storage-ring merged beams for electron-ion collision studies · with charged-particle beams...

IAEA Tech Meeting: Uncertainty Assessment and Benchmark Experiments onAtomic and Molecular Data for Fusion Applications

Vienna, 12-16 September 2016

Andreas Wolf

Storage-Ring Merged Beams forElectron-Ion Collision Studies

Method

Results: Open 4f-shell tungsten ions, HCl+

Developments: Cryogenic storage ring

Max-Planck-Institut für Kernphysik, Heidelberg, Germany

http://www.mpi-hd.mpg.de/ion-storage

Scattering and inelastic collisions with charged-particle beams

Atomic/molecular gas

Ion–molecule (atom) charge exchangeCrossed-beams electron impact

Low-energy electron scattering

Low-energyelectron source


Merged-beams electron impact


Scattering and inelastic collisions with charged-particle beams


Ion–molecule (atom) charge exchangeCrossed-beams electron impact

Low-energy electron scattering

Low-energyelectron source


Merged-beams electron impact Down to zero collision energy

Narrow energy spread

Extended overlap


Ion beam(in storage ring)

Overlap zoneInelastic collisions

Merged-beams electron ion collisions

Velocity-matched electron beamCollision energy: (v

e − v

i )2E

d = ½ m

e

~ 1 meV … keVWide scan range:






e − v

i )2E

d = ½ m

e


Charge changing reaction(photo-recombination)

Products:

Xq+ + e− → X(q−1)+ + γ






e − v

i )2E

d = ½ m

e


- Counting- Momentum measurement (time + position)- Coincidence measurements


Products:

Fragmentation(dissociative recombination)

AB+ + e− → A + B + ε

Xq+ + e− → X(q−1)+ + γ






e − v

i )2E

d = ½ m

e

~ 1 meV … keV

- Fragment mass identification

Wide scan range:

Fragments keep (approx.) the beam velocity v

i

→ Laboratory kinetic energyof fragment f:

Ef = ½ M

f v

i2

- Counting- Momentum measurement (time + position)- Coincidence measurements

Fragmentation(dissociative recombination)


Products:

AB+ + e− → A + B + ε

Xq+ + e− → X(q−1)+ + γ


Ion storage ringTSR

Molecularion beam

Electronbeam

Fragment detectors

Storage ring merged beams experiments

1988 to 2012

Max-Planck-Institutfür Kernphysik

Tandem accelerator (~ 10 MeV·q )

Molecule Van-de-Graaff (~ 1...2 MeV)


Ion storage ringTSR

Molecularion beam

Electronbeam

Fragment detectors

- Store and phase-space cool molecular ion beam- Reduce/control internal excitation of molecular ions (T

env = 300 K)

- Cold electrons (Te ~ 10 K) – vary collision energy of electrons

- Neutral fragment detection: ratesproduct momentaproduct masses

Storage ring merged beams experiments

1988 to 2012

Max-Planck-Institutfür Kernphysik

Tandem accelerator (~ 10 MeV·q )

Molecule Van-de-Graaff (~ 1...2 MeV)


Iron ion dielectronic recombination

F-like Fe17+

Feq+ + e → (Fe(q−1)+)** → (Fe(q−1)+)* + γ

2s22p5 (2P3/2

) → 2s2p6 nℓ

C-like Fe20+

2s22p2 (3P0) → 2s2p3 (SL

J) nℓ

→ 2s22p5 (2P1/2

) nℓ

D. Savin et al., Astrophys. J. Lett. 489, L115 (1997) D. Savin et al., Astrophys. J. Suppl. 147, 421 (2003)

Theory: T. Gorczyca et al., N. Badnell et al.

[ → 2s22p2 (SLJ) nℓ ]


0.1 1 10 100

0.1

1

10

100

Unpublished

Badnell, JPB (2006)

Badnell, APJ (2006)

mod.by Netzer,APJ (2004)

Arnaud & Raymond,APJ (1992)

Experiment Theory

collisionally-ionized

Fe13+

Rec

om

bin

atio

n r

ate

co

eff.

(1

0-1

0 cm

3 s-1)

Electron temperature (eV)

photo-ionized

Fe7+

Fe8+

E. W. Schmidt et al., Astrophys. J. Lett. 641, L157 (2006)

Al-like Fe13+

3s23p (2P1/2

)

→ 3s22p (2P3/2

) nℓ

→ 3s3p2 nℓ

Compiled byS. Schippers

Iron ion dielectronic recombination

Derived thermal plasma rate coefficients


Tungsten ions: merged beams rate coefficientsS. Schippers et al., PRA 83, 012711 (2011)

N. Badnell et al., PRA 85, 052716 (2012)

C. Krantz et al., J. Phys. B Topical Review(JPB acceptedaper link 2016)

Intermediate coupling calculation

Radiative recombination

Fully partitioned (statistical) calculation

Xe-like W20+

4d10 4f8 (7F6)

→ 4d9 4f9 nℓ

→ 4d10 4f9 5d nℓ

→ 4d10 4f9 5g nℓ

→ 4d10 4f8 (f.s.) nℓ

(0 … 30 eV)

W20+ [Kr]4d104f8


Tungsten ions: merged beams rate coefficientsW18+ [Kr]4d104f10

W19+ [Kr]4d104f9

W20+ [Kr]4d104f8

W21+ [Kr]4d104f7

S. Schippers et al., PRA 83, 012711 (2011)

K. Spruck et al., PRA 90, 032715 (2014)


K. Spruck, Thesis,Univ. of Giessen, 2015


C. Krantz et al., J. Phys. B Topical Review(JPB acceptedpaper link)

Stat. theor.V. A. Dzuba et al., PRA 86, 022714(2012).

~37%accuracy(90% conf.)incl. non-detectionof n > 69


Tungsten ions: plasma recombination rate constantsS. Schippers et al., PRA 83, 012711 (2011)

K. Spruck et al., PRA 90, 032715 (2014)



C. Krantz et al., J. Phys. B Topical Review(JPB acceptedpaper link)

~37%accuracy(90% conf.)@150 eV


W18+ [Kr]4d104f10

W19+ [Kr]4d104f9

W20+ [Kr]4d104f8

W21+ [Kr]4d104f7


Tungsten ions: excited ionic states

kBT = 560 eV

(for ion velocity in stripping target ~10 MeV W carbide anions)

+ 2468 other levels τ < 10 ms

W19+ [Kr]4d104f9 and 4d104f8 5s

Metastable levels


W19+ [Kr]4d104f9

Measurementtime in TSR

Storage time (s)

Fra

ctio

nal

leve

l po

pu

lati

on


Absolute normalization: the lifetime method

SH+ n

e ~ 3 × 106 cm−3

W18+ n

e ~ 1 × 107 cm−3

electronsoff

electronson

electronsoff

electrons on

Detuning energy Ed = 0

Electron induced loss rate r

Overlap fraction Le/C

Electron density ne

Reaction rate constantα = r /(n

e · overlap fraction)

H. B. Pedersen, Phys. Rev. A 72, 012712 (2005)O. Novotný, Astrophys. J. 777, 54 (2013)

K. Spruck et al., PRA 90, 032715 (2014)

A. Becker, Thesis,Univ. of Heidelberg, 2016


Molecular recombination measurements: Analysis

Calibration:Lifetime method

Merged-beams rate coefficient signal

O. Novotný, Astrophys. J. 777, 54 (2013)HCl+ + e → H + Cl + εkin



Effectiveenergy distribution

Intrinsic electron velocitydistribution

Overlap geometry

Binned signal contributions(fitted cross section values)

O. Novotný, Astrophys. J. 777, 54 (2013)

Tail frommerging geometry

HCl+ + e → H + Cl + εkin

Calibration:Lifetime method

Merged-beams rate coefficient signal



Binned cross section

O. Novotný, Astrophys. J. 777, 54 (2013)HCl+ + e → H + Cl + εkin



Maxwellian distribution

Plasma rate coefficient

O. Novotný, Astrophys. J. 777, 54 (2013)

~8% uncertainty

300 K internalion temperature !




Molecular recombination measurements: AnalysisO. Novotný, Astrophys. J. 777, 54 (2013)

Fit model for temperature curveof rate coefficient


Maxwellian distribution

Plasma rate coefficient

~8% uncertainty

300 K internalion temperature !



Internal rotational excitation

N = 12

3456

N = 1

2

34

56

Storage time (s)

Storage time (s)

Fra

ctio

n

Fra

ctio

n

Tenv

= 300 K

Tenv

= 10 K

Tsource

= 8000 K

Radiative relaxation only

(electron collisional effectsnot included)

Rotational populations in Π3/2

ground state of HCl+ ionsstored in vacuum

Measurementtime in TSR


±300 kV

2 K to 10 Kinner beam vacuum

Cryostat

Positive/negativeion sources

CSR laboratory

5 m

Neutral fragmentdetectors

MPI für Kernphysik, Heidelberg

Ion platform

2 K refrigerator

buffer gaspre-traps

mass filterelectrospray

Location for:

±60 kV

Merged neutral atom beam

Secondion source

H. KreckelASTROLAB

project

Photocathodeelectronbeam


CSR: Beam lifetime measurement by photodetachment

Ag2−

EA: 1.02 eV

60 keV Ag2

− + hν (1.9 eV) → Ag2 + e− (A = 216)

τ (20% laser) = 2074(21) sτ (40% laser) = 1676(18) s

τ (no laser) = 2717(81) s

~ 3 h

C. MeyerS. George

O. NovotnýC. Krantz

(MPIK)

Ag2

−

Ag2HeNe laser

chopped( 20% 40% )

~45 min1/e

R. von Hahn et al.,Rev. Sci. Instrum.87, 063115 (2016)

CH+ resonant photodissociationA. O'Connor et al., Phys. Rev. Lett. 116, 113002 (2016)

n < 140 cm−3

PRTE

< 5.8 × 10−15 mbar

Vacuum


Installation of the CSR merged electron beam

Storedion

beam

CSR cryostat~1 … 1000 eVelectron beam

Photocathode


Acknowledments – TSR

Stefan Schippers

Nigel Badnell

Oldřich Novotný

Claude Krantz

Alfred Müller

Manfred Grieser Daniel Savin

Kaija Spruck

CSR team

Collaborations CSR and experiments

CSR detectors, electron cooler, laser experiments

A. BeckerC. KrantzS. LohmannO. NovotnýS. SaurabhK. Spruck (Univ. Gießen)S. VogelP. WilhelmM. Rimmler

S. GeorgeC. Breitenfeldt (Univ. Greifswald)C. MeyerJ. GöckJ. KartreinP. Mishra

R. von HahnM. GrieserF. FellenbergerS. GeorgeM. LangeR. RepnowP. Herwig

C. KrantzS. VogelK. Spruck (Univ. Gießen)A. BeckerH. Kreckel (Astrolab)F. Grussie (Astrolab)A. O'Connor (Astrolab)

K. Blaum

WIS Rehovot (O. Heber, D. Zajfman)Univ. Greifswald (L. Schweikhard)Bar-Ilan Univ. (Y. Toker)Univ. Gießen (S. Schippers)Columbia Univ. (D. W. Savin)Univ. Louvain-la-Neuve (X. Urbain)Univ. Heidelberg, KIP (A. Fleischmann, C. Enss)Univ. Kaiserslautern (G. Niedner-Schatteburg)

and the MPIK workshops and labs

Acknowledgments – CSR

FundingMPGWIS

DFG Priority Program“Physics of the Interstellar Medium”

NASA and NSF (Columbia Univ.)

S. Schippers (Univ. Gießen)D. Schwalm (MPIK/WIS Rehovot)

Astrolab@CSRH. KreckelA. O'ConnorF. GrussieE. GuerinS. Kumar

ERC

S. Allgeier, C. Enss, A. Fleischmann, L. Gamer, D. Hengstler, S. Kempf, A. Pabiger, C. Pies

Microcalorimeter collaborators from Kirchhoff Inst. of Physics, Univ. Heidelberg:

MPIKC. D. SchröterR. MoshammerT. Pfeifer

storage-ring merged beams for electron-ion collision studies · with charged-particle beams...

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