Spins, Moments and Charge Radii Beyond 48Ca

INTC-P-313

M.L. Bissell - On behalf of COLLAPS

Background  

Program initiated with IS-484 - “Ground-state properties of K-isotopes from laser and β-NMR spectroscopy”

Extended with I-117 - “Moments, Spins and Charge Radii Beyond 48Ca.”

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)-> 55Ti 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)

54Ca 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 39,40,41,47,48,49,51,50,52,53,54,55,59,60,61Ca. 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 48Ca  

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:

49Ca 2.5x105 /uC Old design UCx49Ca 1.4x107 /uC Ta (Should be equivalent to new UCx)

51Ca 1.0x104 /uC Ta powder (last yield measurements for 51K claimed we had approximately equal amount of K and Ca)

52Ca 1.0x102 /uC T. Stora- Yield will be 1 order of magnitude higher than this. (All yield measurements at the PSB have been in the 1x103 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 .

0 50 100 150 200 250 300 350 40002468

1012141618

Distance from CEC chamber (mm)

Ligh

t co

llecti

on e

ffici

ency

% ∫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=3/2 393.4 nm transition.

4 shifts on 52Ca with 1k ions /μC

3 Such spectra required to reduce systmatics

+ 5 shifts for 51Ca+ 1 shift for 49Ca+ 3 offline shifts directly prior to the run for stable measurements.

Stage 1 total 18 online shifts + 3 offline.

Stage 2 – Radioactive detectionRadioactive detection of Optically pumped ions after state selective Charge exchange (ROC)

C harge exchange ce ll

Ion beamO ptical pum ping zone

Laser beam

Iondece lera tor

β detector

Tape transport

2S 1/2

2P 1/2

2D 3/2

397.0 nm

The theoretical possibilities:1 ion/s of an even isotope over 5 shifts.

An additional 18 shifts 53,54Ca

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=3218 shifts with UCx and RILIS prior to shutdown .

Stage 2 – Investigation of N=3418 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. Papuga1, M.M. Rajabali1 and D. T. Yordanov4