Page "DESY" Paragraph 47
from
Wikipedia
HERA's tunnels run 10 to 25 metres below ground level and have an inner diameter of 5. 2 metres.
For the construction the same technology was used as for the construction of subway tunnels.
Two circular particle accelerators run inside the tube.
One accelerated electrons to energies of 27. 5 GeV the other one protons to energies of 920 GeV in the opposite direction.
Both beams completed their circle nearly at the speed of light, making approximately 47 000 revolutions per second.
Page 1 of 1.
2.443 seconds.