e^2 radius) and the Rayleigh range is about 27m.
- To Do:
- Output MMT
Archive of the previous layouts
- Previous layouts by Y. Aso
Previous optical layout by Y. Aso, attachment:40mUpgradeOpticalLayoutPlan01.pdf Zoom of the optical layout by Y. Aso, attachment:layout-zoom.pdf
The CAD files canbe found in /cvs/cds/caltech/users/aso/doc/CAD40m/2D/40mUpgradeOpticalLayoutSRMinITMX.dwb
This is VariCAD file. VariCAD is installed on rosalba and allegra.
*** Now KA switched from VariCAD/dwb to AutoCAD/dwg based work. Reason:
- The original AutoCAD file is provided by M. Smith.
During the dwg->dwb conversion, a lot of information is lost.
- Because of this, it turned out (for KA) that precise work in VariCAD is totally difficult.
- Layer function of VariCAD is too weak to work with.
- RSE layout by M. Smith
attachment:40m_opt_layout_Orig_with_comment.pdf
►Radii of curvature
Here is the Mathematica notebook I wrote to calculate various parameters for the new recycling cavities.[attachment:NewRecyclingCavities.zip attachment:NewRecyclingCavities.zip] The PDF version is here: [attachment:NewRecCav.pdf attachment:NewRecCav.pdf] [attachment:GaussianOpticsTutorial.pdf attachment:GaussianOpticsTutorial.pdf]
This notebook explains how the cavity lengths, recycling mirror ROCs, PRM reflectivity are chosen.
Note: This calculation does not include the effect of the arm cavity. Thus the length of the cavities are slightly different from the actual desired values.
►Effect of the wedge
All of the main optics have wedge angles of several degrees in order to avoid undesirable interference of back-surface reflections into the main beam. Because of these wedges, we need to design the optical path slightly shifted from the normal angles.In order to incorporate the effect of the wedges, a Mathematica code to calculate the beam deflections has been developed. attachment:wedge_analysis.nb
attachment:ITMY_wedge_1deg.png [attachment:wedge.pdf attachment:wedge.pdf]