Ameland, day 2 Hard-core atomic physics: highly charged ions Jos - - PowerPoint PPT Presentation

Ameland, day 2

Hard-core atomic physics: highly charged ions

José R. José R. Crespo López-Urrut Crespo López-Urrutia Max-Planck-Instit Max-Planck-Institut für Kernphysik für Kernphysik Heidelberg Heidelberg

(59 ± 9) % of baryons are missing

Cosmological simulations (Cen & Ostriker) predict a warm-hot interstellar medium (WHIM) heated by gravitation to 106 K containing most of the missing baryons

The warm-hot intergalactic medium The warm-hot intergalactic medium

To hot for visible light, too diffuse for direct X-ray detection

Fe L-shell autoionizing resonances carry 60%

• f total photoabsortion strength at T500 eV

500 1000 1500

1x10

• 16

2x10

• 16

3x10

• 16

10

• 21

10

• 20

10

• 19

10

• 18

10

• 17

10

• 16

10

• 15

Integrated PI strength (cm

2 eV)

Photon energy (eV)

Total strength Resonant strength Direct photoionization strength Planck continuum

Cross section weighted with Planck continuum

Resonances dominate!

PI cross section (cm

2)

Direct PI cross section Total PI cross section

Fe ions with a few remaining electrons can resonantly absorb photons and also be excited by monoenergetic electrons

Plasma temperature T=190 eV Parameter u=hv/kT

Figure 5 from: Solar Mixture Opacity Calculations Using Detailed Configuration and Level Accounting Treatments Christophe Blancard et al. 2012 ApJ 745 10

Fe XVII at base of the solar convection zone

L shell absorption M shell absorption

Fe XVII ion has largest contribution to opacity

T = 2 × 106 K Ne = 1023 cm−3

Figure from: Solar Mixture Opacity Calculations Using Detailed Configuration and Level Accounting Treatments Christophe Blancard et al. 2012 ApJ 745 10

Contribution of Fe to total opacity

Fe Fe

H, He H, He

How do we make them in the laboratory?

• Fusion machines, magnetically confined plasmas
• High power lasers, X-ray lasers
• Ion accelerators
• Electron beam ion traps

I onization potential rises from 1 0 to 1 3 0 0 0 0 eV

10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 100

barium tungsten krypton neon argon

uranium

Ionization potential (keV) Ion charge state q+

Highly charged ions at accelerators

• Take ions at half the speed of light (e. g. at GSI Darmstadt)
• send them through a thin foil: outer electrons are stripped
• Very hot highly charged ions are produced and stored
• Disordered thermal motion reduces resolution
• Deceleration and cooling in progress (HiTrap project, GSI)

ion source accelerator stripper foil

storage ring

Storage ring = synchrotron without acceleration

With increasing charge state:

• Higher binding energy
• Smaller cross section

Continuum 130 keV 31 keV 12 keV n=1 n=2 n=3

Electron with (sufficient) energy Ek

Making HCI by electron impact ionization

• In the electron beam ion source (EBIS), a fast, dense,

electron beam interacts with atoms and produces ions.

• Ions are confined radially by the potential well in the

electron beam and axially by ring electrodes.

• Ions can be accumulated in or expelled out of it.
• As the interaction time between electrons and ions defines

the highest charge state achievable, high current density (of the order of 1000A/cm2) electron beams are required.

• Since normal cathodes are limited to less than 10A/cm2,

beam compression by means of a strong magnetic field is needed.

Electron beam ion source

Poisson‘s equation in cylindrical coordinates Resulting potential with boundary conditions

Space charge potential: a line charge

1000 2000 3000 20 40 60 80 100 120 140

center drift tube radius

space charge potential

electron density (normalized to 50)

Space charge potential (V) Distance from axis (m)

Ebeam=2162 eV Ibeam=40 mA

Space charge potential of the electron beam

0.1 1 10 100 1000 20 40 60 80 100 120 140

center drift tube radius electron beam radius

space charge potential electron density (normalized to 50)

Space charge potential (V) Distance from axis (m)

Ebeam=2162 eV Ibeam=40 mA

Space charge potential of the electron beam

EBIT (electron beam ion trap) invented at LLNL

Currently: 10 EBITs worldwide,

• f which 3 of the

largest are in Heidelberg (Levine & Marrs 1986)

• As electrons collide with the ions in the beam, they

strip off electrons until the energy required to remove the next electron is higher than the beam energy

• The original LLNL EBIT (1986) is capable of an

electron beam energy of about 30 keV, enough to make neon-like uranium (U82+)

• From this EBIT-I, a high-energy EBIT, named

SuperEBIT, was built. It has an electron gun that can achieve an electron beam energy of 200 keV, enough to make bare uranium (U92+)

The electron beam ion trap (EBIT)

HCI production with electron beam ion trap

radial potential radial potential electr electron beam

• n beam

space charge space charge

15000 A 15000 A/cm cm2 ne

e  10

1013

13 e-/cm

/cm3

axial potential axial potential electr electrodes

• des

Ibeam

beam =450

=450 mA mA

Electron beam drives ionization, excites and traps the ions inside a cylindrical volume

0.01 0.1 1 10 0.0 0.1 0.2 0.3

Hg10+ Hg20+ Hg30+ Hg40+ Hg78+ Hg70+

Charge state fraction Ionization time (s)

Hg52+

Tim e evolution of the charge state Calculated for Hg ions at 50 keV electron beam energy by numerically solving a set of coupled differential equations for the ionization and recombination processes:

Der Feind: Rekombination

n n n n n n n n n n

Ne9+

N

Ladungsaustausch: Neutrale Atome geben Elektronen ab Lösung: Vakuum bei 10-13 mbar (Weltraumbedingungen) Einfang freier Elektronen

n n n n n

Lösung: höhere Elektronenenergie

(1000 Atome/cm3) strahlungsmäßige Rekombination radiative recombination (RR)

Photon emittiert

Electron beam ion traps

• An electron beam produces, traps and excites HCI
• Diagnostics from the optical to the hard x-ray range
• Additional ionic species particle diagnostics
• Studies from N3+ to Hg78+

Electron beam ion traps

electron gun collector superconducting magnet trap region

Evaporative cooling

• heavy, highly charged ions (e.g. Ba53+ ) remain trapped indefinitely

Evaporative cooling

• collisions with beam electrons heat up ion ensemble
• light, less tightly trapped ions (e.g. Ne10+ ) evaporate removing thermal energy: a

single Ne10+ takes away 2 keV (1 second additional life for a heavy ion)

Ion temperat Ion temperatures from 1000 ures from 1000 eV eV to 10 eV to 10 eV Doppler width Doppler width /  1/20.000 (Ba 1/20.000 (Ba53+

53+)

High resolution High resolution spectroscopy spectroscopy

500 1000 1500 2000 0.0 0.2 0.4 0.6 0.8 1.0

D B

Relative energy distribution function Potential energy (arb. units)

Trapping potential

Evaporating fraction Light ions Heavy ions

Evaporative cooling: energy distribution function relative to trapping potential

EBI Ts are good to reproduce the conditions prevailing in astrophysical plasm as

transient plasmas, strong density and temperature gradients EBITs: stationary, homogeneous conditions

Density and temperature space sampled by different spectroscopic light sources

• P. Beiersdorfer, Annu. Rev. Astron. Astrophys. 4 1 ( 2 0 0 3 ) 3 4 3 -3 9 0

X-ray diagnostics: Bragg’s law

CCD 1 CCD 2 crystal EBIT 

180°- 2Θ



|a/b| ξ

Absolute m easurem ents Γ = 180°- 2Θ

180°-2Θ

Bond method (W.L. Bond, Acta Cryst. 13, 814 (1960))

Absolute measurements Side-on vs. end-on spectra: line/point source

The Lyman- spectrum of hydrogenic Ar17+

Testing QED Screening and Two-Loop Contributions with He-Like Ions, H. Bruhns, J. Braun, K. Kubiček, J. R. Crespo López-Urrutia, and J. Ullrich, Phys. Rev. Lett. 99, 113001 (2007)

• K. Kubiček, P. H. Mokler, V. Mäckel, J. Ullrich, and J. R. Crespo López-Urrutia, Transition energy measurements in

hydrogenlike and heliumlike ions strongly supporting bound-state QED calculations, Phys. Rev. A 90 90, 032508 (2014)

Lyman-α and w in S, Ar HCI: Scaled spectra

Testing QED Screening and Two-Loop Contributions with He-Like Ions, H. Bruhns, J. Braun, K. Kubiček, J. R. Crespo López-Urrutia, and J. Ullrich, Phys. Rev. Lett. 99, 113001 (2007)

• K. Kubiček, P. H. Mokler, V. Mäckel, J. Ullrich, and J. R. Crespo López-Urrutia, Transition energy measurements in

hydrogenlike and heliumlike ions strongly supporting bound-state QED calculations, Phys. Rev. A 90 90, 032508 (2014)

GSI Gumberidze et al., PRL 94, 94, 223001 (2005)

LLNL Beiersdorfer et al., PRL 95, 95, 233003 (2005)

Beiersdorfer … JRCLU et al., Measurement of QED and Hyperfine Splitting in the 2s1/2- 2p3/2 X-Ray Transition in Li-like 209Bi80+, Phys. Rev. Lett. 80 80, 3022 (1998)

The Lyman-α spectrum of hydrogenic Ar

Z Artemyev Drake Experiment Ref. This work [5] Remarks

________________________________________________________________________________ 16 2460.629 2460.628 2460.649(9) [1] 2460.626(3)

2460.626(3) Absolute, Absolute, 3x 3x

18 3139.582 3139.580 3139.553(38) [2] 3139.581(4)

3139.581(4) Absolute, Absolute, 10x 10x

26 6700.435(1) 6700.423 6700.730(200) [3] 6700.775(13)

6700.775(13) Absolute, Absolute, 7x 7x

6700.900(250) [4]

In Fe24+ contribution to this transition of:

• 4 eV QED,
• 200 meV screened QED,
• 100 meV nuclear recoil contributions
• vs. 13 meV uncertainty

[1] L. Schleinkofer et al., Phys. Scr. 25 25, 917 (1982) [2] R. D. Deslattes, H. F. Beyer, and F. Folkmann, J. Phys. B 17 17, L689 (1984) [3] P. Beiersdorfer et al., Phys. Rev. A 40 40, 150 (1989) [4] J. P. Briand et al., Phys. Rev. A 29 29, 3143 (1984) [5] K. Kubicek et al., Rev. Sci. Instrum. (2012)

The He-like1 s2 p 1P1- 1 s2 1S0 resonance line w

0.1 eV 0.1 eV 5 eV 5 eV 300 eV 300 eV 1 eV 1 eV

Contributions Contributions to ground state to ground state in He-like in He-like Ar Ar16+

16+

(4000 eV (4000 eV binding binding energy) energy)

experimental experimental error bar: error bar: ≈  0.01 0.01 eV eV

E

+ + h. o.

nuclear recoil 0.06 eV higher orders 0.001 eV

Tw o-electron QED Feynm an diagram s

Hydrogenic standards?

Best HCI line elsewhere Ar17+ Ly1 (5 ppm)

Current x-ray standards impaired by satellites

Calibration line Fe K (1 ppm)

Counts Wavelength (pm)

satellites

A VUV spectrum recorded on a x-ray CCD cam era

• Each pixel acts as an individual Si detector and contains

inform ation about the photon energy.

Grating spectrom eter spectrum of Fe 2 3 + ions

Fe XXII 24.719 nm (th: 24.72) Fe XXIV 25.5113 nm (48.5997 eV) K: Fe XX 12.1858 nm D: Fe XXI 12.8755 nm A: Fe XXIII 13.2906 nm F: Fe XXIV 19.2028 nm C: Fe XXIII 13.5812 nm 2nd D 2nd A 2nd C 2nd Fe XXII 11.7144 nm 2nd Fe XXII 11.4412 nm Fe XV 28.4164 nm

1 0 2

Fe XXII 24.719 nm Fe XXIV 25.5113 nm (48.5997 eV) Fe XXIV 19.2028 nm

19 20 21 22 23 24 25 26 27 0.01 0.1 1

• FeXII

• FeXIII

• FeVII

• FeXIV
• FeVII

• FeXIX (2)

• FeVII

• Fe XXI (2)

• FeXVII

• FeXVI

• FeXVII

1s

2 2s 1/2-1s 2 2p 1/2

Intensity (arb. u.) Wavelength (nm)

1s

2 2s 1/2-1s 2 2p 3/2

Hinode ("sunrise") is a solar space telescope mission launched in 2006 (Japan with US and UK partners) aiming at investigating the Sun's corona

17.0 17.2 17.4 17.6 17.8 18.0 18.2 18.4 18.6

20 40 60 80 100

Intensity (counts)

Hinode EIS Instrument Young, Zanna et al. 2007

17 .0 17 .2 17 .4 17 .6 17 .8 18 .0 18 .2 18 .4 18 .6

5 0 10 0 15 0

Fe X Fe IX Fe VII Fe X Fe X Fe X Fe VII Fe VII Fe VII Fe X Fe XI Fe XI Fe X Fe XI Fe XI Fe XI Fe XI Fe X Fe VII Fe X Fe XI Fe VII Fe XII

Electron-driven resonant processes