1. Future HERA High Luminosity Performance
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

2. HERA: Improvements 1999/2000 Start luminosity Beam currents: andmA
Efficiency %
Average over month

3. Development of the Luminosity
HERA Luminosity
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

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

5. Superconducting Magnet GO

6. 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:

7. 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

8. Dynamic Aperture for 72° Opticx´
V2(kV)
Kick x
The kick where half the current is lost leads to a satisfactory dynamic aperture.

9. 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

10. Luminosity for fRF Increase
6 more measurements indicate
For the center frequency , the luminosity is increased as expected

11. 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

12. 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

13. Where are the Beam-Beam Limits?
Upgrade and Ip=140mA: emittance starts to grow

14. Lumi Reduction by Hourglass Effect
Luminosity ( )
bunch length:
6cm p e
20cm
30cm
Length 19cm:
12cm:

15. Tune Shift with Bunch Length Effect
How will the tune shift parameters change and have these been analyzed by accelerator experiments ?

16. 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

17. 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.