current status of the canadian penning trap mass spectrometer at caribu

Graeme Morgan2014 Cap Congress

Current Status of the Canadian Penning Trap Mass Spectrometer

at CARIBU

How are heavy elements formed?

r-process thought to produce almost half of the elements heavier than Iron.

r-processHigh neutron density and temperature required.

Neutron capture and photodissociation reactions compete with each other.

-decay brings the nuclei to a higher Z.

Reaction ends when density and temperature drop and the nuclei decay to stability.

J. Van Schelt – PhD Thesis 2012

Where do we come in?

We can measure those masses!

r-process reaction rates and path location are dependent on neutron separation energies .

Californium Rare Isotope Breeder Upgrade - CARIBU

• source inside Gas Catcher

• Isobar Separator– Resolution of

approximately 1/14000

• Low energy beamline with RFQ Buncher

• Beams can be sent to ATLAS to be re-accelerated for other experiments

J. Van Schelt – PhD Thesis 2012

J. Clark and G. Savard/Int. Journal of Mass Spectrometry 349-350 (2013) 81

Changes to CARIBUNew source!– 1.7Ci source recently installed

Multi-reflection time-of-flight (MR-ToF) mass separator to be constructed and installed by the end of 2014.

R. N. Wolf et. al./Nucl. Instr. and Methods in Physics Research A 686 (2012) 82

We hope to obtain clean beam production of species with fission branches on the order of

- Proposed measurements

How to Measure Masses

Frequencies can be measured with high precision.

A charged particle in a B-field moves in a circular orbit at it’s cyclotron frequency .

�⃗�

𝜔𝑐=𝑞𝐵𝑚

The Canadian Penning TrapParticles held by a quadrupole trapping potential along the B-field axis.

Potential created by shaping the trap electrodes as two hyperboloids of revolution.

J. Clark – PhD Thesis 2005

Ion Motion in Trap

Quadrupole potential provides an axial oscillation independent of B.

is split into 2 eigenfrequencies due to the radial repulsion.

–

=

𝜔±=𝜔𝑐

2 (1±√1− 2𝜔𝑧2

𝜔𝑐2 )

𝜔 𝑧=√ 2𝑞𝑉 0

𝑚(𝑧 02+𝑟 02

2 )

L. Brown and G. Gabrielse/Rev. Mod. Phys. 58 (1986) 233

can be applied as a dipole excitation if the ring electrode is cut in half.

Increases ion orbit radius.

Application of the sum of the two frequencies as a quadrupole is possible with the ring electrode cut into quarters.

orbit is converted to a orbit of the same radius, giving a increase in frequency and a increase in orbital energy.

J. Van Schelt – PhD Thesis 2012

zFF Channeltron TOF

Detection

0 zB LinearEnergy

Magnetic field lines outside the Penning trap

Ions ejected from the Penning trap

0 zB OrbitalEnergy

Time of Flight Method

Figure by D. Lascar

Isotopes examined during Summer 2013

93Sr, 95Sr, 93Rb, 106Mo, 106Tc, 134I-m, 134I-g, 142I, 147Cs, 148Cs, 146La-m, 146La-g, 148Ba, 149Ba, 150Ba, 162Sa, 162Eu, 164Eu, 165Gd

CPT Detector Upgrade

Replacing current Channeltron detector with a position sensitive MCP

Enables phase-imaging ion-cyclotron resonance (PI-ICR) measurements

PI-ICR Measurements

Ions from the Penning trap

The position of the ion in the trap is projected onto the MCP when ejected.

The orbital frequency of the ion’s motion is calculated from the phase change over time.

𝜔=𝜑+2𝜋𝑛

𝑡

S. Eliseev et. al./Phys. Rev. Lett. 110 (2013) 082501

is determined through a ToF measurement of frequency.

What do we gain?• Contaminants become less of an issue.

– No cleaning before an excitation means less time spent in the trap quicker measurements shorter half lives.

• Less statistics required.– Each ion can be identified compared with ToF measurements. Easier

to reach isotopes with lower yields.

• Resolution is not only given by time spent in the trap; it can also be improved by increasing the orbit radius or reducing the radial spread.

𝜔𝑐

∆𝜔𝑐≈ 𝜔+¿

∆𝜔+¿=𝜙+2𝜋𝑛∆𝜙 =𝜋𝜔

+¿𝑡 𝑅+¿

∆ 𝑅+¿ ¿¿¿¿

¿

CPT CollaborationP. Bertone, J.A. Clark, A. Perez Galvan, A.F. Levand, G. Savard

A. Chaudhuri, G. Morgan, K.S. Sharma

S. Caldwell, J. Van Schelt, M. Sternberg

F. Buchinger, J.E. Crawford, G. Li, R. Orford

D. Lascar, R. Segel

A. Aprahamian, S. Marley, M. Mumpower, A. Nystrom, N. Paul, K. Siegl, S. Y. Strauss,R. Surman

S. Eliseev et. al./ Appl. Phys. B 114 (2014) 107