2014 machine commissioning and 2015 start up

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andrewp
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Re: 2014 machine commissioning and 2015 start up

Post by andrewp » Sun Apr 05, 2015 3:25 pm

After today's excitement, I'm disappointed that we have to wait 8 weeks more to see collisions at 13 TeV. This conservative schedule seems to be largely about safety concerns.

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Re: 2014 machine commissioning and 2015 start up

Post by pcatom » Sun Apr 05, 2015 4:41 pm

andrewp wrote:After today's excitement, I'm disappointed that we have to wait 8 weeks more to see collisions at 13 TeV. This conservative schedule seems to be largely about safety concerns.
Have you any idea what is involved in re-commissioning the LHC for operation? 8 weeks is optimistic if everything goes to plan - working 24 hours a day!

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Tau 2
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Re: 2014 machine commissioning and 2015 start up

Post by Tau 2 » Sun Apr 05, 2015 6:49 pm

But the good news is that these 8 weeks are going to be very exciting!
In a way, they're more interesting than the production runs.
I love it see how they manage to learn from every measurement (and every mistake) they make.
One example is how they handled the earth fault in sector 23: it must have been pretty scary to decide to blow it up, but they really made sure they knew what they were doing! Those things make for pretty interesting stories to follow.
- Tau

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Re: 2014 machine commissioning and 2015 start up

Post by pcatom » Sun Apr 05, 2015 7:04 pm

Tau 2 wrote:But the good news is that these 8 weeks are going to be very exciting!
In a way, they're more interesting than the production runs.
I love it see how they manage to learn from every measurement (and every mistake) they make.
One example is how they handled the earth fault in sector 23: it must have been pretty scary to decide to blow it up, but they really made sure they knew what they were doing! Those things make for pretty interesting stories to follow.
Yes ... it was a bit scary - imagine putting 50kW through 2 wires with a cross section of 0.25mm2 even if it was only for 1/100th of a second. Then imagine doing it in a bath of liquid helium ...

andrewp
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Re: 2014 machine commissioning and 2015 start up

Post by andrewp » Sun Apr 05, 2015 10:35 pm

pcatom wrote:
andrewp wrote:After today's excitement, I'm disappointed that we have to wait 8 weeks more to see collisions at 13 TeV. This conservative schedule seems to be largely about safety concerns.
Have you any idea what is involved in re-commissioning the LHC for operation? 8 weeks is optimistic if everything goes to plan - working 24 hours a day!
That's the problem - I had no idea that 8 weeks was a minimum! I would love to be able to come along for the ride and watch this great beast rise up again, but I have no real insight into what's being done nor what to expect. This despite having a physics degree!
I suspect many would enjoy coming along for the ride too, out of sheer curiosity.

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Re: 2014 machine commissioning and 2015 start up

Post by pcatom » Mon Apr 06, 2015 3:24 pm

andrewp wrote: That's the problem - I had no idea that 8 weeks was a minimum! I would love to be able to come along for the ride and watch this great beast rise up again, but I have no real insight into what's being done nor what to expect. This despite having a physics degree!
I suspect many would enjoy coming along for the ride too, out of sheer curiosity.
Feel free to ask what you want to know - i will try and answer :mrgreen:

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Re: 2014 machine commissioning and 2015 start up

Post by andrewp » Mon Apr 06, 2015 4:45 pm

That's very gracious of you, considering how busy you are (and all you guys and gals working on bring-up are heroes by the way!). So here's one: what guarantees that the orbital tune set-up at 0.45 TeV will work at higher energies?

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Re: 2014 machine commissioning and 2015 start up

Post by pcatom » Mon Apr 06, 2015 5:22 pm

andrewp wrote:That's very gracious of you, considering how busy you are (and all you guys and gals working on bring-up are heroes by the way!). So here's one: what guarantees that the orbital tune set-up at 0.45 TeV will work at higher energies?
It won't - not perfectly anyway. We use feed farward - ie go up there, measure and put corrections into the settings and then feedback where we use continuous measurements and correct back to a reference.

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Tau 2
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Re: 2014 machine commissioning and 2015 start up

Post by Tau 2 » Mon Apr 06, 2015 8:59 pm

This overview shows how much they will have to do in these 8 weeks:
http://lhc-commissioning.web.cern.ch/lh ... utline.htm
- Tau

andrewp
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Re: 2014 machine commissioning and 2015 start up

Post by andrewp » Tue Apr 07, 2015 2:26 am

Fantastic. A project planner challenge with all those dependencies and repeated jobs

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Re: 2014 machine commissioning and 2015 start up

Post by Tau 2 » Wed Apr 08, 2015 5:31 pm

Noticing all these BPM rephasings and other adjustments I decided to figure out why all that was necessary.
So I read a few articles about BPM (Beam Position Monitors). Basically it is metal strip parallel to the beam, and when a bunch of protons is passed a very tiny voltage is measured.
The voltage doesn't neatly correspond to the position of the beam at all, it depends on almost everything: energy, intensity, number of bunches, local conditions of the beam line, and so on. :geek:
The best way to measure the position appears to be to average the signal over a number of turns, split the signal it in its frequencies with FFT, and then guess from the relative peak sizes where the beam is.
No wonder that this is hard to calibrate; we'll have to be patient. :yawn:
I wish them luck with all the calculations.
- Tau

andrewp
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Re: 2014 machine commissioning and 2015 start up

Post by andrewp » Fri Apr 10, 2015 1:04 am

A new world record today with beam at 6.5 TeV!

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Tau 2
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Re: 2014 machine commissioning and 2015 start up

Post by Tau 2 » Fri Apr 10, 2015 5:13 am

andrewp wrote:A new world record today with beam at 6.5 TeV!
I tried to attach a picture of it, but the server gave an error. :angry-fire:
This report at least shows a happy team (in the middle of the night):
https://indico.cern.ch/event/385863/con ... ides/1.pdf
- Tau

jmc2000
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Re: 2014 machine commissioning and 2015 start up

Post by jmc2000 » Mon Apr 13, 2015 2:18 pm

Does anyone know what sort of intensity relative to 2012 50ns operation the LHC gurus are aiming for this year?

I believe it might be a further x2 which would give a possible integrated 2fb/week if I'm not mistaken.

Good luck to the guys involved with commissioning and operating the LHC!

Cheers,

Jmc

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Re: 2014 machine commissioning and 2015 start up

Post by jmc2000 » Thu Apr 16, 2015 11:40 pm

jmc2000 wrote:Does anyone know what sort of intensity relative to 2012 50ns operation the LHC gurus are aiming for this year?

I believe it might be a further x2 which would give a possible integrated 2fb/week if I'm not mistaken
According to the previous link given by Tau, the schedule is to initially try 50ns at 4.8E33 similar to 2012 and then 25ns 1.2e34 which is double the intensity. This should yield around 2fb/week, if I'm not mistaken.

Cheers,

Jmc

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