Tokamak fusion

[MigL]

Temperature of 100 Million degrees acheived in a 'spherical' Tokamak reactor, barely more than 3 feet across.

Achievement of ion temperatures in excess of 100 million degrees Kelvin in the compact high-field spherical tokamak ST40 - IOPscience

Another small step on what promises to be a rewarding but long journey.

[Genady]

I was taught that the correct phrase is "100 million kelvins" rather than "100 million degrees Kelvin."

[John Cuthber]

12 hours ago, Genady said:

I was taught that the correct phrase is "100 million kelvins" rather than "100 million degrees Kelvin."

"100 million kelvins" is a very big  room full of scientists.

"100 million kelvin" is a temperature.

[Genady]

1 hour ago, John Cuthber said:

"100 million kelvins" is a very big  room full of scientists.

"100 million kelvin" is a temperature.

You are right. OTOH, e.g.,

Quote

According to SI convention, the kelvin is never referred to nor written as a degree. The word "kelvin" is not capitalised when used as a unit, but is pluralised as appropriate. The unit symbol K is a capital letter. For example, "It is 50 degrees Fahrenheit outside" vs "It is 10 degrees Celsius outside" vs "It is 283 kelvins outside".

Kelvin - Wikipedia

Edited June 2, 2023 by Genady

[John Cuthber]

Interestingly, Wiki doesn't follow that reliably.
e.g
This increases the density and temperature of the core until it reaches approximately 100 million kelvin, 
from
https://en.wikipedia.org/wiki/Helium_flash

Presumably because nobody would say it is 25 Celsiuses or 90 Fahrenheits outside

[studiot]

3 hours ago, John Cuthber said:

"100 million kelvins" is a very big  room full of scientists.

"100 million kelvin" is a temperature.

I had to laugh when I saw this so +1 to John.

 

As far as I can tell you are both a bit right and a bit wrong.

The relevant body here is the French Authority responsible for Systeme Internationale, whose unit the kelvin is.

They redefined the kelvin in 2017/2018 so the first trap is "which elvin are you using ?"

As far as the French are concerned, the unit is spelled with a lower case k, but the symbol is an upper case K, because the lower case k is already allocated to the Boltzmann Constant, to which the kelvin is related.

Perversely the English speaking world as represented by the UK and US National Physical Laboratories use upper case for both Kelvin and K.

 

@Genady  A perfect example of a camel (which in an English saying is aa horse designed by a committee.

[Genady]

20 minutes ago, studiot said:

I had to laugh when I saw this so +1 to John.

 

As far as I can tell you are both a bit right and a bit wrong.

The relevant body here is the French Authority responsible for Systeme Internationale, whose unit the kelvin is.

They redefined the kelvin in 2017/2018 so the first trap is "which elvin are you using ?"

As far as the French are concerned, the unit is spelled with a lower case k, but the symbol is an upper case K, because the lower case k is already allocated to the Boltzmann Constant, to which the kelvin is related.

Perversely the English speaking world as represented by the UK and US National Physical Laboratories use upper case for both Kelvin and K.

 

@Genady  A perfect example of a camel (which in an English saying is aa horse designed by a committee.

You are right. 

At least, it is agreed that it is incorrect to say, degrees Kelvin, isn't it?

[John Cuthber]

42 minutes ago, Genady said:

You are right. 

At least, it is agreed that it is incorrect to say, degrees Kelvin, isn't it?

I think we all agree on that.

1 hour ago, studiot said:

The relevant body here is the French Authority responsible for Systeme Internationale, whose unit the kelvin is.

The authority isn't French, it's BIPM. The I stands for international. Diplomatically speaking, it's not even in France.

Plus important encore, nous ne parlons pas français

[swansont]

3 hours ago, studiot said:

They redefined the kelvin in 2017/2018 so the first trap is "which elvin are you using ?"

They didn’t change the value when they redefined it. It’s just now defined in terms of physical constants. It would only matter if you were trying to experimentally realize the value, since the method would differ.

[MigL]

The only ones to use '100 Million degrees Kelvin' are the authors of the paper; I simply used 'degrees'.
So, while it is true that you may know the correct usage of kelvin units, more importantly, you don't know how to reach 100 Milliion degrees in a small Tokamak fusion reactor 😄 .

[exchemist]

26 minutes ago, MigL said:

The only ones to use '100 Million degrees Kelvin' are the authors of the paper; I simply used 'degrees'.
So, while it is true that you may know the correct usage of kelvin units, more importantly, you don't know how to reach 100 Milliion degrees in a small Tokamak fusion reactor 😄 .

And in fact at that temperature it makes bugger all difference whether you use C or K. 

[Genady]

Just now, exchemist said:

And in fact at that temperature it makes bugger all difference whether you use C or K. 

But not F.

[swansont]

2 hours ago, Genady said:

But not F.

That’s only a factor of ~2. With a value of 100 million, given the lack of precision, that’s ignorable.

I remember a talk (I think it was highlighting the equivalent temperature scale of the TRIUMF protons down to the trapped atom temperatures in our experiment) and someone asked what the units were. The speaker said “Does it matter?”

[Genady]

26 minutes ago, swansont said:

That’s only a factor of ~2. With a value of 100 million, given the lack of precision, that’s ignorable.

Not sure in this case. They refer to 8.6 keV, which assumes a precision of 10% rather than 100%, I think. Also, they compare to the previous max of 5 keV, which means that a factor of ~2 is not ignorable. 

[MigL]

You're right; I should have iust said 8.6 keV, and avoided all this.

And us canadians went metric in the 70s, so 'degrees' does not refer to ^oF, but to ^oC.

Edited June 2, 2023 by MigL

[studiot]

7 hours ago, John Cuthber said:

I think we all agree on that.

The authority isn't French, it's BIPM. The I stands for international. Diplomatically speaking, it's not even in France.

Plus important encore, nous ne parlons pas français

Really  ?

 

The Bureau International des Poids et Measures is not French, though its official language is?

And what's this ?

 

Quote

History of the Pavillon de Breteuil

The BIPM is based in the Pavillon de Breteuil, which was granted to the BIPM by France in 1875. The Pavillon de Breteuil and its surrounding park are located within the Domaine national de Saint-Cloud. Find more about the history of the Pavillon de Breteuil.

 

History of the Pavillon de Breteuil
(only available in French)

 

 

 

 

5 hours ago, swansont said:

They didn’t change the value when they redefined it. It’s just now defined in terms of physical constants. It would only matter if you were trying to experimentally realize the value, since the method would differ.

 

really ?

 

So what is all the fuss about the difference between 273.15 and 273.16 and why did they need to redefine the value of Boltzmann's constant  ?

[swansont]

24 minutes ago, studiot said:

Really  ?

 

The Bureau International des Poids et Measures is not French, though its official language is?

It’s an international organization. It is physically located in France (because it needs to exist somewhere), but is not a French organization.

24 minutes ago, studiot said:

really ?

 

So what is all the fuss about the difference between 273.15 and 273.16 and why did they need to redefine the value of Boltzmann's constant  ?

What fuss? The old definition was based on the triple-point of water, which is at 0.01 degrees C. The freezing point of water is still 0 C and 273.15 K.

The redefinition happened because of a push not to define basic units on physical artefacts. e.g. the meter and kilogram are not based on platinum-iridium bars/blocks anymore. 

[John Cuthber]

1 hour ago, studiot said:

Really  ?

Yes, really.
We really are not speaking French.
And, from WIKI,
"It is based at the Pavillon de Breteuil in Saint-Cloud, France, a 4.35 ha (10.7-acre) site (originally 2.52 ha or 6.2 acres)^[5] granted to the Bureau by the French Government in 1876. Since 1969 the site has been considered international territory"
So it's really not in France  diplomatically speaking, It is surrounded by France

And "The Bureau International des Poids et Measures is not French, though its official language is?"
is particularly ironic.
England left the EU.
The EU's principle official language is still English.
It's a bit like Eurovision song contest winners; The UK loses, but English usually wins.
The Catholic church is world-wide, but its official language is Latin.
 

[iNow]

On 6/1/2023 at 3:46 PM, MigL said:

Another small step on what promises to be a rewarding but long journey.

What might we do with this? What might be some risks?

[MigL]

monstrates the stability of this compact Tokamak system in  reaching 100 Million degree temps required for Fusion.
It demonstrated this stability for about 0.15 seconds.
The obvious next steps are extending this stability time ( to be of practical use it eventully needs to be unlimited ), and, of course, you need to have a sizeable excess net energy output to be of any practical use.
This won't happen tomorrow.

[Genady]

14 hours ago, MigL said:

You're right; I should have iust said 8.6 keV, and avoided all this.

And us canadians went metric in the 70s, so 'degrees' does not refer to ^oF, but to ^oC.

Sorry @MigL for not making clear in my first comment above that I was referring to the article's title and not to what you said. 

Edited June 3, 2023 by Genady