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TRIμP – a radioactive isotope trapping facility under construction at KVI
Nuclear Instruments and Methods in Physics Research B 204 (2003) 532–535 www.elsevier.com/locate/nimb
TRIlP – a radioactive isotope trapping facility under construction at KVI G.P. Berg, P. Dendooven *, O. Dermois, M.N. Harakeh, R. Hoekstra, K. Jungmann, S. Kopecky, R. Morgenstern, A. Rogachevskiy, R. Timmermans, L. Willmann, H.W. Wilschut Kernfysisch Versneller Instituut, Rijksuniversiteit Groningen, Zernikelaan 25, 9747 AA Groningen, The Netherlands
Abstract At the Kernfysisch Versneller Instituut a new facility (TRIlP) is under development which aims to investigate fundamental interactions using radioactive ions. A spectrum of radioactive isotopes will be produced in inversekinematics and fragmentation reactions using heavy-ion beams from the superconducting cyclotron AGOR. The reaction products will be separated from the primary beam in a dual-mode recoil and fragment separator. The beam of isotopes of interest will be transformed into a low-energy, high-quality, bunched beam and, after neutralization, stored in an atom trap. The emphasis will be put on studying the origin of parity violation via b–m angular correlations and the search for permanent electric dipole moments of atoms and nuclei. The facility will be open to outside users; suggestions for collaborations to extend the scientific program are encouraged. Ó 2003 Elsevier Science B.V. All rights reserved. PACS: 29; 32.80.P Keywords: Radioactive beams; Atom traps; Physics beyond the standard model
1. Introduction At the Kernfysisch Versneller Instituut (KVI) in Groningen, The Netherlands, the new research programme TRIlP (Trapped Radioactive Isotopes: micro-laboratories for Fundamental Physics) was recently started [1]. Its main objective is to investigate fundamental interactions in nature using radioactive atoms and ions. In particular, tests of physics beyond the standard model of particle
*
Corresponding author. Tel.: +31-50-363-3615; fax: +31-50363-4003. E-mail address: [email protected] (P. Dendooven).
physics shall be carried out. A general user facility for radioactive isotopes will be ready for first experiments by the end of 2004. In this paper, the layout of the facility and the scientific goals of the programme are introduced. 2. Scientific programme The scientific programme will be pursued in precision studies of the electro-weak interaction in nuclear and atomic physics processes using radioactive isotopes in atom and ion traps. The in-house research will initially concentrate on two types of experiments:
0168-583X/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-583X(02)02127-4
G.P. Berg et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 532–535
(1) The origin of parity violation will be studied via b–m angular correlations in nuclear b decay [2]. Suitable isotopes could be 19 Ne, 20 Na and 21 Na. Of particular interest is a measurement of the correlation coefficient D which is connected to the operator ~ J ~ p ~ q, ~ J being the nuclear spin, ~ p the b-particle momentum and ~ q the neutrino (recoil–nucleus) momentum. This measurement has a high-potential for limiting certain theories beyond the standard model. (2) Searches will be performed for permanent electric dipole moments (edm) of atoms and nuclei [3]. This strongly relates to searches for new sources of CP violation, which are needed to explain the matter–antimatter asymmetry in the universe. Atomic and nuclear amplifications of a fundamental particle edm are predicted to increase with increasing atomic number; for radium some extra enhancements are expected [4]. In light of this, the radium isotopes appear to be interesting choices. The facility built with the above scientific goals in mind will lay the foundation of a much broader research programme in nuclear and atomic physics.
3. Technical description The different components of the TRIlP facility are shown schematically in Fig. 1. The radioactive isotopes of interest are produced using beams from
Fig. 1. Conceptual view of the TRIlP facility in terms of its scientific potential. The energy labels indicate the typical kinetic energy scales.
533
the superconducting cyclotron AGOR [5]. The reaction products are separated from the primary beam by a magnetic separator. At the end of the separator, the high-energy radioactive-ion beam is transformed into a low-energy, high-quality and bunched beam. This beam can be sent to either an atom trap or an ion (Penning) trap. Some of the components are described in more detail in the following. 3.1. Production of radioactive isotopes The isotopes will be produced in inverse-kinematics or fragmentation reactions. The development of the ECR ion source to deliver the necessary beams up to the heaviest stable elements is under way. In the design phase, various production reactions were studied: projectile fragmentation, direct reactions (e.g. for 20 Na, 21 Na) and fusion–evaporation (e.g. for Ra isotopes). Estimated target production rates for all reactions under consideration are in excess of 106 /s, which is sufficient for the planned experiments. 3.2. The separator Because of the different types of nuclear reactions which will be used, a dual-mode magnetic device has been designed (Fig. 2). It is a combined fragment and recoil separator. In fragment–separator mode (used with projectile fragmentation and direct reactions), target station 1 at the entrance of
Fig. 2. Layout of the TRIlP dual-mode separator. The separator can be used in fragment–separator (target station 1) and in gas-filled (target station 2) mode.
534
G.P. Berg et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 532–535
Table 1 Specifications of the TRIlP dual-mode separator Solid angle Momentum range Resolving power Max. Bq (reaction) Max. Bq (beam)
30 mrad in both transverse directions 2.4% in the dispersive horizontal plane p=dp ¼ 1000 (without gas-filling) 3.0 Tm for reaction products 3.6 Tm (AGOR cyclotron and beamline limit, up to target 2)
3.4. Atom trap A critical stage between the ion beam cooler and the atom trap is the neutralisation of the beam. This topic is presently under investigation. The construction of an atom trap will benefit greatly from the expertise already available at the KVI (see e.g. [7,8]). 3.5. Ion trap
the system is used. The first section is then horizontally dispersive and focusing, allowing the separation by a slit system due to differences in magnetic rigidity between beam and reaction products. The second part can provide an achromatic focus at the end of the separator or may serve as an additional energy-loss separator if a wedge is placed in the focal plane between both parts. In a second mode of operation, gas-filling of the second part is used to efficiently collect heavy-ion products which can be spread out over many atomic charge states (e.g. in fusion–evaporation reactions). In this case, target station 2 in the middle of the separator is used. The first part of the separator then acts as beamline. The main specifications of the system are summarised in Table 1. 3.3. Conversion from high to low energy A gas-catcher system to be placed in the final focus of the TRIlP separator system is being considered for the transformation of the highenergy radioactive-ion beam to a low-energy one. In the gas-catcher system, the high-energy ions are thermalized in a helium- or argon-filled cell. The thermalized ions are extracted at a low-charge state by using electric fields and transported as a low-energy ion beam through an RF multipole into a low-pressure region. Alternate methods, using stopping in and diffusion out of a solid and subsequent ionization, are considered as well. The singly charged beam is then injected into an ion beam cooler: a gas-filled radio-frequency quadrupole (RFQ) structure (see e.g. [6]). Collisions with the gas-atoms cool the beam. Axial segmentation of the RFQ rods allows to trap the ions and release them in short bunches.
The TRIlP facility foresees the installation of a Penning trap for ions of radioactive isotopes, thus creating the possibility for high accuracy experiments on nuclear properties such as e.g. masses and g-factors [9].
4. Outlook The TRIlP facility is expected to be ready for experiments by the end of 2004. In 2001, TRIlP became a managed programme of FOM with funding awarded until 2013 and a mid-term review planned in 2008. It is projected that the TRIlP facility will eventually use 50% of the beam time at the AGOR cyclotron. The facility will be available to outside users via the submission of experiment proposals to the Programme Advisory Committee of KVI.
Acknowledgements This work is funded by the Stichting voor Fundamenteel Onderzoek der Materie (FOM) with financial support from the Nederlandse Organisatie voor Weterschappelijk Onderzoek, the Rijksuniversiteit Groningen (RuG) and in the framework of RTD projects of the European Union (NIPNET, Ion Catcher).
References [1] FOM Programme #48. Available from.
G.P. Berg et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 532–535 [2] P. Herczeg, Prog. Part. Nucl. Phys. 46 (2001) 413. [3] I.B. Khriplovich, S.K. Lamoreaux, CP Violation Without Strangeness, Springer-Verlag, Berlin, 1997. [4] V.A. Dzuba, V.V. Flambaum, J.S.M. Ginges, Phys. Rev. A 61 (2000) 062509. [5] H.W. Schreuder (for the AGOR group), in: E. Baron, M. Lieuvin (Eds.), Proceedings of the 15th International Conference on Cyclotrons and their Applications (Caen, France, 1998), IoP, Bristol, 1999.
535
€ yst€ [6] A. Nieminen, J. Huikari, A. Jokinen, J. A o, P. Campbell, E.C.A. Cochrane, Nucl. Instr. and Meth. A 469 (2001) 244. [7] J.W. Turkstra, H.W. Wilschut, D. Meyer, R. Hoekstra, R. Morgenstern, Hyperfine Interact. 127 (2000) 533. [8] J.W. Turkstra, R. Hoekstra, S. Knoop, D. Meyer, R. Morgenstern, R.E. Olson, Phys. Rev. Lett. 87 (2001) 123202. [9] G. Savard, G. Werth, Annu. Rev. Nucl. Part. Sci. 50 (2000) 119.
TRIlP – a radioactive isotope trapping facility under construction at KVI G.P. Berg, P. Dendooven *, O. Dermois, M.N. Harakeh, R. Hoekstra, K. Jungmann, S. Kopecky, R. Morgenstern, A. Rogachevskiy, R. Timmermans, L. Willmann, H.W. Wilschut Kernfysisch Versneller Instituut, Rijksuniversiteit Groningen, Zernikelaan 25, 9747 AA Groningen, The Netherlands
Abstract At the Kernfysisch Versneller Instituut a new facility (TRIlP) is under development which aims to investigate fundamental interactions using radioactive ions. A spectrum of radioactive isotopes will be produced in inversekinematics and fragmentation reactions using heavy-ion beams from the superconducting cyclotron AGOR. The reaction products will be separated from the primary beam in a dual-mode recoil and fragment separator. The beam of isotopes of interest will be transformed into a low-energy, high-quality, bunched beam and, after neutralization, stored in an atom trap. The emphasis will be put on studying the origin of parity violation via b–m angular correlations and the search for permanent electric dipole moments of atoms and nuclei. The facility will be open to outside users; suggestions for collaborations to extend the scientific program are encouraged. Ó 2003 Elsevier Science B.V. All rights reserved. PACS: 29; 32.80.P Keywords: Radioactive beams; Atom traps; Physics beyond the standard model
1. Introduction At the Kernfysisch Versneller Instituut (KVI) in Groningen, The Netherlands, the new research programme TRIlP (Trapped Radioactive Isotopes: micro-laboratories for Fundamental Physics) was recently started [1]. Its main objective is to investigate fundamental interactions in nature using radioactive atoms and ions. In particular, tests of physics beyond the standard model of particle
*
Corresponding author. Tel.: +31-50-363-3615; fax: +31-50363-4003. E-mail address: [email protected] (P. Dendooven).
physics shall be carried out. A general user facility for radioactive isotopes will be ready for first experiments by the end of 2004. In this paper, the layout of the facility and the scientific goals of the programme are introduced. 2. Scientific programme The scientific programme will be pursued in precision studies of the electro-weak interaction in nuclear and atomic physics processes using radioactive isotopes in atom and ion traps. The in-house research will initially concentrate on two types of experiments:
0168-583X/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-583X(02)02127-4
G.P. Berg et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 532–535
(1) The origin of parity violation will be studied via b–m angular correlations in nuclear b decay [2]. Suitable isotopes could be 19 Ne, 20 Na and 21 Na. Of particular interest is a measurement of the correlation coefficient D which is connected to the operator ~ J ~ p ~ q, ~ J being the nuclear spin, ~ p the b-particle momentum and ~ q the neutrino (recoil–nucleus) momentum. This measurement has a high-potential for limiting certain theories beyond the standard model. (2) Searches will be performed for permanent electric dipole moments (edm) of atoms and nuclei [3]. This strongly relates to searches for new sources of CP violation, which are needed to explain the matter–antimatter asymmetry in the universe. Atomic and nuclear amplifications of a fundamental particle edm are predicted to increase with increasing atomic number; for radium some extra enhancements are expected [4]. In light of this, the radium isotopes appear to be interesting choices. The facility built with the above scientific goals in mind will lay the foundation of a much broader research programme in nuclear and atomic physics.
3. Technical description The different components of the TRIlP facility are shown schematically in Fig. 1. The radioactive isotopes of interest are produced using beams from
Fig. 1. Conceptual view of the TRIlP facility in terms of its scientific potential. The energy labels indicate the typical kinetic energy scales.
533
the superconducting cyclotron AGOR [5]. The reaction products are separated from the primary beam by a magnetic separator. At the end of the separator, the high-energy radioactive-ion beam is transformed into a low-energy, high-quality and bunched beam. This beam can be sent to either an atom trap or an ion (Penning) trap. Some of the components are described in more detail in the following. 3.1. Production of radioactive isotopes The isotopes will be produced in inverse-kinematics or fragmentation reactions. The development of the ECR ion source to deliver the necessary beams up to the heaviest stable elements is under way. In the design phase, various production reactions were studied: projectile fragmentation, direct reactions (e.g. for 20 Na, 21 Na) and fusion–evaporation (e.g. for Ra isotopes). Estimated target production rates for all reactions under consideration are in excess of 106 /s, which is sufficient for the planned experiments. 3.2. The separator Because of the different types of nuclear reactions which will be used, a dual-mode magnetic device has been designed (Fig. 2). It is a combined fragment and recoil separator. In fragment–separator mode (used with projectile fragmentation and direct reactions), target station 1 at the entrance of
Fig. 2. Layout of the TRIlP dual-mode separator. The separator can be used in fragment–separator (target station 1) and in gas-filled (target station 2) mode.
534
G.P. Berg et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 532–535
Table 1 Specifications of the TRIlP dual-mode separator Solid angle Momentum range Resolving power Max. Bq (reaction) Max. Bq (beam)
30 mrad in both transverse directions 2.4% in the dispersive horizontal plane p=dp ¼ 1000 (without gas-filling) 3.0 Tm for reaction products 3.6 Tm (AGOR cyclotron and beamline limit, up to target 2)
3.4. Atom trap A critical stage between the ion beam cooler and the atom trap is the neutralisation of the beam. This topic is presently under investigation. The construction of an atom trap will benefit greatly from the expertise already available at the KVI (see e.g. [7,8]). 3.5. Ion trap
the system is used. The first section is then horizontally dispersive and focusing, allowing the separation by a slit system due to differences in magnetic rigidity between beam and reaction products. The second part can provide an achromatic focus at the end of the separator or may serve as an additional energy-loss separator if a wedge is placed in the focal plane between both parts. In a second mode of operation, gas-filling of the second part is used to efficiently collect heavy-ion products which can be spread out over many atomic charge states (e.g. in fusion–evaporation reactions). In this case, target station 2 in the middle of the separator is used. The first part of the separator then acts as beamline. The main specifications of the system are summarised in Table 1. 3.3. Conversion from high to low energy A gas-catcher system to be placed in the final focus of the TRIlP separator system is being considered for the transformation of the highenergy radioactive-ion beam to a low-energy one. In the gas-catcher system, the high-energy ions are thermalized in a helium- or argon-filled cell. The thermalized ions are extracted at a low-charge state by using electric fields and transported as a low-energy ion beam through an RF multipole into a low-pressure region. Alternate methods, using stopping in and diffusion out of a solid and subsequent ionization, are considered as well. The singly charged beam is then injected into an ion beam cooler: a gas-filled radio-frequency quadrupole (RFQ) structure (see e.g. [6]). Collisions with the gas-atoms cool the beam. Axial segmentation of the RFQ rods allows to trap the ions and release them in short bunches.
The TRIlP facility foresees the installation of a Penning trap for ions of radioactive isotopes, thus creating the possibility for high accuracy experiments on nuclear properties such as e.g. masses and g-factors [9].
4. Outlook The TRIlP facility is expected to be ready for experiments by the end of 2004. In 2001, TRIlP became a managed programme of FOM with funding awarded until 2013 and a mid-term review planned in 2008. It is projected that the TRIlP facility will eventually use 50% of the beam time at the AGOR cyclotron. The facility will be available to outside users via the submission of experiment proposals to the Programme Advisory Committee of KVI.
Acknowledgements This work is funded by the Stichting voor Fundamenteel Onderzoek der Materie (FOM) with financial support from the Nederlandse Organisatie voor Weterschappelijk Onderzoek, the Rijksuniversiteit Groningen (RuG) and in the framework of RTD projects of the European Union (NIPNET, Ion Catcher).
References [1] FOM Programme #48. Available from
G.P. Berg et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 532–535 [2] P. Herczeg, Prog. Part. Nucl. Phys. 46 (2001) 413. [3] I.B. Khriplovich, S.K. Lamoreaux, CP Violation Without Strangeness, Springer-Verlag, Berlin, 1997. [4] V.A. Dzuba, V.V. Flambaum, J.S.M. Ginges, Phys. Rev. A 61 (2000) 062509. [5] H.W. Schreuder (for the AGOR group), in: E. Baron, M. Lieuvin (Eds.), Proceedings of the 15th International Conference on Cyclotrons and their Applications (Caen, France, 1998), IoP, Bristol, 1999.
535
€ yst€ [6] A. Nieminen, J. Huikari, A. Jokinen, J. A o, P. Campbell, E.C.A. Cochrane, Nucl. Instr. and Meth. A 469 (2001) 244. [7] J.W. Turkstra, H.W. Wilschut, D. Meyer, R. Hoekstra, R. Morgenstern, Hyperfine Interact. 127 (2000) 533. [8] J.W. Turkstra, R. Hoekstra, S. Knoop, D. Meyer, R. Morgenstern, R.E. Olson, Phys. Rev. Lett. 87 (2001) 123202. [9] G. Savard, G. Werth, Annu. Rev. Nucl. Part. Sci. 50 (2000) 119.