LASER 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 harmonic generation 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 LASER SCIENCE 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 CENTRAL LASER FACILITY 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 lasers 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.