Current Performance and Future Possibilities of HERA
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Transcript of Current Performance and Future Possibilities of HERA
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7 July 2001
Georg Hoffstaetter (DESY, Hamburg)
Current Performanceand Future Possibilities of HERA
ZEUSHERAH1 (318 GeV)
HERA-B (42 GeV)
HERMES (7 GeV)
PETRA
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HERA and its Pre-Accelerator Chain
H1
ZEUS
HERMES
HERA-B HERA
PETRA
778 m
6336 m long
DE
SY Polarized Electrons
Protons
Protons Electrons
20 keV Source Source 150 keV750 keV RFQ Linac II 450 MeV50 MeV Linac III Pia 450 MeV
8 GeV DESY III DESY II 7 GeV40 GeV PETRA PETRA 12 GeV
920 GeV HERA-p HERA-e 27.5 GeV
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HERA: Improvements 1999/2000
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andBeam current:e p
mA 1999 2000
Average peak luminosity ( )1999 2000
123010 scm
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HERA: Efficiency 1999/2000
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Development of the Luminosity
Inte
grat
ed L
umin
osity
(1/
pb)
HERA Luminosity 1993-2000
Linear increase of the integrated Luminosity
The time for a luminosity upgrade of HERA has come
Days after start of run
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Specific Luminosity and Polarization
%
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ec
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specific luminosity ( )2122910 mAscm
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Concept of HERA IRs
m
• Beam separation by super-conducting magnets in the detectors
• e-bending radius reduced from 1200 m to 400 m
• More radiation power: 28 kW, critical Energy = 150 kV
• Radiation passes the detector, absorbers at 11, 19, and 25 m
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4 super-conducting magnets ( BNL ) [6 MDM]
56 normal-conducting magnets
(Eframov Inst.) [6 MDM]
448 m UH Vacuum
system [6 MDM]
Absorbers, instrumentation,
controls, stands, … [6 MDM]
New Components
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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:
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The Luminosity was initially too small: Lumiscan
Emittance and Lumi for 72° Optic
)60( sL
)60( sL )72( sL
)72( sL
)(mmx )(mmx)(mmy )(mmy
Bunch has no product distribution: )()( yx coupling
)72( sL
)72( sL
x
y
Luminosity with 72° is large as expected
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Dynamic Aperture for 72° Optic
The kick where half the current is lost leads to a satisfactory dynamic aperture.
Kickx
x´ V2(kV)
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Polarization was in the spin matched 72° optic quickly brought to 63% (one day).
Harmonic bumps were immediately effective Decoupling bumps worked well
60%
PolarizationIe
Polarization for 72° Optic
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6 more measurements indicate For the center frequency , the
luminosity is increased as expected
Luminosity for fRF IncreaseLL
RFf RFf
HzfZentrum 175
HzfZentrum 175
HzfZentrum 175HzfZentrum 0
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Ls is independent of e-current Tp depends on e-current Tails depend on
e-current
Too Strong Beam-Beam Force on p?16mA 73mACorresponding e-current after upgrade
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Too Strong Beam-Beam Force on e?
No reduction of Ls by the second experiment
No reduction of Ls by a larger -funktionen
Ls
Ippb
So far no reduction of Ls by the
bunch current
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• beam-beam tune shift for e and p
• hourglass effect for protons
• background due to synchrotron radiation and scattered e
• dynamic aperture of electrons
Limits for the Lumi Upgrade
m
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)(mey
measureds,L
Where are the Beam-Beam Limits?
Upgrade and Ip=140mA: emittance starts to grow
)(mey
yQ2
xQ2
)(mey
emeasuredx,
emeasuredy ,
)(mey
)( ,ecalcys L
measureds,L
)( ,emeasuredys L
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Lumi Reduction by Hourglass Effect
)(cmpy
ep
75.1)5.12(
0L
L cmpyLength 19cm:
12cm: 9.1)5.12(
0L
L cmpy
Luminosity ( )3210
20cm
bunch length: 6cm
30cm
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Tuneshift Change by Hourglass Effect
m
mm
mm
mpx 45.2
mpy 18.0
mex 63.0
mey 26.0
Protons Electrons
Horizontal: grows slowerpx Vertical: grows fasterpy
py
py s
)(px
px s
)(
pss / pss /
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Tune Shift with Bunch Length Effect
How will the tune shift parameters change and have these been analyzed by accelerator experiments ?
)(spx
)(spy
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Bunch Length Dependent Resonances 6Qx+4Qy Resonance
pss /pss /
10Qy Resonance
JpyJpyJpxJpx
For maximum For maximum
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Resonances with Bunch Length EffectHow will the resonance strength change and have these been analyzed by accelerator experiments ?
All large resonance strength are due to the proton bunch length
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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.
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Spin-Orbit Tracking with Quaternions
Computation of the invariant spin field by
analyzing tracking data:
Fourier analysis Stroboscopic averaging Antidamping
Computations performed in SPRINT, Hoffstaetter and Vogt, DESY/00
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High Order Resonance Strength
Tracked depolarization as expected
Resonances up to 19th order can be observed
Resonance strength can be determined from tune jump.
Spin tune )(lim znP
Computations performed in SPRINT, Hoffstaetter and Vogt, DESY/00
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Increasing the Proton CurrentPETRA: N=60, 50 MHz 10 MHz & 5 MHz
10 MHz & 5 MHzN=30, 50 MHz
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TESLA with Röntgen FEL
Damping RingTunnel
Super-conducting Positron Linac
Wiggler for thePositron Source
Detector and Experimental Area
Cryogenic Halls
Super-conducting Electron Linac
Röntgen FEL