1. Magnetic moment measurements with the high-velocity transient field (HVTF) technique at relativistic energies Andrea Jungclaus IEM-CSIC Madrid, Spain Andrew Stuchbery Australian National University Canberra, Australia Instituto de Estructura de la Materia – Consejo Superior de Investigaciones Científicas Jörg Leske TU Darmstadt Darmstadt, Germany

2. Why to measure magnetic moments of short-lived excited states in exotic nuclei ? One example … D.C. Radford et al., Phys. Rev. Lett. 88 (2002) 222501 Te B(E2) anomaly in 136 Te 136 Te N. Benczer-Koller et al., PLB 664(2008)241 Exp. and theoretical g(2 + ) in Te the isotopes  136 Te g-factor is very sensitive to relative proton (neutron) composition of nuclear wavefunction !

3. How to measure magnetic moments ?  /g =  N /ħ·B·t eff Larmor frequency Time integral measurement of the precession angle  L = g ·  N /ħ · B kT fields required for short t eff (<  ) ! Fermi contact field at the nucleus: B 1s = 16.7 Z 3 R(Z) [T] R(Z)  1+(Z/84) 2.5 relativistic correction factor for 1s electrons Magnetic fields of this strength in general available at the nucleus ONLY due to its own electrons ! randomly oriented electron spins: attenuation of  -ray angular distribution “nuclear deorientation” oriented electron spins (polarization): precession of  -ray angular distribution “transient fields” Fermi contact field [Tesla] HOFNeMgSiXe MTesla ! kTesla !

4. Three different techniques to measure g-factors of short-lived states using radioactive beams nuclear deorientation 132 Te @ Oak Ridge 3.0 MeV/u N.J. Stone, A.E. Stuchbery et al., Phys. Rev. Lett. 94 (2005) 192501 38,40 S @ MSU 40 MeV/u A.D. Davies et al., PRL 96 (2006) 112503 A.E. Stuchbery et al., PRC 74 (2006) 054307 42,44,46 Ar @ MSU & N=40 Fe @ MSU October 2008 SP: A.E. Stuchbery 72 Zn @ GANIL 60 MeV/u April 2008 SP: G. Georgiev, A. Jungclaus high-velocity transient field low-velocity transient field 138 Xe @ REX-ISOLDE 2.8 MeV/u 2006/2009 SP: A. Jungclaus, J. Leske 132 Te @ Oak Ridge 3.0 MeV/u N. Benczer-Koller et al., PLB 664(2008)241 Only very few experiments so far advantages and disadvantages of the different techniques still need to be explored ! Nothing yet at relativistic energies !

5. Transient fields: From the low- to the high-velocity regime Transient field strength in Fe host low-energy Coulex intermediate-energy & relativistic Coulex v/c  3-7% maximum around v=Z∙v 0 strength scales with Z 3 (Z 2 in Gd) ξ 1s : degree of polarization of 1s electrons F 1 1s : ion fraction with unpaired 1s electrons B 1s : Fermi contact field of 1s electrons Z∙v 0 : 1s electron velocity v/c  20-50% A.E. Stuchbery et al., Phys. Rev. C74 (2006) 054307 Phys. Lett. B611 (2005) 81 Problem: Transient field strength studied only up to Sulfur (in Canberra). What happens for higher Z ? B tf (v, Z) = ξ 1s (v, Z) · F 1 1s (v, Z) · B 1s (Z) 30 shifts of parasitic 136 Xe beam approved by GSI PAC in 2009 calibration of TF strength in the 132 Sn region !

6. 134 Te 134 Xe angle  (deg) W lab (  ) S nuc (  ), S 2 N Only angular range  40 º and  120 º useful for precession measurement ! How to measure the precession of a  -ray angular correlation with the PRESPEC setup ? 136 Xe primary beam @ 500 MeV/u 2.5 g/cm 2 Be target 100 MeV/u 62 MeV/u 400 mg/cm 2 Gd 83.5 MeV/u 4.1 ps    =3.0(2) ps 2.3 ps 134 Xe Full simulation performed using the code GKINT by A. Stuchbery figure of merit t eff = 1.4 ps, v/Zv 0 = 1.07-0.93  /g = 129 mrad, B ave = 1.9 kTesla Including decay: N=7500 photopeak counts per field per day in Clusters A, D and E LYCCA-0 1.5º 2.1º 0.1º-1.7º

7. Geometry of the PRESPEC Ge array 134 Te P E D A J N PRESPEC 10 o    40 o ! All Ge crystals in the range  40 º and three pairs of Cluster detectors close to the horizontal plane ! B 

8. From the RISING@GSI to the AGATA@GSI setup In case of a successful calibration experiment with the RISING setup we would like to tackle a first physics case in the 132 Sn region with the AGATA@GSI setup ! standard configuration C. Domingo It is still under study whether a larger than the standard distance would lead to a higher sensitivity to the precession.

9. Transient fields (TF) largest around 1s electron velocity Relativistic heavy ions “in principle” well suited for g(2 + ) measurements ! TF strength only known up to Z=16 (30) We need at least one calibration point to tackle the 132 Sn region. Approved parasitic beamtime at GSI ! Magnetic moment information is important (sometime E(2 + ) and B(E2) is not sufficient) ! Summary & Conclusions Once the TF strength is known real physics cases in the 132 Sn region can be studied with the AGATA@GSI setup !