- Email: [email protected]
A new AMS setup for nuclear astrophysics experiments
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 259 (2007) 669–672 www.elsevier.com/locate/nimb
A new AMS setup for nuclear astrophysics experiments D. Robertson a,*, C. Schmitt a, Ph. Collon a, D. Henderson b, B. Shumard b, L. Lamm a, E. Stech a, T. Butterfield a, P. Engel a, G. Hsu a, G. Konecki a, S. Kurtz a, R. Meharchand c, A. Signoracci a, J. Wittenbach a a
Institute for Structure and Nuclear AstroPhysics, University of Notre Dame, Notre Dame, IN 46556, USA b Physics Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA c Florida State University, Tallahassee, FL 32306, USA Available online 14 February 2007
Abstract The Nuclear Structure Laboratory (NSL) at the University of Notre Dame installed its Browne–Buechner spectrograph in the early 1970s for highly accurate energy measurements of nuclear reactions. Current renovation and upgrading of this spectrograph will enable operation of the magnet in a gas-filled mode, in particular for the study of nuclear reactions with low cross-sections of interest in nuclear astrophysics. One of the principle issues shared by measurements of extremely low abundances in Accelerator Mass Spectrometry (AMS) and nuclear astrophysics is the discrimination between the nuclei of interest and often very intense isobaric background. Recently the AMS technique of the gas-filled magnet has very successfully been used at Argonne National Laboratory (ANL) to overcome this in the study of both environmental noble gas traces (39Ar) and the measurement of cross-sections of interest in stellar nucleosynthesis i.e. the 62Ni(n, c)63Ni reaction. We hope to extend these techniques further to the observations of astrophysically important reactions such as 40Ca(a, c)44Ti and 78Kr(a, c)82Sr. 2007 Elsevier B.V. All rights reserved. PACS: 07.75.+h; 26.30.+k; 97.60.Bw Keywords: AMS; Astrophysics; NSL; Nuclear; Spectrograph
1. Introduction Work is well underway on the development of a new AMS setup at the University of Notre Dame. At present the NSL runs three low-energy accelerators and a low energy implantation system. The current JN, KN and FN model accelerators, rated at 1 MV, 4 MV and 11 MV, respectively, are orientated towards astrophysical research, along with a newly installed 200 kV platform for target implantation and ion source testing. With three independent target areas and individual data acquisition and control systems, the simultaneous use of two accelerators and the 200 kV platform is easily possible,
*
Corresponding author. Tel.: +1 574 631 3206; fax: +1 574 631 5952. E-mail address: [email protected] (D. Robertson).
0168-583X/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.01.261
allowing a wide range of experiments to take place inside one laboratory (Fig. 1). As well as technical assistance inside the laboratory, current astrophysical research at the NSL is highly aided by its close affiliation with JINA (Joint Institute for Nuclear Astrophysics) at Notre Dame, which has laid the foundation for current research under way in such fields as nuclear processes in AGB star evolution, cataclysmic binaries and supernova shock fronts. 2. A new AMS facility The Browne–Buechner spectrograph was first installed in the early 1970s for highly accurate energy measurements of charged particles from nuclear reactions induced by our model FN Tandem Van de Graff electrostatic accelerator
670
D. Robertson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 669–672
Despite good resolution and high accuracy, the spectrograph was abandoned more than ten years ago, as work in the laboratory moved into new fields and techniques. When renovation began in 2003 with the formation of a new AMS group at the NSL, neglect and cannibalism had left the supporting systems in a very poor condition, whereas the magnet system itself was believed to be fully functional. 2.1. Current work
Fig. 1. Layout of ISNAP facility. (1) 11 MV Tandem accelerator; (2) 4 MV Single ended KN accelerator; (3) 1 MV JN accelerator; (4) 200 kV implantation system; (5) target rooms; (6) control room; (7) Browne– Buechner Spectrograph.
[1]. The original design of the spectrograph was orientated around better resolution and higher accuracy than any previously installed 50 cm spectrograph [2]. The design chosen centered around a 90 single dipole magnet with a radius of curvature at 90 (q0) of 100 cm and a maximum field strength of 1.2 T. The magnet gap is in the vertical plane (Fig. 2) originally designed using photographic plate detection at the focal surface. The complete system, weighing 56,000 lbs can rotate around a mean radius of 2.5 m up to an angle of 150. Central rotation is about a stationary scattering chamber fixed at the pivot point.
Renovation began in the autumn of 2003 with the deconstruction of all support systems and associated hardware. Some attempt had been made for reconstruction, but due to the level of deterioration this had become impossible. Corrosion had set in throughout various systems, resulting in the necessity to replace all cooling lines, air lines and vacuum seals. Supporting this was the implementation of a complete new vacuum system including new cryogenic and turbomolecular pumps. Control of the new systems was transferred to a LabVIEW based control system, developed on-site parallel to the overhaul of the electrical system previously found to be outdated. To install a new detection system, the previous focal plane detector and associated hardware had to be removed. Its replacement consists of a position sensitive Parallel Plate Avalanche Counter (PPAC) and Ionisation Chamber (IC) and supporting gas-handling systems, built in collaboration with the detector development group at ANL. Full testing of the PPAC began in the summer of 2005 and concluded in early 2006. This detector is now operational with 3 Torr isobutane gas in continuous flow and a 350 lg/cm2 Mylar entrance window. On-going beam development for the AMS program has seen the first NSL production of 48Ti, 58Fe and 58Ni beams. These along with a 12C beam have been seen on the focal plane of the spectrograph, with an increased transmission of 90%, up from a previous attainable transmission of 45%, made possible through intense beam line alignment. 2.2. Gas-filled implementation
Fig. 2. Schematic drawing of spectrograph [2], here R = Ro = 100 cm.
Late 2006 will see the first implementation of the gasfilled magnet technique at the NSL. Initial testing will utilise a mixed nickel–iron cathode leading to the separation of 58Ni–58Fe, as shown previously in [3]. The interest of this AMS technique for the study of nuclear reactions with low cross-sections stems from its basic property of physically separating the trajectories of ions of different elements. This is due to the behavior of a particle moving in a magnetic field which is drastically different when the field region is in vacuum or filled with low-pressure gas, in our case nitrogen. In the latter case, atomic exchange with the gas medium produces a change in ionic charge state. The discrete charge states coalesce around a trajectory defined by the mean charge state of the ion in the gas resulting in the modified trajectory by the magnetic field (Fig. 3). The
D. Robertson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 669–672
671
Fig. 3. Schematic illustration of the trajectories followed by heavy ions in a magnetic field region: (left) in vacuum; (right) in a gas. In the gas-filled magnetic region, the discrete trajectories coalesce around a trajectory defined by the mean charge state of the ion in the gas [3].
magnetic rigidity (Bq) is now proportional to the momentum (p) divided by the mean charge state ð qÞ: Bq p=q [5]. This technique has already been successfully used with the separation of 39K (1.3 · 106 cps) from the 39Ar (0.004 cps) [5] and 58Fe from 58Ni, amongst others. Further work is planned with the addition of an IC shown in Fig. 4. The combination of IC and PPAC will allow measurements of both the position and energy loss at the focal plane, with the separation of these counters by a secondary Mylar window, the use of different gas pressures in each counter is possible, which creates the necessity for a second independent gas-handling system which will be developed based on the successful testing of the previous design. This new combined system will be operable with at present, two selectable orientations 60 and 90 to the oncoming beam, not solely fixed at an extreme angle as shown for the old focal plane in Fig. 3. With three separate gas-filled sections at this point (Spectrograph, PPAC and IC), the energy loss of the incoming beam is no longer negligible. This significant energy loss would leave certain beams with energies so low that no useful signals could be found. For these types of situation a possible solution is to combine time-of-flight (TOF) measurements with focal plane position measurements. With the inclusion of a smaller PPAC at the entrance to the spectrograph as a start signal, a stop signal can be received from the secondary PPAC, thus negating the need for an IC for some measurements. This technique has successfully been applied down to energies in the range of 0.5 MeV/u as seen in [4,6]. For the versatility that this
Fig. 4. Preliminary PPAC and IC detector set-up.
method provides, both IC and secondary PPAC are under simultaneous development. 3. Future applications In comparison to conventional counting methods, AMS provides a highly powerful counting technique which is totally independent of a radioisotope’s half-life, of great importance in the measurement of astrophysical reactions. Whereas prompt-c counting is successful in most cases, AMS can provide a different approach removing any uncertainty associated with the detailed knowledge of the branching ratios in the gamma cascade or where there is a lack of c’s in the decay scheme. The planned investigation of the following two (a, c) reactions will utilise an inverse-kinematics set-up with the bombardment of a beam of interest on a high purity Hegas cell. The resulting recoil reaction products are implanted in a cooled Cu catcher, which can be chemically etched in a HNO3 solution containing a more stable carrier, further chemical extraction as outlined in [7,8] will result in a usable macroscopic sample for acceleration. The resulting abundance can be measured in the new AMS facility using the gas-filled mode to separate out any contaminating isobars. With known information about the amount of carrier atoms used, the final number of nuclei produced and implanted can be deduced. 3.1.
44
Ti a supernovae remnant probe
With a known half-life of 59.2 y and the measurement of 1.157 MeV light from supernovae remnants [9], 44Ti and its production through the capture reaction 40Ca(a, c)44Ti have become of importance in the study of supernovae nucleosynthesis. This reaction has previously been studied by prompt c-ray spectroscopy at higher energies than those found in stellar environments, due to the low cross-section in the region of astrophysical interest. Using the gas-filled magnet technique to separate 44Ca and 44Ti isobars, we hope to improve initial measurements of this reaction made at ANL and the Weizmann Institute in Israel [10]. A planned improvement on previous experiments, which count 44Ti directly from titanium oxide created out of recoil 44Ti and its catcher, will see the selection of the titanium oxide from SNICS and subsequent separation of
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D. Robertson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 669–672
these isobars. The production of much higher beam intensities from the titanium oxide will allow the probing of a much lower energy range, despite the very small cross-section of reaction. 3.2. P-process nuclei production The abundance of light p-nuclei such as 70Ge, 74Sc, 78Kr and 84Sr depend very strongly on the strength of the (c,a) photodisintegration process feeding the nuclei [11]. However, only the first of these has been measured so far, as experimental data for nuclear reactions involved in p-process networks is extremely scarce forcing a reliance on rate predictions. Data on (a, c) reactions which are needed to derive the rates of the inverse photodisintegrations are especially lacking. It is proposed that using techniques under development for the 40Ca(a, c)44Ti experiment, we also study 78Kr(a, c)82Sr (t1/2 = 25.55 ± 0.15 d). In particular the gas-filled technique is well suited to study the 78 Kr(a, c)82Sr reaction as in the decay of 82Sr there is a lack of gamma rays, preventing the use of the more traditional activation method of detection. Based on Hauser–Feshbach calculations, a 82Sr production of 1 · 105 atoms per leA of a beam and per day is possible. This will not fall below a usable value with the reduction of energy. As we intend to perform our experiments at a bombarding energies of 10 MeV and below, comparing the energy dependence of the cross-section with Hauser Feshbach predictions over a wide energy range. Due to the short half-life of 82Sr, testing and development of a suitable technique for this experiment will use the 86Kr(a, c)90Sr reaction (t1/2 = 28.78 ± 0.4 y). With a much longer half-life, optimization of chemical and separation stages is made easier. 4. Conclusion A new AMS facility for nuclear astrophysics experiments is currently in the final stages of development at the NSL, University of Notre Dame, through the renovation of a 1970s Browne–Buechner spectrograph for use in
AMS. Implementation of new support systems and refurbishment of the magnet are complete and work is in its final stages on a new detector set-up. Pre-existing infrastructure must be used with the new AMS system, resulting on constraints on transmission and usable ion energies. Final testing is due for late 2006 when the system will fully come on line. Acknowledgements We would like to thank the continuing support of Mr. J. Lingle, Mr. B. Mulder and Mr. J. Kaiser (University of Notre Dame) during the development and start-up of the AMS facility at NSL. References [1] J.D. Goss, A.A. Rollefson, C.P. Browne, Design and performance of a new magnetic spectrograph for accurate energy measurements, Nucl. Instr. and Meth. 109 (1973) 13. [2] C.P. Browne, W.W. Buechner, Broad-range magnetic spectrograph, Rev. Sci. Instr. 27 (1956) 11. [3] M. Paul, B.G. Glagola, W. Henning, J.G. Keller, W. Kutshera, Z. Liu, K.E. Rehm, B. Schneck, R. Siemssen, Heavy ion separation with a gas-filled magnetic spectrograph, Nucl. Instr. and Meth. A 277 (1989) 418. [4] K.E. Rehm et al., The use of a gas-filled-magnet in experiments with radioactive ion beams, Nucl. Instr. and Meth. A 370 (1996) 438. [5] Ph. Collon et al., AMS of 39Ar, First application of dating ocean water, Nucl. Instr. and Meth. B 223–224 (2004) 428. [6] F. Scarlassara, B.G. Glagola, W. Kutschera, K.E. Rehm, A.H. Wuosmaa, Nuclear charge separation of low-energy medium-mass ions with a gas-filled magnetic spectrometer, Nucl. Instr. and Meth. A 309 (1991) 485. [7] H. Nassar et al., The 40Ca(a, c)44Ti reaction in the energy regime of supernova nucleosynthesis, Phys. Rev. Lett. 96 (2006) 041102. [8] H. Nassar et al., Study of the supernova nucleosynthesis 40 Ca(a, c)44Ti reaction: progress report, Nucl. Phys. A 758 (2005) 411c. [9] A.F. Iyudin et al., COMPTEL observations of Ti-44 gamma-ray line emission from CAS A, A&A 284 (1994) L1. [10] M. Paul et al., Counting 44Ti Nuclei from the 40Ca(a, c)44Ti Reaction, Nucl. Phys. A 718 (2003) 239c. [11] M. Arnould, S. Goriely, The p-process of stellar nucleosynthesis: astrophysics and nuclear physics status, Phys. Rep. 384 (2003) 1.
Nuclear Instruments and Methods in Physics Research B 259 (2007) 669–672 www.elsevier.com/locate/nimb
A new AMS setup for nuclear astrophysics experiments D. Robertson a,*, C. Schmitt a, Ph. Collon a, D. Henderson b, B. Shumard b, L. Lamm a, E. Stech a, T. Butterfield a, P. Engel a, G. Hsu a, G. Konecki a, S. Kurtz a, R. Meharchand c, A. Signoracci a, J. Wittenbach a a
Institute for Structure and Nuclear AstroPhysics, University of Notre Dame, Notre Dame, IN 46556, USA b Physics Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA c Florida State University, Tallahassee, FL 32306, USA Available online 14 February 2007
Abstract The Nuclear Structure Laboratory (NSL) at the University of Notre Dame installed its Browne–Buechner spectrograph in the early 1970s for highly accurate energy measurements of nuclear reactions. Current renovation and upgrading of this spectrograph will enable operation of the magnet in a gas-filled mode, in particular for the study of nuclear reactions with low cross-sections of interest in nuclear astrophysics. One of the principle issues shared by measurements of extremely low abundances in Accelerator Mass Spectrometry (AMS) and nuclear astrophysics is the discrimination between the nuclei of interest and often very intense isobaric background. Recently the AMS technique of the gas-filled magnet has very successfully been used at Argonne National Laboratory (ANL) to overcome this in the study of both environmental noble gas traces (39Ar) and the measurement of cross-sections of interest in stellar nucleosynthesis i.e. the 62Ni(n, c)63Ni reaction. We hope to extend these techniques further to the observations of astrophysically important reactions such as 40Ca(a, c)44Ti and 78Kr(a, c)82Sr. 2007 Elsevier B.V. All rights reserved. PACS: 07.75.+h; 26.30.+k; 97.60.Bw Keywords: AMS; Astrophysics; NSL; Nuclear; Spectrograph
1. Introduction Work is well underway on the development of a new AMS setup at the University of Notre Dame. At present the NSL runs three low-energy accelerators and a low energy implantation system. The current JN, KN and FN model accelerators, rated at 1 MV, 4 MV and 11 MV, respectively, are orientated towards astrophysical research, along with a newly installed 200 kV platform for target implantation and ion source testing. With three independent target areas and individual data acquisition and control systems, the simultaneous use of two accelerators and the 200 kV platform is easily possible,
*
Corresponding author. Tel.: +1 574 631 3206; fax: +1 574 631 5952. E-mail address: [email protected] (D. Robertson).
0168-583X/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.01.261
allowing a wide range of experiments to take place inside one laboratory (Fig. 1). As well as technical assistance inside the laboratory, current astrophysical research at the NSL is highly aided by its close affiliation with JINA (Joint Institute for Nuclear Astrophysics) at Notre Dame, which has laid the foundation for current research under way in such fields as nuclear processes in AGB star evolution, cataclysmic binaries and supernova shock fronts. 2. A new AMS facility The Browne–Buechner spectrograph was first installed in the early 1970s for highly accurate energy measurements of charged particles from nuclear reactions induced by our model FN Tandem Van de Graff electrostatic accelerator
670
D. Robertson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 669–672
Despite good resolution and high accuracy, the spectrograph was abandoned more than ten years ago, as work in the laboratory moved into new fields and techniques. When renovation began in 2003 with the formation of a new AMS group at the NSL, neglect and cannibalism had left the supporting systems in a very poor condition, whereas the magnet system itself was believed to be fully functional. 2.1. Current work
Fig. 1. Layout of ISNAP facility. (1) 11 MV Tandem accelerator; (2) 4 MV Single ended KN accelerator; (3) 1 MV JN accelerator; (4) 200 kV implantation system; (5) target rooms; (6) control room; (7) Browne– Buechner Spectrograph.
[1]. The original design of the spectrograph was orientated around better resolution and higher accuracy than any previously installed 50 cm spectrograph [2]. The design chosen centered around a 90 single dipole magnet with a radius of curvature at 90 (q0) of 100 cm and a maximum field strength of 1.2 T. The magnet gap is in the vertical plane (Fig. 2) originally designed using photographic plate detection at the focal surface. The complete system, weighing 56,000 lbs can rotate around a mean radius of 2.5 m up to an angle of 150. Central rotation is about a stationary scattering chamber fixed at the pivot point.
Renovation began in the autumn of 2003 with the deconstruction of all support systems and associated hardware. Some attempt had been made for reconstruction, but due to the level of deterioration this had become impossible. Corrosion had set in throughout various systems, resulting in the necessity to replace all cooling lines, air lines and vacuum seals. Supporting this was the implementation of a complete new vacuum system including new cryogenic and turbomolecular pumps. Control of the new systems was transferred to a LabVIEW based control system, developed on-site parallel to the overhaul of the electrical system previously found to be outdated. To install a new detection system, the previous focal plane detector and associated hardware had to be removed. Its replacement consists of a position sensitive Parallel Plate Avalanche Counter (PPAC) and Ionisation Chamber (IC) and supporting gas-handling systems, built in collaboration with the detector development group at ANL. Full testing of the PPAC began in the summer of 2005 and concluded in early 2006. This detector is now operational with 3 Torr isobutane gas in continuous flow and a 350 lg/cm2 Mylar entrance window. On-going beam development for the AMS program has seen the first NSL production of 48Ti, 58Fe and 58Ni beams. These along with a 12C beam have been seen on the focal plane of the spectrograph, with an increased transmission of 90%, up from a previous attainable transmission of 45%, made possible through intense beam line alignment. 2.2. Gas-filled implementation
Fig. 2. Schematic drawing of spectrograph [2], here R = Ro = 100 cm.
Late 2006 will see the first implementation of the gasfilled magnet technique at the NSL. Initial testing will utilise a mixed nickel–iron cathode leading to the separation of 58Ni–58Fe, as shown previously in [3]. The interest of this AMS technique for the study of nuclear reactions with low cross-sections stems from its basic property of physically separating the trajectories of ions of different elements. This is due to the behavior of a particle moving in a magnetic field which is drastically different when the field region is in vacuum or filled with low-pressure gas, in our case nitrogen. In the latter case, atomic exchange with the gas medium produces a change in ionic charge state. The discrete charge states coalesce around a trajectory defined by the mean charge state of the ion in the gas resulting in the modified trajectory by the magnetic field (Fig. 3). The
D. Robertson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 669–672
671
Fig. 3. Schematic illustration of the trajectories followed by heavy ions in a magnetic field region: (left) in vacuum; (right) in a gas. In the gas-filled magnetic region, the discrete trajectories coalesce around a trajectory defined by the mean charge state of the ion in the gas [3].
magnetic rigidity (Bq) is now proportional to the momentum (p) divided by the mean charge state ð qÞ: Bq p=q [5]. This technique has already been successfully used with the separation of 39K (1.3 · 106 cps) from the 39Ar (0.004 cps) [5] and 58Fe from 58Ni, amongst others. Further work is planned with the addition of an IC shown in Fig. 4. The combination of IC and PPAC will allow measurements of both the position and energy loss at the focal plane, with the separation of these counters by a secondary Mylar window, the use of different gas pressures in each counter is possible, which creates the necessity for a second independent gas-handling system which will be developed based on the successful testing of the previous design. This new combined system will be operable with at present, two selectable orientations 60 and 90 to the oncoming beam, not solely fixed at an extreme angle as shown for the old focal plane in Fig. 3. With three separate gas-filled sections at this point (Spectrograph, PPAC and IC), the energy loss of the incoming beam is no longer negligible. This significant energy loss would leave certain beams with energies so low that no useful signals could be found. For these types of situation a possible solution is to combine time-of-flight (TOF) measurements with focal plane position measurements. With the inclusion of a smaller PPAC at the entrance to the spectrograph as a start signal, a stop signal can be received from the secondary PPAC, thus negating the need for an IC for some measurements. This technique has successfully been applied down to energies in the range of 0.5 MeV/u as seen in [4,6]. For the versatility that this
Fig. 4. Preliminary PPAC and IC detector set-up.
method provides, both IC and secondary PPAC are under simultaneous development. 3. Future applications In comparison to conventional counting methods, AMS provides a highly powerful counting technique which is totally independent of a radioisotope’s half-life, of great importance in the measurement of astrophysical reactions. Whereas prompt-c counting is successful in most cases, AMS can provide a different approach removing any uncertainty associated with the detailed knowledge of the branching ratios in the gamma cascade or where there is a lack of c’s in the decay scheme. The planned investigation of the following two (a, c) reactions will utilise an inverse-kinematics set-up with the bombardment of a beam of interest on a high purity Hegas cell. The resulting recoil reaction products are implanted in a cooled Cu catcher, which can be chemically etched in a HNO3 solution containing a more stable carrier, further chemical extraction as outlined in [7,8] will result in a usable macroscopic sample for acceleration. The resulting abundance can be measured in the new AMS facility using the gas-filled mode to separate out any contaminating isobars. With known information about the amount of carrier atoms used, the final number of nuclei produced and implanted can be deduced. 3.1.
44
Ti a supernovae remnant probe
With a known half-life of 59.2 y and the measurement of 1.157 MeV light from supernovae remnants [9], 44Ti and its production through the capture reaction 40Ca(a, c)44Ti have become of importance in the study of supernovae nucleosynthesis. This reaction has previously been studied by prompt c-ray spectroscopy at higher energies than those found in stellar environments, due to the low cross-section in the region of astrophysical interest. Using the gas-filled magnet technique to separate 44Ca and 44Ti isobars, we hope to improve initial measurements of this reaction made at ANL and the Weizmann Institute in Israel [10]. A planned improvement on previous experiments, which count 44Ti directly from titanium oxide created out of recoil 44Ti and its catcher, will see the selection of the titanium oxide from SNICS and subsequent separation of
672
D. Robertson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 669–672
these isobars. The production of much higher beam intensities from the titanium oxide will allow the probing of a much lower energy range, despite the very small cross-section of reaction. 3.2. P-process nuclei production The abundance of light p-nuclei such as 70Ge, 74Sc, 78Kr and 84Sr depend very strongly on the strength of the (c,a) photodisintegration process feeding the nuclei [11]. However, only the first of these has been measured so far, as experimental data for nuclear reactions involved in p-process networks is extremely scarce forcing a reliance on rate predictions. Data on (a, c) reactions which are needed to derive the rates of the inverse photodisintegrations are especially lacking. It is proposed that using techniques under development for the 40Ca(a, c)44Ti experiment, we also study 78Kr(a, c)82Sr (t1/2 = 25.55 ± 0.15 d). In particular the gas-filled technique is well suited to study the 78 Kr(a, c)82Sr reaction as in the decay of 82Sr there is a lack of gamma rays, preventing the use of the more traditional activation method of detection. Based on Hauser–Feshbach calculations, a 82Sr production of 1 · 105 atoms per leA of a beam and per day is possible. This will not fall below a usable value with the reduction of energy. As we intend to perform our experiments at a bombarding energies of 10 MeV and below, comparing the energy dependence of the cross-section with Hauser Feshbach predictions over a wide energy range. Due to the short half-life of 82Sr, testing and development of a suitable technique for this experiment will use the 86Kr(a, c)90Sr reaction (t1/2 = 28.78 ± 0.4 y). With a much longer half-life, optimization of chemical and separation stages is made easier. 4. Conclusion A new AMS facility for nuclear astrophysics experiments is currently in the final stages of development at the NSL, University of Notre Dame, through the renovation of a 1970s Browne–Buechner spectrograph for use in
AMS. Implementation of new support systems and refurbishment of the magnet are complete and work is in its final stages on a new detector set-up. Pre-existing infrastructure must be used with the new AMS system, resulting on constraints on transmission and usable ion energies. Final testing is due for late 2006 when the system will fully come on line. Acknowledgements We would like to thank the continuing support of Mr. J. Lingle, Mr. B. Mulder and Mr. J. Kaiser (University of Notre Dame) during the development and start-up of the AMS facility at NSL. References [1] J.D. Goss, A.A. Rollefson, C.P. Browne, Design and performance of a new magnetic spectrograph for accurate energy measurements, Nucl. Instr. and Meth. 109 (1973) 13. [2] C.P. Browne, W.W. Buechner, Broad-range magnetic spectrograph, Rev. Sci. Instr. 27 (1956) 11. [3] M. Paul, B.G. Glagola, W. Henning, J.G. Keller, W. Kutshera, Z. Liu, K.E. Rehm, B. Schneck, R. Siemssen, Heavy ion separation with a gas-filled magnetic spectrograph, Nucl. Instr. and Meth. A 277 (1989) 418. [4] K.E. Rehm et al., The use of a gas-filled-magnet in experiments with radioactive ion beams, Nucl. Instr. and Meth. A 370 (1996) 438. [5] Ph. Collon et al., AMS of 39Ar, First application of dating ocean water, Nucl. Instr. and Meth. B 223–224 (2004) 428. [6] F. Scarlassara, B.G. Glagola, W. Kutschera, K.E. Rehm, A.H. Wuosmaa, Nuclear charge separation of low-energy medium-mass ions with a gas-filled magnetic spectrometer, Nucl. Instr. and Meth. A 309 (1991) 485. [7] H. Nassar et al., The 40Ca(a, c)44Ti reaction in the energy regime of supernova nucleosynthesis, Phys. Rev. Lett. 96 (2006) 041102. [8] H. Nassar et al., Study of the supernova nucleosynthesis 40 Ca(a, c)44Ti reaction: progress report, Nucl. Phys. A 758 (2005) 411c. [9] A.F. Iyudin et al., COMPTEL observations of Ti-44 gamma-ray line emission from CAS A, A&A 284 (1994) L1. [10] M. Paul et al., Counting 44Ti Nuclei from the 40Ca(a, c)44Ti Reaction, Nucl. Phys. A 718 (2003) 239c. [11] M. Arnould, S. Goriely, The p-process of stellar nucleosynthesis: astrophysics and nuclear physics status, Phys. Rep. 384 (2003) 1.