Professor Ric Allott will introduce the the Science and Technology Facilities Council (STFC), and their expertise and capabilities across their 3 main campuses and the potential benefits of working with the SFTC. The talk will focus on 3 key areas of STFC: our Large Scale Facilities (x-rays, neutrons and lasers), High Performance Computing and Data Analytics and Technology. Professor Ric Allott will end with details on how to engage with the SFTC and access our facilities, technologies, scientists and engineers
Point-like sources of X-rays that are pulsed (sub nanosecond), high energy (up to several MeV) and bright are very promising for industrial and security applications where imaging through large and dense objects is required. Highly penetrating X-rays can be produced by electrons that have been accelerated by a high intensity laser pulse incident onto a thin solid target. We have used a pulse length of ~10ps to accelerate electrons to create a bright x-ray source. The bremsstrahlung temperature was measured for a laser intensity from 8.5-12×1018 W/cm2. These x-rays have sequentially been used to image high density materials using image plate and a pixelated scintillator system.
Laser micromachining by ablation is an established technique for the production of 2.5D and 3D features in a wide
variety of materials. Mask projection techniques using excimer lasers have been used to fabricate microstructures on
large panels where diamond turning and reflow techniques have reached their limits. We have developed 3D structuring
tools based upon UV laser ablation of polymers to create large arrays of repeating micro-optical features.
Synchronization of laser pulses with workpiece movement allows layer-by-layer growth of deep structures with
outstanding repeatability. Here, we show recent developments in laser structuring with the combination of half-tone and
binary mask techniques. Significant improvements in surface quality are demonstrated for a limited range of structures.
Fiber delivery of intense laser radiation is important for a broad range of application sectors, from medicine through to industrial laser processing of materials, and offers many practical system benefits relative to free space solutions. In recent years, photonic crystal fiber technology has revolutionized the dynamic field of optical fibers, bringing with them a wide range of novel optical properties that make them ideally suited to power delivery with unparalleled control over the beam properties. The DTI funded project: Photonic Fibers for Industrial beam DELivery (PFIDEL), aims to develop novel fiber geometries for use as a delivery system for high power industrial lasers and to assess their potential in a range of "real" industrial applications. In this paper we review, from an industrial laser user perspective, the advantages of each of the fibers studied under PFIDEL. We present results of application demonstrations and discuss how these fibers can positively impact the field of industrial laser systems and processes, in particular for direct write and micromachining applications.
Pulsed laser sources are widely used for the micro-processing of materials from the structuring and patterning of surfaces to the direct machining of devices. This paper discusses laser micro-processing techniques for the fabrication of microstructures with high accuracy and precision. Techniques discussed include laser mask projection techniques and direct beam micromachining using galvo-scanners and high precision motion stages, with a variety of different lasers. Examples of the application of these techniques to the manufacture of MEMS and MOEMS devices are discussed.
A novel laser micro-machining technique to produce high density micro-structures called Synchronized Image Scanning (SIS) was introduced a couple of years ago. Over this period of time, the technique was refined in a major effort to meet the needs of various industries.
There is an increasing demand for micro-structuring of large and super large area optical films, e.g. for Rear Projection TV, anti counterfeit packaging material and 3D displays. Especially in the display industry, where the screens are ever increasing in size, established micro-structuring methods like e-beam milling, diamond turning or the reflow technique struggle to keep up with the development.
This paper explains how it is possible to direct laser etch hundreds of millions of lenses into a 2 m x 1.5 m substrate. It looks at the advances made in SIS in recent years regarding seam reduction, overall accuracy and precision when structuring super large area optical films, and it presents the tools and subsystems needed to generate the features in those films. Furthermore, the potential of this exciting laser micro-machining technique for rapid prototyping for all sorts of optical and non-optical structures is mapped out.
Two new laser mask projection techniques Synchronized Image Scanning (SIS) and Bow Tie Scanning (BTS) have been developed for the efficient fabrication of dense arrays of repeating 3D microstructures on large area substrates. Details of these techniques are given and examples of key industrial applications are shown.
The Vulcan Nd:glass laser facility at RAL delivers up to 100TW 0.8 ps from its ultra-short pulse beamline and up to 2.5kJ in 8 beams in 'long pulse' mode. It runs parallel operations to two target areas fora wide ranging science program for UK university and EU researchers and their collaborators. In March 1999, funding was awarded by the Engineering and Physical Sciences Research Council for the upgraded of Vulcan's ultrashort beam lie to 1PW as the first phase of a major enhancement program.
Ne-like and Ni-like ions have been pumped in the transient gain regime using intense picosecond pump pulses from Vulcan in its CPA mode. High gain coefficients of at least approximately 30/cm are observed for the Ne-like ions Ti XIII, Ge XXIII and Sn XXIII at wavelengths 31.2, 19.6 and 12.0 nm respectively and approximately 20/cm for the Ni-like ion Sm XXXV at 7.3 nm. Saturated output is found in all cases for target lengths shorter than 10 mm and the effect of traveling wave pumping has been studied and unequivocably demonstrated. An experimental campaign to observe four wave mixing using a soft x-ray laser and an optical laser in a sum-difference frequency mixing scheme has been initiated. Preliminary results are described and future directions discussed.
Saturated operation of an X-ray laser is desirable as a high output irradiance is obtained with reduced shot-to-short variation. The potential of saturated X-ray laser output in probing plasma samples is first investigated. The laser pumping requirements to scale Ni-like saturated X-ray laser output to shorter wavelengths is then analyzed using published atomic physics data and a simple 4-level laser model for gain. A model of amplified spontaneous emission has been modified to accurately predict experimentally observed saturation behavior obtained in different experiments at the Rutherford Appleton Laboratory. In particular, the effects of traveling wave pumping with short duration (approximately 1 ps) laser pulses are investigated. Simulations of Ne-like Ge resonance line emission are compared to experimentally measured spectra.
David Neely, Colin Danson, Ric Allott, F. Amiranoff, E. Clark, Chris Clayton, J. Collier, A. Dangor, A. Djaoui, Christopher Edwards, P. Flintoff, Daniel Gordon, P. Hatton, Mark Harman, M. Hutchinson, K. Krushelnick, G. Malka, Victor Malka, A. Modena, Z. Najmudin, David Pepler, Ian Ross, M. Salvati, M. Santala, M. Tatarakis, M. Trentelman, T. Winstone
Frequency doubling a large aperture sub ps, chirped pulse amplified (CPA) 1053 nm beam for laser matter interaction studies was investigated at the Central Laser Facility. Efficiencies > 50 percent were achieved using a 4 mm thick KDP crystal to convert a 140 X 89 mm 700 fs beam. Measurements of the 527 nm beam's focal spot quality when the doubling crystal was driven at high intensities 200 GWcm-2 are presented. Using data from 2 and 4 m thick 25 mm diameter test crystals, the optimum crystal thickness in terms of conversion efficiency is reviewed for 1053 nm CPA systems in the 0.3-3 ps region and options for fourth harmonic production discussed.
Colin Danson, Ric Allott, S. Angood, G. Booth, J. Collier, A. Damerell, Christopher Edwards, P. Flintoff, J. Govans, S. Hancock, P. Hatton, S. Hawkes, M. Hutchinson, Michael Key, C. Hernandez-Gomez, John Leach, W. Lester, David Neely, Peter Norreys, M. Notley, David Pepler, C. Reason, D. Rodkiss, Ian Ross, W. Toner, M. Trentelman, J. Walczak, R. Wellstood, T. Winstone, R. Wyatt, B. Wyborn
There has been considerable interest in the last 10 years in the physics of ultra-high power laser interactions. With all high power lasers such as Vulcan there is a limit to the energy that can be extracted from laser amplifiers at short pulse-lengths due to the intensity dependent non-linear refractive index. The technique of Chirped Pulse Amplification has overcome the classic limit and has resulted in massive increases in focused intensity. The large increase in on target intensity is achieved by a substantial, usually orders of magnitude, reduction in pulse duration while at the same time maintaining comparable pulse energy and focusability.
An electron-tubes-LTD 129EM electron multiplier tube has been modified to act as a detector of soft x-rays. the first dynode was coated with 100 nm of CsI and the assembly was mounted in a small vacuum chamber with 100 nm thick silicon nitride entrance window. Initial tests show the detector is linear up to an input flux of approximately 1MHz on a synchrotron source and has proved effective in providing pulse height discrimination when used on a pulsed laser plasma source.
A picosecond excimer laser-plasma source has been constructed which generates an x-ray average power of 2.2 Watt and 1.4 Watt at the wavelengths required for proximity x-ray lithography: 1.4 nm (steel target) and 1 nm (copper target), respectively. The plasma source could be scaled to the 50 - 75 W x-ray average power required for industrial lithographic production by scaling the total average power of the commercial excimer laser system up to 1 kW. The 1 nm x-ray source is used to micromachine a 2.5 THz microwave waveguide-cavity package with a 48 micrometers deep, 3D structure, using the LIGA technique.
An overall approach into the differential investigation of membrane/cytoplasm related metabolism and of cell-cycle of yeast cells after two color soft X-ray irradiation is presented; the soft X-rays being generated in trains of picosecond pulses by laser-plasma interaction. The two color X-ray differential technique is based on the generation of approximately 0.6 KeV X-rays which are deposited only in the membrane-wall complex switching off the anaerobic (fermentative) activity of yeast cells and on the generation of approximately 1.2 KeV X-rays which are mainly deposited in the cytoplasm, mitochondria and nucleus of yeast cells, mainly affecting the aerobic metabolism. A synergetic analysis of the metabolism is discussed, mainly founded on the recording of different correlated metabolic parameters, both on-line and delayed. Among the relevant access, pressure monitoring in batch samples acquire a dominant role allowing the identification of metabolic oscillation, that represent a marker of physical and chemical actions performed on the samples at different times. The experience acquired on yeast cells metabolism is being used to investigate lymphocytes metabolism and the related oscillatory properties of relevant enzymatic complexes. Actually even if it is not exactly the same as the mammalian situation, it should really propel the whole field forward.
Ric Allott, I. C. Edmond Turcu, Nicola Lisi, John Spencer, Waseem Shaikh, Adam Whybrew, S. Wang, R. Donovan, K. Lawley, Kenneth Ledingham, Melvyn Folkard, Kevin Prise
Leading edge research in molecular dynamics, photoelectron spectroscopy, surface interactions and radiobiology has pushed forward the requirement for intense, pulsed, tunable sources of vacuum ultraviolet radiation. Presently, only synchrotron radiation sources are sufficiently bright for these applications. A bright, continuously tunable VUV beamline capable of delivering in excess of 1013 photons/sec/cm2/1nm BW 100 nm, 50 Hz repetition rate (BW equals (Delta) (lambda) /(lambda) is the bandwidth) to the sample, has been constructed on a plasma source generated by a high repetition rate, picosecond KrF excimer laser system.
Saccharomyces Cerevisiae yeast cells were irradiated using the soft X-ray laser-plasma source at Rutherford Laboratory. The aim was to produce a selective damage of enzyme metabolic activity at the wall and membrane level (responsible for fermentation) without interfering with respiration (taking place in mitochondria) and with nuclear and DNA activity. The source was calibrated by PIN diodes and X-ray spectrometers. Teflon stripes were chosen as targets for the UV laser, emitting X-rays at about 0.9 keV, characterized by a very large decay exponent in biological matter. X-ray doses to the different cell compartments were calculated following a Lambert-Bouguet-Beer law. After irradiation, the selective damage to metabolic activity at the membrane level was measured by monitoring CO2 production with pressure silicon detectors. Preliminary results gave evidence of pressure reduction for irradiated samples and non-linear response to doses. Also metabolic oscillations were evidenced in cell suspensions and it was shown that X-ray irradiation changed the oscillation frequency.
Fabrication of 3D terahertz waveguide components is demonstrated using a novel x-ray micromachining process with integral and embedded x-ray masks. 1 nm x-rays generated by a laser-plasma source are used to expose chemically amplified resist. A repeated exposure and development technique shortens the total x-ray exposure time to 10 min to obtain the required 48 micrometers high structures. A 2.5 THz waveguide cavity is fabricated in gold by electroplating the above resist microstructure.
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