Current Events Discussion

[Bornerdogge]

That would certainly be useful... There are 7 bunches of ~1e11 now, and stable beams!

[jmayes]

Wow, and I thought my house was bad to reboot after a power glitch...

"While ramping down the machine, there was a general power cut (on the 66kV) that tripped all sectors. The power cut was at 23:20:43 and lasted for ~10-15sec. Cryo conditions were lost in all sectors except S56 and S67. All experimental magnets also tripped.

- Status after power cut
- RF:Pumps for beam and isolation vacuum for the cavities were restarted. All RF power equipment was restarted (except HV)
- Kickers: LBDS came back without problems from power cut. MKI's recovered, but may need intervention on apower supply.
- Vacuum: All valves closed at the power cut. Piquet quickly restarted pumps and gauges. Access needed for vacuum gauge power supply (VGP.78.5R8)
- Collimators: Piquet could clear all faults and we moved them to parking position
- Acces: Access system seems opperational but there is one 48Vdcc supply that needs to be checked
- MP3/QPS: All switches are closed and controllers have been reset. QPS_OK is back for all converters exept some circuits that need PO intervention
-EPC: They have ~20 converters that need to be checked

At 03:08 Access in UX45 was given to cryo team accopanied by firemen to reset cryo crates and ODH alarms at

From MP3: it first seemed that one or more magnets may have quenched after the power cut, but it now seems that the power cut triggered heaters to fire.".

Reboot operations are still on-going, now almost 2 days later. Atleast no real damage but still alot of circuits that did not recover and need personal attention.

[CharmQuark]

I'm so pleased there is no real damage

[tswsl1989]

I suppose the good points are that they don't have these issues often, and that they'll probably be able to respond faster should there be another general power cut.

[Harbles]

But sad timing as the few days of stable beams were lost and now a 3 day planned maintenance outage.
If it was easy everybody would be doing it I suppose.

[Sphereix8]

I have to say it sounds like a reasonably quick recovery given the complexity of the machine. I just returned from Peru where it can take twice as long to get a meal at a restaurant.

[Bornerdogge]

There we go! The LHC is back online!

The experiments are headingfor a busy weekend: 3 days with 13 bunches/beam...

[PhilG]

An important progress update is available at http://indico.cern.ch/getFile.py/access ... nfId=97708

They have now abandoned the 13 bunch low intensity physics runs because it was too much hassle to run those interspersed with commissioning for higher intensity bunches. The new plan as of Wednesday is to concentrate on the higher intensity bunches with the possibility of better physics runs in two weeks time if all goes well. beta will be set at 3.5m and they aim to get to 20 or 40 bunches before settling in for a concentrated month of physics runs in August.

All the details you can eat in the report above.

Next change of plan is planned for next week

[Kasuha]

So they even have plan changes planned?

[DCWhitworth]

So they even have plan changes planned?

If you have a change of plan planned is it still a change of plan ?

[CharmQuark]

So they even have plan changes planned?

If you have a change of plan planned is it still a change of plan ?

mind boggling that is

[Bornerdogge]

So they even have plan changes planned?

If you have a change of plan planned is it still a change of plan ?

I'd say yes, as you don't know yet what you're gonna change ^^

(In a railway station not far from here, they have a special board with the planned delays of train departures ^^ Don't try to understand the Belgian rail services )

[mrgumby]

just as long as they don't plan to change their plan to change their plan changing plans.

[PhilG]

More details of the current plan can be found in this talk on short to medium term planning where medium term means 10 years!:
https://indico.desy.de/contributionDisp ... onfId=1964

There have been no physics runs for about three weeks now. If they can achieve smooth running with nominal bunches (100 billion protons) they should be able to restart physics runs within a couple of weeks. If nominal bunches are too hard they may settle for less e.g. 80 billion protons. The plan for increasing number of bunches during the rest of this year is then as shown in the attached table.

Nb = number of bunches
Nc = number of collisions per turn in each experiment
Ib = number of protons per bunch
Itot = Ib x Nb
MJ = total energy of beams in Mega Joules. (not safe for machine above 1 MJ)
Increase = increase factor of stored energy (not luminosity)
Peak lumi = maximum possible luminosity (what matters)
Days = number of days they hope to do physics runs for at each step
Int. Lumi = estimate for integrated luminosity if it runs smoothly at each step (what really matters)

[Bornerdogge]

What's the unit of the integrated lumi? (pb)^-1?

Haha slide 2 made me laugh... "It's a lot easier to inject a lot of high intensity bunches into an equation than into a particle accelerator"


I have a question... When they say "separation on", they do actually mean the beams don't collide don't they?