Ian Musgrave

Picosecond optical parametric chirped pulse amplifier as a preamplifier to generate high-energy seed pulses for contrast enhancement

We present the design, implementation, and testing of a novel picosecond optical parametric preamplifier system to generate high-energy seed pulses for the Vulcan laser facility. The preamplifier amplifies 100u2009fs pulses stretched to 3u2009ps pulses from 10u2009pJ to 70 μJ in a single stage of amplification before the pulses are further amplified in the Vulcan high-power Nd:glass laser facility to the petawatt power level. This increased seed energy has led to an improvement of the nanosecond amplified spontaneous emission contrast intensity to 10(-10) of the main pulse, without degrading the output of the laser system.

Recent developments on the Vulcan High Power Laser Facility

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.

The production of patient dose level 99mTc medical radioisotope using laser-driven proton beams

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.

Development of a novel large bandwidth front-end system for high peak power OPCPA systems

In this paper we describe the development of a novel front-end capable of generating pulses with ≫100nm bandwidth at 910nm, a pulse duration ≪30fs and energies at the joule level. This system has been developed as a seed source for the development of a 10PW facility for the Vulcan laser. The development is based on large scale OPCPA with the goal of producing pulses with focused intensities ≫1023 W/cm2 and will be achieved by delivering pulses with ≫300J in ≪30fs onto target.

A highly efficient broadband picosecond pump high-gain OPCPA system for Ti-sapphire seed pulses; an ideal seed for high-contrast, large-energy/aperture CPA laser system: Vulcan

The achievement of high contrast, high efficiency OPCPA systems has been a long established goal. We achieve close to ~20% conversion in a picosecond OPCPA system. This is now the standard seed for our petawatt pre-amplifier laser system which had a conventional 108 nanosecond gain. We thereby eliminate the need to the first nanosecond gain stage. We achieve a contrast at the 10-8 level when using the petawatt system in this configuration. We have also demonstrated a second stage of picosecond amplification with an extra gain of >2, maintaining the bandwidth and transform limited nature of the pulses, providing the potential for further improvements.

The 10 PW OPCPA Vulcan laser upgrade

We present the progress that has been made in developing 10PW capability for the Vulcan laser. These pulses will have focused intensities ≫1023 Wcm−2, which represents orders of magnitude increases in intensity currently available. This will be achieved by generating pulses with energies greater than 300J and with durations less than 30fs using the technique of optical parametric chirped pulse amplification, OPCPA [1].

Development of a Novel Large Bandwidth Front-end System for High Peak Power OPCPA Systems

We present the development of a novel large bandwidth front-end that is capable of supporting sub 30fs pulses, with 0.4J of energy at a 2Hz repetition rate that is centered at 910nm

Characterization of the backscattered radiation from petawatt laser matter interactions.

The development of high peak power and energy laser systems require the assurance that any backscattered radiation will not lead to damage of the laser system. We present the characterization of the backscattered radiation for different target types and conditions at petawatt power levels and intensities (>10(20)W/cm2). We observe that radiation is generated between 700 and 900 nm, as well as the expected self emission and laser fundamental. The percentage of the incident light backscattered reduces as a function of the incident energy and is typically <1% for petawatt laser interactions.