<p>LIGO detectors have two 4 km arms, and everything in those arms in suspended in a vacuum. The actual dimensions of those arms I was unable to find, but <a href="https://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.116.061102" rel="nofollow">the published paper here</a> has more information for you to peruse.</p>

CC BY-SA 3.0
2016-03-03T17:03:52.387Z
2016-03-03T17:03:52.387Z
Pulchritude
<p>The arms are $4\,\mathrm{km}\,\times\, 1.2\,\mathrm{m}$:</p>

<p>From the <a href="https://www.ligo.caltech.edu/page/vacuum">LIGO webpage</a>:</p>

<blockquote>
  <p>The 1.2 m diameter beam tubes were created in 19-20 m-long segments, rolled into a tube with a continuous spiral weld. While a mathematically perfect cylinder will not collapse under pressure, any small imperfection in a real tube would allow it to buckle (a crushed vacuum tube would be catastrophic). To prevent collapse, LIGO's tubes are supported with stiffener rings that provide a significant layer of resistance to buckling under the extreme pressure of the atmosphere. The tubes must withstand these stresses for at least 20 years.</p>
</blockquote>

CC BY-SA 3.0
2016-03-03T17:11:22.703Z
2016-03-03T17:11:22.703Z
pela
<p>The LIGO complex is very large, but I assume that there is a very small chamber that actually does the science since they are measuring very small sheers. How big around is the actual evacuated chamber?</p>

<black-hole><space-time><gravitational-waves><instruments>
What are the dimensions of LIGO Detector evacuated chambers?
veda905
# What are the dimensions of LIGO Detector evacuated chambers?

(Asked by: username_0 on 2016-03-03)

The LIGO complex is very large, but I assume that there is a very small chamber that actually does the science since they are measuring very small sheers. How big around is the actual evacuated chamber?

**Tags:** black-hole, space-time, gravitational-waves, instruments

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## 2 answers

### Answer by username_2 on 2016-03-03. Score: 12 | Accepted answer

The arms are $4\,\mathrm{km}\,\times\, 1.2\,\mathrm{m}$:

From the [LIGO webpage](https://www.ligo.caltech.edu/page/vacuum):

> The 1.2 m diameter beam tubes were created in 19-20 m-long segments, rolled into a tube with a continuous spiral weld. While a mathematically perfect cylinder will not collapse under pressure, any small imperfection in a real tube would allow it to buckle (a crushed vacuum tube would be catastrophic). To prevent collapse, LIGO's tubes are supported with stiffener rings that provide a significant layer of resistance to buckling under the extreme pressure of the atmosphere. The tubes must withstand these stresses for at least 20 years.


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### Answer by username_1 on 2016-03-03. Score: 2

LIGO detectors have two 4 km arms, and everything in those arms in suspended in a vacuum. The actual dimensions of those arms I was unable to find, but [the published paper here](https://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.116.061102) has more information for you to peruse.


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