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FASCI RADIOATTIVI (Esotici)

FASCI RADIOATTIVI (Esotici). Particelle o ioni instabili prodotti artificialmente( ovvero non esistenti in natura) con caratteristiche energetiche e spaziali tali da poter essere riutilizzati come un “normale” fascio ottenuto da un acceleratore. L (10 -10 sec) X ( 10 -10 sec)

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FASCI RADIOATTIVI (Esotici)

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  1. FASCI RADIOATTIVI (Esotici) Particelle o ioni instabili prodotti artificialmente( ovvero non esistenti in natura) con caratteristiche energetiche e spaziali tali da poter essere riutilizzati come un “normale” fascio ottenuto da un acceleratore. • L (10-10sec) • X (10-10sec) • Li11 (neutron rich) • Sn107 (proton-rich) G.Raciti –Dip. Fisica& Astronomia –Univ. Catania & INFN – Otranto 2005

  2. What is an exotic nucleus? Exotic Nucleus: Normal Nucleus: 16 neutrons 6 protons (carbon) 22C Radioactive, at the limit of nuclear binding 6 neutrons 6 protons (carbon) 12C Stable, found in nature • Characteristics of exotic nuclei: • Excess of neutrons or protons, • short half-life, • neutron or proton dominated surface, • low binding

  3. Un po’ di Storia… 284 isotopes with T1/2 > 109 year Our beams till 1989 !

  4. Un po’ di Storia… <1940 495

  5. Un po’ di Storia… Reactors: n on U <1940 1940 495 822

  6. Un po’ di Storia… First Isotope Separator experiment Niels Bohr Institute 1951 fast n on U: Kr and Rb isotopes <1940 1940 1950 495 822 1244

  7. Un po’ di Storia… Selective detection method:  decay <1940 1940 1950 1960 495 822 1244 1515

  8. Un po’ di Storia… Light-ion induced spallation Heavy-ion induced fusion <1940 1940 1950 1960 1970 495 822 1244 1515 2010

  9. Un po’ di Storia… Projectile and target fragmentation <1940 1940 1950 1960 1970 1980 495 822 1244 1515 2010 2270

  10. Oggi • Stable + decay • - decay  decay p decay spontaneous fission Around 3000 of the expected 6000 nuclei have been observed

  11. I(eA) NAc[gr/cm2 ] s [cm2 ] Nprod = Zproj e [coul] Atarg [gr] I(enA) 10-9 1019 6.02 1023c[mgr/cm2 ] 10-6 s [mbarn ] 10 -27 Nprod = Zproj 1.602 Atarg 3.76 I(enA) c[mgr/cm2 ]s [mbarn ] Nprod = Zproj Atarg Produzione Nprod = N inc N targ s [ions/sec] [ions/sec] [nucl/cm2 ] [cm2 ] c[mgr/cm2 ] = r [gr/ cm3 ] t[mm] 102

  12. Qualche calcolo….. I= 10enA -> 0.6 1011 protons/sec Potenza (W)= I V = I (Energy/Charge state) Es: I=1mA E=50 A MeV di O16 completamente strippato (O8+) : P = 1 10-3 (50 16/8) 106 =100 kW

  13. Un Esempio…...Produzione ProductionTarget

  14. ProductionTarget ProductionTarget 1 hour 1 min s=1mbarn s=0.5 barn s=1barn …..Reazione

  15. Intensità Minime di RIBs

  16. s( l ) l (angular momentum Reazioni di Produzione • Bassa Energia (Fusione, Fissione, Reazioni dirette , Deep Inelastic) • Alta Energia (Frammentazione Proiettile o Targhetta, Spallation, Fissione in volo) - peripheral elastic and quasi-elastic ( QE ) collisions - semi-peripheral deep-inelastic collisions ( DIT ) collisions - incomplete ( ICF ) and complete ( CF ) fusion in central collisions - pre-equilibrium emision typically preceding ICF/CF and DIT

  17. Reazioni di Produzione Transfer Reactions • In generale: • Piccate ad angoli in avanti • s @ 10-1 – 10 mbarn

  18. 292 MeV 54Fe + 92Mo 146Er(p4n)141Ho 402 MeV 78Kr + 58Ni 136Gd(p4n)131Eu A.A. Sonzogni et al., Phys. Rev. Lett. 83 1116 (1999) D. Seweryniak et al., Phys. Rev. Lett. 86 1458 (2001) Reazioni di Produzione Fusione

  19. Reazioni di Produzione Frammentazione del Proiettile Participant-spectator reactions at relativistic energies ( above 100 AMeV )

  20. Reazioni di Produzione (Frammentazione)

  21. Random removal of protonsand neutrons from heavy target nuclei by energetic light projectiles (pre-equilibrium and equilibrium emissions). Spallation Reazioni di Produzione Frammentazione della Targhetta

  22. Reazioni di Produzione

  23. Reazioni di Produzione (Frammentazione Fissione)

  24. Reazioni di Produzione (Frammentazione Fissione)

  25. K.H. Schmidt et al., Model predictions of the fission-product yields for 238U (2001) Reazioni di Produzione Fissione

  26. Optimum delle Reazioni di Produzione

  27. In Flight ISOL Selezionatore e.m. Target di Produzione Utente Acceleratore Primario (Driver) Target di Produzione Acceleratore Selezionatore e.m. Acceleratore Primario (Driver) Utente Metodi di Produzione • In-Flight (Fascio prodotto direttamente nella reazione) • Degraders • Tagging • ISOL (Prodotti di reazione accelerati in un secondo acceleratore) Reazioni su targhette “spesse”

  28. RIBs Facilities nel mondo

  29. CRC, Louvain-la-Neuve, Belgium delivering ISOL beams since 1989 GSI, Darmstadt, Germany delivering IF beams since 1990 SPIRAL, Caen, France delivering IF beams since 1984 delivering ISOL beams since 2001 MAFF, Munich, Germany under construction REX-ISOLDE, Geneva, Switzerland delivering ISOL beams since 2001 SPES, Legnaro, Italy project LNS-Catania-Italy EXCYT: ISOL Under commissioning FRIBS: IF since 2001 RIBs Facilities in Europa

  30. Production Yield I = s  F N e1 e2 e3 e4 e5 I = Intensità particelle prodotte s: cross-section, F: primary-beam intensity, N: target thickness, 1: product release and transfer efficiency, 2: ion-source efficiency, 3: efficiency due to radioactive decay losses, 4: efficiency of the spectrometer, 5: post-accelerator efficiency. F N = Luminosity

  31. In Flight (IF) Isotope Separator On Line (ISOL) • light and heavy ions, n, e • -spallation • -fission • fusion • fragmentation • heavy ions • fusion • fragmentation driver accelerator or reactor high-temperature thick target thin target gas cell ~ ms ion source storage ring fragment separator post accelerator mass separator meV to 100 MeV/u ms to several s good beam quality 30 A MeV-GeV eventually slowed down ms • experiment • detectors • spectrometers • ... Confronto fra i due Metodi

  32. Metodo ISOL Isotopes Separation On Line • Driver ad alta intensità (Dissipazione Calore) • Targhette di produzione (Raffreddamento e Radioattività) • Efficienza Selezione(20%) • Efficienza di estrazione (30%) • Efficienza di Trasmissione alla Sorgente(30%) Potenza (W)= I V = I (Energy/Charge state) Es: I=1mA E=50 A MeV di O16 completamente strippato (O8+) : P = 1 10-3 (50 16/8) 106 =100 kW Beam

  33. Metodo ISOL Ottima qualità dei Fasci

  34. Figure di Merito Intensity Isecondary = sproductionNtarget Ibeam x erelease – transport x eionization x etransport - storage - post-acceleration Intensity Sensitivity Icounts(reaction) = Isecondary hbranchingsreaction xNsecondary target x espectrometer x edetector Icounts(decay) = Isecondary hbranchingx edetector Event rate Selectivity Isecondary/Itotal Purity Rresolving power (suppression of background, identification of events) Peak to background

  35. ISOL Running Facilities

  36. GANIL

  37. GANIL-SPIRAL(ISOL)

  38. SPIRAL II

  39. Louvain la Neuve (Belgio)

  40. Louvain la Neuve

  41. ISOLDE -CERN

  42. Metodo In-Flight • Separazione ElettroMagnetica (Coktail di RIBS) • Uso di “Degrader” • Accettanza in angolo solido del FRS • RIBs non “monoenergetici” • Energia ? Energia incidente NON REGOLABILE • Rese di Produzione più alte • Intensità di corrente 103 piu’ basse • Relativi problemi di radioattività • RIBs con vite medie piccole (<msec)

  43. Final Focus Dipole 2 Intermediate Focus Q4 Q5 Q6 Q7 Q8 Q9 Degrader Q1 Q2 Q3 Dipole 1 Production Target Overview of the Fragment Separation Technique

  44. In Flight Laboratory Accelerators RIB Separator RIB Energies GANIL NSCL-MSU GSI RIKEN DUBNA LANZHOU LNS C Cycl. C Cycl.s SIS Cycl. C Cycl.s Cycl. Cycl. SISSI+LISE A1200 FRS or ESR RIPS ACCULINNA&COMBAS RIBLL FRS-CT <95 A MeV <200 A MeV <1.2 A GeV <150 A MeV <100 A MeV <80 A MeV <50 A MeV RIBs IF-Running Facilities Fragment Separators

  45. Magnetic rigidity • The force qvB on a charged particle moving with velocity v in a dipole field of strength B is equal to it’s mass multiplied by it’s acceleration towards the centre of it’s circular path. Curvature radius which can be written as: • Bis calledmagnetic rigidity If we put in all the correct units we get: B = 33.356·p [KG·m] or: B = 3.3356·p [T·m] (if p is in [GeV/c])

  46. DIPOLE SELECTION Reference momentum Magnetic Dipole (I) Reference trajectory • A dipole is the ion-optical equivalent of a prism • A dipole introduce dispersion, i.e. a relation between momentum and position • A/q selection with a certain acceptance in momentun width

  47. ALADIN: to evaluate the velocity of a fixed charged particle (momentum reconstraction): once B is know by the measurement of the trajectory of the ion, the evaluation of the velocity can be done if the A/Z of the charged particle is already known. • Large acceptance in angle and momentum • FRSdipole: Magnetic selection in mass, charge state and speed. • Limited acceptance in angle and momentum • Only particles with a limited range of bending radii, centered around 0, can pass. The binding radius 0 is defined by the geometry of the magnet. Magnetic dipole (II) Here we consider two different types of dipoles, represented by two examples: • ALADIN:: ALarge AcceptanceDIpole magNet • dipole magnet of the FRS (Fragment Recoil Separator)

  48. Magnetic field Hyperbolic contour x · y = constant • The field gradient, K is defined as: Quadrupole (I) • A Quadrupole has 4 poles, 2 north and 2 south • They are symmetrically arranged around the centre of the magnet • There is no magnetic field along the central axis • On the x-axis (horizontal) the field is vertical and given by: By x • On the y-axis (vertical) the field is horizontal and given by: Bx y

  49. Quadrupole (II) Force on particles • It focuses the beam horizontally and defocuses the beam vertically. • Rotating this magnet by 90º will give a vertical focusing and an horizontal defocusing • A pair of quadrupoles with a drift section in between is the ion-optical equivalent of a lens.

  50. ENERGY STRAGGLING • ANGULAR STRAGGLING • NUCLEAR REACTIONS INTENSITY LOSS Degrader • Located in an intermediate focal plane on the beam line • Better separation of isotopes with the same A/q ratio • Reduction of “contaminants” • The relative energy loss in the degrader is given by: • With K: constant typical of the degrader A: nucleus mass • e: thickness of the degrader Z: atomic number • Thickness and material is chosen as a compromise between desired and undesired effects.

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