- Email: [email protected]
Atomic physics measurements using an ECR ion source located on a 350 kV high-voltage platform
Nuclear Instruments and Methods North-Holland. Amsterdam
in Physics
Research
B40/41
(1989) 9-12
ATOMIC PHYSICS MEASUREMENTS USING AN ECR ION SOURCE ON A 350 kV HIGH-VOLTAGE PLATFORM R.W. DUNFORD, H.G. BERRY, and B.J. ZABRANSKY
C.J. LIU, M. HASS
Phvsics Dicision, Argonne National Laboratory
Argonne,
*, R.C. PARDO,
LOCATED
M.L.A.
RAPHAELIAN
Illinois 60439 * *, USA
We report on a new atomic physics facility at the Argonne PI1 ECR ion source which was built for the Uranium Upgrade of the ATLAS heavy-ion accelerator. An important feature of our ECR ion source is that it is on a high-voltage platform which provides beam energies of up to 35Oq keV, where 4 is the charge of the ion. We discuss the experimental program in progress at this ion source which includes measurements of state-selective electron capture cross sections. photon and electron spectroscopy. studies of quasi-molecular collisions, and polarization studies using an optically pumped Na target.
1. Introduction The electron cyclotron resonance (ECR) ion source is capable of producing intense beams of moderately charged ions, for example, microampere currents of one-electron oxygen ions can be obtained routinely. Such beams are ideal for studying the atomic physics of multiply-charged ions and there are now several groups using these sources for studies of atomic collisions and spectroscopy. Before the advent of advanced ion sources such as the ECR source and the electron beam ion source (EBIS). production of highly-charged ions required the use of heavy-ion accelerators. The beam time and beam currents available at accelerator laboratories make it difficult to carry out low statistics experiments such as state-selective electron capture [l]. Another aspect of atomic physics experiments using advanced ion sources is that they produce slow, highlycharged ions and slow ions are required for many atomic physics experiments. Other means of obtaining ions include the beams of slow, highly-charged accel-decel procedure [2] and recoil ion sources (SIRS) [3]. In the accel-decel procedure, highly-charged ions are produced by accelerating a beam of ions to high energy, stripping to the desired charge state, and then decelerating to the desired final energy. This technique is, in principle, capable of producing highly-charged ions with any velocity, however, in practice, the final velocity available is dictated by the limitations of available heavy-ion accelerators, which are designed for acceleration and are not generally optimized for deceler-
* Permanent
address: The Kleizmann Institute of Science. Rehovet, Israel. * * Work supported by the US Department of Energy. Office of Basic Energy Sciences, under Contract W-31-109-ENG38.
0168-583X/89/$03.50 0 Elsevier Science Publishers (North-Holland Physics Publishing Division)
B.V.
ation. In the recoil ion technique. slow highly-charged ions are produced by bombarding a gas target with a fast heavy-ion beam and then extracting the slow recoil ions from the gas. In the past year, we have set up an atomic physics facility at the Argonne PI1 ECR ion source which has the unique feature that it is on a 350 kV high-voltage platform. The combination of an advanced ion source with a high-voltage platform. provides beams of highlycharged ions in an energy regime that has not been readily available until now. Recoil, ECR and electron beam ion sources provide low-energy beams (beam energy less than about 10 keV/amu) and accelerators provide high-energy beams but the intermediate energy regime (lo-500 keV/amu) is not well covered at the present time. This is unfortunate because an understanding of ion-atom collisions at intermediate energy has important practical applications in the fields of astrophysics and plasma physics. Other programs such as the study of quasimolecular interference effects and atomic structure and lifetimes would also benefit from the use of ion beams at intermediate energies. The availability of such beams will soon improve because, in addition to the Argonne ECR ion source facility, this energy regime will also be covered by the cryogenic EBIS [4] nearing completion at Kansas State University which will also be located on a high-voltage platform. There are also plans at the Amsterdam-Groningen ECR facility to couple an ECR source with a small accelerator in order to obtain intermediate energy beams.
2. Description
of facility
The Argonne PI1 ECR ion source is one of the key components of the upgrade of the ATLAS heavy-ion 1. ATOMIC PHYSICS
10
R. W. Dunford et al. / Atomic physics measurements
accelerator. The source will provide multiply-charged ions to be accelerated by a new injector linac section which will accelerate the ions to the velocity needed for the existing ATLAS linac. The source has two stages and is operated at 10 GHz. Details of its design are given in another paper being presented at this meeting. An important feature is that good access is provided in the second stage of the source so that ovens or probes needed to produce metallic beams can be easily incorporated. It is intended that beams of any element in the periodic chart up to uranium will be available from this source. In addition to the high-voltage platform, another feature of the Argonne facility is that the beam can be bunched. This feature, which is required for use with the linac will also be useful in some atomic physics experiments. After extraction, ions are focussed by an electrostatic lens and an einzel lens, analyzed in a 90” magnet, accelerated and directed to the injector linac. A bending magnet located after the accelerating tube is used to direct the beam into the atomic physics beamline when the source is not being used for ATLAS. For operation with the high-voltage platform a magnetic quadrupole doublet is used to focus the beam on the target area, while for low energy beams, we use two einzel lenses to transport the beam to the target area. For the first einzel lens, we use the accelerating tube, applying a voltage to one of the six sections while grounding the remaining sections. The use of the accelerating tube in this way works quite well and is an efficient use of available components. We also have three sets of fourjaw slits to collimate the beam. With the slits fully opened, the beam spot size in our target area is about 1 cm in diameter and the beam divergence is about 10 mrad. The source is currently available on about a 50% basis for atomic physics with the other 50% being devoted to source development. When the injector LINAC is completed and begins to be used for ATLAS, the availability of the source for atomic physics will be reduced to periods when ATLAS is shut down. In order to obtain maximum use of the source in the first year of operation, we set up a temporary beam line immediately after the accelerating tube which was used for atomic physics experiments through the first of September 1988. This fall we moved the temporary beam line to a permanent location in a recently completed building addition which was built to provide space needed for the new injector for ATLAS.
of multiply-charged ions were directed on to a gas target which consisted of a 38 mm cube, with a 9 mm diameter hole for the beam to enter and a 1.6 mm by 17.5 mm slot in the side to allow photons from the beam to be observed by a 2.2 m grazing incidence monochromator (McPherson model 247). A channeltron was used for detection of the radiation. The grazing angle of the spectrometer was set at 86” and photons were observed at 90 ’ to the beam axis. Two gratings of 600 lines/mm and 300 lines/mm were used. The 600 lines/mm grating had a peak efficiency at 127 A and provided coverage for wavelengths between 100 A and 250 A while the 300 lines/mm grating had a peak efficiency at 254 A and provided coverage from 200 A to 600 A. Typical data for a beam of 06+ incident on a helium gas target are shown in fig. 1 for two different beam energies. The figure shows the spectra of radiation emitted by the ion after capturing an electron into the lithium-like states of Os+. For this collision system, capture is mainly into n = 3 but there is also some capture into n = 4. Note that at low energy, lines originating from the 3s, 3p and 3d states are of comparable intensity while at higher energy capture into 3d dominates. Also note that the capture into the n = 4 states is relatively more important at higher energy. By measuring the number of photons detected for a fixed quantity of charge collected at the Faraday cup and for a fixed target density, we measured the relative cross sections as a function of energy in the energy range 2-105 keV/amu for all the strong lines in the 100 to 600 A wavelength region for collisions of 06+ with
0
3. Experimental program The first experiments to be done with the temporary beamline at the ECR source were measurements of state selective electron capture in ion-atom collisions. Beams
50
100 CHANIdEL
150
NUMBER
Fig. 1. Spectra taken with the grazing incidence spectrometer with a 600 l/mm grating. The accumulated Faraday cup charge was 6 PC. The upper spectrum was taken at a beam energy of 2.25 keV/amu and the lower spectrum was taken at a beam energy of 41.6 keV/amu.
R. W. Dunford et al. / Atomic physics measurements
helium. We then normalized to the data of Dijkkamp et al. [5] at a beam energy of 4.5 keV/amu. and after applying corrections for the transit time effect, Doppler effect and alignment [6], line emission cross sections were obtained. These data were then compared with the calculations of Fritch and Lin [7]. For electron capture into specific subshells of the n = 3 and n = 4 levels we converted their cross sections into line emission cross sections using calculated branching ratios [8]. Reasonable agreement was obtained particularly for the transitions from n = 3. One important observation is that at energies above 40 keV/amu we observed a line at 356 A identified as the 3d-5f transition in 05+. This is interesting because the calculations of Fritch and Lin did not consider the n = 5 levels. It is clear that neglect of this level is not appropriate at higher energies where the capture into n = 5 becomes significant. We plan to continue measurements of state-selective electron capture cross sections in ion-atom collisions concentrating on bare, one-electron, and two-electron projectiles of carbon, nitrogen and oxygen incident on helium and molecular hydrogen. We have already obtained some data for collisions of 06+ on H, and O’+ on He and HZ. We also plan to develop a dissociated hydrogen target in the coming year and study collisions with atomic hydrogen. Collisions of multiply-charged ions with atomic hydrogen targets are of interest theoretically and they are also important in support of fusion energy research. The interest of the fusion community stems from the fact that photon emission following electron-capture collisions between neutral beams of atomic hydrogen and multiply-charged ions in the plasma are used to determine impurity concentrations and measure ion temperature in tokamaks. Knowledge of the line emission cross sections for these collisions is important in the interpretation of the tokamak data. In addition to the grazing incidence spectrometer, we also have available a 1 m normal incidence spectrometer (McPherson Model 225) and a visible region spectrometer. An important improvement project planned for the next year is to build position-sensitive detectors for the spectrometers so that data may be taken simultaneously over a large wavelength range thus greatly improving the statistical accuracy and allowing the study of weak lines. The position-sensitive detector will also provide data of considerably better resolution than our present data, in which relatively wide slits were used in order to improve the count rate. Another experimental program in progress at the Argonne ECR ion source involves the development of a sodium beam target. The target is part of a project to obtain electron-polarized multiply-charged ions for use in fundamental atomic physics measurements. The sodium beam will be polarized by optical pumping and then the polarization will be transferred to the ions by charge exchange. At the present time, we are using the
I 3o0
11 I
’
/
I
N5++Na
!
DETECTOR
CHANNELTRON
100
0
Fig. 2. Spectrum taken with the normal incidence coupled with a channeltron detector for N5+-Na
spectrometer collisions at
an ion energy of 4.3 keV/amu.
sodium target to study state-selective electron capture in collisions of multiply-charged ions with sodium. Typical spectra for collisions of N5+ with sodium atoms are shown in figs. 2 and 3 which were taken with the normal incidence spectrometer. For fig. 2, the beam energy was set at 4.3 keV/amu and a channeltron detector which is sensitive to radiation in the far ultraviolet was used. These data show a prominent line originating from n = 5 and a weak line originating from n = 6. The data of fig. 3 were taken with an EMR 541G-08 photomultiplier tube which is sensitive to
200
400
600 CHAPJNEL
6OC
IObO
I2k
NUM6EQ
Fig. 3. Spectrum taken with the normal incidence spectrometer coupled with a photomultiplier detector for NSf-Na collisions at an ion energy of 3.6 keV/amu. I. ATOMIC PHYSICS
12
R. W. Dunford et ul. / Atonuc phwics measurements IBOOr
I
N
5+d
.495.4fi
IO001 I
,
I
,
,
r
05+-
Na
-1
No
3p2P0-5deD
’ 2
’
’
’
4
5
c
3 ENERGY
J
6
(keV/amu)
Fig. 4. Dependence of the count rate on ion energy for the 495.3 A line (3p-5d transition in lg4+ ) in N5+-Na collisions. The dotted
Id00
line is to guide the eye.
CHANNEL
longer wavelength radiation. In figs. 4 and 5 we show the dependence of the count rate on ion energy for the 495 and the 748 A lines produced in collisions of N5+ on sodium. In fig. 6 we show a spectrum obtained from collisions of OS+ with sodium. For these data. the channeltron detector was used and the beam energy was set at 3.1 keV/amu. The Argonne ECR ion source and high-voltage platform has also been used to study quasi-molecular X-ray and Auger processes in collisions of hydrogen-like neon ions on a neon gas target. This work was done in collaboration with Kansas State University and The University of Frankfurt 191. In the first experimental run, the high-voltage platform was operated at 280 keV so that the beam energy on target was 2.5 MeV. Electron spectrometers measured the energy of electrons coming from the target in the range of 100 to 1400 eV at laboratory emission angles of 45 o and 135 O. A Si(Li)
i 1600
c
1’
/’ ,’ ,,*_-___x’
‘zoo2
3 ENERGY
4
5
6
(keV/amu)
Fig. 5. Dependence of the count rate on ion energy for the 748.3 A line (3d-4f transition in N4+ ) in NSt-Na collisions. The line is to guide the eye.
2doo
30bo
NUMBER
Fig. 6. Spectrum taken with the normal incidence coupled with a channeltron detector for 05’-Na an ion energy of 3.1 keV/amu.
spectrometer collisions at
detector was also used to study the X-ray emission from the target. The impact parameter was measured in coincidence with X-ray and Auger emission by detecting the scattered particle in a position-sensitive avalanche detector.
References [ll R.K. Yanev and H. Winter, Phys. Rep. 117 (1985) 265. PI P. Thieberger, J. Barrette, B.M. Johnson, K.W. Jones. M. Meron and H.E. Wenger, IEEE Trans. Nucl. Sci.. NS-30 (1983) 1413: H. Ingwersen. E. Jaeschke. and R. Repnow, Nucl. Instr. and Meth. 215 (1983) 55; R.D. Deslattes. R. Schuch and E. Justiniano, Phys. Rev. A32 (1985) 1911. C.L. Cocke, T.J. Gray, R. Dubois. C. Can. [31 E. Justiniano, W. Waggoner, R. Schuch, H. Schmidt-Backing and H. Ingwersen, Phys. Rev. A29 (1984) 1088. in: Proc. Workshop on Opportunities for 141 P. Richard, Atomic Physics Using Slow. Highly-Charged Ions. Argonne National Laboratory. (Jan. 12-13. 1987) eds. H.G. Berry, R. Dunford. D. Gemmell. and E. Kanter, p. 197. D. Ciric, E. Vlieg, A. De Boer and F.J. de (51 D. Dijkkamp. Heer. J. Phys. B18 (1985) 4763. Muller and F.J. de Heer, Physica 48 (1970) [61 L. Wolterbeek 345. 171 W. Fritch and C.D. Lin, J. Phys. B19 (1986) 2683. [El A. Lindgrd and SE. Nielsen, At. Data Nucl. Data Tables 19 (1977) 533. with S. Hagmann. R. Koch. A. [91 Work done in collaboration Gonzalez, B. Krassig, T. Quinteros, H. Schmidt-B&king, A. Skutlartz.
in Physics
Research
B40/41
(1989) 9-12
ATOMIC PHYSICS MEASUREMENTS USING AN ECR ION SOURCE ON A 350 kV HIGH-VOLTAGE PLATFORM R.W. DUNFORD, H.G. BERRY, and B.J. ZABRANSKY
C.J. LIU, M. HASS
Phvsics Dicision, Argonne National Laboratory
Argonne,
*, R.C. PARDO,
LOCATED
M.L.A.
RAPHAELIAN
Illinois 60439 * *, USA
We report on a new atomic physics facility at the Argonne PI1 ECR ion source which was built for the Uranium Upgrade of the ATLAS heavy-ion accelerator. An important feature of our ECR ion source is that it is on a high-voltage platform which provides beam energies of up to 35Oq keV, where 4 is the charge of the ion. We discuss the experimental program in progress at this ion source which includes measurements of state-selective electron capture cross sections. photon and electron spectroscopy. studies of quasi-molecular collisions, and polarization studies using an optically pumped Na target.
1. Introduction The electron cyclotron resonance (ECR) ion source is capable of producing intense beams of moderately charged ions, for example, microampere currents of one-electron oxygen ions can be obtained routinely. Such beams are ideal for studying the atomic physics of multiply-charged ions and there are now several groups using these sources for studies of atomic collisions and spectroscopy. Before the advent of advanced ion sources such as the ECR source and the electron beam ion source (EBIS). production of highly-charged ions required the use of heavy-ion accelerators. The beam time and beam currents available at accelerator laboratories make it difficult to carry out low statistics experiments such as state-selective electron capture [l]. Another aspect of atomic physics experiments using advanced ion sources is that they produce slow, highlycharged ions and slow ions are required for many atomic physics experiments. Other means of obtaining ions include the beams of slow, highly-charged accel-decel procedure [2] and recoil ion sources (SIRS) [3]. In the accel-decel procedure, highly-charged ions are produced by accelerating a beam of ions to high energy, stripping to the desired charge state, and then decelerating to the desired final energy. This technique is, in principle, capable of producing highly-charged ions with any velocity, however, in practice, the final velocity available is dictated by the limitations of available heavy-ion accelerators, which are designed for acceleration and are not generally optimized for deceler-
* Permanent
address: The Kleizmann Institute of Science. Rehovet, Israel. * * Work supported by the US Department of Energy. Office of Basic Energy Sciences, under Contract W-31-109-ENG38.
0168-583X/89/$03.50 0 Elsevier Science Publishers (North-Holland Physics Publishing Division)
B.V.
ation. In the recoil ion technique. slow highly-charged ions are produced by bombarding a gas target with a fast heavy-ion beam and then extracting the slow recoil ions from the gas. In the past year, we have set up an atomic physics facility at the Argonne PI1 ECR ion source which has the unique feature that it is on a 350 kV high-voltage platform. The combination of an advanced ion source with a high-voltage platform. provides beams of highlycharged ions in an energy regime that has not been readily available until now. Recoil, ECR and electron beam ion sources provide low-energy beams (beam energy less than about 10 keV/amu) and accelerators provide high-energy beams but the intermediate energy regime (lo-500 keV/amu) is not well covered at the present time. This is unfortunate because an understanding of ion-atom collisions at intermediate energy has important practical applications in the fields of astrophysics and plasma physics. Other programs such as the study of quasimolecular interference effects and atomic structure and lifetimes would also benefit from the use of ion beams at intermediate energies. The availability of such beams will soon improve because, in addition to the Argonne ECR ion source facility, this energy regime will also be covered by the cryogenic EBIS [4] nearing completion at Kansas State University which will also be located on a high-voltage platform. There are also plans at the Amsterdam-Groningen ECR facility to couple an ECR source with a small accelerator in order to obtain intermediate energy beams.
2. Description
of facility
The Argonne PI1 ECR ion source is one of the key components of the upgrade of the ATLAS heavy-ion 1. ATOMIC PHYSICS
10
R. W. Dunford et al. / Atomic physics measurements
accelerator. The source will provide multiply-charged ions to be accelerated by a new injector linac section which will accelerate the ions to the velocity needed for the existing ATLAS linac. The source has two stages and is operated at 10 GHz. Details of its design are given in another paper being presented at this meeting. An important feature is that good access is provided in the second stage of the source so that ovens or probes needed to produce metallic beams can be easily incorporated. It is intended that beams of any element in the periodic chart up to uranium will be available from this source. In addition to the high-voltage platform, another feature of the Argonne facility is that the beam can be bunched. This feature, which is required for use with the linac will also be useful in some atomic physics experiments. After extraction, ions are focussed by an electrostatic lens and an einzel lens, analyzed in a 90” magnet, accelerated and directed to the injector linac. A bending magnet located after the accelerating tube is used to direct the beam into the atomic physics beamline when the source is not being used for ATLAS. For operation with the high-voltage platform a magnetic quadrupole doublet is used to focus the beam on the target area, while for low energy beams, we use two einzel lenses to transport the beam to the target area. For the first einzel lens, we use the accelerating tube, applying a voltage to one of the six sections while grounding the remaining sections. The use of the accelerating tube in this way works quite well and is an efficient use of available components. We also have three sets of fourjaw slits to collimate the beam. With the slits fully opened, the beam spot size in our target area is about 1 cm in diameter and the beam divergence is about 10 mrad. The source is currently available on about a 50% basis for atomic physics with the other 50% being devoted to source development. When the injector LINAC is completed and begins to be used for ATLAS, the availability of the source for atomic physics will be reduced to periods when ATLAS is shut down. In order to obtain maximum use of the source in the first year of operation, we set up a temporary beam line immediately after the accelerating tube which was used for atomic physics experiments through the first of September 1988. This fall we moved the temporary beam line to a permanent location in a recently completed building addition which was built to provide space needed for the new injector for ATLAS.
of multiply-charged ions were directed on to a gas target which consisted of a 38 mm cube, with a 9 mm diameter hole for the beam to enter and a 1.6 mm by 17.5 mm slot in the side to allow photons from the beam to be observed by a 2.2 m grazing incidence monochromator (McPherson model 247). A channeltron was used for detection of the radiation. The grazing angle of the spectrometer was set at 86” and photons were observed at 90 ’ to the beam axis. Two gratings of 600 lines/mm and 300 lines/mm were used. The 600 lines/mm grating had a peak efficiency at 127 A and provided coverage for wavelengths between 100 A and 250 A while the 300 lines/mm grating had a peak efficiency at 254 A and provided coverage from 200 A to 600 A. Typical data for a beam of 06+ incident on a helium gas target are shown in fig. 1 for two different beam energies. The figure shows the spectra of radiation emitted by the ion after capturing an electron into the lithium-like states of Os+. For this collision system, capture is mainly into n = 3 but there is also some capture into n = 4. Note that at low energy, lines originating from the 3s, 3p and 3d states are of comparable intensity while at higher energy capture into 3d dominates. Also note that the capture into the n = 4 states is relatively more important at higher energy. By measuring the number of photons detected for a fixed quantity of charge collected at the Faraday cup and for a fixed target density, we measured the relative cross sections as a function of energy in the energy range 2-105 keV/amu for all the strong lines in the 100 to 600 A wavelength region for collisions of 06+ with
0
3. Experimental program The first experiments to be done with the temporary beamline at the ECR source were measurements of state selective electron capture in ion-atom collisions. Beams
50
100 CHANIdEL
150
NUMBER
Fig. 1. Spectra taken with the grazing incidence spectrometer with a 600 l/mm grating. The accumulated Faraday cup charge was 6 PC. The upper spectrum was taken at a beam energy of 2.25 keV/amu and the lower spectrum was taken at a beam energy of 41.6 keV/amu.
R. W. Dunford et al. / Atomic physics measurements
helium. We then normalized to the data of Dijkkamp et al. [5] at a beam energy of 4.5 keV/amu. and after applying corrections for the transit time effect, Doppler effect and alignment [6], line emission cross sections were obtained. These data were then compared with the calculations of Fritch and Lin [7]. For electron capture into specific subshells of the n = 3 and n = 4 levels we converted their cross sections into line emission cross sections using calculated branching ratios [8]. Reasonable agreement was obtained particularly for the transitions from n = 3. One important observation is that at energies above 40 keV/amu we observed a line at 356 A identified as the 3d-5f transition in 05+. This is interesting because the calculations of Fritch and Lin did not consider the n = 5 levels. It is clear that neglect of this level is not appropriate at higher energies where the capture into n = 5 becomes significant. We plan to continue measurements of state-selective electron capture cross sections in ion-atom collisions concentrating on bare, one-electron, and two-electron projectiles of carbon, nitrogen and oxygen incident on helium and molecular hydrogen. We have already obtained some data for collisions of 06+ on H, and O’+ on He and HZ. We also plan to develop a dissociated hydrogen target in the coming year and study collisions with atomic hydrogen. Collisions of multiply-charged ions with atomic hydrogen targets are of interest theoretically and they are also important in support of fusion energy research. The interest of the fusion community stems from the fact that photon emission following electron-capture collisions between neutral beams of atomic hydrogen and multiply-charged ions in the plasma are used to determine impurity concentrations and measure ion temperature in tokamaks. Knowledge of the line emission cross sections for these collisions is important in the interpretation of the tokamak data. In addition to the grazing incidence spectrometer, we also have available a 1 m normal incidence spectrometer (McPherson Model 225) and a visible region spectrometer. An important improvement project planned for the next year is to build position-sensitive detectors for the spectrometers so that data may be taken simultaneously over a large wavelength range thus greatly improving the statistical accuracy and allowing the study of weak lines. The position-sensitive detector will also provide data of considerably better resolution than our present data, in which relatively wide slits were used in order to improve the count rate. Another experimental program in progress at the Argonne ECR ion source involves the development of a sodium beam target. The target is part of a project to obtain electron-polarized multiply-charged ions for use in fundamental atomic physics measurements. The sodium beam will be polarized by optical pumping and then the polarization will be transferred to the ions by charge exchange. At the present time, we are using the
I 3o0
11 I
’
/
I
N5++Na
!
DETECTOR
CHANNELTRON
100
0
Fig. 2. Spectrum taken with the normal incidence coupled with a channeltron detector for N5+-Na
spectrometer collisions at
an ion energy of 4.3 keV/amu.
sodium target to study state-selective electron capture in collisions of multiply-charged ions with sodium. Typical spectra for collisions of N5+ with sodium atoms are shown in figs. 2 and 3 which were taken with the normal incidence spectrometer. For fig. 2, the beam energy was set at 4.3 keV/amu and a channeltron detector which is sensitive to radiation in the far ultraviolet was used. These data show a prominent line originating from n = 5 and a weak line originating from n = 6. The data of fig. 3 were taken with an EMR 541G-08 photomultiplier tube which is sensitive to
200
400
600 CHAPJNEL
6OC
IObO
I2k
NUM6EQ
Fig. 3. Spectrum taken with the normal incidence spectrometer coupled with a photomultiplier detector for NSf-Na collisions at an ion energy of 3.6 keV/amu. I. ATOMIC PHYSICS
12
R. W. Dunford et ul. / Atonuc phwics measurements IBOOr
I
N
5+d
.495.4fi
IO001 I
,
I
,
,
r
05+-
Na
-1
No
3p2P0-5deD
’ 2
’
’
’
4
5
c
3 ENERGY
J
6
(keV/amu)
Fig. 4. Dependence of the count rate on ion energy for the 495.3 A line (3p-5d transition in lg4+ ) in N5+-Na collisions. The dotted
Id00
line is to guide the eye.
CHANNEL
longer wavelength radiation. In figs. 4 and 5 we show the dependence of the count rate on ion energy for the 495 and the 748 A lines produced in collisions of N5+ on sodium. In fig. 6 we show a spectrum obtained from collisions of OS+ with sodium. For these data. the channeltron detector was used and the beam energy was set at 3.1 keV/amu. The Argonne ECR ion source and high-voltage platform has also been used to study quasi-molecular X-ray and Auger processes in collisions of hydrogen-like neon ions on a neon gas target. This work was done in collaboration with Kansas State University and The University of Frankfurt 191. In the first experimental run, the high-voltage platform was operated at 280 keV so that the beam energy on target was 2.5 MeV. Electron spectrometers measured the energy of electrons coming from the target in the range of 100 to 1400 eV at laboratory emission angles of 45 o and 135 O. A Si(Li)
i 1600
c
1’
/’ ,’ ,,*_-___x’
‘zoo2
3 ENERGY
4
5
6
(keV/amu)
Fig. 5. Dependence of the count rate on ion energy for the 748.3 A line (3d-4f transition in N4+ ) in NSt-Na collisions. The line is to guide the eye.
2doo
30bo
NUMBER
Fig. 6. Spectrum taken with the normal incidence coupled with a channeltron detector for 05’-Na an ion energy of 3.1 keV/amu.
spectrometer collisions at
detector was also used to study the X-ray emission from the target. The impact parameter was measured in coincidence with X-ray and Auger emission by detecting the scattered particle in a position-sensitive avalanche detector.
References [ll R.K. Yanev and H. Winter, Phys. Rep. 117 (1985) 265. PI P. Thieberger, J. Barrette, B.M. Johnson, K.W. Jones. M. Meron and H.E. Wenger, IEEE Trans. Nucl. Sci.. NS-30 (1983) 1413: H. Ingwersen. E. Jaeschke. and R. Repnow, Nucl. Instr. and Meth. 215 (1983) 55; R.D. Deslattes. R. Schuch and E. Justiniano, Phys. Rev. A32 (1985) 1911. C.L. Cocke, T.J. Gray, R. Dubois. C. Can. [31 E. Justiniano, W. Waggoner, R. Schuch, H. Schmidt-Backing and H. Ingwersen, Phys. Rev. A29 (1984) 1088. in: Proc. Workshop on Opportunities for 141 P. Richard, Atomic Physics Using Slow. Highly-Charged Ions. Argonne National Laboratory. (Jan. 12-13. 1987) eds. H.G. Berry, R. Dunford. D. Gemmell. and E. Kanter, p. 197. D. Ciric, E. Vlieg, A. De Boer and F.J. de (51 D. Dijkkamp. Heer. J. Phys. B18 (1985) 4763. Muller and F.J. de Heer, Physica 48 (1970) [61 L. Wolterbeek 345. 171 W. Fritch and C.D. Lin, J. Phys. B19 (1986) 2683. [El A. Lindgrd and SE. Nielsen, At. Data Nucl. Data Tables 19 (1977) 533. with S. Hagmann. R. Koch. A. [91 Work done in collaboration Gonzalez, B. Krassig, T. Quinteros, H. Schmidt-B&king, A. Skutlartz.