Future HERA High Luminosity Performance

1
Future HERA High Luminosity Performance
H1
778 m
29 March 2001
HERMES

• Georg H. Hoffstaetter and Ferdinand Willeke
• (DESY, Hamburg)

HERA
HERA-B
Protons Electrons
6336 m long 920 GeV protons 27.5 GeV
electrons/positrons
PETRA
ZEUS
2
HERA Improvements 1999/2000
Start luminosity
and
Beam currents
mA
Efficiency

Average over month
3
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
4
The Detector Region
Georg.Hoffstaetter_at_DESY.de
courtesy B.Holzer
courtesy B.Holzer
5
Superconducting Magnet GO
Georg.Hoffstaetter_at_DESY.de
6
Potential Problems

• Dynamic Aperture OK?
• Polarization OK?, Luminosity OK?
• Can HERA be handled well?
• Polarization OK?, Luminosity OK?
• Too strong beam-beam force on p?
• Too strong beam-beam force on e?

Focusing
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 Optic
x
V2(kV)
x

• The kick where half the current is lost leads to
  a satisfactory dynamic aperture.

9
Polarization for 72 Optic

• 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 Ip140mA emittance starts to grow
14
Lumi Reduction by Hourglass Effect
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.