ID |
Date |
Author |
Type |
Category |
Subject |
Text |
 |
14910
|
Sun Sep 29 15:58:19 2019 |
gautam | Update | LSC | POX locking attempt | Summary:
There is no visible PDH error signal
on the POX11 channels. As a result, I am |
|
14915
|
Mon Sep 30 14:16:43 2019 |
gautam | Update | LSC | POX PD checkout - solved | I confirmed that there is light incident
on the POX photodiode. So the problem must
lie downstream in the demod / whitening / |
|
14920
|
Tue Oct 1 21:19:51 2019 |
gautam | Update | LSC | PRMI locked on carrier | Summary:
The |
|
14924
|
Wed Oct 2 11:52:16 2019 |
gautam | Update | LSC | PRMI Oplev loop checkout | I measured the OLTF of both the PRM Oplev
loops. Nothing odd sticks out as odd to me
in this measurement - there seems to be ~40 |
|
14926
|
Wed Oct 2 23:15:02 2019 |
gautam | Update | LSC | FPMI locking | Summary:
I was able to lock the FPMI. The
lock was quite stable. However, |
|
14928
|
Thu Oct 3 11:01:18 2019 |
rana | Update | LSC | (PR)FPMI locking | wonder if its possible to do variable finesse
locking
Gabriele mentioned that Virgo used |
|
14933
|
Thu Oct 3 19:40:18 2019 |
gautam | Update | LSC | POX/POY imbalance | Summary:
There is an imbalance between
the POX and POY detector outputs reported |
|
14954
|
Tue Oct 8 18:35:09 2019 |
gautam | Update | LSC | Locking prep | In preparation for some locking work tonight,
I did the following at the POP in air table
with the PRMI locked on carrier: |
|
14960
|
Wed Oct 9 18:15:26 2019 |
gautam | Update | LSC | PRMI 3f locking | After making sure the beams were hitting
the 3f photodiodes on the "AP"
table, I was able to lock the PRMI with the |
|
14961
|
Wed Oct 9 22:02:58 2019 |
gautam | Update | LSC | REFL55 whitening issue | This
problem has re-surfaced. Is this indicative
of some problem with the on-board VGA? Even |
|
14962
|
Thu Oct 10 01:12:56 2019 |
gautam | Update | LSC | Locking studies | Summary:
ALS control of arms in
the CARM/DARM basis seems pretty robust - |
|
14963
|
Thu Oct 10 22:11:53 2019 |
gautam | Update | LSC | Trans QPD checkout |
I removed the flip-mount that was
installed on the EY in-air table for the
mode-spectroscopy project (see |
 |
14973
|
Wed Oct 16 11:42:17 2019 |
gautam | Update | LSC | Poor separation of PRCL/MICH in 3f signals | Summary:
There is poor separation
of the PRCL and MICH length error signals |
|
14974
|
Thu Oct 17 11:19:28 2019 |
gautam | Update | LSC | Locking activity last night |
Tuning the MICH-->PRM
output matrix element
Locked
the PRMI with the carrier field resonant |
 |
14983
|
Tue Oct 22 00:52:27 2019 |
gautam | Update | LSC | Locking updates |
Transition of arms from POX/POY
to CARM/DARM was much smoother today - a
change was made at the EX PDH setup, see |
|
14996
|
Tue Oct 29 01:24:45 2019 |
gautam | Update | LSC | More locking updates | Summary:
The two arm lengths can
be controlled reliably in the CARM/DARM basis |
 |
14997
|
Tue Oct 29 15:13:19 2019 |
gautam | Update | LSC | More locking updates | I looked at some signals for a 10 second
period when the PRMI was locked with at some
CARM offset, just before the PRMI lost lock, |
|
14998
|
Tue Oct 29 17:40:48 2019 |
gautam | Update | LSC | More locking updates | I set up a photodiode (PDA10CF) in the
IFO REFL beampath and the Agilent NA is sitting
on the east side of the PSL enclosure. This |
 |
14999
|
Wed Oct 30 01:27:00 2019 |
gautam | Update | LSC | More locking updates | Tried a bunch of things tonight.
Modified the "ELP300"
filter module in the MICH filter bank - this |
|
15000
|
Wed Oct 30 11:53:41 2019 |
gautam | Update | LSC | MICH loop shape tuning | I changed the shape of the low pass filter
to reduce high frequency sensor noise injection
into the MICH control signal. The loop stability |
 |
15001
|
Wed Oct 30 17:08:40 2019 |
gautam | Update | LSC | POP22 investigation | The POP beam coming out of the vacuum chamber
is split by a 50/50 BS and half is diverted
to the POP22/POP110/POPDC photodiode (Thorlabs |
|
15009
|
Mon Nov 4 15:29:47 2019 |
gautam | Update | LSC | POP signal path | There are many versions of the POP22 signal
path I found on the elog, e.g. this
thread. But what I saw at the LSC rack |
|
15010
|
Mon Nov 4 16:06:58 2019 |
gautam | Update | LSC | POP optical path | I did some re-alignment of the POP beam
on the IX in air table. Here are the details:
|
    |
15012
|
Tue Nov 5 11:52:27 2019 |
gautam | Update | LSC | Locking notes | Summary:
I am still unable to achieve arm
powers greater than TRX/TRY ~10 while keeping |
|
15014
|
Wed Nov 6 02:08:48 2019 |
gautam | Update | LSC | Locking updates | Summary:
There seems to be stronger-than-expected
coupling between CARM and the 3f sensors. |
|
15015
|
Wed Nov 6 17:05:45 2019 |
gautam | Update | LSC | CARM calibration | Summary:
A coarse calibration of the CARM
error point (when on ALS control) is |
  |
15016
|
Wed Nov 6 17:45:34 2019 |
gautam | Update | LSC | ~ | Here is a comparison of the response of
various DoFs in our various RFPD sensors
for two different CARM offsets. Even in the |
|
15026
|
Thu Nov 14 23:56:18 2019 |
rana | Update | LSC | off the bad Violin filters | We turned off many excessive violin mode
bandstop filters in the LSC.
Due to some feedforward work by |
|
15028
|
Fri Nov 15 11:58:12 2019 |
gautam | Update | LSC | off the bad Violin filters | The clue was that the loop X arm POX loop looked
to have low (<3dB)) gain margin around
600 Hz (and again at 700 Hz). |
 |
15029
|
Fri Nov 15 12:08:04 2019 |
gautam | Update | LSC | POPDC whitening board | The DC port of the Bias-Tee is routed to
(a modified
version of) the iLIGO whitening board. |
|
15034
|
Mon Nov 18 21:04:38 2019 |
gautam | Update | LSC | Locking - some ideas | Some ideas Koji suggested:
Try approaching the CARM
offset zero point "from the other side" |
|
15037
|
Wed Nov 20 01:07:18 2019 |
gautam | Update | LSC | Locking - progress | Summary:
CARM offset was reduced
to 0 with the PRMI locked.
TRY |
|
15038
|
Wed Nov 20 12:14:17 2019 |
gautam | Update | LSC | Locking - progress | I took a look at the TRX/TRY RIN reported
in the single arm POX/POY lock, and compared
the performance of the two available PDs |
|
15039
|
Wed Nov 20 17:20:24 2019 |
Yehonathan | Update | LSC | QPD Investigation | {Gautam, Yehonathan}
In search of the source of discrepancy
between the QPD readings in the X and Y arms, |
|
15040
|
Wed Nov 20 17:52:00 2019 |
gautam | Update | LSC | QPD MEDM screen update | Koji and I had noticed that there was some
discrepancy between the switchable gain stages
of the EX and EY QPDs. Sadly, there was no |
  |
15041
|
Wed Nov 20 21:29:28 2019 |
gautam | Update | LSC | PRG ~13 | After the QPD fix, both arms report consistent
buildup - see Attachment #1. The peak values
touch ~250, corresponding to a PRG of ~13. |
|
15042
|
Thu Nov 21 12:46:22 2019 |
gautam | Update | LSC | CM board study | In preparation for trying out some high-bandwidth
Y arm cavity locking using the CM board,
I hooked up the POY11_Q_Mon channel of the |
|
15043
|
Thu Nov 21 13:14:33 2019 |
Koji | Update | LSC | CM board study | One of the differences between the direct
POY and the CM_SLOW POY is the presence of
the CM Servo gain stages. So this might mean |
|
15044
|
Thu Nov 21 19:08:58 2019 |
gautam | Update | LSC | High BW lock of Y arm length to PSL frequency | Summary:
The Y arm cavity length was locked
to the PSL frequency with ~26kHz |
  |
15045
|
Fri Nov 22 00:54:14 2019 |
gautam | Update | LSC | locking notes | [KA, GV]
There was no shaking (that disturbed
the locking) tonight! |
|
15046
|
Mon Nov 25 19:11:22 2019 |
gautam | Update | LSC | ALS noise re-look | I re-checked the ALS noise in the following
configurations:
PRM is misaligned.
Michelson |
|
15049
|
Tue Nov 26 17:07:41 2019 |
gautam | Update | LSC | POX / POY calibration | Summary:
Since we are using the POX and
POY photodiodes as out-of-loop sensors for |
 |
15050
|
Tue Nov 26 18:16:08 2019 |
rana | Update | LSC | POX / POY calibration | ...maybe the opto-mechanical
CARM plant |
|
15051
|
Wed Nov 27 12:16:52 2019 |
gautam | Update | LSC | ITMX and ITMY OSEMs with low and high circulating power | Summary:
The ITMX OSEMs report elevated
noise in the 10-100 Hz band when we have |
 |
15052
|
Wed Nov 27 13:14:02 2019 |
rana | Update | LSC | ITMX and ITMY OSEMs with low and high circulating power | if the RP don't fit
u must acquit
sweep the laser amplitude |
|
15053
|
Wed Nov 27 16:10:29 2019 |
gautam | Update | LSC | AOM reconnected | i reconnected the AOM driver to the AOM
in the main beam path (it was hijacked for
the AOM in the AUX laser path for Anjali's |
|
15056
|
Wed Nov 27 23:24:01 2019 |
gautam | Update | LSC | No shaking but no inspiration either | Summary:
I tried the following minor changes
to the locking procedure to see if there |
|
15057
|
Sun Dec 1 13:38:48 2019 |
rana | Update | LSC | No shaking but no inspiration either | yes, reasonable |
|
15062
|
Tue Dec 3 00:03:57 2019 |
gautam | Update | LSC | Green ALS also shows elevated noise with high arm buildup | Summary: |
|
15073
|
Wed Dec 4 19:54:27 2019 |
gautam | Update | LSC | A look to the past | Trawling
through some past elogs, I saw that the ALS
noise increase as a function of CARM offset |
|