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A LINEAR RFQ TRAP FOR COOLING AND BUNCHING OF RADIOACTIVE ION BEAMS

A LINEAR RFQ TRAP FOR COOLING AND BUNCHING OF RADIOACTIVE ION BEAMS. Ari Jokinen. University of Jyväskylä CERN / PS-division. Introduction RFQ Buffer gas cooling JYFL ion cooler and buncher. WHY BEAM COOLING ?. Emittance: characteristic property of an ion beam.

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A LINEAR RFQ TRAP FOR COOLING AND BUNCHING OF RADIOACTIVE ION BEAMS

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  1. A LINEAR RFQ TRAP FOR COOLING AND BUNCHING OF RADIOACTIVE ION BEAMS Ari Jokinen University of Jyväskylä CERN / PS-division Introduction RFQ Buffer gas cooling JYFL ion cooler and buncher

  2. WHY BEAM COOLING ? Emittance: characteristic property of an ion beam for a given number of ions, want minimum beam size, divergence and energy spread (hence, small emittance) Ion beam geometry Phase space diagram dx q dq x Liouville’s theorem: area of dx by dq is constant small divergence - large beam small beam spot - large divergence therefore to reduce emittance we need a dissipative environment: cooling

  3. COOLING TECHNIQUES Storage rings: • stochastic cooling • electron cooling • laser cooling Ion traps: • resistive cooling • evaporative cooling • laser cooling • buffer gas cooling (fast, universal -> optimal technique for RIB)

  4. BUFFER GAS COOLING Two initial energy regions: A. Elastic collisions, Eion >> Egas • collision rate • energy loss in single collision B. Viscous damping, Eion» Egas • Origin: long-range interaction between incoming ion and polarized buffer gas atoms -> viscous drag • Ions are damped to zero (in the model) • In reality: RF-heating, thermal movement, ...

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