The Petawatt beamline at the Vulcan laser facility is capable of delivering pulses with 500J of energy in <500fs, and has been operational as a user facility since 2003; being used to study laser matter interactions under extreme conditions. In addition to this short-pulse beamline there is a single long pulse beamline capable of 250J with durations from 0.5 to 6ns. In this paper we present our plans to add an auxiliary beamline to this facility based on Optical Parametric Chirped Pulse Amplification (OPCPA) using LBO as the non-linear crystal. This new beamline will have a dedicated laser area where the seed will be generated, stretched and amplified before being transported to the target area for compression and delivery to target. The beamline will be implemented in 2 phases the first phase will see the development of a 7J <30fs capability with the second phase increasing the delivered energy to 30J. This additional beamline will open up the potential for novel pump probe experiments when operated with the existing PW and long pulse beamlines.
In this paper we demonstrate the implementation of a modified uniformly redundant array (MURA) coded aperture in the x-ray imaging of high power laser produced plasma. We detail the process of design and manufacture of a self-supporting tantalum coded aperture with ~ 50% open area to work in the 1-25 keV x-ray regime. The advantage of using a coded aperture imaging system in this high noise environment in comparison to a standard pinhole aperture is its larger solid angle and increased signal to noise. The increased solid angle allows the aperture and detector to be placed at a further distance from the interaction point. This is beneficial as it reduces the mechanics in the close proximity of the often crowded interaction region and moves the detector which can include sensitive electronics further away from the source of EMP, hard x-rays and secondary sources generated in the interaction. Here we present initial data taken on an experiment using the Vulcan Petawatt Laser at the Central Laser Facility of a prototype x-ray imager.
Many of the new large European facilities that are in the process of coming online will be operating at high power and high repetition rates. The ability to operate at high repetition rates is important for studies including secondary source generation and inertial confinement fusion research. In these interaction conditions, with solid targets, debris mitigation for the protection of beamline and diagnostic equipment becomes of the upmost importance. These facilities have the potential to take hundreds, if not thousands, of shots every day, creating massive volumes of debris and shot materials. In recent testing of the Central Laser Facility’s High Accuracy Microtargetry Supply (HAMS) system on the mid-repetition rate Gemini facility (15 J, 40 fs, 1 shot every 20 seconds), diagnostics were deployed in order to specifically look at the debris emitted from targets designed for high repetition rate experiments. By using a high frame rate camera, it has been possible to observe and characterize some of the debris production, whilst also looking at target fratricide. Alongside these results from Gemini, we also present results of static debris measurements undertaken on the Vulcan Petawatt high energy, high power facility, where the cumulative effects of debris produced by high power laser experiments have been observed.
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.
The ability to maximise the shot rate of large scale laser facilities is dependent on the turnaround time of the laser,
diagnostics and targetry. In a move to improve the last of these, a combined target mount and carousel are being
implemented on the Vulcan Petawatt facility. The Vulcan Petawatt interaction chamber currently operates with either a
single target or with a target wheel; which has limited positions and varying degrees of subsequent target survivability.
Whenever the target holder needs to be changed the chamber vacuum has to be cycled, delaying shots by up to an hour.
The new carousel design is capable of holding 30 target assemblies at a safe distance from the interaction point, with
each target capable of being dialed in to position on demand. This allows for a whole day’s worth of shots with the
flexibility to choose any target or reference object without having to break vacuum. Here we present the design,
characterisation and implementation of this new target inserter.
The polarization state of a laser has a huge bearing on the physics of laser-plasma interactions and it is often desirable to change between linear and circular. For short pulse high power lasers large beam apertures are necessary for transportation. However, in these extreme conditions transmissive birefringent polarization optics become impractical due to their delicacy and their dispersion of the laser bandwidth which will increase the pulse length, which along with large B-integrals, which arises from the transmission of the high-power beams through optics, can be detrimental to the intensity of the laser. It is therefore necessary to consider reflective optics in order to change the polarization. Modelling has been performed at the Central Laser Facility on a design of a large aperture broadband reflective waveplate suitable for short pulse laser systems.
The requirement from large scale facilities for high repetition rate operations is rapidly approaching, and is increasingly
important for studies into high intensity secondary source generation, QED studies and the push for inertial confinement
fusion. It is envisioned that multiple PW systems at high repetition rates will be built for projects such as the European
Extreme Light Infrastructure project. Depending on the interaction physics involved, a number of differing parameters in
the interaction increase in importance, including positioning accuracy and target surface quality, and to ensure
reproducible optimum interaction conditions, presents a significant problem for accurate target positioning. With these
requirements in mind, a co-ordinated project is underway at the Central Laser Facility amongst the experimental science,
engineering and target fabrication groups, to tackle some of the challenges that we as a community face in working
towards high repetition rate operations. Here we present the latest work being undertaken at the CLF to improve
capability in key areas of this project, specifically in the areas of reliable motion control and rapid target positioning.
KEYWORDS: Modeling, Mirrors, High power lasers, Point spread functions, Adaptive optics, Wavefronts, Motion models, Tolerancing, Off axis mirrors, Near field optics
For many years parabolic mirrors have been used as the primary focusing optics of short pulse high power lasers.
Pushing the boundaries of the highest focused intensities requires not only increases in peak laser power but also
exploring the limits of focal spot size. Modelling has been performed at the Central Laser Facility to evaluate the
performance and tolerance of the alignment of a variety of off-axis parabolic mirrors and their limitations in correcting
beam aberrations. Practical considerations such as debris shields and optic mounting have also been assessed for their
effects on the focal spots.
The medical isotope 99mTc (technetium) is used in over 30 million nuclear medical procedures annually, accounting for over 80% of the worldwide medical isotope usage. Its supply is critical to the medical community and a worldwide shortage is expected within the next few decades as current fission reactors used for its generation reach their end of life. The cost of build and operation of replacement reactors is high and as such, alternative production mechanisms are of high interest. Laser-accelerated proton beams have been widely discussed as being able to produce Positron Emission Tomography (PET) isotopes once laser architecture evolved to high repetition rates and energies. Recent experimental results performed on the Vulcan Laser Facility in the production of 99mTc through 100Mo (p,2n) 99mTc demonstrate the ability to produce this critical isotope at the scales required for patient doses using diode pumped laser architecture currently under construction. The production technique, laser and target requirements are discussed alongside a timeline and cost for a prototype production facility.
KEYWORDS: Optical amplifiers, Picosecond phenomena, Near field optics, Mirrors, Diagnostics, Near field, Silicates, Pulsed laser operation, Glasses, High power lasers
We present details of a refurbishment and development programme that we have undertaken on the Vulcan Nd:Glass laser system to improve delivery to its two target areas. For target area petawatt in addition to replacing the gratings in the compressor chamber we have installed a new diagnostic line for improved pulse length measurement and commissioned a high energy seed system to improve contrast. In target area west we have replaced a grating on the high energy short pulse line and improved the focal spot quality. Both areas have been re-commissioned and their laser parameters measured showing that the pulse in petawatt has been measured below 500fs and focused to a spot size of 4μm the two short pulse beam lines in target area west have been measured as short as 1ps and have been focused to 5μm.
O. Chekhlov, E. Divall, K. Ertel, S. Hawkes, C. Hooker, I. Ross, P. Matousek, C. Hernandez-Gomez, I. Musgrave, Y. Tang, T. Winstone, D. Neely, R. Clarke, P. Foster, S. Hancock, B. Wyborn, J. Collier
We describe two development projects: Astra-Gemini: a Petawatt class system based Ti: Sapphire amplifiers and a
10 PW upgrade for the Vulcan laser. The design concepts, features of the optical design of amplifiers and compressors
are presented. Radial delay compensation techniques used for a 3-x beam expander are discussed.
We report here some observations and preliminary findings from a study focussed on the vacuum-UV (λ, 40-60 nm) radiation emitted during the interaction of 150 ps laser pulses (100-400 mJ) with copper pre-plasmas formed by an electro-optically synchronised (0.1 - 0.8 J, 8 ns) long pulse laser. We have observed significant gains in VUV flux that scale with inter-laser delay. We also report preliminary observations on total X-ray emission from the interaction of a superintense 80 fs, 200 mJ laser pulse at the UK ASTRA laser facility with a similar pre-plasma at irradiances approaching 1019 W/cm2
This paper summarizes our recent progress achieved in the characterization and understanding of the Ni-like Ag transient x-ray laser pumped under traveling wave irradiation. At the Rutherford Laboratory CPA laser facility, we measured the temporal history of the 13.9 nm laser pulse with a high-resolution streak camera. A very short, approximately 2 ps x-ray laser pulse was directly demonstrated for the first time. More recently we carried out an experiment at the LULI CPA laser facility. Several diagnostics that recorded the plasma emission at the XRL wavelength or in the keV range indicate the presence of small-scale spatial structures in the emitting XRL source. Single-shot Fresnel interferograms at 13.9 nm were successfully obtained with a good fringe visibility. Strong lasing was also observed on the Ni-like 4f-4d line at 16 nm.
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