Periodic Reporting for period 1 - LILDIA (Longwave Infrared Laser Driven Ion Accelerators)
Reporting period: 2020-11-23 to 2022-11-22
Laser driven plasma accelerators are a disruptive technology developing hand-in-hand with the ongoing revolution in high power lasers. This project addressed a new avenue in the development of laser driven ion sources. Almost all research in this area is performed using optical or near-infrared laser systems, but there are important benefits in using longer wavelength drivers. This project was dedicated to investigating and optimising ion sources driven by high power long-wave infrared high power laser drivers. In particular, I made use of the possibility of using gaseous targets, which are ideal for such long wavelengths, allowing easier deployment of the source at high repetition rate. I also made use of the unprecedented diagnostic access allowed by using long wavelength drivers.
The project was therefore an important step in developing a new frontier in intense laser-plasma interactions and energetic ion sources with extremely high peak current, low transverse emittance and easily varied ion species, providing a promising alternative to conventional ion sources. In the near future, these sources will be usable for applications in, for example, radiobiology and material stress studies. For example, the beams generated by laser driven ion sources is ideal for studies of the FLASH effect in radiotherapy, in which ultra-high dose rates result in increased healthy tissue sparing. This will result in improved cancer treatment.
This project had several main outcomes:
1) I developed two new diagnostics to help understand the way the laser interacts with the plasma and the subsequently accelerated particles. The first was a femtosecond optical probing system, which allowed, for the first time, intrapulse interrogation of a laser driven ion source from a near critical density target. The second was the development of a scintillator based beam profile monitor, which was used to observe accelerated ions.
2) I discovered and investigated a new regime of ion generation from long wave infrared laser driven gas jets. Although producing relatively modest ion energies, the shot-to-shot stability and beam uniformity was excellent, which are important parameters for future applications
3) I investigated the role of laser contrast on ultra-high intensity laser interactions with ultra thin targets, allowing me to accelerate protons and ions up to very high energies using a relatively high repetition rate laser system, a significant step forward from previous work requiring very slow and large high energy glass based laser systems
Therefore, I met the objectives of the project and at the same time have found various promising new regimes for future work. I believe the impact of this project will be long-lasting and generate further interest in using long wave infrared lasers to accelerate ions for future applications.
The project was therefore an important step in developing a new frontier in intense laser-plasma interactions and energetic ion sources with extremely high peak current, low transverse emittance and easily varied ion species, providing a promising alternative to conventional ion sources. In the near future, these sources will be usable for applications in, for example, radiobiology and material stress studies. For example, the beams generated by laser driven ion sources is ideal for studies of the FLASH effect in radiotherapy, in which ultra-high dose rates result in increased healthy tissue sparing. This will result in improved cancer treatment.
This project had several main outcomes:
1) I developed two new diagnostics to help understand the way the laser interacts with the plasma and the subsequently accelerated particles. The first was a femtosecond optical probing system, which allowed, for the first time, intrapulse interrogation of a laser driven ion source from a near critical density target. The second was the development of a scintillator based beam profile monitor, which was used to observe accelerated ions.
2) I discovered and investigated a new regime of ion generation from long wave infrared laser driven gas jets. Although producing relatively modest ion energies, the shot-to-shot stability and beam uniformity was excellent, which are important parameters for future applications
3) I investigated the role of laser contrast on ultra-high intensity laser interactions with ultra thin targets, allowing me to accelerate protons and ions up to very high energies using a relatively high repetition rate laser system, a significant step forward from previous work requiring very slow and large high energy glass based laser systems
Therefore, I met the objectives of the project and at the same time have found various promising new regimes for future work. I believe the impact of this project will be long-lasting and generate further interest in using long wave infrared lasers to accelerate ions for future applications.
The project had 5 main work packages, each with their own specific objectives.
WP1 is project management. Regular meetings were held with the research supervisor, and progress regularly assessed. In some cases, covid-19 related delays forced some rescheduling of the work plan. However, we successfully implemented the project goals.
WP2 is for developing high repetition rate diagnostics for the laser driven ion sources. I successfully implemented a scintillator based beam profile monitor, which was delivered and worked extremely well on the experiment. This diagnostic allowed us to measure the angular divergence of the ion beam generated by our ion source. The technique used is novel and is being prepared for publication. I also implemented a new femtosecond optical probing system. This allowed me to take time resolved measurements of the ion acceleration process within the lifetime of the driver, something which has never been achieved before for laser driven ion sources.
WP3 was to demonstrate ion generation from a long wave infrared driven gas jet, and to investigate the mechanisms by which the ions were generated. This work was successfully performed, and a new regime of ion acceleration observed, in which electrons accelerated by the laser formed a diffuse sheath at the rear of the gas jet. This resulted in very stable and reliable ion generation, which is important for applications. Furthermore, the optical probing diagnostic developed in WP2 allowed us to measure the ion acceleration process in real-time, for the first time. I recreated the experiment using state-of-the-art particle-in-cell simulations, which agreed excellently with the experiment. These results are currently being prepared for publication in a high impact journal.
WP4 was to investigate the acceleration of ions from long wave infrared driven solid targets. Due to covid-19 delays and travel restrictions, some change to the workplan here was required. I was unable to access the long wave infrared laser facility for this experiment, so instead I performed a related experiment at a different facility. A near-infrared laser was used to drive ion acceleration from thin targets. I was able to demonstrate record ion energies for the laser type, and used particle-in-cell simulations to elucidate the acceleration process. I am first author on a publication of this work, which is in press at Light | Science and Applications (IF 20.26) and has caused considerable excitement in my research community. At the same time, planning work was performed for the long wave infrared driven solid target experiment and an experiment will be performed soon (after the end of the project) to investigate the interaction.
WP5 was for dissemination and communication of the work. During the project, I had invited talks at some of the top conferences in my field, including the 63rd Annual Meeting of the American Physical Society - Division of Plasma Physics 2021 (8th November 2021), the 5th European Advanced Accelerator Concepts Workshop (21st September 2021), and the International Conference on High Energy Density Science 2021 (4th April 2021). I have further invites for upcoming conferences based on work performed during the project. I created a webpage to describe the project. I have had one first author publication accepted at Light | Science and Applications (IF 20.26) and two more in preparation.
WP1 is project management. Regular meetings were held with the research supervisor, and progress regularly assessed. In some cases, covid-19 related delays forced some rescheduling of the work plan. However, we successfully implemented the project goals.
WP2 is for developing high repetition rate diagnostics for the laser driven ion sources. I successfully implemented a scintillator based beam profile monitor, which was delivered and worked extremely well on the experiment. This diagnostic allowed us to measure the angular divergence of the ion beam generated by our ion source. The technique used is novel and is being prepared for publication. I also implemented a new femtosecond optical probing system. This allowed me to take time resolved measurements of the ion acceleration process within the lifetime of the driver, something which has never been achieved before for laser driven ion sources.
WP3 was to demonstrate ion generation from a long wave infrared driven gas jet, and to investigate the mechanisms by which the ions were generated. This work was successfully performed, and a new regime of ion acceleration observed, in which electrons accelerated by the laser formed a diffuse sheath at the rear of the gas jet. This resulted in very stable and reliable ion generation, which is important for applications. Furthermore, the optical probing diagnostic developed in WP2 allowed us to measure the ion acceleration process in real-time, for the first time. I recreated the experiment using state-of-the-art particle-in-cell simulations, which agreed excellently with the experiment. These results are currently being prepared for publication in a high impact journal.
WP4 was to investigate the acceleration of ions from long wave infrared driven solid targets. Due to covid-19 delays and travel restrictions, some change to the workplan here was required. I was unable to access the long wave infrared laser facility for this experiment, so instead I performed a related experiment at a different facility. A near-infrared laser was used to drive ion acceleration from thin targets. I was able to demonstrate record ion energies for the laser type, and used particle-in-cell simulations to elucidate the acceleration process. I am first author on a publication of this work, which is in press at Light | Science and Applications (IF 20.26) and has caused considerable excitement in my research community. At the same time, planning work was performed for the long wave infrared driven solid target experiment and an experiment will be performed soon (after the end of the project) to investigate the interaction.
WP5 was for dissemination and communication of the work. During the project, I had invited talks at some of the top conferences in my field, including the 63rd Annual Meeting of the American Physical Society - Division of Plasma Physics 2021 (8th November 2021), the 5th European Advanced Accelerator Concepts Workshop (21st September 2021), and the International Conference on High Energy Density Science 2021 (4th April 2021). I have further invites for upcoming conferences based on work performed during the project. I created a webpage to describe the project. I have had one first author publication accepted at Light | Science and Applications (IF 20.26) and two more in preparation.
This project has made significant progress beyond the state of the art. I have developed new types of diagnostics for investigating laser driven ion sources, with wide impact over research from laser driven sources beyond this project. I have taken the first real-time imaging of a laser driven gas ion source in action, something which has previously only been inferred from simulations and numerical calculation. I have also produced and investigated an extremely high energy ion source (> 60 MeV protons) from an ultra thin target, a technique which is directly transferable to a large number of laser facilities already operating.
These are important results with impact both in the research community of laser driven accelerators, but also are an important step forward for practical societal applications. The importance of the results has been recognised with multiple invited talks at top conferences in the field, and a paper being accepted in Light: Science & Applications (IF 20.26).
These are important results with impact both in the research community of laser driven accelerators, but also are an important step forward for practical societal applications. The importance of the results has been recognised with multiple invited talks at top conferences in the field, and a paper being accepted in Light: Science & Applications (IF 20.26).