TRIUMF Summer Institute, 2015 Precision Measurements of Nuclear - - PowerPoint PPT Presentation

Klaus.blaum@mpi-hd.mpg.de

TRIUMF Summer Institute, 2015 “Precision Measurements of Nuclear Masses – Part 2”

Klaus Blaum 113th-25th July 2015

Lecture 2

What did we learn? 1) Motivation for precision mass data 2) Liquid drop model and nuclear binding energy 3) Production of radioactive ions 4) Storage of charged particles 5) Penning trap technique What comes today? 1) Manipulation of stored ions 2) Frequency measurement techniques 3) Experimental setup 4) Applications of precision nuclear mass data * Nuclear physics and astrophysics

Storage of ions in a Penning trap

Ion q/m Charge q Mass m

U

B

The free cyclotron frequency is inverse proportional to the mass of the ions!

m qB

c

/ = ω

L.S. Brown, G. Gabrielse, Rev. Mod. Phys. 58, 233 (1986).

• K. Blaum, Phys. Rep. 425, 1 (2006).

ωc

2 = ω+ 2+ω- 2+ωz 2

ωc = ω+

+ ω-

An invariance theorem saves the day:

Ion preparation and cooling

Ion beam cocktail: R=102-103 (Selection by dipole magnets)

Buffer-gas (He) in preparation trap Motional amplitudes are reduced Well-controlled conditions

buffer-gas (He) contaminent ions Ions of interest

Mass selective buffer-gas cooling

Dipolar excitation at magnetron frequency (≈ mass independent)

Resolving Power R=105

• G. Savard et al., Phys. Lett. A 158 (1991) 247.

Quadrupolar excitation at the cyclotron frequency (mass selective recentering)

Cooled ions

Manipulation of ion motions

Dipolar excitation Quadrupolar excitation

Destructive ion detection

Non-destructive ion detection

very small signal ~fA ion signal Amplitude mass/frequency spectrum

„FT-ICR“ Fourier-Transform- Ion Cyclotron Resonance

TRIGA-SPEC: TRIGA-LASER + TRIGA-TRAP

TRIGA-TRAP TRIGA-LASER

• W. Nörtershäuser

ECR ion source

Mass separator RFQ

• Nucl. Instrum. Meth. A 594, 162 (2008)

project start @ TRIGA: 01/08 start data taking: 05/09

Nuclear structure and astrophysics studies

4

Nuclear structure studies

In collaboration with CERN, GSI, TU Darmstadt, Greifswald, Dresden, Paris.

Chart of nuclides and magic numbers

H D T

Ca

Investigation of nuclear halos

3/2 - 0 keV 375 keV

9Li +2n

11Li

11Li 207Pb

large matter radius weakly bound

characteristic properties of nuclear halos

probing halo neutron – nucleus interaction

increased charge radius

rc

9

rc

11 =

?

11Be: Phys. Rev. Lett. 102, 062503 (2009)

7Be 7Be 8Be 8Be 9Be 9Be 10Be 10Be 11Be 11Be 11Be

7 . 7 f m

11Be 11Be

7 . 7 f m

12Be

„Size“ & structure studies of 11,12Be

12Be: Phys. Rev. Lett. 108, 142501 (2012)

COLLAPS (ISOLDE) TITAN (TRIUMF)

Ca masses pin down nuclear forces

Production rates of ~10 ions/s Mass measurements via S2n establish new magic number at N = 32 Correct prediction from 3N-forces (A. Schwenk et al., TUD)

Multi-reflection time-of-flight and Penning-trap mass spectrometry

53,54Ca

ISOLTRAP (CERN), TITAN (TRIUMF)

B

51,52Ca

• F. Wienholtz et al., Nature 498, 346 (2013)
• R. Wolf et al., Int. J. Mass Spec. 349, 123 (2013)
• T. Dickel et al., Nucl. Instrum. Meth. B 317, 779 (2013)

Z=20 Ca N=31,32 TITAN

N = 28 magic number N = 32 magic number

PRL 114, 202501 (2015)

Direct Mapping of Nuclear Shell Effects

ChemistryWorld: Tweaked weighing scales help map the island of stability

SHIPTRAP (GSI)

• E. Minaya Ramirez et al., Science 337, 1207 (2012)

Where is the predicted “island of stability“?

256Lr with the lowest

yield ever measured in a Penning trap (2 ions/ minute)

Question

1+ 6- 1+

240 270 300 330 360 390 240 270 300 330 360 390 260 280 300 320 340 360 380 400 mean TOF (us) fexc - 1338940 (Hz) 5 10 15 20 25 30 35

6-

1) Which one is the ground and the isomeric state? Why? 2) What is the observed reolving power? 3) What was the excitation Trf time to get this line width? 4) The reference ions was 85Rb with mass m85,Rb = 84,911789732(14) u. The measured frequency ratio was 0,800000818(20) for 68gCu and 0,800009879(19) for 68mCu. Calculate for both states the mass excess in keV defined by D = m − Au. 5) What is the escitation energy of the isomeric state?

Masses

CPT, CSRe, ESR, ISOLTRAP, JYFLTRAP, LEBIT, SHIPTRAP, TITAN

Nuclear astrophysics studies

Why is iron so much abundant than heavier elements such as gold? Why are there heavy elements at all and how did they come into existence?

Mass spectrometry for nucleosynthesis

Nuclear masses (binding energies) determine the paths of the processes.

Can be addressed at FAIR

• A. Arcones et al.

Nuclides at the rp-process path

νp – process

• C. Weber et al., Phys. Rev. C 78, 054310 (2008)

V.-V. Elomaa et al., Phys. Rev. Lett. 102, 252501 (2009)

• E. Haettner et al., Phys. Rev. Lett. 106, 122501 (2011)
• F. Herfurth et al., Eur. Phys. J. A, 47,75 (2011)

CSRe (IMP, Lanzhou)

• X. Tu et al., Phys. Rev. Lett. 106, 112501 (2011)

JYFLTRAP (IGISOL)

Nuclear astrophysics: Neutron star

Composition of the outer crust of a neutron star

δm/m ~ 10-8 (< 1 keV)

• R. Wolf et al., Phys. Rev. Lett., 110, 041101 (2013)

(T1/2 ~ 200ms)

Nuclear astrophysics: r-process

Compare calculated abundance to observation

• A. Arcones et al.,2012

MNRAS.426.1940 (γ,n) photo- disintegration equilibrium favours “waiting point”

β-decay

seed

rapid neutron capture

N Z

Mismatch comes from:

• n-star-merger conditions!
• Nuclear physics input not

correct.  Need nuclear physics experiments & theory for predictions!

• H. Schatz et al.

End of Lecture 2

What did we learn? 1) Storage, manipulation, detection of stored ions 2) Frequency measurement techniques 3) Applications of precision nuclear mass data

• Nuclear structure studies
• Nuclear astrophysics studies

What comes next? 1) Further applications of precision nuclear mass data

• Test of fundamental symmetries
• Neutrino physics applications

2) Future facilities