What do the displays mean ?

[Xymox]

This layout shows the points along the LHC we see referenced in the Vistars and in comments.

[Xymox]

From another thread on the forum comes a awesome description of what is going on..

From chtephan

During "regular physics running" (which is still weeks-months away), the LHC mode of operations will be done in "cycles".

Each cycle consists of several steps. First, the magnets are brought to currents needed for injection energy beam (450 GeV per beam, which is what the maixum SPS energy is). Then the beam is actually injected from the SPS until the LHC ring is full. The next step is then the "ramp", i.e. the beams are accelerated. Once the energy is reached (2.2 TeV around christmas, then 3.5 TeV next year, eventually 5 TeV and 7 TeV in a few years after some major improvements), the beams are kept at that energy (flat top) for a few hours and squeezed (i.e. compressed to be as thin as possible) so that the collisions at the experiments lead to a best-possible collision rate (luminosity). Once the beams are depleted, the remains are dumped and the current in the magnet ramped down (snapback). Then the whole story restarts from the beginning.

The LHC state that is shown on page 1 is the mode that the LHC is currently in, i.e. which "master program" is controlling the components. There are a few of them, some having a lot of automatism (which is for the future when the LHC will mostly run autonomously), but also some needed for testing, where manual adjustments are allowed by the operators.

The "pre-cycling" stage would be a stage where basically the LHC system is ready, but none of the magnets are operating, i.e. the state before the start of a new cycle (sort of "standby"). The next strage would then be "injection" or "fill".

[photino]

This site explains the codes above the four images on LHC Page1. They denote the beam TV camera the image is coming from.
http://ab-dep-bi-pm.web.cern.ch/ab-dep- ... ies.BTVLHC

It would be nice to understand better the actual image itself

[Danny252]

I think the colour of the image shows the [atom?] density over a cross-section of the LHC - blue being empty, red being "stuff here". Hence why you get red dots appear when a beam is supposedly running - I think the red bars that appear are actually part of the machinery being picked up for some reason.

Looking at the Status Op page, why is it that ATLAS has such high background readings, whilst the other 3 detectors are virtually zero? On Background 2, Atlas is sat at 3000+. Are the other background detectors just not plugged in?

[photino]

Or maybe the red bar (like for instance at the moment on the right at BTVST.A4R8.B2) is a beam that is not very collimated? Then the red bar on the left display (BTVST.A4L2.B1) would also be the presently circulating second beam? Ah well, maybe someone from CERN will enlighten us at some point...

[Danny252]

And yet, even with no beams running (as of right now, apparently), dots and bars are everywhere...

I'm sure it makes sense to the boffins!

[jepson]

SMP means "Safe Machine Parameters". EDMS 883620 lists (in a very roundabout way) the conditions under which each is true (except for Global Beam Permit, I guess that's a human decision). EDMS 810607 contains them too, along with other info (such as the locations of the detectors).

[Xymox]

Wow you guys are really finding great stuff...

Ive been watching this stuff for a long time.

The bars and dots and all that are just strange noise and weirdness..

NORMALLY these show very clearly a bright red dot close to center showing the beam location. They can choose the location along the ring.

I have no idea why recently they have been showing this junk. Also the text above the windows gets garbled.

I have asked that they show the real beam. That it would be cool to see it.

Alas they are busy... There might be something minor wrong too. I don't know..

Yoy got me on the Status-op background.

I am hoping we will get a CERN guy/girl who might take the time to explain these things for us..

Once we know what all this is. I will use photoshop and also create a page with screen shots and arrows pointing to section of the displays showing what the function is and what to watch for.

You guys are awesome locating this info... Thanks..

[photino]

Re the BTV displays on page 1: it appears the BTV images are produced by lowering a scintillating screen into the beam. Since this somewhat degrades the beam itself, the screen is only lowered into the beam when measurement is required. I suspect some of the images we are seeing are artifacts of BTV being on but the screen being in its retracted position.

[Xymox]

O.... well that explains it..

[morgad]

A couple of interesting changes on the lhc_operations screen

* the graphs now show 20 hours of info, not 2hrs

* the energy label at the top of the screen is now in TeV, not GeV

is longer beam duration, higher energy testing planned soon ??
(is Xymox right again?)

Dave

[Xymox]

The scales on all the pages auto adjust. For some reason it seems that when the input is missing weird things occur.

Once the beam is back all the instrumentation will show correct scales. Both level and time.

Dont consider any of those display valid unless there is beam.

IMHO...

[Xymox]

When they go to high powers.... What that really means is that they will ramp up the beam. It means they will circulate the beam and push it faster each time around. This will be very obvious on the screens. All the SMP flags on the lower right corner will be green for the beam they are ramping.

Going to higher powers will be very obvious and take time to get there. Constant ramping for a while..

[Xymox]

From a different thread... PCollier provided some important insight.

Page 1 is dynamically configured depending on the mode of the machine so the information available will vary.

Here are a few definitions to be going along with:

TI 2 - is the transfer line between the SPS and the LHC for the clockwise beam. It is 2943m long.
TI 8 - is the anticlockwise transfer line from the SPS to LHCand is 2694m long

TED - stands for 'Target Extraction Dump' There are stoppers that can be put into the transfer lines there is one at the top and one at the bottom of each line (upstram and downstream) . Each one weighs about 20 tonnes.

TDI - this is an injection protection element just downstream of the injection point. It has upper and lower jaws that can be moved into the beamline. If the injection kickers fire correctly the beam will be fired through the gap between the jaws. If the kickers do not fire - for example when we are setting up injection - the beam hits one of the jaws and is absorbed.

BKG1,2,3 - These are figures of merit provided by the experiments to the machine. Each one is derived from a specific part of the detector (and are therefore experiment specific). They are normalized to a number between 1 (good) and 5 (bad) - 0 means it is not yet active.

Hope this helps.

[Danny252]

Wonder what all CERN's acronyms mean on those displays? They made a list!

http://lhccwg.web.cern.ch/lhccwg/Biblio ... ronyms.htm