Dec 1st, 2011 Meeting of the 40m Technical Advisory Committee

Link to the slides https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=76382

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I. Personnel

1. Current members
2. Joe B gone to Louisiana...
3. A new grad student Den joined
4. Long visit by Mirko(AEI), Katrin(AEI), Keiko(LSU), and Anamaria (LSU)
5. Current crew: Kiwamu Izumi (GS - March), Jenne Driggers (GS), Denis Martynov (GS), Jamie Rolllins (PD), Suresh Doravari (PD-April), Steve Vass, Koji, Rana

II. Overview of the presentation

• Current Status

  1. Under each subsystem (IFO&SUS, RF, LSC, CDS) we discuss

     1. An overview of the subsystem
     2. Work completed since last TAC
     3. Work in progress just now
• Future projects
  1. Compare and contrast the features of the 40m vs (LHO and LLO)
  2. Outline projects which are planned for the near future (6 months)
  3. Specific deliverables where ever possible.

III. Current Status / Recent and Ongoing Work for each subsystem

1. Optics and Suspensions
   • An overview of the new optical layout (high lighting the differences from the previous plan)
     • ITMs and ETMs are dichroic, mass/finesse chosen such that the radiation pressure effects are enhanced
     • PRC is resonant with 11 MHz, 55 MHz and the carrier (PSL)
     • SRC is resonant with 55 MHz
     • Small Schnupp asymmetry
     • Additional optics installed to route the green beam from the end tables to the PSL table
     • Tip-tilts (with blades) are installed with new suspensions: some characterization done (SURF project)
   • Status:
     • All optics suspended and installed according to the new plan in the vacuum chamber
     • The chamber has been evacuated and has reached operational vacuum pressure
     • Arm lengths have been readjusted
     • Rearrangement of the green optics done
     • Rearrangement of pick off optics done (POX/POY/POP are now available)
     • A new procedure to diagonalize the suspension input matrix has been developed (link to poster in DCC)
2. Length Sensing and Control
   • An overview of the Current status
     1. PSL locked to MC length (in IR) w/ HV. No feedback to MC length!
     2. X-end and Y-end laser frequency locked to each arm length (in 532nm)
     3. Single-mode fiber brings X-end / Y-end NPRO light to the PSL table for IR beat
     4. Handing off of the single-arm ALS was demonstrated
     5. Refinement of the LSC model and screens done
   • Work in progress:
     1. Y arm Green noise budget and handing off test
     2. automation/sequencing of single arm ALS acquisition
3. Alignment Sensing and Control
   • An overview of the Current status
     1. MC alignment is controlled by WFS / IOO-WFS model w/ lockins, matrices, scripts, etc.
     2. Dither beam alignment system installed: uses suspension A2L to measure/maintain spot positions
   • Work in progress:
     1. Study of optimal WFS-ASC control in MC (incorporating the MC_TRANS_QPD for slow centering control)
4. Electronics (RF system)
   • An overview of the new RF system
     • The layout and the measurement scheme
   • Status
     • Done: Multiple frequency RF generator to preserve the phase noise performance of the oscillator
     • Done: RF signal distribution (oscillators, splitters, amplifiers, etc.)
     • Done: Triple-Resonant EOM (New Focus KTP + resonant circuit) prototype installed
     • Ongoing: Finish the PDs / Install the photodiodes on the tables; characterization of all the PDs underway
     • Done: RFAM monitor installed
   • Work in progress:
     • Reduction of RFAM using a heater on the EOM crystal
5. Control and Data Systems
   • Done: All of the new CDS hardware installed
     1. All 5 IO chassis and computers installed: c1lsc, c1sus, c1ioo, c1iscex, c1iscey
     2. New frame builder computer and code running, recording, and serving data
   • Done: Local damping has been achieved on all suspended optics with the new CDS system
   • Done: Have working reflected memory networks communicating between computers
     1. Both old GE Fanuc and the new Dolphin PCIE reflected memory networks installed
   • 1/2 Done: "Simulated plant" taken by JoeB to LLO
     1. virtual suspension can be controlled by the actual realtime controller

IV. Future Projects

1. Comparison of the 40m and the LHO/LLO instruments
2. Length Sensing and Control
   • Deterministic full lock acquisition through auxiliary green laser locking
   • Locking sequences: successively increasing the length of the primary length reference
   • Coherent lock of the three lasers (PSL and two auxiliary lasers)
3. Adaptive seismic noise cancellation
   • seismometers are back in action installed near the 40m arms
   • determination of the transfer function matrices
   • closing the feedforward loops to arm cavities
   • implementing the algorithms in CDS
4. What is the future of the 40m?
   • What to prototype (if anything) for LIGO 3G?
   • Dual-carrier / local readout schemes ?
   • Any use to speedmeter, variational readout schemes? (SQZ cav happening at MIT)

V. End

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