Anisotropic dielectronic resonancesfrom magnetic-dipole lines

Yuri Ralchenko

National Institute ofStandards and TechnologyGaithersburg, MD, USA

ADAS Workshop, 2013Supported in part by the Office of Fusion Energy Sciences, U.S. DoE

Analyzing 10,000-eV dielectronic resonanceswith 80-eV forbidden lines

Yuri Ralchenko

National Institute ofStandards and TechnologyGaithersburg, MD, USA

ADAS Workshop, 2013Supported in part by the Office of Fusion Energy Sciences, U.S. DoE

Yu. Ralchenko & J.D. GillaspyPhysical Review A 88, 012506 (2013)

Radiative recombination

Continuum

Bound states

𝐴( 𝑍+1 )+¿+𝑒 → 𝐴𝑍 +¿+h𝜈 ¿¿

Ion recombined

DR step 1: dielectronic capture

Continuum

Bound states

Resonant process!

𝐴( 𝑍+1 )+¿+𝑒 → 𝐴𝑍 +∗∗¿

Continuum

Bound states

Dielectronic capture + autoionization= no recombination

DC and AI aredirect and inverse

DR step 2: radiative stabilization

Continuum

Bound states

𝐴( 𝑍+1 )+¿+𝑒 → 𝐴𝑍 +∗∗ → 𝐴𝑍 +∗+h𝜈¿

Stabilizing transition:Mostly x-rays

Dielectronic recombination in plasmas

Z

Z+1…

Maxwellian

Electrons are presentat all energies

(Infinite) Series of transitions areto be accounted for

DR

DR measurements on EBITs

EBIT electronbeam

extractedions

Is ionization distribution the sameinside and outside the trap?..

NO!

1. Extract ions2. Measure ionization distribution

Beam energy

time

ER

ER

ER

Fast beam ramping

DR energy generally does not coincide with the energy of max abundance

DR resonances with M-shell (n=3) ions

LMN resonances:L electron into M,free electron into N

1s22s22p63s23p63dn

Calculation of LMn DR strength: Ca-like 3d2 W54+

2s1/2 3d2p1/2 3d2p3/2 3d

e 3de 4le 5l

1s2(2s2p)83s23p63d + e 1s2(2s2p)73s23p63d2nl

Relativistic model potential+ QED corrections(Flexible Atomic Code, Gu 2008)

Strategy1. Scan electron beam

energy with a small step (a few eV)

2. When a beam hits a DR, ionization balance changes

3. Both the populations of all levels within an ion and the corresponding line intensities change as well

4. Measure line intensity ratios from neighbor ions and look for resonances

5. EUV lines: forbidden magnetic-dipole lines within the ground configuration

A(E1) ~ 1015 s-1

A(M1) ~ 105-106 s-1

I = NAE (intensity)

Ionization potential

Ca-like W54+

Beam energy: 0.1 keV – 30 keVBeam resolution: ~50 eVBeam current: ≤ 150 mABeam radius: ~30 μmElectron density: ~1012 cm-3

Can produce > 60-timesionized atoms

Ar, Kr, Xe, Sn, Ti, Sm, Gd, Dy,Er, Hf, Ta, W, Pt, Au, Bi,…

NIST Electron Beam Ion Trap1.0

0.8

0.6

0.4

0.2

0.0

No

rma

lize

d C

ross

Se

ctio

n

140120100806040200

Speed [106

m/s]

EBIT Electron Beam (width x10) Maxwell-Boltzmann distribution

8 keV

x10

Monoenergetic beam allows one to “touch” dielectronic resonances

Yu. Ralchenko et al, Phys. Rev. A 83, 032517 (2011)

Almost all lines are M1Good statisticsIsolated lines

Pair of lines:(a) within 3d in K-like W55+ (b) within 3d2 in Ca-like W54+

EUV spectrum of W47+-W56+: M1 lines within 3dn ground configurations

[Ca]/[K]

𝑊 54+¿3 𝑑2𝐽 =2 −3𝑑 2

𝐽=3

𝑊 5 5+¿3 𝑑3/ 2 −3𝑑5 /2 ¿¿

[Ca]/[K]:

𝑊 54+¿3 𝑑2𝐽 =2 −3𝑑 2

𝐽=3

𝑊 5 5+¿3 𝑑3/ 2 −3𝑑5 /2 ¿¿

THEORY:no DR

Modeling: CR code NOMAD, atomic data from FAC

[Ca]/[K]

𝑊 54+¿3 𝑑2𝐽 =2 −3𝑑 2

𝐽=3

𝑊 5 5+¿3 𝑑3/ 2 −3𝑑5 /2 ¿¿

THEORY:no DR

[Ca]/[K]

𝑊 54+¿3 𝑑2𝐽 =2 −3𝑑 2

𝐽=3

𝑊 5 5+¿3 𝑑3/ 2 −3𝑑5 /2 ¿¿

THEORY:no DRisotropic DR

Non-Maxwellian (40-eV Gaussian) collisional-radiative model: ~10,500 levels

[Ca]/[K]

𝑊 54+¿3 𝑑2𝐽 =2 −3𝑑 2

𝐽=3

𝑊 5 5+¿3 𝑑3/ 2 −3𝑑5 /2 ¿¿

THEORY:no DRisotropic DRanisotropic DR

atomic level degenerate

magneticsublevels

Jm=-J

m=+J

Impact beam electrons are monodirectional

Non-Maxwellian (40-eV Gaussian) collisional-radiative model: ~10,500 levels

[Ca]/[K]

𝑊 54+¿3 𝑑2𝐽 =2 −3𝑑 2

𝐽=3

𝑊 5 5+¿3 𝑑3/ 2 −3𝑑5 /2 ¿¿

THEORY:no DRisotropic DRanisotropic DR

atomic level degenerate

magneticsublevels

Jm=-J

m=+J

Impact beam electrons are monodirectional

Non-Maxwellian (40-eV Gaussian) collisional-radiative model: ~18,500 levels

[Ca]/[K]

𝑊 54+¿3 𝑑2𝐽 =2 −3𝑑 2

𝐽=3

𝑊 5 5+¿3 𝑑3/ 2 −3𝑑5 /2 ¿¿

2p3/2 3de 4l

One EBIT run, several ions…

Can=4 Sc Ti

Where are the 10-keV photons?..

2p53s23p63dn+14l

2s1/22p1/2

2p3/2

3s3p

3d

4s 4p 4d 4f

~8keV~9keV

~11keV

X-ray emission (Ge detector)

2p53/2-4l

2p53/2-3d

2p53/2-3s

B and C: horizontal

A: slant

n>0 transitions into the 2p3/2 hole

Conclusions

•A new in situ method to measure multi-keV dielectronic resonances in 3dn ions using ratios of EUV magnetic-dipole lines

•First resolved measurements of LMN resonances in ~55-times ionized W

•CR modeling shows importance of anisotropic effects on ionization balance

•Isolated resonances allow determination of the beam width