Large Hadron Collider:Status and Prospects

Stefano Redaelli for the LHC teams

CERN Beams Department Operations Group

4

Summer School on “The Physics of LHC”

June 14

-19

, 2010

Palazzo Palmieri, Martignano (LE), Italy

Large Hadron Collider:

Status and Prospects

Part 2

Outline - 2 ^nd part

• Recap. of 1 ^st lecture

• LHC parameters

- Energy challenge

- 2010-11 run configuration

• LHC status

- Commissioning: baseline/status - Luminosity performance

- Highlight of LHC operation

• Outlook

Where we stand...

Record performance on the 24 ^th of May:

L ≈ 3 x 10 ²⁹ cm ^-2 s ^-1 in all experiments After that, focus was put on the commissioning of

Beam 1

Beam 2

Energy

Outline

• Recap. of 1 ^st lecture

• LHC parameters

- Energy challenge

- 2010-11 run configuration

• LHC status

- Commissioning: baseline/status - Luminosity performance

- Highlight of LHC operation

• Outlook

Basic accelerator physics (I)

x(s) = A !

β _x (s) cos[φ(s) + φ ₀ ] + D(s) × ∆p p

Bρ = p e

Q = 1 2π

! ds

β(s) Q ^! = ∆Q

∆p/p

x ^!! + K(s)x = 1 ρ

∆p p ₀

σ _x (s) = !

"β _x (s) + [D _x (s)δ] ²

Equation of motion and its solution:

Betatron tune and chromaticity:

Emittance and beam size:

Beam rigidity:

Beta function

Dispersion

Basic accelerator physics (II)

Dipole errors closed-orbit distortion

Quadrupole errors perturbation of beta functions (β-beating)

Δg Δk 1

Beam measurements at the LHC

Closed-orbit

Betatron tune

Longitudinal profile

Beam losses

Transverse size

Wire

LHC injector complex

1.4 GeV

450 GeV

LHC layout and accelerator systems

L = 26.7 km!

70-140 m underground.

Eight arcs and

eight straight sessions:

Point 1: Atlas, LHCf

Point 2: Alice, injection

Point 3: Momentum cleaning

Point 4: RF

Point 5: CMS, TOTEM

Point 6: Beam Dumps

Point 7: Betatron cleaning

Point 8: LHCb, injection

LHC design parameters

Nominal LHC parameters

Beam injection energy (TeV) 0.45

Beam energy (TeV) 7.0

Number of particles per bunch 1.15 x 10 ¹¹ Number of bunches per beam 2808 Max stored beam energy (MJ) 362 Norm transverse emittance (μm rad) 3.75 Colliding beam size (μm) 16 Bunch length at 7 TeV (cm) 7.55

β

= 0.55 m

Crossing = 285 μrad L = 10

cm

s

L = N ² n _b f _rev 4πσ _x σ _y F

N = bunch population n

= number of bunches f

= revolution frequency σ

= colliding beam sizes F = geometric factor from crossing angle, θ

F = 1/

!

1 +

"

θ _c σ _z 2σ ^∗

# 2

Luminosity:

Outline

• Recap. of 1 ^st lecture

• LHC parameters

- Energy challenge

- 2010-11 run configuration

• LHC status

- Commissioning: baseline/status - Luminosity performance

- Highlight of LHC operation

• Outlook

Path to high luminosity

L = 1

4π · m ⁰ c ² · f _rev · N · F

β ^∗ · # ⁿ · E ^stored

E _stored = E _b · N · n ^b

! _n = γ!

σ _x ^∗ = σ _y ^∗ = !

β ^∗ #

Normalized emittance:

Colliding beam size (round beams):

Stored beam energy:

N = bunch population n

= number of bunches f

= revolution frequency β

= beta functions at IP F = geometric factor E

= beam energy

Constant

Tunnel length

Single bunch + beam- beam limitations

Optics constraints

Injectors + damage limits

The LHC can

only push the

luminosity by

increasing the

The stored energy challenge

Increase with respect to existing accelerators :

•A factor 2 in magnetic field

•A factor 7 in beam energy

•A factor 200 in stored energy

Quench limit:

5-30 mJ/cm ³

LHC beam:

360 MJ

Damage limit

~ 1 MJ

To set the scale...

Example:

Few cm long groove on an SPS vacuum chamber from the impact of ~1% of a nominal LHC beam during an incident:

 vacuum chamber ripped open.

 3 day repair.

The same incident at the LHC implies a shutdown of > 3 months.

 The 11 GJ of energy stored in the magnets are sufficient to heat and melt 15 tons of Copper (~1.7 m ³ ).

We have seen what a fraction of that could do in sector 3-4...

 The 360 MJ stored in each beam correspond to ~90 kg of TNT .

Plasma-hydrodynamic simulations indicate that the beam will drill a

~30 m long hole into Copper.

Effect of a fraction of that...

Quadrupole-dipole interconnection

Main damage area ~ 700 metres.

 39 out of 154 dipoles,

 14 out of 47 quadrupole short straight sections (SSS)

from the sector had to be moved to the surface for repair (16) or replacement (37).

Quadrupole support

Accident of September 19 ^th , 2008

Dipole busbar Vac. chamber

Isolating vacuum

Dipole cold-mass

Accident of September 19 ^th , 2008

Dipole busbar Vac. chamber

Isolating vacuum Dipole cold-mass

Dipole bus bar

LHC energy target - way down

450 GeV

2002-2008

7 TeV

When Why

12 kA ^Design

All main magnets commissioned for 7TeV operation before installation

Summer 2008

5 TeV

Detraining

9 kA

Detraining found for magnets in series, during HW commissioning 5 TeV poses no problem

Difficult to exceed 6 TeV

Spring 2009

3.5 TeV 6 kA

Late 2008 Joints Machine wide investigations

following S34 incident showed problem with joints

Nov. 2009 nQPS

2 kA 1.18 TeV

Commissioning of new Quench

Protection System (nQPS)

LHC energy target - way up

When What Train the dipole magnets

- 6.5 TeV is within reach

- 7 TeV will take time 7 TeV 2014 ? Training

1.18 TeV

2009

450 GeV

3.5 TeV nQPS

2010 nQPS system commissioned 2011

Stabilizers

6 TeV 2013 Repair joints

Complete pressure relief system

Goals for 2010-2011

Repair of Sector 34 1.18 TeV

nQPS 6kA

3.5 TeV

I

< I < 0.2 I

β* ~ 2 m

Ions

3.5 TeV

~ 0.2 I

β* ~ 2 m

Ions

2009 2010 2011

No Beam B Beam Beam

Goal (ambitious!) for the run: collect 1 fm ^-1 of data/exp at 3.5+3.5 TeV.

Ion physics at the end of each run.

Short shut-down over Christmas.

To achieve this goal the LHC must operate in 2011 with L ~ 2×10 ³² Hz/cm ² ~ Tevatron Luminosity

which requires ~700 bunches of 10

p/bunch (stored energy of ~ 30 MJ – 10% of nominal)

Implications:

Strict and clean machine setup.

Machine protection systems at near nominal performance!

β

β

IP1 / IP5 11 m 2 m

IP2 10 m 2 m

IP8 10 m 2 m

IP5-TOTEM 11 m 90 m

Minimum β* in various IP’s

Examples from other accelerators

It takes time....

Outline

• Recap. of 1 ^st lecture

• LHC parameters

- Energy challenge - Energy prospect

- 2010-11 run configuration

• LHC status

- Commissioning: baseline/status - Luminosity performance

- Highlight of LHC operation

• Outlook

Recent timeline

➡ End of summer 2008

- Accelerator complete, ring cold and under vacuum.

➡ September 10 ^th 2008

- First beams around!

➡ September 19 ^th 2008

- The incident in sector 3-4.

➡ 2008 – 2009

- 14 months of major repairs and consolidation.

- New Quench Protection System (nQPS) for protection of all joints.

➡ November 20 ^th 2009

- First beams around the rings again.

➡ November 29 ^th 2009

- Both beams accelerated to 1.18 TeV simultaneously.

➡ December 8 ^th 2009

- 2-on-2 accelerated to 1.18 TeV - highest energy collider!

➡ December 14 ^th 2009

- 2-on-2 stable beams at 1.18 TeV, collisions in all experiments.

2010 beam commissioning strategy

Global machine checkout 450 GeV re-commissioning

System/beam commissioning continued Squeeze

Establish stable safe beams at 3.5 TeV Collisions at 3.5 TeV

Full machine protection qualification Collisions at 3.5 TeV squeezed

Ramp commissioning

Machine protection commissioning

today

Commissioning interleaved with

physics at intermediate luminosity

2010 commissioning milestones

27 ^th Feb First injection

28 ^th Feb Both beams circulating

5 ^th March Canonical two beam operation 8 ^th March Collimation setup at 450 GeV 12 ^th March Ramp to 1.18 TeV

15 ^th - 18 ^th March Technical stop – bends good for 6 kA 19 ^th March Ramp to 3.5 TeV

30 ^th March First 3.5 TeV collisions in all experiments (media event) 1 ^st April Betatron squeeze to 5 m in IP1 and IP5

4 ^th - 5 ^th April 19h-long store with collisions in all IPs 7 ^th April Betatron squeeze to 2 m in IP1 and IP5

24 ^th April Stable unsafe beams with β ^* = 2 m in all IPs 17 ^th May Two nominal bunches of >1x10 ¹¹ p to 3.5 TeV 24 ^th May Luminosity > 10 ²⁹ cm ^-2 s ^-1 in all experiments

26 ^th May Design bunches of >1x10 ¹¹ p were brought in collisions

x 10

x 10

Example of commissioning

Ramp Problems

Beam 1 Beam 2

2 days

Energy

A good physics period

Bunches injected, kept the minimum time needed for tuning and for recovering ref conditions, then ramp, then stable beams!

And then... hands OFF! ! !

48 hours

Record luminosity performance

Beam 1

Beam 2

Energy

Record luminosity performance

13 bunches of ~2 x 10 ¹⁰ p (0.15 kJ) 8 collisions per experiment

β ^* = 2m in all IPs L ≈ 3.0 x 10 ²⁹ cm ^-2 s ^-1

Beam 1 Beam 2 Energy Instantaneous luminosity in the

5 fills for physics on May 24

10 ²⁹ cm ^-2 s ^-1

Present luminosity performance

Courtesy of M. Ferro-Luzzi

The LHC page1

Beam Energy Beam 1

Beam 2

Beam energy

Fill number

Machine:beam mode

Information BIC and safe

machine parameters (SMP)

Operation crew’s comment

The LHC page1

Beam Energy Beam 1

Beam 2

Beam energy

Fill number

Machine:beam mode

Information BIC and safe

machine parameters (SMP)

Operation crew’s comment

Interlock / SMP panel on page1

SMP = safe machine parameters

Allows experiments to take data with sensitive

components: all safety conditions are met!

Changes of some of these modes required

handshake with the

experiments.

Page1 for injection modes

After a beam dump

Screens of

dump line

Ramp Down / Recovery

Info on the last post-mortem event, with

comment by the Engineer in Charge (EiC).

Page1 - powering mode

Powering phase for the different

sectors

My daughter

LHC “operation” Page1

Outline

• Recap. of 1 ^st lecture

• LHC parameters

- Energy challenge - Energy prospect

- 2010-11 run configuration

• LHC status

- Commissioning: baseline/status - Luminosity performance

- Highlight of LHC operation

• Outlook

LHC cycle

energy ramp

preparation and access

beam dump

injection phase collisions

collisions

450 GeV 7 TeV

start of the

ramp Squeeze

3.5 TeV

Optimization at injection

- Tunes to nominal injection values (H / V = 0.28 / 0.31)

- Chromaticity under control - Coupling under control

- Repeat with experiment magnets on - Establish reproducibility fill after fill (with pre-cycle)

...

All essential to have a stable and reproducible machine at 450 GeV.

A lot of meticulous work!

The machine is now well under

control at injection for all beam

and bunch intensities!

Example of instabilities

Example of very BAD lifetime at

injection!

Chromaticity adjustment

Q

= Q

+ Q

∆p

p

2010 reference “golden” orbit

Beam 1 - H

Beam 1 - V

2010 reference “golden” orbit

Beam 1 - H

Beam 1 - V Beam 2 - H

Beam 2 - V

Is this good or bad??

-30 -20 -10 0 10 20 30 -30

-20 -10 0 10 20 30

] m m [ er utr e p a l aci tr e V

Horizontal aperture [ mm ]

Beam screen aperture

One word on references and tolerances

Up to 360 MJ stored energy

Orbit, beam size and alignment must be

controlled well and kept constant to avoid

problems!

In addition, collimators gaps are set with respect to reference orbit and beam size (remember Spain/Italy on euro coin ! !).

Closed orbit ± 4 mm

Beta-beat ± 20 %

Spurious dispersion 27% D nom Arc

Mechanical tolerance 1-2.5 mm

Alignment 1.0.-1.6 mm

Tolerance table

Transverse view in an arc

Cold aperture:

quench limit ~mJ/cm ³

Relative error of beta

functions around the

ring: Δβ/β

Optics: correction of β functions

R. Tomàs

Aperture measurements (i)

Aperture bottlenecks are found by exciting orbit oscillations (or emittance blow-up)

Measurements started

during the sector tests.

Aperture measurements (ii)

Aperture bottlenecks are found by exciting orbit oscillations (or emittance blow-up)

Measurements started during the sector tests.

Beam losses

Beam envelope + aperture model

No un-expected

restrictions found so far

..

Collimator setup

Collimator setup

Primary Secondary Dump Protection

Tertiary +Triplet

Tertiary +Triplet

Closed orbit

Normalized

coll aperture

Collimator setup

Primary Secondary Dump Protection

Tertiary +Triplet

Tertiary +Triplet

Closed orbit

Normalized coll aperture

Done for each collimator!

Exercise to be repeated if orbit or

optics change: important to do it after

Cleaning efficiency at 450 GeV

4000 beam loss monitor

Measurement noise Peak leakage

to supercond. magnets

Loss at primary collimator

Collimators

~ 5000

Collimation team

IP1

IP2 IP3 IP4 IP5 IP6 IP7 IP8

Ramp functions - dipoles

Present ramp with maximum dI/dt = 2 A /s

3.5 TeV ramp with nominal settings

Beam energy [ T eV ]

6 kA = 3.5 TeV

1000 s

We are limited by the new QPS system: 2 A/s instead than 10 A/s...

Ramp to 3.5 TeV is taking ~ 45 min instead than less than 20 min.

(The validation of nominal parameters has been DONE but not yet validated

with beam.)

Beam energy [ T eV ]

450 GeV

Scaling of currents with energy

Bρ = p e

Time [hh:mm]

Current [ A ]

Top energy

Injection

Ramp

The magnetic fields of all magnets must match the beam energy!

Pre-generated functions are loaded into the power converters and are triggered

Frequency change during ramp

200 Hz

Injection settings

3.5 TeV settings

Time/energy Jaw

position

Collimation team

Collimators are ramped with energy to maintain settings in sigma units when the beams shrink down → Ensure optimum cleaning and protection!

100 x 4 position functions + 2600 limit functions!

Collimator ramps

σ _x (s) = !

"β _x (s) + [D _x (s)δ] ²

! _top = E _inj

E _top ! _inj

Energy ramp to 3.5 TeV

➡ Successfully ramped two pilot beams at first attempt!

➡ Now it takes 47 min (main dipoles limited to 2 A/s by nQPS)

➡ Ramp quickly became operational routine!

➡ Present intensities for physics ramped without losses.

➡ Key beam parameters stable and reproducible

➡ Tune and orbit feedback working

➡ Can ramp nominal bunches of 10 ¹¹ protons

➡ ... definitely, the beams like it up there!

Energy ramp to 3.5 TeV

➡ Successfully ramped two pilot beams at first attempt!

➡ Now it takes 47 min (main dipoles limited to 2 A/s by nQPS)

➡ Ramp quickly became operational routine!

➡ Present intensities for physics ramped without losses.

➡ Key beam parameters stable and reproducible

➡ Tune and orbit feedback working

➡ Can ramp nominal bunches of 10 ¹¹ protons

➡ ... definitely, the beams like it up there!

Ramp of 13x2 bunches: no

losses!

Lifetime >> 100h

Betatron squeeze - intro

➡ The luminosity increases like 1 / β, for a given stored intensity!

➡ The change of optics needs a very tight control of the power converters all around the ring:

- IRs: 13 x 2 quadrupoles around the IP

- Ring: global corrections of tune, chromaticity, coupling, orbit

➡ The squeeze reduces the aperture at the inner triplets!

- Collimator gaps need to be adjusted as well.

➡ It is done at top energy, with highest damage potential.

L = 1

4π · m ⁰ c ² · f _rev · N · F

β ^∗ · # ⁿ · E ^stored

Tevatron quench statistics 2007-2009

A. Valishev, PAC09

Controls implementation

Time [hh:mm]

Current [ A ]

For the power converters, it is like a “ramp”: currents

of the matching section quadrupoles change to modify the optics functions.

Current settings for the quadrupoles in IR5:

I [A] vs t [s]

Controls implementation

Time [hh:mm]

Current [ A ]

For the power converters, it is like a “ramp”: currents

of the matching section quadrupoles change to modify the optics functions.

Current settings for the quadrupoles in IR5:

I [A] vs t [s]

Ex: three different

optics in IP5 for β ^* =

11m (inj), 9 m and 7m

β* monitoring in a physics fill

Time ~ 30 min Flat-top

IP1/5: 11m → 2m IP2/8: 10m → 2m

Stop a 5 m to close collimators

2 m in all IPs Achieved the

minimum value for the 2010-11 run!

All IPs done together.

β ^* measurements in all IPs

Impressively good agreement for the first

test down to β ^* = 2 m

Effect on luminosity

Courtesy of M. Ferro-Luzzi

Factor 4-4.5 improvement (expected 5.5)

Expected improvement consistently

Colliding beams

Luminosity tuning

S. White

VdM scans operational early on - routinely performed in all IPs

Outline

• Recap. of 1 ^st lecture

• LHC parameters

- Energy challenge - Energy prospect

- 2010-11 run configuration

• LHC status

- Commissioning: baseline/status - Luminosity performance

- Highlight of LHC operation

• Outlook

Short-term plans

➡ We have run for a few weeks above the safe limits at 3.5 TeV of I tot = 3.14 x 10 ¹⁰ p (up to factor 10 above).

➡ We are now working on the commissioning of nominal bunches operation: 1.2 x 10 ¹¹ p.

➡ Strategy: commission maximum bunch intensity and then increase the number of bunches to push performance.

➡ Optimum for luminosity, but increased risk in case of asynchronous beam dump.

➡ Therefore, initial physics runs will start with larger β* = 3.5 m:

- Increased safety: triplets in the shadow of the arcs;

- Can work with relaxed collimator settings;

- Easier transition to crossing angles (more triplet aperture).

➡ Working on some puzzles...

Some puzzles: “Hunt the Hump”

Broad frequency “hump” driven beam excitation → emittance blow-up,

significant lifetime reduction

Vertical plane, worse for beam 2 Actually a fast frequency shifting

oscillation with the mean drifting slowly We are open to suggestions!

Reduction of lifetime at top energy (7 minute period)

Christmas tree and dancing beams

Synchrotron side-bands around tune peak, driven

by head-tail instabilities.

Explained by large chromaticity (E. Métral).

Can be efficiently cured with Landau octupoles.

Optimum settings being determined

Mitigated by increasing longitudinal emittance from SPS.

Transverse damper being commissioned.

Effect of Landau octupoles

First ramp:

octupoles OFF

Octupoles ON

at 200 A

Looks under good control now

More than 6h with

nominal bunch at 3.5 TeV

Commissioning of squeeze

with orbit+tune feedback,

6h

Conclusions

We have well-defined goals for the 2010-11 run at 3.5 TeV.

- After that, long shut-down to prepare the machine for larger E.

The initial beam commissioning of the LHC has been impressive!

- Thanks to all the teams and people involved (over many years!!).

The machine is in a very good shape so far:

- Is magnetically well understood and reproducible.

- Is optically behaving well.

- Is armed with marvelous instrumentation, software and hardware.

We routinely deliver collisions with squeezed beams in all IPs.

- Achieved 3x10 ²⁹ cm ^-2 s ^-1 in all experiments (β ^* =2m, ~2x10 ¹⁰ p/bunch).

- Stored energy about ~10 larger than safe limit at 3.5 TeV.

Set-up with nominal bunches is on going, more tricky (interesting) than expected. Followed by physics with β ^* =3.5m.

Still a lot to sort out for machine protection before we are