Taking a closer look at LHC
The proton source is where it all starts at CERN.
(a new system will be running in 2017-18 at Linac4)
"To make the protons", physicists inject hydrogen gas into the metal cylinder -Duoplasmatron- then surround it with an electrical field to break down the gas into its constituent protons and electrons. This process yields about 70 percent protons.
We can simplify the process as follows:
H2 + e- → H2+ + 2e-
H2+ + e- → H+ + H + e-
H + e- → H+ + 2e-
For the LHC beam, we need:
2808 bunches x 1.15·1011 = 3·1014 protons per beam
or, 6·1014 protons for the two beams (1)
A single cubic centimetre of hydrogen gas at room temperature contains
with P = 105 Pa ,, V = 10-6 m3 ,, T=293 K
using P·V = n·R·T -
n = 4·10-5 moles ,, N = 4·10-5 x 6·1023 = 2.4·1019 molecules
So, about 5·1019 atoms of hydrogen (2)
Taking into account (1) and (2), the LHC can be refilled about 100000 times with just one cubic centimetre of gas – and it only needs refilling twice a day!
n = 5000/2 = 2500 moles
2500 x 6·1023 = 1.5·1027 molecules
N = 2 x 1.5·1027 = 3·1027 atoms
Taking into account that the process yields about 70% protons we have:
0,7 x 3·1027 = 2.1 ·1027atoms
With (1), this cylinder can be used:
2.1·1027 / 6 ·1014= 3.5·1012 times
Since the LHC is filled every ten hours, this cylinder could be used for:
10 x 3.5·1012 = 3.5·1013 hours
So, about 4 ·109 years
The hydrogen will diffuses out of the bottle faster.
A new ion source (providing in this case H-) will be working in the new linear accelerator, Linac4.
But not only protons for LHC
Xabier Cid Vidal, PhD in experimental Particle Physics for Santiago University (USC). Research Fellow in experimental Particle Physics at CERN from January 2013 to Decembre 2015. Currently, he is in USC Particle Physics Department ("Ramon y Cajal", Spanish Postdoctoral Senior Grants).
Ramon Cid Manzano, secondary school Physics Teacher at IES de SAR (Santiago - Spain), and part-time Lecturer (Profesor Asociado) in Faculty of Education at the University of Santiago (Spain). He has a Degree in Physics and in Chemistry, and is PhD for Santiago University (USC).
CERN and the Environment
For the bibliography used when writing this Section please go to the References Section