1. Stefan Hild (University of Birmingham) + A.Freise, M.Mantovani, A.Perreca Advanced Virgo telecon, June 2008 Why use FinesseTools for Advanced Virgo simulations, a simple example.

2. S. HildAdvanced Virgo, 19th of June 2008 Slide 2 Outline  Motivation: Why to use FinesseTools for OSD-work?  Infrastructure for OSD-Simulations  Advanced Virgo OSD_Tools SVN  Example of an OSD_Tool_function  Calculating the mirror ROCs for a given beam size  Current baseline of ROCs for main and recycling mirrors

3. S. HildAdvanced Virgo, 19th of June 2008 Slide 3 Introduction: Why to use FinesseTools for OSD simulation work  We need to do plenty of simulations for Advanced Virgo  Many of these simulation task are fairly big constructs (for instance producing control matrix)  Many parameters are not fixed and might change several times within the next year or so  For instance: mod frequencies, Schnupp asymmetry,...  Many design options are available which might completely change everything  For instance degenerate recycling cavities  We will have to do the simulations many times, with several parameter set, several optimization criteria …

4. S. HildAdvanced Virgo, 19th of June 2008 Slide 4 Introduction: Why to use FinesseTools for OSD simulation work  IDEA: Build up a collection of (semi) automated scripts and functions, called OSD_Tools For instance for:  Calculating the mirror ROCs for a given beam size  Calculating the optimal Schnupp length for given modulation frequencies  Calculating the length of the SR-cavity for given Schnupp length and modulation frequency  Calculating an optimized Control matrix for a given IFO configuration  These scripts and functions always read in the current Advanced Virgo parameter set (from Finesse baseline file) and give back an optimized parameter set.  Example scenario:  Suppose the length of one recycling cavity changes  Need to redo the full length control scheme (including all noise propagations).  OSD_Tools can make things easier, more reliable and better documented.

5. S. HildAdvanced Virgo, 19th of June 2008 Slide 5 Infrastructure: OSD-SVN  A dedicated SVN for OSD Simulation effort  All scripts and input files are stored in a subversion repository including backup and version control.  This svn can be read by the public:  Server: svn://lnx0.sr.bham.ac.uk  Repository: adv-osd  Everybody is welcome to join …

6. S. HildAdvanced Virgo, 19th of June 2008 Slide 6 Infrastructure: OSD-SVN  Four main directories  Finesse-files:  Current and Previous input files (Parameter documentation)  OSD-tools:  Top Level OSD-function  FinesseTools  Tasks:  Example scripts how to run the Top Level OSD-functions

7. S. HildAdvanced Virgo, 19th of June 2008 Slide 7 Example: Determine the mirror ROCs for a given beam size  The value for the Advanced Virgo beam size is likely to change in future:  There is a current baseline value (6.0cm)  New info about …  Size of flats  Geometry and type of actuators  FFT simulations … will make it necessary to modify the beam size  The lengths of the recycling cavities is not fixed:  For each length the recycling mirrors need to have a an adjusted curvature  Every time the beam size or the cavity lengths changes we have to recalculated all the curvatures of the mirrors.  It would be nice doing these calculations always by just pressing a single button (I.e. running a single function.)

8. S. HildAdvanced Virgo, 19th of June 2008 Slide 8 OSD_ROC.m: What does it do? 1.Reads in the current an Advanced Virgo configuration from the current Advanced Virgo Finesse file (advirgo-base-xxxxxx.kat) 2.Switches off all cavity commands and use the pure eigenmode of the arm cavities. 3.Produce and run new Finesse simulation: beam size over main mirror ROC 4.Find main mirror ROC value corresponding to the wished beam size 5.Repeat step 3. and 4. with higher resolution (2nd iteration) 6.Write the new ROC value to the main mirrors. 7.Produce and run new Finesse simulation: beam parameter detector at the recycling mirrors 8.Calculates from z and z_r values the wavefront curvature of the recycling mirrors. 9.Writes a new Advanced Virgo input file, containing the new ROC values. (This file can then be used by the next OSD-Tool-function…)

9. S. HildAdvanced Virgo, 19th of June 2008 Slide 9 OSD_ROC.m: What does it do?  For further detail, please look at the help of the function:

10. S. HildAdvanced Virgo, 19th of June 2008 Slide 10 Current baseline for beam size and mirror curvatures

11. S. HildAdvanced Virgo, 19th of June 2008 Slide 11 Documentation on the Wiki  Available on the AdV-OSD-Wiki:  Very brief summary of beamsize analysis  Current working values for mirror curvatures https://workarea.ego-gw.it/ego2/virgo/advanced- virgo/osd/beam-sizes

12. S. HildAdvanced Virgo, 19th of June 2008 Slide 12 E N D