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