'''[[LCGT/subgroup/ifo/ISC/TaskList|..Up]]''' = Lock Acquisition = Lock acquisition scheme has to be planed carefully because it was a big problem in the first generation large-scale interferometers. Probabilistic lock (a.k.a. lucky lock) won't probably work. Other locking schemes such as the arm pre-locking has to be considered. == Auxiliary Lock System == Also known as green laser lock, this scheme will make use of auxiliary lasers to lock the arm cavities first. ---- == Servo simulation == * [[http://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=788|Report in JGWDOC]] == Optical Table Layout == * [[attachment:GrLock_Table_120127.pdf]] == Purchase List == * [[attachment:tatsu_2012_Jan.xlsx]] ---- === SVN archive === [[https://granite.phys.s.u-tokyo.ac.jp/svn/LCGT/trunk/GreenLock/|SVN directory]] === Oscillator phase noise requirement for PLL local oscillator === See [[https://granite.phys.s.u-tokyo.ac.jp/wiki/Lab/index.php?LCGTALSPhaseNoise|here]]. === Overview of Green Lock Scheme === [[attachment:Overview_GreenLock.pdf]] === Lock procedure === [[attachment:Procedure.pdf|PDF]] === Block diagram === [[attachment:BlockDiagram.pdf|BlockDiagram]] === Description of the blocks === ==== Phase Comparison ==== * When you combine two beams with power P, we get the beat note with amplitude of '''2 alpha P Sin phi''', where '''alpha''' is the contrast (0~1) and phi is the relative phase between the fields. '''Thus, the phase sensitivity is 2 alpha P [W/rad]'''. e.g. Two 1mW beams geneartes 4mWpp beat if the contrast is 1. The slope is 0.002 alpha W/rad. * For the broadband PD, InGaAs is not relevant because of the high junction capacitance. If we use Si PD (like FFD-100 phi=2.5mm), the responsivity is '''eta = 0.08 [A/W]'''. * BBPD Transimepedance and the shotnoise intercept current are assumed to be 1e3 [V/A] and 0.3 [mA], from the experience of LIGO BBPD. * '''Total gain is 1 [V/rad]''' if we assume alpha and P to be 0.5 and 12.5mW respectively. * Shot noise * Shot noise of the modulated beam is described by = 2 e [I0+1/2 dI Sin(phi)], according to N. Mio and K. Tsubono, Physics LettersA 164 (1992) 255-258.　Does nonstationary part cancel because of the orthogonality of the RF and LO signals??? * Consider only the stationary part, in = sqrt(2 e I0). Thus in/eta/(2 alpha P) = sqrt(e / eta / alpha / P) [rad/rtHz]. This corresponds to 2.5e-8 rad/rtHz. ==== Frequency noise of NPRO ==== * 1e4/f [Hz/rtHz] according to R. Adhikari's PhD thesis. ==== Shot noise ==== * [[attachment:PC010706.JPG|Shot noise estimation]]