Charge exchange and spectroscopy with isolated
highly-charged ions
Nicholas D. Guise
Samuel M. Brewer, Joseph N. TanQuantum Measurement Division
National Institute of Standards and Technology
Gaithersburg, MD 20899
8 June 20128 June 20128 June 20128 June 2012
� GoalEngineer highly-charged ions (HCI) of interest in metrology, astrophysics, plasma diagnostics, and collision studies
� Basic Scheme1) Extract HCI from EBIT source2) Recapture in Penning trap3) Study recaptured ions
-charge exchange-optical spectroscopy
Overview
CX beam
ions
MCP detector
EBIT(electron beam ion trap)
fs comb
q/manalyzing magnet
ion trap laser
One-Magnet Trap• B field provided by one NdFeB magnet• Magnet also functions as ring electrode• Simple construction with copper endcaps
Two-Magnet Trap• B field more homogeneous near center• Holes in ring provide optical access• Iron electrodes shape field profile
Permanent Magnet Penning Traps
J.N. Tan, S.M. Brewer, and N.D. Guise, Rev. Sci. Instrum. 83, 023103 (2012)
XY Position Sensitive MCP Detector
Time-of-Flight MCP Detector (TOF), on retractable translator
2-MagnetPenning Trap
1-MagnetPenning Trap
PhotomultiplierTube
RF Trap/Lens/Filter
Experiment Region
TOF Detector:8 mm diameter<1 ns rise time
Ne10+ Beam Spoton Position-Sensitive MCP
t=0extract ions from EBIT
capt
ure
dump
t=tcapture ≈ 17 µspulse trap closed to capture ions
t=tstorage ≈ 200mspulse trap open to dump ions
t ≈ tstorage+1 µsions arrive at MCP detector
Ion Capture and Detection
Front Endcap Ring Back Endcap
EBIT MCP
ap
pli
ed
vo
lta
ge
Ion Extraction and Capture Timing
Ion Energy
Ion energy ~ 5.5 eV
Ion Charge Exchange
ParametersTwo-Magnet Trap
V0 ≈ 2.5 kV∆V=Vring-Vendcap = 25 V
Ne10+
only
sum of all charge states
charge state evolutionbare Ne nuclei
H-like Ne
bare Ne nuclei
H-like Ne He-like
Ne
He-like Ne
Ion Storage: Pressure Dependence
ParametersTwo-Magnet Trap
V0≈ 2.5 kV∆V=Vring-Vendcap = 25 V
Electron Probability Distribution
electron state: | n,l,m ›
nucleus: Ze+
|m|=l=n-1
• Theory more accurate than for Hydrogen S states due to:• negligible interactions with the nucleus• accuracy of calculated corrections, including
QED effects
• |n› → |n-1› transitions are accessible to optical frequency comb
U.D. Jentschura, P.J. Mohr, J.N. Tan, and B.J. Wundt,
Phys. Rev. Lett. 100, 160404 (2008).
Long-Term Focus: H-like ions in Circular
Rydberg States
New Apparatus for Low Charge States
Ion production region
Experiment region with two-magnet Penning trap
18 mm TOF detector
Electron gun
Summary
• Unitary architecture NdFeB Penning traps are used to capture andstore highly charged ions extracted from the NIST EBIT.
• Captured ion speciesinclude Ne10+, Ne9+, Ne8+, Ar16+, Ar15+, Ar14+,Ar13+, N7+, and Kr17+.
• Ion storage times of order 1 secondare limited primarily by collisionswith residual gas at 300 K.
• Ongoing experiments include studies of charge exchange, opticalmeasurements of metastable lifetimes(upcoming talk by S. Brewer).
• New apparatus will utilize similar NdFeB construction for a room-temperature “mini-EBIT” source, for planned spectroscopywith low-Zhydrogen-like ions.
