Transcript LHC Ramp Commissioning Mike Lamont Reyes Alemany-Fernandez

LHC Ramp
Commissioning
Mike Lamont
Reyes Alemany-Fernandez
Thanks to: Stefano, Verena, Walter
LHC ramp commissioning








Ramp generalities
Overall strategy
Beam entry conditions and tolerances
Entry conditions
Procedures
Exit conditions
What’s in place
Upcoming tests
9/5/2007
LHC ramp commissioning
2
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
9/5/2007
LHC ramp commissioning
3
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
9/5/2007
LHC ramp commissioning
4
Nominal cycle
PHYSICS
BEAM DUMP
9
14000
8
SQUEEZE
7
PREPARE
PHYSICS
RAMP DOWN
6
PHYSICS
I~t
5
PREINJECTION
PLATEAU
4
B [T]
MB current
START RAMP
3
INJECTION
I ~ et
T0
2
I ~ t2
Tinj
1
0
Injection plateau -3000
alpha
current rate end snapback
current at injection
current variation during snapback
parabolic segment duration
current at end exp
b at end exp
current to field scaling factor
max current rate
current rate end parablolic
9/5/2007
exp time constant inverse
-2000
0 -1000
5.92105E-06
0.6
760
20
405.333
4110.000
3.000
1370.000
10.000
3.648
LHC
2.433E-03
0
Time [s]
ramp commissioning
1000
2000
Ramp down
0
3000
 18 Mins
Pre-Injection Plateau
15 Mins
Injection
 15 Mins
Ramp
Squeeze
 28 Mins
 5 Mins
Prepare Physics
Physics
 10 Mins
10 - 205 Hrs
Possible variations

Skip exponential




Slower snapback


Measurements planned to check dependency
Programmed stop in ramp


Ramp induced inter-strand coupling currents small
Simplifies ramp structure – easier to stop anywhere
Cost – one minute per ramp
Parabolic – (Linear) - Parabolic
Pre-cycle (as entry condition)

9/5/2007
Snapback minimization – particularly during commissioning
LHC ramp commissioning
6
Stopping with beam in the ramp
Used for commissioning of beam dump, beam loss monitors,
beam measurements, optics checks, physics...

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.



9/5/2007
requires a new set of functions to be loaded
including corrections for handling the associated snapback
during commissioning will be dumping the beam
LHC ramp commissioning
7
Settings/Trim
LSA



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.
9/5/2007
LHC ramp commissioning
8
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
9/5/2007
LHC ramp commissioning
9
Power converters

Load I(t) to all 1700 power converters









9/5/2007
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
LHC ramp commissioning
10
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:






9/5/2007
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.
LHC ramp commissioning
11
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




9/5/2007
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
LHC ramp commissioning
12
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)
Orbit/aperture
Check MKD kicker “fine” timing adjustment
Extraction trajectory
Instrumentation
Kicker timings, retriggering
Post mortem and XPOC
Brennan Goddard
Cham 2006
9/5/2007
LHC ramp commissioning
13
LBDS beam commissioning – pilot beam
LBDS 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
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
Ramp
Extract 1 pilot
450-7000
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
… before first pilot ramp
… with the pilot ramp
Energy tracking measurements
…before moving to operation with potentially “unsafe” beams
= time consuming
9/5/2007
LHC ramp commissioning
14
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.)
Stefano and Delphine

High Intensity ramp behaviour defined


C. Bracco: Collimator settings during the energy ramping
Low Intensity ramp commissioning




9/5/2007
Cleaning not an issue, protection.
Set TCDQ/TCS at ±10 s at 450 GeV, primary at 7-8 s
Good enough for intermediate energies
Provides protection at 7 TeV, but still might want to bring them in
LHC ramp commissioning
15
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
9/5/2007
LHC ramp commissioning
16
Measurements on ramp

Periodic






BCT/Lifetime
Synchrotron light monitors
Beam Loss Monitors
Schottky
WCM
Continuous


Tune PLL – clear priority
Chromaticity




9/5/2007
RF modulation (Synch with orbit -> dispersion)
Ramp – different frf
“Slow” orbit acquisition ~ 1 Hz
RT orbit acquisition ~10 Hz
LHC ramp commissioning
17
Measurements at intermediate energies




Tunes, Chromaticity, Orbit, Coupling
Tracking between sectors
Transfer functions
Beta beating
9/5/2007
LHC ramp commissioning
18
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
9/5/2007
LHC ramp commissioning
19
Machine Protection
Star
t
Low intensity, single bunch, low
energy... same as at 450 GeV
BLMs: acquisition – no dump,
check losses against thresholds
 collimators & TDCQ coarse
settings
Switch to nominal cycle

Single beam through snapback
Ramp – single beam
Critical machine protection systems
must be in place

Single beam to physics energy


Two beams to physics energy

End

9/5/2007
LHC ramp commissioning
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
20
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
9/5/2007
LHC ramp commissioning
22
Procedures
LHC Stage A: Commissioning phases
Phase
A.1
A.2
A.3
A.4
A.8
A.9
A.6
A8.b
A.10
A.5
A.11
A.12
Description
Injection and first turn: injection commissioning; threading, commissioning beam instrumentation.
Circulating pilot: establish circulating beam, closed orbit, tunes, RF capture
450 GeV initial commissioning: initial commissioning of beam instrumentation, beam dump
450 GeV optics: beta beating, dispersion, coupling, non-linear field quality, aperture
Snap-back and ramp: single beam
Top energy checks: single beam
450 GeV Two beam operation
Ramp two beams
Top energy checks: two beams
450 GeV Increasing intensity: prepare the LHC for unsafe beam
Top energy: collisions
Squeeze: commissioning the betatron squeeze in all IP's
Snap-back & Ramp with single pilot beam – Basic Objectives




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
9/5/2007
LHC ramp commissioning
24
Overview of Steps Involved
Step
A.8.1
A.8.2
A.8.3
A.8.4
A.8.5
A.8.6
9/5/2007
Activity
Priority
Prepare ramp: Correction of snap-back and TRIM
incorporation; beam 1
Ramp beam 1 up to pre-defined energy steps (E=1TeV);
commission the RF system
Check the key instrumentation and control key beam
parameters: orbit, tune, coupling, chromaticity
Stop in the ramp and commission beam dump and machine
protection systems at intermediate energies. Perform beam
based checks at intermediate energies
Ramp to 7 TeV, beam 1
Repeat A.8.1 to A.8.5 for beam 2
LHC ramp commissioning
1
1
1
1
1
1
25
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
9/5/2007
LHC ramp commissioning
26
Entry conditions
Entry
Description
E.A.8.1
First optimization of the machine at 450 GeV done
Tune, chromaticity, orbit, coupling measured and corrected
beta beating at least measured. Aperture reasonably well established
All circuits up to b3 commissioned – polarities check with beam, etc
Collimators providing basic protection
PC OFF: Skew sextupoles; octupoles spool pieces; decapoles spool
pieces; crossing angle; spectrometer magnets; experiments solenoids
and separation bumps
Settings generation
LSA parameter space fully defined. Settings generation available and
debugged. Ramps to pre-defined intermediate energies.
Decay/snapback effects will be handled by LSA’s implementation of
FiDEL. Pre-cycles defined.
RF functions (frequency & voltage etc.) available
Collimator ramp settings (not used initially but there with all functionality
tested)
.01
.02
.03
.04
E.A.8.2
.01
.02
.03
.04
9/5/2007
LHC ramp commissioning
27
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.
9/5/2007
LHC ramp commissioning
28
Entry conditions
Entry
Description
E.A.8.6 Machine protection
.01 Critical BLMs commissioned and connected to the BIS
.02 Collimators interlocked in place
Local orbit stabilization around beam cleaning insertions and dump
.03
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
9/5/2007
LHC ramp commissioning
29
Stage A.8.1 – Prepare ramp
Step
Activity
A.8.1 Prepare ramp, single beam, ring 1
Snap –back prediction, incorporation into functions,
.01
decay at stop point to be anticipated
.02 450 GeV trim incorporation
.03 Prepare RF:
 Load RF functions
 Radial loop on – to be done after last injection and
before start ramp
9/5/2007
LHC ramp commissioning
Group
Priority
MA/OP
1
OP
RF/OP
1
1
30
Stage A.8.1 – Prepare ramp
Step
Activity
Group
A.8.1 Prepare ramp, single beam, ring 1 (cont.)
.04 Transverse feedback not needed in the first instance
.05 Load Power Converters (Table)
Collimators (not ramped during first attempts to lower
.06
energy)
.07 Timing table configured and loaded
.08 BLM thresholds up the ramp - check
.09 TDI, TCT, TCLI out. Kickers off.
0.10 Check BLMs threshold table (energy dependence)
9/5/2007
LHC ramp commissioning
Priority
1
OP
OP
OP
BI
31
Stage A.8.2 – Ramp single beam
Step
Activity
Group
A.8.2 Ramp single beam; ring 1
.01 Send timing event: Start Ramp
Monitor: Lifetime, tunes, orbit, energy, beam
.02
losses, beam sizes (synchrotron light)
.03 Measure:
 Capture losses (flash loss of out-of-bucket beam
at start of ramp)
 Continuous measurements of frequency
response of loops during ramp
 Bunch length (emittance growth), RF noise
Feed-forward of measured frequency offset for
.04
eventual switch to synchro-loop operation
9/5/2007
LHC ramp commissioning
Priority
OP
RF
Parasitic
RF
Parasitic
RF
2
Parasitic
32
Stage A.8.2 – Ramp single beam
Step
Activity
Group
Priority

OP
1

OP/BI
1
OP/BI
3
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.

PLL:
Continuous tune, coupling
 High priority: feed forward

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
Tracking: the real time orbit acquisition allows us to
check the relative tracking during the ramp with
.07
similar or better accuracy in delta (use difference
w.r.t. injection) as compared to injection
9/5/2007
LHC ramp commissioning
OP
33
Stage A.8.2 – Ramp single beam
Step
Activity
Group
Priority
A.8.2 Ramp single beam; ring 1 (Cont.)
.08 Transfer functions (may be difficult).
.09 Chromaticity

.10
9/5/2007
MA
OP/BI
RF modulation synchronized with orbit/dispersion
Beta beating measurement at intermediate energies
– local orbit checks
LHC ramp commissioning
1
1
OPABP
34
Stage A.8.3 – Post Ramp analysis
Step
Activity
Group
Priority
A.8.3 Post Ramp analysis
.01
Feed-forward of measured frequency offset for
eventual switch to synchro-loop operation
.02 Feed-forward of tune measurements
Analysis of orbit and feed-forwarded of orbit
.03
corrections (if GOFB not operational)
Analysis of GOFB correction and feed-forward if
.04
operational
.05 Beta beating
9/5/2007
LHC ramp commissioning
RF/OP
ABP/OP
1
ABP/OP
1
ABP/OP
2
ABP/OP
35
Stage A.8.4 – Beam at Intermediate Energy
Step
Activity
A.8.4 Beam at Intermediate Energy
.01 Follow decay of tune, chromaticity and orbit
Measure tune, coupling, orbit – only correct if
.02
really required
.03 Check optics
.04 Monitor beta beating
.05 Beam dump commissioning
 Check energy tracking calibration (MKD, MSD,
Group
Priority
OP/ABP
1
OP/ABP
1
OP/ABP
OP/ABP
AB/BT
1
1
MKB)
Orbit/aperture
 Extraction trajectory
 Instrumentation
 Kicker timings, retriggering
 Post mortem and XPOC

9/5/2007
LHC ramp commissioning
36
Stages A.8.5 – A.8.7
A.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
9/5/2007
LHC ramp commissioning
37
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
9/5/2007
LHC ramp commissioning
38
What have we got?
Settings Generation




Optics & Twiss import
Ramp & squeeze – all circuits
Fully integration of LHC power converters
Ramp and squeeze tests performed.


Collimators


Inc. parameter space – Twiss parameters as functions
RF


Driven by proto-sequencer
Incoming
BLMs

9/5/2007
Just started wrestling with the threshold tables
LHC ramp commissioning
40
Collimators
9/5/2007
Stefano Redaelli
LHC ramp commissioning
41
Ramping – IR8
9/5/2007
LHC ramp commissioning
42
FiDeL
9/5/2007
Marek
LHC ramp commissioning
43
Timing
9/5/2007
Delphine Jacquet
LHC ramp commissioning
44
Sequencer

Requirements specification


First prototype in place


Mike, Reyes & Fermilab
Tasks, sub-sequences, sequences, external conditions defined
on database
Demo
Vito Baggiolini
Roman Gorbonosov
Reyes Alemany
Greg Kruk
Mike Lamont
9/5/2007
LHC ramp commissioning
45
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

9/5/2007
Hardware tests during HWC
LHC ramp commissioning
46
Conclusions
 Principles
and mechanics understood
 Procedures
for initial commissioning
pretty well established
 Implementation
 Tests
9/5/2007
of tools in progress
planned
LHC ramp commissioning
47