An all-solid state laser system for the laser ion source RILIS and in-source laser spectroscopy of astatine at ISOLDE,CERN

This doctoral thesis describes the extension of the resonance ionization laser ion source RILIS at CERN/ISOLDE by the addition of an all-solid state tunable titanium:sapphire (Ti:Sa) laser system to complement the well-established system of dye lasers. Synchronous operation of the so called Dual RILIS system of Ti:Sa and dye lasers was investigated and the potential for increased ion beam intensity, reliability, and reduced setup time has been demonstrated. In-source resonance ionization spectroscopy was performed at ISOLDE/CERN and at ISAC/TRIUMF radioactive ion beam facilities to develop an efficient and selective three-colour ionization scheme for the purely radioactive element astatine. A LabVIEW based monitoring, control and measurement system was conceived which enabled, in conjunction with Dual RILIS operation, the spectroscopy of high lying Rydberg states, from which the ionization potential of the astatine atom was determined for the first time experimentally.

MeV negative ion source from ultra-intense laser-matter interaction

Experimental demonstration of negative ion acceleration to MeV energies from sub-micron size droplets of water spray irradiated by ultra-intense laser pulses is presented. Thanks to the specific target configuration and laser parameters, more than 109 negative ions per steradian solid angle in 5% energy bandwidth are accelerated in a stable and reliable manner. To our knowledge, by virtue of the ultra-short duration of the emission, this is by far the brightest negative ion source reported. The data also indicate the existence of beams of neutrals with at least similar numbers and energies.

Ethanol (C2H5OH) spray of sub-micron droplets for laser driven negative ion source

Liquid ethanol (C₂H₅OH) was used to generate a spray of sub-micron droplets. Sprays with different nozzle geometries have been tested and characterised using Mie scattering to find scaling properties and to generate droplets with different diameters within the spray. Nozzles having throat diameters of 470 µm and 560 µm showed generation of ethanol spray with droplet diameters of (180 ± 10) nm and (140 ± 10) nm, respectively. These investigations were motivated by the observation of copious negative ions from these target systems, e.g., negative oxygen and carbon ions measured from water and ethanol sprays irradiated with ultra-intense (5 × 1019 W/cm2), ultra short (40 fs) laser pulses. It is shown that the droplet diameter and the average atomic density of the spray have a significant effect on the numbers and energies of accelerated ions, both positive and negative. These targets open new possibilities for the creation of efficient and compact sources of different negative ion species.

Coupling of LMS with a fs-laser ablation ion source: elemental and isotope composition measurements

Mass spectrometric analysis of elemental and isotopic compositions of several NIST standards is performed by a miniature laser ablation/ionisation reflectron-type time-of-flight mass spectrometer (LMS) using a fs-laser ablation ion source (775 nm, 190 fs, 1 kHz). The results of the mass spectrometric studies indicate that in a defined range of laser irradiance (fluence) and for a certain number of accumulations of single laser shot spectra, the measurements of isotope abundances can be conducted with a measurement accuracy at the per mill level and at the per cent level for isotope concentrations higher and lower than 100 ppm, respectively. Also the elemental analysis can be performed with a good accuracy. The LMS instrument combined with a fs-laser ablation ion source exhibits similar detection efficiency for both metallic and non-metallic elements. Relative sensitivity coefficients were determined and found to be close to one, which is of considerable importance for the development of standard-less instruments. Negligible thermal effects, sample damage and excellent characteristics of the fs-laser beam are thought to be the main reason for substantial improvement of the instrumental performance compared to other laser ablation mass spectrometers.

Characterization of compact ICP ion source for focused ion beam applications

A compact, high brightness 13.56 MHz inductively coupled plasma ion source without any axial or radial multicusp magnetic fields is designed for the production of a focused ion beam. Argon ion current of density more than 30 mA/cm(2) at 4 kV potential is extracted from this ion source and is characterized by measuring the ion energy spread and brightness. Ion energy spread is measured by a variable-focusing retarding field energy analyzer that minimizes the errors due t divergence of ion beam inside the analyzer. Brightness of the ion beam is determined from the emittance measured by a fully automated and locally developed electrostatic sweep scanner. By optimizing various ion source parameters such as RF power, gas pressure and Faraday shield, ion beams with energy spread of less than 5 eV and brightness of 7100 Am(-2)sr(-1)eV(-1) have been produced. Here, we briefly report the details of the ion source, measurement and optimization of energy spread and brightness of the ion beam. (C) 2010 Elsevier B.V. All rights reserved.

Research on Dynamic Micro-Deformation under Laser Point Source

The dynamic micro-deformation of the specimen under laser point source is measured using a laser beam reflex amplifier system and numerically simulated by Msc.Marc software. Compared with experimental result and calculated result, the final deformation direction of the specimen depends on the result of the thermal strain and the phase transformation strain cooperation, away from the laser beam or towards the laser beam, the final deformation angle depends on temperature gradient in the thickness direction and the geometry constraint of the specimen. The conclusion lays the foundation for further research on the mechanism of laser bending. At the same time, it is proposed that the model of calculation based on classical Fourier heat transfer theory cannot be enough to simulate the dynamic micro-deformation of the specimen under laser point source, the model of calculation should be modified in the future.

10 Gbit s(-1) electroabsorption-modulated laser light-source module using selective area MOVPE

A distributed-feedback (DFB) laser and a high-speed electroabsorption (EA) modulator are integrated, on the basis of the selective area MOVPE growth (SAG) technique and the ridge waveguide structure, for a 10 Gbit s(-1) optical transmission system. The integrated DFB laser/EA modulator device is packaged in a compact module with a 20% optical coupling efficiency to the single-mode fibre. The typical threshold current is 15 mA, and the side-mode suppression ratio is over 40 dB with the single-mode operation at 1550 nm. The module exhibits 1.2 mW fibre output power at a laser gain current of 70 mA and a modulator bias voltage of 0 V. The 3 dB bandwidth is 12 GHz. A dynamic extinction ratio of over 10 dB has been successfully achieved under 10 Gbit s(-1) non-return to zero (NRZ) operation, and a clearly open eye diagram is obtained.

Electroabsoorption-modulated laser light-source module using selective area growth for 10 Gb/s transmission

In this work, a novel light source of strained InGaAsP/InGaAsP MQW EAM monolithically integrated with DFB laser is fabricated by ultra-low-pressure (22 x 10(2) Pa) selective area growth ( SAG) MOCVD technique. Superior device performances have been obtained, sue h as low threshold current of 19 mA, output light power of about 7 mW, and over 16 dB extinction ratio at 5 V applied voltage when coupled into a single mode fiber. Over 10 GHz 3 dB bandwidth in EAM part is developed with a driving voltage of 3 V. After the chip is packaged into a 7-pin butterfly compact module, 10-Gb/s NRZ transmission experiments are successfully performed in standard fiber. A clearly-open eye diagram is achieved in the module output with over 8.3 dB dynamic extinction ratio. Power penalty less than 1.5 dB has been obtained after transmission through 53.3 km of standard fiber, which demonstrates that high-speed, low chirp EAM/DFB integrated light source can be obtained by ultra-low-pressure (22 x 102 Pa) SAG method.