Cooling Experiments at COSY in preparation for HESR · 2010. 11. 6. · August 31st, 2009 COOL 09 in Lanzhou 16 Prototype hardware tests at COSY Barrier Bucket tests in COSY One cavity

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Cooling Experiments at COSYin preparation for HESR

COOL 09, August 30th to September 4th, 2009

Dieter Prasuhn

August 31st, 2009 2COOL 09 in Lanzhou

Outline

Introduction to the COSY Facility

The HESR

Recent Cooling Experiments at COSY

Future Developments


The Accelerator Facility

COSY accelerates (polarized) protons and deuterons between 300/600 and 3700 MeV/c

4 internal and 3 external experimental areas

Electron cooling at low momentaStochastic cooling at high momenta


The Electron Cooler

Design Values

Electron energy up to 100 kV

Electron current up to 3 A


Stochastic CoolingHardware

2 Pickup-Tanks, 4m long, cooled to 20 K2 Kicker-Tanks, 2 m long

Frequency range: 1.0-1.8 GHz1.8-3.0 GHz

Adjustable delays for different ion velocities above β=0.85

Longitudinal Notch FilterCooling with the vertical system in „Sum-Mode“

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The HESR at FAIR


Artist’s view of

High Energy Storage RingHESR


Basic Data of HESR

Circumference 574 mMomentum (energy) range1.5 to 15 GeV/c (0.8-14.1 GeV)Injection of (anti-)protons from RESR at 3.8 GeV/cMaximum dipole field: 1.7 TDipole field at injection: 0.4 TDipole field ramp: 0.025 T/sAcceleration rate 0.2 (GeV/c)/s


Electron cooling

Electron energy range: 450 keV to 4.5 MeVElectron current up to 1 A

Allows cooling of anti-protons between1.5 GeV/c and 8.9 GeV/c

Beam Cooling in the HESR


Stochastic cooling(optimized for momenta above 3.8 GeV/c)

2 systems with 2-4 GHz and 4-6 GHzSeparate systems for radial, vertical and longitudinal phase spaceIndependent cooling per plane to adjust beam properties to the experimental requirements


Main common features of COSY and HESR

Electron coolingStochastic coolingInternal targets



Internal Target Experiments at COSY

ANKE:

• Dipol spectrometer• Polarized target• Cluster target• Solid state target

WASA:

• Solenoidal field• Pellet target


Internal Target Experiments at HESR

PANDA

• Solenoidal field• Forward dipol magnet• Pellet target• Cluster target


Studies at COSY for HESR

Prototype hardware tests

Beam – Target interaction- With stochastic cooling- With barrier bucket- Combination of barrier bucket and stochastic cooling

Electron cooling- Phase space density limits- Beam feed-back- Phase space manipulation


Prototype hardware tests at COSY

Barrier Bucket tests in COSY

One cavity one gapFilled with VitroPerm 500F Very compact design (length of cavity without gap: 28 cm). The length form flange to flange including the COSY gap: 50cm.

• Single sinus 5*f0 (2.5MHz) generated by 20 harmonics -> ~20% gap in antiproton beam

• Standing bucket• Voltage: 600V

1. Barrier bucket cavity


The principle of the Barrier Bucket

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Phasensonde mitBBAWG Signal

Barrier Bucket voltage

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beam-phase monitor with BBbeam-phase monitor with RF


2. Stochastic cooling electrodes


Inner part with coupling structures

Printed loop couplersSlot couplers


Longitudinal pickup (protons, 1.69 GeV/c, 5E10)

1958. Harmonics 1959. Harmonics


Slot coupler as transversal pickup:Beam centered / out of center

Betatron sidebands

only low beta-functions atinstallation point


Slot ring coupler as BPM

long. Spectrum vs BPM 5

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Position [mm]

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Noise level


Studies of Beam Target Interaction

• Only with stochastic cooling

• Only with RF or barrier bucket

• With the combination of stochastic cooling and RF





Advantage of the barrier bucket

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Electron Cooling Experiments at COSY• At low energies• Beam life time studies• Dynamic aperture calculations


PAX at COSYThe beam time for beam acceptance studies gaveus new insight into loss mechanisms within COSY

The electron beam size limits the dynamicacceptance of COSYThe beam lifetime (dynamic aperture) is stronglytune dependantInitial losses due to the electron cooling can bereduced by slowly increasing the electron current


Initial losses

Beam Intensity vs. Time

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H_0-rate vs time

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H_0-Rate (20 ms injection)

H_0-Rate (10 ms injection)

Initial losses disappear at smaller injected proton beam emittance

Explanation:Protons outside the electron beam see a non-linear focussing by the electron beam


Recent studies to overcome initial losses:

Electron cooled beam

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Beam life time in the presence of a cluster target (1014 cm-2)

beam lifetime vs. ecool current

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lifetime target on / s


Explanation for the life time results

• Without electron beam the measured beam life time is consistentwith the full geometrical acceptance of COSY and the targetrelated loss rates

• The electron beam is smaller than the proton beam. Now thebeam life time can only be explained with a reduced dynamicacceptance

• The dynamic acceptance corresponds to the acceptance of theelectron beam.

• The non linear space charge of the electron beam excitesresonances of higher order and reduces the dynamic acceptance.


Future Developments at COSY

• Investigations of Time-of-Flight stochastic coolingTalk on Tuesday morning

• Installation of the proposed 2 MeV electron coolerTalk by Juergen Dietrich on Friday morning

Documents

Cooling Experiments at COSY in preparation for HESR · 2010. 11. 6. · August 31st, 2009 COOL 09 in Lanzhou 16 Prototype hardware tests at COSY Barrier Bucket tests in COSY One cavity