1. 2016 Chamonix Workshop Summary of the HL-LHC Session
O. Brüning
CERN, February 24, 2016

2. HL-LHC Sessions @ Chamonix
Not a Status Report of all Work Packages:
Rather:
Discuss WPs where experience from the first year RunII oper.
has an impact on the HL-LHC implementation and operation
Discuss topics where decisions are pending
Clarify the paths for implementing options and baseline choices
Work Packages that are not covered are assumed to be on track
7 Presentations:
2 focusing on the path for HL-LHC hardware implementations
3 on LHC post LS2 operation with LIU parameters,
1 on required HL-LHC tests in the SPS,
1 on Civil Engineering aspects for constructing the HL-LHC
infrastructure
High light scope of the HL-LHC session: pending decisions, impact of 2015 operation on HL-LHC, revision and down selection of Options
O. Brüning, Chamonix Summary CERN, March 3rd

3. HL-LHC Sessions @ Chamonix
Performance Limitations in the LHC after LIU upgrade:
G. Arduini  e-cloud, UFOs, Z & instabilities, aperture, BI
RF Upgrade Paths:
E. Jensen  200MHz and 800MHz options, feedback
Collimation Upgrade Path for the HL-LHC:
S. Redaelli  quench tests, materials, radiation, DS collimation
Crab Cavity Test Installation in the SPS:
G. Vandoni  location, infrastructure requirements, schedule
Coating Operation for the insertion magnets in IR2 & IR8:
P. Costa Pinto  aC coating and laser surface treatment
Vibration Studies and Tolerances for the Operation: J. Wenninger  test drills, shaker, Geotherm2020, earth quakes
Ion Operation after LS2:
J. Jowett  LIU prospects, L sharing options, 2015 MDs
O. Brüning, Chamonix Summary CERN, March 3rd

4. HL-LHC Sessions @ Chamonix
Performance Limitations in the LHC after LIU upgrade:
Different heat load in the LHC sectors  2 different classes
 impact on scrubbing campaign
E-cloud heat load ≈ constant as function of bunch intensity for
SEY ≤ 1.3 and N > nominal
 if we can condition the LHC
up to nominal intensities the machine is good for HL-LHC
Coating of IR2 & IR8 IR quadrupoles is mandatory!
Luminosity limitation in IR1 & IR5 due to heat exchanger and Cryo
Is important to push current in the LHC after LS2 up to HL-LHC
values in order to identify potential current limitations before LS3
in order to discover and identify potential other bottlenecks!
2 categories for LHC cryo sections?! Conditioning to nominal intensity is sufficient for HL-LHC, interest in operating at HL-LHC intensities before LS3!
O. Brüning, Chamonix Summary CERN, March 3rd

5. Beam parameters after LIU (SPS ext.)
Assuming measures for SPS long. Impedance reduction are implemented
Parameter
Before LIU (2016)
After LIU
Bunch population Nb [1011]
1.3
2.3
Max. number of bunches per SPS ext.
288
Normalized emittance en [mm]
2.7
2.0
eL [eVs]
0.66
r.m.s. bunch length [cm] 12
#bunches
Bunch population [1011]
Lev. time
[h]
Opt. Fill length
Peak Lumi
[1034 cm-2s-1]
Int. Lumi for for opt. fill length
[fb-1 /y]
Pile-up density/Pile-up
[ev./mm]/
[ev./xing]
2748
1.5
5.5
9.8
1.7 80
0.54/45
1800
2.0
11.5 14
1.25 70
0.6/50
Impressive progress in the understanding of the origin of longitudinal coupled bunch instabilities:
Shielding of the MBA-QF flanges + damping of the TWC 200 MHz at 630 MHz should allow reaching HL-LHC parameters  will be included in the baseline. Need of enamelled flanges should be assessed.
MKP shielding would solve the issues related to heating
Corresponding reduction of the transverse impedance and TMCI thresholds should be evaluated in view of using Q22 or Q26 optics to provide additional longitudinal acceptance at flat top and possibly reduce peak dispersion (and losses)
Need to determine rise-time for transverse coupled bunch instabilities due to impedance and study interplay with electron cloud for the coupled bunch instabilities observed in the horizontal plane
G. Arduini - Performance Limitations in LHC after LIU Upgrade

6. HL-LHC Sessions @ Chamonix
RF Upgrade Paths:
Full detuning of the 400MHz RF system
 ±15mm long. modulation (±50ps) of IP
 Klystron power limited to 200kW
Coupler lifetime (15y?), storage and consolidation for HL-LHC?
200MHz, 800MHz BL and 800MHz BS options
 feasibility / prototype studies until LS2  need to decide when?
RF noise for flattening bunches even in ‘bunch shortening mode’
‘WBFB would be nice and studies
should continue’
 but no clear justification of need
Why do we continue with 800MHz options; Brennan’s stateent that longer bunches in the SPS can make the LIU and HL-LHC parameters match! Klystron lifetime and need for matched Consolidation
O. Brüning, Chamonix Summary CERN, March 3rd

7. HL-LHC Sessions @ Chamonix
Collimation Upgrade Path for the HL-LHC:
2015 operation experience:
 up to 280MJ beam energy and no quench from beam losses
 but machine configuration and beam parameters were not pushed
Quench test: (Eb-max > 420MJ, LHCnom = 362MJ, HL-LHC = 630MJ)
 difficult extrapolation for protons due to absence of quench
 11T DS collimators in IR7
(2 Cryoassembly per beam  4 in total, 2 by LS2),
 connection cryostat DS collimators in IR2 (2 units total)
 mitigation in DS of IR1 & IR5 via orbit bumps
Material tests:
 encouraging result for MoGr (jaw survived 288b of 1.3x1011p)
 Radiation test need to be redone due to damage with too high dose
 coating studies for impedance reduction advancing well (2 jaws)
Crystal collimation: successful channeling in MD!
 option for Pb but NOT obvious for p (power on absorbers)!
Hollow e-lens: interesting for Halo depletion  on path to Baseline
Decision on 11T DS collimatros for IR7 only, alternative solutions for other IRs, progress with MoGr, Crystal collimation is NO solution for proton operation, Materials -> I would also emphasise that in 2015 we built to full-scale jaws that with a new design for HL. Important milestone. Eb-max > 420MJ, LHCnom = 362MJ, HL-LHC = 630MJ
O. Brüning, Chamonix Summary CERN, March 3rd

8. HL-LHC Sessions @ Chamonix
Crab Cavity Test Installation in the SPS:
Vital to gain feedback from operation with beam before launching of
cavity production for HL-LHC  need results before LS2!!!
Tight and ambitious schedule
but doable!
 Visualization and planning now
Preparation in EYETS 16/17
Installation YETS 17/18
 vital for project to be able to launch
Carb cavity production by LS2!!!
(international partners!!!)
Cable and pipework length:
~ m
65m
Cold-box
+SPS fire safety
CCCM
200m2
Ambitious and tight schedule but doable. Full support from the HL-LHC project. Only chance for getting experience with beam before production launch.
O. Brüning, Chamonix Summary CERN, March 3rd

9. HL-LHC Sessions @ Chamonix
Coating Options for IR2 and IR8:
Triplet magnets in IR2 and IR8 will not be changed for HL-LHC
but they will see the same current as the new magnets in IR1/IR5
Need procedure to reduce SEY of the triplets beam screens!
Two options: aC coating or Lase Engineered Surface Structures (LESS)
Plan A - Baseline: a-C as in IR1 and IR5  can be done in-situ ✔
SPS tests: effect of radiation ✔; Impedance ✔; in-situ setup?
 decreasing H2 desorption and increase deposition rate (B-field)
Plan B - Option: LESS  proof of compatibility with HL-LHC 2017
 Impedance, dust?  COLDEX
 Both methods could be applied to all IPQ!!!!
a-C
LESS
Low SEY based on the electronic properties of the material
Low SEY is a
morphological effect
Two very interesting options!
O. Brüning, Chamonix Summary CERN, March 3rd

10. HL-LHC Sessions @ Chamonix
Lessons from Civil Engineering Test Drills and Earth Quakes
On Vibration Tolerances:
Driven by worries about vibrations from the HL-LHC civil engineering
GEOTHERM2020
a renewable energy
production project by
the Canton of Geneva
GEOTHERM2020; O(100) amplification by triplet cryostat, worry about micrometer movements; hollow electron lens options
O. Brüning, Chamonix Summary CERN, March 3rd

11. HL-LHC Sessions @ Chamonix
Lessons from Civil Engineering Test Drills and Earth Quakes
On Vibration Tolerances:
From Noise to Beam
 O(100) amplification to cold-mass for certain modes (H0)
 O(10-100) attenuation H1 and H2
 order of micrometer tolerance for vibrations!
 Schedule that allows CE construction during LS2!!
 Hollow electron lens for halo depletion!
In (ω)
Out (ω)
H1 (ω)
H0 (ω)
Beam stability
H2 (ω)
GEOTHERM2020; O(100) amplification by triplet cryostat, worry about micrometer movements; new schedule, CE contract, hollow electron lens options
O. Brüning, Chamonix Summary CERN, March 3rd

12. HL-LHC Sessions @ Chamonix
Heavy Ion Operation after LS2:
Experiments upgrade during LS2 (ALICE)
LIU upgrades during LS2  Pb HL operation starts in Run3
Luminosity limitation from Bound Free Pair Production (BFPP)
 Orbit bumps & Dispersion Suppressor collimators!
Luminosity lifetime dominated by ‘burn-off’
Assume equal luminosity sharing: Projections of nb-1 /
Pb-Pb run (new LIU baseline + high efficiency)
Requested running scenarios (LoI):
Pb-Pb  2.85 nb-1
Pb-Pb  2.85 nb-1
pp reference run
LS3
Pb-Pb  2.85 nb-1
2028 ½ Pb-Pb 1.5 nb-1 + ½ p-Pb 50 nb-1
Pb-Pb  2.85 nb-1
2030   LS4
3 DS collimation solutions (bumps, collimators in empty cryostat and 11T DS); versatile program with request for flexibility, predictions are now within 40% of the experiments needs
O. Brüning, Chamonix Summary CERN, March 3rd