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Today, research on
nuclear structure far from stability is one of the most exciting frontiers in
nuclear physics since such nuclei allow to amplify and
isolate particular aspects of nuclear interaction and dynamics. The Radioactive
beam EXperiment at ISOLDE (REX-ISOLDE) [1,2,3,4,5] accelerates radioactive ion beams and thus the
full variety of beams available at ISOLDE become accessible as accelerated
beams for experiments.
REX-ISOLDE uses the
method of charge-state breeding to enhance the charge state of the ions before
injection into a linear accelerator. The charge multiplication of the
radioactive ions allows access to the heavier mass region of the nuclear chart,
which cannot be reached by accelerating monocharged
ions.
Fig 1. Schematics
of the ISOLDE and the post accelerating REX-ISOLDE.
REX makes use of the large variety of radionuclides that have been extracted
from the on-line mass separator ISOLDE. The radioactive singly-charged ions from the separators are first
accumulated, bunched and cooled in a Penning trap, REXTRAP.
The trap stores the ions during the breeding in the subsequent charge breeder.
Bunches of ions are then transferred to an electron beam ion source, REXEBIS
where the ions are charge bred to a mass-to-charge ratio below 4.5. Finally,
the ions are injected into a compact linear accelerator via a mass separator.
The linear
accelerator has a total length of about 10 m. It consists of a Radio Frequency Quadrupole (RFQ) accelerator which accelerates ions
from 5 to 300 keV/u, a rebunch
section, an Interdigital H-type (IH) structure that boosts the
energy to 1.2 MeV/u, three seven-gap
resonators which allow the variation of the final energy, and a 9-gap resonator. The final energy is variable between 0.8 and
3.0 MeV/u.
Fig
2. The
REX-ISOLDE post accelerator with the Miniball
The first aim of
REX-ISOLDE was to demonstrate a new concept to bunch, charge-breed and
post-accelerate singly-charged, low energetic ions in an efficient way. Second,
to study the structure of neutron-rich Na, Mg, K and Ca isotopes in the
vicinity of the closed neutron shells N = 20 and N = 28 by Coulomb excitation
and neutron transfer reactions with a highly efficient γ- and
particle-detector array MINIBALL.
The experiment dwells on established techniques, but represents a new way of
combining these structures. Since, 2003, the machine is fully operational
and used for accelerating isotopes with masses up to A>200 for experiments in nuclear physics, astrophysics and solid state physics. Reviews of the machine
performance can be found in ref. [6,7].
Fig
3. The
REX-ISOLDE facility seen from above the experimental stations
Guidelines for
estimation of the accelerated beam intensities are given here.
Beam intensities recorded until 2008 are listed here.
Radioactive elements run in REX so far 8Li3+(2006), 9,11Li2+(2004), 9Li2+(2005), 10,11Be3+,4+(2006), 11,12Be3+,4+(2005), 11Be3+(2009), 11Be3+(2010), 9C3+(2010), 10C3+(2008), 17F5+(2004), 17F5+(2007),24-29Na7+, 29,30Na7+(2009), 26,30Na6+,7+(2011), 29,31Mg9+(2006), 30Mg9+(2007), 30Mg7+(2008), 30,31Mg9+(2007), 28,30,32Mg8+, 44Ar13+, 61,62Mn15+(2008), 62,63Mn15+,17+(2009), 61,62Fe15+(2008), 62Fe21+(2009),68Ni19+(2005), 66,68Ni16+(2009), 66Ni17+(2011), 7070Cu19+(2008), 67,69,71,73Cu19+,20+,20+,19+(2006), 68,69,70Cu19+,20+,19+(2005), 74,76,78Zn18+(2004), 72Zn20+(2011), 72,74,76Zn20+(2011), 78Zn20+(2010), 80Zn21+(2006), 70Se19+(2005), 72Kr17+(2010), 72Kr17+(2011), 88,92Kr21+,22+(2005), 94,96Kr22+,23+(2009), 92,94,96Kr22+,22+,23+(2010), 96Kr23+(2011), 93,95,97,99Rb22+,23+,23+,23+(2010), 96Sr23+(test), 96Sr27+(2007), 98Sr26+(2011), 108In30+(2005), 106,108Sn26+(2006), 107,109Sn26+(2009), 108Sn27+(2005), 110Sn27+(2004), 100,102,104Cd24+,25+,25+(2008), 122,124,126Cd30-31+(2004), 124,126Cd30,31+(2006), 128Cd30+(2011), 138Xe33+ (2009), 138,138,140,142,144Xe34+, 140,142,148Ba33+,33+,35+(2007), 140Nd34+(2011), 148Pm30+, 153Sm28+, 156Eu28+, 184,186,188Hg43+,43+,44+(2007), 182,184,186,188Hg44+,44+,44+,45+(2008), 192Pb45+(2010), 186,188,190,194,196,198Pb44+,44+,44+,45+,46+,46+(2011), 200Po48+(2009), 202,204Rn47+(2008), 202Rn47+(2010), 208,220Rn50+,52+(2011), 224Ra52+(2010), 224Ra52+(2011) Elements
in italic – experiment not successful |
REX running schedule
REX experiments are
outlined in red on the ISOLDE schedule.
1. Radioactive beam
experiment at ISOLDE: Excitation and neutron transfer reactions of exotic
nuclei, proposal to the ISOLDE committee,
2. D. Habs et al. , Nucl.
Instrum. Meth. B139 No 1-4
(1998) p. 128-135
3. O. Kester et al. , Hyperfine Interactions 129 No 1-4 (2000) p. 43-66
4. O. Kester et al. , Nucl. Instrum. Meth. B204 (2003) p. 20-30
5. J. Cederkall
et al. , Nuclear
Physics A, Volume 746 (2004) p. 17-21
6. D. Voulot et al., ‘Radioactive beams at
REX–ISOLDE: Present status and latest developments’, Nucl. Instrum. Meth. B266 (2008) p.4103-4107
7. F. Wenander, ‘Charge breeding of radioactive ions with EBIS and
EBIT’, Journal of Instrumentation, vol5
(2010) C10004
See also the REX-ISOLDE
poster homepage.