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Operational Aspects of the North Area in CERN Secondary Beam Line Complex

This article provides an overview of the operational aspects, access system, and radiation protection issues in the North Area of the CERN Secondary Beam Line Complex.

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Operational Aspects of the North Area in CERN Secondary Beam Line Complex

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  1. North Area, P42+K12, Compass, CNGSEdda Gschwendtner, AB/ATB Edda Gschwendtner

  2. Outline • Introduction • North Area • P42 & K12 • Compass • Operational Aspects • Access System • CNGS • Overview • Operational Aspects • Access & Radiation Protection Issues Edda Gschwendtner

  3. Introduction Edda Gschwendtner

  4. The CERN Secondary Beam Line Complex SPS North Area • Three experimental halls : EHN1, EHN2, ECN3 , 3 service buildings • 7 beam lines ; ~1000 equipment installed ; total length 5.8 km • ~2000 users / year performing experiments and tests ; frequent changes of beam configuration and settings Edda Gschwendtner Introduction

  5. The CERN Secondary Beam Line Complex PS East Area • 5 beam lines ; ~120 equipment installed ; total length 300m • ~300 users / year performing experiments and tests Edda Gschwendtner Introduction

  6. The CERN Secondary Beam Line Complex CNGS • 1 beam line ; ~50 equipment installed ; total length 1 (+732) km • LNGS experiment Edda Gschwendtner Introduction

  7. Introduction • The SPS North Area was originally designed to house long-lasting experiments • demands for high quality of beams: high intensity, high energy, high resolution • In the recent years most of the users are “tests” • in particular of LHC detectors with permanent or “semi-permanent” BIG installations • several users from astro-particle experiments and linear colliders • The test users have very different requirements from the big experiments: • scan the full energy range ; typically [10, 300] GeV/c • with sometimes increased precision (linearity) requirements • use beams of all particle types (electrons, pions, protons, muons) • with as good as possible separation and identification • and, sometimes request high (or very high) rates and all that during the few (or even one!) week(s) of their allocated time! Rapidly changing environment, quite demanding on beam conditions and tunes Edda Gschwendtner Introduction

  8. Ingredients • Bends • Correction dipoles (Trims) • Targets • Beam Instrumentation • Steering • Momentum Measurement • Particle Identification • Timing/Spill • Clean-up of Beam • Collimators (TAX, momentum, acceptance, cleaning collimators) • Scrapers and MIBS • Absorbers, Converters, Filters • Interlocks and Safety • Access Doors • Dumps • Shielding • Fences Edda Gschwendtner Introduction

  9. Primary p beam (400 GeV/c) Secondary particles ( 400 GeV/c) Target Development of hadronic shower Attenuated proton beam Particle Production Particle production downstream the primary target • Protons: remnant of the incoming primary beams • the target actually serves as attenuator • ~40% of the initial incoming intensity of the beam • Pions (hadrons): produced in hadronic interactions • Typical scale: interaction length (lint) • Electrons : produced in electromagnetic processes • Typical length scale : radiation length (X0) • Muons : produced in the decay of pions • At the target and also along the beam line Edda Gschwendtner Introduction

  10. Particle Production Target material and length • The proton intensity on each target can go up to 1.4 1013 protons/pulse • limited by target and TAX absorber construction (i.e. cooling, etc.) • The material with largest ratio: Xo/lint is preferred  Beryllium • Increasing the target length: • more production but also more re-absorption • lower the energy of the outgoing particles Optimal choice ~ 1 interaction length Edda Gschwendtner Introduction

  11. Muon beam Muon beams are formed by the decay of pions (p+, or p-) Decay kinematics: At the pion center of mass system: At the laboratory frame – boost Limiting cases: Conclusion: the muon beam energy is in the interval [0.57,1.0] of the initial pion beam energy m (p*, E*) q* n m Particle Production Edda Gschwendtner Introduction

  12. North Area Edda Gschwendtner

  13. North Area • The proton beam (400 GeV/c) from SPS is slowly extracted to the North Area at LSS2 • The extracted beam is transported in the TT20 tunnel • 11% slope to arrive into TCC2 – then horizontal ; ~10m underground • The primary proton beam is split in three parts directed towards to the North Area primary targets: T2, T4 and T6 11% slope Edda Gschwendtner North Area

  14. North Area The SPS North Area Beams • The three proton beams are directed onto the primary targets: • T2  H2 and H4 beam lines • T4  H6, H8, and P0 beam lines • T6  M2 beam line and Experimental Areas: • ECN3: underground experimental hall, can receive the primary proton beam with high intensity in ECN3 • EHN1: surface experimental hall, can receive secondary beams and/or attenuated primary proton beams • EHN2: surface experimental hall, receives the secondary beams or intense muon beam Edda Gschwendtner North Area

  15. The target head Beam position monitors TBIU (upstream) , TBID (downstream) mounted on same girder as the target head for better alignment beam steering onto the target using BSM located ~30m upstream of the target Targets <x> = -0.2 mm <y> = -0.4 mm Edda Gschwendtner North Area

  16. Targets T6 target (M2, COMPASS) T4 target (H6, H8, P0) T2 target (H2, H4) Wobbling magnets Edda Gschwendtner North Area

  17. Target Station Wobbling - General AIM: • Increase flexibility in using a target station • Produce “several” secondary beams from the same target • when the primary beam hits the target basically “all” the particles are produced in a large variety of angles and energies • the most energetic particles are in the forward direction Don’t forget: • The very intense primary proton beam has to be dumped in a controlled way • The secondary beams of the chosen momentum have to go into the directions foreseen by the beam geometry (i.e. inside the vacuum tube of each beam line) SOLUTION: • “Wobbling” :hit the target under variable angle Edda Gschwendtner North Area

  18. Target Target Target Station Wobbling - General 0-order approximation: TAX B1 • single secondary or primary beam • fixed production angle SPS protons 1st -order approximation: TAX B1 • two secondary beams • one could be the primary beam • fixed production angles SPS protons B1 2nd -order approximation: TAX B1 • two secondary beams • one could be the primary beam • variable production angles Target SPS protons B1 Edda Gschwendtner North Area

  19. T4Wobbling Example P0 protons, H8 +180GeV, H6 +120GeV@0.54mrad) Edda Gschwendtner North Area

  20. … T4Wobbling Example P0 protons, H8, H6 secondary beam Edda Gschwendtner North Area

  21. Wobbling Survey/Changes Safety - Survey • Survey current in the “wobbling” magnets • Survey position of the TBIU, TBID monitors • automatically done • A program called WOBSU should be running continuously • Manual INHIBIT signal set in CCC for planned wobbling changes. Wobbling Changes: • Initiated by the EA physicist (upon the user requests) • Discussed in the EATC meeting, • documented in the minutes • Settings file • prepared and communicated by the EA physicist • Performed by the operators on the agreed time • re-tuning of the the beam lines after the wobbling changes is often required Edda Gschwendtner North Area

  22. Tertiary Beams - Introduction Secondary beams: • transport particles directly produced in the primary targets • energy and polarity depending on the wobbling setting Target “wobbling”: • advantages: • several beams per target are available • flexibility of production angle and secondary beam energy • drawback: • introduces coupling between beams: e.g. P0 + H8 + H6, H2 + H4 • changes are difficult to agree and schedule but the users (in particular the LHC detector calibration tests) demand a frequent change of beam energy and particle type solution: TERTIARY BEAMS Edda Gschwendtner North Area

  23. Tertiary Beams - Introduction • Allows more flexibility (independence) of the users in different beam lines • keep longer periods with the same wobbling setting • use mainly the filter mode optics • Produced in two distinct ways: • H2, H4, H6, H8: use a second target (filter) • H2, H4: from the conversion or decay of secondary neutral particles Edda Gschwendtner North Area

  24. Basic beam design momentum selection in the vertical plane two sets of bends Upstream BENDs between the primary target and the momentum acceptance collimator Downstream BENDs the main spectrometer of the beam momentum definition Secondary Beams - Reminder Edda Gschwendtner North Area

  25. introduce a target (filter) after the upstream bends beam line tuned for two energies E1 (high energy) : from the primary target until the filter momentum selection by the upstream vertical BENDs E2 (< E1) : from the filter until the experiment momentum selection by BEND-3 and BEND-4 (downstream vertical bends) tertiary beams have typically lower rates acceptance collimators can stay wide open choice of target material enhance/select different particles Tertiary Beams - H6, H8 XCONfine positioning filter/converter Edda Gschwendtner North Area

  26. Bend B3 of the wobbling as sweeping magnet charged particles are absorbed in the TAX neutral particles go through and hit the converter note: neutral particles can have zero or non zero production angle converter g on Pb (Converter=lead): to produce electrons (e+, e-) Converter=air (no converter) to let K0, L0 , to decay K0 p+ + p- L0  p + p- Bend B1:select charge and particle for the tertiary beam to the experiment Tertiary Beams - H2, H4 Edda Gschwendtner North Area

  27. Secondary beams Produced at the primary target rate goes down with energy increase Electron production: more with longer (Be-) targets e/pi ratio ~ proportional to target length With synchrotron radiation: separation from hadrons at high energies (120 GeV/c) mixed beams pion (hadron) contamination for lower energies user CEDAR or treshold Cherenkov counters for tagging Tertiary beams H6, H8: use Pb as secondary target few mm, or ~1-2 radiation lengths (X0) radiation length: distance in matter where electrons loose ~1/e of their energy hadrons loose ~nothing H2, H4: electrons from photon conversion high purity beams! Electron Beams Edda Gschwendtner North Area

  28. Secondary beams produced at the primary target positive sign beam a good fraction of the total hadron rate is protons Eliminate electron contamination using an absorber (~1-2 X0 of Pb) in the beam Tertiary beams H6, H8: use secondary target of Cu, (CH)n ~1 interaction length lI interaction length: characterizes the average longitudinal distribution of hadronic showers a high energy hadron has 1-1/e probability to interact within one lI lI >> X0 for most of materials H2, H4: hadrons produced in the decay of neutral mesons L0 p + p-, K0p++ p- Hadron Beams Edda Gschwendtner North Area

  29. Secondary beams Muons produced by the decay of pions muon momentum: 57-100% of the parent pion momentum For a pure muon beam for the experiment: close out of the beam axis the last collimators of the beam line Momentum selected muons: closing the collimator upstream of the last bend of the line rule of thumb: muons in a 1010cm2 trigger represent ~1% of the hadron/pion flux there is another ~1% in a cone about 1  1m2 around the beam axis 106 muons / 10  10 cm2 trigger  1.3 uSv/h Tertiary beams Muon energy range 57-100% of the secondary beam momentum Muon Beams Edda Gschwendtner North Area

  30. P42 + K12 Beam Edda Gschwendtner P42 + K12 Beam

  31. H6 H8 NA48 P42 beam (800 m) K12 beam T4 T10 P42 + K12 Beam for P326 (‘NA48’) in ECN3 Purpose of P326: studies of Direct CP violation in the K+ system Aim for 100 decays of type K+ p+nn Primary proton beam Intensity 1012 ppp Dangerous for equipment Hence P0-Survey ‘interlock’to close TAX1 when a magnetis out of tolerance Software still to be written. “K+”beam only (in 2007), 75 GeV/c Intensity 108 ppp Special interlock on T10 and TAX Cooling (chain 9) Beam monitored closely be experimentand EA physicists Edda Gschwendtner P42 + K12 Beam

  32. Edda Gschwendtner P42 + K12 Beam

  33. P42 + K12 Beam – Two Parts of the Run • A long run for a measurement of the (K+ e+n) / (K+ m+n) ratioSignature very similar to K+ p+nn for P326 experiment • 2. A R&D program for P326 detector developmentsAt the end of the period (about 4 weeks). This program has been approved last week.Some operational details still need to be clarified. Edda Gschwendtner P42 + K12 Beam

  34. COMPASS Edda Gschwendtner

  35. Trigger-hodoscopes μ Filter 160 GeVμ ECal & HCal SciFi SM2 RICH MWPC SM1 6LiD Target Gems Straws Silicon Drift chambers Micromegas Merge of two proposals: HMC – muon physics CHEOPS – hadron spectroscopy  study of hadron structure and hadron spectroscopy COMPASS (M2-Beam) Two stage spectrometer Polarized beam andtarget ~75% ≥50% SAT, LAT, PID ≈ 250 physicists from 28 institutes Edda Gschwendtner COMPASS

  36. Edda Gschwendtner COMPASS

  37. COMPASS Optics Considerations • Transport pions and muons from their decay together • Pions are matched into a long decay channel (> 5-10% of tp). • M2 decay channel: ~700m long • Pions have large momentum spread (10%). • Muons from their decay: lower momentum and larger momentum spread. • Muons not from a single point • Optics of decay channel: must transport both p and m. • A hadron absorber • To stop all hadrons and scatter muons as little as possible • Transport muon beam over a sufficient distance • muon momentum selection (±3%) after the hadron stopper: done by magnetic collimation. • The unwanted: separated from the beam axis and‘ranged out’ in the earth • the energy loss is about 0.5 GeV/m. • For 200 GeV muons thisrequires a length of  400 metres! • The origin of the muons isnot a point sourcebut a long ‘tube’ Edda Gschwendtner COMPASS

  38. Edda Gschwendtner COMPASS

  39. In/out motorisation Hadron Absorbers 9 Be modules (1.1 m each) in 3 bends Edda Gschwendtner COMPASS

  40. Hadron Beam Mode Special optics for hadron beam: 1) Special beam file 2) Short target head (40/100mm Be) 3) Small TAX holes 4) Single beam momentum all along the beam 5) Hadron absorbers OUT Hadron running still to be approved. More information later. Edda Gschwendtner COMPASS

  41. Electron Beam Mode • Beam produced as in the West Area, i.e.: • Secondary beam at  -100 GeV/c • 5 mm Pb ‘target’, (50m upstream of B4 + B5) • Tertiary beam of –40 GeV/c from Pb target to experiment.  Special optics with focus at the Pb target. Will only be used for one or a few days, set up by EA physicist Edda Gschwendtner COMPASS

  42. North Area Operational Aspects Edda Gschwendtner

  43. Organization of EA Operations • NORTH AREA • Setting up (commissioning) of secondary beam lines done by EA experts. They provide operational setting files. • SPS operators handle the technical problems of the secondary beam lines. • SPS operators change beam conditions according to schedule using operational setting files Edda Gschwendtner NA Operational Aspects

  44. Operational Aspects – Beam Tuning • Goal: deliver good quality of beam to the experiment! • sufficient rate, spot size, particle purity,… • Tuning the beam is required each time we change something: • energy, wobbling, user Very important: • start from an already prepared beam file by the EA physicists • be sure it corresponds to the present wobbling settings • be sure it can fulfill the user requirements • typically the users know “their” files, but good to check it yourself as well!!! Edda Gschwendtner NA Operational Aspects

  45. Operational Aspects – First Steps • consult the logbook of the beam line • most of the files have been used already in the past • new files represent minor variations of existing files • treat each plane independently • start with the vertical plane which is the most important to get the beam to the experimental hall • select your observation point • a scintillator counter close to the end of the beam line • provided the beam can reach it!! Edda Gschwendtner NA Operational Aspects

  46. To first order, all beam lines are quite similar however there are some differences which need time to become familiar with Time is important for you and the users there is always a limit to how good a beam can be; let the users decide Some users are quite experienced with their beam, and can do many things alone Good documentation is vital WIKI pages Beam line snapshot: status of magnets/files/wobbling settings status of collimators, target, absorber rates in few counters (start, middle, end of beam line) Ask for help if needed Operational Aspects - Remarks Edda Gschwendtner NA Operational Aspects

  47. Electrons do not like material! remove triggers or other detectors from the beam line, otherwise you may damage the whole beam line be careful when you try to measure/monitor things, you may disturb the users Follow the particles, consistent particle rates use as much as possible normalized rates: rate/pot monitor beam losses, be sure you are looking at the beam not at its halo Switching beam files: secondary beams have high rates  acceptance collimators close tertiary beams have low rates  acceptance collimators wide open therefore: switching from tertiary to secondary beam, load FIRST the collimators and then the magnets Operational Aspects – Precautions Edda Gschwendtner NA Operational Aspects

  48. CESAR - Equipment and Control • Access command & diagnostic • Files Management • Mode analyze • General Status • Scan • North Area Fix Display • North Area Interlocks • Login + Security Equipments • Magnets • Collimators • Scrapers • TAXs • TDXs, TDVs • Obstacles (Targets, Converters, Absorbers, …) • Pumpes (only reading) • Scalers • Scintillators • Analog Wire Chambers (status+profiles) • Delay Wire Chambers • FISCs (status + fast & slow profiles) • SEMs • Doors Edda Gschwendtner NA Operational Aspects

  49. Menus + Toolbars Navigation equipment oriented Work area one per beam Edda Gschwendtner NA Operational Aspects

  50. Menus and Toolbars Toolbars with shortcuts with the most useful actions Menus with same hierarchy as Nodal tree Edda Gschwendtner NA Operational Aspects

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