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HERA Running 2005 F. Willeke, DESY 60 th Meeting of the DESY PRC November 10-11 2005

This document discusses the running of the HERA accelerator, including luminosity and polarization achievements, technical issues faced, and planned improvements for future runs.

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HERA Running 2005 F. Willeke, DESY 60 th Meeting of the DESY PRC November 10-11 2005

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  1. HERA Running 2005F. Willeke, DESY60th Meeting of the DESY PRCNovember 10-11 2005 Luminosity Polarization Backgrounds Improvements Technical Issues Further Planned Improvements Switching from electrons to positrons Low Energy Running Outlook

  2. Proton (1982) design intensity Electron (1982) Design Beam Current F. Willeke, HERA, 60th PRC

  3. Peak Luminosity goal peak luminosity F. Willeke, HERA, 60th PRC

  4. Specific Luminosity Alternative working point H1 ZEUS Design Level Larger than design: * smaller p emittance * strong dynamic beta reduction e  Well understood F. Willeke, HERA, 60th PRC

  5. Luminosity Production High peak luminosity and efficient operating  At the end of the run production rates of 1.5pb-1/d achieved Technical problems in the beginning and middle of the run lead to substantial luminosity loss 215 pb-1 F. Willeke, HERA, 60th PRC

  6. Electron Spin Polarization + - + - • Routine Running with polarized electron beams in collisions • Several times switching of Helicity • Polarization level (40-50) % (coll) (50-60)% non-colliding beam • Issues: • Strong Beam-Beam Effect • Non-understood asymmetry of polarization w.r.t. helicity F. Willeke, HERA, 60th PRC

  7. Beam-Beam Effect on Polarization Peak Polarization achieved after slow decay of specific luminosity Experiment: Beam-Beam Tunes spread of electrons is the problem Proposed cure:Mirror Tunes allow to run with the beam core at favorable (low) tunes Test in June:Confirmed, but beam core is too close to resonances, loss of luminosity  Decided to stay with nominal tune F. Willeke, HERA, 60th PRC

  8. Background Conditions: Poor HV conditions • Reasons for background conditions: • Large Global p Background in H1 after venting IR in shut down • BU-Magnet short, problems in March/April  coil replace in April • Electronics problem in large PS, spikes in June, July  found, fixed in July • Reasonable conditions in August-Nov, but careful tuning required F. Willeke, HERA, 60th PRC

  9. Operational Efficiency About 50% of the failure time lost due to a few incidents  measures taken Global failure statistics is encouraging F. Willeke, HERA, 60th PRC

  10. Improvements in 2005 • Poor electron injection efficiency resolved, reasons understood (saturation in beam line), further improved by better matching  70-80% efficiency • Enhanced temperature monitoring prevented further damage to beam pipe despite harder radiation • Improvements in diagnostics: e-BPM electronics, improved synchrotron radiation monitoring and imaging (e+p), further improvements in controls and data logging • Improved machine protection by fast magnet current change detection (helps to prevent uncontrolled beam loss) • Implementation of proton tune controller • Improved beam lifetime evaluation • Automation of timing and synchronization system  Positive impact on operational efficiency and operability of the accelerators F. Willeke, HERA, 60th PRC

  11. Technical Issues Coils of n.c. vertical bend in HERA p (BU) Damage by corrosion • Refurbishing Program: 6 coils already replaced in previous shut down 2 coils replace during the run • All the (remaining) 27 Coils will be replaced in Shutdown F. Willeke, HERA, 60th PRC

  12. Technical Issues Rotator Vacuum System Bellows produced 2 leaks in 2004 and 3 leaks in 2005 (insufficient fix in 2004 shut down) F. Willeke, HERA, 60th PRC

  13. Further planned Improvements(coming winter shut down): • Implementation of a longitudinal broad band damper system for protons to preserve the longitudinal emittance • Further reduction of beam cross sections at collisions due to using up margins and making use of dynamic beta  25% more Luminosity • Improvements in proton BPM (replacement of 12 critical BPMs in IR) • Improvements of klystron protection to prevent unnecessary transmitter trips • Increased pumping (x2) in one RF straight • Implementation of an operational permit system to prevent operator mistakes • Fast electron orbit stabilization at Ip’s (0-100Hz) to improve on proton beam diffusion and corresponding backgrounds F. Willeke, HERA, 60th PRC

  14. Switching from Electrons to Positrons Requirements of Experiments: The remainder of HERA Luminosity should be split equally in electron-proton and positron proton collisions • Need to switch from e+/e- or vice versa at least once during the run F. Willeke, HERA, 60th PRC

  15. November 2004: Switching from positrons to electrons F. Willeke, HERA, 60th PRC

  16. Switching leptons from 2004 Experience: • Needed 30 days in Nov 2004 from start switching to first luminosity subtract 5 days of hardware problem (GN repair Nov 2004) = 25 days • If turn-over is after shut down: Absorb 7 days of survey, magnet movement, shielding installation, wire system installation in shut down = 18 days A normal startup is about 1-2 weeks, subtract from turn-on time = ~(4-11) days needed additionally for switching • Switching from e- to e+ after shutdown takes 7 days extra turn on time • switching from e+ to e- during the run takes 25 days F. Willeke, HERA, 60th PRC

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  19. Sacrifice F. Willeke, HERA, 60th PRC

  20. HERA Running Until 2007 • Shut Down Nov 14 2005- Jan 26 2006 • Start up 2006 Jan 26- Febr 21 • Luminosity Running until switching leptons • 25 days switching leptons • Christmas break 2006/2007? • Run 2007 from Jan2-June 30 • ~450 Days of running F. Willeke, HERA, 60th PRC

  21. Conclusion • HERA made a big step in improving performance compared to 2004, more than 210 pb-1 of luminosity have been delivered, polarization is in competition with luminosity • A number of improvements increased the operational efficiency • Running with electron turned out to be slightly more difficult: somewhat larger background, occasional lifetime break down • However this was more than balanced by a large luminosity enhanced by dynamic b (+10%) • There have been a number of technical problems reducing operation time by about 40% • The technical problems and the background problems have either be solved during the run or are addressed in the HERA improvement program. • There is a rich HERA improvement program to overcome technical problems and to improve on performance and backgrounds • switching from e t e- or vice versa during the run is time consuming (25d) switching e t e- or vice versa after the shut down  more commissioning time (~7days) • Operating HERA with lower energy is most likely possible, parameters need to be worked out. The luminosity scales with g2. The loss in luminosity is estimated to be 90pb-1 F. Willeke, HERA, 60th PRC

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