What do the displays mean ?

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Danny252
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Re: What do the displays mean ?

Post by Danny252 » Tue Dec 01, 2009 8:37 pm

Tim Bergel wrote:I found BRAN in the acronyms list:

Beam RAte Neutrals (TAN type luminosity monitor) and TAN means Target Absorber Neutral

so yes, a type of luminosity monitor ...
It helps if I turn "case sensitive" off when searching - no wonder FF couldn't find "bran" on the acronyms sheet...

Danny252
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Re: What do the displays mean ?

Post by Danny252 » Mon Dec 07, 2009 11:31 am

It appears Status Op has lost its BRAN counts on the top graph, and this is now showing Intensity for each beam and Power only.

Might be because the machine is down currently, however.

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morgad
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Re: What do the displays mean ?

Post by morgad » Mon Dec 07, 2009 12:18 pm

It was like that last night, made things much easier to see
also I note that page one now has a 'recovery' mode

Dave

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Re: What do the displays mean ?

Post by Xymox » Wed Dec 09, 2009 6:11 am

Yea Page 1 and Status-op have been wacky lately...

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Re: What do the displays mean ?

Post by Harbles » Sun Feb 21, 2010 10:25 pm

And I see you added the LHC CONFIG vistar to the Portal. Most of the items are fairly evident from their labels.
I found this on Ghost Bunch warning;
" The BPIM also records the bunch structure for both beams and how many bunches which
collide in LHCb. It is also able to detect bunches which are not in the proper locations (ghost
bunches)."
From https://lbtwiki.cern.ch/pub/Operation/W ... cedure.pdf

And This on BPTX ;
" ΔT will be the delay in ns between calculated crossing point (one value from BPTX and one from trackers if available) versus theoretical crossing point. ΔT will be positive when the calculated collision point is ahead of the theoretical IP clockwise. Inversely, if the calculated IP is behind the theoretical IP, then the sign of ΔT will be negative.
For example, if ATLAS BPTXs give an estimated crossing point 6ns far from the theoretical crossing point in the direction of ALICE, ΔZ will be +6ns."
From http://lhc-experiments-timing.web.cern. ... ration.htm

More details from our experts?

Harbles
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Re: What do the displays mean ?

Post by Harbles » Fri Feb 26, 2010 6:51 pm

The busy Gnomes at CERN have added yet another op-Vistar screen LHC_Exp_Magnets.
http://op-webtools.web.cern.ch/op-webto ... =LHCEXPMAG
Info on 6 magnets their State, Current, And polarity. Also 4 graphs showing the ramping.

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Re: What do the displays mean ?

Post by Danny252 » Fri Feb 26, 2010 7:50 pm

LHC Config seems to be mostly collision, tune, luminosity info and so forth. There's also some general info on the accelerator at the top, and what Harbles posted above.

Accelerator Mode: Not sure if this means LHC as a whole, or just RF.
Beam Mode: Fairly self explanatory I'd hope
Active Filling Scheme: Pilots, injection, etc.
Active Hypercycle: Currently "NOM_1.18TEV_2010", so I'd say it's the overall power configuration of the machine.

Target Beta*: No idea, metres? EDIT: photino suggested this could be related to Beta[tron] Oscilliations?
Target Crossing Angle: Angle between the beams at the IPs, microradians
Spectrometer Angle: I'd need to look up what spectrometers this refers to, microradians
Target Beam Separation: How far apart the beams are at the IP, millimetres

Abort Gap Population: The abort gap is a gap left to allow time to change the beam path to the dump. This is explained fairly well somewhere I believe. If stuff is here, there's a problem - explained in the chat as "Where you REALLY don't want a ghost bunch"
Ghost Bunch: I'll go with Harbles' explanation of a bunch being somewhere it shouldn't, a bunch being a group of protons.
DeltaT: As Harbles said, time lead/lag of the bunches (..right?)
Luminous Size: Luminosity relates loosely to collision rate/chance, so I guess this is related to how spread out the beam is - you want it "squeezed" to get a good collision rate.

The Magnets VISTAR only shows the detector magnets - hence I believe this is either to measure the interaction of these with the beam, or just to let the CCC know the status of the experiments (I doubt they'd be happy if someone threw protons at them unexpectedly when turning it on).

Of course, this is just our best guess from chat!

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Re: What do the displays mean ?

Post by amiso » Sun Mar 21, 2010 10:14 pm

Hi,

Precycle : I think that this means that they actually ramp the magnetic field up and then down but when the beams are not loaded. doing this ensures that any magnetic hysteresis is at a known "usual" state. Doing this avoids any surprise when the beams are filled and potentially dangerous!

"E : xxx" display: I think that this display is a direct calculation from the magnetic field, not from a measuremet on the protons.

"I (B1)" display : There were many explanations about this earlier. Let me propose my explanation (and please tell me if I am wrong): The protons are grouped into "bunches" and are charged. Then it is very easy to couple (measure) the beam intensity using a simple transformer coil. The measured quantity is then the total charge flowing through the pipe during one second, ie, the average current.

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WOPR
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Re: What do the displays mean ?

Post by WOPR » Thu Mar 25, 2010 12:24 am

There's been a new SMP flag on LHC1 for a while: "Link Status of Beam Permits". Anyone know what this is?

Right now is the first time I've ever seen it green.

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Re: What do the displays mean ?

Post by Xymox » Thu Mar 25, 2010 6:28 am

Hehehe,,,, WOPR...

Yes it means if one beam dumps it dumps the other beam as well I believe..

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WOPR
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Re: What do the displays mean ?

Post by WOPR » Thu Mar 25, 2010 10:32 pm

Ah, makes sense.

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Re: What do the displays mean ?

Post by bgab001 » Mon Mar 29, 2010 9:06 pm

On the CMS update it says :
"LHC operators have ramped both beams to an energy 1.18 TeV again. Now they "squeeze" the beams (reduce their transverse profile) by focusing the beams with magnets. This increases the luminosity (which is inversely proportional to "beta*") when the beams pass through each other. The steps achieved are in the Page 1 displays above. Trigger rate started from below 2 Hz and increased to around 3 Hz as beta* decreased from about 11m to 9m and then to 7m."
I guess the "target beta*" is easier to understand then...
B.

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Re: What do the displays mean ?

Post by Harbles » Fri Apr 09, 2010 7:12 pm

More Op Vistar newness LHC_Coordination http://op-webtools.web.cern.ch/op-webto ... r=LHCCOORD

And LHC_CMS_Experiment http://op-webtools.web.cern.ch/op-webto ... usr=LHCCMS

Just fuzzy pics on for now but I hope there will neat new stuff to see there soon.

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Re: What do the displays mean ?

Post by philpecsok » Sat Apr 10, 2010 12:55 am

Is there a chat room here?

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Re: What do the displays mean ?

Post by tswsl1989 » Sat Apr 10, 2010 8:53 am

A few of us congregate in #lhc on irc.gimp.org
You can use this link to chat through your web browser.

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