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| 40m Log |
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 Wed Feb 20 23:55:51 2019, gautam, Update, ALS, ALS delay line electronics 
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 Thu Mar 7 01:06:38 2019, gautam, Update, ALS, ALS delay line electronics
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Tue Mar 12 22:51:25 2019, gautam, Update, ALS, ALS delay line electronics
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Wed Mar 13 01:27:30 2019, gautam, Update, ALS, ALS delay line electronics
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Sun Mar 17 00:42:20 2019, gautam, Update, ALS, NF1611 cannot be shot-noise limited?
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Thu Mar 28 19:40:02 2019, gautam, Update, ALS, BeatMouth with NF1611s assembled
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Fri Mar 29 21:00:06 2019, gautam, Update, ALS, BeatMouth with NF1611s installed
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Sun Mar 31 15:05:53 2019, gautam, Update, ALS, Fiber beam-splitters not PM
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Wed Apr 3 09:04:01 2019, gautam, Update, ALS, Note about new fiber couplers
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Wed Apr 3 12:32:33 2019, Koji, Update, ALS, Note about new fiber couplers
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Fri Apr 5 00:33:58 2019, gautam, Update, ALS, Promising IR ALS noise
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Fri Apr 5 11:49:30 2019, gautam, Update, ALS, PSL + X green beat recovery
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Mon Apr 8 00:04:08 2019, gautam, Update, ALS, IR ALS noise budget
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Mon Apr 8 18:28:25 2019, gautam, Update, ALS, EX Green PDH checkout
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Mon Apr 8 23:52:09 2019, gautam, Update, ALS, EX Green PDH error monitor calibrated
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Tue Apr 9 00:16:22 2019, rana, Update, ALS, EX Green PDH error monitor calibrated
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Tue Apr 9 00:18:19 2019, gautam, Update, ALS, EX Green PDH error monitor calibrated
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Tue Apr 9 18:44:00 2019, gautam, Update, ALS, EX Green PDH discriminant measurement
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Tue Apr 9 19:07:12 2019, gautam, Update, ALS, IR ALS noise budget
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Thu Apr 11 01:10:05 2019, gautam, Update, ALS, Large 2kHz peak (and harmonics) in ALS X
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Wed Apr 17 00:50:17 2019, gautam, Update, ALS, Large 2kHz peak (and harmonics) in ALS X no more
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Wed Apr 17 11:01:49 2019, gautam, Update, ALS, Large 2kHz peak (and harmonics) in ALS X no more
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Wed May 29 18:13:25 2019, gautam, Update, ALS, Fiber beam-splitters are now PM
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Fri May 31 15:55:16 2019, gautam, Update, ALS, PSL + X beat restored
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Message ID: 14521
Entry time: Mon Apr 8 00:04:08 2019
In reply to: 14516
Reply to this: 14523
14528
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| Author: |
gautam |
| Type: |
Update |
| Category: |
ALS |
| Subject: |
IR ALS noise budget |
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To start the noise budgeting, I decided to measure the "DFD noise", which is really the quadrature sum of the following terms:
- ZHL-3A (RF amplifier) noise, NF ~ 6dB per spec (~ 1nV/rtHz)
- Delay line demod board noise, ~30nV/rtHz [measurement]
- AA board noise [measurement]
- ADC noise
According to past characterizations of these noises, the ADC noise level, which is expected to be at the level of a few uV/rtHz, is expected to be the dominant noise source.
The measurement was made by disconnecting the NF 1611 free space photodiode from the input to the RF amplifier on the PSL table, and connecting a Marconi (f_carrier = 40 MHz, signal level=-5dBm) instead. The phase tracked output was then monitored, and the resulting digital spectrum is the red curve in Attachment #1. The blue curve is the ASD of fluctuations of the beatnote between the PSL and EX IR beams, as monitored by the DFD system, with the X arm cavity length locked to the PSL frequency via the LSC servo, and the EX green frequency locked to the X arm cavity length by the analog PDH servo.
Conclusions:
Assuming the Marconi frquency noise is lower than the ones being budgeted:
- the measured frequency noise is above the DFD noise - this needs to be budgeted.
- The DFD noise level is consistent with a frequency discriminant of 15 uV/rtHz and an ADC noise level of 3 uV/rtHz at high frequencies.
Next noises to budget:
- In-loop X arm length noise
- In-lop EX laser frequency noise
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