Radioactive Beam EXperiment at ISOLDE
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 amass
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,
anInterdigital
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. A review of the machine performance can be found in
ref. [6].
Fig 3. The REX-ISOLDE facility seen
from above the experimental stations
Radioactive elements run
in REX so far
(click on the mass for machine summary of the run):
8Li3+(2006), 9,11Li2+(2004), 9Li2+(2005), 10,11Be3+,4+(2006), 11,12Be3+,4+(2005),
10C3+(2008), 17F5+(2004), 17F5+(2007),24-29Na7+, 29,31Mg9+(2006), 30Mg9+(2007),
30Mg7+(2008), 30,31Mg9+(2007), 28,30,32Mg8+, 61,62Mn15+(2008), 61,62Fe15+(2008),
68Ni19+(2005), 70Cu19+(2008),
67,69,71,73Cu19+,20+,20+,19+(2006),68,69,70Cu19+,20+,19+(2005),
74,76,78Zn18+(2004), 80Zn21+(2006), 70Se19+(2005), 88,92Kr21+,22+, 96Sr23+(test),
96Sr27+(2007), 108In30+(2005), 106,108Sn26+(2006), 108Sn27+(2005), 110Sn30+(2004),
100,102,104Cd24+,25+,25+(2008), 122,124,126Cd30-31+(2004), 124,126Cd30,31+(2006),
138,138,140,142,144Xe34+, 140,142,148Ba33+,33+,35+(2007), 148Pm30+, 153Sm28+,156Eu28+,
184,186,188Hg43+,43+,44+(2007), 182,184,186,188Hg44+,44+,44+,45+(2008),202,204Rn47+(2008)