Talk:Barn (unit)

Barn is not listed

The barn is not listed on the official table of accepted non-SI units that is linked in the article...perhaps it was removed? I'll remove that statement in a while, unless someone objects. --Bmk 14:52, 10 July 2006 (UTC)

The barn is used in documentation from the early nuclear era. I don't think it's much found these days (though I'm not up in the field, so I could well be mistaken). I would rather see it added to the page of unofficial units than have the link deleted from here.--King Hildebrand 16:26, 2 August 2006 (UTC)

It is still commonly used in high-energy physics, both particle and nuclear. —Preceding unsigned comment added by 137.138.77.201 (talk) 13:00, 7 May 2009 (UTC)

I would like to offer, as a nuclear physicist, the barn was in my 3rd year textbook. furthermore it should not be denied SI status for having a humorous name.--Fx303 (talk) 04:50, 16 July 2009 (UTC)

The "barn" is a legitimate unit used all the time by nuclear physicists and particle physicists. It is a common everyday unit in the field and one cannot work without it. On the other hand, in 23 years in the field, I've never ever heard of "shed" or "outhouse", which seem like obvious joke terms to me. —Preceding unsigned comment added by 142.90.119.70 (talk) 19:29, 9 September 2009 (UTC)

I agree with above. No-one uses "shed" or "outhouse" and including these terms in the main definition section makes Wikipedia look ridiculous. I suggest deletion of this sentence. (Searching arxiv.org for "outhouse" yields no results. Searching for "shed" isn't so easy because it occurs in phrases like "shed like on".)92.20.226.103 (talk) 02:06, 7 July 2012 (UTC)

I've "been bold" and deleted it. I hope that's OK. 92.20.226.103 (talk) 02:09, 7 July 2012 (UTC)

I also think the ZNSNCS terms (in the section "Commonly used prefixed versions") are complete nonsense and should be deleted. These terms are just one person's joke idea and have no currency. But I've deleted enough today. — Preceding unsigned comment added by 92.20.226.103 (talk) 02:24, 7 July 2012 (UTC)

Just some random online glossary will not do as an authority to confirm the usage of "outhouse". Will move it to the section with "commonly used prefixed versions". Kotika98 (talk) 13:51, 8 April 2013 (UTC)

Origin

I had it explained to me a few years back as this: researchers had expected that neutrons would have to have a direct strike on a nucleus to trigger the fission, but then found that it would still trigger it when passing close by. This meant that the cross-sectional area for triggering the reaction was much larger than expected - i.e. like hitting a barn door. I don't have any reference to back this up though, so I don't want to blindly change the explaination in the article. Andrewjrallan 14:50, 19 July 2006 (UTC)

I think it was in Fermi's biography that I read his code name for the Manhattan Project at Los Alamos was "Henry Farmer". And that the "barn" came from the old American baseball saying, "He couldn't hit the broad side of a barn." My Flatley (talk) 16:28, 9 September 2009 (UTC)

Uranium nucleus?

Gold nuclear radius ~ 3 x 10-14 metres so about 10 barns??? Uranium nucleus is one barn? was looking for link or conversion factor for barns (area) to nuclear(atomic) radius. Gadolinium neutron absorption cross section (49000barn) versus (180 picometer) atomic radius. —Preceding unsigned comment added by Shjacks45 (talk • contribs) 10:44, 1 July 2008 (UTC)

Error in shed size ?

See shed - it says 10^-48 m², but if it is 10^-24 b, then it should be 10^-48 *cm*², or 10^-52 m². See also Wikipedia entry for 'shed'. Main article corrected accordingly. —Preceding unsigned comment added by 24.61.45.41 (talk) 03:06, 3 July 2008 (UTC)

Only hearsay. All I ever worked with was barns. I took a class in radiation effects on ferritic materials back in about 1985. Sheds came up in the class as being the same as a millibarn. Shortly afterwards, the question came up that if a shed was a millibarn, what was a microbarn. I was the only farm kid in the class, and the answer was obviously an outhouse. Not a chance at getting official verification.

If a shed was 10E-48 cm^2, it would be useful for neutrino cross sections. It would not be very useful for anything else. And an outhouse would still not be useful (as an outhouse has to be smaller than a shed).Fortran (talk) 02:17, 4 January 2012 (UTC)

Redirect from "Barns"

I changed the redirect from "Barns" from "Barn (unit)" to "Barn (disambiguation)", since I think those searching for "barns" are more likely to be interested in the buildings than the units of measurement. Giles Martin (talk) 15:32, 1 April 2009 (UTC)

Time for Fermilab to achieve an inverse femtobarn

I found a press release from Fermilab to indicate how long it took to achieve a femtobarn and replaced the "citation needed". However the reference seems to indicate that run II started March 2001 and one femtobarn had been achieved by June 2005. This refutes the claim that it took over a decade. Perhaps the claim is including the time of run I (how long?). —Preceding unsigned comment added by 76.21.117.175 (talk) 04:08, 9 April 2010 (UTC)

Silo

I couldn't find a reference for "silo". Anyone? — Preceding unsigned comment added by 129.217.129.134 (talk) 19:08, 29 November 2011 (UTC)

Inverse femtobarn

> The "inverse femtobarn" (fb−1) is a measurement of particle collision events per femtobarn of target cross-section, and is the conventional unit for time-integrated luminosity.

It is true that the number of events in some channel is equal to N=I σ, where I is integrated luminocity and sigma the crosssection. But, that definition above is strictly speaking not correct. It confuses the cause and effect. The correct definition is the number of particles delivered divided by the area of the beam. It is called "integrated luminocity" and it does not depend on the target cross section. For example, in a fixed target experiment, it is the a measure of the beam , while the crosssection is a property of the target only. 112.80.242.190 (talk) 02:16, 10 July 2013 (UTC)

Barn origin

Barn was originated by Fermi, as the uranium nucleus was 'as big as a BARN DOOR'. see

http://books.google.co.uk/books?id=DQVEAQAAIAAJ&pg=PA408&img=1&pgis=1&dq=barn+door+nucleus+unit+fermi&sig=ACfU3U0uqtFGt-u-17RLSJwsxyVQXygeNg&edge=0

I suggest changing the wording in the article to reflect this, citing the above or a better source. GilesW (talk) 14:26, 5 May 2014 (UTC)

This is a decade's later addition, but I think the Holloway/Baker report is probably better than Seaborg's uncited assertion.

For future use, the above link is to the diaries of Glenn Seaborg. In the entry for 12/20/1944, he wrote:

Near the end of Jaffey's lecture Katzin asked whether the unit of cross section referred to is a barn or a barn door, to which I replied that the unit is called a barn because it is as large as a barn door in comparison with actual cross sectional areas of nuclei. The term was originated by Fermi.

And that's all he said. While an interesting anecdote, I do not think it carries the weight as Holloway and Baker's report, or even warrants mentioning, by itself. It sounds like Seaborg was just reporting something he heard indirectly. Given that the first report to feature the term came out of the Purdue program (which Fermi was not associated with), it seems more plausible on the face of it that Holloway and Baker coined it as they claimed to. --NuclearSecrets (talk) 00:01, 3 March 2024 (UTC)

Kilobarn, millibarn etc.

1 km² = 1 000 000 m², not 1000, since it's defined as 1000 m × 1000 m. How come 1 kilobarn is 1000 barn?

Just like how 1 kilolitre is 1000 litres. Double sharp (talk) 20:36, 30 November 2022 (UTC)

And how 1 millilitre is 0.001 litres. Dondervogel 2 (talk) 01:15, 11 November 2023 (UTC)

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Humorous unit?

Does it make sense to add List of humorous units of measurement to the "See also" sections for this and shakes? -- ScratchMonkey (talk) 11:53, 9 May 2021 (UTC)