Future HERA High Luminosity Performance 22.11.2018 Future HERA High Luminosity Performance H1 778 m 29 March 2001 HERMES Georg H. Hoffstaetter and Ferdinand Willeke (DESY, Hamburg) HERA-B HERA Protons Electrons 6336 m long 920 GeV protons 27.5 GeV electrons/positrons PETRA ZEUS

HERA: Improvements 1999/2000 Start luminosity Beam currents: and mA Efficiency % Average over month Georg.Hoffstaetter@DESY.de

Development of the Luminosity HERA Luminosity 1993-2000 Linear increase of the integrated Luminosity Integrated Luminosity (1/pb) The time for a luminosity upgrade of HERA has come Days after start of run Georg.Hoffstaetter@DESY.de

The Detector Region Georg.Hoffstaetter@DESY.de courtesy B.Holzer courtesy B.Holzer Georg.Hoffstaetter@DESY.de

Superconducting Magnet GO Georg.Hoffstaetter@DESY.de Georg.Hoffstaetter@DESY.de

Potential Problems Dynamic Aperture OK? Focusing: Dynamic Aperture OK? Polarization OK?, Luminosity OK? Can HERA be handled well? Too strong beam-beam force on p? Too strong beam-beam force on e? fRF increase: Georg.Hoffstaetter@DESY.de

Emittance and Lumi for 72° Optic The Luminosity was initially too small: Lumiscan Bunch has no product distribution: coupling Luminosity with 72° is large as expected Georg.Hoffstaetter@DESY.de

Dynamic Aperture for 72° Optic x´ V2(kV) Kick x The kick where half the current is lost leads to a satisfactory dynamic aperture. Georg.Hoffstaetter@DESY.de

Polarization for 72° Optic 60% Polarization Ie Polarization was in the spin matched 72° optic quickly brought to 63% (one day). Harmonic bumps were immediately effective Decoupling bumps worked well Georg.Hoffstaetter@DESY.de

Luminosity for fRF Increase 6 more measurements indicate For the center frequency , the luminosity is increased as expected Georg.Hoffstaetter@DESY.de

Too Strong Beam-Beam Force on p? 16mA 73mA Corresponding e-current after upgrade Ls is independent of e-current Tp depends on e-current Tails depend on e-current Georg.Hoffstaetter@DESY.de

Too Strong Beam-Beam Force on e? Ls So far no reduction of Ls by the bunch current Ippb No reduction of Ls by the second experiment No reduction of Ls by a larger b-funktionen Georg.Hoffstaetter@DESY.de

Where are the Beam-Beam Limits? Upgrade and Ip=140mA: emittance starts to grow Georg.Hoffstaetter@DESY.de

Lumi Reduction by Hourglass Effect Luminosity ( ) bunch length: 6cm p e 20cm 30cm Length 19cm: 12cm: Georg.Hoffstaetter@DESY.de

Tune Shift with Bunch Length Effect How will the tune shift parameters change and have these been analyzed by accelerator experiments ? Georg.Hoffstaetter@DESY.de

Resonances with Bunch Length Effect How will the resonance strength change and have these been analyzed by accelerator experiments ? All large resonance strength are due to the proton bunch length Georg.Hoffstaetter@DESY.de

Nominal and Ultimate Parameters The performance goal of HERA is not unrealistic and should not be too hard to achieve. A shortfall of beam intensity in the short term can be compensated. Georg.Hoffstaetter@DESY.de