1. Chamonix 2006 – LHC Project Workshop
What is required to get the beam safely out of the LHC
B.Goddard AB/BT
Input from E.Carlier, J.Uythoven, R.Assmann, V.Kain, J.Wenninger + others
23 January 2006
Chamonix LHC Project

2. Outline of talk Beam dumping system :
Operational states and sequencing
Beam commissioning – what, when and how:
Overview of beam commissioning needed
Fitting into the overall LHC commissioning
Breakdown of individual LBDS beam tests
TCDQ positioning
Discussion points and conclusion
23 January 2006
Chamonix LHC Project

3. Scope I will focus on ‘Stage I’ as detailed earlier by Roger 1 pilot
43 bunches (41010 p+)
156 bunches ( 91010 p+)
Requirements for ‘Stage II’ are basically more of the same
23 January 2006
Chamonix LHC Project

4. Reminder Dilution kicker system MKB is staged (2H, 2V)
Limits extracted intensity at 7 TeV to 50% of nominal
For 25ns spacing, this is a limit on single bunch intensity, NOT on total in LHC
Not an issue for “Stage I” : could safely dump full beam intensity up to about TeV – (no interlock - rather unlikely to be needed in first few months…)
BTVDD trace – full dilution
BTVDD trace – staged MKB
Allowed dumped intensity (staged MKB)
23 January 2006
Chamonix LHC Project

5. Q: “when is the LBDS needed….”?
See J.Wenninger’s presentation !
System
Commissioning before beam possible ?
First pilot beam
10^12
43 bunches ^12
156 bunches ^12<N<1.4 10^13
936 bunches >5 10^13
Beam Dumping System 450 GeV
PARTIAL
Beam Dumping System 7 TeV
System tests, HWC and Reliability Run to validate internal dependencies of LBDS subsystems, and connection with MP systems (including BIS)
 no operational Beam Dump system = no Beam permit
However….LBDS can be “operational” for pilot intensity, but “not operational” for 43 bunch running
 need representation of “operational state” (LHC sequencer)
A: “day 1”
23 January 2006
Chamonix LHC Project

6. “Bootstrapping” the LBDS operational state
Need to drive LBDS operational state from “Not ready” to “Ready for beam”
Diagnostics IPOC, XPOC
Beam dump triggered
Arming procedure
Not ready
Ready for no beam
Ready for pilot
Tests with pilot beam
Ready for beam
LBDS operational states
BUT LBDS “Ready for beam” can’t distinguish between 1 or 2808 bunches of 1011 p+
need formal representation of the progress of the LHC commissioning process
could envisage MCS + SIS (plus sequencer?) to manage this
23 January 2006
Chamonix LHC Project

7. Safety critical aspects of the LBDS
Signal from beam interlock system (test in HWC/RR)
No trigger = no beam dump
Energy tracking
Potentially catastrophic (whole beam at “any” amplitude)
MKD retriggering (test in HWC/RR)
No retriggering could put whole 7 TeV beam at ~10s
TCDQ setting
Wrong w.r.t. orbit exposes LHC arc / triplets / collimators.
System self-tests and post-mortem
Undetected ‘dead’ MKD severely reduces reliability
Aperture, optics and orbit
Dump with bad orbit could damage extraction elements MSD, TCDS or MKB
MKD – MKB connection and sweep form
Insufficient dilution could damage TDE, BTVDD and TDE entrance window
Abort gap ‘protection’
Beam in the abort gaps risks quench, or TCT/LHC damage if TCDQ position error
Fault tolerance with 14/15 MKD
The system is designed to operate safely with only 14 out of the 15 MKDs
Nearly all aspects need beam commissioning (validation or optimisation)
23 January 2006
Chamonix LHC Project

8. LBDS beam commissioning in phase I
Pilot beam:
Before first extraction….
Before first ramp…
During ramp…
At 7 TeV…
Before moving to potentially unsafe beam:
Interlock commissioning
TCDQ positioning
43 bunches
Before first extraction…
156 bunches
23 January 2006
Chamonix LHC Project

9. Before first extraction…
Circulating beam, 1 pilot at 450 GeV
Optics and other measurements in IR6
Beta, dispersion, orbit correction, stability
Commission dedicated LBDS BDI for circulating beam
Synch BPM, BLMs (MKD, MSD, TCDS, TCDQ), check direct LBDS interlock BLM
Aperture measurement with circulating beam
MSD, TCDS, MKD, TCDQM
Opening for circulating beam (H plane) at TCDS and MSD
15.3 mm (n1=6.5)
20.8 mm (n1=7.0)
23 January 2006
Chamonix LHC Project

10. Before first pilot ramp…i
Extracted beam: GeV (inject & dump)
First extraction
Into “Inject & Dump” mode
“Rough” extraction timing
Adjust RF synch  MKD kick delay, S signal from IR6 BPM (UA access for each delay trim!)
Commission extraction line BDI
BTV (SE, D, DD), BPM (SE, D), BLMs, BCTs
Any major problems will be apparent at this stage!
23 January 2006
Chamonix LHC Project

11. Before first pilot ramp…ii
Extracted beam: GeV (inject & dump)
Verification of extraction trajectory and aperture
Vary orbit in IR6 and measure aperture at TCDS/MSD/TD line
Optimise extraction trajectory (orbit, MKD, MSD); define ‘reference’ (UA access for MKD trim!)
Define limits for interlock BPM reference
Explicit check that aperture is adequate for 14/15 MKD case
Unplugging 1 MKD is not desirable (interlocks to be strapped, undo HWC/RR validation, etc.)
Prefer to check by varying orbit in IR6 (1/15 of 270 mrad…)
Opening for extracted beam (H plane) at TCDS and MSD
Extracted beam aperture vs IR6 orbit {
MKD sweep
23 January 2006
Chamonix LHC Project

12. Before first pilot ramp…iii
Extracted beam: GeV (inject & dump)
Logging and fixed displays
Checks that the beam related data is being correctly acquired and displayed
XPOC basic functionality (trajectory, BLMs, BCT, kickers, BTVDD, …)
Check that XPOC validation is working correctly for pilot setup
Issue: safe change of configuration when changing beam. With MCS/SIS/sequencer?
BDI Post-Mortem data
Check that all beam-dependant transient signals from the LBDS systems are being PM’d
23 January 2006
Chamonix LHC Project

13. Before first pilot ramp…iv
Extracted beam: GeV (inject & dump)
MKD kick waveform measurements
Important for aperture at TCDS/MSD
BPMD, BTVDD and BLMs. inject & dump, vary injected bunch bucket (5 meas. points)
MKB sweep measurements
Important for MKB and TD line aperture
BPMD and BTVDD. inject & dump, vary injected bunch bucket (≈10 meas. points)
MKD kicker waveforms (current signal)
BTVDD ‘screenshot’
89 ms
bunch 1
bunch 1300
23 January 2006
Chamonix LHC Project

14. During ramp with pilot…
Extracted beam: GeV (dump in ramp)
MKD, MKB kicker and MSD septum energy tracking
Extract single pilot at pre-defined energies in the ramp (calibrated points)
Adjustment of kicker lookup tables means UA access
Time-consuming if done as dedicated measurement….need to organise in a quasi-parasitic way
Extraction with 2 pilots during the ramp is also needed to verify the abort gap timing… combine?
MKD lookup table calibration data
23 January 2006
Chamonix LHC Project

15. Before moving to unsafe beams…i
Extracted beam: GeV (inject & dump)
MKD kicker “fine” timing adjustment
Inject 2 pilots into positions 1 and 2808 (3.0 ms spacing)
Fine adjustment of MKD timing (IR6 synch BPMs and RF frequency)
Acquire last turn of bunch 2808 in LHC to verify MKD kick (0.5 s or 3 mrad)
bunch 1
turn n
270 mrad kick
bunch 2808
turn n-1
3 mrad kick
MKD kick waveform
3.0 ms
Note: this also needs to be checked through the ramp…
23 January 2006
Chamonix LHC Project

16. Before moving to unsafe beams…ii
Circulating beam: safe 450 GeV
Abort gap “watchdog”
Commission the link between the LBDS and the injections
Fine timing between IR6 and injections needs to be adjusted with beam
Interlock BPMs for IR6 maximum orbit
Interlocked to around ±3.6 mm. Threshold setting and tests
23 January 2006
Chamonix LHC Project

17. Before moving to unsafe beams…iii TCDQ
Circulating beam: GeV
Adjustment of TCDQ/TCS jaws to 450 GeV position (≈10 s)
Beam axis wrt jaw, adjustment of jaw tilt, movement cross-calibration
TCS – 2 jaws - more accurate movement - tighter setting (by ≈1 s)
Needs BLMs and collimator controls
Orbit at TCDQ
Measurement of beam axis
Circulating beam: safe GeV
Establish TCDQ movement function during ramp
Interdependence with collimation system
Circulating beam: safe 7 TeV
Establish TCDQ movement function during squeeze
Accurate adjustment of TCDQ and TCS jaws in final position
Establish reference settings for target b* during next phase of commissioning
Interdependency on collimation settings, and on orbit feedback
Iterations (changes of orbit, b-beat, b*) to finalise TCDQ reference function
This looks like a major workup!
23 January 2006
Chamonix LHC Project

18. Alternative for TCDQ setting during phase I…
TCDQ protects arc at 450 GeV and TCTs/triplets at 7 TeV squeezed
450 GeV - set TCDQ/TCS system up at ±10 s
Rely on ±4 mm interlock to protect arc (maximum excursion at TCDQ is ≈2 s )
Asynch dump with 156b, max. 2 bunches in interval 7-12 s  Safe for 450 GeV
7 TeV - pilot near to damage level - set TCDQ/TCS at ±10 s
Rely on 2-jawed TCS to protect the TCTs – don’t worry about the orbit
Keep TCTs at ≈20 s  protected for any orbit in IR6 (limits b* to 2 m)
Can then (if needed) delay final orbit feedback + TCDQ beam position + SW interlock full commissioning to b* <2 m
Should improve operational efficiency during stage I
Need to check through all detailed implications
Protection level with TCS - decide safe combinations of intensity/filling pattern
Optics control/knowledge at TCDQ, TCTs and triplets (plus orbit at TCTs/triplets)
23 January 2006
Chamonix LHC Project

19. Before first 43b ramp…
Extracted beam: 450 GeV (inject, fill & dump?)
Start with 43 pilots, to keep below the damage threshold
When this is OK, move to 43 bunches of 41010 for validation
Losses in extraction channel and along the dump line
Reduced sweep with staged MKB means generous TD aperture
Check BDI response
Logging, PM and XPOC validations
Establish new reference data for XPOC…
BPMD
BTVDD
23 January 2006
Chamonix LHC Project

20. Before first 156b ramp…
Extracted beam: 450 GeV (inject, fill & dump?)
As per 43b activities…
Plus…..TDE thermal behaviour?
≈10 kW for nominal beam at 7 TeV every 10 hours
Could load with ≈4 kW with repeated inject, fill & dump of 156 bunches…
23 January 2006
Chamonix LHC Project

21. 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
Extraction element aperture measurements
… before first pilot ramp
First extractions: rough timing adjustment
Inject & dump
Extract 1 pilot
TD line BDI commissioning
Extraction trajectory and aperture measurements
Data diagnostics: IPOC, logging, FDs, PM, XPOC
MKD waveform overshoot measurements
MKB sweep measurements
… with the pilot ramp
Energy tracking measurements
Ramp
…before moving to operation with potentially “unsafe” beams
Fine timing adjustment
Extract 2 pilots
Commission SW interlock on beam position at TCDQ
Circulating, safe beam
Commission IR6 orbit BPM interlock
Commission abort gap watchdog
TCDQ “injection setting” positioning
Fine timing in ramp
Extract 2 pilots
TCDQ positioning at 7 TeV
Adjust/squeeze
Circulating, 1 pilot
7000
= time consuming
23 January 2006
Chamonix LHC Project

22. LBDS beam commissioning – 43b
LBDS beam commissioning activity
LHC mode
Beam type
Energy GeV
Things to do before first 43b extraction
Orbit feedback / stability checks at TCDQ
Injection
Circulating, 43b
450
… before first 43b ramp
Extraction trajectory checks
Inject & dump
Extract 43 pilots
TD line BDI checks
Extract 43b
Data diagnostics: XPOC
… with the 43b ramp
Energy tracking and abort gap timing checks
Ramp
… with 43b at 7 TeV
TCDQ positioning at 7 TeV
Adjust/squeeze
7000
23 January 2006
Chamonix LHC Project

23. LBDS beam commissioning – 156b
LBDS beam commissioning activity
LHC mode
Beam type
Energy GeV
Things to do before first 156b extraction
Orbit feedback / stability checks at TCDQ
Injection
Circulating, 156b
450
… before first 156b ramp
Extraction trajectory and BDI checks
Inject & dump
Extract, 156 pilots
Extract, 156b
Data diagnostics: XPOC
TDE thermal behaviour
… with the 156b ramp
Energy tracking and abort gap timing checks
…with 156b at 7 TeV
TCDQ positioning at 7 TeV
Adjust/squeeze
7000
This is essentially the same list of activities as from pilot to 43b.
It will be essentially the same list for all major changes in LHC beam (filling pattern, significant intensity steps, optics, emittance, …)
23 January 2006
Chamonix LHC Project

24. Unfinished business… Inject and dump mode Diagnostics
Needed from first extractions, for efficient commissioning
Details to finalise (timing, PM/logging,, multiple injections, turn delays, HW,SW)
Diagnostics
Split between IPOC, XPOC, logging and PM; XPOC configurations
Abort gap monitoring and cleaning in phase I
Assumed not needed for protection - could be important for efficiency
Topic for another day…
Ensuring that only ‘authorised’ beam can be used
Operational states and allowed LHC beam conditions – MCS, SIS and sequencer
Halo at TCDQ
Effect of “minimum collimation” strategy – risk of frequent Q4 quenches
FLUKA energy deposition simulations give cause for concern – work ongoing
Beam 2 will be worse….not checked yet
23 January 2006
Chamonix LHC Project

25. Conclusion LBDS beam commissioning for phase I operation:
will depend heavily on HWC/RR;
Validation of subsystem interconnectivity and reliability assumptions
Many key elements will be fully commissioned without beam
requires careful commissioning with pilot beam;
At 450 GeV before extraction, to check the optics and aperture
At 450 GeV in “Inject & Dump” mode, to check the LBDS functioning
During the ramp, to check the energy tracking
requires specific checks when LHC beam changes;
To verify instrument response, diagnostics and losses
can be somewhat relaxed for difficult TCDQ/TCS positioning;
By taking advantage of limited b* squeeze and number of bunches
23 January 2006
Chamonix LHC Project

26. 23 January 2006
Chamonix LHC Project

27. LBDS functional dependencies - overview
23 January 2006
Chamonix LHC Project

28. External “subsystems” requiring beam
LHC control system
Ethernet
LBDS
DCCTs
Access
BPM IR6
Fast timing
(RF synch)
BLM6
TCDQ
position
Direct triggers (to TSU)
Slow
timing
Abort gap
monitor
Emergency
stop status
IR6 PM
trigger
Mains &
UPS status
IR6 orbit
feedback
External
outputs
External
inputs
Machine
Protection
interfaces
SLP
Injection
BIC interface
Software
interlock
LHC beam permit loop
23 January 2006
Chamonix LHC Project

29. Primary LBDS failure catalogue

30. Lookup tables in the LBDS
Lookup tables within Beam Energy Tracking sub-system to convert physical measurements to energy
Conversion of main bending currents to energy
Conversion of energy to kicker voltage references
Conversion of extraction septa currents to energy
Conversion of ring quadrupole Q4 currents to energy
Conversion of kicker voltages to energy
Modification (e.g. adjust MKD strength)  reprogram local FPGAs
E.Carlier
23 January 2006
Chamonix LHC Project

31. Look-Up Tables - Which Type and Where
Acquisition
Settings
Main
Bends
Normalisation to Beam Energy
Operational Settings
Kicker HV
Generators
ImeasA
EbeamA
UrefKi
Reference
UmeasKi
Kicker HV
Generators
Q4 & Septa Magnets
EbeamKi
Tracking Interlock Logic
|EbeamB – EbeamKiMi| > 0.5% * EbeamB
Normalisation to Beam Energy
ImeasMi
EbeamMi
Main
Bends
Normalisation to Beam Energy
Imeas B
EbeamB
Dump Trigger Request
Interlock
Acquisition
Tracking
First Order Interpolation
Memory Map
23 January 2006
Chamonix LHC Project

32. Energy tracking performance
Power converter DCCT precision
±0.1 %
Kicker HV divider precision
±0.2 %
BEA sampling frequency
65 kHz
BEA resolution
16 bit
BEA–BEM / BEI transmission rate
~100 kbit/s
Error during ramp (10 A/s)
 0.01%
Bending magnet look-up table precision
Kicker magnet look-up table precision
Beam energy reference error (with interlock on RF & Sextupole)
±0.4 %
BEI tracking frequency
1 kHz
BEI tracking reaction time
1 ms
Bending magnet tolerance window
 ±0.3 %
Kicker magnet tolerance window
 ±0.5 %
23 January 2006
Chamonix LHC Project

33. “Bootstrapping” the LBDS operational state
BUT LBDS “Ready for beam” can’t distinguish between 1 or 2808 bunches of 1011 p+
need formal representation of the progress of the LHC commissioning process
could envisage MCS + SIS (plus sequencer?) to manage this
Ready for pilot
LBDS
“Ready for pilot”
commission pilot
prepare for bunches
Ready for bunches
commission 43 bunches
prepare for bunches
Ready for bunches
LBDS always
“Ready for beam”
commission 156 bunches
prepare for bunches
Ready for bunches
commission 936 bunches
prepare for bunches
Ready for 2808 bunches
commission 2808 bunches
LHC state
Inside each activity are commissioning steps for LBDS, which must be completed and “signed-off” before overall LHC is declared “Ready” for next stage.
23 January 2006
Chamonix LHC Project

34. Areas for concern – halo at TCDQ
Effect of “minimum collimation” strategy
High load on TCDQ risks frequent Q4 quenches
Load from beam tracking: input for FLUKA energy deposition simulations
Beam 2 will be worse – not checked yet
Thermal load in Q4 coil due to halo
no beam cleaning
nominal cleaning
0.03mW/cm3
15mW/cm3
A.Presland
23 January 2006
Chamonix LHC Project