Transcript Chamonix 2011 - Energy Session

Beam Energy
(to increase or not to increase)
Andrzej Siemko and Marco Zanetti
Chamonix 2011 – Beam Energy Session
What has changed since last year?
● Increase of knowledge of copper bus bar segments:
– Measurements of RRR in the whole machine justify to assume in the
simulations significantly higher RRR (RRR=200 instead of RRR=100)
● Increase of knowledge of the resistance of superconducting
splices:
– Contrary to copper joints, the superconducting splices are very good
(Rmax = 2.7nΩ for main dipoles and Rmax = 3.2nΩ for main quads)
● Arjan’s simulation of burnout limits:
– quenches due to heat conduction through the busbar, including heat
generated due to by-pass diodes, have been studied in detail (this had not
been studied last year) and give somewhat lower limits
Chamonix 2011 – Beam Energy Session
A. Siemko
What has changed since last year?
crease of knowledge of consequences of a hypothetical incident
different sectors (with beam energy up to 5 TeV)
The present consolidation, up to 5 TeV, suppresses mechanical collateral
damages in adjacent sub-sectors
Nevertheless damage of the MLI and contamination of the beam pipe(s)
could require heavy repair work (8 to 12 months)
L. Tavian
Chamonix 2011 – Beam Energy Session
A. Siemko
Discoveries in the next LHC run
● Increase of feeling of discoveries in reach from experiments
(thanks to successful first year of LHC operation)
● At 8 (7) TeV CMS/ATLAS will have 3σ sensitivity for the Higgs in
the whole mass range with 5 (6) fb-1
– The discovery potentials
for the main physics
objectives increase not
only as a function of
integrated luminosity
but also as a function of
center of mass energy
– Statistics (lumi) is
critical, increase in
energy is beneficial
W. Murray
Chamonix 2011 – Beam Energy Session
A. Siemko
1 quench/week
1 quench/month
Burn-out probability
Pyear = NM * (PG+PB) + NJ * PJ  NM*(PG+PB)
Probability per year
for joint burn out
Number of dipole
quenches per year
Chamonix 2011 – Beam Energy Session
(NJ << NM)
Asynchronous beam
Number of prompt joint dump inducing series of
quenches per year
quenches under study
A. Siemko
Hardware constraints
● Reduction (better elimination) of high current quenching is
crucial, both at 3.5 TeV and 4 TeV
– Quenching due to UFO phenomenon can show up with increasing beam
intensity and energy
– Transient EM perturbation must be reduced  snubber capacitors should
be commissioned a.s.a.p. (extra one week)
– Reviewed HV withstand
levels, including crosstalk between circuits
need to be applied in
future
– No other critical
hardware constraints
(NCRs) impacting on
operation up to 4 TeV
J. Steckert
Chamonix 2011 – Beam Energy Session
N. Catalan-Lasheras
A. Siemko
Hardware constraints
IRB
5.0
TeV
8500A
4.5TeV
7650A
Beam energy
(dipole current)
Circuit
Protection
limits
Splice risk
4.0
TeV
6800A
4TeV,
52 s
3.5
TeV
6000A
present
4TeV,
68 s
Risk of burning an
interconnect during a
quench
τ
34
s
52
s
68
104s
Time constant
s
Plot only for visualization, not to scale !
J. Steckert
Chamonix 2011 – Beam Energy Session
4/11/2017
A. Siemko
Operational constraints
● Given any HWC/QPS/MP3 overheads
● Starting a new year at a new energy is almost cost free
– Full setup from scratch planned anyway
● During run - with squeeze re-scaling
– Around 1 week re-commissioning
– Pre-flight checks in MD could be useful
● Without squeeze re-scaling
– Collimator setup – around 2 weeks re-commissioning
● To be able to make up for lost time – don’t leave it too late.
● Or run the whole year at 3.5 TeV
M. Lamont
Chamonix 2011 – Beam Energy Session
A. Siemko
Copper Stabilizer Continuity Measurements
(a.k.a. “Thermal Amplifier”)
● The current safe energy analysis is based on a lot of assumptions
– Mostly conservative
● The CSCM is a qualification tool that measures in situ the copper
busbar resistance and thus can qualify a sector to the maximum
current it can safely withstand.
● Feasibility study successfully performed in 2010.
REAL DATA
2.7kA pulses at 41K
The GREEN
voltage contains a
50uOhm defect.
The BLUE and
RED voltages are
across perfect
joints
M. Koratzinos
Chamonix 2011 – Beam Energy Session
RB: a typical
bad joint has
excess
resistance of
2% - if we warm
it up, its
resistance
grows by ~200
times – easy to
detect!
A. Siemko
Recommendation
● To allocate the resources and to launch a.s.a.p. the:
Copper Stabilizer Continuity Measurements Project
(CSCM)
● With the aim to be ready to measure the copper stabilizers in the
machine during 2011/2012 year-end stop
● Only the ‘CSCM’ in all sectors can qualify the safe operating
current in situ
Chamonix 2011 – Beam Energy Session
A. Siemko
To increase or not to increase
● From main magnet circuit protection point of view, a scenario with
3.5 TeV in 2011, CSCM during 2011/2012 stop and then higher
energy (defined by CSCM) run over 2012 is the minimum risk
scenario of splice burn-out
● Our present knowledge do not prevent running LHC up to 4 TeV per
beam. There is no hard show-stopper neither for the hardware nor
for OP to start the run at 4 TeV with 52 s energy extraction time
constant, however:
– the risk of splice burn-out significantly increases (factor 5)
– hardware parameters are pushed to the limits
– number of quenches to reach predefined incident probability is very
limited (less then 2 for P=0.1%), may need to reduce the energy during
the run
● 4 TeV/68s and 4.5 TeV/68s are much to risky
Chamonix 2011 – Beam Energy Session
A. Siemko
My personal point of view
Chamonix 2011 – Beam Energy Session
A. Siemko