the rextrap penning trap pierre delahaye, cern/isolde friedhelm ames, pierre delahaye, fredrik...
TRANSCRIPT
The REXTRAP Penning Trap
Pierre Delahaye, CERN/ISOLDE
REX- ISOLDE
Friedhelm Ames, Pierre Delahaye, Fredrik Wenander and the REXISOLDE collaboration
TAS workshop, LPC CAEN, 30/03/2004
Its potential use for nuclear spectroscopy?
The REX-ISOLDE facility Acceleration of exotic nuclei delivered by ISOLDE/CERN
Ion beam cooling in REXTRAPCharge breeding in REXEBISAcceleration in the LINAC
A/q≤4.5
Beam preparation at REX-ISOLDE
REXTRAP and REXEBIS
PENNING Trap
EBISA/q<4.5
ISOLDEbeam60 keV
HV platform60 kV
HV platform20-60 kV
Separator(q/A)/(q/A)= 1/150
tra
nsf
er
bea
m li
ne
cooled beam of singlycharged ions 60 keV
highly chargedions 5 keV/u
REXTRAP
REX EBIS
q/A-selector
breeding time (A/q < 4.5) 20 ms
beam intensities < 109 /s
ions in one charge state < 30%
injection efficiency into EBIS 40%
efficiency REXTRAP 40%
breeding time (A/q < 4.5) 20 ms
beam intensities < 109 /s
ions in one charge state < 30%
injection efficiency into EBIS 40%
efficiency REXTRAP 40%
If the number of ions inside the trap is not too big (<107,108) If the charge exchange process is negligible
The REXTRAP Penning trapCylindrical trap filled by Ne as buffer gas
1m
Center electrodes
Injection plateEjection plate
Pulse drift tube
Magnet 3T – Trap electrodes
trappingejecting
10
10
10
-3
-4
-5
300
200
1000
-50-800 600 400 200 0 800 400 600 800
Z (mm)
p (
mb
ar)
U(V
)
Buffer gas pressure
Electric potential
P. Schmidt et al, Nucl. Phys. A 701(2002)550
Radioactive ion beam manipulation Tests of the cooling methods
E
Accumulation Cooling Ejection
Sideband Cooling
Quadrupolar excitation at c=qB/M in the transverse plane of the trapMagnetron and cyclotron motions coupling
Viscous force F = - m v r (t) r(0) e -/2 t
example Na+ 10-4 mbar Ne d = 400 s-1
cooling≈20 ms
Emittance reduction with the Sideband cooling method
3.2 104 trapped and ejected ionsE80%=30.1 .mm.mradERMS=9.4 .mm.mrad
3.8 104 trapped and ejected ionsE80%=10.6 .mm.mradERMS=3.9 .mm.mrad
Injection efficiency in REXEBIS 45% Nions<106
Sideband Cooling
BB
Dipolar Excitation Quadrupolar Excitation
Rotating Wall cooling
The Lorentz force compress the ion cloud
B
Rotating Wall cooling
Interesting for high number of ions > 106
Quadrupolar excitation
Dipolar excitation
Resonance frequenciesExcitation modes of the non neutral plasma
Experimental results
Dipolar excitation: #z
Quadrupolar excitation: #z, c
39K+ ions
Resonance frequencies
z c
Rotating wall cooling
Sideband excitation
Noble gases: high ionization energies
Losses due to the charge exchange process
Charge exchange investigation
40Ar+ ions
ms142 s7.2
78Kr+ ions 130Xe+ ions
ms115Quantitative information about charge exchange cross sections?
Nuclear spectroscopy experiments at REX-ISOLDE Radioactive EXperiments at ISOLDE
The MINIBALL detector: 8 Germanium clusters
Coulomb excitation and nucleon transfer reactions to probe the structure of the exotic nuclides
Last year: 30,31,(32)Mg B(E2,0+->2+) N=2072,74,(76)Zn B(E2,0+->2+) 40≤N≤50 6,7,8,9(11)Li 11Li Polarizability 88Kr B(E2,0+->2+)
Progress in Particle and Nuclear Physics 46(2001)389
Beam developments with REXTRAP Molecule breakup in the buffer gas
SeCO+ Shape coexistence around mass 70 AlF+ Study of the stellar reaction 14O(,p)17F SnS+ B(E2,0+->2+) towards doubly magic 100Sn
New beams available!
Preliminary result: F+ with 20% efficiency
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
Cooled pin diode
B=3T
Trap center
Advantages:high efficiencyno implantationCan be used for ion cloud imagery
Drawbacks: 60 keV background, low energy background charge space induce resolution limitations buffer gas pressure limitation Detector in a high magnetic field
Tests with well known electron sources:116m2In, 118m2In, 221Fr ()
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 studiedStrong technical limitationsA dedicated setup could be more adapted