LHC Ramp Commissioning Mike Lamont Reyes Alemany-Fernandez Thanks to: Stefano, Verena, Walter.

LHC Ramp Commissioning

Mike Lamont

Reyes Alemany-Fernandez

Thanks to: Stefano, Verena, Walter

LHC ramp commissioning 29/5/2007

LHC ramp commissioning Ramp generalities Overall strategy Beam entry conditions and tolerances Entry conditions Procedures Exit conditions What’s in place Upcoming tests


Magnets The basic design of the LHC ramp (parabolic, exponential, linear,

parabolic (PELP)) is designed to: P: Push up the time in which the snapback is resolved. E: Constant Bdot – ramp induced coupling current L: Max dI/dt of MB power converters P: smooth round off at top energy

Start [s] End [s] Start p [GeV] End p [GeV]

Snapback 0 70 450 ~500

Parabolic 0 405 450 ~900

Exponential 405 820 ~920 ~2400

Linear 820 1500 ~2400 ~6800

Parabolic 1500 1600 ~6800 7000

LHC main dipole proposed baseline current ramping - Bottura, Burla and Wolf


Ramp Construction

Construct idealized MB current function (PELP) using standard prescription (defined in terms of current variation during snapback etc.)

From this generate momentum(t) using averaged calibration curve

Use this a scale parameter for settings generation Optics defined as a function of time

Design optics (Note change of IR2 optics)

Circuit currents via FiDeL generated calibration curves


Nominal cycle

0

14000

-3000 -2000 -1000 0 1000 2000 3000

Time [s]

MB

cu

rre

nt

0

1

2

3

4

5

6

7

8

9

B [

T]

RAMP DOWNSTART RAMP

PHYSICS

PREPAREPHYSICS

BEAM DUMP

PREINJECTIONPLATEAU

INJECTION

T0 Tinj

SQUEEZE

PHYSICS

Ramp down 18 Mins

Pre-I njection Plateau 15 Mins

I njection 15 Mins

Ramp 28 MinsSqueeze 5 Mins

Prepare Physics 10 MinsPhysics 10 - 20 Hrs

I ~ t2

I ~ et

I ~ t

Injection plateau 0alpha 5.92105E-06current rate end snapback 0.6current at injection 760current variation during snapback 20parabolic segment duration 405.333current at end exp 4110.000b at end exp 3.000current to field scaling factor 1370.000max current rate 10.000current rate end parablolic 3.648exp time constant inverse 2.433E-03


Possible variations

Skip exponential Ramp induced inter-strand coupling currents small Simplifies ramp structure – easier to stop anywhere Cost – one minute per ramp

Slower snapback Measurements planned to check dependency

Programmed stop in ramp Parabolic – (Linear) - Parabolic

Pre-cycle (as entry condition) Snapback minimization – particularly during commissioning


Stopping with beam in the ramp

Must be programmed before starting the ramp with appropriate round-off behaviour of the functions Might need to handle (much reduced) decay after the stop

Restart with beam is possible in theory. requires a new set of functions to be loaded including corrections for handling the associated snapback during commissioning will be dumping the beam

Used for commissioning of beam dump, beam loss monitors, beam measurements, optics checks, physics...


Settings/Trim

Run to run feed forward Feed forward from feedback system Incorporation of TRIMs into settings before ramping

Ensure and test compatibility with feedbacks and make sure that machine safety cannot be compromised

constant strength, smoothed out etc. as appropriate. This will be configurable depending on the parameters involved. The

appropriate strategy will be decided based on common sense and experience with beam.

Real time knobs on key beam parameters (tune, chromaticity) are planned. To be tested during commissioning.

LSA


Magnets Transfer functions DC components

Geometric, DC magnetization, Saturation, Residual MB MQ (Decay &) Snapback predictions

b1, b2, b3, b5, a2, a3… Cycling prescriptions – all magnets Corrector Hysteresis

Handled on-line by LSA’s implementation of FiDeL Snapback “on the fly” invocation and incorporation

Import of FiDEL coefficients into LSA database in progress


Power converters

Load I(t) to all 1700 power converters Ramp won’t load if I(0) not within 0.01 of actual reference value 100 µs granularity up to 5000 points, maximum duration 400000 s. Linear interpolation of supplied points FGC runs full table – no stop/re-start Abort running ramp possible - don’t expect to keep the beam There can be no trims after loading the ramp Changes can still be put through the real time channel, however,

the real time TRIMs are not ramped Ramp start on receipt of timing event


RF Use multiplexed FGCs for function generation

The FGC2_RF will generate sixteen 16-bit integer functions at 1 kHz and will use the RFC-500 card to distribute the function values to the relevant nodes on the bus

Will ramp: 2*8*Cavity voltages & phase Coupler positions RF frequency (offset from 400 MHz). Both rings nominally locked

to the same frequency to avoid re-phasing before physics gain of the phase loop gain and time constant of the synchro loop Plus transverse damper etc.


Radial Loop

Fixed radial position, variable frequency Adjusts RF frequency to centre beam at pickup in IR4

measure frequency offset and feed correction forward into functions [LSA]

Choices Single pickup as planned Global orbit average – correct via RT system (robust) Two pick-ups at Pi Feed forward – check mean orbit – implies RT global orbit

acquisition – correct either radial loop reference or frequency


Beam Dump Loaded with the reference energy ramp On-line secure energy monitoring MSD/Q4 – FGC – I(t) locked in MKD, MKB kicker and MSD septum energy tracking

Extract single pilot at pre-defined energies in the ramp (calibrated points)

Check MKD kicker “fine” timing adjustment

Brennan Goddard

Cham 2006

Orbit/aperture

Extraction trajectory

Instrumentation

Kicker timings, retriggering

Post mortem and XPOC


LBDS beam commissioning – pilot beamLBDS beam commissioning activity LHC mode Beam type Energy GeV

Things to do before first pilot extraction

IR6 optics measurements Injection Circulating 1 pilot 450

Commission dedicated LBDS BDI in IR6 Injection Circulating 1 pilot 450

Extraction element aperture measurements Injection Circulating 1 pilot 450

… before first pilot ramp

First extractions: rough timing adjustment Inject & dump Extract 1 pilot 450

TD line BDI commissioning Inject & dump Extract 1 pilot 450

Extraction trajectory and aperture measurements Inject & dump Extract 1 pilot 450

Data diagnostics: IPOC, logging, FDs, PM, XPOC Inject & dump Extract 1 pilot 450

MKD waveform overshoot measurements Inject & dump Extract 1 pilot 450

MKB sweep measurements Inject & dump Extract 1 pilot 450

… with the pilot ramp

Energy tracking measurements Ramp Extract 1 pilot 450-7000

…before moving to operation with potentially “unsafe” beams

Fine timing adjustment Inject & dump Extract 2 pilots 450

Commission SW interlock on beam position at TCDQ Injection Circulating, safe beam 450

Commission IR6 orbit BPM interlock Injection Circulating, safe beam 450

Commission abort gap watchdog Injection Circulating, safe beam 450

TCDQ “injection setting” positioning Injection Circulating, safe beam 450

Fine timing in ramp Ramp Extract 2 pilots 450-7000

TCDQ positioning at 7 TeV Adjust/squeeze Circulating, 1 pilot 7000

= time consuming


Collimators

Motor positions(t) down loaded to controllers Functions triggered with timing event Settings maintained on LSA with full parameter space

defined (position, angle, emittance, Twiss etc.)

High Intensity ramp behaviour defined C. Bracco: Collimator settings during the energy ramping

Low Intensity ramp commissioning Cleaning not an issue, protection. Set TCDQ/TCS at ±10 at 450 GeV, primary at 7-8 Good enough for intermediate energies Provides protection at 7 TeV, but still might want to bring them in

Stefano and Delphine


Timing System

Timing table(s) pre-configured and loaded to the CBCM Start PC ramp Start RF ramp Start collimator ramp BPM – closed orbit/capture BLM – burst Fly Wire Scanner Etc. etc.

Executed on request by timing system


Measurements on ramp

Periodic BCT/Lifetime Synchrotron light monitors Beam Loss Monitors Schottky WCM

Continuous Tune PLL – clear priority Chromaticity

RF modulation (Synch with orbit -> dispersion) Ramp – different frf

“Slow” orbit acquisition ~ 1 Hz RT orbit acquisition ~10 Hz


Measurements at intermediate energies

Tunes, Chromaticity, Orbit, Coupling Tracking between sectors Transfer functions Beta beating


Feedback using the PLL tune system Tune feedback requirements

Stable PLL tune measurement system Knowledge of correction quad transfer functions

already known from initial tune corrections Implementation of feedback controller

Coupling feedback requirements Stable PLL tune measurement system Knowledge of skew quad transfer functions Implementation of feedback controller

Chromaticity feedback requirements Stable PLL tune measurement system RF frequency modulation

All of these will require dedicated beam time for testing the control loop response and the final closing of the loop.

Rhodri Jones


Machine Protection

Single beam through snapback

Switch to nominal cycle

Ramp – single beam

Single beam to physics energy

Two beams to physics energy

Start

End

Low intensity, single bunch, low energy... same as at 450 GeV BLMs: acquisition – no dump,

check losses against thresholds collimators & TDCQ coarse

settings

Critical machine protection systems must be in place minimum subset of BLMs

connected to beam interlock system

collimators interlocked in place local orbit stabilisation around

beam cleaning insertions and dump region

further commissioning of beam dump & BLMs

BEM & SBF

Overall strategy


Initial Ramp Commissioning

Baseline 450 GeV commissioning Snapback light pre-cycle Pilot beam Wait it out at injection Snapback using FiDeL predictions Ramp to reduced energy Recycle full machine Thus in seven steps with seven ramps to seven TeV Repeat for beam 2

Procedures


LHC Stage A: Commissioning phasesPhase 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.8 Snap-back and ramp: single beam

A.9 Top energy checks: single beam

A.6 450 GeV Two beam operation

A8.b Ramp two beams

A.10 Top energy checks: two beams

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

A.11 Top energy: collisions

A.12 Squeeze: commissioning the betatron squeeze in all IP's

Commission snap-back corrections Commission the RF up to top energy Commission beam dump and machine protection (MPS) at different

intermediate energies Commission BI acquisition in the ramp

Snap-back & Ramp with single pilot beam – Basic Objectives


Overview of Steps Involved

Step Activity Priority

A.8.1 Prepare ramp:Prepare ramp: Correction of snap-back and TRIM incorporation; beam 1

1

A.8.2 Ramp Ramp beam 1 up to pre-defined energy steps (E=1TeVE=1TeV); commission the RF systemRF system

1

A.8.3 CheckCheck the key instrumentationinstrumentation and control key beam beam parametersparameters: orbit, tune, coupling, chromaticity

1

A.8.4StopStop in the ramp and commission beam dumpcommission beam dump and machine machine protection systemsprotection systems at intermediate energies. Perform beam based checks at intermediate energies

1

A.8.5 Ramp to 7 TeVRamp to 7 TeV, beam 1 1

A.8.6 Repeat A.8.1 to A.8.5 for beam 2 1


Beam Entry Conditions

Beam Entry conditions: One bunch, Ib = 5x109 p to 3x1010 p Separate commissioning for beam 1 and beam 2 Nominal beam emittance (value agreed for ramping)

Beam tolerances: 450 GeV tolerances should also apply for the ramp as

the available beam aperture stays constant Need to allocate budgets for static and dynamic

tolerances Relaxed tolerances on key beam parameters


Entry conditionsEntry Description

E.A.8.1 First optimization of the machine at 450 GeV done

.01Tune, chromaticity, orbit, coupling measured and corrected beta beating at least measured. Aperture reasonably well established

.02 All circuits up to b3 commissioned – polarities check with beam, etc

.03 Collimators providing basic protection

.04PC OFF: Skew sextupoles; octupoles spool pieces; decapoles spool pieces; crossing angle; spectrometer magnets; experiments solenoids and separation bumps

E.A.8.2 Settings generation

.01LSA parameter space fully defined. Settings generation available and debugged. Ramps to pre-defined intermediate energies.

.02Decay/snapback effects will be handled by LSA’s implementation of FiDEL. Pre-cycles defined.

.03 RF functions (frequency & voltage etc.) available

.04Collimator ramp settings (not used initially but there with all functionality tested)


Entry conditions

Entry Description

E.A.8.3 Power Converters

.01 All operational functionality tested.

E.A.8.4 BI

.01 BCT commissioned

.02 Closed orbit acquisition

.03 PLL commissioned

.04 BCT & lifetime commissioned

.05 Synchrotron light monitors commissioned (not critical)

E.A.8.5 Feedbacks

.01 Orbit (1) and tune (2) feedbacks are the priority.


Entry conditions

Entry Description

E.A.8.6 Machine protection

.01 Critical BLMs commissioned and connected to the BIS

.02 Collimators interlocked in place

.03Local orbit stabilization around beam cleaning insertions and dump region

.04 Further commissioning of beam dump(*) and BLMs

.05 Intensity versus energy logic in SBF tested

E.A.8.7 Controls

.01 Timing system fully commissioned/input to equipment

.02 Ramp timing table populated

03 Logging & data acquisition criteria established


Stage A.8.1 – Prepare ramp

Step Activity Group Priority

A.8.1 Prepare ramp, single beam, ring 1

.01Snap –back prediction, incorporation into functions, decay at stop point to be anticipated

MA/OP 1

.02 450 GeV trim incorporation OP 1

.03 Prepare RF: RF/OP 1 Load RF functions Radial loop on – to be done after last injection and before start ramp


Stage A.8.1 – Prepare ramp


A.8.1 Prepare ramp, single beam, ring 1 (cont.) 1.04 Transverse feedback not needed in the first instance.05 Load Power Converters (Table) OP

.06Collimators (not ramped during first attempts to lower energy)

OP

.07 Timing table configured and loaded OP

.08 BLM thresholds up the ramp - check BI

.09 TDI, TCT, TCLI out. Kickers off.0.10 Check BLMs threshold table (energy dependence)


Stage A.8.2 – Ramp single beam


A.8.2 Ramp single beam; ring 1

.01 Send timing event: Start Ramp

.02Monitor: Lifetime, tunes, orbit, energy, beam losses, beam sizes (synchrotron light)

OP

.03 Measure: Capture losses (flash loss of out-of-bucket beam at start of ramp) Continuous measurements of frequency response of loops during ramp

RF Parasitic

Bunch length (emittance growth), RF noise RF Parasitic

.04Feed-forward of measured frequency offset for eventual switch to synchro-loop operation

RF 2 Parasitic


Stage A.8.2 – Ramp single beamStep Activity Group Priority

A.8.2 Ramp single beam; ring 1 (Cont.).06 Feedbacks:

Orbit feedback: Synchronized acquisition and feed-forward Global orbit feedback a.s.a.p.

OP 1

PLL: Continuous tune, coupling High priority: feed forward

OP/BI 1

Tune and coupling: First ramps can be attempted w/o these feedbacks, however, in our interest to commission them a.s.a.p. Critical will be measurements to monitor variations during snap-back and in the ramp

OP/BI 3

.07

Tracking: the real time orbit acquisition allows us to check the relative tracking during the ramp with similar or better accuracy in delta (use difference w.r.t. injection) as compared to injection

OP


Stage A.8.2 – Ramp single beam


A.8.2 Ramp single beam; ring 1 (Cont.)

.08 Transfer functions (may be difficult). MA

.09 Chromaticity OP/BI 1 RF modulation synchronized with orbit/dispersion 1

.10Beta beating measurement at intermediate energies – local orbit checks

OPABP


Stage A.8.3 – Post Ramp analysis


A.8.3 Post Ramp analysis

.01Feed-forward of measured frequency offset for eventual switch to synchro-loop operation

RF/OP

.02 Feed-forward of tune measurements ABP/OP 1

.03Analysis of orbit and feed-forwarded of orbit corrections (if GOFB not operational)

ABP/OP 1

.04Analysis of GOFB correction and feed-forward if operational

ABP/OP 2

.05 Beta beating ABP/OP


Stage A.8.4 – Beam at Intermediate EnergyStep Activity Group Priority

A.8.4 Beam at Intermediate Energy.01 Follow decay of tune, chromaticity and orbit OP/ABP 1

.02Measure tune, coupling, orbit – only correct if really required

OP/ABP 1

.03 Check optics OP/ABP 1

.04 Monitor beta beating OP/ABP.05 Beam dump commissioning AB/BT 1

Check energy tracking calibration (MKD, MSD, MKB) Orbit/aperture Extraction trajectory Instrumentation Kicker timings, retriggering Post mortem and XPOC


Stages A.8.5 – A.8.7A.8.5 Iterate:

• Dump at progressively higher energies: proposal: 7 steps from 450 GeV to 7 TeV

• Repeat previous stages at each benchmark energy• The full procedure will have to be repeated for beam 2

A.8.6 Commission Collimators in the ramp (Group Coll)

• Procedure should have essentially been commissioned without beam• Watch closed orbit at collimators and related beam losses • No cleaning issue for pilot.. Primary needs to be defined• 10 sigma TCDQ at 450 GeV, primary closer – could leave for first attempts • based on findings during 450 GeV optimization

A.8.7 Commission Feedback using PLL (Group BI)

• If at first you don’t succeed


Exit Conditions Reasonable transmission of pilot through snap-back (first

minute of the ramp) Single pilot at 7 TeV – ramp transmission good enough to

get pilot intensity up Beam dumps commissioned up to 7 TeV Machine Protection good for these intensities to 7 TeV

At the end of this phase:- we can proceed with top energy checks with single beam

What have we got?


Settings Generation

Optics & Twiss import Ramp & squeeze – all circuits Fully integration of LHC power converters Ramp and squeeze tests performed.

Driven by proto-sequencer

Collimators Inc. parameter space – Twiss parameters as functions

RF Incoming

BLMs Just started wrestling with the threshold tables


Collimators Stefano Redaelli


Ramping – IR8


FiDeL Marek


Timing Delphine Jacquet


Sequencer

Requirements specification Mike, Reyes & Fermilab

First prototype in place Tasks, sub-sequences, sequences, external conditions defined

on database

Demo

Vito Baggiolini

Roman Gorbonosov

Reyes Alemany

Greg Kruk

Mike Lamont


Upcoming tests

Ramp and squeeze tests during HWC Ongoing

Ramp tests in SM18 Hit instrumented MBs, MQ Effects of different pre-cycles etc. etc. Stephane Sanfilippo et al.

Dry magnet sector test

Other systems Hardware tests during HWC


Conclusions

Principles and mechanics understood

Procedures for initial commissioning pretty well established

Implementation of tools in progress

Tests planned

LHC Ramp Commissioning Mike Lamont Reyes Alemany-Fernandez Thanks to: Stefano, Verena, Walter.

Documents

lhc ramp parabolic

lhc ramp commissioning9

lhc ramp commissioning2

lhc ramp commissioning4

lhc ramp commissioning3

lhc ramp commissioning5

lhc ramp commissioning6

exponential ramp