Radioactive ion beam facilities

1. 2012 Student Practice in JINR Fields of Research 9.oct.2012 Radioactive ion beam facilities How does they work ? I. Sivacek flerovlab.jinr.ru

2. How to prepare secondary beams ?

3. Efficiency and selectivity • ISOL systems has advantage in better selectivity • Fragment separators have more intensive secondary beams • Every process has it’s own efficiency ξ = ξDiff ・ ξIon ・ ξSep I2= σ Nt Φ ξ EFFICIENCY IS CRUCIAL Proper choice of equipment for each experiment is needed !

4. Secondary beams preparation • In-flight (10 - 1000 MeV/u, thin target) • Projectile fragmentation (scattering to small angles, few nucleons lost) • Heavy projectile on light target -> n-rich, mid A • Light projectile on heavy target -> n-def., low A • Fusion • Cold – 1n channel (GSI Darmstadt) • Hot – 3n, 4n with double-magic 48Ca (JINR Dubna) • Isotopes with τ ~ μs • Significant emittance

5. Secondary beams preparation • ISOL (any target, any projectile) • Fragmentation (protons, heavy ions) • Fission (neutrons, heavy ions) • Variety of mid-A isotopes (light and heavy fragment) • Spallation (protons) • n-deficient, close to β-stability line • Fusion (heavy ions) • n-def,.far from β-stability, ~ 5 MeV/u projectiles, selective • τ > ms • High selectivity, better emittance, up to 60 keV

6. Thermalization of reaction products • Thick hot target (ISOLDE) *converter – high Z (W, Ta) • Hot catcher (MASHA) • Fast release, high diffusion and effusion efficiency (low effusion materials Ti, V, Zr, Nb, Mo, Hf, Ta, W – ideal for construction materials – Ta heater at MASHA catcher) • Gas catcher(Gas cell for thermalization of reaction products) *IGISOL Target-catcher system is usually not selective &

7. MASHA hot catcher 4-sector diaphragm for beam diagnostic 2 μm Ti foil

8. Ion source Very fast method • IGISOL (ions are evacuated in 1+ or 2+ state) • Charge state: evacuation time, He purity, e - ion density in gas cell, chemical properties • Impact ionization (elements Wi > 7 eV) • Energetic electrons hit neutral atom in el. field • Thermoionization/surface ionizations • X+ (Wi< 7 eV); X- (EA> 1,5 eV) *catcher heater materials • Laser resonance ionization • Electron cyclotron resonance Not very selective Very selective (alkali metals, halogens) VERY selective Not very selective, great efficiency

9. Laser ionization • Isobaricaly and isomericaly pure secondary beams • Pulse laser – tunable wavelength • Competitive de-excitation • Non resonant high power laser ionization for highly charged ion beams

10. Electron cyclotron resonance • Plasma including all electrons and ions • Magnetic field keeps plasma volume • Resonance frequency 2πf = ω = e.B/m for electron mass m, elementary charge e and magnetic field strength B = 0,0875 T • 2,45 GHz microwave power – electrons gain energy in resonance • Impact ionization • C, N, O: ~ 50%; Xe: ~ 90% (only volatile elements)

11. ECR ion source scheme 40 kV acceleration Working gas (He) Reaction products 1+ reaction products, 1+ working gas

12. Mass separation • Fragment separators (in-flight) • Light fragments q = Z • Heavy fragments q ≤ Z -> degraders • Mass separators (ISOL) • Dipole magnet (magnets, or combination with TOF) • The higher angle – the better resolution

13. Ion optics • Dipole magnets • mass analysis • Quadrupole lenses • focusation • linear corrections of beam-shape • dispersion changes • linear or 3D ion traps (*mass analysis) • HF quadrupoles - beam cooling • Sextupoles • 2nd order (nonlinear) corrections of beam spot • wobbler

14. Detection systems • Position-sensitive spectrometric “stop detectors” • Time-of-flight systems • Faraday cups for beam diagnostic • Post acceleration • Linac • Tandem accelerators • Cyclotrones(also used as very precise mass separators)

15. Now is the right time for Questions !