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CR39 nuclear track detector application for the diagnostics of low energy high power ion beams
Abstract
This report presents the investigation results of spectral composition of ion bemas generated by magneto-insulated ion diode of “MAC-M” accelerator. Energetical and mass characteristics of the accelerated ion beam were determined by Thomson spectrometer with CR-39 plate detector. Accelerated ion energy was from 40 up to 240 keV. Mass composition contained hydrohen, nitrohen and carbon ions. The individual track analysis shows the track form, depth and diameter dependence on ion mass and energy.
A high-current pulsed accelerator, producing ion beams with a current density of 4-20 A/cm2, an energy of 30-150 kV/n (n is the ion charge), a beam cross-section area of 180 cm2, and a pulse repetition frequency of up to 10 Hz, is described. The accelerator comprises a high-voltage (300 kV) pulse transformer, a nanosecond generator using low-ohmic cables capable of producing two voltage pulses of arbitrary polarity, and a magnetically insulated diode. The first nanosecond voltage pulse forms an explosion-emission plasma at the anode surface, and the following nanosecond pulse accelerates the ions. Performance of the accelerator is illustrated by data on the production of hydrogen, carbon, and aluminum ion beams.
By applying an after acceleration electric field, the detection and registration of the ion species and spectral distribution of low energy ion beams (≪1 keV) have been achieved by the Thomson spectrometer with CR-39 nuclear track detector as detection plate. With the use of this modified spectrometer, the low energy and high energy density plasma ion beams generated by a coaxial plasma gun have been detected and investigated. The ion beams were mainly N + ions and were distributed in the energy range from E∼0.12 to 0.4 keV. © 1997 American Institute of Physics.
The response of a CR-39 track detector to ion beams was examined for the purpose of diagnosing low-energy heavy ion beams. The effect of a low-energy heavy ion beam on the CR-39 track detector is limited to its top surface, which means that a careful and quick treatment is necessary for the chemical etching process of ion-irradiated track detectors. It was found that the optimal etching time almost agreed with that estimated from calculations on the ion range and the V function concerning the track etch rate. The outline of a thin Ar+ beam was successfully measured up to about 10μm in diameter in the energy range from 20 to 200keV.
Two sources of high-power ion beams of nanosecond duration are described, a MUK and a TEMP unit They generated ions with energies of up to 150 and 300 keV, respectively, and the pulse duration was 20–200 and 50 ns, respectively. For the MUK unit, beam parameters for heavy ion implantation (Aln+, Mgn+, Fen+, Wn+, etc.) were as follows: current density ranging from 1 to 10 A cm−2 and total ion flux energy up to 20 J. For the TEMP unit, the following beam parameters were used for H+ and Cn+ ions: current density 40–200 A cm−2 and total ion flux energy 0.3–0.5 kJ. The sources are powered by various diode systems and can be applied in material science for scientific research and technology.
Our work is dedicated to research on dense plasma generation using explosive electron emission with desired plasma composition directly in the diode. The first (negative) high-voltage pulse being applied to the potential electrode of the diode (subsequently called anode) serves for plasma formation. The second (positive) pulse serves for the acceleration. These pulses are produced by nanosecond generator and considered as one shot. During delay between these two pulses the plasma spreads from anode to cathode. So when the accelerating voltage pulse arrives the plasma in the anode-cathode gap already exists
The short-pulse high-current implanter with the flow of charged cpecies 10 13 −5.10 13 species/cm2 in the pulse end with rate of doze in the target up to 5.10 14 ions/cm2.sec, is developed. The strip line magneto-insulated diode is ion source. This implanter is developed on the base of MA C accelerator by means of replacement of Marx-generator by the high voltage pulse transformer with output voltage up to 300 k V, as well as by means of the some other MA C units' modification. The implanter has parameters as following: ion energy - up to 150ke V, ion current density - from 10 to 30 A/cm2, pulse duration - from 50 to 200 ns, pulse frequency - 10 Hz, ion kind - H+, Cn+.
We tried reduction of low energy components in pulse ion beams with self-crowbar switch of which operation was achieved by expansion of electrode plasmas in a small MITL. The experiments were carried out with the small MITL (self-crowbar switch) and the “Inverse Pinch Ion Diode”. From the experimental results, the times required for dropping of pulse high voltage were shortened from 40 to 15 ns. As the result of this shortening, the ions accelerated at a relatively low voltage decreased, and the energy ranges of proton beams were reduced from 60 to 30 keV.
This report describes two sources of high power ion beams of nanosecond duration. The first one produces ions with energy up to 125 keV, pulse duration from 20 to 200 ns, current density for heavy ions (Al+, Mg+, Fe+, W+, etc.) 1–2 A cm−2 and energy of 12 to 120 J deposited by the beam. The second one produces, respectively, 300 keV, 50 ns, 40 to 200 A cm−2 current of H+ and C+ ions and a kJ energy. The sources are powered by various diode systems and can be applied to scientific research and technology for materials science.