HERA Luminosity ZEUS Weekly Collaboration Meeting January 22, 2007 F. Willeke, DESY MHE

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HERA Luminosity ZEUS Weekly Collaboration Meeting January 22, 2007 F. Willeke, DESY MHE. PART I HERA Overview HERA Luminosity Production 2004-2006 Low Energy Proton Running PART II Accelerator Physics of Luminosity Tuning, selected topic. Electron-Hadron Collider HERA. - PowerPoint PPT Presentation

Text of HERA Luminosity ZEUS Weekly Collaboration Meeting January 22, 2007 F. Willeke, DESY MHE

  • HERA LuminosityZEUS Weekly Collaboration MeetingJanuary 22, 2007

    F. Willeke, DESY MHE PART I HERA Overview HERA Luminosity Production 2004-2006 Low Energy Proton Running

    PART IIAccelerator Physics of Luminosity Tuning, selected topic

  • Electron-Hadron Collider HERADouble Storagering with 6.3km Circumference920GeV Protons - 27.5GeV Leptons

  • HERA Double Ring Collider 820 GeV Protons (actual 920 GeV) 30 GeV Leptons e+ or e- (actual 27.5 GeV) Spatial resolution 10-18m

    Bjrn Wiik (1937-1999)Ultimate experimental demonstration of QCD required a Lepton-Proton Collider with 320 GeV center of mass Energy

  • HERA Milestones1981 Proposal1984 Start Construction1991 Commissioning, first Collisions Start Operations for H1 and ZEUS, 1st Exciting Results with low Luminosity1994 Install East spin Rotators longitudinal polarized leptons for HERMES1996 Install 4th Interaction region for HERA-B1998 Install NEG pumps against dust problem, Reliability Upgrade2000 High efficient Luminosity production rate:100pb-1y-1 180pb-1 e+p Precision Measurement on proton structure 2001 Install HERA Luminosity Upgrade, Spin Rotators for H1 and ZEUS2001/2 Recommissioning, HERA-B physics Run 1st longitudinal polarization in high energy ep collisions Start-up of the HERA II Run2007 HERA operation ends

  • HERA Footprint240 mcircumference

  • Injectors ProtonsMagnetron H- SourceRFQ to 180keVAlvarez Linac to 50MeVCharge conversion injection DESY III p to 7.5GeV/cPETRAII to 40GeV/c

    Leptonsthermionic guns-band LINAC ~300MeVe+ converters-band LINAC 450MeVe+ accumulator 450MeVDESYII 12.5Hz Synchrotron 7GeVPETRA II 12GeV

  • 10 mdetectorIPNEW IR schematicallyTop View

  • Basic Concept: low b Quadrupole Magnets closer to the Interaction Point, using novel magnet technology

    IR TOP VIEWHalf Quadrupoles for p-focusing Superconducting Separator/Quads

  • Improved Absorber 4 NR11m: Status: eingebaut

  • HERA II Beam CurrentsP-limitationsLosses in transferingFrom PETRA(PR-Weg)

    Lepton LimitationsRF Breakdowns

  • HERA Luminosity Production 2004-20072004200520062007

  • Specific Luminosity 2004-2007QyQxOperation with MirrorTunes

  • Modeling of HERA Specific LuminosityEffects investigated to explain/cure difference: Beam optics e: ok Beam optics p: ok Chromatic beta beat p After switching to mirror tunes: 5%, corrected Assuming incorrect phase advanceModels well the difference, but can not be verified experimentally larger satellite resonances, uncorrectable, -3%

  • Low Proton Energy Running

  • Adiabatic damping and aperture limitations



  • Proton beam-beam Tuneshift

  • Electron Beam Size Matching

  • Electron Beam-Beam Tune shift

  • Lumi-scaling with Energy

  • Design of low energy collision scheme Reduce GM magnets in strength and leave all p-magnets in the nominal proton- positron/electron positions Positron Lattice unchanged, positron IR quads unchanged Positron optics in the arc: assume 60 degree positron/proton IP (-7.5mm radially) Optical Parameters:

    bxp=4.9mbxe = 1.20mbyp=0.36mbye = 0.52meNp=16 mm exe = 40nmeye = 6 nm

  • Ip=100mAIe=40mA

  • IR Top ViewP-Magnets: Nominal positron/electron positionsE-Magnets: Nominal positron positions

  • IR Top View Close-up

  • All p-magnets are now at nominal positionsP-magnets axisGM GM GN GN GN GA GB GB GB9 QR QR QR QR~4mmP-TrajectoryIP

  • P-Optics


  • VersatileToolbox for Accelerator Optimisation BUMPSClosed Orbit bump tool box:

    adjusting transverse position and angle in the IP adjusting the g beams on the photon monitor optimized spurious dispersion waves and width of synchro-betatron amplitudes injection bumps for adjusting position and angle at the injection septum Polarimeter bumps:adjusting the position and angle of the beam at calorimeters H1 VFPS Bumps: make room in the beam pipe for off momentum protons by moving the circulating beam off centerVertical dispersion bumps for adjusting the vertical beam emittance to match the two beam sizes at the IRDecoupling bumps: small vertical beam offset of the arcs to produce Weak skew quadrupoles in the arc by feed-down of sextupole fieldsHarmonic bumps to compensate the detrimental content of the distribution small dipole perturbations around the machine in order to achieve high spin polarizationPhase bumps: global compensation of higher order Chromaticity and dynamic betaTilt bumps:adjusting the x-y beam ellipse tilt at the IPBackground bumps: adjust beams in the centre of quadrupoles to avoid additional synchrotron radiationChromaticity bumps: adjust the sextupoles to compensate the chromaticity

  • Closed Orbit

  • Closed Orbit Bump3 short dipoles (kicks) are necessary in general to make a local orbit distortion

    A superposition of two 3-bumps allows to control the besides the amplitude also the slope a some positionSuch bumps are called Symmetric 4 Bump x=0Antisymmetric 4 bump x=0, x0(if centred around a symmetric lattice point)

  • Luminosity Tuning and Luminosity Scans

  • Angle Bumps in the IPAssume that the proton beam is cut in slices of length ds which collide with the e-beam with an offset of D=qs (short bunches assumed) ss=20cm, sxp,e=110mm, qx
  • IP Beam Angels and Luminosity Difference Electrons/Positrons IP16mm24 mme+e-P(e-)P(e+)LumimonitorR(positrons)= 95%R(Electrons)=98%Luminosity difference is 3%Not quite negligible

  • H4A-Bumps and Synchro-betatron Oscillations Transverse ad longitudinal motion are intrinsically strongly coupled. This coupling my drive synchro-betatron resonances

    Resonances: small distortions, which are in phase with the oscillation amplitudes and have large impact: amplitude growth (beam loss) oscillation energy exchange between different planes

    Longitudinal oscillation energy: dEs=E10-3Transverse energy: dEt= Ex=E 10-4 Resonant coupling between transverse and longitudinal directioncan cause large growth of transverse emittance

  • Operation with the new LatticeLuminosity Optics3Qx4QxQx- QyInjection Tune:Dynamic Aperture Sufficient High specific Luminosity But in Collisions Tune footprint limited by strong resonances Poor PolarizationCollision Tunes:good polarization (50% in collisions with 3 rotators)Dynamic Aperture small (6-7)s frequent sudden lifetime breakdown non-reproducible orbit effects reduced specific luminosity (15%) Frequent beam loss when switching tunes, Squeeze with C.T. very difficultQx + 2QyQx0.500.5Qy0DQxbb =0.036 DQybb=0.072Qx -2 Qy4QyQx + 2Qs3Qy2Qx + 2QyBETATRON TUNE DIAGRAM

  • Results of Particle Tracking with Synchrotron and Betatron Oscillations

    (6D)1000 turns @21ms, (transverse Radiation Damping time tx=12ms)2 Sextupole Families, 20 sextupoles per family/octant Result: Dynamic Aperture severely reduced near single resonancesThe strongest resonances are the Qx-2Qy resonance driven by sextupole fields and the 2nd synchro-betatron resonanceQx+2QsTracking Calculations using the code Six-track performed by W. Decking Study of ResonancesSurvival plot

  • Coupled 6-D motion with cavities and sextupolesStrong linear coupling between horizontal and longitudinal motionchromaticsNonlinearitiesTransverse motionNonlinearities longitudinal motion Linear opticsLongitudinal focussingApproximations:v = cp2x/r neglectedSquare root expanded1/(1+e) expanded into 1-eCanonical coordinates x,p, s,e

  • Decoupled Motion (Ripken, Barber, Mais, Wke,90)Transverse linear optics

    Longitudinal linear opticsLinear coupl. by dispersion in cavities


    2nd satellite driving terms

    Nonlinearities trans.

    Nonlinearities longitudinal.

  • Example: Qx+2Qs resonance driving term driven by dispersion in sextupolesResonances are driven by certain harmonics of the non-linear Forces (called driving terms) which oscillate close to the betatron/synchrotron frequencyNear a resonance, there is rapid exchange of energy between the oscillation in different planes and in some cases unlimited growths of oscillation amplitudes

  • H4A Bumps & DispersionIPDispersion kicks from off centre passage through IR quads add: large dispersion waveDispersion Waves:Large contributions to Satellite Driving Term

  • Built-up of satellite driving terms around HERA for various optics solutionsBefore UpgradeAfter UpgradeAfter Upgrade Improved chromaticsAfter Upgrade Improved D.A.

  • Re-evaluating synchro-betatron resonances without closed orbit distortionsZero closed orbit Undistorted Dispersion FunctionBuilt-up of Satellite resonance driving termsDf12=295.8Hz

  • Re-evaluating synchro-betatron resonances with an asymmetric Bump around IP North5mm asymmetric hor. bump at IP North Dispersion with 10cm beatDf12=590 Hz

  • Long Bumps In HERA with its long periodic structures in the arc, distortions can potentially accumulate which leads to strong performance reduction large accelerators need a distributed corrector system

    On the other hand, this sensitivity to small distortions