When the positrons are at the top, they attract negative charges into the top end-cap. This is called an "image charge". When the positrons are close to the bottom end-cap, the image charge into bottom end-cap. This forms a current, the "image current". The more positrons you have, the larger the image current.

Since the image current (on the order of femtoamperes) has to flow through the large resistor, it is turned into a voltage that can be amplified and measured by cryogenic amplifiers. But it has a second effect: The voltage "back-acts" on the positrons, damping their motion. If you have more positrons in the trap, this damping gets stronger, because each positron experiences the back-action of all other positrons.

In the paper, you can see pictures of the driven axial motion, where you take an RF excitation and sweep the frequency over the resonance, recording the positrons' amplitude as a response. The more positrons you have, the "wider" this resonance, because of the damping effect.

As you reduce the number of positrons by doing a "dip" (making the trap really shallow, hoping that some, but not all, positrons escape), you can see the width getting smaller and smaller in discrete steps. That's how you know you are dealing with individual particles.

I haven't worked on Gabrielse's setup, but I have worked on other, very similar (better, ha!) experiments 10 years ago. I don't see what's so special about this trap, but putting antimatter into it always makes for a nice headline.

This is absolutely not cool.

This is a horrible future to consider.

The more I think about it, the more I come to the conclusion that a society that bans ads is a healthier, more robust society, and I am not alone.

https://news.ycombinator.com/item?id=43595269

Typically, spherical harmonics are introduced as a complex function over spherical coordinates, which makes them much easier to derive, but imo hides their beauty.

The real-valued, cartesian form of regular spherical harmonics is also called "solid harmonics" or "harmonic polynomials", in case you want to dig deeper.

https://idlewords.com/talks/website_obesity.htm

If a doctor even _hints_ there might be cancer, the patient will have a terrible 6 months (with actual, measurable negative health impacts of the added stress). Also, at some uncertainy-level (say, 10% chance of cancer) the doctor _has_ to say something and has to schedule expensive followups to not risk liability, even though in 90% of the cases it is not only unnecessary, but actively harmful to the patients.

When, on average, the cost of the screening + the harm done by a false positive outweighs the benefits of an early detection, you shouldn't do the screening in the first place.

It's a bit more technical. And it has a three-letter acronym. Gotta have a three letter acronym.

For sequence-diagrams, nothing beats https://sequencediagram.org/ (I am not connected with them in any way, just a happy user)

It's mostly broadband noise that can be simulated by simpler methods, but visualizing possible resonance patterns for the low-frequency emissions from the compressor (which typically runs at 20Hz, 40Hz, ..., 120 Hz) would be good to know.

Although I am not sure how the 2d simulation result carries over to the 3d world...

Sadly, it is no longer maintained.

What kind of stack should I use so that tools like Darwin (or just plain old copilot) can be most effective?

It was a race between me placing items on the conveyor belt and them ringing the items up. Oh the embarrassment when they told me the total as I was placing the last item on the conveyor belt.

Or is it because the Penning trap measures "inertial mass" but they really want a measurement of "gravitational mass"? But wouldn't inertial mass fluctuate the same way?

- syntax is really close to PlantUML

- it's rendered in the browser -> immediate feedback

- great autocomplete and syntax-check in the code editor

- great connection between graphic and text (click on element -> jump to relevant line)

- graphical drawing and reordering

- presentation view (fullscreen + keeps actors "sticky" on top)

Especially dragging/dropping actors around is a lot of fun when you try to find the most suitable presentation format for complex diagrams. I'm not aware of any other editor that has this good integration between the code-editor and the visual editor.

It's not open source, but it's been around for free for a long time.