||Mon Jul 2 12:29:01 2018
||Koji||Electronics||Characterization||Impedances of individual components (3IFO EOM)|
The impedances of the individual components from the 3IFO EOM (before modification) were tested.
Each component was modeled by LISO. The LISO model (in PDF and txt) are attached at the end of the entry.
There are three inductors taken from the EOM unit. They showed the Q ranging from 150~300.
Their impedances are compared with the coil taken from the 9MHz port of the spare EOM (=current LHO EOM).
The inductance of the 8.7MHz inductor indicated higher L but still higher Q.
Todd made a replica of the 45.3MHz coil. He used a silver plated wire and it actually showed highest Q of ~400.
The crystal capacitances were measured by attaching a test rig on the DB15 connector of the crystal housing. The rig was calibrated such that the impedances of the attched components on the rig were measured. They showed somewhat similar feature with parasitic resonances at ~50MHz. Above this frequnecy the capacitance went down (i.e. Abs(Z) went up). This indicates there are stray series LCR in pararrel to the crystal. Not sure what is the cause of this.
The central (24.1MHz) port showed smaller capacitance. This probably means the plates for the central port is smaller. Not sure the actual dimensions of the plates for this unit.
||Wed Jul 4 18:30:51 2018
||Koji||Electronics||Characterization||EOM circuit models|
The circuit models for the 3IFO EOM (before mods) were made using LISO.
Then the modification plan was made to make it a new LLO EOM.
Impedance data, LISO model, Mathematica files are zipped and attached at the end.
||Thu Jul 26 20:57:07 2018
||Koji||Electronics||Characterization||9MHz port tuned impedance|
The 9MHz port was tuned and the impedance was measured.
||Tue Aug 7 15:43:12 2018
||Koji||Electronics||Characterization||New LLO EOM stuffed|
[Rich, Dean, Koji]
Stuffed all inductors for the new LLO EOM. As the impedances were sensitive to the positions of the inductors in the housing, they were glued with a glue gun.
Also the lid of the housing significantly change the stray capacitance and lowers the resonant frequency (meaning lowers the Q too), we decided to tune the matching circuit without the lid.
The attached plots show the measured impedances. They all look well tuned and matched. We will prepare and perform the optical measurement at the 40m.
||Thu Aug 9 11:24:29 2018
||Koji||General||Characterization||Modulation Index Test Setup at 40m Lab|
The impedances of the new LLO EOM were measured with the beat note setup at the 40m PSL (as described in the previous ELOG entry.
At the target frequencies (9.1MHz, 24.1MHz, 45.5MHz, 118.3MHz), the modulation responses were (0.09, 2.9e-3, 0.053, 0.021) rad/V.
This corresponds to the requirement for the driving power as follows.
required (LHO) [rad]
||Wed Aug 29 11:06:30 2018
||Koji||General||General||RF AM RIN and dBc conversion|
0. If you have an RF signal whose waveform is , the amplitude is constant and 1.
1. If the waveform , the amplitude has the DC value of 1 and AM with the amplitude of 0.1 (i.e. swing is from 0.9 to 1.1). Therefore the RMS RIN of this signal is 0.1/1/Sqrt(2).
2. The above waveform can be expanded by the exponentials.
Therefore the sideband carrier ratio R is 0.025/0.5 = 0.05. This corresponds to 20 log10(0.05) = -26dBc
In total, we get the relationship of dBc and RIN as , or R = RIN/sqrt(2)
||Sun Sep 23 19:42:21 2018
||Koji||Optics||General||Montecarlo simulation of the phase difference between P and S pols for a modeled HR mirror|
With Gautam's help, I ran a coating design code for an HR mirror with the standard quarter-wave design. The design used here has 17 pairs of lambda/4 layers of SiO2 and Ta2O5 (=34 layers) with the fused silica as the substrate to realize the transmission of tens of ppm. At the AOI (angle of incidence) of 4 deg (=nominal angle for the aLIGO OMC), there is no significant change in the reflectivity (transmissivity). With 95% of the case, the phase difference at the AOI of 4 deg is smaller than 0.02 deg for given 1% fluctuation (normal distribution) of the layer design and the refractive indeces of the materials. Considering the number of the OMC mirrors (i.e. 4), the total phase shift between P and S pols is less than 0.08 deg. This makes P and S resonances matched well within 1/10 of the cavity resonant width (360/F=0.9deg, F: Finesse=400).
Of course, we don't know how much layer-thickness fluctuation we actually have. Therefore, we should check the actual cavity resonance center of the OMC cavity for the polarizations.
Attachment 1 shows the complex reflectivity of the mirror for P and S pols between AOIs of 0 deg and 45 deg. Below 30 deg there is no significant difference. (We need to look at the transmission and the phase difference)
Attachment 2 shows the power transmissivity of the mirror for P and S pols between AOIs of 0 deg and 45 deg. For the purpose to check the robustness of the reflectivity, random fluctuations (normal distribution, sigma = 1%) were applied to the thicknesses of each layer, and the refractive indices of Silica and Tantala. The blue and red bands show the regions that the 90% of the samples fell in for P and S pols, respectively. There are median curves on the plot, but they are not well visible as they match with the ideal case. This figure indicates that the model coating well represents the mirror with the transmissivity better than 70ppm.
Attachment 3 shows the phase difference of the mirror complex reflectivity for P and S pols between AOIs of 0deg and 45deg. In the ideal case, the phase difference at the AOI of 4deg is 1x10-5 deg. The Monte-Carlo test shows that the range of the phase for 90% of the case fell into the range between 5x10-4 deg and 0.02 deg. The median was turned to be 5x10-3 deg.
Attachment 4 shows the histogram of the phase difference at the AOI of 4deg. The phase difference tends to concentrate at the side of the smaller angle.
||Thu Jan 10 20:42:54 2019
||Koji||Optics||Characterization||FSR / HOM Test of OMC SN002|
OMC SN002 = Former LHO OMC which CM1 was destroyed by the lock loss pulse in 2016. This OMC needs to be optically tested before storage.
The test items:
- [done] FSR measurement with offset PDH locking (FM->AM conversion)
- [done] FSR/finesse measurement with the EOM RFAM injection
- [done] TMS measurement with input miaslignment and the trans RFPD misalignment: with no PZT offset
- [done] TMS measurement with input miaslignment and the trans RFPD misalignment: with PZT offsets
- PZT response
- Mirror cleaning
- Power budget
- Diode alignment: shim height
- PD/QPD alignment
||Thu Jan 10 20:45:00 2019
||Koji||Optics||Characterization||PZT test cable|
As OMC SN002 already has the PZTs connected to the Mighty-Mouse connector, a test cable with a female mighty-mouse connector was made.
A small imperfection: When the cable was inserted to the connector shell, I forgot to mirror the pin out. Therefore the color and pin number do not match.
||Sat Jan 12 22:49:11 2019
||Koji||Optics||Characterization||PM-SM patch cable mode cleaning effect|
Mode cleaning capability of an optical fiber was measured. The conclusion is that the leakage of the non-fiber mode to the fiber output is insignificant and also practically negligible.
The tested fiber was Thorlabs 5-m Polarization Maintaining Single-Mode fiber (P3-1064PM-FC-5, PM Patch Cable, PANDA, 1064 nm, FC/APC, 5m).
The output mode cleaner was used as a mode analyzer. The fiber input was aligned and the misaligned so that the amount of higher order mode for the fiber is changed. The fiber output has been mode matched to an output mode cleaner. Therefore excess mode mismatch when the fiber input was misaligned, was accounted as the leakage higher order mode.
For each alignment state, the OMC transmission (in V), the OMC reflection (in V), and the OMC reflection with the OMC unlocked were measured. The voltages were measured with a digital multimeter (non-portable unit). With the fiber input beam aligned to the fiber, the fiber input and output powers were measured with a power meter.
With the input beam aligned
- Fiber input: 52.5 +/- 0.2 [mW]
- Fiber output: 35.5 +/- 0.2 [mW] (~68% coupling)
- Reflection PD offset: -0.00677 +/- 0.00001 [V]
- Refl PD reading with the OMC unlocked: 6.32 +/- 0.01 [V]
- Refl PD reading with the OMC locked: 0.133 +/- 0.002 [V]
- OMC Trans PD with the OMC locked: -1.72 +/- 0.01 [V]
With the input beam misaligned
- Refl PD reading with the OMC unlocked: 3.63 +/- 0.01 [V]
- Refl PD reading with the OMC locked: 0.0752 +/- 0.001 [V]
- OMC Trans PD with the OMC locked: -1.00 +/- 0.01 [V]
The naive mode matching was 0.9779 +/- 0.0003 and 0.9775 +/- 0.0003 without and with misalignment. We initially had roughly 17mW of non-fiber mode incident. And it was increased by roughly 15mW. For the misaligned case, the amount of the OMC-matched carrier was also reduced due to the misalignment. So the actual fiber mode cleaning effect needs more careful quantitative analysis.
The power budget at each part of the setup was modeled as shown in Attachment 1. The blue numbers are the measured values.
The factor a is the ratio of the leakage non-fiber mode into the fiber transmission.
The factor (1-b) is the mode matching of the fiber mode into the OMC mode.
With the calibration between the refl PD and the power meter measurement,
The solution of the equations is
So, the leakage of the non-fiber mode to the fiber output is insignificant. Moreover, the number is practically negligible because the mismatching between the fiber and OMC modes is of the order of percent and dominated by the aberration of the collimator (i.e. the OMC reflection looks like concentric higher-order LG modes) with the order of 1~2%.
||Fri Feb 1 12:52:12 2019
||Koji||Mechanics||General||PZT deformation simulation|
A simple COMSOL simulation was run to see how the PZT deforms as the voltage applied.
Use the geometry of the ring PZT which is used in the OMCs - NAC2124 (OD 15mm, ID 9mm, H 2mm)
The material is PZT-5H (https://bostonpiezooptics.com/ceramic-materials-pzt) which is predefined in COMSOL and somewhat similar to the one used in NAC2124 (NCE51F - http://www.noliac.com/products/materials/nce51f/)
The bottom surface of the ring was electrically grounded (0V), and mechanically fixed.
Applied 100V between the top and bottom.
||Sat Feb 2 16:17:13 2019
||Koji||Optics||Characterization||Summary: OMC(001) HOM structure recalculation|
Each peak of the transfer function measurement was fitted again with a complex function:
History: Measurement date 2013/5/31, Installed to L1 2013/6/10~
||Sat Feb 2 20:03:19 2019
||Koji||Optics||Characterization||Summary: OMC(002) HOM structure recalculation (before mirror replacement)|
History: Measurement date 2013/10/11, Installed to L1 2013/XX
||Sat Feb 2 20:28:21 2019
||Koji||Optics||Characterization||Summary: OMC(003) HOM structure recalculation|
History: Measurement date 2014/7/5, Stored for I1, Installed to H1 2016/8 upon damage on 002
||Sat Feb 2 20:35:02 2019
||Koji||Optics||Characterization|| Summary: OMC(002) HOM structure recalculation (after mirror replacement) |
OMC (002) after repair
History:Mirror replacement after the damage at H1. Measurement date 2019/1/10
||Tue Mar 19 17:30:25 2019
||Koji||General||Characterization||OMC (002) Test items|
OMC #002 Optical tests
- FSR measurement (done, 2019/1/8-9, 2019/4/1)
- TMS measurement (done, 2019/1/9)
- TMS measurement (with DC voltage on PZTs) (done, 2019/1/10)
- Cleaning (done, 2019/3/19)
- Power Budget (done, 2019/3/19, 2019/4/1)
- PZT DC response (done, 2019/3/27)
- PZT AC response (done, 2019/3/27)
- QPD alignment (done, 2019/4/5)
- DCPD alignment (done, 2019/4/4)
- Beam quality check (done, 2019/4/4)
(Cabling / Wiring)
- (Attaching cable/mass platforms)
- (PZT cabling)
- (DCPD cabling)
- (QPD cabling)
(Packing / Shipping)
||Thu Mar 28 16:36:52 2019
||Koji||Mechanics||Characterization||OMC(002) PZT characterization |
As performed in the ELOG 202, the PZTs of the OMC 002 were tested.
DC response was measured by sweeping each PZT with 0-150V triangular voltage at 11Hz. Acquire 0.2sec of the tie series using an oscilloscope to get the PDH error, cavity transmission, and the sweep signal.
The voltage where the tranmission peaks were observed were fitted were recorded. One fringe corresponds to the displacement of 532nm. So the displacement and the applied volatagewere fitted witha linear function.
This gave the PZT response for PZT1 and PZT2 to be 14.9nm/V and 14.4nm/V.
AC response was measured with SR785. The PZT was shaken with 1~50mVpp signal with the DC offset of 5V while the OMC was locked with the feedback to the laser fast PZT. The transfer function from the applied PZT voltage to the servo output were measured. The closed loop TF was also measured to remove the effect of the servo control. The DC levels of the responses were calibrated using the values above.
||Thu Apr 4 20:07:39 2019
== Office Depot ==
Really Useful Box 9L x 6 (delivered)
Really Useful Box 17L x 5 (ordered 4/4)
P-TOUCH tape (6mm, 9mm, 12mmx2, 18mm) (ordered 4/4)
== Digikey ==
9V AC Adapter (- inside, 1.3A) for P-TOUCH (ordered 4/4)
12V AC Adapter (+ inside, 1A) for Cameras (ordered 4/4)
== VWR ==
Mask KIMBERLY CLARK "KIMTECH Pure M3" ISO CLASS 3 (ordered 4/4)
||Fri Apr 5 01:07:18 2019
||Koji||Optics||Characterization||OMC(002): transmitted beam images|
There was a concern that the transmission from CM1 has additional fringes. The shape of the transmitted beams from CM1, CM2, and FM2 (main) werecaptured with WinCamD.
Indeed CM1 and CM2 have the fringes, but it does not exist in the main transmission. So it seems that the fringes are associated with the curved mirrors. But how???
||Fri Apr 5 01:08:17 2019
||Koji||Optics||Characterization||OMC(002): DCPD / QPD alignment|
The beam height in the cavity became totally different from the previous one and the shims needed to be much thicker than before. This is probably because of the alignment of the newly-glue curved mirror.
As the beam height is 2~2.5mm higher, two shims need to be stacked. The preliminary check of the heights using the alignment disks (dummy PDs) suggested the following combinations.
QPD1(SHORT) D1201467-03 (SN 007) + D1201467-03 (SN 008) (2.0 mm + 2.0 mm = 4 mm)
QPD2(LONG) D1201467-01 (SN 001) + D1201467-01 (SN 002) (1.5 mm + 1.5 mm = 3 mm)
DCPD1(TRANS) D1201467-02 (SN 006) + D1201467-03 (SN 005) (1.75mm + 2.0 mm = 3.75 mm)
DCPD2(REFL) D1201467-02 (SN 002) + D1201467-03 (SN 006) (1.75mm + 2.0 mm = 3.75 mm)
This resulted that the fixing button head socket screws for the PD housings to be replaced from 5/16" to 7/16". Stephen kept CLASS A spare screws from Jeff's time.
For the DCPD alignment, a cap-removed Excelitas 3mm InGaAs PD is used. -> This needs to be returned to the PD stock next time.
- DCPD1 was aligned using the zoomed CCD image (Attachment 1). Once the beam is aligned, the angle was tweaked to have the reflection nicely dumped by the glass beam dump (Attachment 2).
- DCPD2 was aligned too. (Attachment 2/3)
- The two housings were fastened by a torque wrench at 2 inch lb.
Continue with the QPDs. The QPD amp was already set.
The cable of the CCD monitor has a problem -> need to check what's wrong
The servo box probably have large offset at the output stage or somewhere (but not input stages).
||Fri Apr 5 20:50:54 2019
||Koji||Optics||Characterization||OMC(002): QPD alignment|
QPD# QPD1 QPD2
Housing# #004 #008
Diode# #44 #46
Shim (see OMC ELOG 323)
Power Incident 252.3 uW 266.0 uW
Sum Out 174.2 mV 176.0 mV +0.3
Vertical Out + 4.7 mV +19.0 mV +0.2
Horizontal Out -16.1 mV - 8.0 mV +0.0
SEG1 -52.4 mV -53. mV -0.1
SEG2 -37.6 mV -47. mV -0.1
SEG3 -41.8 mV -34. mV -0.1
SEG4 -43.7 mV -36. mV -0.1
Spot position X +39 um +15. um (positive = more power on SEG1 and SEG4)
Spot position Y - 8.1 um -56. um (positive = more power on SEG3 and SEG4)
Responsivity[A/W] 0.69 0.66
Q.E. 0.80 0.77
Arrangement of the segments
View from the beam
/ 2 | 1 X
\ 3 | 4 /
I(w,x,y) = Exp[-2 (x^2 + y^2)/w^2]/(Pi w^2/2)
(SEG_A+SEG_B-SEG_C-SEG_D)/(SEG_A+SEG_B+SEG_C+SEG_D) = Erf[sqrt(2) d/w]
d: distance of the spot from the center
w: beam width
||Fri Apr 5 23:30:20 2019
||Koji||General||General||OMC (002) repair completed|
OMC(002) repair completed
When the cable harness of OMC(004) is going to be assembled, the cable harness of OMC(002) will be replaced with the PEEK one. Otherwise, the work has been done.
Note that there are no DCPDs installed to the unit. (Each site has two in the OMC and two more as the spares)
More photos: https://photos.app.goo.gl/XdU1NPcmaXhATMXw6
||Wed Apr 10 19:22:24 2019
||Koji||General||General||OMC(004): preparation for the PZT subassembly bonding |
Preparation for the PZT subassembly bonding (Section 6.2 and 7.3 of T1500060 (aLIGO OMC optical testing procedure)
- Gluing fixture (Qty 4)
- Silica sphere powder
- Electric scale
- Toaster oven for epoxy mixture qualification
- M prisms
- C prisms
- Noliac PZTs
- Cleaning tools (forceps, tweezers)
- Bonding kits (copper wires, steering sticks)
- Thorlabs BA-2 bases Qty2
- Razor blades
||Thu Apr 11 12:15:31 2019
||Koji||Mechanics||Configuration||PZT sub assy mirror orientations|
||Thu Apr 11 21:22:26 2019
||Koji||Mechanics||General||OMC(004): PZT sub-assembly gluing|
The four PZT sub-assemblies were glued in the gluing fixtures. There were two original gluing fixtures and two additional modified fixtures for the in-situ bonding at the repair of OMC(002).
- Firstly, we checked the fitting and arrangements of the components without glue. The component combinations are described in ELOG 329.
- Turned on the oven toaster for the cure test (200F).
- Then prepared EP30-2 mixture (7g EP30-2 + 0.35g glass sphere).
- The test specimen of EP30-2 was baked in the toaster oven. (The result shows perfect curing (no stickyness, no finger print, crisp fracture when bent)
- Applied the bond to the subassemblies.
- FInally the fixtures were put in airbake Oven A. We needed to raise one of the tray with four HSTS balance weights (Attachment 2).
||Thu Apr 11 21:22:58 2019
||Koji||General||General||OMC(004): PZT sub-assembly air baking|
The baking of the PZT subassemblies was more complicated than we initially thought.
The four PZT subassemblies were placed in the air bake oven A. We meant to bake the assemblies with the ramp time of 2.5h, a plateau of 2h at 94degC, and slow ramp down.
The oven controller was started and the temperature has been monitored. The ramping up was ~20% faster than expected (0.57degC/min instead of 0.47degC/min), but at least it was linear and steady.
Once the temperature reached the set temperature (around t=120min), the temperature started oscillating between 74 and 94degC. Stephen's interpretation was that the PID loop of the controller was not on and the controller falled into the dead-bang mode (=sort of bang-bang control).
As the assembly was already exposed to T>70F for more than 2.5hours, it was expected the epoxy cure was done. Our concern was mainly the fast temperature change and associated stress due to thermal expansion, which may cause delamination of the joint. To increase the heat capacity of the load, we decided to introduce more components (suspension balance weights). We also decided to cover the oven with an insulator so that the conductive heat loss was reduced.
However, the controller thought it was already the end of the baking process and turned to stand-by mode (i.e. turned off everything). This started to cause rapid temp drop. So I (Koji) decided to give a manual heat control for mind cooling. When the controller is turned off and on, it gives some heat for ramping up. So the number of heat pulses and the intervals were manually controlled to give the temp drop of ~0.5degC/min. Around t=325, the temperature decay was already slower than 0.5degC/min without heat pulse, so I decided to leave the lab.
We will check the condition of the sub-assemblies tomorrow (Fri) afternoon.
||Sun Apr 14 23:58:49 2019
||Koji||General||General||OMC(004): PZT sub-assembly post air-bake inspection|
(Friday afternoon) We retrieved the PZT sub-assemblies to the clean room.
We started removing the ASSYs from the fixtures. We noticed that some part of the glass and PZT are ripped off from the ASSY and stuck with the fixture. For three ASSYs (except for #9), the effect is minimal. However, ASSY #9 has two large removals on the front surface, and one of the bottom corners got chipped. This #9 is still usable, I believe, but let's avoid to use this unit for the OMC. Individual inspection of the ASSYs is posted in the following entries.
This kind of fracture events was not visible for the past 6 PZT sub-ASSYs. This may indicate a few possibilities:
- More rigorous quality control of EP30-2 was carried out for the PZT ASSY bonding. (The procedure was defined after the past OMC production.) The procedure leads to the strength of the epoxy enhanced.
- During the strong and fast thermal cycling, the glass was exposed to stress, and this might make the glass more prone to fracture.
For the production of the A+ units, we think we can avoid the issues by modifying the fixtures. Also, reliable temperature control/monitor technology should be employed. These improvements should be confirmed with the bonding of spare PZTs and blank 1/2" mirrors before gluing any precious components.
||Mon Apr 15 00:08:32 2019
||Koji||General||General||OMC(004): PZT sub-assembly post air-bake inspection (Sub-assy #7)|
Probably the best glued unit among the four.
Attachment #1: Mounting Block SN001
Attachment #2: PZT-Mounting Block bonding looks completely wet. Excellent.
Attachment #3: The other side of the PZT-Mounting Block bonding. Also looks excellent.
Attachment #4: Overall look.
Attachment #5: The mirror-PZT bonding also look excellent. The mounting block surface has many EP30-2 residue. But they were shaved off later. The center area of the aperture is clear.
Attachment #6: A small fracture of the mirror barrel is visible (at 7 o'clock).
||Mon Apr 15 00:39:04 2019
||Koji||General||General||OMC(004): PZT sub-assembly post air-bake inspection (Sub-assy #8)|
Probably the best glued unit among the four.
Attachment #1: Mounting Block SN007
Attachment #2: Overall look.
Attachment #3: Some fracture on the barrel visible.
Attachment #4: It is visible that a part of the PZT removed. Otherwise, PZT-Mounting Block bonding looks pretty good.
Attachment #5: The other side of the PZT bonding. Looks fine.
Attachment #6: Fractured PZT visible on the fixture parts.
Attachment #7: Fractured glass parts also visible on the fixture parts.
Attachment #8: MIrror bonding looks fine except for the glass chip.
||Mon Apr 15 01:07:30 2019
||Koji||General||General||OMC(004): PZT sub-assembly post air-bake inspection (Sub-assy #9)|
The most fractured unit among four.
Attachment #1: Mounting Block SN017
Attachment #2: Two large removals well visbile. The bottom right corener was chipped.
Attachment #3: Another view of the chipping.
Attachment #4: PZT-mounting block bonding look very good.
Attachment #5: Another view of the PZT-mounting block bonding. Looks very good too.
Attachment #6: Fractures bonded on the fixture.
Attachment #7: Front view. The mirror-PZT bonding look just fine.
||Mon Apr 15 01:23:45 2019
||Koji||General||General||OMC(004): PZT sub-assembly post air-bake inspection (Sub-assy #10) |
Attachment #1: Mounting Block SN021
Attachment #2: PZT-Mounting Block bonding looks just excellent.
Attachment #3: The other side of the PZT-Mounting Block bonding is also excellent.
Attachment #4: The mirror-PZT bonding also look excellent. Some barrel fracture is visible at the lower left of the mirror.
||Tue Apr 16 11:36:36 2019
||Koji||Optics||Characterization||OMC(004): PZT testing for spare OMC|
Attachment 1: Shadow sensor setup for the PZT displacement test
Attachment 2: PZT endurance test. 4 PZTs were shaken at once.
Attachment 3~5: Function generator setup 100Hz, 3.5Vpp 1.75Voffset (meant be displayed for 50Ohm load)
Attachment 6: The above setting yields 7Vpp unipolar signal @Hi-Z load
Attachment 7: The output was monitored with a 1/10 probe with the PZTs connected. This shows 10Vmax 0Vin -> Good. This photo was taken at 17:35.
Attachment 8: The test is going well @9:15 next day. (t=15.7hours = 5.6Mcycles)
Attachment 9: The test went well. The modulation was stopped @15:35. (t=21hours = 7.6Mcycles)
||Tue Apr 16 16:35:09 2019
||Koji||Optics||Configuration||OMC(004): Glass breadboard selection|
D1200105 SN006 was selected as the breadboard for OMC(004).
The reason is the best parallelism among the unused ones.
The attached is the excerpt from T1500060 with the #006 highlighted.
||Tue Apr 16 16:40:26 2019
||Koji||General||Configuration||OMC(004): A Mirror selection|
We are going to use A5 and A14 for FM1 and FM2. (The role of these two can be swapped)
The reason for the selection is the better perpendicularity among the available prisms.
A11 has the best perpendicularity among them. However, the T didn't match with the others. The pair of A5 and A14 has a good matching with small compromise of the perpend.
The attachment is the excerpt from T1500060.
||Tue Apr 16 16:52:36 2019
||Koji||Optics||Configuration||OMC(004): B Mirror selection|
We are going to use B6 for the DCPD BS (BS2), and B1 for the QPD BS (BS3). Their role can not be swapped.
B6 has the best loss among the available ones, while the perpendicularity is not so critical due to the short arm.
B1 has the OK perpendicularity, while the loss is also moderately good.
The attachment is the excerpt from T1500060 with some highlighting.
||Tue Apr 16 17:24:56 2019
||Koji||Optics||Configuration||OMC(004): E Mirror selection|
We are going to use E6, E9, E11, and E14 for BS1, SM1, SM2, and SM3. They (and E18) are all very similar.
The attachment is the excerpt from T1500060 with some highlighting
||Tue Apr 16 21:16:11 2019
||Koji||Optics||Characterization||OMC(004): PZT testing for spare OMC|
After having dug into the past email, it turned out that these wires were the ones already replaced from the original teflonwires. The length of them were confirmed to be ~19" (480mm).
All four PZTs seem to be connected to Teflon coated wires. It needs to be checked if these
fulfill the vacuum compatibility requirements.
||Tue Apr 16 23:11:43 2019
||Koji||General||General||Borrowed items from the other labs|
Apr 16, 2019
Borrowed two laser goggles from the 40m. (Returned Apr 29, 2019)
Borrowed small isopropanol glass bottole from CTN.
Apr 19, 2019
Borrowed from the 40m:
- Universal camera mount
- 50mm CCD lens
- zoom CCD lens (Returned Apr 29, 2019)
- Olympus SP-570UZ (Returned Apr 29, 2019)
- Special Olympus USB Cable (Returned Apr 29, 2019)
||Fri Apr 19 11:34:19 2019
||Koji||Optics|| ||OMC initial alignment and locking|
The spot on CM1 was found displaced by 3.4mm (horiz.) and 3.0mm (vert.) in the upper right direction looking from the face side.
The spot on CM2 was found displaced by 1.2mm (horiz.) and 1.8mm (vert.) in the upper left direction looking from the face side.
The drawing on the left side of the attachment shows the estimated misalignment when we think they all come from the curved mirrors.
As for the yaw misalignment, CM1 and CM2 were 3.9mrad and 5.6mrad rotated (misaligned) in CW, respectively.
As for the pitch misalignment, CM1 and CM2 has 1.7mrad (narrowing) and 3.5mrad (widening), respectively. We have no adjustment for this.
Let's say if this comes from the dusts on the bottom of the prisms, CM1 has ~17um one, and CM2 has ~35um one beneath them. The question is if we can believe this or not? This should be checked with the Newton fringes we can see at the bottom of the prisms.
||Sat Apr 20 00:50:12 2019
||Koji||Optics||Characterization||OMC(004): Spot positions|
Similarly to OMC ELOG 349 the spot positions after the replacement of CM2 were measured (Attachment 1)
Also, the spot positions after the realignment were measured. (Attachment 2)
||Mon Apr 22 19:54:28 2019
||Koji||General|| ||OMC(004): Spot positions at the end of Apr 22nd|
||Wed May 1 15:40:46 2019
||Koji||Optics||Characterization||OMC(004): Spot positions and the scattering|
Tried a few things.
1. Replaced CM1 (PZT ASSY #10=M21+PZT#22+C12) with PZT ASSY #7 (=M1+PZT#13+C13)
We tried PZT ASSY #7 at the beginning and had the spots at almost at the top edge of the curved mirrors. As we found a particle on the bottom of the M1 prism (and removed it), I gave it a try again. Resulting spots are again very high. This results in rejecting PZT ASSY #7 and we set the combination of the PZT ASSYs as #8 (M7+P11+C11) and #10 (M21+P22+C12). This combination nominally gives the spot ~1mm above the center of the curved mirrors.
2. Swapped FM1 and FM2. Now FM1=A5 and FM2=A14.
No significant change of the scattering features on the FMs. The transmitted power was 14.85mW (Ref PD Vin = 3.42V), Reflection PD Vrefl,lock = 54.3mV and Vrefl,unlock = 2.89V (Vin=3.45V), Vrefl,offset = -6.39mV. The incident power was 17.43mW (Vin 3.69V).
==> Coupling 0.979 , OMC transmission 0.939 (This includes 0.6% loss to the QPD path) ...Not so great number
3. Built better camera setups to check the spot position and the scattering from the cavity mirrors.
Now the spot heights are fixed and safe to move the camera up for inches to obtain better views of the mirror faces. The camera was set 15" away from the mirrors with 1.5" height from the beam elevation. This is 0.1rad (~ 5 deg) and Cos(0.1)~0.995 so the distortion (compression) of the view is negligible. (Attachment) The spot photo were taken with the fixed CCD gain, the focus on the glass, and lens aperture F=8.0. Later the focus and aperture were adjusted to have clear view of the scattring points.
The intensity of each scattering was constant at different views. I suppose this is because the scattering is coming from a spot smaller than the wavelength. The bright spots does not show any visible feature on the mirror surfaces when they were inspected with a green flash light.
CM2 has the excellent darkness and we want to keep this spot position. FM1, FM2, and CM1 showed bright scattering.
The spot at CM1 is not well centered on the mirror. And this is the way to avoid this scattering point. So let's think about to move the spot on CM1 by 1.3mm towards the center while the spot on the CM2 is fixed. Note that this is going to be done by the micrometers for CM1 and CM2.
By turning right micrometer of CM1 forward (50um = 5div = 1/10 turn) and the left micrometer of CM2 backward (60um = 6div) moves the spots on FM1, FM2, CM1, and CM2 by (0.43, 0.87, 1.3, 0)mm. This basically moves the spots toward the center of each mirror. Let's give it a try.
||Fri May 3 11:06:28 2019
||Koji||Optics||Characterization||OMC(004): Spot positions and the scattering|
Experiment on 5/1
- CM1 right knob was moved 1div (10um) backward such that the spots were better centered on the mirrors
FM1 (A5): h=-0.2mm -> 0.4mm made the spot much darker but still it has a few scattering spots.
FM2 (A14): h=-0.8mm -> 0.2mm reduced the number of spots from 2 to 1. And it is darker. The remaining spot at the center.
CM1 (C11): h=-1.3mm -> +1.0mm made the spot much darker.
CM2 (C12): h=-0.7mm -> +0.2mm remains dark.
Note: CM1 h=1mm and CM2 h~0mm are good locations. h+ is the good direction to move. Avoid h-.
FM1 and FM2 has the scat spots at the center. Want to go h+ more.
Uniformly go h+ is the good move. => This can be done by rotate CM1 positive => CM1 right knob CCW.
||CM1 right micrometer 1div backward
Improvement of the transmission from 93.9%->95.3%
- Further moved CM1 right knob 0.5div (0.5um) backward such that the spots were moved to h+ directions.
FM1 (A5): h=0.4mm -> 1.1mm (there is only one spot rather than multiple spots)
FM2 (A14): h=0.2mm -> 1.1mm (darker but multiple spots)
CM1 (C11): h=1.0mm -> 1.8mm (brighter but single spot)
CM2 (C12): h=0.2mm -> 1.5mm (dark multiple spots)
||CM1 right micrometer 0.5div backward
Not much improvement of the transmission but kept 95% level.
- Replaced FM1 (A5) with A1 mirror (No photo)
Good news: This did not change the cavity alignment at all.
- Tweaked the CM1 angle
=> A1 mirror does not improve the transmission much.
Next Plan: Use A5 (or something else) as FM2 and see if A14 caused the dominant loss.
||Thu May 9 17:35:07 2019
Notes on the OMC cavity alignment strategy
- x3=1.17 γ + 1.40 δ, x4=1.40 γ + 1.17 δ
- This means that the effect of the two curved mirrors (i.e. gouy phases) are very similar. To move x3 and x4 in common is easy, but to do differentially is not simple.
- 1div of a micrometer is 10um. This corresponds to the angular motion of 0.5mrad (10e-6/20e-3 = 5e-4). ~0.5mm spot motion.
- ~10um displacement of the mirror longitudinal position has infinitesimal effect on the FSR. Just use either micrometer (-x side).
- 1div of micrometer motion is just barely small enough to keep the cavity flashing. => Easier alignment recovery. Larger step causes longer time for the alignment recovery due to the loss of the flashes.
- After micrometer action, the first move should be done by the bottom mirror of the periscope. And this is the correct direction for beam walking.
- If x3 should be moved more than x4, use CM2, and vise versa.
- If you want to move x3 to +x and keep x4 at a certain place, 1) Move CM2 in (+). This moves x3 and x4 but x3>x4. 2) Compensate x4 by turning CM1 in (-). This returnes x4 to the original position (approximately), but leave x3 still moved. Remember the increment is <1div of a micrometer and everytime the cavity alignment is lost, recover it before loosing the flashes.
||Thu May 9 18:10:24 2019
||Koji||Optics||Characterization||OMC(004): Spot position scan / power budget|
(Now the CCD image is captured as a movie and the screen capture is easier!)
Various spot positions on CM1 and CM2 were tried to test how the transmission is dependent on the spot positions. CM1 has a few bright spots while CM2 shows very dark scattering most of the case. Attachment 1 is the example images of one of the best alignment that realized the transmission of ~96%. FM1 and FM2 also showed bright spots. The replacement of the FM mirrors does not improve nor degrade the transmission significantly. The transmission is still sensitive to the spot positions on the alignment. This indicates that the loss is likely to be limited by CM1.
Attachment 2 shows the distribution of the (known) scattering spots on CM1. The bright spots are distributed every ~1mm on the spot height and the beam (with beam radius of .5mmm) can't find a place where there is no prominent spots.
We will be able to examine if the transmission can be improved or not by replacing this CM1 mirror.
||Wed May 15 19:07:53 2019
||Koji||Clean||General||What is this???|
Suddenly something dirty emerged in the lab. What is this? It looks like an insulation foam or similar, but is quite degraded and emits a lot of particulates.
This does not belong to the lab. I don't see piping above this area which shows broken insulation or anything. All the pipes in the room are painted white.
The only possibility is that it comes from the hole between the next lab (CRIME Lab). I found that the A.C. today is much stronger and colder than last week. And there is a positive pressure from CRIME Lab. Maybe the foam was pushed out from the hole due to the differential pressure (or any RF cable action).
||Mon May 20 19:53:17 2019
||Koji||Optics||Configuration||DCPD high power test|
We want to perform a damage test of OMC DCPDs with high power beam. The OMC DCPD is the 3mm InGaAs photodiodes with high quantum efficiency, delivered by Laser Components.
The sites want to know the allowed input power during the OMC scan for beam mode analysis. The nominal bias voltage of the PDs is +12V. Therefore, 30mA of photocurrent with the transimpedance of 400 Ohm is already enough to saturate the circuit. This means that the test is intended to check the damage of the photodiode mainly by the optical power.
The test procedure is as follows:
1. Illuminate the diode with certain optical power.
2. Measure the dark current and dark noise of the PD with no light on it.
3. Check the condition of the PD surface with a digital camera.
4. Repeat 1~3 with larger optical power.
The beam from an NPRO laser is delivered to the photodiode. The maximum power available is 300~400mW. The beam shape was regulated to have the beam radius of ~500um.
- When the PD is exposed to the high power beam, the circuit setup A) is used. This setup is intended to mimic the bias and transimpedance configuration used in the DCPD amp at the site.
- When the dark noise is measured, the circuit setup B) is used. This setup is low noise enough to measure the dark noise (and current) of the PD.
- The test procedure is going to be tested with an Excelitas 3mm InGaAs PD (C30665), and then tested with the high QE PD.
||Wed May 22 07:31:37 2019
||Koji||Optics||Configuration||Camera test (DCPD high power test)|
C30665 (3mm) camera test. The camera was Canon PowerShot G7X MkII. Exposure 1/15s, F 5.6, ISO 125, MF (~the closest), no zoom.
This image was taken before the beam illumination. Will tune the green lighting to have some gradient on the surface so that we can see any deformation of the surface.
||Thu May 23 01:42:46 2019
||Koji||Optics||Characterization||C30665 high power test|
An Excelitas C30665 PD with the cap removed (SN07 in Case H slot #2) was exposed to the beam with the optical power of 1.4mW to 334mW.
After each illumination, the dark current and the dark noise level were tested. Also the photo image of the PD surface was taken each time.
- No significant change of the dark current after each illumination.
- No significant change of the dark noise after each illumination.
- No visible change of the surface observed.
||Thu May 23 23:27:38 2019
||Koji||Optics||Characterization||IGHQEX3000 high power test|
LaserComponents IGHQEX3000 (Cage B2: Serial# B1-23) was exposed to the beam with the optical power from 1.6mW to 332mW.
After each illumination, the dark current and the dark noise level were measured. Also the photo image of the PD surface was taken each time.
- No significant change of the dark current after each illumination.
- No significant change of the dark noise after each illumination.
- No visible change of the surface observed.
(During this dark noise measurement, the current amp gain was set to be 1e8 V/A, instead of 1e7 for the measurements yesterday.)