Collimator Setup Software in 2012
G. Valentino
R. W. Assmann, S. Redaelli and N. Sammut
LHC Collimation Working Group – 20 February 2012
Acknowledgements
• Colleagues who contributed to data-taking in the collimator setups (BE/ABP):
R. Bruce, F. Burkart, M. Cauchi, D. Deboy, L. Lari, A. Rossi, B. Salvachua,
D. Wollmann
• BE/BI:
B. Dehning, S. Jackson, C. Zamantzas
• EN/STI:
A. Masi
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Outline
•
The Setup Application in 2011
•
Setup Application for 2012
•
Demonstration Video
•
Ongoing Work
•
Summary
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The Setup Application in 2011
Main features:
– BLM feedback (jaws stop moving when losses exceed pre-defined threshold)
– Improved GUI
– Automated data logging (not fully exploited)
– Parallel collimator setup made possible
Achievements:
– Automation reduced the amount of operator intervention required
– Setup time reduced by up to a factor 6 for TCT alignment from 2010
– High BLM losses and resulting beam dumps from human error avoided
Issues:
– Optics had to be input manually: it was easier to use the excel sheets for logging
– Full automation not yet achieved (loss threshold, step size, time interval input
manually)
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Application Structure for 2012
User
Tested in
2011 MD
NEW
BLM Spike
Recognition
Loss Threshold
Selection
GUI
Data
Logging
Setup Task
Sequencer
NEW
Available
in 2011
BLM
Feedback
Available
in 2011
Parallel Setup
Algorithm
Tested in
2011 MD
Fast BLM Data
Acquisition
NEW
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Automatic BLM Spike Recognition
•
Automatic recognition of BLM spikes achieved using Support Vector Machines (SVMs)
•
Loss spikes are classified into 2 classes: optimal and non-optimal spikes
•
SVMs maximize the margin between the data points of different classes and the decision boundary
Discriminating Features:
Optimal Loss Spike
(a) ratio of maximum BLM value to average of 10
preceding BLM values
(b) coefficient of power fit to loss temporal decay
(c) correlation coefficient of power fit
20 seconds loss
pattern fed into the
SVM predictor
•
97% prediction accuracy from 480 samples (improvement from 90% achieved from data of July MD)
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Automatic Threshold Selection
•
A model based on Exponentially Weighted Moving Average (EWMA) was developed.
•
The largest weight is given to the most recent value.
•
The EWMA was calculated for 475 sets of 10 BLM values.
Threshold set by
the operator
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Setup Task Sequencer
Start
Move in B1 & B2 TCP
Loop executed for
each plane
Move B1 & B2
collimators in parallel
Align collimators
separately in sequence
NO
All collimators
aligned ?
YES
Stop
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Input Parameter Heuristics
• Heuristics derived from experience with manual and semi-automatic setup
Input Parameter
Heuristic
Jaw Step Size at 450 GeV
All collimators: 10 µm
Jaw Step Size at 4 TeV
TCT: 10 µm (larger beam size)
All other collimators: 5 µm
Jaw Movement Time Interval
1 s for 1 Hz BLM data
0.125 s for 12.5 Hz BLM data
BLM Threshold
Calculated from the latest 10 BLM values
before every jaw movement
After an optimal loss spike
Move in other jaw to align both jaws
After a non-optimal loss spike
Increase step size by 5 µm and move in jaw again
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Parallel Setup Algorithm
Start parallel jaw movement
After first jaw stops, wait for 2 s
in case of other stopping jaws
Are there other
stopped jaws?
NO
YES
Stop all movements and move
each of the stopped jaws
separately by a further 50 µm
NO
Are all collimators
close to the beam?
YES
Start sequential alignment
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Demo Video
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Fast BLM Data Acquisition
•
Fast BLM data acquisition possible thanks to C. Zamantzas and S. Jackson.
•
Data is sent via UDP packets from all BLM crates at a rate of 12.5 Hz (RS07, 81.92 ms).
•
A UDP client is implemented in setup application to receive packets and convert data to Gy/s.
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Fast BLM Data Video
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Setup Time: Theoretical Limit
•
Assumptions: (a) Each plane for B1 and B2 set up in parallel.
(b) Step size: 10 µm for all collimators.
(c) Each jaw needs to be moved for 7 mm (average) until it touches the beam.
(d) In sequential setup, each jaw needs to be moved in further by 200 µm
(average), B1 and B2 separately.
10 minutes per group
for parallel setup
recovery after cross talk
Parallel Setup
Sequential Setup
60 s delay per
collimator for
pattern recognition
and threshold
7000 ´ 3
N colls ´ 200 ´ 2
Tsetup =
+ 600 ´ 3+
+ N colls ´ 60
MRpar. ´10
MRseq. ´10
For
MRpar.
= 1 Hz,
MRseq. = 8 Hz and N colls= 84 :
Tsetup = 2 hours 30 minutes
factor 7 better than 2011
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Ongoing Work
•
1 hour without beam required for final testing and to determine the maximum number of
collimators that can be moved in parallel at 8 Hz. Tentative: Week 9 after MP tests.
•
When crosstalk occurs during setup, the collimators moving in parallel will be saved to avoid
these combinations in future.
•
BPM-interpolated orbit at the collimators will be compared to the beam-based centres.
•
If the BPM interpolation is consistently correct to within a certain value, the jaws can be
moved immediately to one location assuming a certain beam size, instead of parallel setup.
•
Models for threshold selection and spike recognition will be developed for the 12.5 Hz data.
•
Work on collimator setup LSA tables which will store a timestamp and the jaw alignment
positions is in progress (P. Pera Mira).
•
Logging application of fast BLM (and collimator?) data: ~45 GB/day – issue of storage
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Summary
•
A fully automatic setup procedure has been developed for 2012.
•
Models for automatic loss threshold selection and spike recognition were built based on 2011
setup data.
•
Setup task sequencer uses heuristics learned through setup experience to make decisions.
•
Increased automation and faster data rates expected to reduce the setup time hopefully by
factor > 3 from 2011.
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