Time For Another Science Post! As Usual, You Can Read More About Fusion Reactors Under My #fusion Tag!

Time for another science post! As usual, you can read more about fusion reactors under my #fusion tag! Let’s talk about…

Tokamaks vs Stellarators!

These devices work on the same general principle: take a very hot plasma, and confine it in a loop using powerful magnets. Heat up the plasma enough and it starts to fuse, then harvest the resulting neutrons to generate electricity. But there’s a catch!

You can’t just have the plasma move around in a circle. If you did that, negative and positive particles would drift in opposite directions, collide with the walls of the chamber, and fizzle out. Instead, you need to get everything moving in a helix.

The difference between a stellarator and a tokamak lies in how they generate that helix.

Tokamaks

This is a tokamak! The vast majority of fusion reactors out there use this design. They work by having a torus (donut-shaped) plasma, with spiraling magnetic fields traveling through it. Within the toroidal plasma, particles follow the helical field lines.

The way you generate this helical field is pretty dang clever. What you do is take two perpendicular magnetic fields — one poloidal (looping in and out of the donut hole), and one toroidal (around the donut in a circle) — and add them together. The resulting combined field is a helix!

The toroidal field is “easiest” to generate. You have a series of powerful magnets that form a ring around the torus. They create a powerful magnetic field in the toroidal direction.

The poloidal field is trickier. For that one, you use a big transformer coil that sits in the middle of the “donut hole.” By ramping up the current in the transformer, you induce a corresponding current within the plasma itself. That plasma current in turn produces its own magnetic field, in the poloidal direction. Toroidal + poloidal = helical.

Stellarators

This is a stellarator! Or rather, one kind of stellarator. Rather than having a torus-shaped plasma with a helical magnetic field running through it, you just make the plasma itself into a helix! You use toroidal magnets (weird blue shapes above) to contain it and drive it along, without the need to generate any plasma current at all. This results in some incredibly wacky geometries!

So which is better?

That’s not an easy question to answer. Let’s compare pros and cons.

Tokamak pros:

Simple geometry, symmetric all around.

Design is forgiving to small errors.

We’ve been building them for 50 years and have gotten pretty good at it.

Every toroidal magnet is identical. Manufacturing the machine is relatively cheap.

Extremely dense plasma that produces a ton of energy.

Tokamak cons:

Plasma current induced by a transformer is inherently transient. If you want to run “steady state” (I.e. for more than 30 seconds), you need to have other ways of keeping that current going. This is doable with various techniques called “current drive,” but it’s tricky. KSTAR and EAST are two tokamaks that are very good at this.

If the plasma collides with the walls of the machine, the entire plasma current gets dumped into one spot. You get what’s called a “halo current,” where several mega amps of electricity blast through an area maybe 10 centimeters wide in a few milliseconds. This is called a “disruption event.” They happen a lot, and they give the machine a hell of a beating.

Stellarator pros:

No need for plasma current! This means you can just run steady state pretty much indefinitely.

No plasma current means that disruptions are relatively gentle, when they happen at all.

Stellarator cons:

As opposed to a tokamak, there are a lot of potential stellarator configurations. Before modern computers, trying to calculate a good stellarator magnet geometry was all but impossible.

They are extremely difficult and expensive to build. Every magnet is unique, and the Seussian vacuum chamber itself is a nightmare to engineer.

Stellarator plasmas are generally colder, and not as dense.

Given how difficult they’ve been to design, we just haven’t built many stellarators. Stellarator research is 30 years behind tokamak research.

So which is best? Nobody really knows! Judging by the trends in research, the first fusion power plant will almost certainly be a tokamak. But hey, it’s possible that eventually, stellarators will become the industry standard.

And now to finish it off, here are some pictures inside the two biggest stellarators in the world: LHD (the Large Helical Device) in Japan, and Wendelstein 7-X in Germany! They are confusing and hard to look at, and have very different geometries.

Here’s W7-X:

And here’s LHD:

opinion on crispr/cas9 + favorite application of it?

Oughhhh it has literally been so long since I read up on CRISPR. I used to have a much more detailed understanding of the technique, but I don't really deal with genetics on much more than surface level these days, so I'm very behind on the state of that field.

Generally speaking, I think it's a great tool... for now. So far I haven't heard of any major issues with it; scientists can add or remove any section of a cell's genome with little to no additional complications observed. It's admittedly pretty ingenious and has catapulted the entire field of genetics forward by decades (if not centuries). But let's not forget that CRISPR is really one of our earliest direct genetic engineering tools! As time progresses we're bound to discover and/or invent far more sophisticated and even safer methods of genetic tinkering.

btw I know ppl on this site go on abt mutuals but if you are someone that shows up in my notes regularly who I don’t follow, I do notice and I am fond of you and if you reblog something from me I do think “YES I have pleased the follower with good taste”

here are the correct answers!

(stolen from xkcd of course)

Reasons Discord's New Mobile Layout Update is Bad

The reply function is redundant, as most people are used to just holding down and tapping the reply option at the top. If they're going to change it, they shouldn't have gotten rid of the member list for this functionally bad option. It also doesnt line up with any other platform in terms of swipe direction.

The member list is gone from easy viewing

It doesnt auto open your last group chat/DM making multiple simultaneous conversations far more difficult and longer

It's already broken my app once (Locked all channels including other servers' to one channel. I could not access anything except that and my DMs.)

You can not see images that have been pinned in the pins tab.

The search function was fine before. Where did your before, during and after date search go??

All of Discord's individuality is disappearing.

Getting used to a mobile format actually impedes usage of the desktop format and likely discourages people from multiplatforming discord because theyre so used to the "intuitiveness" of the new "tailored for mobile" experience

There is no way to CHANGE IT BACK. This is like Tumblr rolling out Tumblr Live without any Disable button At All.

Why are they marketing midnight mode as Something fucking ENTIRELY new??? It has always been a feature on Android as the AMOLED theme???????

If you, too, dislike the theme, head to settings (you can double tap your account picture) and go to Appearance, scroll to New Layout and Send Feedback.

Overall, what they've done is disorientate every single current user on discord, and you cannot avoid it unless you've not updated to the latest discord because this is not an update. It is a feature that has already been on the latest update and is being slowly rolled out, like Tumblr Polls.

Good Luck, and may we send as much feedback as possible and have them make it optional or at the least, revert it. I've already sent in at least seven complaints to discord, commented on their instagram post about the layout and I'm about one star review it on google play and app store.

This isnt just the appearance and vibes being off like the new (ish) app icon, this is a matter of functionality.

Stepping on your