M. F. Gu 1

Recent Laboratory Astrophysics Work atthe LLNL Electron Beam Ion Traps

Ming Feng Gu, Steven M. KahnKIPAC, Stanford University

Peter Beiersdorfer, Greg Brown, Hui, Chen, Daniel ThornLawrence Livermore National Laboratory

Stanford/SLAC

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Outline

• Overview of LLNL EBIT.

• Cross sections of Ne-like Fe XVII lines.

• Cross sections of Fe XVIII-XXIV lines.

• Inner K-shell transitions of O III-VI.

• Wavelengths survey of high-n lines of Fe XVIII-XXIV.

• Wavelengths survey of 3 → 2 transitions of L-shell Ni.

• Future work.

Stanford/SLAC

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the LLNL Electron Beam Ion Trap

Available spectrometers:crystal, grating, and X-ray microcalorimeter.

Stanford/SLAC

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Cross Section Measurements Using the XRS

• High quantum efficiency.

• Large energy coverage.

• Long-time gain stability.

• Simultaneous monitoring of the collisional excitation andradiative recombination emission.

• σex(E) = K(E)σrr(E) × Iex

Irr.

Stanford/SLAC

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Fe XVII Spectrum measured by Microcalorimeter

20000

15000

10000

5000

0

co

un

ts/

2 e

V b

in

140012001000800600

energy (eV)

80

70

60

50

40

30

20

10

0

co

unts

/4eV

bin

15001450140013501300

energy (eV)

3G+M2

3F

3D

3C

3d3/2+3d5/2

3p1/2+3p3/2

3s1/2

Eb = 964 eV. Brown et al. Phys. Rev. Lett. (submitted)

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Comparison between Theories and Exp.

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Line Ratios of Ne-like Ni XIX

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Cross Sections of Fe XVIII-XXIV Lines

Eb = 2.9 keV

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Supplement XRS with the Crystal Spectrometer

300

250

200

150

100

50

0

Cou

nts

1.201.151.101.051.00

Photon energy (keV)

Measurement Fit

C8

Be1

B13

Be2

Be8

Be9

Li3

Li3(B19)

Li5

Li6

C13

C10

5D

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Global Analysis Method

1. Fit XRS RR spectra to derive relative ion abundances.

2. Fit crystal spectra, using the relative ion abundances derivedfrom RR, and allow the cross sections of strong lines to vary,while keeping the those for weak lines fixed at the theoreticalvalues.

3. Fit XRS excitation spectra, fixing the cross sections as derivedfrom the crystal spectra, determine a new set of ionabundances.

4. The ion abundances derived in step 1 and 3 are compared, andthe ratios for each charge state are used to normalize the crosssection.

5. Ensures that the relative cross sections are determined fromthe high resolution crystal spectra, while the absolutenormalizations are obtained from the fit to the XRS data

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Examples of Measured Cross Sections2.5

2.0

1.5

1.0

0.5

03.02.52.01.5

0.6

0.4

0.2

03.02.52.01.5

B13

B10b

Electron energy (keV)

Effective excitation cross section (10-20cm

2 )

5

4

3

2

1

03.02.52.01.5

1.2

1.0

0.8

0.6

0.4

0.2

03.22.82.42.01.6

Electron energy (keV)

Effective excitation cross section (10-20cm

2 )

C10

C8

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Density Sensitivity of C-like line C10

Electron Denstiy (cm-3)

Effe

ctiv

e C

ross

Sec

tion

(10-

20 c

m-3

)

1011 1012 1013 10140

1

2

3

4

Stanford/SLAC

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Examples of Measured Cross Sections

2.0

1.5

1.0

0.5

03.02.52.01.5

Be2

1.2

0.8

0.4

0

Be1

Electron energy (keV)

Effective excitation cross section (10-20cm

2 )

1.0

0.8

0.6

0.4

0.2

0.5

0.4

0.3

0.2

0.1

03.02.52.01.5

Li3

Li6

Electron energy (keV)

Effective excitation cross section (10-20cm

2 )

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Inner K-shell Transitions of O III-VI

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Measured Wavelengths for K-shell Transitions

Ion Lower(J) Upper(J) λexp(A) Label Index

O VI 1s22s( 12) 1s2s2p( 1

2, 32) 22.374(8) u,v C

O VI 1s22p( 12, 32) 1s2s2( 1

2) 23.017(20) o,p H

O V 1s22s2(0) 1s2s22p(1) 22.370(10) β C

O V 1s22s2p(0,1,2) 1s2s2p2(0,1,2) 22.449(8) D

O V 1s22s2p(2) 1s2s2p2(2) 22.871(5) G

O IV 1s22s22p( 12, 32) 1s2s22p2( 1

2, 32) 22.741(5) E

O IV 1s22s2p2( 52, 32) 1s2s2p3( 3

2) 22.836(5) F

O III 1s22s22p2(1,2) 1s2s22p3(1) 23.071(6) I

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Wavelengths of High-n Lines of Fe L-shell Ions

• For Fe L-shell lines between 10.6 and 18 A, see Brown et al.ApJS, 140, 589, and ApJ, 502, 1015.

• Wavelengths of weaker, high-n transitions of Fe L-shell ions areimportant, e.g., for modeling the line blending in the Mg XItriplet region.

• Using crystal spectrometers, and with four crystal settings, wemeasured all significant Fe L-shell emissions between 7 and 11A, mostly, high-n → 2 transitions, with 4 ≥ n ≤ 10.

• Measurements were taking at different beam energies to selectcharge states.

• Compilation of the line list is in preparation (Chen et al., 2006).

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Lines between 7.0 and 7.5 A

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Lines between 7.4 and 8.4 A

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Lines between 8.3 and 9.0 A

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Lines between 8.7 and 11.0 A

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Wavelengths of Ni L-shell Lines

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Wavelengths of Ni L-shell Lines

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Wavelengths of Ni L-shell Lines

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Wavelengths of Ni L-shell Lines

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Wavelengths of Ni L-shell Lines

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Wavelengths of Ni L-shell Lines

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Wavelengths of Ni L-shell Lines

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Wavelengths of Ni L-shell Lines

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Wavelengths of Ni L-shell Lines

Stanford/SLAC

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Future Work

• X-ray emission following Charge Exchange.

• Inner-shell transitions, K-shell lines of L-shell ions and L-shelllines of M-shell ions (Fe M-shell UTA).

• Life time measurement of M2 transitions in Ne-like ions,important for density diagnositcs.

• Ionization balance measurement of L-shell ions.

• Benchmark the recombination and resonance contributions tothe 3s − 2p transitions in Fe XVII–XX.

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