Evian summary 1 24-1-2011 Operational challenges (Feed forward from Evian LHC operation workshop)...

Evian summary 124-1-2011

Operational challenges(Feed forward from Evian LHC operation workshop)

7-9 December 2010Day after last beamTwo nights – 7 sessions

LHC beam operation: review of 2010 and setting the scene for 2011Experiments, efficiency, beam from injectors,

75 & 50 ns, intensity ramp up, RF Driving the LHC

Turnaround, software, magnetic model, missing functionality

Beam diagnostics and feedback systemsBunch by bunch, feedbacks, transverse

damper, BPMs, transverse beam size

Evian – Sessions

24-1-2011 2Evian summary

Machine protection systemsMPS performance, LDBS, abort gap,

minimum beta*, injection protection, the human factor

Beam lossesCollimation, injection, extraction, UFOs, BLM

thresholds Luminosity performance & wrap-up

Emittance preservation, the hump, beam-beam, luminosity optimization, optics, pushing the limits in 2011, 2011 projections

Evian – Sessions

3Evian summary24-1-2011

Improved machine availability Turn around optimization Beam quality and availability from injectors Machine safety & the human factor Software and controls Magnet model

Sessions 1 & 2: Operations


For all these: lessons learnt, improvements being made

2010: pretty good going

Operations bedded in but there is room for improvement

Clear procedures needed (scraping, blow-up etc.) Preparation in good time, check lists

Must be able to track beam quality through the injectors Emittances, intensities etc.

LHC request must be clearly communicated in good time Talk to your suppliers

Nice long list of RF improvements in the SPS Dedicated LHC filling to be pursued

Beam quality and availability from the injectors

24-1-2011 5Evian summaryGiulia Papotti

Transverse and longitudinal characteristics very important

Go dynamic with b3 compensation at injection ~2 units of decay, as expected by FiDeL, but on much longer

time constant Measure & deploy dynamic correction. Rollback decay driven trims before starting each injection

Tune decay at injection Remove hysteresis handling in squeeze Ramp-down settings for access to avoid pre-cycle

afterwards Chromaticity during ramp

Tracked within ±7 units – we can improve the initial part

Magnetic model/cycle and its effects


Ezio Todesco

..today we have the most complex and comprehensive field forecast system ever implemented in a superconducting accelerator

Luca Bottura 2008

LHC: 5.4 GCHF investment Around 299 MCF/year P & M budget Understandable desire to capitalize on investment Route 1: long operational years

Human factor: Operations and infrastructure teams with limited manpower Stretched in some areas - not only the LHC

The human factor


Resources

S3: RF, beam diagnostics and feedback systems


• Interaction of Q-feedback and TFB

• BPMs in interaction region

• BPM intensity dependence

• Reliable bunch by bunch beam size measurement through the cycle

Key systems have performed with a remarkable degree of maturity – inevitably some improvements possible:

Beam based feedbacks – tune, orbit

Transverse feedback

RF

Beam instrumentation: BPMs, BLMs, beam size measurement…

Transverse Feedback


commissioned damper at 450 GeV, during ramp and with colliding beams

nominal damping rate reached and surpased

commissioned operation with bunch train

commissioned damper for ions at 450 GeV and with colliding ion beams

abort gap cleaning and injection slot cleaning successfully used

diagnostics (logging, fixed display, multi-bunch acquisition) available

Lots incoming in 2011 Tune measurement options listed. Strategy to be defined.

Wolfgang Hofle

Feedbacks performed well and facilitated a fast commissioning de-facto required during every ramp and squeeze with nominal

beam and expect the same also for next year additional safety margin to operation provided feed-forward is

performed regularly Good overall performance with little transmission losses

and minimal hiccups related to Q/Q' instrumentation, diagnostics and Q/Q' & orbit feedbacks This year's 1% losses may become more critical in 2011

Tune, Orbit feedbacks


Ralph Steinhagen

Tune feedback in the ramp


BBQ versus ADT


Effective ADT noise floor and observed bunch-to-bunch cross-talk hinders reliable operation of LHC's Q/Q’-diagnostics and related feedbacks

Scenario for gain


The global performance of the system is very good – 97% channel availability

Number of improvements through the year including temperature calibration/compensation

Synchronous mode 2011 will solve double trigger issue on IR BPMs Orbit on selected bunches

IR BPMs: cable adapters will be installed this XMAS stop Pre-flight checks with beam

Testing acquisition and calibration Intensity dependence cross-over

B1 behavior was caused by a small impedance mismatch at the input of the intensity module.

Replacing the intensity card by termination card in IRs

BPMs: status, measurement reliability and outlook for 2011

24-1-2011 14Evian summaryEva Calvo

Wire scanners Turn and bunch-to-bunch Reference but take care

BSRT DC and pulsed mode Resolution – optics; Accuracy via x-calibration with WS – correction factors not

stable Absolute calibration and ultimate resolution: still to be studied Complicated in ramp – change of focusing etc. Bunch by bunch, turn by turn incoming – fast camera

BGI is in commissioning phase relative accuracy reliable once beam profile quality has been checked absolute calibration to be studied to complement cross-calibration with bumps 2011: gas inj. remote control, better camera control

Transverse beam size


F. Roncarolo

Essential - need bunch by bunch - getting there

S4: Machine protection


Machine protection system has functioned remarkably well – long list of improvements for 2011

LBDS performing well

Injection protection – some issues

Intensity ramp up strategy in 2010 was well judged

Motherhood statement: continue to take it seriously

Injection protection - injecting unsafe beam into the LHC

Enforcing a more rigorous approach at injection > 500 kJ

Ramping up intensity – clear strategy for 2011 required

CERN

[email protected] LHC beam commissioning Workshop - Evian

Main challenges during 2010 run (> injection)

SIS (TCDQ Position, missing energy)Magnet Powering (Orbit Feedback, etc..)

Collimator interlocks during ramp

Magnet Powering (OFB/QFB, QPS sector trip, ..)

Loss Maps, Collimator setup, Fast losses

ATLAS

Magnet Powering (Mostly PC issues + FB, CRYO,..)Fast losses, loss maps,… SW Permits (TCDQ position, trip of DOCs)

Loss maps, wire scanner tests, collimators moving… SW Permits (TCDQ position,…)

Magnet Powering (Mostly PC issues, …)

>> Fast Losses (UFOs) Magnet Powering (QPS, CRYO, PC,.. )SW Permit (Orbit, BLM lost in IR7…)Electrical Perturbations

Beam dumps as a function of beam mode for fills where energy ramp started and main causes of loosing the beams…

17

MPS system response - summary


LHC Machine Protection Systems have been working extremely well during 2010 run thanks to a lot of commitment and rigor of operation crews and MPS

experts

Most failures are captured before effects on beam are seen, still no quenches with circulating beam (with ~ 30MJ per beam and 10mJ for quenching a

magnet)

Beam dumps above injection are rigorously analyzed, we can do better at injection (avoiding repetitive tries without identifying the cause)

Still a lot of room for improving tools for more efficient and automated analysis

No evidence of major loopholes or uncovered risks, but bypassing of protection layers was/is still possible -> Follow-up of MPS Review recommendations

Still we have to remain vigilant to maintain current level of dependability of MPS systems, especially when entering longer periods of ‘stable running’

Markus Zerlauth

LBDS: Faults Occurred During 2010 run

1 energy tracking error at 3.5 TeV due to instabilities of 35 kV power supplies beam dump (30/03/2010: media day)

Asynchronous beam dump, during energy scan without beam (due to spark on the outside of the gate turn-off GTO thyristor):

1 at 5 TeV 2 at 7 TeV

4 internal triggers due to vacuum interlocks on the MKB for B2 FALSE vacuum pressure reading – logic now changed to use only VAC

signal

1 Asynchronous beam dump with beam

2 beam dumps induced by TCDQ faults

12/08/2010

Safe margin for 3.5 TeV operation, isolators implemented during technical stops (starting in

January 2011 finished during 2012 TS)

Number of total dump system failures (unacceptable):1 every 1000000 years

Chiara Bracco

LBDS failures occurrence in agreement and not worse than requirements and expectations No damage or quench during synchronous and asynchronous

beam dumps Leakage to downstream elements within specifications TCDQ needs TLC – long-term plans to define

Machine protection validation tests, procedures and tests frequency: Is this adequate? (too often, too rarely) Could tests be improved? Do they really insure machine safety?

LBDS

24-1-2011 20Evian summaryChiara Bracco

BEAM LOSSES


Excellent performance of collimation system - no quenches

BLMs – great job – thresholds always a consideration

Issues at injection with fast losses

Watch extraction losses

UFOs

BLM thresholds at critical locations

UFOs Triplet, IRs and arcs Scaling with total intensity – extrapolations look worrying Don’t appear to get harder with intensity Loss duration falls with intensity Interestingly – hot and cold regions out there Maximize UFO acceptance by threshold adjustment

BLM hardware failures Acceptable!

Losses away from collimators: statistics and extrapolation


Barbara Holzer

BLM thresholds


Detailed analysis presented by Annika!

Annika Nordt

Correlations between collimator movements, vacuum and beam losses

LUMINOSITY PERFORMANCE

Excellent performanceStability and reproducibility: orbit, optics

Intensity and emittance from injectors

Benign beam-beam

Collimation has performed very well – projected limits for beta* presented. No limits on beam intensity in 2011.


Optics – measurement and correction

Emittance preservation through the cycle – the hump

Bunch by bunch diagnostics

Beam quality from injectors: intensity, emittance

Luminosity calibration

Beam-beam

Beating at injection, during squeeze well corrected 3.5 m.

10% achieved! Slightly worse with LSA… not driving IR3,4,6 and 7 Hysteresis handling – 10% beating at 1.5 m. – we will desist

Excellent long-term stability! Non-negligible drift 8% observed at injection Beatings going to get worse, but correctable IR coupling correction mandatory below 2 m.

Optics


Rogelio Tomas Garcia

The hump affects luminosity performance due to blow-up (particularly at 450 GeV). In collision it can excite beam-beam coherent modes or generate tails and therefore losses

Mitigation: low noise TFB at maximum gain Since middle of November turn-by-turn/bunch-by-bunch

position with damper pick-up. Ion filling scheme with basic spacing of 500 ns possibility of determining the frequency of the hump ±f0+n x 2 MHz with 0<f0<1 MHz fhump < 10 MHz

The identification (and possibly eradication) of the origin remain the (challenging) goal of the ongoing analysis and measurements.

The hump is there all the time


Gianluigi Arduini

The hump is there all the time


2011 INCOMING

Energy?

Squeezing further - minimum beta*

LHCb ”Luminosity leveling”, beta’s at Alice and LHCb

150 vs. 75 vs. 50 ns. - beam from injectors, start-up strategy


Electron cloud: heat load, vacuum, scrubbing, monitoring

UFOs

R2E

Beam-beam – pushing the limits

All to be covered in detail at this workshop

Come a phenomenally long way in 9 months Notable feature - remarkable maturity of some key

systems after just a year It hasn’t come for free It’s been years in the preparation Devil is, as always, in the details, lots to follow-up

Possible improvements, consolidation detailed for all systems

2011 clearly aims to leverage off of what’s been learnt this year

With some known problems incoming: UFOs, electron cloud, R2E…

We’ll be pushing up Ralph’s stored energy plot LET’S TRY NOT TO BREAK IT!

Conclusions


Chairpersons Roger, Gianluigi, Jorg, Brennan, Ralph, Malika

Scientific secretaries Giulia, Mirko, Reyes, Alick, Stefano, Verena

Speakers Lot of hard work at the end of a hard year

Workshop secretariat Sylvia Dubourg, Flora Meric

Technical support Pierre Charrue

Brains, organization and determination Malika Meddahi

Editor of proceedings Brennan Goddard

Steve and Paul for their support

Acknowledgements


ATLAS: highlights from the first run Fabiola Gianotti

ALICE: The 2010 LHC Experience Werner Riegler, on behalf of Jurgen Schukraft

CMS 2010 and Prospects for 2011-12 Tiziano Camporesi, on behalf of Guido Tonelli

Compliments to LHC from LHCb Andrei Golutvin

Special thanks….


Very much appreciated!


Thanks to CMS

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