Current Performance and Future Possibilities of HERA

[email protected]

7 July 2001

Georg Hoffstaetter (DESY, Hamburg)

Current Performanceand Future Possibilities of HERA

ZEUSHERAH1 (318 GeV)

HERA-B (42 GeV)

HERMES (7 GeV)

PETRA

[email protected]

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

[email protected]

[email protected]@desy.de

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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


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


Specific Luminosity and Polarization

%

55

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31-D

ec

25-J

an

19-F

eb

15-M

ar

9-A

pr

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ay

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ay

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un

18-J

ul

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ug

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ep

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ep

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ct

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ov

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ec

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ec

specific luminosity ( )2122910 mAscm


The HERA Lumi-Upgrade


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


Th e Detec to r R

e gion

courtesy B.Holzer courtesy B.Holzer


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


Superconducting Magnet GO


Superconducting Magnet GO


One Pipe - Three Beams


Synchrotron Radiation Absorber


Parameters


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:


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


Dynamic Aperture for 72° Optic

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

Kickx

x´ V2(kV)


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


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


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


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


• 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


)(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


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


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 /


Tune Shift with Bunch Length Effect

How will the tune shift parameters change and have these been analyzed by accelerator experiments ?

)(spx

)(spy


Bunch Length Dependent Resonances 6Qx+4Qy Resonance

pss /pss /

10Qy Resonance

JpyJpyJpxJpx

For maximum For maximum


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


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.


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


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


Increasing the Proton CurrentPETRA: N=60, 50 MHz 10 MHz & 5 MHz

10 MHz & 5 MHzN=30, 50 MHz


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

Current Performance and Future Possibilities of HERA

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