I could be briefLHC OP days 2012 WHAT YOU GET ..

ORBIT / TUNE MEASUREMENT AND FEEDBACKM. ANDERSEN, C. BOCCARD, S. BOZYIGIT, E. CALVO, M. FAVIER, J. FULLERTON. GASIOR, S. JACKSON, L. JENSEN, R. JONES, T. LEFEVRE, A. MARGIOLAKIS, A. NOSYCH, J.J. SAVIOZ, R. STEINHAGEN, M. WENDT

And colleagues from BE-OP-LHC, BE-ABP, BE-RF, EN-MME, EN-STI

I could be brief Beam Position Monitor Orbit stability and temperature drift Update on BPM non-linearity correction Higher resolution orbit measurement with DOROS Status of Orbit feedback Status Interlock BPMs

Tune and Tune Feedback Upgrades and Develoment of Gated BBQ Tune feedback at 7TeV Schottky monitors after LS1

Detection and Measurement of Transverse Instabilities Time domain vs Frequency domain measurements Possible plan for LS1OUTLINEConcentrating on plans for LS1

I could be briefBPM - WBTNOrbit resolution measured ~few m (during MDs)

Main limitation from long term drift in position due to temperature variation in VME integrator mezzanine

Standard BPM calibration added to sequencer mitigates part of the problem not enough !!VME based Digital Acquisition Board and WBTN Mezzanine Cardsfrom 2010

I could be briefBPM Temperature issueRacks to be installed during LS1Thermalized Racks consist of:Heat exchanger (bottom)Air flow isolating wallsHigh constant speed fan (top)PID controlled water valve Tests performed in SUX1 for one year1 bin ~ 30um

I could be briefBPM non-linearity correctionsAverage error in beam allowed area: 1.1 mmMax error for on-diag beam: 6mm!Average error in beam allowed area: 30 umMax error for on-diag beam: < 100 umExisting non-linearity correction can be improved by using a 2-D cross-term polynomialEspecially for IR bumps and Dump line BPMs

BPM with DOROS DOROS is a new technique developed to process collimator BPM signals, robust and simple

Optimised for position resolution, absolute accuracy for centered beams No bunch-by-bunch measurement but could be gated (not implemented yet !)Tested in SPS on collimator BPM prototypeand in LHC @Pt 5 on BPMSW

*BPM with DOROS Resolution

I could be briefORBIT FEEDBACKI could be briefOrbit correction at IP to bring beams head-on (here B1H correction)Slow drift over the year not corrected by OFB.The F2F difference is very small and sufficiently good ( squeeze in collision) 80 mm7 mm rmsLHC does not work without orbit FB and overall performance 2010-2012 has been remarkable (Jorg W. BI Day 2012)Current correction quality limits (not yet a real problem):Arcs + most of the LSS: BPM F2F reproducibility 50 um rms. OK!Common regions 1,2,5 & 8, ~ 200 um rms (directivity of stripline BPM)

ORBIT FEEDBACKImprovements in hardware highly beneficial for OFBFor arcs limited by residuals after temp control (F2F:

Interlock BPMsPurposeTo ensure the orbit at the extraction septum MSD remains below 4mm, in order to maintain a safe extraction trajectoryLayout2 redundant BPMs added near TCDQ and 2 near preceding Q490 phase advance to minimise chance of an unfortunate orbit bumpuse standard LHC BPM analogue electronics BUT specific FPGA firmwareAll hardware detection and trigger of beam abort

BPMSA (.A/.B)BPMSB (.A/.B) Main window with 70 readings (BD1) out of limits over 100 turns (T1) triggers the system

Second window with 250 (BD2) out of limits over 10 turns (T2) to quickly catch fast orbit change

I could be briefInterlock BPMsNote: 1% ~ 130 um for LHC arc, ~220um for BPMSA and ~330um for BPMSB buttons

Modify attenuation to displace dynamic ranges

Current installation BPMSA (80mm ap.) have 4dB and BPMSB (130mm ap.) have 0 dB for P/P run

Interlock BPMs The system has suffered too many false dumps No known case where the interlock did not function when it should haveDifficult start in 2012 with initial problems coming from BI database No more issues once system tuned for the operational high intensity beams (low sensitivity mode triggering dumps @2E10 bunch intensity)Not so compatible with other tests (like proton-Lead) more sensitive to signal reflections in high sensitivity mode

New version of interlock firmware/fesa has been prepared .. not deployed yetVersion with more diagnostics - Installed on a test system since summer 2012Several issues found i.e. neither BPMS orbit reading nor the position thresholds took into account the electronic non-linearities

. Options for LS1Optimize the hardware to limit signal reflection (spurious beam count) and adjust the sensitivity ranges to operational scenarios (remotely controlled attenuators ?) if not enough.....duplicate the system: one for protons and one for lead ions physics ? New firmware customized for interlock BPMs only (more data for PM analysis) ? All of these choices have an impact for MP & need to be thoroughly discussed

I could be briefTUNE SystemsSystem hardware settings optimized for different beam configurations

TUNESettings of BBQ FE for different beam conditions Need to be put in operation through sequencer to use full BBQ capabilities

TUNE with FBMain issues with the LHC Tune system during last yearsTune FB triggering QPS (too fast voltage change) due to poor Q peak quality

Pending request for b/b tune measurements

Low S/N ratio for certain beam conditionsDamper system operated at high gain Large octupole currents and chromaticity

The peak finding challenge Solved by Gated BBQ system Gating on bunches for which the damper operates at lower gain Long development resulting in first prototype tested in summer 2012 Operational in 2012 with basic functionality

I could be briefGATED TUNEI could be briefgated BBQ = standard BBQ + RF switch + hybrid + attenuation

TUNE after LS1Installation of new pick-ups for Gated tune and better measurement of coupling

Software required to exploit full functionality of nominal and Gated BBQ Fesa and logging DB done already missing GUIs (bunch selection and bunch scans display )

Tune system compatibility with Damper should be even better (gated BBQ) with upgrades foreseen on the Damper (see Daniels talk)

QFB compatibility with QPS Better tune signal with GatingTE/MPE considers introducing 3 threshold levels after LS1 (instead of 2). Thresholds are not yet defined.. To be discussed.

I could be briefSCHOTTKY MONITORSRun With IONS in 2011 Run With Protons in 2012 The Schottky transverse signals are still good on B1H, for single and multi bunch measurements at injection and at stable beam.Too large coherent signals saturate and destroy the pre-amps in the other systems! (B2H pre-amp killed already)Good, high level Schottky signals on all ion fills, for B1H, B1V and B2H.

Reliable single bunch measurements for the tune, and possible also for the chromaticity measurements. Modification on the gating procedure of the B2V pick-up: Significant reduction of the coherent signal peaks, but no improvement of the transverse Schottky signal bumps.

Figure : Analogue Processing Chain describing the modified pickup plate with the addition of a gate and a 24 MHz filter (elements unlighted in yellow).

I could be briefSCHOTTKY MONITORSPlan for LS1: Make all 4 Schottky Monitors fit for Protons! Overhaul of the Schottky pick-upsReduction of the reflections for better return loss using a better overall match on the waveguide-to-coaxial transition (new transitions have to be manufactured)Systematic checks on test bench with stretched wire measurementsImprove the symmetry of opposite electrodes, e.g. lower tolerances, mechanical tuningCheck the transverse coupling impedanceReplace all internal SiO2 coaxial cables (some have a vacuum leak)

Overhaul of the RF signal processingModify the gating of all front-ends!New RF input filter to better cope with 25 ns bunch spacing.Probably new input amplifiers ?

Controls and softwareExtend the attenuator / phase shifter control to all systems.Adapt the front-end control software to the hardware modifications.Complete rearrangement / replacement of the Java user application software!

MONITORING INSTABILITIESObservation of instabilities in 2012 relied mainly on BBQ spectra and ADT activity (see daniels talk) LHC head tail monitors using fast sampling oscilloscopes limited to the detection of 100um oscillation amplitudes and limited in memoryDevelopment of high senstivity frequency domain detection system based on bandpass filters and diodesm=1m=2m=5m=1m=2m=5sum or 'm=0' signalChannel index 0 1 2 3 4 5...HT modesTimeFrequency

Input-SignalOutputfull-range1.6 GHz1.2 GHz0.8 GHz0.4 GHzHigh modulation-index @ 400 MHz indicates 'm1' head-tail motionPrototype tested on SPS in Summer 2012 ; Installed shortly after on LHCMONITORING INSTABILITIES

MONITORING INSTABILITIESProposal for LS1 more for discussion !

I could be briefCONCLUSIONS Improving the stability and accuracy of Beam Position Monitors Install thermalized racks for WBTN Use synchronous orbit mode for common region BPMs Implement better correction of non-linearities

Attractive option for high-resolution BPM using DOROS in LSSs BPMs

Modifications of Interlock BPMs to improve the system performance without compromising on reliability..

Gated Tune system has solved many issues in 2012 Full functionalities after LS1

OFB and QFB will get better with hardware upgrades Software review during LS1

Several technical solutions on offer for Instability measurements Need to agree on system architecture to be deployed after LS1 (BI, ABP, OP, RF)

I could be briefThanks again all the contributors to this talk !BI WATCH

Orbit resolution in LSSSubject: Cross-talk between both beams in insertion BPMs (stripline).Solution: Use synchronous mode with orbit calculated from single bunch which has no long range collision close to BPM location. Firmware deployed since January 2011.Action 2012:Mask needs to be configured for each BPM and dynamically as filling progressesThere is a (OP) person working on an application to do this automatically.

BPM non-linearity correctionsIssue with 10-20% scaling error in LSSs stripline BPMsNormaliser non-linearity and error in test-bench using BPM simulatorCheck with fixed attenuator found >8% error in worst case

Limitation due to limited directivity of stripline BPM in common vacuum chambers : (Cross talk between both beams) Mitigation using Synchronous Orbit Mode and selecting appropriate bunch Tested in MDs on one BPM To be deployed(contributions from OP)

Beam Position Monitors: BI MD4 IR8 scan (29 Nov. 2012)*BPMSW.1L8.B1B1 Vertical orbit. Snapshot in timeSingle-term poly usedDifference btw Optics prediction and BPM measurement: ~2mmEM Model: prediction map

GATED TUNEThe RF switch can accept some 30 Vpp, so smaller amplitudes needed (the standard BBQ handles 500 Vpp straight form the PU electrodes).An RF 180 hybrid used to subtract the pick-up electrode signals to decrease the signal level at the input of the RF switch.The hybrid cannot take the whole electrode signal power (>10 W). 10 dB attenuators are used, causing a sensitivity loss w.r.t. the regular BBQ.Sensitivity of the gated BBQ is decreased less than the attenuation, as the gated BBQ detector has only one diode, while the standard detector has 6 diodes to deal with the high electrode signal amplitude. The gated BBQ operates as the standard BBQ with one bunch (or a few bunches) in the machine . The whole acquisition chain and its software is the same.The above scheme started to be studied only in 2012, as a result of difficulties with the previous development based on a floating gate, which did not require signal attenuation. The current scheme with a series RF switch works only due to the fact that an RF switch was found, accepting signals with sufficiently high amplitudes, which are well above its data sheet spec. standard BBQgated BBQ = standard BBQ + RF switch + hybrid + attenuation

GATED TUNEoperation with positive beam offsetsthe implemented configuration: for operation with bipolar beam signalsoperation with negative beam offsets

MONITORING INSTABILITIESfrevfrev+fqfrev-fqfrevfrev+fqfrev-fq

This year 4 firmware versions were developed, but only the first was deployed to all the crates. The rest were under test is only special crates in P1,P5 and P6.

Current deployed DAB firmware: v.2012-1 (24-1-2012) added an automatic IIR setting.- Count the number of received Strobes during a programmable window, in order to Auto-select the Orbit filter according to this number.- Set the Interlock Alarm level = 0, in order to use the Alarm counter to count the received triggers.

Versions not yet deployed in all the creates:

v.2012-2 (4-4-12) : As. Orbit with increased resolution.v.2012-3 (15-6-12): Split criteria for interlocks triggering: bad acquisitions are not counted as bad positions. Different settings for triggering through errors or positions. More post-mortem data for analysis.v.2012-4 (10-10-12): Interlock Stop Trigger from BST P0 trigger. Allows freezing the PM buffers of all the interlocked channels when one of them triggers the interlock system.

DAB firmware in 2012:

1) New tool developed by OP and used at beginning of the year to check the BPM quality from the point of view of inverted polarities and scalar factors. The tool is based on kicks from 2 correctors at (almost) 90 deg phase advance. Fast (< 1 minute / beam /plane) check of the BPM response.Results:- Some scale issue possible (~ 20%) for IR BPMs. (from Jorg)- BPMS[WXY] calibrations are systematically 10% lower while the BPMS[AB] seem to be 10% higher (the data is in the logbook). We assumed that they should be the same. If we could confirm that the BPMSA have the same geometry/design as e.g. (from Ralphs email)- Warm BPM in LSS seems to have a 10-15% error on scaling factors according to Jorg's measurements. Witold said that he came up last year to the same feeling when analysing VdM scans data. (From Jean Jacques email).- It allowed to detect BPM wrong polarities at BPMSW1.L5 (due to an error when connecting the RF switches).2012 software upgrades/modifications

2) Sequencer task to calibrate automatically the SPS-LHC transfer lines before every LHC fill.

3) Expert GUI to calculate the temperature gradients of the LTI lines + FESA modifications to used the found them and compensate for temperature effects in the LTI trajectory.

4) New sequencer task selects the bunches without beam crosstalk to setup properly the synchronous orbit. - Required a FESA modification (orbitBunch) that was only deployed for testing in a special crate at P1. - Unfortunately, this crate overwrite some settings (bunch delay and phase clock) with every sequencer calibration, leading to a malfunction of the synchronous orbit. - Solution is found, make an LSA trim to correct the settings. - Tested at P1 during the collide and squeeze MD (MD#3) and during the 1km *.- Results were nice and seem to be ready to deploy.

2012 software upgrades/modifications

*