An ion-trap setup for interaction studies of clusters with intense laser light [Elektronische Ressource] / Martin Arndt

An ion-trap setup for interaction studies of clusters with intense laser light [Elektronische Ressource] / Martin Arndt

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An ion-trap setup for interaction studies ofclusters with intense laser lightI n a u g u r a l d i s s e r t a t i o nzur Erlangung des akademischen Gradesdoctor rerum naturalium (Dr. rer. nat.)an derMathematisch-Naturwissenschaftlichen FakultätderErnst-Moritz-Arndt-Universität Greifswaldvorgelegt vonHerrn Martin Arndtgeboren am 05.02.1981in WolgastGreifswald, Juni 2011Dekan: Prof. Dr. Klaus Fesser1. Gutachter : Prof. Dr. Lutz SchweikhardErnst-Moritz-Arndt-Universität Greifswald2. Gutachter : Prof. Dr. Günter WerthJohannes Gutenberg-Universität MainzTag der Promotion : 5. Oktober 2011Für meine Eltern.Contents1 Introduction 12 Magnetron sputter cluster source 32.1 Magnetron sputter head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.1.1 Magnetron sputtering process . . . . . . . . . . . . . . . . . . . . . . . . 52.2 Aggregation chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.3 Quadrupole bender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.4 McLaren inline time-of-flight mass spectrometer . . . . . . . . . . . . . . . . . . 92.4.1 DesignandfunctionoftheMcLareninlinetime-of-flightmassspectrometer 102.4.2 Simulation and optimization of the McLaren inline time-of-flight massspectrometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112.5 Measurements with the magnetron sputter cluster source setup . . . . . . . . . 132.5.

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An ion-trap setup for interaction studies of
clusters with intense laser light
I n a u g u r a l d i s s e r t a t i o n
zur Erlangung des akademischen Grades
doctor rerum naturalium (Dr. rer. nat.)
an der
Mathematisch-Naturwissenschaftlichen Fakultät
der
Ernst-Moritz-Arndt-Universität Greifswald
vorgelegt von
Herrn Martin Arndt
geboren am 05.02.1981
in Wolgast
Greifswald, Juni 2011Dekan: Prof. Dr. Klaus Fesser
1. Gutachter : Prof. Dr. Lutz Schweikhard
Ernst-Moritz-Arndt-Universität Greifswald
2. Gutachter : Prof. Dr. Günter Werth
Johannes Gutenberg-Universität Mainz
Tag der Promotion : 5. Oktober 2011Für meine Eltern.Contents
1 Introduction 1
2 Magnetron sputter cluster source 3
2.1 Magnetron sputter head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1 Magnetron sputtering process . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Aggregation chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 Quadrupole bender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4 McLaren inline time-of-flight mass spectrometer . . . . . . . . . . . . . . . . . . 9
2.4.1 DesignandfunctionoftheMcLareninlinetime-of-flightmassspectrometer 10
2.4.2 Simulation and optimization of the McLaren inline time-of-flight mass
spectrometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.5 Measurements with the magnetron sputter cluster source setup . . . . . . . . . 13
2.5.1 Characterization of the ion transfer to the inline ToF-MS . . . . . . . . 14
2.5.2 Measurements for the calibration of the inline ToF mass spectrometer . 14
2.5.3 of the magnetron sputter cluster source . . . . . . . . . 16
3 Theory of linear Paul traps 23
3.1 Linear Paul traps operated with harmonic oscillating fields . . . . . . . . . . . . 24
3.1.1 Mathieu differential equations . . . . . . . . . . . . . . . . . . . . . . . . 24
3.1.2 Stability Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.1.3 Mass filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.1.4 Adiabatic approximation and pseudo potential . . . . . . . . . . . . . . 28
3.2 Linear Paul traps operated as DIT (Digital Ion Trap) . . . . . . . . . . . . . . . 29
3.2.1 Solving Hill’s differential equation with matrix-method . . . . . . . . . . 30
3.2.2 Stability diagram for the DIT . . . . . . . . . . . . . . . . . . . . . . . . 32
3.2.3 The DIT operated as mass filter with variable duty cycle . . . . . . . . . 34
3.2.4 The linear ion trap as TS-DIT (Three-State DIT) . . . . . . . . . . . . . 35
3.2.5 Higher stability regions for the TS-DIT in symmetric and asymmetric
operation mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.2.6 Fourier analysis of the symmetric and asymmetric TS-DIT signal . . . . 39
4 The mobile Paul trap setup and the femtosecond laser system 43
4.1 Vacuum system of the overall setup with connected crossed beam ion source . . 43
4.2 Crossed beam ion source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.3 Preparation trap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.4 Einzel lens 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.5 Measurement trap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.6 Radial MCP detector system . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
iContents
4.7 Acceleration section, pulsed cavity and einzel lens 2 . . . . . . . . . . . . . . . . 54
4.8 Channeltron detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.9 Femtosecond laser system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.10 Wiring, connected electronics and devices of the linear Paul traps . . . . . . . . 57
4.10.1 Description of how to create the RF potentials in the preparation trap . 57
4.10.2 of how to create the RF potentials in the measurement trap 59
4.11 Control system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
5 Simulations and calculations 65
5.1 Preparation trap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
5.1.1 Plate electrode shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
5.1.2 Radial ion stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
5.2 Measurement trap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
5.2.1 Trapping potential characteristics . . . . . . . . . . . . . . . . . . . . . . 70
5.2.2 Radial ion extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
5.2.3 Simulation of ion trapping in TS-DIT-mode . . . . . . . . . . . . . . . . 73
6 Characterization measurements 79
6.1 Preparation trap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
6.1.1 Operated with harmonic signals . . . . . . . . . . . . . . . . . . . . . . . 79
6.1.1.1 Trap parameter and stability diagram . . . . . . . . . . . . . . 84
6.1.2 Operated as DIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
6.1.2.1 Ion species selection by use of the duty cycle . . . . . . . . . . 86
6.1.2.2 Ion ejection with constant guiding field phase . . . . . . . . . . 89
6.2 Measurement trap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
6.2.1 Operated with harmonic signals . . . . . . . . . . . . . . . . . . . . . . . 90
6.2.2 Operated as TS-DIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
6.2.2.1 RF amplitude dependent ion storage . . . . . . . . . . . . . . . 91
6.2.2.2 Phase dependent ion injection into the measurement trap . . . 93
6.2.2.3 Ion transfer to and from the measurement trap . . . . . . . . . 95
7 First fullerene-cluster laser interaction measurements 99
8 Summary and Outlook 105
8.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
8.2 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
A Appendix 109
A.1 Further information for the Magnetron Sputter Cluster Source . . . . . . . . . . 110
A.2 Fourier analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
A.2.1 Fourier analysis of the DIT signal . . . . . . . . . . . . . . . . . . . . . . 112
A.2.2 Fourier of the TS-DIT signals . . . . . . . . . . . . . . . . . . . 113
A.3 Real shape of the TS-DIT signal . . . . . . . . . . . . . . . . . . . . . . . . . . 114
Bibliography I
Acknowledgements IX
iiList of Figures
2.0.1 Scheme of the magnetron sputter cluster source setup . . . . . . . . . . . . . . 4
2.1.1 Cut view of the whole magnetron sputter head . . . . . . . . . . . . . . . . . 5
2.1.2 Detailed cut view of the magnetron sputter head . . . . . . . . . . . . . . . . 6
2.1.3 Detailed cut view of the magnetron sputter head for the explanation of the
sputtering prozess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.1 Detailed cut view of the aggregation chamber . . . . . . . . . . . . . . . . . . 8
2.3.1 Top view of the quadruplole bender . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3.2 Simulation of the ion optics and the quadrupole bender . . . . . . . . . . . . . 9
2.4.1 Top view of the McLaren inline ToF acceleration unit . . . . . . . . . . . . . . 10
2.4.2 SIMION graphic of the McLaren inline ToF-MS with equipotential lines . . . 11
2.4.3 Simplex optimization of ToF-potentials and simulated ToF spectrum 12
2.4.4 Calculation of time that ions with different masses and kinetic energies need
to enter the first acceleration region . . . . . . . . . . . . . . . . . . . . . . . . 13
2.5.1 Mass spectra gained with the ToF-MS to optimize R and to determine amass
mass calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.5.2 Cluster transmission through the quadrupole bender dependent to the bender
potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.5.3 Pressure and aggregation length dependence of silver cluster cat- and anions . 18
2.5.4 Cluster size as a function of the argon flow and the plasma power . . . . . . . 19
2.5.5 Cluster size as a of the helium flow . . . . . . . . . . . . . . . . . . . 20
2.5.6 Four ToF spectra showing the dependence of the helium flow on the cluster size 20
3.0.1 Scheme of a quadrupole mass filter with hyperbolically shaped electrodes . . . 23
3.0.2 Quadrupole potential for radial ion confinement in a linear Paul trap . . . . . 24
3.1.1 Equipotential lines inside a linear quadrupole with hyperbolically shaped elec-
trodes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.1.2 Stability diagrams for thex-dimension and combined for thex-dimension and
y-dimension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.1.3 Stability diagram with the stability region I combined for thex-dimension and
the y-dimension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.1.4 Stability diagrams for three different masses illustrating the selection skills of
a mass filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.2.1 Sinusoidal and rectangular waveforms to operate a linear Paul trap . . . . . . 30
3.2.2 Stability diagrams for thex-dimension and combined for thex-dimension and
the y-dimension for the DIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.2.3 StabilitydiagramwithstabilityregionIforthex-dimensionandthey-dimension
for the DIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.2.4 Fourier analysis of a harmonic signal and the DIT signal . . . . . . . . . . . . 34
iiiList of Figures
3.2.5 Rectangular waveforms with variable duty cycles to perform mass filtering in
a DIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.2.6 Stability diagrams for the DIT in two dimensions with three values for the
duty cycle d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2.7 Scheme for introducing two signal forms to operate a linear Paul trap as TS-DIT 36
3.2.8 Stability diagrams for the symmetric and the asymmetric TS-DIT operation
mode with different d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37TS
3.2.9 Interdependence between q and d for both TS-DIT signal forms . . . 38max;TS TS
3.2.10 Stability diagrams for symmetric and asymmetric operation mode
with higher stability regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.2.11 Fourier spectra of symmetric and asymmetric TS-DIT signals for varying d 40TS
3.2.12 Sums of harmonics from the Fourier spectrum of asymmetric and symmetric
TS-DIT signal as a function of d . . . . . . . . . . . . . . . . . . . . . . . . 41TS
3.2.13 Continuous fourier spectra of the asymmetric signal and the symmetric signal
in 3D plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.1.1 Complete ion trap setup with crossed beam ion source . . . . . . . . . . . . . 45
4.2.1 Overall view of crossed beam ion source with Fullerene oven . . . . . . . . . . 47
4.3.1 Cut view of the preparation trap . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.3.2 Scheme for ion accumulation, storage and ejection in the preparation trap . . 49
4.3.3 Axial view of the preparation trap . . . . . . . . . . . . . . . . . . . . . . . . 51
4.4.1 Cut view of the einzel lens 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4.5.1 Setup of the measurement trap . . . . . . . . . . . . . . . . . . . . . . . . . . 53
4.5.2 Scheme of ion injection, storage and ejection in the measurement trap . . . . 54
4.7.1 Setup scheme of the acceleration section, the pulsed cavity and einzel lens 2 . 55
4.8.1 Photo of a Channeltron with conversion dynode . . . . . . . . . . . . . . . . . 56
4.9.1 Scheme for the guiding of the fs-laser beam through the preparation trap. . . 57
4.10.1 Scheme for operating the preparation trap as DIT . . . . . . . . . . . . . . . . 58
4.10.2 Scheme for op the measurement trap as TS-DIT . . . . . . . . . . . . . 60
4.11.1 Scheme of the control system (CS) and a scheme of the experimental cycles . 62
5.1.1 Influence of plate electrodes on the on axis potential in the preparation trap . 66
5.1.2 Influence of plate electrodes on the radial quadrupole potential in the prepa-
ration trap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
5.1.3 Axial aspired potential gradient and the resulting plate electrode shape . . . . 68
5.1.4 Axial potential minimum in preparation trap . . . . . . . . . . . . . . . . . . 69
+5.1.5 Simulated stability diagram for Ar ions in the preparation trap . . . . . . . 70
5.2.1 Quadrupole potential in the x-y-plane of the measurement trap . . . . . . . . 70
5.2.2 Form of axial ion trapping potential in thet trap . . . . . . . . . 71
5.2.3 Plot of the SIMION workbench presenting the radial ion extraction from the
measurement trap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
5.2.4 Simulation of radial ion extraction from the measurement trap . . . . . . . . . 73
5.2.5 Calculation of the fragment extraction time as a function of the kinetic energy
and field free time for different d and f . . . . . . . . . . . . . . . . . . . 74TS RF
5.2.6 Simulation of the RF phase and amplitude dependent ion trapping in the
measurement trap for the use of asymmetric TS-DIT signals . . . . . . . . . . 75
iv