Holzer, E B

CERN Document Server

BI GROUP COMMITMENTS AND MAJOR ISSUES FOR DISTRIBUTEDSYSTEMSE. B. Holzer, CERN AB/BI, Geneva, SwitzerlandAbstractThis presentation will detail BI responsibility and orga-nization for LHC distributed instrumentation, i.e. the beamposition monitoring system (BPM), the beam loss monitor-ing system (BLM) and the beam synchronous timing sys-tem (BOB). It will also present BI commitments on the re-quirements listed in the 2 previous sessions. In particular,it will address the BPM and BLM functionality and per-formance expected for the different operation stages andthe procedures and tests foreseen to reach these objectives.Finally, current major issues (i.e. uncovered requirements)and possible alternatives will be presented.BI RESPONSIBILITIESAB/BI will provide the monitors, the electronics, thefront end software and corresponding expert applicationsnecessary to develop, test, deploy, diagnose and maintainthe different instruments produced by the group.AB/BI is not responsible for any software above the BDIfront end servers necessary to operate the machine. There-fore, the BPM and BLM concentrators, the real-time feed-back loops, the fixed displays, the middle tier black boxes,the operational applications, the post-mortem applications,the video and the analog signal transmission are outside theresponsibility of the AB/BI group.Table 1 gives a list of the people in the AB/BI group re-sponsible for the different components of the BPM system,the BLM system and the BST system. All components ofthe BI mandate are covered. The commissioning expertsfor the BPM and the BLM system from the AB/ABP andAB/OP group are also shown in the table. The BOB systemwill be commissioned by AB/BI experts.BEAM SYNCHRONOUS TIMINGCommitmentsThe beam synchronous timing (BOB) consists of themaster (BOBM) and receivers (BOBR). The BOB systemis based on TTC technology. It will provide the 40 MHzbunch synchronous clock and the 11 kHz LHC revolutionfrequency to the LHC beam instrumentation. In addi-tion to these two basic clocks, it will allow the encodingof beam synchronous messages which can be updated onevery LHC turn. They will be used for LHC instrumen-tation triggering and broadcasting of the machine status(mode, intensity, energy, turn number, ...). The BOB sys-tem is expected to be available right from the start-up of theLHC, as soon as it receives the RF signal.ClientsThe BPM system relies on the BOB for orbit, trajectoriesand multi-turn acquisitions as well as for the post mortemfreeze trigger. The BLM will rely on the BOB only for thepost-mortem freeze and the logging trigger. The BOB willbe used by other instruments to synchronize themselves orto synchronize amongst each other (BTVM, BWS, BSRT,...). The machine status has also proven to be of interest tothe LHC experiments. They will receive this informationusing their standard TTC receivers and decoders [1].Testing PlansThe BOB system is a collaboration between the AB/COgroup and the AB/BI group. AB/CO is responsible for themaster hardware and the master firmware. AB/BI is re-sponsible for the master server, the master real-time task aswell as for the receiver hardware, firmware and software.In total, three BOB systems are foreseen, one for the SPS,and one for each of the two LHC beams. The functionalityof the recent BOB version two covers all the requirements.The system is being tested at the moment, and it will becommissioned on the SPS in 2006. Its performance will beassessed during the LHC sector test, using the SPS BOBmaster.BEAM POSITION MONITOR SYSTEMStatus of the BPM Electronic ComponentsThe network infrastructure, i.e. the optical cables, thecoaxial cables and the WorldFIP control links have alreadybeen installed. The analogue front-end part of the BPMsystem, the Wide Band Time Normalizer, was successfullytested in TI8 and the SPS in 2004. Series production of the4500 units is currently being launched. The Digital Acqui-sition Board, DAB64x, was designed by TRIUMF. Seriesproduction of the 1800 units has now started. The DAB64xcard is the BI standard module for the digital data acqui-sition of the BPM system, the BLM system, the fast beamcurrent transformer, the tune measurement system, the wirescanners and the luminosity monitors. The BPM acquisi-tion hardware is expected to be fully functional for the LHCstart-up.PerformanceFigure 1 gives the linearity and the noise level for theBPM system as a function of the number of charges perbunch. It can be seen that the BPM operating threshold ofapproximately    charges per bunch corresponds to 17%LHC Project Workshop - 'Chamonix XV'125Table 1: Responsibilities for the system components.Equipment ProjectLeaderMonitor Electronics FE Software Exp.Appl.CommissioningBOB J.J. Savioz n.a. J.J. Savioz P. Karlsson BLM, BPM expertsBPM R. Jones C. Boccard E. Calvo L. Jensen J. Wenninger (OP),W. Herr (ABP), Y.Papaphilippou (ABP)BLM B. Dehning E.B. Holzer C. Zamantzas,E. Effinger, J.EmeryS. Jackson R. Assmann (ABP),H. Burkhardt (ABP),J.B. Jeanneret (ABP),S. Gilardoni (ABP)of the nominal ion bunch intensity. This does not leavemuch margin for the ion commissioning. Table 2 showsthe rms resolution for pilot beams and for nominal intensitybeams. It should be possible to reach the nominal resolu-tion of 5 m on the global orbit measurement for Stage Irunning with 43 pilot bunches.CommissioningThis section describes the functionality and availabilityof the BPM system during the different stages of commis-sioning.Before Beam The system has been tested in the SPSand in the TI8 transfer line. The testing will continue in2006. The full calibration of the LHC acquisition chain ispart of the BPM hardware commissioning.First Turn As long as the beam synchronous timing(BST) is not available, the BPM will acquire data in anasynchronous mode. In this mode the system is auto-triggered and does not depend on any external timing.It is intended to have the BPM intensity measurementoperational for the start-up of the LHC, but at this momentit is not sure if the goal will be attained. The efforts are cur-rently concentrated on the completion of the position mon-itoring system. The intensity measurement has the nexthighest priority and the work on the required acquisitioncard will be started as soon as manpower becomes avail-able. This measurement implies a considerable amount ofadditional software as it uses the acquisition system of theposition measurement of the other LHC ring. During thismeasurement the positions in the second ring cannot bemeasured. Should the intensity measurement not be readyin time, it would not affect the position measurement.First few to 1000 Turns As soon as the BST systembecomes available, the BPM will be phased-in with theBST 40 MHz bunch synchronous clock. This can takeplace in parallel to the asynchronous acquisition of thebeam position. Once the BPM system is timed-in it willallow bunch tagging and turn tagging.Circulating Beam at 450 GeV Two modes of opera-tion will be available, the global orbit mode and the cap-ture mode. The global orbit mode requires the timing-in ofthe BST to be completed. It will provide the real-time orbitdata at 10 Hz and the full functionality of the post-mortem.The capture mode can be triggered on request. It will givebunch to bunch and turn by turn data on a selected num-ber of turns. This mode of operation can generate a largeamount of data and will require concentrators and powerfulanalysis software to be exploited.Snapback, Ramp and Squeeze At that time of com-missioning the real-time global orbit data will be availableas input to the orbit feedback correction. The concentrator,the feed-back algorithm and the real-time orbit correctionneed to be available to implement the orbit feedback.Cuts proposed on the Capture Mode for Stage IThe AB/BI group proposes the following limitations onthe capture mode for stage I of the commissioning, in orderto reduce the workload. The multi turn acquisition will beable to capture the position readings of either one user se-lected bunch or of the beam average for a maximum of upto 10000 turns. The acquisition will always be on consecu-tive turns and always on all BPMs at the same time.BEAM LOSS MONITOR SYSTEMStatusThe network infrastructure has been completed.Almost all detector components have been received. Theproduction of 40 ionization chambers has started at CERNin January 2006. In February 2006 the series productionof about 3800 chambers will start in IHEP, Prodvino, Rus-sia. A production rate of 20 chambers per day is foreseenin Prodvino. The total production time is about one year.LHC Project Workshop - 'Chamonix XV'126-5%-4%-3%-2%-1%0%1%2%3%4%5%1E+08 1E+09 1E+10 1E+11 1E+12Number of Charges per BunchPercentageErrorw.r.t.HalfRadius[%]Linearity - High SensitivityLinearity - Low SensitivityNoise - High SensitivityNoise - Low sensitivityPilot Nominal UltimateNominalPb ionPercentageErrorw.r.t.HalfRadius[%]Figure 1: Linearity and noise level as a function of the number of charges per bunch.Table 2: BPM rms resolutions for different intensitiesIntensity rms ResolutionPilot Bunch Trajectory (single shot) 200 mOrbit (224 turn average) 20 mNominal Bunch Intensity Trajectory (single shot, single bunch) 50 mTrajectory (average of all 2808 bunches) 5 mOrbit (average of all bunches over 224 turns) 5 mThe total production rate could possibly be increased, tobalance unforeseen delays. In case of problems with theproduction or installation, it would also be possible to in-stall a smaller number of monitors without compromisingthe beam loss measurements too much. However, it seemsunlikely that this option needs to be adopted. In additionto the ionization chambers, 320 secondary emission mon-itors will have to be produced. Prototypes have been suc-cessfully tested. Currently, improvements to the design arebeing tested. The production is foreseen to start beginningof 2007 and is expected to last two months. The secondaryemission monitors are expected to be ready for LHC com-missioning, but not for the sector test. The intensity of thesector test beam is expected to just about reach the satura-tion level of the ionization chambers, in case the total beamintensity is lost within one meter. Therefore, the secondaryemission monitors are not critical for the sector test.The installation of the electronic crates (456 in the tun-nel and 105 on the surface) and of their power supplieshas started. Pre-series (50 out of 750 cards) production ofthe tunnel acquisition card has started in December 2005.For the digital surface acquisition, series production of theDAB64x cards has started and pre-series (30 out of 400cards) production has started of the mezzanine card. The25 combiner cards for interlock and testing are still in thedesign phase.In summary, the BLM hardware is expected to be readyfor LHC start-up. The tasks which are still to be performedbefore the start-up, are: The post-mortem has to be addedto the DAB program. The testing of the communication ofthe FPGA with the threshold tables has to be finished. Thecombiner card has to be designed. And one additional highvoltage system test has to be implemented in the charge-to-frequency converter program.Threshold CalibrationFor the BLM system to fulfill the specifications, thethreshold tables have to be calibrated. These calibrationsare based on simulations [2]. In case the calibrations are notprecise enough, calibration measurements with the LHCbeam will have to be performed. The analysis effort ofthe BLM logging and post-mortem data will have to bestarted in 2006. The required tools are needed for the sec-tor test already. This analysis is essential for the calibrationof threshold tables on one hand and for the interpretationof BLM signal patterns (beam particle loss patterns) on theother hand. Very large amounts of data will have to be an-alyzed, when the beam commissioning starts. Extensivesoftware tools for data analysis will be required to fulfillLHC Project Workshop - 'Chamonix XV'127the specifications. We have to start now to specify and im-plement them. Equally important is an operational loggingand post-mortem system for the Sector Test.System TestsThe testing procedure are described in [3]. They havebeen defined in order to achieve the required reliability andavailability of the system. The functionality of all compo-nents will be tested before installation. Thereafter, thereare three different inspection frequencies: tests after instal-lation and during yearly maintenance, test before (each) filland tests which take place with beam, in parallel to the datataking. Figure 2 lists the most important tests and their fre-quency.Updating the Threshold TablesThe threshold tables can be downloaded on the charge-to-frequency converter card via the VME interface. Thispossibility will only be used in the lab. Before installationit will be disabled by a hardware switch. During LHC com-missioning and operation the threshold tables can only bechanged locally (i.e. in the surface buildings which housesthe electronics cards) via a dedicated interface.Conceptually, two different approaches will have to beused when changing the threshold tables. An empiricalprocedure needs to be defined to apply fast changes accord-ing to the needs of the LHC operation and within certainsafety limits. After an analysis of loss data, more funda-mental changes can be applied. They can then also affectthe energy and loss duration dependence of the thresholdvalues.For the generation, the failsafe management and thearchiving of the threshold tables software tools will have tobe specified and developed. It should be possible to groupmonitors according to magnet type for a faster changing ofthe threshold tables.SynchronizationFor reliability reasons the BLM system does not use anyexternal timing (other than the post-mortem and loggingtrigger). So the different DAB cards are not synchronizedamongst each other. Table 3 gives the duration of the 12time intervals over which the losses are integrated and therate with which the integrated values are refreshed. Everysecond an external logging trigger prompts the read out ofthe loss values. For the intervals below one second, themaximum value over the last second is sent for loggingand data display. For the larger intervals, the most recentvalue is sent. E.g. the integration window of 5.5 s is up-dated every 82 ms. At the time of the readout this value cantherefore not be older than 82 ms on any of the DAB cards.Hence, the maximum time jitter of all the 5.5 s values onall the DAB cards is 82 ms.Table 3: Refreshing rate of the 12 integration intervals ofthe BLM system.Moving Average Refreshing Rate40 s 40 s80 s 40 s0.3 ms 40 s0.6 ms 40 s2.6 ms 80 s10 ms 80 s82 ms 2.6 ms0.3 s 2.6 ms1.3 s 82 ms5.5 s 82 ms21 s 1.3 s84 s 1.3 sBLM for IonsConsiderably less beam loss simulations are available forthe ions than for protons. Therefore, the performance of theBLM system for ions has much higher uncertainties. Theions loss maps have been simulated for beam one and beamtwo [4]. These simulations yielded additional loss posi-tions left and right of the collimation regions in IR3 andIR7. Like in a spectrometer, the loss position of the dif-ferent ion species (which are produced through interactionin the collimator jaws) are fanned out over the dipole mag-nets. These simulations lead to the request for additionalmonitors. Error studies on the loss maps are foreseen to beperformed within the AB/ABP group.The bound free pair production (BFPP) has been sim-ulated for the interaction region of the ALICE experi-ment [5]. The simulation shows a localized loss position inD6 (Bernd?), which has to be monitored by an additionaldetector as well. The induced hadronic shower throughthe dipole magnet has been simulated [6]. This simulationshows that for the LHC main dipole magnets the ratio ofenergy deposited in the magnet versus the energy depositedin the BLM detector is roughly the same as for protons.The ratio of the quench (damage) level to the BLM signalis, therefore, about the same as for protons. This meansthat similar threshold tables can be used for protons andions. Also the shape of the hadronic shower is similar forions and protons. Hence the standard BLMs, which are in-stalled at local aperture limitations, are also well positionedfor ions. Future simulations of other electro-magnetic pro-cesses (which have a lower cross section) might lead to ad-ditional requests for BLM locations.LHC Project Workshop - 'Chamonix XV'128Radioactive source test (before start-up)Functional testsBarcode checkHV modulation test (implemented)Double optical line comparison (implemented)10 pA test (implemented)Thresholds and channel assignment SW checks (implemented)Beam inhibit lines tests (under discussion)DetectorTunnelelectronicsSurfaceelectronicsCombinerInspection frequency:Reception Installation and yearly maintenance Before (each) fill Parallel with beamCurrent source test (last installation step)Threshold table beam inhibit test (under discussion)Figure 2: Overview of the most important BLM testing procedures from [3]. The colored bars show what part of thesystem is tested and at what frequency.SUMMARYThe BST, the BPM (possibly excluding the intensitymeasurement) and the BLM hardware systems are expectedto be fully operational for the LHC start-up. The variousmodes of acquisition of the BPM system should allow thenecessary data to be available when they are required dur-ing the commissioning stages. To fulfill the specificationregarding the precision of the measurement of the quenchlevels, the BLM system needs to be calibrated. The calibra-tion requires the logging, the post-mortem and a system forthe management of critical settings to be available alreadyfor the Sector Test.ACKNOWLEDGMENTSThanks to J. J. Gras and Rh. Jones for their help inpreparing this contribution.REFERENCES[1] Rh. Jones, “The Interface and Structure of the MachineBeam Synchronous Timing Message for the LHC Ex-periments”, Functional specification, LHC-BOB-ES-0001,EDMS 638899.[2] B. Dehning, “Commissioning of Beam Loss Monitors”,Workshop Chamonix XV, Divonne-les-Bains, January 2006.[3] G. Guaglio, “Reliability of the Beam Loss Monitors Systemfor the Large Hadron Collider at CERN”, PhD thesis, Univer-site´ ClermontFerrand II - Blaise Pascal and CERN, December2005.[4] H. H. Braun et al., “Collimation of Heavy Ion Beams inLHC”, EPAC’04, Lucerne, Switzerland, 2004.H. H. Braun, “Collimation for heavy Ions”, LHC MachineAdvisory Committee Meeting no. 17, CERN, 10. June 2005.[5] J. M. Jowett et al, “Limits to The Performance of the LHCwith Ion Beams”, EPAC’04, Lucerne, Switzerland, 2004.[6] R. Bruce et al., “BFPP Losses and Quench Limit for LHCMagnets”, LHC Project Note 379, November 2005.LHC Project Workshop - 'Chamonix XV'129

BI Group Commitments and Major Issues for Distributed Systems

Abstract

Similar works

Full text

Available Versions

CERN Document Server