The REXTRAP Penning Trap

1
The REXTRAP Penning Trap
Pierre Delahaye, CERN/ISOLDE
Its potential use for nuclear spectroscopy?
Friedhelm Ames, Pierre Delahaye, Fredrik Wenander
and the REXISOLDE collaboration
TAS workshop, LPC CAEN, 30/03/2004
2
The REX-ISOLDE facility
Acceleration of exotic nuclei delivered by
ISOLDE/CERN

• Ion beam cooling in REXTRAP
• Charge breeding in REXEBIS
• Acceleration in the LINAC

A/q4.5
3
Beam preparation at REX-ISOLDE
REXTRAP and REXEBIS
breeding time (A/q lt 4.5) 20 msbeam
intensities lt 109 /sions in one charge state
lt 30injection efficiency into EBIS
40efficiency REXTRAP 40
If the number of ions inside the trap is not too
big (lt107,108) If the charge exchange process is
negligible
4
The REXTRAP Penning trap
Cylindrical trap filled by Ne as buffer gas
P. Schmidt et al, Nucl. Phys. A 701(2002)550
5
Radioactive ion beam manipulation
Tests of the cooling methods
DE
Accumulation
Cooling
Ejection
Sideband Cooling
Viscous force F -? m v ? r (t) ? r(0) e -?/2
t example Na 10-4 mbar Ne d 400
s-1 tcooling20 ms
Quadrupolar excitation at wcqB/M in the
transverse plane of the trap Magnetron and
cyclotron motions coupling
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Sideband Cooling
Emittance reduction with the Sideband cooling
method
3.8 104 trapped and ejected ions E8010.6
p.mm.mrad ERMS3.9 p.mm.mrad
3.2 104 trapped and ejected ions E8030.1
p.mm.mrad ERMS9.4 p.mm.mrad
Injection efficiency in REXEBIS 45 Nionslt106
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Rotating Wall cooling
Rotating Wall cooling
B
Dipolar Excitation
Quadrupolar Excitation
The Lorentz force compress the ion cloud
Interesting for high number of ions gt 106
8
Rotating wall cooling
Resonance frequencies
39K ions
Resonance frequencies Excitation modes of the non
neutral plasma
Experimental results Dipolar excitation
wz Quadrupolar excitation wz, wc
wz
wc
9
Charge exchange investigation

• Noble gases high ionization energies

Losses due to the charge exchange process
Sideband excitation
Quantitative information about charge exchange
cross sections?
10
Nuclear spectroscopy experiments at REX-ISOLDE
Radioactive EXperiments at ISOLDE
The MINIBALL detector 8 Germanium clusters
Progress in Particle and Nuclear Physics
46(2001)389
Coulomb excitation and nucleon transfer reactions
to probe the structure of the exotic nuclides

• Last year
• 30,31,(32)Mg B(E2,0-gt2) N20
• 72,74,(76)Zn B(E2,0-gt2) 40N50
• 6,7,8,9(11)Li 11Li Polarizability
• 88Kr B(E2,0-gt2)

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Beam developments with REXTRAP
Molecule breakup in the buffer gas

• SeCO Shape coexistence around mass 70
• AlF Study of the stellar reaction 14O(a,p)17F
• SnS B(E2,0-gt2) towards doubly magic 100Sn

Preliminary result F with 20 efficiency
New beams available!
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In-trap spectroscopy
In-trap conversion electron spectroscopy
L. Weissman et al, NIM A 492(2002)451
Study of the feasibility of such spectroscopy
technique
B3T
Tests with well known electron sources 116m2In,
118m2In, 221Fr (a)
Cooled pin diode
Trap center

• Drawbacks
• 60 keV background, low energy background
• charge space induce resolution limitations
• buffer gas pressure limitation
• Detector in a high magnetic field

• Advantages
• high efficiency
• no implantation
• Can be used for ion cloud imagery

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Conclusion

• REXTRAP as a first stage of REX-ISOLDE is an
  efficient and/or interesting setup for
• radioactive beam cooling (emittance reduction)
• beam developments
• breakup of molecules
• study of charge exchange process
• The possibility for conversion electron
  spectroscopy has been studied
• Strong technical limitations
• A dedicated setup could be more adapted