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projects:stm:log [2025/08/28 15:53] – [Day 2025-08-28 (rahix)] rahix | projects:stm:log [2025/09/30 22:27] (current) – Remove nolink rahix | ||
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====== Lab Notes for the Scanning Tunneling Microscope ====== | ====== Lab Notes for the Scanning Tunneling Microscope ====== | ||
+ | ==== Day 2025-09-20 (rahix) ==== | ||
+ | Modelled more of the as-built of the current STM setup in mechanical CAD so we have a reference model: | ||
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+ | ==== Day 2025-09-07 (rahix) ==== | ||
+ | Took the video capture from yesterday, of the beam bouncing from the STM off a mirror 2.35m away and back to the camera on the STM and ran some analysis on the data. | ||
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+ | Analysis works like this: For each frame, we find the beam center. | ||
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+ | Here is the final figure: | ||
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+ | The most interesting result is the peak highlighted by the red line. The red line marks the theoretical resonance frequency of the vibration isolation system that we had calculated in the past. Seeing a peak right at this frequency sparks a lot of confidence! | ||
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+ | The results are limited up the 15 Hz because of the 30 fps video capture. | ||
+ | ==== Day 2025-09-06 (rahix, q3k, hugo) ==== | ||
+ | Rebuilt the entire experiment to clean up the space and install some shelving. | ||
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+ | Set up the laser again to make some more measurements of the beam. The following pictures show the beam at different distances. Left to right: 50mm, 100mm, 200mm, 400mm. | ||
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+ | The size change derived from the FWHM in these pictures would be about 0.6mrad, but this is most likely not at all a dependable result. | ||
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+ | Set up the laser to bounce off a mirror 2.35m away and back onto the STM vibration isolated mount. | ||
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+ | Turned on the STM again and managed to get (very very unstable) tunneling. | ||
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+ | We noticed that the vibration isolation is bouncing around a lot more after the rebuild. It seems this is caused by it now standing on a different part of the table that is not rigidly fastened to the table frame. | ||
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+ | Here is an overview of the current status of the experiment after it was rebuilt: | ||
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+ | * Oscilloscope | ||
+ | * Yellow: Z displacement (control variable, this is the " | ||
+ | * Pink: Tunneling current scaled to 0-5V | ||
+ | * Blue: X displacement output | ||
+ | * Green: X displacement input | ||
+ | * Multimeter (set to DC voltage | ||
+ | * Setpoint current ('' | ||
+ | * Laptop | ||
+ | * Connect white USB cable from the Raspberry Pi Pico | ||
+ | * Temperature Measurement using '' | ||
+ | * Red Pitaya (not currently running) | ||
+ | * Can also measure the Z displacement ('' | ||
+ | * And output the X displacement ('' | ||
+ | ==== Day 2025-09-05 (rahix) ==== | ||
+ | Set up the beam camera for a test whether this whole plan of using the camera for interferometry will work. Pointed the bare cheapo laser diode at it. | ||
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+ | Configuring the camera is very odd — it seems you cannot directly set the exposure. | ||
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+ | Analyzing this image for beam quality, using '' | ||
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+ | Please keep in mind that the sensor size is not precisely known as of right now so the absolute measurements in the image above are probably off by up to 20%. | ||
==== Day 2025-08-28 (rahix) ==== | ==== Day 2025-08-28 (rahix) ==== | ||
Performed a study of the dimensions involved in our system based on some yet-to-be-confirmed assumptions. | Performed a study of the dimensions involved in our system based on some yet-to-be-confirmed assumptions. | ||
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Played a bit more with the [[https:// | Played a bit more with the [[https:// | ||
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Calculated the damping behavior of our setup: | Calculated the damping behavior of our setup: | ||
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EMI Box: | EMI Box: | ||
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Removed the formwork from the conrete block we poured on friday. | Removed the formwork from the conrete block we poured on friday. | ||
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* Lessons learned: | * Lessons learned: | ||
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Poured a concrete weight for the vibration isolation system: | Poured a concrete weight for the vibration isolation system: | ||
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* Lessons learned: | * Lessons learned: |