LHC portal

Woopie!!!

Way to go guys!!!!!!!!!!!!!!!!!!

Hi, I see that about 20% of the beam is lost (It started at 2.5E12 and now it is ~2.0E12). Is this caused by collisions? Is it safe to loss this amount of particles?
Thanks
Fernando.

A few protons are lost due to collisions with molecules of the imperfect vacuum in the tube, but most are being lost on the collimators as the beam spreads out. So long as the loss rate is not too high that is perfectly safe. The collimators are designed to take the loss and protect more delicate components.

I can see nearly 2,5 10e30cm-2s-1 lumi, is this a new record?
oldboson

It was around about that level yesterday too.

does any one know when live collisions will be veiwable again?

Interesting comment in LHCb log book:

Message ID: 16934 Entry time: 02-Aug 04:32
Author: Conor Fitzpatrick

Additional amazingness can be seen in the AB & OP logbook- they are seeing the effect of the tides on the beam
energy.

Dave

tomey36 wrote:does any one know when live collisions will be veiwable again?

Nearly every day, just have a look at the "coordination" page on the vistars...

By the way, new record today, they've just broken the 3e30 barrier!

Nice work guys

Does anybody know why they witness such a drop in instantaneous luminosity (50% in a few hours), where the beam intensity stays nearly constant?

Bornerdogge wrote:Does anybody know why they witness such a drop in instantaneous luminosity (50% in a few hours), where the beam intensity stays nearly constant?

I was wondering that too, I guess the bunches start to spread out over time so making collisions less likely and hence luminosity lower.

Does anybody know why they witness such a drop in instantaneous luminosity (50% in a few hours), where the beam intensity stays nearly constant?

Also luminosity is proportional to (intensity)^2, so you would expect it to drop faster.

I observe a rapid decline at the same time as tune and orbit feedback are turned off at declaration of stable beams. Comments from the enlightened?
And every collision (or grazing contact) kills some protons, plus losses at the collimators and beam gas events cut down the available participants. It seems they start with an instantaneous luminosity of almost 3 units and let it decay down to about 1 unit after 14 hours or so then dump and do a refill.

So 4 am Friday till 7 pm physics, reset 7pm till 1:42 AM sat 1:42 stable beams again.
Almost routine.

It is just a guess, but it could be that some protons are "better" at colliding than others.
If that is the case, the "good" ones would be the ones to go first, so that the quality of the beam quickly deteriorates, and that luminosity drops as a result.