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Machine development - results and plans – critical results, what’s to be done?
R. Assmann15/07/2011
R. Assmann
for the LHC MD coordination team (R. Assmann, Frank Zimmermann, Giulia Papotti)
See LSWG presentations of MD teams and the ATS MD notes for details!
http://www.cern.ch/lhc-md
R. Assmann15/07/2011
LHC-MD web site holds detailed info, ATS MD notes by the teams, MD requests, LSWG minutes and presentations, ...
Here I will be generic, focusing on issues relevant for this meeting!
MD Results: Bunch Intensity and Emittance
R. Assmann15/07/2011
MD Results: Bunch Intensity and Emittance
R. Assmann15/07/2011
Isolumi lines give luminosity per colliding bunch in IP1/5 (3.5 TeV, 1.5m beta*) Multiply with number of colliding bunches to get total peak luminosity!
Reached: Luminosity per coll. Bunch (IP1/5)
R. Assmann15/07/2011
1.00E+11 1.10E+11 1.20E+11 1.30E+110.5
1
1.5
Bunch Intensity
Lu
min
osi
ty p
er c
oll
idin
g b
un
ch
[103
0 cm
-2 s
-1]
Reached: Luminosity per coll. Bunch (IP1/5)
R. Assmann15/07/2011
1.00E+11 1.10E+11 1.20E+11 1.30E+110.5
1
1.5
Bunch Intensity
Lu
min
osi
ty p
er c
oll
idin
g b
un
ch
[103
0 cm
-2 s
-1]
Iso-luminosity („isolumi“) lines calculated based on this performance!
MD Results: Bunch Intensity and Emittance
R. Assmann15/07/2011
Collimation MD‘s: Very high bunch charges OK at 3.5 TeV for up to 2808 bunches. No limit on number of bunches!
MD Results: Bunch Intensity and Emittance
R. Assmann15/07/2011
WP‘s ~OK in LHC.Can be used with same machine configuration... Also OK for long-range beam-beam!
MD Results: Bunch Intensity and Emittance
R. Assmann15/07/2011
25ns requires further commissioning work
Assume 1.2 mm mrad minimum emittance
R. Assmann15/07/2011
Not feasible
Optimal performance improvement
R. Assmann15/07/2011
Movement orthogonal to isolumi lines looks optimal!
Optimal performance improvement
R. Assmann15/07/2011
Small emittance could be used to later reduce beta* to 1m and to gain further.
Injection limit on high emittance
R. Assmann15/07/2011
Robustness limit from TCDQ
R. Assmann15/07/2011
Intensity Limit for Smallish Emittance
R. Assmann15/07/2011
Exclude Region with Lower Luminosity
R. Assmann15/07/2011
Room for Improvements
R. Assmann15/07/2011
Room for Improvements (LHC only)
R. Assmann15/07/2011
Room for Improvements (with injector limit)
R. Assmann15/07/2011
Bettina‘s talk
Room for Improvements (LHC only)
R. Assmann15/07/2011
Most efficient in view of limits: Increase bunch intensity for the same emittance. Gain of factor 4 is possible!
Room for Improvements: Beta*
Optics MD‘s (90m, ATS) very successful: Demonstrates efficiency in increasing/reducing beta*. Optics errors small and controllable. No major problem from non-linearities even for very small beta* (0.3m
with ATS) reduces overhead for squeezing further. Beta* can be reduced to 1m ( Roderik). Smaller beta* requires tight collimation settings:
Machine in a different regime (impedance). Would be useful to test this year to see whether this is workable with
high intensity. If successful, could use it as baseline for 2012.
R. Assmann15/07/2011
Addressing LHC limits in MD‘s I
Small transverse emittance and bunch length emittance growth can become limiting: Mechanisms for emittance growth in the LHC Longitudinal instabilities Understanding diffusion process, when beams are brought into
collision. IBS, longer bunch length, noise of transverse damper, ...
High bunch charge effects: Instabilities Emittance growth versus bunch intensity Luminosity lifetime
Many of these issues only seen in long stable physics fills
Beneficial to push bunch intensity and emittance early to learn about the most important problems. Then study in MD!
R. Assmann15/07/2011
Addressing LHC limits in MD‘s II
Beam-beam limits: Not yet for head-on. Continue exploring it. Study as function of noise? Further tests on long-range beam-beam, versus emittance and bunch
spacing, … Tight collimation settings and impedance:
High current MD with robust (CFC) collimators moving in Most efficient: end of fill MD go to adjust mode after end of long,
high intensity physics fill Lower beta*:
Tight collimation settings, low beta* and protection can be tested (partly) in MD (no new collimation setup)
More bunches 25 ns: Longer trains, e-cloud, beam-beam effects, ... Goal: Firm plan and time line for 25 ns scrubbing run
R. Assmann15/07/2011
Addressing LHC limits in MD‘s III
Beam instrumentation: Smaller emittance requires better calibration, for example to be sure
about emittance growth Intensity dependent effects Bunch by bunch variation stronger close to limit
Quench limits: Tests at 3.5 TeV to further determine quench limit in dispersion-
suppressors and maximum BLM threshold. Tests at injection conclusive or more
Heating effects: Determine longest acceptable bunch length in LHC. Dependence of heating effects on size of “cavity” (can be studied with
movable collimator jaws).
R. Assmann15/07/2011
Addressing LHC limits in MD‘s IV
UFO mechanism: Understand mechanism at the injection kickers, which have 100 times
higher rate than other locations UFO’s faster than gravity acceleration towards beam (really?) or
evidence for EM effect? Injection limits:
Extracting beam with Q20 optics in SPS and inject into LHC long-term program
R. Assmann15/07/2011
Addressing LHC limits in HiRadMat
Robustness limits of LHC collimators and protection devices: Cannot be addressed in the LHC with beam tests. Very expensive to learn about damage limits by trial and error in the
LHC. This is why the HiRadMat test facility was proposed and constructed.
HiRadMat tests for addressing robustness limits in LHC: TCT limits for catastrophic damage propose to equip one spare
TCT for a destructive test in HiRadMat. CFC and C collimators: HiRadMat beam parameters allow to test with
higher power densities than in 2004 and 2006. Push test intensity to gain margin!
TCDQ: ?
R. Assmann15/07/2011
Comments and Feedbacks Welcome...
Outcome of Mini-Chamonix will impact plans for next MD‘s Start discussing draft plan for end-of-August MD next week...
R. Assmann15/07/2011
Reached: Number of bunches
R. Assmann15/07/2011
0
500
1000
1500
Date
Nu
mb
er
of
bu
nc
he
s [
p]
Reached: Bunch intensity
R. Assmann15/07/2011
0.00E+00
2.00E+10
4.00E+10
6.00E+10
8.00E+10
1.00E+11
1.20E+11
1.40E+11
Date
Bu
nc
h I
nte
ns
ity
[p
]
Reached: Peak luminosity
R. Assmann15/07/2011
0
500
1000
1500
Date
Pe
ak
Lu
min
os
ity
[1
03
0 c
m-2
s-1
]
Reached: Stored energy
R. Assmann15/07/2011
0.00
20.00
40.00
60.00
80.00
100.00
Date
Sto
red
En
erg
y [
MJ
]
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