- Email: [email protected]
Ion–atom merged-beams measurements
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 261 (2007) 129–132 www.elsevier.com/locate/nimb
Ion–atom merged-beams measurements C.C. Havener a
a,*
, E. Galutschek a, R. Rejoub a, D.G. Seely
b
Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6372, United States b Physics Department, Albion College, Albion, MI 49224, United States Available online 19 April 2007
Abstract The ion–atom merged-beams apparatus at Oak Ridge National Laboratory measures benchmark total charge-transfer cross sections for a variety of multicharged ions with atomic H from keV/u down to meV/u center-of-mass collision energies. The apparatus has recently been upgraded and moved to the new high voltage platform where a permanent magnet ECR ion source provides intense high-velocity ion beams. Upgrades to the merged-beams apparatus include more accurate beam profiles and a shortened merge path to increase the angular acceptance of the apparatus. An observed factor of four decrease in the angular divergence of the ion beam translates into access to lower collision energies with higher resolution. The higher velocity ion beams will enable charge transfer measurements with heavier ions, and measurements with both H and D at eV/u energies and below to directly observe the isotope effect. 2007 Elsevier B.V. All rights reserved. PACS: 34.70.+e Keywords: Merged-beams; Charge transfer
1. Introduction The charge transfer (CT) process, Xqþ þ A ! Xðq1Þþ þ Aþ
ð1Þ
by multicharged ions (Xq+) from neutral atoms (A) at low collision energies (meV/u–keV/u) is characterized by large cross sections, on the order of 1014–1016 cm2 and therefore important in many plasmas where ions and neutrals exist. Low energy CT is important for interpreting spectroscopic diagnostics and modeling of core, edge and diverter regions of magnetically confined fusion plasmas. In astrophysics, charge transfer by multicharged ions from H is important in planetary nebulae and H II regions. While scaling laws have been successful in describing charge transfer at higher energies, at low energies (<1 keV/u), models must correctly handle both the quasi-molecular and fully quantum nature of the collision dynamics. Molecular *
Corresponding author. Tel.: +1 865 574 4704; fax: +1 865 574 1118. E-mail address: [email protected] (C.C. Havener).
0168-583X/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.04.103
orbital close coupling (MOCC) calculations are deemed most appropriate but difficult to perform and often have not been extended to eV/u energies and below. ORNL merged-beam measurements for Si4+ [1], Ne4+ [2], N4+ [3] and C4+ [4] + H (or D) are shown in Fig. 1 along with two MOCC calculations [1] which extend to low energies for Si4+. Calculations for C4+ [5] from a more recently developed hyperspherical close coupling (HSCC) method are also shown. all measurements below 10 eV/u were performed with D. As can be seen in the figure, all the q = 4+ cross sections are similar around 1000 eV/u, and are found to scale according to an empirical scaling law (r q · 1015 cm2) proposed by Phaneuf [6]. As the CT cross section decreases to lower energies, the measurements show a marked variation for the different ions with different electron cores, over a factor of ten at 10 eV/u between C4+ and Si4+. The measurements for Si4+ and Ne4+ have been extended to sufficiently low collision velocities (v) to observe the enhancement in the cross section (1/v) due to trajectory effects caused by the ion-induced dipole potential [1]. The Si4+measurements show excellent agreement with the MOCC calculations for D; the MOCC
130
C.C. Havener et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 129–132
marked to the merged-beams measurements and extended to lower energies, exhibit a 1/v increase. the temporary decrease in the cross section is due to the quantal nature of the charge transfer process.
4+
Si 4+ Ne 4+ N 4+ C 4+ Si + H; MOCC 4+ Si + D; MOCC 4+ C + H; HSCC
Cross Section (10-16 cm2)
100
2. Experimental Technique
50
0 0.01
0.1
1
10
100
1000
Energy (eV/u) Fig. 1. ORNL ion–atom merged-beams measurements for various q = 4+ ions on H (D). For Si4+ and C4+, the measurements are compared to MOCC and HSCC calculations. See text for details.
calculations for H exhibit a large isotope effect also indicative of trajectory effects [1]. For C4+ the HSCC calculation also shows the 1/v increase. In fact, all the other calculations (not shown) for the various q = 4+ ions, bench-
Low energy charge transfer is performed at the Multicharged Ion Research Facility (MIRF) at ORNL using the ion–atom merged-beams apparatus which has previously been described in detail [7]. The newly upgraded version of the apparatus is shown in Fig. 2. In this technique, intense relatively fast (keV) ion and atomic beams are merged producing center-of-mass collision energies from meV/u to keV/u. A neutral ground state hydrogen (or deuterium) beam is obtained by photodetachment of an H beam as it crosses the optical cavity of a 1.06 lm cw ND:YAG laser where kilowatts of continuous power circulate. The H is extracted from a duoplasmatron ion source. The ion and neutral beams interact along a field-free region, after which H+ product ions are magnetically separated from the primary beams. The neutral beam is monitored by measuring secondary electron emission from a stainless steel plate, and the intensity of the ion beam is
ION BEAM (20-150kV) HV PLATFORM
NEGATIVE ION SOURCE (e.g., H , 5 - 30 kV)
X
0
q+
1.0 meter
0.5
30˚ BENDING MAGNET LENS
X, Y STEERER
PAIR of SLITS cw Nd: YAG LASER (NEUTRALIZATION) ELECTROSTATIC QUADRUPOLES
H - BEAM DUMP
SLITS ELECTROSTATIC SPHERICAL DEFLECTORS
(a)
(b)
8.9 cm
3.4 cm
DUAL ROTATING WIRE BEAM SCANNER
MECHANICAL SLITS
LENSES
2+
H
DETECTOR
6.9 kV D, 48 keV N
10 kV H, 132 keV N2+
43.9 cm
29.3 cm
VERTICAL DEFLECTOR
DEMERGE MAGNET H˚
X
q+ (q-1)+ , X
H'
V'
H'
V'
Fig. 2. Schematic of the current ORNL ion–atom merged-beams apparatus. The inset compares +45 (H’) and 45 (V’) beam profiles at two positions along the merge path for the neutral (dashed) and the ion beam (solid) beams (a) from the old CAPRICE ECR and (b) from the new high velocity beams from the HV platform.
C.C. Havener et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 129–132
Scqe2 v1 v2 r¼ ; I 1 I 2 vr L < F >
ð2Þ
where S is the signal count rate, q is the charge number of the ion, e is the electronic charge, I1 and I2 are the currents of the beams, v1 and v2 are the velocities of the beams, vr is the relative velocity of the beams, L is the merge-path length, c is the secondary electron emission coefficient of the neutral detector, and hFi is the average form factor measuring the overlap of the beams. The form factor is estimated from two-dimensional measurements of the beam– beam overlap at four different positions along the merged path. The secondary electron emission coefficient c is measured in situ. The velocities are calculated from the accelerating voltages of the beams, which include the estimated plasma potential shifts of the two sources (see, e.g. [1]). The small (non-zero) angle between the merged beams must be determined along with the angular spreads of the interacting beams. It is the overlapped angular spread of the beams which effectively determines the energy spread of the measurements in the meV/u energy range. 3. Results and discussion The upgraded apparatus, shown schematically in Fig. 2, has recently been moved at MIRF to accept beams from a CEA/Grenoble all-permanent magnet ECR ion source mounted on a 20–250 kV high voltage (HV) platform. Upgrades to the apparatus include a dual rotating wire scanner which provides a real-time indication of the divergence of the beams and a shorter merge path (47.1– 32.5 cm) which increases the angular acceptance from 2.3 to 3.3 in the lab frame. This increase transforms to a significant increase of angular collection in the center-of-mass frame where the products often exhibit significant angular scattering [9]. A high-transmission beam line from the HV platform contains two electrostatic quadrupole lenses and three sets of slits which are used to shape the beam and form a waste at the focal point of an electrostatic spherical sector analyzer. The subsequent ‘‘parallel’’ ion beam is thus merged with the neutral beam in the merge path. The inset, in Fig. 2 shows the improvements in the beam profiles compared to previous profiles with the (5–20 kV) ORNL CAPRICE ECR ion source. There is almost a factor of four decrease in the angular divergence of the ion beam. This translates into a significant improvement in the collision energy uncertainty and will allow access to lower ener-
70 Present w/D Present w/H Pieksma (97) Wilke (85) Bienstock (86) Herrero (95) Barragan (06)
60
Cross Section (10-16 cm2)
measured by a faraday cup. The product signal of H+ ions is detected with a channel electron multiplier operated in pulse counting mode. The beam–beam signal rate (HZ) is extracted from (kHZ) backgrounds with a two-beam modulation technique. The technique has been highly successful in providing benchmark CT total cross sections [8] for a variety of multiply charged ions in collisions with H and D. The independently absolute charge transfer cross section is determined at each velocity from directly measurable parameters from the following formula,
131
50 40 30 20 10 0 0.01
0.1
1
10
100
Energy (eV/u) Fig. 3. Present merged-beams measurements for N2+ with H and D are compared with our previous merged-beams measurements of Pieksma et al. [14], measurements of Wilke et al. [15] and theory. See text.
gies with higher resolution. The higher velocity ion beam will make possible measurements with both H and D at energies below 1 eV/u. Previously, the higher velocity ion beams needed to match typical H beam velocities were not available from the CAPRICE ECR. Measurements at low center-of-mass collision energies had to be performed with D, especially for heavier lower charge ions. A collision system which is not predicted to exhibit the typical (1/v) enhancement in the cross section at low collision energies is N2+ + H and is shown in Fig. 3. MOCC calculations by Bienstock et al. [10], Herrero et al. [11] and Barragan et al. [12] all show a cross section decreasing at lower energies. The most recent calculation of Barragan et al. [12] uses more accurate molecular potentials compared to their earlier work [13] which predicted a cross section which decreases at lower energies similar to the calculation of Herrero et al. [11]. ORNL merged-beam measurements by Pieksma et al. [14] did not extend to low enough energies to establish the low energy dependence. New measurements for this system are presented here with D using the old CAPRICE ECR and with H using the new HV platform. The measurements with D clearly show an increasing cross section toward lower energies in sharp contrast to the calculations. The measurements with H, which are now being performed with ion beams from the HV platform, are to be extended to low enough energies to test whether an isotope effect is present. 4. Future The HV platform provides quality high velocity ion beams which allow much higher resolution measurements with both H and D below an eV/u. It may be possible to explore low energy CT for structure, e.g. due to Regge oscillations [16] or shape resonances [17]. The ion beams are now of sufficient intensity that state-selective CT may
132
C.C. Havener et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 129–132
now be possible using photon spectroscopy. The observed intense ion beams should permit X-ray emission measurements for a variety of bare and H-like ions (e.g. C, N, O) + H. Such measurements are possible by using a high efficiency detector mounted directly above the merge path. The sounding rocket X-ray Calorimeter [18] is being considered for these measurements. The X-ray detector is characterized by a high energy resolution (5–12 eV FWHM) along with high throughput (1000 times greater than dispersive X-ray detectors). A Cs negative-ion sputter source can be exchanged with the duoplasmatron and used to provide a variety of multi-electron neutral beams, e.g. Li, B, Na, Al, P, K, Cr, Fe and molecular beams like O2 and CH2. The HV platform will soon be configured with a cold molecular ion source which will allow measurements with molecular ions. Acknowledgement This research is supported by the DoE, Division of Chemical Sciences, Office Of Basic Energy Sciences and the Division of Applied Plasma Physics, Office of Fusion Energy Sciences, under Contract No. DE-AC0500OR22725 with UT-battelle, LLC.
References [1] M. Pieksma, M. Gargaud, R. McCarroll, C.C. Havener, Phys. Rev. A 54 (1996) R13. [2] C.C. Havener et al., Phys. Rev. A 71 (2005) 042707. [3] L. Folkerts et al., Phys. Rev. A 51 (1995) 3685. [4] F.W. Bliek et al., Phys. Rev. A 56 (1997) 426. [5] C-N Liu, A-T Le, C.D. Lin, Phys. Rev. A 68 (2003) 062702. [6] R.A. Phaneuf, Phys. Rev. A 28 (1983) 1310. [7] C.C. Havener, in: S.M. Shafroth, J.C. Austin (Eds.), Acceleratorbased Atomic Physics Techniques and Applications, AIP, New York, 1997, p. 117. [8] C.C. Havener, The Physics of Multiply and Highly Charged Ions, Vol. 2, Kluwer Academic Publishers, Dordrecht, The Netherlands, 2003, p. 193. [9] C.C. Havener, R. Rejoub, P.S. Krstic, A.C.H. Smith, Phys. Rev. A 71 (2005) 015504. [10] S. Bienstock, A. Dalgarno, T.G. Heil, Phys. Rev. A 33 (1986) 2078. [11] B. Herrero, I.L. Cooper, A.S. Dickenson, D.R. Flower, Phys. Rev. A 28 (1995) 711. [12] P. Barragan et al., Phys. Rev. A 74 (2006) 024701. [13] P. Barragan et al., Phys. Rev. A 70 (2004) 022707. [14] M. Pieksma, M.E. Bannister, W. Wu, C.C. Havener, Phys. Rev. A 55 (1997) 3526. [15] F.G. Wilke et al., J. Phys. B 18 (1985) 479. [16] J.H. Macek et al., Phys. Rev. Lett. 93 (2004) 183293. [17] M. Rittby et al., J. Phys. B 17 (1984) L677. [18] D. McCammon et al., ApJ 576 (2002) 188.
Nuclear Instruments and Methods in Physics Research B 261 (2007) 129–132 www.elsevier.com/locate/nimb
Ion–atom merged-beams measurements C.C. Havener a
a,*
, E. Galutschek a, R. Rejoub a, D.G. Seely
b
Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6372, United States b Physics Department, Albion College, Albion, MI 49224, United States Available online 19 April 2007
Abstract The ion–atom merged-beams apparatus at Oak Ridge National Laboratory measures benchmark total charge-transfer cross sections for a variety of multicharged ions with atomic H from keV/u down to meV/u center-of-mass collision energies. The apparatus has recently been upgraded and moved to the new high voltage platform where a permanent magnet ECR ion source provides intense high-velocity ion beams. Upgrades to the merged-beams apparatus include more accurate beam profiles and a shortened merge path to increase the angular acceptance of the apparatus. An observed factor of four decrease in the angular divergence of the ion beam translates into access to lower collision energies with higher resolution. The higher velocity ion beams will enable charge transfer measurements with heavier ions, and measurements with both H and D at eV/u energies and below to directly observe the isotope effect. 2007 Elsevier B.V. All rights reserved. PACS: 34.70.+e Keywords: Merged-beams; Charge transfer
1. Introduction The charge transfer (CT) process, Xqþ þ A ! Xðq1Þþ þ Aþ
ð1Þ
by multicharged ions (Xq+) from neutral atoms (A) at low collision energies (meV/u–keV/u) is characterized by large cross sections, on the order of 1014–1016 cm2 and therefore important in many plasmas where ions and neutrals exist. Low energy CT is important for interpreting spectroscopic diagnostics and modeling of core, edge and diverter regions of magnetically confined fusion plasmas. In astrophysics, charge transfer by multicharged ions from H is important in planetary nebulae and H II regions. While scaling laws have been successful in describing charge transfer at higher energies, at low energies (<1 keV/u), models must correctly handle both the quasi-molecular and fully quantum nature of the collision dynamics. Molecular *
Corresponding author. Tel.: +1 865 574 4704; fax: +1 865 574 1118. E-mail address: [email protected] (C.C. Havener).
0168-583X/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.04.103
orbital close coupling (MOCC) calculations are deemed most appropriate but difficult to perform and often have not been extended to eV/u energies and below. ORNL merged-beam measurements for Si4+ [1], Ne4+ [2], N4+ [3] and C4+ [4] + H (or D) are shown in Fig. 1 along with two MOCC calculations [1] which extend to low energies for Si4+. Calculations for C4+ [5] from a more recently developed hyperspherical close coupling (HSCC) method are also shown. all measurements below 10 eV/u were performed with D. As can be seen in the figure, all the q = 4+ cross sections are similar around 1000 eV/u, and are found to scale according to an empirical scaling law (r q · 1015 cm2) proposed by Phaneuf [6]. As the CT cross section decreases to lower energies, the measurements show a marked variation for the different ions with different electron cores, over a factor of ten at 10 eV/u between C4+ and Si4+. The measurements for Si4+ and Ne4+ have been extended to sufficiently low collision velocities (v) to observe the enhancement in the cross section (1/v) due to trajectory effects caused by the ion-induced dipole potential [1]. The Si4+measurements show excellent agreement with the MOCC calculations for D; the MOCC
130
C.C. Havener et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 129–132
marked to the merged-beams measurements and extended to lower energies, exhibit a 1/v increase. the temporary decrease in the cross section is due to the quantal nature of the charge transfer process.
4+
Si 4+ Ne 4+ N 4+ C 4+ Si + H; MOCC 4+ Si + D; MOCC 4+ C + H; HSCC
Cross Section (10-16 cm2)
100
2. Experimental Technique
50
0 0.01
0.1
1
10
100
1000
Energy (eV/u) Fig. 1. ORNL ion–atom merged-beams measurements for various q = 4+ ions on H (D). For Si4+ and C4+, the measurements are compared to MOCC and HSCC calculations. See text for details.
calculations for H exhibit a large isotope effect also indicative of trajectory effects [1]. For C4+ the HSCC calculation also shows the 1/v increase. In fact, all the other calculations (not shown) for the various q = 4+ ions, bench-
Low energy charge transfer is performed at the Multicharged Ion Research Facility (MIRF) at ORNL using the ion–atom merged-beams apparatus which has previously been described in detail [7]. The newly upgraded version of the apparatus is shown in Fig. 2. In this technique, intense relatively fast (keV) ion and atomic beams are merged producing center-of-mass collision energies from meV/u to keV/u. A neutral ground state hydrogen (or deuterium) beam is obtained by photodetachment of an H beam as it crosses the optical cavity of a 1.06 lm cw ND:YAG laser where kilowatts of continuous power circulate. The H is extracted from a duoplasmatron ion source. The ion and neutral beams interact along a field-free region, after which H+ product ions are magnetically separated from the primary beams. The neutral beam is monitored by measuring secondary electron emission from a stainless steel plate, and the intensity of the ion beam is
ION BEAM (20-150kV) HV PLATFORM
NEGATIVE ION SOURCE (e.g., H , 5 - 30 kV)
X
0
q+
1.0 meter
0.5
30˚ BENDING MAGNET LENS
X, Y STEERER
PAIR of SLITS cw Nd: YAG LASER (NEUTRALIZATION) ELECTROSTATIC QUADRUPOLES
H - BEAM DUMP
SLITS ELECTROSTATIC SPHERICAL DEFLECTORS
(a)
(b)
8.9 cm
3.4 cm
DUAL ROTATING WIRE BEAM SCANNER
MECHANICAL SLITS
LENSES
2+
H
DETECTOR
6.9 kV D, 48 keV N
10 kV H, 132 keV N2+
43.9 cm
29.3 cm
VERTICAL DEFLECTOR
DEMERGE MAGNET H˚
X
q+ (q-1)+ , X
H'
V'
H'
V'
Fig. 2. Schematic of the current ORNL ion–atom merged-beams apparatus. The inset compares +45 (H’) and 45 (V’) beam profiles at two positions along the merge path for the neutral (dashed) and the ion beam (solid) beams (a) from the old CAPRICE ECR and (b) from the new high velocity beams from the HV platform.
C.C. Havener et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 129–132
Scqe2 v1 v2 r¼ ; I 1 I 2 vr L < F >
ð2Þ
where S is the signal count rate, q is the charge number of the ion, e is the electronic charge, I1 and I2 are the currents of the beams, v1 and v2 are the velocities of the beams, vr is the relative velocity of the beams, L is the merge-path length, c is the secondary electron emission coefficient of the neutral detector, and hFi is the average form factor measuring the overlap of the beams. The form factor is estimated from two-dimensional measurements of the beam– beam overlap at four different positions along the merged path. The secondary electron emission coefficient c is measured in situ. The velocities are calculated from the accelerating voltages of the beams, which include the estimated plasma potential shifts of the two sources (see, e.g. [1]). The small (non-zero) angle between the merged beams must be determined along with the angular spreads of the interacting beams. It is the overlapped angular spread of the beams which effectively determines the energy spread of the measurements in the meV/u energy range. 3. Results and discussion The upgraded apparatus, shown schematically in Fig. 2, has recently been moved at MIRF to accept beams from a CEA/Grenoble all-permanent magnet ECR ion source mounted on a 20–250 kV high voltage (HV) platform. Upgrades to the apparatus include a dual rotating wire scanner which provides a real-time indication of the divergence of the beams and a shorter merge path (47.1– 32.5 cm) which increases the angular acceptance from 2.3 to 3.3 in the lab frame. This increase transforms to a significant increase of angular collection in the center-of-mass frame where the products often exhibit significant angular scattering [9]. A high-transmission beam line from the HV platform contains two electrostatic quadrupole lenses and three sets of slits which are used to shape the beam and form a waste at the focal point of an electrostatic spherical sector analyzer. The subsequent ‘‘parallel’’ ion beam is thus merged with the neutral beam in the merge path. The inset, in Fig. 2 shows the improvements in the beam profiles compared to previous profiles with the (5–20 kV) ORNL CAPRICE ECR ion source. There is almost a factor of four decrease in the angular divergence of the ion beam. This translates into a significant improvement in the collision energy uncertainty and will allow access to lower ener-
70 Present w/D Present w/H Pieksma (97) Wilke (85) Bienstock (86) Herrero (95) Barragan (06)
60
Cross Section (10-16 cm2)
measured by a faraday cup. The product signal of H+ ions is detected with a channel electron multiplier operated in pulse counting mode. The beam–beam signal rate (HZ) is extracted from (kHZ) backgrounds with a two-beam modulation technique. The technique has been highly successful in providing benchmark CT total cross sections [8] for a variety of multiply charged ions in collisions with H and D. The independently absolute charge transfer cross section is determined at each velocity from directly measurable parameters from the following formula,
131
50 40 30 20 10 0 0.01
0.1
1
10
100
Energy (eV/u) Fig. 3. Present merged-beams measurements for N2+ with H and D are compared with our previous merged-beams measurements of Pieksma et al. [14], measurements of Wilke et al. [15] and theory. See text.
gies with higher resolution. The higher velocity ion beam will make possible measurements with both H and D at energies below 1 eV/u. Previously, the higher velocity ion beams needed to match typical H beam velocities were not available from the CAPRICE ECR. Measurements at low center-of-mass collision energies had to be performed with D, especially for heavier lower charge ions. A collision system which is not predicted to exhibit the typical (1/v) enhancement in the cross section at low collision energies is N2+ + H and is shown in Fig. 3. MOCC calculations by Bienstock et al. [10], Herrero et al. [11] and Barragan et al. [12] all show a cross section decreasing at lower energies. The most recent calculation of Barragan et al. [12] uses more accurate molecular potentials compared to their earlier work [13] which predicted a cross section which decreases at lower energies similar to the calculation of Herrero et al. [11]. ORNL merged-beam measurements by Pieksma et al. [14] did not extend to low enough energies to establish the low energy dependence. New measurements for this system are presented here with D using the old CAPRICE ECR and with H using the new HV platform. The measurements with D clearly show an increasing cross section toward lower energies in sharp contrast to the calculations. The measurements with H, which are now being performed with ion beams from the HV platform, are to be extended to low enough energies to test whether an isotope effect is present. 4. Future The HV platform provides quality high velocity ion beams which allow much higher resolution measurements with both H and D below an eV/u. It may be possible to explore low energy CT for structure, e.g. due to Regge oscillations [16] or shape resonances [17]. The ion beams are now of sufficient intensity that state-selective CT may
132
C.C. Havener et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 129–132
now be possible using photon spectroscopy. The observed intense ion beams should permit X-ray emission measurements for a variety of bare and H-like ions (e.g. C, N, O) + H. Such measurements are possible by using a high efficiency detector mounted directly above the merge path. The sounding rocket X-ray Calorimeter [18] is being considered for these measurements. The X-ray detector is characterized by a high energy resolution (5–12 eV FWHM) along with high throughput (1000 times greater than dispersive X-ray detectors). A Cs negative-ion sputter source can be exchanged with the duoplasmatron and used to provide a variety of multi-electron neutral beams, e.g. Li, B, Na, Al, P, K, Cr, Fe and molecular beams like O2 and CH2. The HV platform will soon be configured with a cold molecular ion source which will allow measurements with molecular ions. Acknowledgement This research is supported by the DoE, Division of Chemical Sciences, Office Of Basic Energy Sciences and the Division of Applied Plasma Physics, Office of Fusion Energy Sciences, under Contract No. DE-AC0500OR22725 with UT-battelle, LLC.
References [1] M. Pieksma, M. Gargaud, R. McCarroll, C.C. Havener, Phys. Rev. A 54 (1996) R13. [2] C.C. Havener et al., Phys. Rev. A 71 (2005) 042707. [3] L. Folkerts et al., Phys. Rev. A 51 (1995) 3685. [4] F.W. Bliek et al., Phys. Rev. A 56 (1997) 426. [5] C-N Liu, A-T Le, C.D. Lin, Phys. Rev. A 68 (2003) 062702. [6] R.A. Phaneuf, Phys. Rev. A 28 (1983) 1310. [7] C.C. Havener, in: S.M. Shafroth, J.C. Austin (Eds.), Acceleratorbased Atomic Physics Techniques and Applications, AIP, New York, 1997, p. 117. [8] C.C. Havener, The Physics of Multiply and Highly Charged Ions, Vol. 2, Kluwer Academic Publishers, Dordrecht, The Netherlands, 2003, p. 193. [9] C.C. Havener, R. Rejoub, P.S. Krstic, A.C.H. Smith, Phys. Rev. A 71 (2005) 015504. [10] S. Bienstock, A. Dalgarno, T.G. Heil, Phys. Rev. A 33 (1986) 2078. [11] B. Herrero, I.L. Cooper, A.S. Dickenson, D.R. Flower, Phys. Rev. A 28 (1995) 711. [12] P. Barragan et al., Phys. Rev. A 74 (2006) 024701. [13] P. Barragan et al., Phys. Rev. A 70 (2004) 022707. [14] M. Pieksma, M.E. Bannister, W. Wu, C.C. Havener, Phys. Rev. A 55 (1997) 3526. [15] F.G. Wilke et al., J. Phys. B 18 (1985) 479. [16] J.H. Macek et al., Phys. Rev. Lett. 93 (2004) 183293. [17] M. Rittby et al., J. Phys. B 17 (1984) L677. [18] D. McCammon et al., ApJ 576 (2002) 188.