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Evian summary 124-1-2011
Operational challenges(Feed forward from Evian LHC operation workshop)
7-9 December 2010
Day after last beam
Two nights – 7 sessions
LHC beam operation: review of 2010 and
setting the scene for 2011
Experiments, efficiency, beam from injectors,
75 & 50 ns, intensity ramp up, RF
Driving the LHC
Turnaround, software, magnetic model,
missing functionality
Beam diagnostics and feedback systems
Bunch by bunch, feedbacks, transverse
damper, BPMs, transverse beam size
Evian – Sessions
24-1-2011 2Evian summary
Machine protection systems
MPS performance, LDBS, abort gap,
minimum beta*, injection protection, the
human factor
Beam losses
Collimation, 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
24-1-2011 4Evian summary
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 summary
Giulia 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
24-1-2011 6Evian summary
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
24-1-2011 7Evian summary
Resources
S3: RF, beam diagnostics and feedback systems
Evian summary 824-1-2011
• 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
Evian summary 924-1-2011
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
24-1-2011 10Evian summary
Ralph Steinhagen
Tune feedback in the ramp
Evian summary 1124-1-2011
BBQ versus ADT
Evian summary 1224-1-2011
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
Evian summary 1324-1-2011
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 summary
Eva 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
24-1-2011 15Evian summary
F. Roncarolo
Essential - need bunch by bunch - getting there
S4: Machine protection
Evian summary 1624-1-2011
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
CERNCERN
[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
Evian summary 1824-1-2011
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
Evian summary 2124-1-2011
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
24-1-2011 22Evian summary
Barbara Holzer
BLM thresholds
Evian summary 2324-1-2011
Detailed analysis presented by Annika!
Annika Nordt
Correlations between collimator movements, vacuum and beam losses
LUMINOSITY PERFORMANCE
Excellent performance
Stability 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.
Evian summary 2424-1-2011
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
24-1-2011 25Evian summary
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
24-1-2011 26Evian summary
Gianluigi Arduini
The hump is there all the time
Evian summary 2724-1-2011
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
Evian summary 2824-1-2011
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
24-1-2011 29Evian summary
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
24-1-2011 30Evian summary
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….
24-1-2011 31Evian summary
Very much appreciated!
Evian summary 3224-1-2011
Thanks to CMS
Evian summary 3324-1-2011