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REX-ISOLDE: Advancements in Proton Beam Conditions and Radioactive Ion Beam Release

This project focuses on the implementation of laser resonance ion source and a new concept for post-acceleration ISOLDE radioactive ion beams using a pulsed proton beam. It overcomes initial challenges and achieves better yields than expected. Other developments include adapting to new experimental conditions, the suppression of contamination, and the use of laser resonance ionization.

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REX-ISOLDE: Advancements in Proton Beam Conditions and Radioactive Ion Beam Release

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  1. 1993-1995: the Pre REX-ISOLDE Era Piet Van Duppen KU Leuven Department of Physics and Astronomy Instituut voor Kern- en Stralingsfysica Leuven, Belgium • Start up at PS-Booster - adapt to the new proton-beam conditions • Implementation of the laser resonance ion source - new opportunities • A new concept for post-acceleration ISOLDE radioactive ion beams - REX-ISOLDE

  2. 1 GeV, pulsed proton beam of the PS-Booster • Pulsed release of the radioactive isotopes - pulsed RIB (compared to DC at SC) From the ISC meeting of August 1993: H.L. Ravn presented two encouraging results: …the initial problems with shock waves in molten metal targetshave been overcome, and second that the combined effect of shorter delay times, higher cross sections at 1 GeV proton beam energy…have resulted in radioactive beam yields better than expected by a factor two or more. Chimney and Helix Target container Start up at PS-Booster

  3. 1 GeV, pulsed proton beam of the PS-Booster • Pulsed release of the radioactive isotopes - pulsed RIB (compared to DC at SC) Release of 8Li(T1/2=840 ms) from a tantalum target tdiffusion = 1 s teffusion 100 ms PS Booster proton pulse - Measurements of the release profile: essential for further target ion source development J. Lettry,- NIMB 126 (1997) 130 Start up at PS-Booster

  4. First experiment at PS Booster Phys. Lett. B317 (1993) 25 17Ne (T1/2=109 ms) 0-1 s 1-4 s 495 keV Counts • ..(the decay to the 1/2+ bound state) ….is a factor two faster than the corresponding mirror . • Shell-model calculations can only reproduce the asymmetry if the halo structure of the 17F state is taken into account • Halos have thereby been shown to affect beta decay rates directly. E (keV) Start up at PS-Booster

  5. Adapting to new experimental conditions - Collaps (A. Keim et al., Nucl. Phys. A 607 (1996) 1) "The ultra-sensitive detection combines optical pumping, state-selective collisional ionization and counting of beta-radioactivity." sd-shell model calculations "..the beam of mass m=32 a.m.u, contained less than 103 short-lived 32Ar (T1/2=98 ms) ions per second on a background exceeding 108 ions per second…" Start up at PS-Booster

  6. Adapting to new experimental conditions - ISOLTRAP (G. Bollen,- Phys. Scripta 59 (1995) 165) "New developments aim for an extension of the applicability of the spectrometer to isotopes of other elements." elements that can be surface ionized Start up at PS-Booster

  7. Pulsed release of the radioactive isotopes - pulsed RIB - Suppression of contamination Z=82 210Tl: Hahn en Meitner (1909) De Witte,- PRC69, 044305 (2004) N=126 700 ns 89 Fr A=216 45 ms 1.2 Rn 300 ms 0.05 At T1/2 s (mbarn): Th 150 ms 0.003 Po 2.17 m 6 10-5 Bi PVD et al., NIMB 134 (1998) 267 Start up at PS-Booster

  8. NIMB 73 (1993) 550 Ag I Mn I Sn, Tm, Yb and Li F. Scheerer,- Inst. Phys. Conf. Ser. 114 (1990) 129 Laser Resonance Ionization

  9. courtesy V. Fedoseyev Laser Resonance Ionization

  10. T. Kautzsch,- PRC54 (1996) R2811 K.L. Kratz,- Astrophys. J. 403 (1993)216 Laser Resonance Ionization

  11. 57Co 272 d 57Fe 57Fe Mossbauer spectrum from 57Mn decay implanted in silicon 57Mn 1.5m Fedoseyev,- NIMB126 ( 1997) 88 Weyer,- Mat. Science Forum 258 (1997) 437 Laser Resonance Ionization

  12. A project to post-accelerate ISOLDE's beams • First ideas/suggestions for post-acceleration of radioactive ion beams: • “Nuclides far off the Stability Line” (1966) Sweden 1966 • Workshop on Intermediate Energy Physics (1977, CERN) • - discussion on post-acceleration of the ISOLDE beams • - Comments made by H.J. Specht (1981 review): P.G. Hansen, History of CERN Vo. III (1996) 327 • The PRIMA proposal “Post Accelerator for Radioactive Ions of Measurements in Astrophysics” (mid – 80’s) The REX - ISOLDE project

  13. Towards a Proposal for a Post-Accelerator at ISOLDE (1993 – 1994) • Appealing physics case for RIB experiments: • several workshop/conferences/study groups • first ISOL-based RIB facilities (e.g. RIB’s at Louvain-la-Neuve – Belgium) • Existing Q=1+ RIB beams from ISOLDE at 60 keV • Efficient, universal and cost-effective accelerator scheme • Cooler/buncher ion trap: based on ISOLTRAP – CERN • (G. Bollen,- J. Appl. Phys. 68 (1990) 4355) • Fast and efficient charge breeder: based on CRYSIS – Stockholm • (E. Beebe,- NIM B93 (1994) 378, B. Visentin,- NIM B101 (1995) 275) • Cost-effective room temperature LINAC’s: MPI-Heidelberg, GSI-Darmstadt • (R. von Hahn,- EPAC (1992) 1313, U. Ratzinger, Il NuovoCimento A106 (1993) 1583) • Efficient germanium detector array for low-multiplicity events • “.... a more efficient Ge-”mini-ball”, built from large segmented detectors, is being discussed,... At ISOLDE, this experiment could be a main user.” The REX - ISOLDE project

  14. efficiency = 14.5 % Extracted ions per pulse (ppC) Confenement time (ms) Beebe,- NIM B93 (1994) 378 (MSL - Stockholm) Visentin,- NIM B101 (1995) 275 (CEA - Saclay) The REX - ISOLDE project

  15. new extension of the ISOLDE hall • new gamma-ray array for low-multiplicity experiments

  16. REX-ISOLDE proposal: IS347 • Physics case: • Coulomb excitation and one-neutron transfer of very neutron rich (A<32) Na-Mg and (A<52) K-Ca isotopes in the region around the neutron shell closures of N=20 and N=28 • Technical case: • develop a highly efficient and cost-effective way to bunch, charge-state breed and accelerate already existing mass-separated singly-charged radioactive ion beams • CERN Research Board approval: 1995 - First post-accelerated RIB: 31/10/2001 The REX - ISOLDE project

  17. Publicity and first REX-ISOLDE Meeting (the first extension...) The REX - ISOLDE project

  18. Conclusion • ISOLDE's PS-Booster period 1993 - 1995 was characterized by • Technical and instrument developments • Adapt to the new proton beam characteristics of the PS Booster • Laser Ion Source • REX ISOLDE feasibility studies, start of the project. • Experiments immediately making use of these new opportunities and preparing for physics in the years to come (see next talks).

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