Spins, Moments and Charge Radii Beyond 48 Ca INTC-P-313 M.L. Bissell- On behalf of COLLAPS

Background Program initiated with IS “Ground-state properties of K-isotopes from laser and β-NMR spectroscopy” Extended with I “Moments, Spins and Charge Radii Beyond 48 Ca.” Substantial theoretical interest and recent developments encourage us to bring forward part of this program

New magic numbers N = 32, 34 Whilst β-decay spectroscopy, deep inelastic scattering and Coulomb- excitation experiments have all provided evidence for a sub-shell closure at N=32, no direct experimental evidence exists for such a closure at N=34. Maierbeck et al., Phys. Lett. B 675, 22 (2009) -> 55 Ti has a 1/2 − ground state. GXPF1A predicts this, KB3G predicts 5/2 − A.Gade, T. Glasmacher, Progress in Particle and Nuclear Physics 60, 161–224 (2008) 54 Ca is “the key nucleus for a search for the new magic number N=34.”

Ca: An ideal testing ground for theory Gaute Hagen (Oak Ridge) : “I think it would really great idea for a proposal to measure the neutron rich calciums. We can within coupled- cluster theory compute radii, masses, spectra and moments of 39,40,41,47,48,49,51,50,52,53,54,55,59,60,61 Ca. So basically its only a few calciums we cannot compute at the moment. To have experiments measure radii and moments of the n-Ca would be of really huge interest for the theory community and provide tests for ab-initio approaches.”

Ca: An ideal testing ground for theory Existing charge radii of Ca are probably the most theoretically investigated of any isotopic chain: I.Talami, Nucl. Phys. A 423, 189 (1984) -> Linear + Parabolic + OES Each of these terms related to particular components of the interaction used.

Charge radii beyond 48 Ca Fe -> Normal OES Mn -> Downturn at N=31 but could be just OES. IS-508 will extend this beyond N=32 K -> Preliminary results indicate a downturn at N=32. Statistics to be improved.

Only old SC yields available on the database: 49 Ca2.5x10 5 /uC Old design UCx 49 Ca1.4x10 7 /uC Ta (Should be equivalent to new UCx) 51 Ca1.0x10 4 /uCTa powder (last yield measurements for 51 K claimed we had approximately equal amount of K and Ca) 52 Ca1.0x10 2 /uC T. Stora- Yield will be 1 order of magnitude higher than this. (All yield measurements at the PSB have been in the 1x10 3 range.) + Possible factor of 10 from RILIS Yields

Stage 1 – Optical detection Optical detection efficiency for K improved from 1 : 300 k to 1 in 20 k + low background. ∫η(new) dx / ∫η(existing) dx ≈14 For Cd we observed 1 in 6k -> 1 in 4k for Ca

What is possible? Strong ionic J=1/2 to J=3/ nm transition. 4 shifts on 52 Ca with 1k ions /μC 3 Such spectra required to reduce systmatics + 5 shifts for 51 Ca + 1 shift for 49 Ca + 3 offline shifts directly prior to the run for stable measurements. Stage 1 total 18 online shifts + 3 offline.

Stage 2 – Radioactive detection Radioactive detection of Optically pumped ions after state selective Charge exchange (ROC) The theoretical possibilities: 1 ion/s of an even isotope over 5 shifts. An additional 18 shifts 53,54 Ca

Why is stage 2 stage 2? ROC is not ideally suited to odd cases. We must introduce multiple pumping. In the previous setup it was not possible to reliably focus both the ion and atom beam onto the detectors. -> Shutdown will be an ideal time to develop this.

Summary of Request Stage 1 – Investigation of N=32 18 shifts with UCx and RILIS prior to shutdown. Stage 2 – Investigation of N=34 18 shifts with UCx and RILIS after the shutdown.

Collaboration M. L. Bissell, 1 K. Blaum, 2 I. Budincevic, 1 N.Frömmgen, 3 R.F. Garcia Ruiz, 1 Ch. Geppert, 3 M. Hammen, 3 M. Kowalska, 4 K. Kreim, 2 P. Lievens, 5 R. Neugart, 3 G. Neyens, 1 W. Nörtershäuser, 3 J. Papuga 1, M.M. Rajabali 1 and D. T. Yordanov 4