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Optical Anchor / Interferometer Status: June, 2004

Optical Anchor / Interferometer Status: June, 2004. Josef Frisch. Concept (still just a cartoon). Interferometer. Commercial unit manufactured by Zygo. Single axis purchased, expandable. Heterodyne interferometer Offset frequency set by RF acousto-optical cell

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Optical Anchor / Interferometer Status: June, 2004

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  1. Optical Anchor / Interferometer Status: June, 2004 Josef Frisch

  2. Concept (still just a cartoon)

  3. Interferometer • Commercial unit manufactured by Zygo. • Single axis purchased, expandable. • Heterodyne interferometer • Offset frequency set by RF acousto-optical cell • Good immunity to optical noise • Lambda / 2048 measurement • Low “data age” – allows easy feedback. • Includes: Laser, single axis interferometer, detector, cables, etc.

  4. Interferometer Specs • 0.15nm + 0.5ppb resolution • No detailed noise specs • Expect noise to be better for short timescales • Performance likely limited materials drift • Probably need vacuum transport • Index change of windows with temperature • Thermal expansion of supports • Should be adequate for 1nm stability (relative to ground)

  5. Tasks • Receive Laser (June 2004) • Data acquisition software • Simple test setup to verify basic operation • Test setup for stability / noise • Who guards the guardsmen? • Feedback Software development • Test single axis feedback system • Purchase multi-axis system (6 or 12 axis) • Install system at ATF • Test multi-axis feedback

  6. Data Acquisition • This is probably the most critical issue! • Interferometer in VME format • Plan to integrate with Vibration / ATF VME data-acquisition. • Already have software platform for multi-axis feedback • Requires significant infrastructure for operation • VME crate, VME controller. Unix server. • Software development also requires: • VxWorks development platform

  7. Testing • Plan for Mike Hildrith to test system • Has time and student. • Physical infrastructure for testing probably not too difficult. • What to do about DAQ • Need VME crate + controller (~$12K) • Need host platform / software

  8. System testing software options (1) • Use Vibration / ATF SLAC system • Existing vibration system provides flexible multi-axis characterization and feedback capabilities • Linda Hendrickson guesses “end of summer” to have data acquisition system for interferometer. (will have better estimate when manuals arrive) • Additional manpower may speed this up (but ramp-up time)

  9. System testing software options (2) • Mike Hildrith develops driver compatible with vibration system. • Allows for easy future integration with other data acquisition. • Would need to either purchase VxWorks development environment, or use the SLAC environment remotely.

  10. System testing software options (3) • Develop completely independent platform for testing. • Might be simpler for initial testing. • Would need to re-do work to integrate with existing system, or re-do the very large amount of effort already applied to existing system. • Interferometer hardware required for development, so this would delay driver development at SLAC

  11. Present DAQ system operation • Realtime (vibration) feedback runs at ~1KHz on private bus to DSP • Vibration data (~100KB/sec) from DSP -> crate controller -> ethernet -> NFS • Nanobpm data (~10KB/sec) from crate controller -> ethernet -> EPICS • Scopes independent.

  12. Changes for next generation • Use PPC processor • Feedback calculations in crate controller • Need real time operation of crate controller • Add interferometer support • Looks similar to vibration sensors • Optionally add PC with LabView for scope control. • Use LabView to EPICS interface to centralize data • Optionally replace Solaris NFS server with PC NFS server also running labview

  13. Future direction of software • LabView • Wide variety of hardware supported (in pc format) • Poor support for VME or real time. • EPICS • Wide use in accelerator community • Existing interface to real –time system • Difficult to learn • Make it look like new LCLS system (VME/EPICS)? • Some hardware only in VME • Interferometer (best), 100Ms/s ADC (cheapest) • Good crate density. • Minimal system large and complex • PC bus advantages • Labview, variety of hardware, cheap processing / data storage. • Poorly suited to real-time

  14. Other Tasks • Interferometer support hardware • Probably need vacuum transport lines • Mount corner cubes to support frame / ground (in vacuum?) • Temperature stabilization • 1nm over 1M scale length is ~.0001 degree C. • Support redesign for feedback: • Soft supports, Fast actuators

  15. Goals of Interferometer / optical anchor system • Stabilize a test mass – the NanoBPM support frame • Can measure performance above ~0.1Hz using STS-2 seismometers. • May need multiple seismometers to compare with ground ! • Need to understand beam based experiments. • Can we compare 2 support frames with beam? (may be difficult to get 1nm given lever arm). • 3 independently supported NanoBPMs?

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