MIF's Interface with IOO
Carrier
iKAGRA
Wavelength |
1064nm |
Comment |
Power |
>500mW at PRM AR |
More than 1W desirable |
Polarization |
S |
|
Complex beam radius at the PRM AR |
9.8358048093144834+i*18.307397678406861 |
So called q-parameter in the unit of m. Although there is no PRM in iKAGRA, this is a beam parameter at the position where the AR surface of the PRM will be located in bKAGRA. This parameter gives the perfect mode match to the iKAGRA arm cavities. However, the MIF does not require IOO to provide 100% mode matching in iKAGRA phase. More than 60% of mode matching is the current requirement, which allows us to use the same IMMT as bKAGRA. |
Frequency Noise |
To be calculated from the viewpoint of lock acquisition. |
Residual frequency noise after the MC. |
Relative Intensity Noise |
To be calculated from the viewpoint of lock acquisition. |
|
Beam Jitter |
1e-6 rad RMS |
Calculated by requiring that beam spot moves less than 1mm after traveling 3km. |
bKAGRA point of view
Wavelength |
1064nm |
Comment |
Power |
75W at PRM AR |
|
Power adjustability |
750mW to 75W continuous |
(TODO: decide where to put variable attenuators) |
Polarization |
S |
|
Complex beam radius at the PRM AR |
-10.580258464886768+i*56.648923633432595 |
So called q-parameter in the unit of m. |
Frequency Noise |
Residual frequency noise after the MC. For more detailed discussion, see this. |
|
Relative Intensity Noise (AF) |
|
|
Relative Intensity Noise (RF) |
< 2.7e-9 @ above f1 frequency |
RF RIN at the input to the MIF (i.e. MC trans) (TODO: more detailed calculation) |
RFAM amplitude |
to be calculated |
Static RFAM amplitude after MC. |
RFAM phase jitter |
to be calculated |
Tolerated RFAM phase fluctuations. It should depend on the RFAM amplitude. |
Beam Jitter |
3e-11 rad/rtHz@10Hz, 7e-14 rad/rtHz@100Hz (Safety mergin of 20) |
Modulations
iKAGRA
Name |
Freqency |
Type |
Mod. index |
Relative Amplitude to Carrier before PRM |
Comment |
fPMC |
15MHz |
PM |
|
|
|
fIMC |
51.72MHz |
PM |
|
|
also used for FRC locking |
f1 |
16.88MHz |
PM |
0.1rad |
|
|
bKAGRA
Name |
Frequency |
Type |
Mod. index |
Relative Amplitude to Carrier before PRM |
Oscillator Phase Noise |
Oscillator Amplitude Noise |
Comment |
fPMC |
15MHz |
PM |
|
|
|
|
|
fRefCav |
51.75MHz |
PM |
|
|
|
|
|
f1 |
16.880961MHz |
PM |
0.2rad (nominal 0.15) |
|
|
||
f2 |
45.0159MHz |
PM |
0.1rad (nominal 0.05) |
|
|
||
f3 |
56.2699MHz |
AM |
point of view0.05 |
|
|
|
Non-resonant sidebands to be used only for lock acquisition. Modulation index value, m, means the carrier field amplitude E0 (not power) is modulated by m*E0 (so, the sideband amplitude is m/2*E0; checked with Optickle). This SB is turned off once the interferometer is locked. |
2*f3 |
112.5398MHz |
AM |
less than ?? |
|
|
|
Maximum permitted 2nd harmonics amplitude of f3-AM. To be calculated from the error signal availability during lock acquisition. |
f1-AM |
16.880961MHz |
AM |
65% of PM amplitude |
|
|
|
Optional. Modulation phase should be aligned with PM. |
fIMC |
13.78 MHz |
PM |
0.025? |
|
|
|
Modulation depth written is from aLIGO value; JGW-T1605493 |
fALSX |
33 MHz |
PM |
? |
|
|
|
|
fALSY |
32 MHz |
PM |
? |
|
|
|
Assumed modulator arrangement
In the Optickle modeling, f1, f2 and f3 modulations are applied in series in this order. Optickle can properly handle the generation of sidebands on sidebands. So it is confirmed that series modulation is OK for bKAGRA. In practice, it may be better to apply f3 modulation first. This is to be discussed with IOO.
RFSB transmission servo
The RFSB frequencies (f1 and f2) should be set to maximize their power inside PRC, i.e. fully resonant in the central part of the interferometer. Therefore, at first, the MC length has to be adjusted to transmit the RFSBs optimized in frequency for the main interferometer. After the DC adjustment, however, small continuous adjustment to the RFSB frequencies to minimize the RFAM generation by the transmission through the MC should be performed by a RFSB transmission servo. Note that MIF does not require this servo to be implemented in the iKAGRA phase.