LHC to go for higher intensity next

Following the record luminosities a few days ago, the Large Hadron Collider was closed down for three days this week to make some technical corrections. This evening they are ready to restart and new plans for the next two weeks have been drawn up.

The main goal now is to increase the number of protons per bunch. The physics runs so far have used up to about 12 billion protons per bunch. A few weeks ago they did some brief tests with 100 billion protons per bunch but the beams were dumped very quickly. Now they will try to maintain high intensities long enough to declare stable beams and do physics.

Increasing the number of protons per bunch is one of three ways that they increase the overall luminosity of the beams. They can also increase the number of bunches and they can squeeze the beams as they did last week. But there is a good reason why increasing the number of protons per bunch is especially exciting. If they multiply the number by ten in one beam it means ten times the luminosity and ten times the number of collisions, but of course they can increase the number by a factor of ten in both beams so the luminosity is then increased by a factor of 100 ( That is assuming the bunches remain the same size). By comparison, if they increase the number of bunches by a factor of ten in both beams they still only increase the luminosity by a factor of ten.

The current golden orbit for physics is  a configuration of  3.5TeV/2m/12Billion/3-bunches. The plan shows them aiming for 3.5TeV/2m/40Billion/2-bunches. This will actually give a modest increase in luminosity of about 5. If they put the number of bunches back up to 3 it will be a factor of ten. That’s not bad just a few weeks after the last factor of 10. Of course sometimes they do actually keep to the plan.


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