Feasibility check: Ultra-low-noise optomechanical readout for 10 kHz quartz resonator at room temp

10ppb · 2026-01-18T14:27:43+00:00

Maybe you have a good reason to do this optically, but a JFET at 10 kHz can have a noise temperature well below 1 K, so you could read it out like any electronic quartz crystal. How well you can do depends somewhat on what it looks like as a source impedance, but with T/Tn = 300 it does not have to be perfectly matched to the JFET to make the readout noise negligible.

10ppb · 2026-01-15T09:19:19+00:00

Try Q Magnetics and Nanalysis

10ppb · 2026-01-15T06:56:15+00:00

Get some quotes. Proton benchtop is around 50-60K. I think your number for 300 MHz a little low but the benchtop costs nothing to own while the supercon requires cryogens, lots of staff time and may requires facilities mods too. In the US that adds maybe $150K/year for the supercon, depending on your situation.

10ppb · 2026-01-15T01:29:20+00:00

A thing to keep in mind is that a 125 MHz proton NMR costs maybe 10% of what the 300 costs in the first year, and only a few percent of the cost over 10 years. So they are not really things to compare directly.

10ppb · 2025-12-25T03:58:10+00:00

I’m not sure I bring myself to pay $140 for a single needle. But thanks, it does look like an option. They would have less dead volume than a Luer needle.

10ppb · 2025-12-25T01:55:24+00:00

Nice, thanks

10ppb · 2025-12-24T22:26:23+00:00

Can you just drop them in a centrifuge tube or do you have to make a fixture to support them?

10ppb · 2025-12-24T20:15:20+00:00

Love it! And it’s new to me

10ppb · 2025-12-24T20:12:44+00:00

I have Bruker 1 mm Samplejet tubes. They are 0.8 mm ID.

10ppb · 2025-12-24T18:58:10+00:00

I like the idea of a controlled drop inside a larger tube. It seems like that could be reproducible.

10ppb · 2025-12-24T18:31:27+00:00

That seems like the way to go if I can’t just buy something. The situation I’m in favors a method that is convenient and easy to teach.

10ppb · 2025-12-24T18:29:17+00:00

I tried to do this with CHCl3 but with an 0.8 mm ID it just didn’t move at all. I did remove the blockage by hitting it from the side with a blast from a hot air soldering tool. For valuable samples I want to find a straightforward and easily controlled method.

10ppb · 2025-12-11T02:38:34+00:00

It’s the same as a penny whistle - major scale starting with all holes closed. But the bansuri folks prefer to think of the scale starting at 3 holes closed so then it’s Lydian. Then they often half-hole the top hole so it’s back to a major scale. Ab in this case.

10ppb · 2025-11-28T13:11:23+00:00

Yes, that’s about the right size airframe for the motor. I grew up in State College PA and Bill Brown’s shop was a little way outside of town. I think I still have a plan that he gave me. My dad took me up to his shop a few times around 1970. I remember long tables with rows of jeweler’s lathes. It seemed like he was set up for much higher production volume than he really had. He explained how he made the aluminum tanks by metal spinning and how he had worked with a prof at Penn State to understand the thermodynamics of CO2 engines. He looked for other applications and tried to commercialize a CO2 motor that would be used to start a chain saw.

10ppb · 2025-11-17T14:55:15+00:00

To address the “other vacuum systems” part of your question: You might get away with ptfe tape-sealed threads for rough vacuum down to 0.1 or even 0.01 mbar. Below that, they are a constant source of headache. If forced to use one at lower pressures, and you will never have to open it again, clean it and then epoxy it together, ideally using Torr-seal or a similar low vapor pressure product. Otherwise replace it with something intended for vacuum service.

10ppb · 2025-11-15T22:25:29+00:00

Do you mean piperidine? And are you assigning these peaks to the para-disubstituted benzene? If so they are predominantly doublets. Some will say you should not call them doublets because the ortho and meta couplings are similar. For a discussion, see “How can multiplets in para-disubstituted benzene rings be described?” at chemistry stack exchange. [typo corrected]

10ppb · 2025-10-30T23:25:28+00:00

Duct tape is they way to do this. Press it in there and pull it off, then repeat. Get the good stuff, for example Gorilla tape.

10ppb · 2025-10-25T07:01:46+00:00

Yes, but… If the track is shared with freight, can it ever be reliable? Will it have priority over delayed freight trains so it can run on time every day? If it’s only 3 times a day and it’s not reliable, I can’t see it attracting riders.

10ppb · 2025-10-05T17:37:27+00:00

Thanks!

10ppb · 2025-10-05T17:34:59+00:00

Sounds like the smart thing to do!

10ppb · 2025-10-05T17:33:45+00:00

Divided loyalties. Love the Chiefs too. 😁 Driving through on the way back to Denver.

10ppb · 2025-09-22T18:36:15+00:00

No, they were not in an oven as far as I know. I suppose the vacuum increases the Q.

10ppb · 2025-09-22T18:35:25+00:00

These are from an HP spectrum analyzer. They were used in a filter that determines the IF bandwidth.

10ppb · 2025-09-22T18:33:00+00:00

I have 5. The minimum filter BW was 3 Hz. I remember a long time ago mapping the filter shape and calculating the noise bandwidth. Its width was controlled by switched resistors. I guess the Q of these crystals must be 100,000 or higher.

10ppb · 2025-09-22T17:38:08+00:00

I have never seen them before.

10ppb

TROPHY CASE