I did a quick estimation of the subtraction result. I subtracted the ADC noise and the noisemon noise.
Now I subtract it:
The ADC noise and Noisemon noise are converted to DAC volts (divided by the transfer function of the noisemon and coil driver).
Form the results from 10-200Hz, it seems that the calculated noise is DAC noise.
Attachment 2 is the result: subtracted noises vs. model compared to aLIGO noise.
Attachment 1 shows how the subtraction is done: we subtract noisemon noise from the total noise. (Noisemon noise contains ADC noise) Noisemon noise and ADC noise is neglegible at that frequency.
It seems at low frequency what we see there might still be DAC noise, if not other unknown sources.
I don't agree about this. Doesn;t this ignore the noise of the noisemon circuit (analog readout noise + ADC noise) ? I think you must have a model for than noise in order to infer the DAC noise. Or maybe my pringle suggestion has better SNR?
This is how we calculate the DAC noise spectrum. The unit is V/rtHz.
Noisemon has been installed at L1 for a while. Now we have it on ITMX and ITMY. ITMX was installed first and ITMY was installed on September 11.
Recently, after it was installed at ITMY, we were trying to check the functionality of the circuit - if it measures DAC nosie properly between 20 - 100Hz. When we were doing that, we encountered some strange harmonics of 65Hz in UL channel. It is shown in attachment 6, data from 9/25 ETMY.
We traced back to where it was installed at ETMY, 9/11, and we still see the lines there (attachment 5).
Then we went to check ITMX, since the data was consistent when it was first installed. However, when we use 9/25 data, we see attachment 4. The UL channel measurement is way above the other three channels. Tracing back the dates, we found in ITMX it started 9/10 (attachment 3), comparing to 9/9 (attachment 2) when it was still good.
All the data and scripts are in attachment 1.
Notes (in case you read about noisemon for the first time):
All the plots are
It is suppose to be DAC nosie + Noisemon noise + ADC noise, which DAC noise being dominant between 20 - 100Hz. The purple curves are DAC noise model. The measurements are expected to be close to it between 20Hz and 100Hz.
I brought in the instrument and components for 2um ECDL:
1. SAF Gain chip / SAF1900S / Qty2
2. Grating / GR25-0616 / Qty2
3. 3axis piezo mount / POLARIS-K1S3P / Qty2
4. Lens / 390093-D / Qty2
5/6 Thorlabs small components / F3ES20, F3ESN1P / Qty2 ea
8~13 Machines Metal Components / D1900435, D1900429, D1900433, D1900432, D1900430, D1900434 / Qty 2ea
14~17 McMaster Carr fastners / 92196a192, 92196a110, 92196a079, 92196a081 / Qty 100 ea
18 Temp Controller / TED200C / Qty 2 Note One unit temporary used by 2um PD test setup
19 Laser Current Driver / LDC220C / Qty 2
20 Piezo Driver MDT694B / Qty 2
I entered Crackle lab circa ~11:15. I started some basic lab inventory and started cleaning/organizing stuff. We will use the first optical table (as you enter the lab) because it's the easiest to clear (see below before and after clearing). Some of the cleared items on the table include:
- UHV foil (moved to top left cabinet above the work bench)
- OSEM components for Crackle (?) (moved to top left cabinet above the work bench)
- Various metallic parts/components (moved some in a plastic container to the second drawer from the bottom of the second red tool storage, and others to the second optical table)
- Various screw/screwdriver kits (moved some to work bench right by the electronic storage area and others to the second optical table)
- Power supply and laser diode driver (moved to control/acquisition rack)
I then moved the 1064nm pump Innolight Mephisto 800NE to the clear table, clamped it down, and cleaned/organized the lab a little, which involved:
- Shelve orphan/incomplete PCBs and electronic components from the work bench up to the cabinets.
- Organized some cables by the fume hood.
- Organized other random hardware on the work benches.
I found the Emergency STOP (OMRON STI #A22EM02B) button buried on the fume hood, so I gave it a quick test, and after confirming it worked I wired it to the interlock on the back of the laser controller. Then tested it along with the interlock and verified it's working, but I have yet to solder it nicely (I didn't commit to the wire lengths yet).
Left at ~ 14:45. Noted that we had more cockroaches in the floor at the beginning of the day than 2 um laser sources. Now we are tied.
Attachment 1: Black Diamond (GeSbSe) Lens was mounted on the flexure mount. The flat surface should face to the gain chip. It was aligned on the wipe to be flush with the protrusion.
Attachment 2: Applied glue on the four grooves of each flexure mount.
Attachment 3: The grating was bonded on the mount. The arrow marks were arranged as Paco directed. The mount could not stand by itself. And the screws were placed to stop the grating skating on the mount.
> Temp Controller / TED200C / Qty 2 Note One unit temporary used by 2um PD test setup
I brought the brand new TED200C from QIL to Crackle (Permanent move).
The unit used for 2um PD test setup will stay in QIL (Permanent)
Another Heimann Sensor / Boston Electronics delivered to Paco.
This unit (purchased May 2020/ / Delivered Aug 5th, 2020) has a FZ-Si window on it.
We don't know how it is.
[Paco, Anchal, Ian, Yehonathan]
Today, in preparation for the optical table to come, we vented the big crackle jar using the vent valve near the gauge. We detached the roughing pump and covered the bellows and pump connections with clean aluminum foil. We then proceeded to move several instruments, including some other pumps, a compressor, a couple of power supplies, power cords, the HeNe laser, misc. material blocks, and boxes with bearings and springs into the cage. The next operation required for us to displace the table is to lift the jar from the top and carefully dismantle the Crackle experiment and store it away somewhere.
Questions: where to store mostly?
In an effort to (1) train Jan and Sanjit to use the elog and (2) actually write down some useful info, I'm going to put some highly useful info into the elog. We'll see what happens after that....
The deal: we have a Trillium, an STS-2, a GS-13 and the Ranger Seismometers, and we want to make nifty breakout boxes for each of them. These aren't meant to be sophisticated, they'll just be converter boxes from the many-pin milspec connectors that each of the seismometers has to several BNCs so that we can read out the signals. These will also give us the potential to add active control for things like the mass positioning at some later time. For now however, the basics only.
I suggest buying several boxes which are like Pomona Boxes, but cheaper. Digi-Key has them. I don't know how to link to my search results, so I'll list off the filters I applied / searched for in the Digi-Key catalog:
Hammond Manufacturing, Boxes, Series=1550 (we don't have to go for this series of boxes, but it seems sensible and middle-of-the-line), unpainted, watertight.
Then we have a handy-dandy list of possible sizes of nice little boxes.
The final criteria, which Sanjit is working on, is how big the boxes need to be. Sanjit is taking a look at the pinouts for each seismometer and determining how many BNC connectors we could possibly need for each breakout box. Jan's guess is 8, plus power. So we need a box big enough to comfortably fit that many connectors.
Nanometrics has a couple of seismometers which are cheaper than the T240 which may be of interest to us: better than the Guralp CMG-40T, but cheaper and easier to use than the STS-2.
We made a drawing for a structure hat will hold the maraging blade. The details aren't complete yet. The holes for the clamping will be identified, but the sketch shows the rough idea.
We want to clamp the blade to a structure. The drawing for the clamp will be provided by Ryan (he found it in the dcc.) The structure is consisted of the base and the pillar. Although a monolithic structure is better, it might be to expensive to carve out a big piece of Al block, so Koji suggested that we do it like this. The base will be mounted on the table, and the pillar will be mounted on the base by 4 screws. The height of the pillar is not decided yet. It depends on how big the Al mass block we need to pull down the blade by its weight, and how the mirror for reflecting the beam up will be mounted, but it should be around 6 - 8 inches.
The mass block will be used for mounting the end mirror of the interferometer + a translational stage. This way we can steer the beam with 2 mirrors and adjust the arm length. We will determine the weight, so we can estimate the size of the mass block, assuming we will use Al.
We made a sketch for the weight clamp that will carry the mass block on the end of the blades. This will be done in Solidwork tomorrow.
We plan to load a block of mass under the tip of the blade by using a pair of knife edge pieces so that the rubbing between the mass block and the blade is minimized.
The edge of the blade cannot be too large, or it will be noisy when the blade is driven. On the other hands, if the blade angle is too small (sharper blade), the stress on the blade due to the weight will be too large and cause plastic deformation on the blade, which we don't want. We plan to make it flat ~ 1mm wide, with 120degree open angle.
The yield tensile strength of maraging steel is ~ 1 -2 GPa. With the contact area at the knife edge we can calculate the maximum clamping force.
The width of the edge is ~ 5cm
The thickness of the edge ~ 1mm.
so the maximum force should not exceed ~ 1 GPa x 0.05 m x 0.001 m ~10^4 newton.
We will use spring washers to make sure that we do not tighten the clamps together with too much force and cause plastic deformation on the blade.
We finalized the drawing for blade clamping system. The drawings are posted here and in Crackle ATF Wiki. We will submit the drawings to the machine shop tomorrow.
For each blade, the clamping system will consist of: 1)Steel base, 2)Steel pillar, 3) Steel top clamp, 4) Al knife edge top piece,5)Al knife edge bottom piece,and 6) Al end piece.
1) Steel base x1: The steel base is 3"x3"x0.5" . It has 4 counter sunk holes that allow us to mount the steel pillar on it. It has 3" rails on both sides, so we can mount it on the table. Extra clamps can be used to hold the base on the table.
2) Steel pillar x1: It is 5.5" height with 2"x2" square cross section. There are 4 tapped 1/4-20 holes , 1" in depth, on the bottom for mounting it on the base. There are 2 tapped 3/8 , 1" in depth, on top for clamping two clamps along with the blade.
3) Steel top clamping piece x1, This will clamp the blade on the pillar.
4) Aluminum knife edge, top piece x1,
5) Aluminum knife edge, bottom piece x1: (4&5) The two knife edge pieces will be used for loading the mass block on the maraging blade tip. The explanation is written in this entry.
6) Aluminum end piece that holds the mirror mount on the blade tip x1: We want to have a steerable mirror for the IFO. So we need a mirror mount. The block will hold the mount and the blade tip together through screws. This piece is uploaded in the above entry.
The assembly (without the blade and the mirror mount) is shown below.
We submitted the drawing to the machine shop today. The works should be done before May 23rd.
The base/ pillar/ blade clamp will be made from stainless steel. The knife edge pieces and mirror mount at the blade tip will be made from aluminum.
I ordered opto mechanical mounts for turning the beam vertically. See the details in psl log.
I also orderedspring lock washers and wave washers. There will be used when we clamp the guillotine things for putting the load on the tip of the blade.
The pressure from the clamp should not exceed the yield strength of the maraging steel blade. So the spring lock washer should give us some limits of pressure on the blade. There is no specification about how much pressure it would be, so I ordered two kinds of washer for testing.
It is clear that the fiber situation needs to be improved. Rana says that the way to reduce the fiber's intensity noise is to use a long (5m?) length of fiber inside of the chamber, tied solidly to the stack; as the beam jitter induced intensity noise is a result of the jittering beam coupling into higher order modes. I am working on calculating the attenuation of higher order modes in a single mode fiber as a function of length, as this should indicate how much fiber we would need.
I have also been in email contact with Dan Clark at Stanford, who did some fiber feedthrough work for a seismic platform interferometer. He sought to achieve a design that would be fully compatible with aLIGO standards, and thus considerably more stringent than the requirements for our situation. He got ahold of a metalized polarization maintaining fiber, and soldered it directly to a flange blank, with pigtails on each end. This has the advantage of only having metal-to-metal vacuum seals, so UHV can be achieved. However, he told me that this all lives out of the way, and doesn't need to be touched often.
Our situation differs somewhat, because we occasionally need to work near the flange, and thus have a greater risk of breaking a fiber that is semipermanently mounted to the flange. Additionally, our vacuum requirements are much looser. I think a feedthrough that has female fiber connectors on each side along with patch cables such as the one we're using would be a robust solution. This way, the fiber can be detached from the flange while leaving the coupling intact, if things need to be moved around.
My current thought is that we can make a feedthrough out of something like this Thorlabs mating sleeve, since an assembled feedthrough (like from CeramTech, which may not even be polarization maintaining) is quite expensive.
Thus, the solution could be made of the following things:
In order to bypass the mechanical resonance problems that people have been having with the blades (i.e. they're not good for high BW locking), today we discussed using a stiff PZT mirror in one of the Michelson arms.
In principle, we would be concerned that we get crackle from this PZT element, but the LLO people have done some crackle measurements on the OMC PZTs so that we should have a good upper limit on that component and its good enough ??
Stiff, high BW, PZT actuated mirror mounts have been used for laser locking:
High Voltage Piezo drivers:
We want to avoid gluing magnets at all. So I designed some small plates that will host the magnet in the center, clamped with set screws. Those small plates can then be attached to the breadboard and to the blocks using screws. The plates have some slots where the screws will go in, so that we can adjust thei vertical position.
There are two different versions, one for the breadboard magnets (6 pieces) and one for the block later magnets (4 pieces). I also redesigned the triangular stands that we are using for the vertical magnets: in the bottom side you can see the four tapped holes where the magnet plate will be attached. When we want to install the magnets using the plates, we'll have to remove the two lateral stiffening beams and have the holes machined. Hopefully we can do that quickly at the machine shop.
I also redesigned the wire clamps for the test blades: the hole positons have been corrected to preperly align to the holes in the blades. Here too I added a clamp for the magnet, so no glue anymore.
Orders have been placed for the improved version of the electronics. The basic ideas are described in T1500539 and detailed schematics are available in D1500402.
The drawings of the Crackle2.1 mechanical upgrade are available from LIGO-E1500420-x0. Thanks Eddie!