LHC Technical Committee, 23/05/20071 LHC Commissioning Phases Squeeze presented by Massimo Giovannozzi on behalf of the LHCCWG Particular thanks to S

LHC Technical Committee, 23/05/2007 1

LHC Commissioning Phases

Squeeze

presented by Massimo Giovannozzi

on behalf of the LHCCWG

Particular thanks to

S. Redaelli, G. Arduini, R. Assmann, R. Bailey, B. Goddard, V. Kain, M. Lamont, L. Ponce, J. Wenninger, EICs,

LHCCWG members and ABP-LCU members


LHC Commissioning Phase 11 – Squeeze

• Phase A.11: Squeeze – Objectives– Entry conditions– Commissioning procedures– Exit conditions

• Summary


Squeeze - General considerations

Physics runs with un-squeezed beams imply that the squeeze is only needed after:

• Required Machine Protection in place

• Better understanding of the collimation system

• Stable separated beams at 7 TeV

• Can bring beams into collision

• Can master the ramp and get interleaved beams to 7 TeV

A fairly good knowledge of the LHC will have been gained by the time when we will try the squeeze.

First turn

First turn

Circulating beam Circulating

beam450 GeV:

initial 450 GeV: initial

450 GeV: detailed 450 GeV:

detailed450 GeV:

increasing intensity

450 GeV: increasing intensity

Two-beam operation

Snap-back

Ramp

Single-beam 7 TeV

Two-beam 7 Tev

Collisions

Squeeze

Snap-back

Ramp

Single-beam 7 TeV

Adapted from M. Lamont


LHC Stage A: Commissioning phases

Phase Description

A.1 Injection and first turn: injection commissioning; threading, commissioning beam instrumentation.

A.2 Circulating pilot: establish circulating beam, closed orbit, tunes, RF capture

A.3 450 GeV initial commissioning: initial commissioning of beam instrumentation, beam dump

A.4 450 GeV optics: beta beating, dispersion, coupling, non-linear field quality, aperture

A.5 450 GeV, Increasing intensity: prepare the LHC for unsafe beam

A.6 450 GeV, two beam operation

A.7 450 GeV, collisions

A.8 Snap-back and ramp: single beam

A.9 Top energy checks

A.10 Top energy, collisions

A.11 Squeeze: commissioning the betatron squeeze in all IP's

A.12 Physics runs: physics with partially squeezed beams, no crossing in IP1 and IP5

Phases for full commissioning Stage A (pilot physics run)

Basic Objectives:• Master mechanics of squeeze• Control and protect aperture during optics change • Control orbit and optics during squeeze • Establish procedures and references (orbit, tune) for the feedback operation• Establish collimators settings during the squeeze (in particular TCTs to protect the triplet) as

well as TCDQ • Prepare for collisions with squeezed beams and physics


Squeeze – Overview of Steps Involved

Step Activity Priority

A.11.1Beam-based calibration of collimators for triplet protection and cleaning

Collimation Team

1

A.11.2 Load magnet settings into the hardware ABP/OP/PO 1

A.11.3Running the betatron squeeze with detailed measurements (beam parameters, optics, ...) for new beta*

ABP/OP 1

A.11.4 Preparation to bring the beams into collision ABP/OP 1

Priority categories (71th LTC):1. absolutely mandatory, 2. should be done if possible, 3. would be nice if it could be done

Iterative procedure for steps 1 to 3: to be repeated for each intermediate beta* stop point until we can get to the final value for physics.

Remark: The squeeze will be performed by changing gradients (linear interpolation) in between two matched optics.Recap of key parameters:

• Max 156 bunches

• No crossing angle

• beta* = 2 m


Squeeze - General commissioning approach

Goal: commission simultaneous squeeze of the IP1 and IP5, both beams

How can we get there during commissioning?

1. Start with a single pilot Beam 1 and squeeze IP1 without separation

2. Verify squeeze of one beam with parallel separation

3. Squeeze two separated pilot beams in IP1

4. Commission squeeze in IP5 with a single pilot Beam 1 (squeeze in 2 IP’s in parallel) - try with separation on

5. Try two beams in IP5 as well

• Remark: First commissioning done with detector magnets ON (input from their effect from collisions without squeeze, A.10). We should be ready to switch them OFF in case of difficulties.

• Remark: Squeeze of IP8 (and IP2) will follow in a similar manner.


Squeeze – Entry Conditions - IAssumption: The squeeze takes place with circulating beams at 7 TeV and does

not start at lower energies. • Beams separated, no crossing in IP1 and IP5 (works up to 156 on 156)

• Stable and well measured optics at 7 TeV for both - separated – beams (as exit of A.9):

– Reference "golden" orbit with beam-beam separation ON established for feedback. – Reference "golden" orbit established in the cleaning and dump insertions.– Beta-beating measured and under control in all the machine.

• Orbit and optics stable in the cleaning and dump insertions (1 sigma at 7 TeV).– If needed, the orbit feedback must be commissioned and operational, at least for local

orbit control at collimator locations (IR7 and IR6, maybe also IR3 if momentum cleaning is needed).

• Aperture measured at critical bottlenecks and corrected to acceptable levels (as exit of A.4 and A.9).

Aperture bottlenecks will appear during betatron squeeze: special measurements to be performed at 450 GeV.

Tolerance tables on beam parameters to be defined…


Squeeze – Entry Conditions - II• Collimators and dump protection elements (TCDQ) tuned to ensure

required cleaning and protection. – Cleaning collimators: after-ramp settings of injection optics at 7 TeV.

– Dump system fully commissioned for 7 TeV beams.

NB: collimators and dump protection elements (TCDQ) will require setting adjustments for every beta* step.

• Tertiary collimators (TCTs) hardware-commissioned and ready to move. Beam-based determination of closed orbit, beam size and divergence at each TCTs.

• Landau octupole circuits fully hardware-commissioned. • Ready-to-use magnet settings from MADX optics files and all timing

tables (trigger events/measurements). • Full commissioning of squeeze settings generation and trim (timing

tables) for insertion magnets.

A decision must be taken beforehand on the number of steps during the squeeze and on the final value of beta* for physics at each IP.


Squeeze – Entry Conditions - III• All instrumentation operational (no special requirements for squeeze).

Instrumentation commissioning done at phases A.3, A.6, A.10.

Continuous emittance/beam size measurement extremely useful.

• All software operational (no special requirements for squeeze).

• Orbit monitoring + feedback available (commissioned for constant optics).

• Q, Q' monitoring + feedback available (commissioned for constant optics).

Need dedicated commissioning for feedback! Change of optics matrices for correction algorithm, triggered from sequencer or manual timing distribution, has to be operational. However, the algorithm proved to converge also with 100% beta-beating…

• Distribution of beta squeeze factor for machine protection commissioned.

• Roman Pots, VELO, LHCf OUT. Verification of the interlock signals. • Detector magnets ON


Squeeze – Stage A.11.1 – Setup of TCTs for triplet protection and cleaning - I

• Collimators settings based on measured apertures (phases A.4, A.9). • End-of-ramp settings for the collimators can be kept up to beta* ~ 6 m.• Then, TCT will be set such that the triplet aperture is protected for the

next beta* value. All the other collimators and TCDQ will be moved in to provide cleaning and protection for reduced aperture corresponding to next beta* value.

T. Weiler Collimation WG#85

Remarks: TCTs will always be used to ensure triplets protection (independently on intensity/beta* values).


Squeeze – Stage A.11.1 – Setup of TCTs for triplet protection and cleaning - II

RWA, 28/11/2006 21

2) Squeeze

• Squeeze reduces overall machine aperture, for * smaller than about 6 m!

• Triplets become the aperture bottleneck in the LHC (act as primary collimators risk of quench and damage)!

• Collimators must be closed before the actual squeeze to prevent this from happening!

• Very tight machine tolerances from collimators with small gaps: proceed in stepsto profit from larger tolerances as long as possible!

• Impedance will increase once collimators are being closed. Tune spread from octupoles is required to stabilize beam!

• Overall orbit and optics must be sufficiently under control to always ensure protection of the machine! Feedbacks will help to ensure this!

• Squeeze is a complex and dangerous process in the LHC…

R. Assmann LHCCWG#18


Squeeze – Stage A.11.1 – Setup of TCTs for triplet protection and cleaning - III

RWA, 28/11/2006 26

Reduced Procedure for Low Intensity

End of Ramp Measure tail population to 6

Correct machine

Switch off FB (transv)

Correct machine

Adjust coll IR3/7 for n1 of next * step (apply 1 margin)

Squeeze to *=6 m all relevant IR’s

Correct machine

Scraping of tails

Check feedbacks?

Verify coll settingsAdjust dump protec-tion (TCDQ+TCS)

Adjust triplet collimators (TCT)

Squeeze each IR to next * step

(maybe track TCT’s with crossing bumps)

Correct machine

End of squeeze?

Put beams into collision

Physics

HIGH

LOW

Correct machine

YES

NO

Check losses and background

R. Assmann LHCCWG#18

Performed with TCP initially


Squeeze – Stage A.11.2 – Load settings - I

Load the relevant functions of current versus time in the hardware, namely• Insertion quadrupoles• Lattice sextupoles to correct chromaticity during squeeze• Insertion correctors

21/11/2006 LSA 2006 2

Optics

•Machine Layouts in LSA database From layout database (Chris, Delphine)

•LOOP OVER MAD Perl (Marek)

•All optics in the LSA database Twiss, strengths, optics parameters

M. Lamont LHCCWG#18

Remark: the target for Stage A is beta* = 2 m. Nonlinear correctors in triplets are not needed above beta* = 1 m. Otherwise functions for these circuits should be loaded, too.


- As many functions as the foreseen beta* steps have to be generated.- Need to define the appropriate timing events for each step. - Functions loaded ~ 10 s before the squeeze, then triggered by timing

events. - Few minutes are needed to generate the settings on-line (including

matrices for feedback).

Squeeze – Stage A.11.2 – Load settings - II

21/11/2006 LSA 2006 6

GENERATION

•Optics versus time•Time from ΔI and dI/dt limits•Parabolic round in and round off

between optics Allowing stop in squeeze

M. Lamont LHCCWG#18

• Do one beam at a time, one IP at a time according to the pre-defined order.

• Obviously this will not be the case for standard operation but we should start simple.

• dI/dt limits: Q4 is usually the limiting circuit for the squeeze

t for each beta* step: max of t for each insertion quadrupole circuit.


Squeeze – Stage A.11.3 – Run the squeeze - IOnce functions for the first beta* step are loaded and ready in the

hardware, the squeeze can be triggered by timing events sent out by the operators. Before this…

1. Switch ON continuous monitoring of tune and chromaticity (BBQ, PLL).2. Monitor beam losses around the ring, in particular in the IP and in the

cleaning IR's. 3. Continuous monitoring of the orbit. Feedback working (cleaning

insertions, dump region AND IP that is being squeezed). 4. If it is available, start a monitoring of the local orbit at the TCTs (H + V).

Save data for later analysis.

Then…

1. Trigger the change to the first beta* value by sending the appropriate timing event.

2. Ready to dump if something goes wrong.


Squeeze – Stage A.11.3 – Run the squeeze - II

In case everything goes well…

1. Perform the required measurements (optics, aperture, ...) at the new beta* value.

•Detailed measurement program and its procedures to be defined.•Define appropriate check procedures for optics and orbit in collimation and

dump regions.2. If necessary, adjust beta* with optics knobs (MADX on-line model).

3. Check losses and beam halo / adjust cleaning collimators and TCDQ for next step, if needed (changes only required for beta*< ~ 6 m).

4. Set the tertiary collimators to ensure an adequate level of MQX protection (later, with higher intensities, also to ensure cleaning!).

5. Record optimum collimator settings in the appropriated databases for the generation of the time functions of settings.


Squeeze – Stage A.11.3 – Run the squeeze - III

Ready to move to the next beta* value.

1. Load functions for new beta* step for the insertion magnets.2. Load updated settings for the main sextupole families. 3. Update the octupole settings if needed (depends on collimator settings/transverse feedback).

Trigger the next beta* step.

In case something goes wrong and the beam is dumped, try to understand where is the problem (post mortem analysis) and restart.


LHCCWG - November 29th 2006 6

Squeeze (3/4)

Quadrupole gradients [T/m] in the Dispersion Suppressor (Q7-Q10) as a function of : beam1 (left) beam2 (right)

Rather smooth except for 1 m << 2 m

S. S. FartoukhFartoukh, 23 LTC meeting, 23 LTC meeting

Squeeze – Stage A.11.3 – Run the squeeze on paper - I


Squeeze – Stage A.11.3 – Run the squeeze on paper - II


Squeeze (4/4)

Quadrupole gradient [T/m] in the trim quadrupoles (QTL11,-QT12,QT13) as a function of : beam1 (left) beam2 (right)

Smooth/monotonous for beam1 but more “erratic’’ for beam2, with unavoidable zero-crossing for both beams (matching procedure could be optimised if needed)

S. S. FartoukhFartoukh, 23 LTC meeting, 23 LTC meeting



BehaviourBehaviour of optical parameters during of optical parameters during squeeze of IR1 squeeze of IR1 -- IIII

2.0

2.1

2.2

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

Horizontal beta* (m)

Ch

rom

atic

ity

Chrom. Hor. (Beam 1) Chrom. Ver. (Beam 1)

Squeeze – Stage A.11.3 – Run the squeeze on paper - III

LHCCWG#18

Simulations performed on a perfect machine…



BehaviourBehaviour of optical parameters during of optical parameters during squeeze of IR1 squeeze of IR1 -- II

-2.0E-03

-1.5E-03

-1.0E-03

-5.0E-04

0.0E+00

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0


Del

ta t

un

e

9.990E-03

1.009E-02

1.019E-02

1.029E-02

1.039E-02

1.049E-02

Tu

ne

split

DQ Hor. (Beam 1)

DQ Ver. (Beam 1)

Tune split

Squeeze – Stage A.11.3 – Run the squeeze on paper - IV

LHCCWG#18



Squeeze – Stage A.11.3 – Run the squeeze on paper - IV

LHCCWG#18


BehaviourBehaviour of optical parameters during of optical parameters during squeeze of IR1 squeeze of IR1 -- VIVI

-0.10

-0.05

0.00

0.05

0.10

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0


Clo

se

d o

rbit

(si

gm

a)

Hor. Plane (Beam 1)Ver. Plane (Beam 1)

Computed outside IR1/5Computed outside IR1/5


BehaviourBehaviour of optical parameters during of optical parameters during squeeze of IR1 squeeze of IR1 -- VV

-1.0

-0.5

0.0

0.5

1.0

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0


Bet

a b

eati

ng

(%

)Hor. Plane (Beam 1)Ver. Plane (Beam 1)

Computed outside IR1/5Computed outside IR1/5



Squeeze – Stage A.11.3 – Run the squeeze with real magnets - I

Position of the problem

From a magnet standpoint, the low squeeze is a sequence of current ramps, eventually with changes of sign and stopsfor beam measurements and corrections

There are two possible implications, i.e.Hysteresis crossing

Decay and snapback

Both change the actual field produced for a given current (transfer function)

W. Venturini LHCCWG#21


Max setting errors,from hysteresis loops

(without modeling hysteresis crossing)

• MQM ~ 30 units at 320 A, 10 units at 1000 A, 5 units at 2000 A

• MQY ~ 25 units at 200 A, ~10 units at 300 A

• MQTL ~ 90 units at 17 A, ~ 25 units at 34 A, etc..

• MQT ( same as MQTL)…diverging at zero

-0.008

-0.006

-0.004

-0.002

0

0.002

0.004

0.006

0.008

0 200 400 600 800 1000 1200 1400

Current [A]

TF

Off

set

[Tm

/KA

]

MQY26_A2MQY26_A2_MinCurr-200AMQY25_A2MQY24_A1MQY24_A2SSS 621 A1 (SM18)SSS621 A2 (SM18)MQY30 A1MQY30 A2MQY 29 A1MQY29 A2MQY28 A1MQY28 A2MQY27 A1

8 units

-5.00E-03

-3.00E-03

-1.00E-03

1.00E-03

3.00E-03

5.00E-03

7.00E-03

9.00E-03

0 1000 2000 3000 4000 5000 6000

Current (A)

TF

-O

ffset

(Tm

/kA

)

MQM33 A2 MQM33 A1 MQM31 A2


MQM30 A2 MQM29 A1 MQM 29 A2








10 units

4.4 K

Squeeze – Stage A.11.3 – Run the squeeze with real magnets - II



2.1420

2.1430

2.1440

2.1450

2.1460

2.1470

2.1480

2.1490

2.1500

0.00 500.00 1000.00 1500.00 2000.00 2500.00 3000.00 3500.00

Current (A)

Tra

nsf

er F

un

ctio

n [

Tm

/KA

] 4.66 units2.1450

2.1460

2.1470

2.1480

2.1490

2.1500

2.1510

0 10 20 30 40 50 60 70 80 90 100

injection current for Q6R5 B2 = 207 A

No decay, or if any, below measurement noise (pretty high in this particular case)

Small loop

Squeeze – Stage A.11.3 – Run the squeeze with real magnets - III



Squeeze – Stage A.11.3 – Run the squeeze with real magnets - IV


Concluding remarks (1) Δk = f(k) can be extracted from hysteresis loops These errors due to hysteresis add to global uncertainty

on gradients, with the present FIDEL model FIDEL modeling of hysteresis crossing should bring

errors in the range of few units, but this gets harder at low currents

Very low settings for MQTL and MQT, difficult to manage: transfer functions diverge, it is difficult to get the desired field

No decay in MQT and MQTL On MQM and MQY full decay characterization needs

more data (measurement foreseen in 2007) Data are available at the median injection current, which is only indicative.


Squeeze – Stage A.11.4 – Preparation to bring the beams into collision

Assume that we are able to squeeze both beams separately for beta* values down to the value agreed for physics runs. Settings for movable devices are also defined.

Then, after this (details in A.10):

• Inject both beams, ramp and squeeze them both (with separation still ON).

• Once both beams are squeezed, load into the power supplies of the orbit correctors the functions to set the separation OFF (get them from MADX model).

• Switch OFF the orbit feedback (local orbit correction at the IR(s) that is(are) being squeezed) and trigger the event "go in collision“ (next phase…).


Squeeze – Exit Conditions• Betatron squeeze commissioned in all relevant IPs in a defined number

of step points.– Goal: define the maximum amount of losses and the required beam quality

(emittance blow-up, final beta* value) after squeeze.

• Definition of time-dependent settings for all the movable devices (collimators and TCDQ) versus beta* values and versus beam-beam separation, to be used later for automatic squeeze triggered by sequencer. This includes also interlocks position functions.

• Definition of reference orbits in the experimental insertions versus beta*.

• Definition of procedures for feedback operation – reference orbit– when to switch it on/off

• Definition of procedures for Q, Q' feedback operation.

• Definition of procedures for using Landau octupoles (expected to be needed only for higher beam intensities).


Summary• Phase A.11 :

– Squeeze beams

• Main focus is on:– Control the mechanics of the squeeze– Control and protect the aperture during the squeeze– Control the orbit and the optics during the squeeze– Protection of triplets using TCTs– Define the actual procedure/sequence to squeeze the various

insertions

• At the end of this phase:- beams can be brought in collision…


References• Web documentation

LHC Commissioning procedures: Phase A.11 [S. Redaelli]• Papers:

Squeeze criteria & requirements – Chamonix XIV [O. Brüning] What is required to safely get the beam out of the LHC – Chamonix XV [B. Goddard] Beam commissioning of the collimation system – Chamonix XV [R. Assmann]

• LHCCWG presentations:Collimation During Ramp and Squeeze, LHCCWG#18 [R. Assmann]Squeeze mechanics, LHCCWG#18 [M. Lamont] Squeeze optics and power converter settings, LHCCWG#18 [S. Fartoukh, M. Giovannozzi, J. Jowett, Y. Papaphilippou]Commissioning Procedures, LHCCWG#21 [S. Redaelli] 450 GeV Optics: IR Aperture and IR Bumps, LHCCWG#13 [Y. Papaphilippou] 450 GeV Optics – Mechanical Aperture and Momentum Aperture, LHCCWG#11 [S. Redaelli], Overview of Feedbacks and Implications for Commissioning, LHCCWG#6 [R. Steinhagen]Response Matrix Measurements and Analysis, LHCCWG#9 [J. Wenninger] Behaviour of the magnets through the squeeze, LHCCWG#21 [W. Venturini]Optics measurements needed at top energy, LHCCWG#22 [F. Zimmermann]Two-beam operation, LHCCWG#25 [R. Assmann]

• Other presentations:IR1 & IR5 optics updated for the LHC V6.5, LTC 31/03/2004 [S. Fartoukh]V6.5 optics development in IR2 & IR8, LTC 31/03/2004 [O. Brüning]Requirements in ramp & squeeze, LHC MAC 9-11/12/2004 [O. Brüning]Squeeze of the crossing scheme in IR1 & IR5, ABP-LOC 11/10/2005 [S. Fartoukh]Discussion of the operational procedure for squeezing the beams, ABP-LCU 12/02/2007 [S. Redaelli]Progress in IR8 matching for beta* squeeze, ABP-LCU 26/02/2007 [Y. Papaphilippou]Final squeeze solution for IP8, ABP-LCU 21/05/2007 [Y. Papaphilippou]LHC ramp commissioning, LTC 9/5/2007 [M. Lamont]LHC Orbit Stability during β* Squeeze, LHC Collimation WG 27/11/2006 [R. Steinhagen]

http://lhccwg.web.cern.ch/lhccwg/overview_index.htm

http://lhccwg.web.cern.ch/lhccwg/Meetings/2006.10.04/reproducibility.ppt

http://lhccwg.web.cern.ch/lhccwg/Meetings/2006.09.20/IR%20bumps.ppt

http://lhccwg.web.cern.ch/lhccwg/Meetings/2006.07.26/LHCCWG_2006-07-26.pdf

http://lhccwg.web.cern.ch/lhccwg/Meetings/2006.05.17/2005-05-17_LHCCWG_feedbacks_rstein.pdf

http://lhccwg.web.cern.ch/lhccwg/Meetings/2006.06.28/LOCO-LHCCWG-Jun06.ppt

http://lhccwg.web.cern.ch/lhccwg/Meetings/2006.11.15/PC-tracking-JW-LHCCWG-Nov06.ppt

http://lhccwg.web.cern.ch/lhccwg/Meetings/2006.11.15/PC-tracking-JW-LHCCWG-Nov06.ppt

Documents

LHC Technical Committee, 23/05/20071 LHC Commissioning Phases Squeeze presented by Massimo Giovannozzi on behalf of the LHCCWG Particular thanks to S