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Diagnostic Equipment of High-current Pulsed Ion Beams

1. Faraday cup

2. Time-of-flight diagnostics

3. Thomson Parabola spectrometer

4. Thermal imaging diagnostics of powerful ion beams

5. Acoustic diagnostics

6. Pin-diode

7. Pin-diode

8. Measurement of ion beam divergence

9. Analysis of correctness of diagnostic of high current pulsed ion beam by ion current density

A. Pushkarev

Tomsk Polytechnic University, Russia

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For modification high-thermal conductivity materials we need to use ion beam with an energy density 2–5 J/cm2 and a pulse duration of not more than 100–150 ns. The increase in pulse duration leads to an increase in the heated layer thickness in a target with an inessential temperature increase.

Introduction

AHPIB

Melt region

Ion range

1-2 mkm

Ab

lati

on

pla

sma

Stress wave

Stress wave

107-108 К/с

1-5 J/cm2

3

Simulation of the temperature distribution along the depth for a copper target (Comsol Multiphysics program)

The temperature distribution in copper target irradiated with C+ ions at different times after

interception with the beam

Pushkarev A.I., Isakova Yu.I., Xiao Yu, Khailov I.P. Characterization of intense ion beam energy density and beam induced pressure on the target with acoustic diagnostics // Review of Scientific Instruments, 2013,  vol. 84, iss. 8, 083304 (2013)

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It is possible to increase ion beam energy density without increasing pulse duration:

1. By increasing the accelerating voltage U

However, along with ion generation an essential amount of electrons with the same energy is formed. With an electron absorption of energy over 500 keV, X-ray radiation increases rapidly and it is necessary to provide extra radiation shielding.

2. By increasing the ion current density Jion

With ion currents’ densities over 20 A/cm2 a collective effect appears, and full-load current is limited by their charge in the A-K gap. In this case, the ion current density is determined by the A-K gap and accelerating voltage.

Energy density of ion beam:

20

2/30

)(9

24

vtd

U

m

zJ

i

iion

anode cathode

dtJUq ionion

do

5

It is possible to obtain a high energy density of PIB in the target with the help of focusing of the ion beam and elimination of its scattering while drifting.

While ions are transferred to the focus their deviation from the initial path occurs due to:

Coulomb repulsion

Influence of electromagnetic fields,

Diffusive scattering, etc.

The influence of different instabilities and critical currents on the transfer of PIB is smaller than for the high-current electron beams because of the huge mass of charge carriers.

Jion 0.2 J/cm2

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Olson C.L. Ion Beam Propagation and Focusing // Journal of Fusion Energy, 1982

It is shown that magnetically insulated diodes have a rather small PIB divergence, amounting to 1–4, in contrast to reflex diodes and pinch-diodes.

Divergence angle ()

D

rarctg

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K. Yatsui, et all. Geometric focusing of intense pulsed ion beams from racetrack type magnetically insulated diodes // Laser and Particle Beams (1985)

Исследования выполнены на ускорителе ETIGO-1 (напряжение 1.2 MV, ток 240 kA, длительность импульса 50 ns, состав МИП - протоны).

Divergence angle ()

r - the focusing radius of the beam where one half of the total ion current,f - the focusing distance from the anode

D

rarctg

8K. Yatsui, et all. Geometric focusing of intense pulsed ion beams from racetrack type magnetically insulated diodes // Laser and Particle Beams (1985)

Sketch of shadow box. The aperture plate has 63 holes of 2-mm-diam./each

Damage patterns measured at z = 50 mm

Shadow-box measurement

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The angle basically depends upon three factors:

1. Local divergence angleThe local divergence angle originates from effects due to the presence of

knock pins on the anode, the temperature of the source plasma, inhomogeneity of magnetic field, or scattering processes (Humphries 1980a).

2. AberrationThe aberration arises from the fact that the direction of the beam acceleration

is not exactly directed towards. the focusing point due to an uneveness of the accelerating electrodes, an inhomogeneity of the anode plasma, etc

3. Space-charge effectThe space-charge effect also affects the focusing properties of the beam,

particularly in a high-current, relatively low-energy region.

The authors noted that PIB focusing diameter is, generally, determined by an aberration because of the heterogeneous thickness of the anode plasma and distortion of the electric field near the cathode. When the cathode geometry was changed, it decreased the divergence from 6 to 2.5

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H.A. Davis, R.R. Bartsch, J.C. Olson, D.J. Rej, and W.J. Waganaar. J. Appl. Phys. 82 (7), 3223 (1997).

With an accelerating voltage of 400 kV and pulse duration 0.5 µs the proton beam divergence amounted to 8.

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Furman, É., Stepanov, A. & Furman, N. (2007). Ionic diode. Technical Physics 52, 621.

divergence 4-5 Thermogram and energy density

distribution IIP focus. Horizontal and vertical cross section.

Spherical diode with self-insulation: 1 – calorimeter, 2 – active voltage divider, 3, 4, 8 Rogowski coils, 5 – loop for induction correction, 6 – anode, 7 – cathode, 9 – electron diode, 10 – pump

flange. Waveforms of diode voltage(1), diode current (2) and ion current(3) for diode with blade cathode and A-C gap of 10 mm

Bystritskii V.M., Glushko Yu.A., Kharlov A.V., Sinebryukhov A.A. Experiments on high power ion beam generation in self-insulated diodes // Laser and Particle Beams. – 1991. – Vol. 9. – № 3. – P. 691–698.

divergence 3°.

13Scheme diode assembly (1-grounded electrode, 2-potential electrode 3 Rogowski coil), the accelerating voltage waveform (4) and the total current of the diode (5)

4. Focusing IIP stripline focusing diode

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Photo diode and focusing the energy density distribution of IPI formed diode with a screen (1) and without a screen (2). Curve 3 - the original background of the target

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Thermograms IIP formed focusing diode

Дивергенция МИП уменьшилась с 11º до 7.5 - 8º.

без экрана с экраном

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The energy from the UIM energy supplied to the diode junction to the diode strip with screen and without screen

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Shadow-box measurement of divergence

9 holes2 mm

anodeanode

cathode

plate with holes

thermal paper

screen

thermal paper

thermal paper

divergence 2-3°.

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5. Фокусировка МИП, формируемого конусным диодом

Photo diode and a tapered accelerating voltage waveform (1) and the total current in the diode (2)

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Thermogram IIP tapered diode screen and the energy density distribution of IPI

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Diagnostic Equipment of High-current Pulsed Ion Beams

1. Faraday cup

2. Time-of-flight diagnostics

3. Thomson Parabola spectrometer

4. Thermal imaging diagnostics of powerful ion beams

5. Acoustic diagnostics

6. Pin-diode

7. Measurement of ion beam divergence

8. Analysis of correctness of diagnostic of high current pulsed ion beam by ion current density

A. Pushkarev

Tomsk Polytechnic University, Russia

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8. Analysis of correctness of diagnostic of high current pulsed ion beam by ion current density

In most papers devoted to surface modification of metal samples by intense ion beams, the ion beam parameters are controlled using ion current density waveforms

ABSTRACT: Anticorrosion behavior is an important factor for the reliability and durability of thermal barrier coatings (TBCs). Intense pulsed ion beam (ion species: 70% H++30% C+; current density: 150 A/cm2 and 250 A/cm2; accelerate voltage: 300 kV; pulse duration: 65ns) irradiation were used to improve the anticorrosion behavior of the Y2O3-stabilized ZrO2 (YSZ) /NiCoCrAlY thermal barrier coating. The anticorrosion property of the TBCs was evaluated with polarization curves method. A quite good result was obtained. Further analysis show that IPIB irradiation can seal the pores in YSZ layer, and block the penetration channels of corrosive fluid, therefore, improves the anticorrosion behavior.

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S. Yan, Y. J. Shang, X. F. Xu, X. Yi, X. Y. Le Improving anti-corrosion property of thermal barrier coatings by intense pulsed ion beam irradiation // Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 02/2012.

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Abstract In order to investigate the effect of processing parameters of high-intensity pulsed ion beam (HIPIB) on the performance of WC-Ni which contained 8% Ni (YWN8), four groups of parameters, with current densities of 100, 200 and 300 A/cm2 with one to five shots, were selected to irradiate the samples.

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V. S. Kovivchak, et al. Structural Phase Transformations in Tin Dioxide under the Action of a Nanosecond High-Power Ion Beam // Technical Physics Letters, 2013, Vol. 39, No. 11, pp. 982–985.

Abstract—Structural phase transformations in polycrystalline tin dioxide under the action of a nanosecond high-power ion beam with a current density of 50–150 A/cm2 are studied. It is found that the effect of a beam with a current density of 150 A/cm2 on SnO2 leads to the formation of submicron particles of tetragonal SnO with an average size of 210 nm on the exposed surface. The particles have a pronounced crystallographic facet pattern. Possible mechanisms of the observed transformations are discussed.

Fig. 3.Micrographs of the surface of SnO2 after exposure to a HPIB at j= 150 A/cm2 and n = 1. The inset shows a magnified image of SnO particles on the surface of SnO2 microparticles.

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I. P. Chernov et al. Physicomechanical Properties of the Surface of a Zirconium Alloy Modified by a Pulsed Ion Beam // Technical Physics, 2014, Vol. 59, No. 4, pp. 535–539.

Abstract—The physico-mechanical properties of the surface of the Zr–1% Nb zirconium alloy modified by a pulsed carbon ion beam with a pulse duration of 80 ns, an energy of 200 keV, and a current density of 120 A/cm2 are studied at four regimes having different numbers of pulses. Irradiation by a carbon ion beam results in hardening of the surface layer to a depth of 2 μm, grain refinement to 0.15–0.8 μm, zirconium carbide formation, and a decrease in the hydrogen permeability of the zirconium alloy.

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Action mechanism of PIB

AHPIB

Melt region

Ab

lati

on

pla

sma

Stress wave

Stress wave

107-108 К/с1-5 J/cm2

Ion current density 40-70 A/cm2 Pulse duration 100-150 ns

fluence (1.3-2.5)×1013 cm-2.

Trip of ions with energy of 200-300 keV in metals is 1-3 microns, concentration in the surface layer does not exceed 1017 cm-3.

Ion range

1-2 mkm

A significant factor affecting the properties of a treated specimen is the thermal effect of the beam, rather than ion implantation.

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This corresponds to ion fluence per pulse of (1.3-2.5) 1013 cm-2. Range of ions with energies 200-300keV in metals is 1-3 microns, and their concentration in the surface layer does not exceed 1017 cm-3.

In this case the energy density of ion beam is 3-5 J/cm2, and the main factor determining modification of sample surface properties is thermal effect and not the implantation of ions.

Therefore, for optimization of samples processing with ion beam it is important to measure the energy density of the beam and its distribution over the cross section.

1. Influence of a wide range of ion energy and complex element composition

Intense ion beam generated in a diode at pulsed accelerating voltage has a wide range of ion energy and complex element composition in the beam.

D

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Beam composition (time-of-flight diagnostic)

С+ (85-87)% H+ (13-15)%

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2. Influence of energetic neutrals

Some previous studies were looking into the formation of a large flux of energetic neutrals in the ion beam produced by magnetically insulated diodes with flashover anodes. The neutrals are produced though the effect of charge exchange between the ions and background neutrals in a gas layer onto the anode surface.

T.D. Pointon Charge exchange effects in ion diodes // J. Appl. Phys. 1989, vol. 66, No 7, p. 2879- 2887.

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Thermal imprint and energy density distribution in the focus.

2J/cm 3.4UJdtqUJ

• External insulation• single pulse mode

qIR = qUJ

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4. Ion beam energy density measurement. Double pulse mode

2J/cm 0.5 - 0.4UJdtqUJ

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3. Influence of changes in accelerating voltage

Generation of ion beam with current density more than 20 А/cm2 is accompanied by collective effects and ion flow is limited by space charge

In the space charge mode, in the nonrelativistic approximation, taking into account the expansion of the plasma emission surface, the ion current density is equal to :

20

2/30

][9

24)(J

tvd

U

m

zt

i

ion

where accelerating voltage; d0 initial A-C gap spacing; mi – ion mass; z – ion cahrge, v – plasma expansion speed

Increase in the ion current density by 2 times due to increase in accelerating voltage will cause an increase in energy density (at the same pulse width) by 2.8 times

Energy density of ion beam: dtJUq ionion

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4. Diagnostic locality

ions +electrons

N

S

B

Schematic of the strip diode with self-magnetic insulation and diagnostics: 1 - strip anode 2 - dielectric coating on the anode, 3 - anode Rogowski coil, 4 - strip cathode 5 – FC with magnetic insulation; 6 -

additional outlet, 7 - cathode Rogowski coil, 8 – targets; 9 – a place when electom beam breaks down, 10 – iaccelerator insulator 11 - DFL 12 - voltage divider

V.M. Bystritskii, A.N. Didenko, Y.E. Krasik, V.M. Matvienko. Plasma physics, 1985. v. 11, № 9. pp. 1057–1061.

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Signals from the sensors in self-insulation diode: 1 - voltage at the output of strip line; 2 – cathode current at the end of line; 3-5 - signals from FC installed along the length of the

diode at different points (3 - 4 cm, 4 - 31 cm, 5 - 60 cm)

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4. Additional energy impact of electrons

The electron density is (2.5-6)1012 cm-3.

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5. Correlation analysis of intense ion beam energy in a self magnetically insulated diode

The dependence of the total ion beam energy (a) and energy density (b) on the total charge transferred in the diode.Summary data is given for A-C gaps of 7, 8, 9, and 10 mm.

The correlation analysis of the ion current density with the diode parameters.

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A comparative analysis of systematic errors which occur during the interctions of action pulsed ion beams with a target (comparison between ion current density and energy density measuremtns) showed that the measurement of the energy density provides more accurate and complete information.

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Lecture 1. Ion beam generation in self-magnetically insulated diodePhysical principles of intense ion beam generation in self-magnetically insulated diode. Formation of dense plasma at the anode. Suppression of the electronic component of diode current. Ion current density enhancement.

Lecture 2. The TEMP-4M Ion beam generator.The TEMP-4M Ion beam generator construction (Marx generator, pulse forming line, diode). Diagnostic equipment of the TEMP-4M accelerator (Rogowski coil, voltage divider). Calibration of diagnostic equipment. Energy transfer in the generator.

Lecture 3. Intense ion beam diagnostics. Faraday cup. Time of Flight diagnostics of composition and energy spectrum of ion beam. Thomson Parabola spectrometer. Infrared imaging diagnostics of beam energy density distribution. Acoustic diagnostics. Pin-diode.