Intensities

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Vecctor
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Joined: Fri Dec 11, 2009 1:25 am

Intensities

Post by Vecctor » Sun Mar 21, 2010 2:23 am

Does anybody know the reason why the beam intensities on the "LHC_OPERATION" page seem to be the ones displayed in the curves, while the intensities on "LHC page 1" differ very much (especially for B2)?

Thanks in advance and I wish all of you a last exciting week (i guess) till world record collisions!!!

oxodoes
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Re: Intensities

Post by oxodoes » Sun Mar 21, 2010 3:37 pm

Vecctor wrote:...seem to be the ones displayed in the curves ...
Which curves do you refere to??

Kasuha
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Re: Intensities

Post by Kasuha » Sun Mar 21, 2010 4:04 pm

LHC1 is an interactive page, operators can (and often do) change its contents, displayed graphs and info according to what they are working on. Just now it's only displaying beam intensities (blue line for B1 intensity, red line for B2 intensity) and not magnet energy.
LHC_STATUS is more stationary and the graph in the middle contains more time-compressed variant of the graph from LHC1, plus it displays magnet energy as black line (which corresponds to how much the beam is accelerated - if there is a beam).
Magnet energy is always increased and decreased relatively slowly to prevent hardware failures - that's why you can see slopes on the black line. Beams are injected in bunches from SPS, one bunch at a time - and usually also dumped all at once - therefore beam graph is "blocky". But both graphs display the same, except the time scale, at least now.

Vecctor
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Re: Intensities

Post by Vecctor » Sun Mar 21, 2010 4:41 pm

I refer to the blue and red intensity curves that are always displayed on "LHC_OPERATION" and sometime on "LHC1". Except for the different time scales these curves were the same on both pages whenever I watched them. But on both pages the intensities are given as numerical values as well. The value for B2 on the "LHC1" page is usually much smaller than the value for B1. And the values plotted in the curves seem to be the ones from the "LHC_OPERATION" page.
These values on "LHC_OPERATION" are almost the same, especially when the curves for both beams are almost the same. For example:
LHC1:
B1 4.80e+09
B2 3.05e+09
LHC_OPERATION
B1 5.03e+09
B2 5.05e+09
while the curves for both beams nearly coincide on both pages

oxodoes
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Re: Intensities

Post by oxodoes » Sun Mar 21, 2010 5:35 pm

Ok the numbers given on page1 are definitly wrong! They are very jumpy and even go up rather often. I don't know a reason (yet).

oxodoes
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Re: Intensities

Post by oxodoes » Sun Mar 21, 2010 10:58 pm

See here:Image

The encircled value is wrong compared to the chart and the values on LHC_OP and is showing a rather random behaviour. When B1 is in the same is true for the associated value.

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Tau
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Re: Intensities

Post by Tau » Mon Mar 22, 2010 7:08 am

The short answer is: there are different ways to measure intensities (which is obviously hard in the first place). They have built several different instruments to do that, and these are not completely calibrated towards each other.
It was actually worse last year.
- Tau

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