= Arm Length Stabilization System =
 Wiki for ALS (Arm Length Stabilization; Auxiliary Lock System), a.k.a green lock system

{{https://gwdoc.icrr.u-tokyo.ac.jp/DocDB/0077/T1807771/003/ALSSchematic.png|ALS Configuration|width=500}}
 [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7771|JGW-T1807771]]

== To Do ==
 * optical layout of PR2/SR2 chambers, POP/POS table
 * select AOM and AOM driver
  * DONE
 * fix green fiber specs, including how to do the laying
 * fiber collimators for green
 * green fiber after EOM/AOM or before EOM/AOM
  * Not much difference from noise, cable length point of view.
  * Alignment jitter noise from AOM will be less if fiber comes after AOM. So, let it so.
 * fiber for PLL beat or not
  * DECIDED not to use fiber for PLL (Mar 5, 2018)
 * where to put frequency offset: PLL or arm length
 * more detailed noisebudget
 * initial alignment planning
 * comm/diff servo topology
  * necessity of summing node for common mode servo ([[https://dcc.ligo.org/LIGO-D1300782/public|LIGO-D1300782]])
   * first, try with digital switch and decide (Feb 6, 2018)
 * lock acquisition scheme

== List of Items ==
=== Electronics ===
 * Common Mode Servo Board [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=3705|JGW-D1503705]] (ready)
 * PLL Board (similar to CMB, ordered to AEL)
 * Phase Frequency Discriminator [[https://dcc.ligo.org/LIGO-D1002476/public|LIGO-D1002476]] (prototype developed at UToyama)
 * Fast version of IQ Demodulator [[https://dcc.ligo.org/LIGO-E1100044/public|LIGO-E1100044]] (ordered to AEL)
 * RF Oscillator for PDH [[https://www.keysight.com/ja/pdx-x201911-pn-N5181B/mxg-x-series-rf-analog-signal-generator-9-khz-to-6-ghz?cc=JP&lc=jpn|Keysight N5181B MXG]] (ready)
  * FM option N5181BU-UNT (not yet ordered)
 * VCO for PLL [[https://www.keysight.com/ja/pdx-x201773-pn-E8663D/psg-rf-analog-signal-generator-100-khz-to-9-ghz?cc=JP&lc=jpn|Keysight E8663D]] (ready)
 * Frequency counter [[https://www.tek.com/frequency-counter/fca3000-3100|Tektronix FCA3103]] (ready)
 * [[Current driver for the thermal path ALS-X/Y servo]]

=== Opto-electronics ===
 * Broadband PD for PLL [[https://www.newport.com/p/818-BB-21A|Newport 818-BB-21A]] (1.2 GHz bandwidth)
 * Resonant PD for green PDH [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=1280|JGW-D1201280]]
 * AOM G&H 3080-125 (80MHz) and AOM driver G&H 1075FM-1 (1W, 5MHz BW). (ordered)
 * EOM: Qubig EO-T38M3-VIS (ready)
  * modulation frequencies are 32 MHz and 33 MHz [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=5626|JGW-T1605626]]
 * QPD for green beam pointing? (Use Oplev QPD?)
 * Picomotor mount? (ordered)

=== Optics ===
 * Faraday isolator [[https://www.thorlabs.co.jp/thorproduct.cfm?partnumber=IO-5-532-HP|Thorlabs IO-5-532-HP]] (ready)
 * Periscopes [[https://www.thorlabs.com/navigation.cfm?guide_id=54|Thorlabs Ø1.5inch Post Assembly]] (ready)
 * Dichroic mirror for periscopes: LEO DRX-1064/532-45P-UF-2038 (ready: 8pcs(2 each for POP/POS/TRX/TRY))
 * Harmonic splitter: LEO LWP-45-R532-T1064-UF-2038 (ready: 8pcs(1 each for POP/POS/TRX/TRY, 4 spares))
 * Dichroic mirror in-vac: Sigma TFVMQ-50.8C10-20-W1D-532/1064-ARS-30-45D (ready: 4pcs(1 for PR2, 1 for SR2, 2 spares))

=== Fiber optics ===
 * Fiber: Coastal Connections P-FAnskFAnsk-3.5nx/125/3-75 and -80 (under test at UToyama)
  * probably with jacket, with endcap, without AR coating
  * polarization maintaining
 * Fiber collimator ([[https://www.thorlabs.co.jp/newgrouppage9.cfm?objectgroup_id=2940|Thorlabs PAF-X-5-A]]? [[https://www.thorlabs.co.jp/newgrouppage9.cfm?objectgroup_id=5124|Thorlabs triplet lens collimator TC06APC-543]]?)

== Drawings ==
 * PSL table [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=6335|JGW-D1706335]], [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7060|JGW-G1707060]]
 * Fiber layout [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7060|JGW-G1707060]]
 * POP table
 * PR2 in-vac [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=6473|JGW-G1706473]]
 * TRX
 * POS table
 * SR2 in-vac
 * TRY
=== Conceptual ===
 * ALS configuration [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=5353|JGW-T1605353]] (see Candidate4)
 * Optical layout around PRs [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=5261|JGW-T1605261]]
 * Optical layout around SRs [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=5967|JGW-T1605967]]
 * Green beam positions [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7775|JGW-T1807775]]

== Noisebudget ==
 * [[https://granite.phys.s.u-tokyo.ac.jp/svn/LCGT/trunk/kagranoisebudget/GreenLock]]

== Documents ==
 * Document tree for ALS [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=7769|JGW-E1807769]]