Schedule for BSC9 Vent and ETMX Assessment and Cleaning
Approved work to be done:
The last step is at the time and discretion of the Vacuum crew.
Kyle, Gerardo, Bubba -> Installed HAM1 east door (every other bolt) -> Pumping annulus Kyle, Gerardo -> Closed GV20 -> Started slow vent of X-end Bubba -> Staged/Status prep for BSC9 West door removal slated for tomorrow morning Kyle, Gerardo, Bubba -> Installed BSC10 North door -> Not pumping BSC10 annulus or Y-end until others "sign-off" on readiness tomorrow
LVEA: Laser Hazard Observation Bit: Commissioning 06:15 Karen & Cris – Cleaning at End-Y 09:16 Elli & Thomas – In the LVEA working on HWS alignment 09:25 Hugh – Working on HAM3 CPSs 09:35 Aaron – In Beer Garden terminating cables 10:00 Jeff & Nutsinee – Tour of LVEA 10:15 Water sampling company on site to test water 10:26 Betsy & Travis – Going to End-Y 10:30 Kyle, Bubba, & Gerardo – HAM1 door install 11:08 Cris – Taking garb to End-X 11:40 Thomas & Elli – Out of the LVEA 12:08 HAM1 door installed 12:30 Dave & Jim – Going to End-Y to connect a HWD monitor cable 13:00 Manny – Dropping of parts at End-X 13:05 Shut down Picomotors at End-X to prep for vent 13:10 Kyle – Going to End-X to soft close GV20 for vent 13:30 Bubba – Going into the LVEA to gather tools for End-X Vent 13:32 Manny – Delivering parts to End-Y 14:00 Rick – Going to End-Y 14:30 Started venting BSC9 15:30 Robert – Going to beam enclosure just short of Mid-Y
Krishna, Sheila, Hugh, Fabrice:
We have been chasing large amplifications at low frequencies (in the range of 10mHz to 30mHz) caused by the Z zensor correction of HEPI, which is necessary to reduce the Z to RZ coupling on Stage 1. It looks like the Z HEPI inertial isolation is causing rotations (RX, RY), that are causing tilt signal in the Stage 1 horizontal seismometers, that couple to X and Y as we blend at 45 mHZ, and then shows up into the cavity signal.
The problem was mostly visible on the BS unit. We convinced ourself that Z to tilt was the problem by moving Stage 1 in high blend, which very significantly reduced the Mich amplification around 20 mHz (which exist only when the Z sensor correction is ON)
It seems that the excessive Z to tilt coupling in the BS was caused by off centered vertical position sensors (up to 24000counts). We recentered them by applying a HEPI vertical force. The Z to Mich coupling is now much lower. So I guess that the gain of the sensors was affected by the large offsets and thus creating excessive Z to RX and RY couplings.
Comparison with high blend configurations show that there is probably room to further reduce this coupling. We need the measure the Z to RX and RY coupling and apply corrections.
Dave, Jim
To perform some further HWWD testing at ETMY, we have temporarily connected the HWWD RMS analog monitor (BNC output on rear of unit) to a spare PEM channel on its AA chassis. We are reading the channel using the slow IOP DAQ channel. The plot shows 1 minute of full 16Hz data during the recent ETMY in-chamber work. The 1.6 second integration time can be easily seen in the data.
We are using the next to last channel on the PEM AA chassis, this is ADC3, Ch30 (counting from zero).
Recent in-chamber work on ETMY has provided a OSEM PD RMS trip level comparison between the Hardware watchdog (HWWD) and the IOP software watchdog (SWWD).
We have verified that the two systems have very similar trip levels. The SWWD trip level is hardcoded at 110mV. The HWWD level can be modified, but it is running at its default of 110mV.
The plot shows: the PD RMS status for the SWWD (Ch 4, GOOD=1, BAD=0); and the HWWD (Ch 2, GOOD=0, BAD=1). Also shown is the SWWD RMS monitor for the ETMY top stage OSEM, SIDE channel, which is the channel driving the RMS errors.
As can be seen, Ch4 and Ch 2 match each other very well.
Note that the maximum time in error in this plot is only 3 minutes. If the excitation were to extend to 10 minutes the SWWD would have tripped the SEI DACs, and if it were to extend to 20 minutes the HWWD would power down the ISI coil drivers.
Approved work to be done:
After Chamber Vent Following E1400430
1: Disconnect external (air side) ESD cable from feed thru.
2: Install flat surface with Vacuum Foil on it near Flange for a work
surface.
3: Remove ESD feed thru flange Gerardo
4: IF enough cable exist cut the cables from the connector on the inside.
IF not enough cable disconnect cable
disassemble connector then remove connector ends.
5: Crimp new pin on to cables.
6: Verify with SUS which pin is connected to which part of ESD.
7: Make up connector with new pins in proper order D1400177 V2
8: Secure new connector to new feed thru.
9: Install Flange on Vacuum chamber. Gerardo
10: Connect new external cabling to feed thru
11: Ensure no one is near optic!!! High Pot connector ~ 700V DC If it
doesn't pass. Stop and investigate.
12: Make up external cables to field current limiting resistor box.
The last step is at the time and discretion of the Vacuum crew.
Decision flow diagram from E1400472, drawing by D. Coyne
Took dust monitor trends from End-X ahead of the vent. Posted are a 7 day trend for both location #1 and #2 and a 72 hour trend. The first cleaning and cleanroom over BSC9 were turned on 12/16/14.
Here is an estimate of the BRDF for ETMx and ETMy from the recent scattering images we took.
BRDF | Ps (W) | Pinc(W) | |
ETMy | 2.3e-02 | 8.4e-07 | 21 |
ETMx | 2.5e-03 | 8.0e-08 | 19 |
BRDF=Ps/solidAngle/Pinc/cos(theta_s), in W/steradian , as quoted by Hunter Rew in P1400197. Ps is power incident on photodiode, solidAngle is that subtended by the photodiode, Pinc=incident power (here the IR power inside the arm), and theta_s is the scattering angle, which is the angle of the photodiode from normal incidence. SolidAngle-A/L where A is the area of the photo diode and L is its distance from the test mass.
Ps=calibration_factor*Intensity/Exposure, where calibration factor is in (W*microseconds/counts) and is defined by David Feldbaum in LLO alog 12627, intensity is the total pixel counts on the CCD, and exposure is the camera exposure in microseconds.
Pinc is calculated using Dan's calibration of the TMS photodiodes outlined in alog 15431.
A is as given by the camera specs = 1.0209e-05 m^2.
Rick Savage and Joe Gleason helped me get the distance and scattering angle of the camera from the mirror. L is 6.0452m and theta_s is 4 deg for the ETMS. .
The other paramters used are:
UTC Measurement time | Exposure (microsec) | L ((m) | theta_s (deg) | |
ETMy | 14-12-11-03-00-00 | 10000 | 6.0452 | 1 |
ETMx | 14-12-12-02-00-00 | 500000 | 6.0452 | 1 |
Because these images are taken at small angles, its not valid to assume the BRDF is constant, so its not meaningful to integrate the BRDF to get an estimate on total scatter in ppm. I wanted to compare numbers to the ITMs, however I can't because the analogue gain setting was different (1023 not 100) for the ITM pictures. Once ETMy is clean and we have the Y-arm back I will re-measure ETMy and also add numbers for the ITMs.
ITM03 - had a full sheet of FC applied with NO IAS windows, see attached. ITM03 was installed in BSC3.
Thomas V, Elli
The ITMy and ITMx Hartmann wavefront sensors are now aligned to their respective SLEDS.
We took the HWS plates out and centered the SLED beam on the camera using the periscope mirrors and the final mirror before the HWS (pictures of the final alignment on the camera are included).
The ITMx image is a lot dimmer than the ITMy image, however the H1:TCS-ITMX_HWS_SLEDPOWERMON said 5mW whereas H1:TCS-ITMY_HWS_SLEDPOWERMON says 1.8 mW. We were watching to maximise image brightness as we made the adjustments so I don't know why ITMx image is so much dimmer.
This morning, travis and I pulled the FC sheet that we applied to the ETMy yesterday. The patchy smudge mark and the large gooeyish particle that we induced yesterday were apparently picked up by this FC sheet. While there, we tested using the cotton tipped Q-tip on a portion of the ring around the edge of the optic (~1Inch in from bevel edge near the bottom). We used both DI water and also acetone, both chased with ~5 spot drag wiped of acetone using the pressure technique. Upon evaluating neither q-tip+ acetone drags seemed to improve the area since both swipes added to the streaking which the chasing acetone could not fully remove with 5 wipes.
Our cleaning efforts at EndY have focused on the three larger scattering objects on the surace (which were apparently removed) and the ~3" diameter "stain" associated with the thinner central window in a previous layer of First Contact (which we have not been very successful in removing. ) The composite image below includes six images. All were taken by illuminating the lower edge of the central "stain" feature with the green LED flashlight. The two on the left were taken before applying First Contact (note the large scattering objects are still on the surface). The middle two were taken after the first application and removal of First Contact. The two on the right were taken today, after the second application and removal of First Contact. It doesn't appear that we have significantly improved the "stain" feature.
RF Input Power | Peak Height measured with OSA relative to noise floor | Modulation Depth | |
45 MHz | 21.5dBm | 79.2mV | 0.284 |
9 MHz | 17.27dBm | 41.2mV * | 0.205 |
RFAM | RFAM/PM | |
45 MHz | 1.146e-4 | 4.0199e-4 |
9 MHz | 1.486e-3 | 7.233e-3 |
I annotated the scope screenshot from alog 15639 with carrier and sideband frequencies. Just reading off the plot we have
Frequency | Amplitude | Unit | Ratio | Γ |
---|---|---|---|---|
Carrier | –22.0 | dBm | 1 | — |
–9 MHz sideband | –41.0 | dBm | 0.112 | 0.226 |
+9 MHz sideband | –41.5 | dBm | 0.106 | 0.213 |
–45 MHz sideband | –39.0 | dBm | 0.141 | 0.285 |
+45 MHz sideband | –39.5 | dBm | 0.133 | 0.269 |
Taking the average and assuming a 0.5 dB reading error we have Γ = 0.219(12) for the 9 MHz and Γ = 0.277(16) for the 45 MHz sidebands, respectively.
Paul, Mackenzie, Alexa
We measured the RFAM again; this time after the MC (with the PRM misaligned). Paul and Mackenzie had already aligned the beam onto the AC coupled 1811 NewFocus PD on IOT2R (same specs as before). We blocked the auxiliary laser. Again we used a TPS 30324 to measure the DC signal at high impedance, and the Agilent 43958 Spectrum Analyzer to measure the AC signal. We measured 210mV at DC, and
RFAM | RFAM/PM | |
45 MHz | 2.245e-4 | 6.762e-4 |
9 MHz | 1.121e-3 | 5.63e-3 |
The PM represents the modulation depth. We repeated Daniel's calculation but wanted to collect the numbers with the Spectrum Analyzer to reduce the error. So again, we had the aux beam phase locked to the beam on IOT2R. We measured the following:
Freq | Amplitude | Ratio | Mod Depth | |
Beat | 60 MHz | -22.8dBm | 1 | |
+ 45 MHz | 105 MHz | -37.96dBm | 0.174 | 0.348 |
+ 9 MHz | 69 MHz | -43.2dBm | 0.095 | 0.19 |
-9 MHz | 51 MHz | -42.50dBm | 0.104 | 0.208 |
-45 MHz | 14.5 MHz | -38.82dBm | 0.158 | 0.316 |
Taking the average we find. Gamma_9MHz = 0.199 and Gamma_45MHz = 0.332. This seems a bit high given our previous two measurements. I have used RFAM = 2 * (Vsb/Vcar). There is no sqrt this time because we are measuring the amplitudes; whereas the OSA measured the power. The PD has a BW of 200 MHz, but maybe we are approacing the roll-off. We tried locking the beatnote at a lower frequency so that we would not need to worry about the PD's roll off; however, we had trouble getting a clean lock even at 20 MHz which seemed to be fine yesterday. Paul will attach the raw data.
..and here are the data. It seems like we can even pick out sidebands of sidebands with this measurement technique.
The plot attached shows the Mich Out signal:
- in the first box, HEPI Z sensor correction is ON, Stage 1 X abd Y are in low blend, the IPS are off centered. The low frequency amplication is huge.
- in the second box, HEPI Z sensor correction is ON, Stage 1 X abd Y are in high blend, the IPS are still off centered. The low frequency amplication is gone.
- in the third box, HEPI Z sensor correction is ON, Stage 1 X abd Y are in low blend, the IPS are re-centered. Our current understanding/aseumption is that the Z to RX and RY coupling on HEPI has been well reduced.
The latest configuration is likely the best compromize:
- good micro-seism atenuation thanks to the low blend on X and Y
- low vertical to pitch coupling thanks to the Z feedback
- little RZ amplification at the micro-seism thanks to the Z sensor correction to HEPI (that offloads Stage 1 Z drive at the micro-seism)
- amplification acceptable at very low frequency, now that the IPS have been re-centered. We'll try to further improve it.
An ASD plot of the MICH_OUT channel is attached under different configurations. The first (RED) is with no sensor correction on BS, ITMX and ITMY. The second (BLUE) is with X, Y sensor correction signals to all three BSCs. The third (GREEN) is with Z sensor correction to HEPI for the BS chamber, showing the large low frequency amplification. The fourth (BROWN) shows the MICH_OUT with the IPS recentered and same configuration as the third. Tilt-decoupling on HEPI ought to reduce the amplification further.
Z sensor correction has been turned OFF on BS and ITMY. X and Y sensor corrections seem to be working fine and can be left ON.
Could be that I'm missing something but it sounds to me like at least one of the IPS is not working properly (ie broken). They are supposed to be linear to within 0.1% over the full range (+/- 0.05 inches)