Hacker News Reader

Comment by happyopossum | Hacker News Reader

> Herrmann noted that in previous experiments, neutrons exiting the capsule on one side of the implosion arrived a few picoseconds earlier than did those flying off the opposite way

Let’s all just take a step back here and marvel at this statement. We (science-humans) are capable of building a machine that can detect and quantify picosecond level variances in neutrons traveling in an enclosure. We can do amazing things.

Side note - the lab is just down the road from me, I’m proud of my fellow Livermorons, and continue to hope they keep all those megajoules contained.

View on HN

For context, in wired chip-to-chip communication electronics, femtosecond variations are (statistically) measurable. Picoseconds are rather pedestrian. A 56 Gbaud signal has a single-symbol duration of about 18 picoseconds and perturbations on the order of 1 picosecond are rather large 5.6%.

Not to downplay the achievement of the article or the innovation in fusion physics and engineering in general, just a bit of context for the timescales.

For further context, the fastest oscilioscopes commercially available (Keysight UXR) samples at 256G with 20fs (rms) of jitter. Modern coherent optics runs at over 100GBaud, a picosecond is 1/10th of a symbol period.

MSRP of $1.3 Million US dollars

https://www.eevblog.com/forum/testgear/something-amazing!-ke...

AKA roughly one Brooklyn apartment.

Used a similar scope during my grad school tenure for measuring 200GS/s ADCs. RF electronics is a wonderful field.

In a 5nm semiconductor chip a standard cell inverter (like combinational AND / OR gates) can switch in 5 picoseconds. These things are characterized with at least 2 more significant digits so we feel we know how they respond at the 10's of femtosecond level of precision.

A nice rule of thumb for these kind of timescales (courtesy of a lecture by Grace Hopper) is to consider the speed of light: 1 nanosecond at the speed of light is about 1 foot (300 mm). A picosecond is then 0.3 mm.

Which is also a method to shift light pulses by the shortest of durations! Insert an optical delay line into the setup and by varying the path length, you can delay a light pulse by a tiny amount of time, e.g. for a pump-probe experiment (a pump-probe experiment works like this: first pulse does something to the system ("pump"), second pulse comes a short time later and reads out ("probes") the state of the system at that time. Changing the time delay gives an idea of the dynamics).

Here is a drawing of an optical delay line: https://www.thorlabs.com/images/TabImages/Delay_Line_Kit_D1-...

The part labelled "V-Block" can move along the "translation stage" which changes the length of the optical path by twice this amount. Use the speed of light to calculate which delay the pulse incurred over the distance. You can now send pulse after pulse through your setup while changing the delay by tiny amounts to see how things (e.g. chemical processes) happen on these time scales.

Relevant video for those who haven’t seen the lecture:

https://www.youtube.com/watch?v=9eyFDBPk4Yw

For those questioning the “Livermorons”: I can’t speak directly to that but can say that Naval Aviation uses a similar term for those who elect to stay at NAS Lemoore: “Leemorons”. It’s not a perjorative; the people I’ve talked to use the term affectionately.

In a large enough community, these two (perjorative and affectionate) are not mutually exclusive. c.f. Yankee Doodle, etc

And it's important to note that these developments in sensor technologies can be carried forward to future experiments even if the NIF is ultimately incapable of being improved much further. The quest for fusion is not simply achieved or failed, working on tough problems like this leads to technological progress at every step along the way.

It still amazing how much of the periodic table we owe to this place. https://www.llnl.gov/news/tags/periodic-table

A considerable number of post-1960 Nobel prizes in physics and chemistry, as well as a fair bit of the medicine ones, come from sensor-related discoveries.

Either they're directly applicable to sensing phenomena, or they form a substantial part of a sensor technology.

Contrast with the pre-1960 period which was dominated by discovery of fundamental particals, elements, and laws or principles.

Disclaimers: this is based on a somewhat casual review of awards, and even if my own assessment is reliable, the Nobel award process itself has numerous opportunities for bias and trend-based behaviours.

While everyone is focusing on the picosend part of this, I’m more impressed by the neutron detection. Electrically charged particles sound much easier to detect, let alone with any kind of temporal precision

It reminds me of the gravity wave detectors. It boggles my mind that we are able to build machines that can measure such staggeringly tiny effects.

Lol.. livermorons

Livermorons? Really?

It's the correct demonym for people from Livermore and also a bit funny. One of the breweries in the area even named a drink after it.

Maybe they have a sense of humor about themselves.

you need to with the heat there in the summer

> I’m proud of my fellow...

The part after that, was it a typo? :)

Nope, looks legit: https://www.google.com/search?q=livermorons+site:www.reddit....

To be honest, Livermorans sounds a bit more natural to me than Livermorons. And it does appear that some people from Livermore call themselves Livermorans, like "Cheryl is a native Livermoran" [1].

[1] https://www.lvwine.org/blog/winemakers-talk-harvest-favorite...

I think you miss the point: it’s a friendly in-joke that the people who stay in that area are “morons”.

You see this in places where there isn’t much to keep you there except your profession, typically government. I’m aware of Livermore and Lemoore, but I’m sure there are others.

And to completely explain the joke to death, it's also ironic to self-deprecatingly call yourselves "morons" when you work at a scientific laboratory.

No, this has nothing to do with those of us that choose to live here being stuck because of our professions, what the heck gave you that idea?

Everyone I know who lives here LOVES Livermore. It’s decent commute distance to most places in the Bay Area, is surrounded by beautiful hills, 40+ wineries, an award winning downtown, and the friendliest people of any biggish California city I’ve lived in.

It’s a joke, but related to the awkward sounding and looking term Livermoran.

There is a LOT more keeping the 100k of us in Livermore than our professions.

My apologies; I grew up half and half between Marin and Fresno and that’s what I recall for both.

If I mistook where the term up north came from then I do apologize.

Edit: I think an issue was with my explanation. The people I know in both areas actually love it; people outside the area think they are stupid for living there. Therefore there is some appropriation of the pejorative.

Once again, if that’s mistaken in reference to Livermore then I apologize.

We can do so much and yet so little. All of this progress may amount to nothing if we cannot overcome our internal obstacles to our collective survival.

Awaiting the downvotes but it's true.

lol yeah y'all aren't in denial, sure....

Reply on news.ycombinator.com