Physics:ISOLTRAP experiment

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ISOLTRAP experiment in the ISOLDE facility at CERN

The high-precision mass spectrometer ISOLTRAP experiment is a permanent experimental setup located at the ISOLDE facility at CERN. The purpose of the experiment is to make precision mass measurements using the time-of-flight (ToF) detection technique.[1] Studying nuclides and probing nuclear structure gives insight into various areas of physics, including astrophysics.[2]

Background

Mass spectrometry is a technique to determine the mass-to-charge ratio of ions. For a radioactive ion beam, there may be many radionuclides present within the beam and mass separation is needed to isolate a specific ion for measurements.

An ion trap uses electric and magnetic fields to capture charged particles in a system. There are multiple types of ion traps using various mechanisms, including the Penning trap. A Penning trap uses a uniform magnetic field and a quadrupole electric field to confine the particle radially and axially respectively.[3]

Experimental setup

ISOLTRAP experimental setup area at ISOLDE

The ISOLTRAP experiment is a high-precision mass spectrometer/separator, consisting of four ion traps. These include a radio-frequency quadrupole (RFQ) trap, a multi-reflection time-of-flight (MR-ToF) mass spectrometer, and two Penning traps.[4]

The RFQ trap is used convert the radioactive ion beam delivered by the ISOLDE facility into low-energy ion pulses, before it is injected into the MR-ToF mass spectrometer.[5] It does this by electrostatically decelerating the ions and then passing them through a buffer-gas-filled environment.[6] The radio-frequency creates an oscillating electric field which confines the ions to a thin line. The ions are guided towards the trapping region by a potential, where they interact with the buffer gas and the energy spread of ions is reduced.[7] This forms a small cloud of ions which is then ejected as a bunch out of the trapping region and transported to the MR-ToF.[8]

Ion detector (left) and MR-ToF mass spectrometer (right)

The MR-ToF mass spectrometer/separator injects and ejects ions, using a switched cavity, and reflects them between two electrostatic mirror sets to increase their flight path.[9] This gives a large resolving power for a short trapping time, and therefore efficient isobaric separation can be performed.[10] The ToF of the ion is measured by an electron multiplier particle detector and can be used to determine the corresponding mass.[11][12]

The two Penning traps following the MR-ToF are the preparation Penning trap and the precision Penning trap.[4] The preparation Penning trap, a large cylindrical trap, is placed in the uniform field of a superconducting magnet.[13][12] The ions are captured and, with high-selectivity, cooled by mass.[14] Mass measurements are made by the precision Penning trap, which uses a radio frequency field to drive cyclotron motion of the ions. The ions are then ejected from the trap and drift to the non-uniform outside (fringe) field of the magnet to an ion detector. Ions that were at resonance due to the radio frequency field reach the detector faster than the others and the ToF can be determined.[14][15]

Results

Doubly magic Nickel from one proton away

Since the start of its operation, ISOLTRAP has measured the masses of hundreds of short-lived radioactive nuclei.[16][17] Initially, the experimental setup consisted of just two Penning traps but since the MR-ToF was installed in 2011, the most exotic nuclides that can be detected are now measured at ISOLTRAP.[4]

One purpose of the ISOLTRAP experimental results is to confirm doubly magic isotopes. Doubly magic isotopes are those that have both numbers of protons and neutrons equal to magic numbers. They are very stable against decay. Results from ISOLTRAP have confirmed that nickel-78 is doubly magic by studying its neighbour, copper-79.[18][19]

External links

References

  1. ↑ "ISOLTRAP | ISOLDE". https://isolde.web.cern.ch/isoltrap. 
  2. ↑ "ISOLTRAP pins down masses of exotic nuclei" (in en-GB). 2004-03-01. https://cerncourier.com/a/isoltrap-pins-down-masses-of-exotic-nuclei/. 
  3. ↑ Brown, L.S.; Gabrielse, G. (1986). "Geonium theory: Physics of a single electron or ion in a Penning trap". Reviews of Modern Physics 58 (1): 233–311. doi:10.1103/RevModPhys.58.233. Bibcode: 1986RvMP...58..233B. http://gabrielse.physics.harvard.edu/gabrielse/papers/1986/Review.pdf. Retrieved 2014-05-01. 
  4. ↑ 4.0 4.1 4.2 Lunney, D; (on behalf of the ISOLTRAP Collaboration) (2017-06-01). "Extending and refining the nuclear mass surface with ISOLTRAP". Journal of Physics G: Nuclear and Particle Physics 44 (6): 064008. doi:10.1088/1361-6471/aa6752. ISSN 0954-3899. Bibcode: 2017JPhG...44f4008L. https://iopscience.iop.org/article/10.1088/1361-6471/aa6752. 
  5. ↑ Herfurth, F; Dilling, J; Kellerbauer, A; Bollen, G; Henry, S; Kluge, H. -J; Lamour, E; Lunney, D et al. (2001-08-11). "A linear radiofrequency ion trap for accumulation, bunching, and emittance improvement of radioactive ion beams" (in en). Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 469 (2): 254–275. doi:10.1016/S0168-9002(01)00168-1. ISSN 0168-9002. Bibcode: 2001NIMPA.469..254H. https://www.sciencedirect.com/science/article/pii/S0168900201001681. 
  6. ↑ Szerypo, J.; Ban, G.; Le Brun, Ch.; Delahaye, P. et al. (Oct 1999). "Design and performance of an RFQ cooler and buncher". Laboratoire de Physique Corpusculaire. https://www.osti.gov/etdeweb/servlets/purl/20071078. 
  7. ↑ Mukherjee, M.; Beck, D.; Blaum, K.; Bollen, G.; Dilling, J.; George, S.; Herfurth, F.; Herlert, A. et al. (Jan 2008). "ISOLTRAP: An on-line Penning trap for mass spectrometry on short-lived nuclides" (in en). The European Physical Journal A 35 (1): 1–29. doi:10.1140/epja/i2007-10528-9. ISSN 1434-6001. Bibcode: 2008EPJA...35....1M. http://link.springer.com/10.1140/epja/i2007-10528-9. 
  8. ↑ Savard, G.; Becker, St.; Bollen, G.; Kluge, H.-J.; Moore, R.B.; Otto, Th.; Schweikhard, L.; Stolzenberg, H. et al. (Sep 1991). "A new cooling technique for heavy ions in a Penning trap" (in en). Physics Letters A 158 (5): 247–252. doi:10.1016/0375-9601(91)91008-2. Bibcode: 1991PhLA..158..247S. https://linkinghub.elsevier.com/retrieve/pii/0375960191910082. 
  9. ↑ Mougeot, M; Algora, A.; Ascher, P.; Atanasov, D. et al. (25 Sep 2019). "Penning-trap mass measurements with ISOLTRAP during the period 2014-2018". European Organization for Nuclear Research. https://cds.cern.ch/record/2690732/files/INTC-SR-091.pdf. 
  10. ↑ Wolf, R. N.; Wienholtz, F.; Atanasov, D.; Beck, D.; Blaum, K.; Borgmann, Ch.; Herfurth, F.; Kowalska, M. et al. (2013-09-01). "ISOLTRAP's multi-reflection time-of-flight mass separator/spectrometer" (in en). International Journal of Mass Spectrometry. 100 years of Mass Spectrometry 349-350: 123–133. doi:10.1016/j.ijms.2013.03.020. ISSN 1387-3806. Bibcode: 2013IJMSp.349..123W. https://www.sciencedirect.com/science/article/pii/S1387380613001115. 
  11. ↑ Karthein, J.; Atanasov, D.; Blaum, K.; Breitenfeldt, M.; Bondar, V.; George, S.; Hayen, L.; Lunney, D. et al. (2019-07-15). "${Q}_{\mathrm{EC}}$-value determination for $^{21}\mathrm{Na}\ensuremath{\rightarrow}^{21}\mathrm{Ne}$ and $^{23}\mathrm{Mg}\ensuremath{\rightarrow}^{23}\mathrm{Na}$ mirror-nuclei decays using high-precision mass spectrometry with ISOLTRAP at the CERN ISOLDE facility". Physical Review C 100 (1): 015502. doi:10.1103/PhysRevC.100.015502. https://link.aps.org/doi/10.1103/PhysRevC.100.015502. 
  12. ↑ 12.0 12.1 "ISOLTRAP". http://isoltrap.web.cern.ch/experiment.html. 
  13. ↑ Fink, Daniel (21 Jun 2010). "The ISOLTRAP Laser-Ablation Ion Source and Q-Value Determination of the 110Pd Double Beta Decay". Institut fur Physik Johannes Gutenberg-Universitat Mainz. https://pure.mpg.de/rest/items/item_912087/component/file_912086/content. 
  14. ↑ 14.0 14.1 König, M.; Bollen, G.; Kluge, H. -J.; Otto, T.; Szerypo, J. (1995-03-31). "Quadrupole excitation of stored ion motion at the true cyclotron frequency" (in en). International Journal of Mass Spectrometry and Ion Processes 142 (1): 95–116. doi:10.1016/0168-1176(95)04146-C. ISSN 0168-1176. Bibcode: 1995IJMSI.142...95K. https://dx.doi.org/10.1016/0168-1176%2895%2904146-C. 
  15. ↑ Eliseev, S.; Blaum, K.; Block, M.; Droese, C.; Goncharov, M.; Minaya Ramirez, E.; Nesterenko, D. A.; Novikov, Yu. N. et al. (2013-02-19). "Phase-Imaging Ion-Cyclotron-Resonance Measurements for Short-Lived Nuclides" (in en). Physical Review Letters 110 (8): 082501. doi:10.1103/PhysRevLett.110.082501. ISSN 0031-9007. PMID 23473137. Bibcode: 2013PhRvL.110h2501E. https://link.aps.org/doi/10.1103/PhysRevLett.110.082501. 
  16. ↑ Herfurth, F.; Ames, F.; Audi, G.; Beck, D.; Blaum, K.; Bollen, G.; Kellerbauer, A.; Kluge, H. J. et al. (2002-08-25). "Mass measurements and nuclear physics-recent results from ISOLTRAP" (in en). Journal of Physics B: Atomic, Molecular and Optical Physics 36 (5): 931–939. doi:10.1088/0953-4075/36/5/312. https://hal.in2p3.fr/in2p3-00012773. 
  17. ↑ Kowalska, Magdalena; for the ISOLTRAP collaboration (2010-02-01). "ISOLTRAP results 2006–2009" (in en). Hyperfine Interactions 196 (1): 199–203. doi:10.1007/s10751-009-0140-4. ISSN 1572-9540. Bibcode: 2010HyInt.196..199K. https://doi.org/10.1007/s10751-009-0140-4. 
  18. ↑ Welker, A.; Althubiti, N. A. S.; Atanasov, D.; Blaum, K.; Cocolios, T. E.; Herfurth, F.; Kreim, S.; Lunney, D. et al. (2017-11-06). "Binding Energy of Cu 79 : Probing the Structure of the Doubly Magic Ni 78 from Only One Proton Away" (in en). Physical Review Letters 119 (19): 192502. doi:10.1103/PhysRevLett.119.192502. ISSN 0031-9007. PMID 29219497. https://link.aps.org/doi/10.1103/PhysRevLett.119.192502. 
  19. ↑ Yirka, Bob; Phys.org. "Nickel-78 confirmed to be doubly magic" (in en). https://phys.org/news/2017-11-nickel-doubly-magic.html. 



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