Ramping to 3.5 TeV: time line

March 19, 2010 at 4:05 am 2 comments

Here is a summary of accelerator operations last night:

- 16:30 Started ramp without beam at 2 A/s
- 17:38 Trip of Sector 78 during dry ramp to 6 kA. To be understood.
- Dump during the ramp due to BLM (problem with optical link 
  for BLM in pt1, fixed).
- 20:45 Try a second ramp without beam
- 22:04 Ramp to 3.5 TeV without beam completed. LBDS/BETS OK.
- 00:20 Ready at injection
- 01:45 Injecction started
- Found large chromaticity (negative) and important orbit distortion
  => regenerated sextupole functions (SF SD), much better
- Performed checks:
  * beam1: 
    o Q' Trim : H = -25.0 & V = 0.0, now at H= 5, V= 5
    o Q trim : H only by +0.02. Tunes at 0.28 and 0.31
    o Orbit corrected against "golden"
  * beam2:
    o Q' trim : H by -20.0 & V by +8. Now at H= 10, V= 9
    o Small tune trims to get back to nominal
    o Orbit corrected
- 04:00: Ramp started with buckets 1 (beam1) and 1001 (beam2)
  with tune feedback on, LHCPROBE, ~5e9.
- 05:23: both bams at 3.5 TeV ! 100 hrs lifetime
- At 5:25: RQTF.A81B2, RQTF.A45B2, RQTF.A34B2, RQTF.A23B2 tripped.
  PM indicates that QPS triggered
- Beams dumped properly
- At flat top, aad time to send 50% of an orbit correction on
  both beams, before RQTFs tripped. 
- Tune feedback was on
  * Final Q-FB trims before beam loss: 
    o beam1: dQH = -0.008 , dQV = -0.054
    o beam2: dQH = -0.019 , dQV = -0.066 
  * Tunes at nominal settings after the end of the ramp. 
  * Trims requested to RQT circuits therefore increase and probably
    led to trip of QPS. To be understood.
- Transverse emittances
  * BSRT vs WS Vertical excellent up to ~ 2.5 TeV, then BSRTa
    calibration with D3 light to be studied.
    WS profiles with small sigmas to be looked in detail.
    BSRT vs WS HOR with already seen systematic difference, to be
    understood .

Note the innocuous mention at 05:23 hours: both beams at 3.5 TeV!. As has been pointed out in Cosmic Variance and Not Even Wrong, this is a new world record, far surpassing the beam energies of the Tevatron and the earlier running of the LHC itself. You can also read the CERN Press Release, and a nice upbeat message from Director General Rolf Heuer. Details from the LHC operations center are available at http://cern.ch/lpc.

LHC screen shot

LHC screen shot - 3500 GeV!

Bravo! Now let’s see the beams held for a significant period of time, and then… collisions!


Entry filed under: Particle Physics.

First ATLAS Physics Paper: Charged Particle Multiplicities Twenty-three papers: Commissioning CMS

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