Notices by gigabecquerel (gigabecquerel@chaos.social)

Here's something fun, who wants to guess what this is?

No correct guesses yet... none even close 😁
Hint: One of these layers is boron coated!

Definitely getting warmer!
Hint: It is not a "counter"

Hint:
It's made to measure one kind of radiation selectively in the presence of another kind of radiation

No correct guess yet.
Here are a few more pictures:

It's a gamma compensated neutron ionisation chamber!
Basically two chambers in one, sharing one electrode. One chamber is coated in boron to make it neutron sensitive, the other isn't and with some clever wiring of both chambers you can make sure the current on the shared electrode is just from neutrons, regardless of the gamma background!

You'll typically find these very close to a reactor core, used for measuring power.

I got myself another granite plate as a christmas gift, and today I finally finished the micrometer stand for it!
It came out nice and rigid, and the knobs add just the right amount of bling 😁

Yes, I know what a parallax error is, but this kind of setup can be useful, too, just because it's more universal.
Sooner or later I'll build another adapter that then keeps the dial gauge exactly vertical to the plate.

Les lab has been a bit quiet lately, and now we know why:
He made a *really* nice machine for growing huuuge KDP crystals and it came out so well!
Can't wait for the first hobbyist to replicate it, I give it 10 more years until we have NIF-Style fusors in every makers basement 😆

https://youtu.be/uSSoSIcXWa0

Hm

So

An AFM / STM isn't *that* hard to build, right?

Dang why does everything have such a high CTE

50 nm per K in Z.... maybe that can be compensated with the right materials to even out... kinda.

Maybe I just build everything out of fused silica and invar

Ohhh I can build it in a way that the CTEs cancel each other out perfectly(ish)

This looks... ok?
Provided I can cut the glass, that V-Groove is going to be fun. I have an idea or two.

Tests to be done!
The Piezo (why does fusion render brass blue??) does X/Y/Z for the actual raster, the micrometer provides rough (maybe too rough?) Z travel and the kinematic coupling between both plates in combination with the right material choices *should* cancel out most of my thermal expansion to keep it all stable.
Piezo - Glass rod - Needle are one replacable assembly.

The basic kinematic coupling is already soooo satisfying to play with!

Hmmmnice.
It works as expected, and the kinematics reduce the mvement by a factor of ~3, so every Division moves the center by ~3 um.
Should be just about ok, meaning that the piezo can do the rest of the Z travel.
Issue is that I now need to constrain the ball on the micrometer, which means that I either have to grind a cup in the micrometer shaft or buy a different micrometer with a rounded tip to take the ball out entirely.

...maybe I should build a dremel tool mount for the lathe.

@ftg This one is an original one from mitutoyo, I think I found it at a flea market?
But there are similar ones on aliexpress for around 5 €, I've ordered a few and will report back!

@ftg They're... ok!
Not great, but for around 5€ a pop you really can't complain.
The grease they're packed with was a bit thick for my liking, so I swapped it for something thinner (the prusa lube that comes with the printers), which revealed some wiggle room and a few rough spots on the threads. Nothing deal breaking at all!
I'm happy with them.

https://de.aliexpress.com/item/32883962660.html?

Bayerisches Regierungsgebäude
Symbolbild

Oh yes

Oh hell yeah

NUCLEAR MERCH 😍

SMH
It's only november and they've already put up christmas trees...

"Oh this should be around 20 mm, the dimension is not critical"

The result: a few 100 nm off.

I bet the next time I actually try to get something to this accuracy it will be way off :|