Microsecond pulse width, intense, light-ion beam accelerator

Review of Scientific Instruments, 2012

An overview of the last experimental campaigns on laser-driven ion acceleration performed at the PALS facility in Prague is given. Both the 2 TW, sub-nanosecond iodine laser system and the 20 TW, femtosecond Ti:sapphire laser, recently installed at PALS, are used along our experiments performed in the intensity range 10 16 −10 19 W/cm 2 . The main goal of our studies was to generate high energy, high current ion streams at relatively low laser intensities. The discussed experimental investigations show promising results in terms of maximum ion energy and current density, which make the laser-accelerated ion beams a candidate for new-generation ion sources to be employed in medicine, nuclear physics, matter physics, and industry.

2003

The paper deals with experiments on generation and transport of a low energy (60-100 keV), high density (10 -30 A/cm 2 ), microsecond ion beam (IB) generated in a magnetically insulated diode (MID) with an active hydrogenpuff ion source. The convergent annular IB was initially ballistically focused then transformed into a paraxial cylindrical shaped beam and transported in vacuum to a distance > 1 m with high efficiency using a combination of a concave toroidal magnetic lens and a straight solenoid. 2D one-particle computer simulations of the IB propagation in the lens/solenoid system supported the optimization of the system parameters.

Review of Scientific Instruments, 1993

A plasma source based on an inductive breakdown of a supersonic gas puff is described. The source was developed to provide an anode plasma for an annular, extraction geometry, magnetically insulated ion diode. In this source, plasmas with densities of 1013 cm−3 were generated and accelerated to velocities of 20–30 cm/μs; plasma fluxes of 10–40 A/cm2 were obtained. Operating the source under the diode insulating field effect, plasma fluxes above 100 A/cm2 were observed. When the plasma source was used in conjunction with a magnetically insulated diode gap, intense ion beams with proton fluxes of more than 100 A/cm2, energies of 100 keV, and beam pulses longer than 1 μs were extracted.

Journal of Applied Physics, 1980

Experiments are described pertaining to the development of very high-current pulsed linear ion accelerators utilizing electron neutralization. A novel magnetically insulated gap using radial magnetic fields has been tested. It provides stable electron cloud confinement over microsecond time scales with no detectable leakage current. The gap can act as an ion injector when used in conjunction with a plasma source. Control of the electron cloud dynamics allows the injector to operate in an enhanced current density mode (10–50 times the Child-Langmuir limit) with high efficiency and with plasma source control of the current flow. Currents up to 20 kA at 100 kV applied voltage resulted when using a light-ion flashboard plasma source. Carbon beams were produced by extraction from a flowing plasma from a gun array. A 3-kA beam with equal fractions of C+ and C++ was extracted over a microsecond time scale with little proton contamination. The use of active plasma injection into the high-in...

2006

A high current, mixed ion electron flux with space charge compensation has been produced without using a traditional dedicated source of space charge neutralizing electrons. The source employs a dual stage discharge and extraction concept. The main gas discharge plasma was generated in the cavity of a hollow cathode, representing a non self sustained glow discharge supported by electrons injected from the plasma of an auxiliary glow discharge. An ion beam was extracted from the plasma of the main discharge by a single grid extractor. Beam ions were later decelerated to a required energy in the layer between the grid and the beam plasma. The ion beam current was measured using a collector located 30-60 cm away from the dischar ge system. For the electron component of the main dischar ge plasma to penetrate into the ion beam drift space through the grid, the potential barrier was reduced under the condit ions of the optimal extractor potential with respect to the hollow cathode. The space charge neutralization of the low energy ion beam lead to a decrease in the plasma potential in the drift space and an increase in ion beam current. At a main discharge current of 1 A and a main discharge voltage of 300 V, an ion beam current of up to 100 mA and an ion en ergy of 20-100 eV was obtained. An increase in the distan ce between the collector and the discharge system necessita ted a corresponding increase in the initial ion energy if the ion beam current needed to be kept constant. The formation of an ion beam with the desired energy was confirmed by ti me of flight measurements.

Review of Scientific Instruments, 2004

Computer simulation codes for the extraction of ion beams have been used for over three decades. Here we describe medium current extraction ͑ϳ1 mA͒ from a high density plasma source (Ͼ10 12 cm Ϫ3) with a three electrode extraction system and compare the extracted current and the angular divergence with the results of two computer simulation programs. The first is called PBgun and is a commercially available ray tracing code; the second, called simulation d'extraction de faisceaux d'ions ͑SEFI͒ uses a particle-in-cell code to simulate the plasma and ion beam. It is the purpose of this article to ascertain whether these codes can adequately model the plasma/beam interface and hence successfully predict the extracted current and beam form across a broad range of extraction parameters. We found that SEFI could accurately predict the function of extracted current versus extraction voltage and that PBgun gave accurate simulations when the current or current density could be specified near the meniscus. Also for a thin plasma aperture and a fixed current at the meniscus, PBgun gave roughly 60% of the functional dependence of the extracted current on the extraction voltage and the other 40% on variations in the plasma pre-sheath. Both codes had some error from beam crossing near the axis which changed the amount of meniscus curvature predicted.

2012

UltraCold Ion Beam Source. Focused ion beam (FIB) machines are largely used in the semiconductor industry mainly for imaging, milling and deposition of material, at the nanometer scale. To keep up with the trend of making smaller and smaller components, FIBs need to be continuously improved. A FIB is mainly made of an ion source and a focusing column. In this thesis, two concepts of ion sources are presented, modeled and discussed. The ultra-cold ion source (UCIS) is based on creating very cold ion beams (T <1 mK) by near-threshold photo-ionization of a laser-cooled and trapped atomic gas. In our experiment, 85Rb atoms are confined in a magneto optical trap built directly inside an accelerator structure. A spherical portion of the atom cloud is ionized with a 2-step ionization process and the bunched ions are accelerated by either a DC or a pulsed electric field. The liquid-metal ion source (LMIS) is the current state-of-art for focused ion beam technology, having a reduced brigh...

2003

This article presents the construction of a fast, intense electron beam generator, several of its operational properties and its preliminary applications. A fast filamentary discharge produced in a tube filled with Argon gas at pressure of about 0.1 torr. An electron beam is obtained with a current intensity of about 0.6 A for a 25 ns duration. The length of the filamentary discharge and the behavior of the beam in the magnetic field are examined. The interaction of the beam with different targets was investigated by Scanning Electron Microscope. It is also demonstrated that the device can be used to drill holes of several tens of microns in diameter and it can be used for material coating.

2002

We present the results of a study on the acceleration of intense ion beams from solid targets irradiated with laser intensities up to 5xl0 19 W/cm 2. A strong dependence of the ion beam parameters on the conditions on the target conditions and laser parameter was found. The ion beam characteristic revealed a highly laminar acceleration and an excellent beam quality superior to that from conventional accelerators. We succeeded in shaping the ion beam by the appropriate tailoring of the target geometry and we performed a characterization of the ion beam quality. The production of a heavy ion beam could be achieved by suppressing the amount of protons at the target surfaces. Finally, we demonstrated the use of short pulse laser driven ion beams for radiography of thick samples with high resolution. CP634, Science of Superstrong Field Interactions, edited by K. Nakajima and M. Deguchi

Laser ion sources offer the possibility to get ion beams utilizable to improve particle accelerators. Today many laboratories, as well as the LEAS, are involved to develop accelerators of very contained dimensions, easy to be installed in little laboratories and hospitals. Pulsed lasers at intensities of the order of 10 8 W/cm 2 and of ns pulse duration, interacting with solid matter in vacuum, produce plasma of high temperature and density. The charge state distribution of the plasma generates high electric fields which accelerate ions along the normal to the target surface. The energy of emitted ions has a shifted Maxwell-Boltzmann distribution which depends on the ion charge state. To increase the ion energy, a postacceleration system can be employed by means of high voltage power supplies of about 100 kV. The post acceleration system results a good method to obtain high ion currents using a not expensive system and the final ion beams find interesting applications in the field of the ion implantations, hadrontherapy, scientific applications and industrial use. In this work we study the electromagnetic and geometric properties, like the emittance of the beams delivered by Cu target. Plasma"s characterization was performed using a Faraday cup for the electromagnetic characteristics, while for the geometric ones by adopting a pepper pot system. Applying 60 kV of accelerating voltage and a laser irradiance of 0.1 GW/cm 2 , we obtain 5.5 mA of output current and a normalized beam emittance of 0.2 π mm mrad. The brightness of the beams was 137 mA(p mm mrad) -2 .