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V. Kain, SLAC, 16 th -17 th of July 2009 LHC LHC Status & Plans V. Kain, LHC Operations Input from:...
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Transcript of V. Kain, SLAC, 16 th -17 th of July 2009 LHC LHC Status & Plans V. Kain, LHC Operations Input from:...
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LHC
LHC Status & Plans
V. Kain, LHC Operations
Input from: J. Wenninger, F. Zimmermann, R. Assmann, S. Myers, J.P. Koutchouk, L. Evans, A. Verwej, H. Burkhardt....
SLAC SLUO workshop 16th – 17th of July 1
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Outline
Beam Commissioning
September 19th Incident
The cause, the problem...a cure?
2009/10 LHC run
...And beyond – LHC Upgrade
Summary
2
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LHC Cool-down
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First cool-down of LHC sectors
0
50
100
150
200
250
300
12-Nov-2007
10-Dec-2007
07-Jan-2008
04-Feb-2008
03-Mar-2008
31-Mar-2008
28-Apr-2008
26-May-2008
23-Jun-2008
21-Jul-2008
18-Aug-2008
15-Sep-2008
Tem
pera
ture
[K]
ARC56_MAGS_TTAVG.POSST ARC78_MAGS_TTAVG.POSST ARC81_MAGS_TTAVG.POSST ARC23_MAGS_TTAVG.POSST
ARC67_MAGS_TTAVG.POSST ARC34_MAGS_TTAVG.POSST ARC12_MAGS_TTAVG.POSST ARC45_MAGS_TTAVG.POSST
Cool-down time to 1.9 K ~ 4-6 weeks/sector[sector = 1/8 LHC]
All sectors at nominal
temperature
First beam around the LHC
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LHC Hardware Commissioning
February to September 2008o (Re-)commissioning of the magnets & circuits (power converter, quench protection, interlocking..)
following predefined test steps.
o 1’700 circuits, 10’000 magnetso LHC was commissioned to 5.5 TeV (5 TeV target for physics in 2008).
o Magnet re-training required above ~6 TeV.
o Commissioning of other equipment (kickers, instrumentation, RF,…)
4
11’122 test steps
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Injection Tests
August – September 2008
o Injection tests up to 4 adjacent sectors
o Almost all HW systems involved
o Essential checks for:
o Control system
o Beam Instrumentation
o Optics (magnetic model) and aperture
5
22nd – 24th of August
8th – 10th of August 5th – 7th of September
Evening of August 8th 2008:First beam in the LHC after
~25 years of design and construction.
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LHC
September 10th
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LHC
Beam Threadingo Threading by sector:
o One beam at a time AND one beam per hour
o Collimators used to intercept beam (1 bunch, 2 × 109 protons per bunch, 2 % of nominal bunch)
o Beam through sector (1/8 of ring), correct trajectory, move out collimators, carry on.
7
Beam 2 threading BPM availability ~ 99%
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Courtesy of ATLAS
ATLAS & CMS “events”o Beam-on-collimator events, synchronized
to beam timing
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Courtesy of CMS
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Beam Commissioning Progresso September 10th
o 10:30: Beam 1 around the ring (in ~ 1 hour). Beam makes ~ 3 turns
o 15:00: Beam 2 around the ring. Beam makes 3-4 turn
o 22:00: Beam 2 circulates for 100s of turns
o September 11th
o Late evening beam 2 captured by RF.
o First emergency dump correctly executed.
o September 12th
o All basic instrumentation operational: BPMs, BLMs, Tune, BCTs,...
o Good beam lifetime (> 1 hour)
o Beta-beating measured
9
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Magnetic model & beta-beatingo A sophisticated magnetic model (FIDEL) was developed to predict transfer functions and field errors
for all magnets, backed by measurements and integrated into the control system for online corrections.
10
Beta-beat tolerance : 20%
Horizontal beating ≤ 30%Vertical beating up to 90-100%
Dominant source of beating identified as trim quadrupole inversion between beam1 & beam2.
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SEPTEMBER 19TH INCIDENT
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Event sequence on 19th of September
o Last commissioning step on main dipole circuit in Sector 34: ramp to 9.3 kA (5.5 TeV)
o At 8.7 kA an electrical fault developed in the dipole bus bar in the interconnect between Q24.R34 and the neighbouring dipole
o Later correlated to a resistance of that splice in the interconnect of ~ 220 n (0.35 n nominally)
o An electrical arc developed which punctured the He enclosure
o Secondary arcs developed along the circuit
o Around 400 MJ out of the 600 MJ stored in the circuit were dissipated into the coldmass and in electrical arcs.
o Tons of He were released into the insulation vacuum
o Pressure wave along the magnets in the insulation vacuum → collateral damage
12
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Interconnection
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Vac. chamber
Dipole busbar
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LHC
After the incident...
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Dipole bus bar Dipole bus bar
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Collateral damage – pressure waveo He-pressure wave travels along magnet inside insulation vacuum up to vacuum
barriers (every 2 cells)
o Self actuating relief valves could not handle pressure
o Designed for 2 kg He/s: incident ~ 20 kg He/s
o Large forces exerted on vacuum barriers
o Designed for 1.5 bar: incident ~ 8 bar
o Several quadrupoles displaced by ~ 50 cm
o Connection to cryo-line damaged
o Beam vacuum atmospheric pressure
15
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Collateral damage - beam vacuumo Beam vacuum affected over entire length of arc: 2.7 km
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Beam Screen (BS) : The red color is characteristic of a clean copper
surface
BS with some contamination by super-isolation (MLI multi layer
insulation)
BS with soot contamination. The grey color varies depending on the thickness of the soot, from grey to
dark.
Clean surface Covered with MLI flakes~ 60 % of all chambers
Covered with soot.~ 20 % of all chambers
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LHC Repair
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THE CAUSE, THE PROBLEM...A CURE?
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Incident cause: poor quality joint
o Cryogenic measurements indicate local resistance of superconducting cable joint of ~ 220 nOhm in cell where incident occured.
o Simulation of fatal ramp: “thermal runaway at 8700 A”o 1 V detection threshold of “OLD” quench protection system (QPS) not adequate
o → 0.3 mV is required to protect busbars → new QPS system 19
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Busbar quench: current through Cu stabilizer
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Bad connection in Cu stabilizer
→ New QPS does not protect
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o Has to be measured at warm.
Bad Cu stabilizer: bus bar quench
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Measurement at cold: 1.9 Ko Goal for next run: beam energy 4 TeV – 5 TeV
o Splices above inadequate resistance have to be fixed
23
0
2000
4000
6000
8000
10000
12000
10 100 1000
I_ru
n [
A]
R_joint [nOhm]
RRR=240, weak thermal contact (Incident)
RRR=120, no thermal contact (worst case)
0.3 mV
1 mV
0.5 mV
58
5 TeV
Arjan Verweij, TE-MPE, 9 June 2009
25
4 TeV
Cold 1.9K
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Measurement at300 K (80 K)o Copper stabilizers... “simulations are only as good as their input conditions...”
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4000
5000
6000
7000
8000
9000
10000
11000
12000
0 20 40 60 80 100 120
Max
. saf
e cu
rren
t [A
]
R_additional [microOhm]
RB, tau=100 s
RB, tau=68 s
RB, tau=50 s
RQ, tau=30 s
RQ, tau=15 s
Adiabatic conditions, without QPS delay, RRR (bus and cable)=160,cable without bonding at one bus extremity, self field included,no contact between bus stabiliser and joint stabiliser.
Arjan Verweij, TE-MPE, 30 June 2009
7052
4 TeV
5 TeV
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Measurement status & strategyo SC joint measurements: calorimetry (down 40 nOhm), high precision voltage (down
to 1 nOhm) measurements,...
o 3 sectors still to be tested (S34, S23, S45): so far:
o two “bad” internal joints found (50 nOhm, 100 nOhm)
o Cu stabilizers:
o 3 sectors still to be tested (S 23, S 78, S 81): so far:
o MB: 10 joints repaired > 35 Ohm
o MQ: 10 joints repaired > 80 Ohm
o Strategy:
o Measure remaining sectors
o Determine which splices need to be repaired as a function of safe current
o Discuss safe operating energy vs. start-date with beam25
NEW QPS TO PROTECT!
DANGEROUS
IN CASE OF
QUENCH
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LHC RUN 2009/10 - PLANS
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Current Planning
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High cur. powering
Low cur. powering
Cool-Down
o Machine fully hardware-tested end of October.
o First beam end of October.
o ...followed by a long LHC run until November 2010 with a short break around Christmas/New Year.
o Target energy 4 – 5 TeV
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Luminosity Goalso Present 4-stage collimation system limits intensity to ~ 10 % of nominal.
o Operational goals 2009/10
o End of 2010: short Pb ion run foreseen
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No. bunches/beam
Protons/bunch
% of nominalintensity
* (m)Peak L
(cm-2 s-1)
43 51010 0.7 2 6.9x1030
156 51010 2.4 1 5.0x1031
156 11011 4.8 1 2.0x1032
720 (50 ns) 51010 11.1 2 1.2x1032
No crossing angle
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...AND BEYOND – LHC UPGRADEsLHC – Luminosity upgrade
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Upgrade for Nominal - Collimationo Issue: loss of off-momentum particles in the dispersion suppressor right downstream
of collimation zones.
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Coming either 2010/11 or 2013/14
• cryo-collimators
• low impedance collimators → HiRadMat
• in-built BPMs
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LHC Luminosity Upgrade
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o Luminosity upgrade → sLHC
F4
fnN*
n
rb
2
b
L
Limitations:Nb, n injector chain nb electron cloud effectF beam separation schemes insertion
sLHC: Phase I
sLHC: Phase II
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Phase II: 2018
Plans...
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Phase I: 2014
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Phase I and Phase II
o Phase I - 2014
o New NbTi larger apterure triplets, new quadrupole absorbers (TAS), new separation dipoles → * = 25 cm
o Linac4 → ultimate intensity 1.7 × 1011 p+ per bunch
o Luminosity: 3 × 1034 cm-2s-1
o Phase II - 2018:
o Two new injectors: SPL and PS2 → 2x ultimate beam brightness (Nb/)
o New triplets? Nb3Sn? More robust, larger aperture → * = 15 cm
o New separation schemes? Other compensatory measures?
o Luminosity: 1035 cm-2s-1
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Still open questions
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Phase II: new separation scheme required
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for nominal crossing angle(“9.5 σ”), only modest luminosity gain from reduced β*, if notcomplemented by other measures
Crossing angle reduces beam-beam tune shift but also luminosity.
21
1F
y,x
zc
2
Geometric factor
Piwinski angle
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Beam separation schemes/ Compensatory measures: possibilities
o Low emittance: 1- 2m
o Draw back: limited by beam-beam tune shift and IBS
o Work against lumi-decrease from geometric overlap reduction: different possibilities
o Long-range beam-beam compensation
o Early separation: dipole magnets in experiment
o Plus possible crab cavities
o Full crab crossing with dedicated crab cavities
o “Large Piwinski angle” – at beam-beam limit: larger Piwinski angle (and/or larger emittance) increases luminosity: 50 ns, 4.9 × 1011 p+ per bunch
35
SPS wire
Beam-beam compensation
Crab crossing
1.7
-2.3
× 1
01
1 p
er
bu
nch
,2
5 n
s
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Contact Names - Upgradeo http://project-slhc.web.cern.ch/project-slhc/contacts/
o sLHC project leader: L. Evans
o Linac4: M. Vretenar, A. Lombardi
o SPL: R. Garoby, A. Lombardi
o PS2: M. Benedikt, Y. Papaphilippou
o SPS upgrade: E. Shaposhnikova
o IR upgrade (phase I): R. Ostojic, S. Fartoukh: http://slhc-irp1.web.cern.ch/SLHC-IRP1/
o EuCARD Coordinator: J.-P. Koutchouk https://eucard.web.cern.ch/EuCARD/about/
o Crab cavities: J. Tuckmantel, F. Zimmermann
o Collimators: R. Assmann
o High field magnets: L. Rossi
o ....
o Other things:
o Machine protection, operational issues, software,...: J. Wenninger, R. Schmidt, V. Kain
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Summaryo With beam the LHC is a wonderful machine.
o All key systems were operational
o Remarkable performance of the beam instrumentation
o The incident of the 19th of September was most probably due to the poor quality of a bus-bar joint.
o → Quench protection system upgrade
o → Improvement of the pressure relief system
o → Measurement campaign for all splices and stabilizers: systematic problem
o Repair and further measurements are well under way
o We will start-up in autumn this year. The goal is to run until autumn 2010.
o Upgrade: luminosity upgrade in several stages. Different work packages have been defined.
o Collimators need upgrade to go to nominal intensity
o The first upgrade phase is planned for 2014
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RESERVE SLIDES
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Bad surprise...voids in jointso Voids are present in most of the joints. Solder (SnAg) flows out when soldering in
situ.
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Splice and Stabilizer Measurements (Status June 5)
40
Sector Status
on
June 5
2009
Splices
Calorimetric Ohmic
Stabilizers
Biddle R16
Stabilizers
Biddle
1.9K 7kA Warm 80K
Dipoles Quads Dipoles Quads Dipoles Quads
12 warm Done Done Done Done No need No need
23 2K
34 warm Done Done No need No need
45 80K Analysis Problems
56 warm Done Done Done Done No need No need
67 warm Done Done Done Done No need No need
78 40K Done Done
81 40K Done Done