Accelerators and ion storage ring TSR

Electron cooling

The phase space of stored ions can be compressed by aligning the ion beam with a cold dense electron beam over a length of about 1.2 m. The rms velocity spreads of the ions in all degrees of freedom is reduced by Coulomb interaction and this process is called electron cooling. In order to get a better understanding systematic investigations on this topic are being made at the TSR. The different degrees of freedom are being studied.

• Longitudinal electron cooling is investigated at the TSR by measuring the longitudinal cooling force within the range of its linear behaviour.
  
  Two different methods are used: The cooling force is measured by
  
  
  • the aid of an induction accelerator (IndAcc)
  • diffusive heating

• Transverse electron cooling is investigated by studying the time evolution of the transverse beam profiles under different conditions. The beam profile is recorded by the aid of the beam profile monitor (BPM).
  
  Transverse cooling time measurements are performed using
  
  
  • large initial beam diameter
  • small initial beam diameter

Systematic measurements were performed with D⁺, ⁶Li³⁺, ¹²C⁶⁺ and ¹⁶O⁸⁺ ions (6.1 MeV/u)

• for low electron-ion relative velocity in order to study the influence of the parameters
  
  
  • electron density
  • ion current
  • longitudinal magnetic field
  • transverse electron temperature (expansion of the electron beam)
  • charge state of the ions
    
    
• for high electron-ion relative velocity
  
  
  • longitudinal cooling force measurements with the aid of the induction accelerator were carried out, in order to study the dependence on electron density and ion charge
  • horizontal cooling time experiments with ion beams having large initial diameters were carried out, in order to study the influence of the parameter
    • initial beam profile, -width
    • electron density
    • charge state of the ions
    • velocity of the ions