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Interleaved Filling Possibilities. Interleaved Filling Possibilities V. Kain , K. Cornelis, J. Wenninger. Introduction Filling the LHC – nominal concept How will we do it? What is the problem? Cycles for next year Summary. Introduction – Filling the LHC (SPS point of view).

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interleaved filling possibilities
Interleaved Filling Possibilities

Interleaved Filling Possibilities

V. Kain, K. Cornelis, J. Wenninger

  • Introduction
  • Filling the LHC – nominal concept
  • How will we do it?
  • What is the problem?
  • Cycles for next year
  • Summary

Oct 9, 2007

introduction filling the lhc sps point of view
Introduction – Filling the LHC (SPS point of view)
  • 2 different SPS extraction for the 2 LHC rings:
    • LSS6 → TI 2 → beam 1
    • LSS4 → TI 8 → beam 2
  • Nominal filling: 12 injections per ring
  • Can we fill the LHC in an interleaved way?

Oct 9, 2007

slide3

YES…

Can we do it easily, efficiently…?

Oct 9, 2007

introduction sps extractions
Introduction - SPS extractions
  • Large horizontal bump (> 35 mm)
  • Fast extraction kickers (~ 50 kV in LSS4, ~ 30 kV in LSS6)
  • Extraction septa

Example: LSS4

Oct 9, 2007

filling the lhc ideal world nominal concept
Filling the LHC – Ideal World - Nominal Concept
  • The plan (and reality) is
    • The Central Timing System controls the production of the LHC beams in the Injector chain via the CBCM (Central Beam and Cycle Manager)
    • Beams are associated with “users” in the different accelerators to define the magnetic cycles and destinations
    • Static destinations/ dynamic destinations
      • E.g.: LHC beam: static destination: SPS dump, dynamic destination: set on the fly (TI 8 dump, TI 2 dump, TI 8/LHC2, TI 2/ LHC1)
      • Destinations: TI 8/ LHC2, TI 2/LHC1 can only be set by the LHC sequencer
      • Sequencer requests: beam type (number of batches), target RF bucket, ring
  • Hence the required supercycles in the SPS
    • Supercycle: LHC nominal (~ 20 s)
    • Supercycle: FT + 3 CNGS + pilot (~ 43 s)
    • Supercycle: pilot (~ 8 s)

Oct 9, 2007

but we can t do it like this yet
But…we can’t do it like this yet…
  • The SPS power converter control (mugef) is run by the ROCS software
    • The mugefs do not “understand” destination
  • The extraction kickers understand destination
  • Could always pulse both lines plus both extractions….and same scenario as before

 expensive

    • safety issue: the bumps in the SPS
      • in case of problems during extraction (kicker problems,…) risk to damage both extraction channels
  • The ROCS system will go FESA or something similar one day
    • …but not for next year!!!!!!!!

Oct 9, 2007

how will we do it how did we do it
How will we do it? How did we do it?
  • Instead of one LHC user per SPS supercycle and two destinations…
  • 2 LHC users per SPS supercycle (with different destinations)
    • = two LHC cycles per SPS supercycle

Example: this year’s

interleaved extractions

to TT40 and TT60:

2 LHC pilot cycles in the

SPS supercycle. 2 users,

one for LSS4, one for LSS6.

Each transfer line pulsed only

once per SC.

Total length: 16.8 s

Oct 9, 2007

so what is the problem 1
So, what is the problem? (1)
  • Same supercycle, filling only one ring, takes 2 x as long…
  • Could be overcome by changing supercycle in case:

Example: supercycle for

interleaved nominal filling.

Total length: 43.2 s

SFTPRO + pilot

Etc.

LHC nominal

Pilot interleaved

Oct 9, 2007

so what is the problem 2
So, what is the problem? (2)
  • All supercycles have to be ready
    • The timing sequences need to be prepared as well (also for different beam types)
  • To be really efficient: all supercycles should be resident in the hardware
  • BUT….
    • there are not enough users
      • 24
        • already three for CNGS, three for coast, pstart/pstop, SFTPRO,…
    • the ROCS do not have enough memory
  • Change supercyle if cycles resident:
    • 1 – 2 minutes
  • Change supercycle if cycles not resident:
    • up to half an hour

Oct 9, 2007

cycles for next year
Cycles for next year…
  • For next year we can live with the current situation
  • Always resident:
    • Supercycle: FT + 3 CNGS + LHC pilot (length ~ 43 s )…or similar
      • parallel MD cycle ?!?!?
    • Supercycle: LHC pilot(length ~ 8 s)
      • fine for single injections from PS: pilot, one bunch, 4 bunches, 12 bunches, 48 bunches, 72 bunches
      • Low intensity (up to 12 bunches) interleaved: both lines + bumps pulsing
  • Other cycles which will be there, but (probably) not resident:
    • Supercycle: LHC nominal
    • Supercycle: LHC nominal + LHC nominal

Oct 9, 2007

prospect and proposal
Prospect and proposal
  • ROCS will migrate in shutdown 2008/2009
    • next generation software will understand destination
  • We would like to have more users 24 + > 8
    • despite memory limitation in the ROCS
      • Clean up the functions for the corrector magnets

Oct 9, 2007

solution for next year
Solution for next year…

About 1.3 x 1013 protons per extraction

Oct 9, 2007

summary
Summary
  • We can fill the LHC in an interleaved way.
  • Current limitations for efficient and flexible filling of the LHC:
    • SPS mugefs (mainly the extraction bumpers)
  • Solution:
    • Migration of ROCS to FESA or similar (will come)
    • More users, at least 8 more

Oct 9, 2007

additional complexity no showstopper
Additional complexity – no showstopper
  • LSS4: LHC and CNGS extraction
    • MBIs: main dipole chain in TI 8/ CNGS…same power converter
    • Electronic switch: current below 1 % of nominal during beam out
  • Same thing for the MBSG (switch magnet between CNGS and TI 8)
  • Separate beam transfer needs to be defined for TT40
    • Otherwise cannot have CNGS and LHCbeam 2 transfer in the same supercycle
  • CTIMs to be managed by LSA

Oct 9, 2007

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