SCIENCE AND DEVELOPMENT Artemis Artemis

Monochromatised XUV beamline 51 for ultrafast time-resolved ARPES

E. Springate, C. Cacho, E. Turcu, C. Froud, The short pulses of coherent XUV S.G. Hook (CLF, STFC, Rutherford Appleton radiation produced through high Laboratory, UK) Layout of the XUV beamline including the have enabled the Harmonic generation chamber, the L. Poletto, P. Villoresi, F. Frassetto, S. Bonora (LUXOR, Padova, Italy) study of ultrafast electron dynamics in monochromator chamber to select the photon atomic systems and simple molecules. energy, the recombination chamber for pump- W.A. Bryan, G.R.A.J. Nemeth probe experiment and the experimental (Swansea University, UK) The Artemis facility now aims to exploit chamber for time resolved ARPES. A. Cavalleri, J. Petersen, N. Dean these XUV pulses to investigate ultrafast (University of Oxford, UK) dynamics in experiments spanning gas- S. Dhesi phase chemistry of polyatomic molecules (Diamond, UK) A specially designed monochromator and condensed-matter physics of complex allows us to select a single harmonic and C. Cacho materials. [email protected] preserve also the short pulse duration (10 - 30 fs). We have shown that the We have built an XUV beamline that beamline can achieve 250 meV energy delivers short pulses of monochromatised resolution and 30 fs temporal resolution, XUV, produced through high harmonic enabling us to carry out first measurements generation, to an end-station optimized for of angle- time- resolved photoemission photo-emission experiments on condensed with XUV pulses. matter.

Spin and angle resolved photoemission with fs laser 52 source: calibration of spin detector

C. Cacho (CLF, STFC, Rutherford Appleton Angle resolved photoemission is a very systems with large spin-orbit coupling Laboratory, UK) powerful technique to explore the [1-2]. The intrinsic low efficiency of the C.M. Cacho, S. Vlaic, M. Malvestuto, electronic structure of materials. Over the electron spin detection makes these B. Ressel, and F. Parmigiani (Sincrotrone Trieste, Trieste, Italy) past three decades this spectroscopic experiments very challenging. This is why, technique has well matured partly due to using a laser source with a novel electron W. Bryan, G.R.A.J. Nemeth (Swansea University, UK) the development of intense synchrotron analyzer (electron time-of-flight) is a real

E.A. Seddon (Manchester University, UK) radiation and bright fs-laser sources. step forward for this type of experiment Measuring the spin as well as the emission particularly in terms of acquisition time C. Cacho [email protected] angle of the photoelectron is particularly and resolution. Furthermore by combining interesting to study the magnetic the ToF-Spin analyzer to the Artemis properties of ferromagnetic systems or facility, one can study the electron spin dynamic in the sub 10-fs time domain which is of great interest to explore the switching mechanisms in ferromagnetic systems for spintronic devices.

1 J.-H. Park et al., Nature, 392, 794 (1998). 2 K. Sakamoto et al., Phys. Rev. Lett.,102, 096805 (2009)

Top view of the experimental setup in normal polarimeter where they are spin resolved. The emission geometry. The photoelectrons travel arrival time of the electrons at each detector through the drift tube up to the Mott is measured and converted to kinetic energy.

CENTRAL LASER FACILITY Annual Report 2009 - 2010 33 AND DEVELOPMENT Artemis

Few-cycle carrier-envelope-phase controlled laser pulses 53 for time resolved science at the Artemis facility

W.A. Bryan, G.R.A.J. Nemeth When the duration of a laser pulse reaches of the energy can be focused into a hollow (Swansea University, UK and CLF Facility, STFC the few-cycle level, the phase of the laser fibre to generate few-cycle pulses. Recent Rutherford Appleton Laboratory, UK) electric field relative to the pulse envelope improvements have reduced the R.B. King (Queen’s University Belfast, UK) (the carrier-envelope phase, CEP) can have pulselength to 7 fs, with 0.5 mJ per pulse. a significant effect on the physics of the The long-term stability of the CEP C.M. Cacho, I.C.E. Turcu and E. Springate (CLF, STFC Rutherford Appleton Laboratory, UK) interaction. Examples of this are the stabilisation is 325 mrad rms for over five generation of isolated attosecond pulses hours. E. Springate, [email protected] [1] and the control of electron localisation during molecular dissociation [2], both of 1. A. Baltuska et al, “ Attosecond control which require few-cycle pulses with stable of electronic processes by intense light CEP. fields”, Nature 421, 611 (2003). 2. M. F. Kling et al, “Control of electron The Artemis facility is constructed around a localization in molecular dissociation”, CEP stabilised laser system with an output Science 312 246 (2006). of 780 nm, 30 fs, 14 mJ pulse at 1 kHz. Part

FROG measurement of 7 fs, 0.5 mJ CEP control over five hours with pulses produced in the hollow fibre 2 mJ/pulse and 325 mrad rms system showing retrieved temporal stability. Blue line: programmed intensity and phase. The FROG error target phase. Red line: measured was 0.006. phase.

34 Annual Report 2009 - 2010 LASER SCIENCE AND DEVELOPMENT Astra Astra

Vibration in Gemini and engineering 54 modifications (interim report)

S. Blake, R. Pattathil, P.S. Foster Intermittent ground borne vibration The full report details the vibration scan (CLF, STFC, Rutherford Appleton Laboratory, UK) delayed and plagued early experiments in results, changes to the hardware and initial H.Huang Astra Gemini. The vibration manifested conclusions. (Diamond, UK) itself in an elliptical or figure of eight S. Blake, movement of the spot at the interaction [email protected] point. After analysis the source was traced back to the main magnet power supply of the neighbouring ISIS facility. The main source at 50 Hz was amplified by the support structure, multi component breadboard and key optical mounts increasing the amplitude of the vibration at each stage. Large structural changes were carried out to the main optics table and associated framework, parabola chamber and the key optical mounts. The initial testing post upgrade is positive. The image The new structure and the location of on the right shows the main optics table the four sensors. (breadboard), supporting structure which spans the trench leading to ISIS and the change to the key optical mounts.

Temporal and spatial overlap monitoring 55 of the dual-beam layout in Astra-Gemini TA3

N. Booth, D. R. Symes, P. S. Foster, J. Martin, The Astra-Gemini target area is now up and To monitor the spatial overlap, leakage P. P. Rajeev, D. Neely running for dual beam experimental from each of the beams is taken, then (CLF, STFC, Rutherford Appleton Laboratory, UK) operations. It is now essential to have combined, focussed, and split to a near- N. Booth, spatial and temporal overlap of the two field and a far-field camera. The near-field [email protected] beams at the target position. Two extra will be used to indicate the temporal diagnostics have been added to the target overlap of the two beams and the jitter in area to monitor these overlaps on a the spatial alignment. The far-field will shot-to-shot basis. monitor the spatial stability of the overlap of the two beams.

A cross-correlator diagnostic has been installed in order to monitor the temporal overlap. Leakage is taken from each of the beams which are both split and overlapped with two BBO crystals to generate two cross correlation traces, one with a time window of ~ 6 ps and one with a > 6 ps window. Schematic diagram of the beam arrangements in Astra-Gemini TA3. Red indicates the main beamlines and pink indicates leakage beams.

CENTRAL LASER FACILITY Annual Report 2009 - 2010 35 LASER SCIENCE AND DEVELOPMENT Astra

Upgrade of Astra amplifier 3 and the Astra interlock system 56

C. Hooker, B. Costello, S. Hawkes, Last year a significant C. John, B. Landowski, A. Tylee upgrade was carried out to (CLF, STFC, Rutherford Appleton Laboratory, UK) the old Astra amplifier 3, C. Hooker, which has improved its [email protected] performance and removed one of the least reliable commercial from the system. The old Macholite laser was replaced with four Quanta-Ray PRO-350 Nd:YAG lasers, and a new water cooling system installed. The layout of the amplifier was redesigned for better Schematic of the new layout accessibility: before the changes, the beam for Astra Amplifier 3. expansion tubes were on a raised framework above the amplifier, but now Joules at 800 nm. During the same period, everything is on the same level. The new the old PC-based interlocks were replaced layout is shown in the diagram. The with an up-to-date system based on PLC performance of the amplifier is better than technology, giving improved safety and full before, with a typical output of 1.2 to 1.3 compatibility with other areas of the CLF.

Improved post-experiment data analysis at Astra Gemini 57

V. Marshall, D. Symes We have further improved the gathering traces are averaged and displayed as a (CLF, STFC, Rutherford Appleton Laboratory, UK) and analysis of diagnostic data over the Scalable Vector Graphics (SVG) images. The V .Marshall, course of an experiment. In conjunction laser operator can subsequently view this [email protected] with the Principal Investigator, we identify data and, for image data streams such as the laser parameters (singular values, trace far-field profiles and FROG traces, select images and camera images) which are key the image which represents a typical image to that experiment and make them for that day. In this way we compile an available to users as Comma-Separated overall summary table detailing the Values (CSV) files. This CSV data can be average trace plots, representative images downloaded and incorporated into analysis and a scatter plot of X/Y alignment pairs on programs written for target area a shot-by-shot, day-by-day basis. diagnostics. Singular value data streams are subsequently averaged and displayed;

Three day’s worth of representative images and plots.

36 CENTRAL LASER FACILITY Annual Report 2009 - 2010 LASER SCIENCE AND DEVELOPMENT Astra

A new phase (and amplitude) for Astra 58 Gemini: using a spatial light modulator

C. Hooker, V. Marshall We have developed a new method for The sum of the voltages controls the phase (CLF, STFC, Rutherford Appleton Laboratory, UK) correcting the spectral phase and and the difference controls the spectral C. Hooker, amplitude of the Astra Gemini laser, based amplitude. The existing phase corrector [email protected] on a spatial light modulator (SLM). This () suffers from crosstalk between device uses voltages applied to a pair of phase and amplitude corrections: the liquid-crystal arrays to modify different advantage of the SLM is that such crosstalk parts of the spectrum in a is minimised. The SLM is positioned at the spatially-dispersed laser beam. mid plane of a 4F zero-dispersion optical setup using blazed 600 groove/mm gratings. It is controlled through a custom interface that allows the user to set the amplitudes of four polynomial phase terms and to apply localised phase and amplitude adjustments. The interface is designed for use by operators wearing laser protective eyewear.

View of the SLM control system user interface.

Ultrafast gated imaging of laser produced 59 plasmas using the optical Kerr effect

D.R. Symes, U. Wegner, H-C. Ahlswede, Optical imaging provides a versatile We conclude by exploring the possibility to M.J.V. Streeter, P.L. Gallegos, E.J. Divall, diagnostic for investigations of plasmas produce a sub-10fs, high dynamic range P.P. Rajeev, D. Neely (CLF, STFC Rutherford Appleton Laboratory, UK) generated under intense laser irradiation. “all optical” streak camera. Electro-optic gating techniques operating R.A. Smith (Imperial College London, UK) on the >100ps timescale are commonly used to reduce the amount of light D.R. Symes, detected from self-emission of hot [email protected] or improve the temporal resolution of the detector. The use of an optical Kerr gate enables a superior dynamic range and temporal resolution compared to electronically gated devices. We have applied this method using the hollow fibre pulse compressor in Astra TA2 to demonstrate enhanced imaging of laser produced plasmas. Employing fused silica, which has an ultrafast response, as the We use the optical Kerr effect to gating material we achieved a gate time perform ultrafast gated plasma imaging. ~100fs. We also discuss alternative The opening time of the gate is ~100fs materials. We used the system to image in fused silica (black) compared to plasma produced with moderate intensity slower response materials. Shown by irradiation and show the elimination of the throughput of the device versus plasma self-emission from the image. delay between gating and probe beams.

CENTRAL LASER FACILITY Annual Report 2009 - 2010 37 LASER SCIENCE AND DEVELOPMENT Lasers for Science Facility Lasers for Science Facility

Two-photon fluorescence 60 correlation : FCS Calculating the autocorrelation Fluorescence correlation spectroscopy P. Burgos function. (CLF, STFC, Rutherford Appleton Laboratory, UK) (FCS) is a powerful single-molecule detection technique used to characterise P. Burgos, p.burgos @stfc.ac.uk the dynamics and interactions of this technique using our TiSa confocal fluorescent species by recording and setup, the diffusion coefficient of the correlating their fluctuations in Rhodamine dye was measured for different fluorescence intensity within a microscopic concentrations and laser powers. Surface detection. To demonstrate the potential of diffusion has been recorded in vivo.

The ULTRA time-resolved IR, 2D-IR and T-2D-IR station 61 I.P. Clark [email protected]

Developments within the EPSRC Laser Loan Pool 62 I.P. Clark [email protected]

The Octopus imaging cluster: A new imaging facility in 63 the Research Complex at Harwell

S.W. Botchway, D.T. Clarke, M. Hirsch, The past year has again seen major Octopus cluster has at its core a hub of 14 A. Mackenzie, M.L. Martin-Fernandez, changes in the Lasers for Science Facility. lasers (3 Ti:Sa, 2 OPOs, 3 supercontinuum S.R. Needham, S.K. Roberts, D.J. Rolfe, A. Tylee, C.J. Tynan, S.E.D. Webb The LSF’s operations in the biological and 6 CW). The laser sources provide (CLF, STFC, Rutherford Appleton Laboratory, UK) imaging area were relocated to the excitation light to seven microscope M. Martin-Fernandez, Research Complex at Harwell (RCaH) in systems, namely a total internal reflection [email protected] April 2010. The Octopus cluster is a large fluorescence (TIRF) tweezers system, 3 scale imaging facility offered by the single molecule fluorescence microscopes, Functional Biosystems Imaging Group of each of which is specialised in a different the LSF which begun user single molecule imaging technique, two operations and collaborative 1-photon confocal FLIM (Fluorescence work in July 2010. Octopus is Lifetime Imaging Microscopy) systems and a new concept in multi-modal a 2-photon confocal FLIM system laid out imaging. Currently in Phase I as shown left. of its development, the

Layout of the Octopus cluster. 5-colour single molecule tracking system. Top right: The central room is the laser hub with the different This room houses a one-photon multicolour microscopes lab position around it. It also houses a confocal FLIM system. Top middle: The control two-photon confocal FLIM system. Bottom right: room (see Fig. 2). Top left: Storage room. Left: This this room houses three systems, namely a total rooms houses a 3-colour single molecule tracking internal reflection fluorescence (TIRF) tweezers system (top) and an 8-channel single molecule system, a one-photon confocal FLIM system and a FRET and polarisation combined system (bottom). Bottom middle: Development room.

38 CENTRAL LASER FACILITY Annual Report 2009 - 2010 LASER SCIENCE AND DEVELOPMENT Lasers for Science Facility

New data analysis software for time-resolved 64 spectroscopy experiments in the Ultra laser facility

M.R. Pollard, G.M. Greetham, D.A. Robinson, New data analysis software has been efficient analysis of large data sets in order M. Towrie, I.P. Clark, A.W. Parker developed in response to the start of to guide their experiment. The need for (CLF, STFC, Rutherford Appleton Laboratory, UK) operations in the Ultra laser facility and the expediency is reinforced because of the M. Pollard, significant increase in experimental data limited lifetime of precious biological and mark.pollard @stfc.ac.uk that it brings. The facility generates chemical samples that are potentially light spectral data at a typical rate of > 50 or temperature sensitive. We describe the spectra per experiment with ~ 15 features of the software including experiments per day, which requires correction for instrument variation (such as visiting scientists to perform quick and background intensity and detector-based electronics noise) and a flexible data display that allows visiting scientists to observe their data according to experimental parameters in two and three dimensions.

Screenshot of graphics display, showing data from sample of DMABN.

Active synchronisation of dual amplifier outputs 65 for time-resolved spectroscopy

M.R. Pollard, G.M. Greetham, D.A.M. Towrie Robinson, Many of the time-resolved spectroscopy We report the development of a control M.(CLF, Towrie, STFC, Rutherford I.P. Clark and Appleton A.W. ParkerLaboratory, UK) experiments in the Ultra laser facility take system that improves synchronisation of (CLF, STFC, Rutherford Appleton Laboratory) M. Pollard, advantage of its unique dual synchronised the two outputs to 40 fs rms, achieved mark.pollard @stfc.ac.uk 2 ps and 50 fs output pulses. The relative using a scanning optical correlator system timing between the pulses is susceptible to to measure the relative timing between the thermal drift of potentially several mm that pulses and a feedback loop control system occurs in the optical paths within the laser to ensure that the synchronisation of the amplifiers, which significantly affects two outputs is constrained to a defined experimental measurements. set-point.

Comparison of relative timing over 2 hours.

CENTRAL LASER FACILITY Annual Report 2009 - 2010 39 LASER SCIENCE AND DEVELOPMENT Lasers for Science Facility

Optical trapping of laser targets under vacuum for 66 ion-beam production in the LIBRA programme

A.D. Ward, B. Li, T. Strange As part of the targetry package of the high-power laser beam. In the report we (CLF, STFC, Rutherford Appleton Laboratory, UK) EPSRC funded LIBRA programme, we have outline the underpinning methodology and A. Ward, successfully held a microscopic liquid optical requirements for trapping [email protected] droplet in the centre of a vacuum micron-sized droplets using long-working interaction chamber at a pressure of distance, high numerical aperture objective 5 mbar using laser-based optical levitation lenses. By extension of this technology, our techniques. The droplet was held to a goal in the LIBRA programme is to hold positional accuracy of 1 micron which solid targets for the purpose of generating demonstrates the concept is suitable for ion-beams by laser irradiation. manipulating targets into a focused

The vacuum chamber and diagnostics in operation. Droplet stability, laser alignment and chamber pressure are continually monitored. Trapping can be achieved from 1000 mbar to 5 mbar before efflorescence of the salt droplet occurs (i.e. a crystal is formed). The droplet is observed to be stable in position to approximately 1 micron.

40 CENTRAL LASER FACILITY Annual Report 2009 - 2010 LASER SCIENCE AND DEVELOPMENT Vulcan Vulcan

Close-in contrast measurements of the new ps OPCPA front end 67

A.G. Boyle, I. Musgrave, M. Galimberti, In high intensity laser matter interactions W. Shaikh, K. Lancaster, B. Costello, the contrast of the laser pulse can be A. Frackiewicz, R. Heathcote (CLF, STFC, Rutherford Appleton Laboratory, UK) crucial to the outcome of the physics. In I. Musgrave, this article we discuss the addition of a [email protected] picoseconds optical parametric chirped pulse amplification (OPCPA) stage to the Vulcan front end improving the amplified stimulated emission.

The novel dual OPCPA pre-amplifier system is sufficiently stable to be injected into the 3rd order cross correlator (Sequoia) rest of the Vulcan laser system and leads to trace, which is a multi shot device that a direct improvement of the ASE contrast temporally scans the pulse. by at least 2 orders of magnitude without degrading the performance of the laser system. The Vulcan Petawatt laser system now has an ASE contrast of 1010 at 1ns, at 100ps the contrast is better than 108 and the PF (Parametric Fluorescence) caused by the ps OPA starts at 30ps.

Vulcan rod amplifier upgrade 68

A.K. Kidd, N. Stuart, A.G. Boyle, The Vulcan rod amplifier control system The upgrade was successfully completed D.A. Robinson, D.A. Pepler, T. Winstone, and power supplies have been operating three days overdue and user experiments C. Hernandez-Gomez (CLF, STFC, Rutherford Appleton Laboratory, UK) and running successfully on the Vulcan commenced on Monday 9th November A. Kidd, laser system since the system was 2009. [email protected] inaugurated in 1975. But the equipment suppliers no longer manufacture or even The experience gained from this project support the electronics for the rod will aid the future success of the upcoming amplifiers. Therefore, it was necessary for six-year 10 Petawatt upgrade project. the rod amplifier capacitors and control system to be replaced, as it posed a serious risk towards the future operation of Vulcan.

The Vulcan laser was shut down for three months from 12th August until 9th November to allow the replacement of the rod amplifier racks from inside the control room and laser areas with new capacitor banks.

Old Quantel units inside the Vulcan Main Control Room. New Quantel racks, located on north wall of Laser Area 1, to power the 45mm rod amplifiers and control processing and power of both rod chains.

CENTRAL LASER FACILITY Annual Report 2009 - 2010 41 LASER SCIENCE AND DEVELOPMENT Vulcan

Vulcan computer control system upgrade 69

D.A. Pepler, A.K. Kidd, P. Holligan, The successful operation of the Vulcan The bulk of the development for this took D. Robinson, C. Hernandez-Gomez, high-power laser over the past 30 years has place offline with the final windows T. Winstone (CLF, STFC, Rutherford Appleton Laboratory, UK) been heavily dependent on the use of controls being tested, in parallel with the D.Pepler, computerized control systems. These existing DOS controls, during the normal [email protected] originated with a GEC 4080 “mini” inter-experimental maintenance periods, a computer but in the mid 1980’s were process which ensured minimal operational replaced with a pair of IBM 286 DOS-based downtime. PC’s. The network continued to grow in size and complexity with (by the late 1990’s) some peripheral PC’s running Windows NT / 2000 but with the core fundamental laser control PC’s remaining DOS.

A project to completely rewrite the computer control system, converting everything to windows XP compatible coding, turned out to be more complex than originally thought and became a four Main control screen giving access to prime control functions and diagnostic data such as year project. the shot firing sequence and waveform displays.

The Vulcan 10PW project – building design 70

B.E.Wyborn, S.P.Blake, R.J.Clarke, J.L.Collier, A key aspect of the Vulcan 10 PW project Vulcan 10PW building design. This resulted S.Hancock, C.Hernandez-Gomez, P.Holligan, is the new building that will house the in a conceptual design report presentation D.Neely, T.B.Winstone (CLF, STFC, Rutherford Appleton Laboratory, UK) large amount of equipment required for and review. J.M.Henstridge, P.Allen, H.Loosemore, the 10 PW laser facility. The building will D.Matthewson (STFC, Rutherford Appleton Laboratory, UK) extend the current building (R1) to Following this the 10PW management D.Reynolds maximise the available space within the team have now agreed a conceptual design (Capita Symonds Ltd, Portishead, UK) limited surrounding land at RAL. In for the building that has been costed to a C.Biddle (Franklin Andrews, Birmingham, UK) preparation for the start of phase two of level adequate for the project to proceed A.Gainer, J.Baker, R.Gibbs, the project a team consisting of STFC staff to the building detail design, ready for J.Wingfield-Stratford (Nightingale Associates, Harwell, UK) and external consultants has been working anticipated tender action in the Autumn of P. Ward, A. Hawkin hard for the past six months to develop the 2010. (Fairhurst, Leeds, UK) M. Bacon, G. Rishworth, A. Pearson (AECOM, St Albans, UK) M. Weeks (EDP HS&E Consultants Ltd, St. Helens, UK) B. Wyborn, [email protected] View of new 10 PW building.

42 CENTRAL LASER FACILITY Annual Report 2009 - 2010 LASER SCIENCE AND DEVELOPMENT Laser R&D Laser R&D

The DiPOLE project: towards high energy, 71 high repetition rate diode pumped lasers

K. Ertel, S. Banerjee, P. Mason, J.P. Phillips, DiPOLE stands for Diode Pumped Optical A distributed cooling technique using the P. Rice, S. Tomlinson, C. Sawyer, S.P. Blake, Laser for Experiments. It is a new project at slab-stack architecture aids in minimising C. Hernandez-Gomez, J.L. Collier (CLF, STFC, Rutherford Appleton Laboratory, UK) the CLF to develop the foundations of amplified spontaneous emission (ASE)

T. Davenne, M. Fitton, J. Hill, A. Lintern novel high energy, high average power losses by enabling the use of a relatively (ETC, STFC, Rutherford Appleton Laboratory, UK laser systems based on diode pumped solid thick media with low doping K. Ertel, state laser (DPSSL) technology. Compared concentration. To test the concept in the [email protected] to conventional systems, this approach laboratory, a lower-energy, multi-J promises dramatically increased repetition prototype amplifier system is currently rates (and hence average powers) at under development. significantly higher electrical-to-optical conversion efficiency. The article presents the conceptual design of a cryogenic Yb:YAG amplifier that can be scaled to kJ energy levels and beyond, owing to its geometry and unique cooling technique. Numerical modelling predicts superior performance of the amplifier at 175K compared to room temperature.

Yb:YAG - Cr4+:YAG Schematic diagram of the cryocooler system compound disk. under development at CLF.

Timing and synchronisation system designs 72 for the New Light Source

G.J. Hirst In recent years a new generation of “free The FELs, based on particle accelerators, (CLF, STFC, Rutherford Appleton Laboratory, UK) electron laser” light sources has appeared, are very large – many hundreds of metres G.J. Hirst, delivering beams which will revolutionise long. But the light pulses they produce are [email protected] science just as conventional lasers have very short. With a few tens of done since their invention 50 years ago. femtoseconds duration their physical length can be less than a hundredth of a millimetre. Much of the work that scientists want to do with them makes use of this very short duration, often combining beams from more than one ultrafast source in complex experimental geometries. Synchronising the pulses, which have travelled so far, so that they all arrive at exactly the right time on the A design for a system to target is a huge challenge. But a synchronise light pulses combination of ultra-low noise laser-based from a free electron clocks, feedback-stabilised optical fibre laser and a conventional laser at an experimental transport and state of the art electronics endstation. promises to meet it!

CENTRAL LASER FACILITY Annual Report 2009 - 2010 43 LASER SCIENCE AND DEVELOPMENT Laser R&D

Experimental setup in the Vulcan HaPPIE laboratory 73 for multi-beam combination to achieve diffraction-limited pulses

P.J. Phillips, C. Hernandez-Gomez, J.L. Collier With future and current designs for high This article explains the various methods (CLF, STFC, Rutherford Appleton Laboratory, UK) power lasers requiring several sub-beams for one-aperture wavefront measurement P.J. Phillips to be combined into a single monolithic and then goes on to explain how a phase [email protected] one, technology needs to be developed to difference (piston measurement) between allow these beams to be spatially and two sub-apertures can be extracted using a temporally overlapped. A CLF laboratory proprietary technology. An experimental has been set up - the Vulcan HaPPIE setup to test the concept is described and Laboratory ( High Average and Peak Power future developments are discussed. lasers for Interaction Experiments) to research various techniques to spatially and temporally lock two or more sub-beams.

Experimental layout. Laboratory setup, beam path is shown by the use of the red line.

44 CENTRAL LASER FACILITY Annual Report 2009 - 2010 LASER SCIENCE AND DEVELOPMENT Target Fabrication Target Fabrication

Installation of the target fabrication 74 quality management system

E. Barber, D. Wyatt, C. Spindloe, I. East, As target complexity is increasing and also streamline the processes from inception to H.F. Lowe, S. Serra, M.K. Tolley with the introduction of high repetition delivery of a product the Target Fabrication (CLF, STFC, Rutherford Appleton Laboratory, UK) rate laser systems such as Astra Gemini the Group has introduced a Quality D. Wyatt demands on target fabrication to improve Management System (QMS) into its [email protected] productivity and quality increase. It is experimental delivery procedures. This essential to be able to trace, track and quality management process incorporates record target fabrication processes both the full process of target fabrication from during and after an experiment to the initial conceptual design of a target, interrogate data and to understand the through the planning stage to manufacture underlying science that is achieved. To and finally delivery to the experimental deliver this service and to improve and user group for their experimental shots.

Electroplating of gold and palladium for high power laser 75 target fabrication

S.Serra [email protected]

Mass production of AFI cone geometries 76 for fusion target studies

C. Spindloe, H.F. Lowe, M.K. Tolley One of the baseline targets for the HiPER mass production techniques have been (CLF, STFC, Rutherford Appleton Laboratory, UK) project uses an innovation called AFI developed that have dramatically reduced P. Hiscock, M. Beardsley (Advanced Fast Ignition) in which a fuel target costs, and therefore increase that (Space Science and Technology Department, STFC, Rutherford Appleton Laboratory, UK) sample is compressed using multiple laser availability of target components to the beams around the end of a gold cone. community. This initial work is summarised C. Spindloe, [email protected] These gold cones have been fabricated and and more recent work to develop new assembled at RAL since 2003 using single target geometries and cones of different ‘one-off’ production methods. Recently materials are discussed.

A SEM image of the parabolic An array machined in aluminium shape of the tip. for copper plating

CENTRAL LASER FACILITY Annual Report 2009 - 2010 45 LASER SCIENCE AND DEVELOPMENT Instrumentation and Plasma Diagnostics Instrumentation and Plasma Diagnostics

Debris analysis and mitigation 77 for target motion systems

R. Clarke, P. Rice, D. Neville, T. Strange, The use of motion stages within Target A. Cox, S.G. Hook, C. Spindloe, M. Tolley Area Interaction Chambers is key to the (CLF, STFC, Rutherford Appleton Laboratory, UK) flexibility of experiments. Both targetry and R.Clarke diagnostics use such stages to allow [email protected] in-vacuum positioning and adjustments in order to maximise the data output from shots. Failure of these systems has a high impact and usually requires the replacement of components in-situ. Over the last few years the ‘sticking’ encoders has dominated the failure modes for the standard motorised mounts. This report discusses the main cause of such sticking and one method for reducing the likelihood of reoccurrence. EDX image of target debris coated onto the magnetic rod.

Calibration of image plate response 78 to energetic carbon ions

Image Plate (IP) detectors are widely used the slots, both on the CR39 and IP. The PSL D. Doria, S. Kar, K. Kakolee , B. Ramakrishna, G. Sarri, K.E. Quinn, M. Borghesi for revealing x-rays, electrons and ions in signal from the IP and the pits number on (Queen’s University Belfast, UK), laser-plasma experiments. While IP the CR39 were compared at a given ion J. Osterholz, M. Cerchez, O. Willi response to protons has been reported in energy. (Heinrich-Heine Universität, Düsseldorf), earlier works, we have carried out for the X. Yuan, P. McKenna (University of Strathclyde, UK) first time measurements in which the IP response to Carbon ions has been D. Doria, measured by cross-calibration with CR39. [email protected] In order to obtain the IP calibration for Carbon ions of different energies a Thomson Parabola is used to disperse the ion beam. A slotted CR39 placed on the IP is used as detector so that carbon ions having reasonably close energy can be recorded at same time around the edges of Calibration curve that relates the PSL signal to the number of carbon ions as function of the ion energy.

46 CENTRAL LASER FACILITY Annual Report 2009 - 2010