2017-07-27

• I resolved a couple more data processing bugs and calculated a sweep of the ESD-Sample gap from a distance of .5 mm to 1.5 mm. The resulting data behaves far more like I would expect from a force generated by an electric field, it seems to drop off like distance squared. This is a very strong correlation with a good intuitive explanation, and would suggest that it is prudent to place the ESD as close to the sample as possible.
• I also computed a higher resolution sweep of the gap between the arms of the ESD. It did not resolve the strange behavior at all, so I will investigate coupling into the mode pairs as a possible source.

2017-07-27

• I ran a low resolution sweep of the offset in the arms of the ESD, the space between the end of the arm and base of the opposite combs. The trends are much more subtle and are not coherent across as many of the modes. The lower frequency modes decrease slightly, while the force in the higher frequency modes increase more drastically. This is an interesting parameter, I will definitely run another sweep once I have written code that accounts for the mode pairs. Assuming the apparent trends are physically accurate, this could be a useful parameter because a greater offset gives a greater relative increase to the higher order modes while still leaving a substantial force on the lower order modes that are excited more easily anyway.

2017-08-01

• I completed an improved sweep of the gap between the ESD arms. I resolved some code issues, since it was passing the maximum value not the most extreme, smaller magnitude positive values were being included rather than the strongest force calculation.
• There are still three modes that show unique behavior relative to the others: 14, 19, and 25. Mode 14 is the (2,2), mode 19 is the (2,3) and mode 25 is (3,2).
• Plots of the mode shapes are included for reference. The black rectangle represents the region covered by the ESD.

2017-08-02

• I ran a sweep of the width of the ESD arms. There appears to be a linear relationship across the modes except for mode 25. Mode 25 exhibits a very similar behavior as in the arm gap sweep. I realized that the abrupt change in direction (also noticeable in mode 14) is likely caused by the fact that the force profile is calculated as absolute value, there might be an exponential relationship that gets converted into that shape by the absolute value function. 

I am posting a diagram of the geometric parameters that I swept. The only one not included is the vertical space between the ESD and sample that sweeps perpendicularly out of the image

2017-08-07

• I included the modal mass factors in the code and renormalized my data. The normalization has a noticeable impact, but does not change the general trends of the data
• In fact the impact is not even significant enough to warrant a change in the ideal parameters I picked for the rectangular ESD in my interim report

2017-08-08

• I rotated the ESD and calculated it's modal projections by rotating the data array that MATLAB extracts from COMSOL. I confirmed that this was properly done by plotting the profile and then computed and plotted both the rotated and normal projections.
• The rotated ESD actually increases the force in some of the modes but decreases the forces in others. It markedly improved the force in 7 of the modes: 3, 6, 12, 18, 19, 22, and 26 while being quite weaker in about 4 of the modes: 9, 13, 14, and 15. This suggests that it may actually be useful to rotate the ESD as it excites some of the higher order modes a noticeable amount more. I am including plots of both modal profiles as well as a chart with mode numbers, shapes, and frequencies.

2017-08-09

• I created a plot of the ratio of the force in the optimized design to the force in the original design. The improvement factor is huge, some modes are excited by more than a factor of 100. I took the same ratio keeping the gap between the ESD and the sample constant and it decreased the excitation by almost a factor of 10. Keeping that gap constant, the geometric modifications to the ESD give an improvement factor ranging from almost 2 to almost 4 for most of the modes. Modes 10 and 25 are outliers but in the original geometry they are barely excited at all, so this could easily be a numerical artifact where those modes were excited at a minimum in the original geometry.

2017-08-09

• I compared the triangular geometry to the original geometry and the excitation was only improved in 7 of the of 20 modes. In four of those modes the improvement factors ranged from almost 2 to over 3 while the other modes where only improved by about 25%. The other 13 modes were diminished drastically, 9 of them where less than half as excited. Given more time it may have been interesting to try and optimize the geometry of a triangular drive, but that would easily take the better part of a week. 

2017-08-09

• From the data I have gathered from a variety of MATLAB sweeps, I think that the optimal geometry I can produce has the parameters in the attached image. Neither the original or optimized drawing is to scale. The gap between the arms of the electrodes should be 1.25 mm, the arm width 0.55 mm, the arm length 16 mm, and the offset of the arms 3.5 mm.

• It is also optimal to place the ESD as close to the sample disk as can reasonably be achieved, at around 0.5 mm away. Since the force on the disk scales exponentially with the distance from the ESD, decreasing that gap is the most substantial way to impact the excitation. Decreasing the gap from 1 mm to .5 mm increases the excitation of the modes by approximately a factor of 8.

• From my simulations, the shift in geometry alone still has a useful impact on the excitation. Modes 1 and 3 are the only two modes that are less excited by the new geometry, mode 1 is 10% weaker  and mode 5 is 5% weaker. Modes 5 and 6 are nearly unaffected by the shift, mode 5 is 2% stronger and mode 6 is 5% stronger.  Modes 7, 18 and 19 are outliers, 7 is excited by a factor of 7, 18 by a factor of 4 and 19 by a factor of 17. The rest of the modes are improved by between a factor of 1.5 and 3. For mode numbers, shapes, and frequencies a plot is included.

2017-08-10

• The attached plots compare the new and old geometries with .5 mm and 1 mm sample gaps. They are the same plot on linear and logarithmic axes respectively

2017-08-14

• I did my best to increase the excitation in the higher order modes. By making the ESD narrower (a 6mm electrode overlap) the higher order excitation is improved drastically, by factors of between 10 and 30 for most modes.  I also created a double ESD (see image) that excited the modes by a factor of 3 or more better than the thinner drive. The plotted ratios are relative to the original geometry, but both of these geometries do better than previous geometries by factors of 2 or 3. 
• After a lot of experimentation, I think that there are non-trivial numerical artifacts from the force projection method. I have noticed that in the modes that are almost entirely unchanged by modifications, both the mode and its doublet have equal regions of positive and negative antinodes directly above the ESD force profile. This can be more clearly seen in the attached mode plot, the rectangle represents the region of the ESD. As a result of this, when the mode shape and force profile are multiplied and integrated the resultant force is very small. I expect this does not appear in the lab because the modes could be rotated at a different angle relative to the ESD. I am not sure how to effectively resolve this, perhaps checking other rotations of the mode shapes could be productive though I am unsure how to effectively accomplish this. 

2017-08-15

• It appears to me that the major factor limiting the improvement of the modes that either remain equal or diminish is that the original design was already quite good at exciting those modes. As can be seen in the attached plots, the original design is about as well centered over the 5 modes as a rectangle on the x axis can be. As a result, maintaing a constant potential on the ESD it would be difficult to improve the coupled force without specifically tailoring the force profile to a certain mode.
• In order from left to right, the frequencies of the given modes are 14.2 kHz, 16.2 kHz, 16.3 kHz, 23.8 kHz, and 27.4 kHz.

2017-08-16

• I placed created a very narrow ESD placed along the edge of the sample. The thought behind this is that it will not cross over into any other modes that will cancel out the force. However, it does not appear to couple force into enough of the area of the disk to cause a worthwhile improvement, as can be seen in the plot, more modes lost amplitude than gained and some were worse by as much as a factor of 1000.

2017-08-16

• I created a model with a drive offset in the middle. It improved one of the modes by a factor of 14 or so, but overall, it diminished the vast majority of the modes by as much as a factor of 100. 

2017-08-16

• I created a model with two ESD's, essentially a combination of my previous two attempts with one ESD on the edge and one closer to the center of the disk. This test was quite successful compared to previous trials, the improvement seems to be on an average of a factor of 10. No modes are weakened by this design. I am going to run a sweep adjusting the central ESD and see what placement is best.
• Attached is an overlay of the force profile and all of the modes. Note that this image is very large, and is useful as a digital reference or very large print only.

2017-08-17

• I ran a sweep of the position of the middle ESD to determine the optimal arrangement. From the original geometry I offset the central ESD between -2 mm and 11 mm. From the plots below I conclude that the optimal geometry is the one that is shifted 2 mm to the right of the original design. 
• The first plot is the sweep data as a ratio to the data of the current geometry for all modes. The second plot is the root mean square of the eight high frequency modes that change the most over the course of the sweep, those are modes 9, 11, 13, 14, and 17-20. The frequencies of those modes in order are 9.5kHz, 11 kHz, 14 kHz, 16 kHz, 19 kHz, 20 kHz, 21 kHz, and 23 kHz. There is a very apparent peak at 2 mm which is the driving force behind my conclusion that it is the optimal design. The next two plots are the 2mm shifted design and the original design as ratios to the original geometry. The 2mm shifted geometry is much more consistent than the original design, there is a very noticeable minimum in the original design (improvement by a factor of 2) for the 23 kHz mode that is resolved in the shifted design to a factor of 9.
• The final plot are ratios of the two designs relative to each other. I found this plot useful to convince myself that the 2 mm shifted design was better than the original, particularly in the region above 1.5 kHz.

2017-08-17

• I made a drawing of the Optimal ESD design. The bottom combs (right hand in the rotated image) are set to ground and the 5 arm comb is set to a positive voltage and the 2 arm comb is set to a negative voltage. 

2017-08-18

• With both electrodes driven at a positive voltage, the results are still an improvement over the original design, but by smaller factors, particularly in 3 of the higher frequency modes at around 2 and 3 kHz. With another parametric sweep I may be able to find a better design. The opposite voltage was useful because it could couple force in opposite directions to adjacent anti-nodes with opposing signs. An adjusted configuration could probably be found to interact with anti nodes with the same signs. An alternative option would be to leave the radial position of the more central ESD constant but rotate it relative to the sample by some amount, though this would also require an additional parametric sweep as well as a much larger ESD. 

2017-08-18

• I ran a sweep of the central position in the two ESD setup with both set at the same voltage. There were two designs that maximized excitation by different metrics, the design with a 3 mm shift from the original design maximized excitation overall, but the 20 kHz mode was worse by a bout a factor of 5. The design with a -2 mm shift maximized the high frequency modes, particularly the modes most affected by the shift.
• MATLAB crashed shortly after the sweep so I will have to recreate the RMS plots of the dynamic modes later.

2017-08-18

• We created a prototype of PCB for the ESD design. Unfortunately the orientation of the two combs was flipped, so it will require some creative mounting to get right. The final design had a 6 mm offset between the two combs, .5 mm traces and 1 mm gaps between them The vertical traces are 12 mm long and there is a 3.75 mm gap between the end of the vertical traces and the opposite horizontal one. The ESD will arrive on Tuesday to be installed Wednesday and we will see how the new design works out.

2017-08-23

• Installed ESD Prototype design by taping it to the older design, we then lowered the mount until it was as close as we could reasonably get it. The new PCB lines up when the top of the new PCB is lined up with the last electrode on the old one. The new PCB was slightly too narrow, the mounting holes are very close to the edge of the PCB, this can easily be corrected in later models.
• Installed sample S1600541 into the single sample apparatus
• Roughing pump on at 12:32
• Turbo pump on at 2:28pm

Link to image1.JPG Link to image2.JPG

We set up the model x3tst to acquire at 65kHz four signals coming from the PSL lab:

• X3:TST-BEAT_OUT_DQ: beat note
• X3:TST-ACC_X_OUT_DQ: accelerometer X
• X3:TST-ACC_Y_OUT_DQ: accelerometer Y
• X3:TST-ACC_Z_OUT_DQ: accelerometer Z

Cleaned the chamber in the washing machine at 40m and started 48 baking at 120 C

Some progress on the cleam room: bar fixed to the wall, some more structure built, filters in place. We had to (literally) work around a corner of the low ceiling that we haven't noticed before. More contruction will follow tomorrow. We also had to order some additional parts (more extrusions, brackets, screws, etc...) 

The clean room frame is built and secured to the floor and wall. Panels are being installed on the ceiling and back. Also, the optical table has been leveled.

Ceiling, back and side panels are installed. The air filters have been cabled and connected to the power supply.

Samples #433 (annealed and cleaned) and #438 (as received from Mark Optics) are now with GariLynn for deep cleaning.

Sample #438 was broken during annealing.

Mon May 13 18:37:37 2019

Entered CRIME lab to borrow 4x hair nets and face masks. Can you please advise on what I should order for clean lab equipment? There are more options on techmart than I anticipated. We're in the process of increasing the cleanliness of the SiQ experiment.

Aaron,

There is a buy list of approved clean room supplies posted here https://dcc.ligo.org/LIGO-E1300399. This list is used by designated people to keep clean rooms supplies stock at each site including LIGO labs in Downs, 40m and the CRIME lab. Not sure what lab you are working in and what regulations you have there. Typically we study the list of the approved supplies, figure out what budget can be used for supplies for a particular experiment. Depending on what your project is, you may be able to just take what you need from the existing LIGO stock (I believe there is one for Downs and one for Bridge and 40m) or work with Liz, Bob or Chub on ordering it for your via approved channels.