Laser Based Particle Acceleration

Radiochromic film is used extensively in many medical, industrial, and scientific applications. In particular, the film is used in analysis of proton generation and in high intensity laser-plasma experiments where very high dose levels can be obtained. The present study reports calibration of the dose response of Gafchromic EBT3 and HD-V2 radiochromic films up to high exposure densities. A 2D scanning confocal densitometer system is employed to carry out accurate optical density measurements up to optical density 5 on the exposed films at the peak spectral absorption wavelengths. Various wavelengths from 400 to 740 nm are also scanned to extend the practical dose range of such films by measuring the response at wavelengths removed from the peak response wavelengths. Calibration curves for the optical density versus exposure dose are determined and can be used for quantitative evaluation of measured doses based on the measured optical densities. It was found that blue and UV waveleng...

The map of the radiation dose distribution has been determined experimentally inside the interaction chamber during high-power laser - thin solid target experiments. In addition, the map also has been assessed theoretically by performing 3D simulations. Maximum values of the integrated doses of tens of mGy/shot are recorded in a direction normal to the target, at a distance of about 30 cm apart from the laser-target interaction point. Monte-Carlo simulation of the radiation doses map around the laser-foil interaction point is performed using Geant4 General Particle Source code and the particular geometry chosen for the experimental setup. The computed radiation dose distribution shows a good agreement with experimental results, and this represents the most important progress made within the contract. We introduce a new method to increase the measurement resolution of the proton energy spectrum, based on using a stack of thin solid detectors, preferably CR-39 [OSIM Patent Application...

A nonperturbing probe that utilizes a focused ion beam has been developed to measure the position and profile of a tightly bunched charged particle beam (CPB). The ions are injected across the path of the CPB and are deflected by the electromagnetic field of the CPB. Deflected ions are detected by a gated microchannel plate detector and video camera. From the magnitude of the deflections, one can determine the position, radial profile, and in some cases, the axial length of the CPB. Ion parameters can be adjusted to tailor the probe to a wide range of CPB parameters, from submicron, ps bunches to millimeter-sized, quasicontinuous beams. We present the theory of operation of the probe, provide a number of numerical examples to illustrate its capabilities, and describe a proof-of-principle version of the probe that we built and successfully tested at SLAC. The experimental results obtained with this prototype version have shown the ion probe diagnostic to be feasible, reliable, and we...

The paper discusses some 3D simulations to compute the ionizing radiation dose during laser-plasma experiments leading to the generation of accelerated protons and electrons. Also, we suggest a new method to increase the measurement resolution of the proton energy spectrum. Monte-Carlo simulations of the radiation doses map around the laser-foil interaction point are performed using Geant4 General Particle Source code and the particular geometry chosen for the experimental setup. We obtain the map of the radiation dose distribution for high-power laser - thin solid target experiments, considering a cubic geometry of the interaction chamber. The computed radiation dose distribution shows a good agreement with various, previously obtained experimental results, and could be a step towards simulating the radiation environment inside of a spacecraft. To characterize the laser-plasma accelerated protons, we introduce a new method to enhance the measurement resolution of the proton energy spectrum by employing a stack of thin solid detectors, preferably CR-39. Each detector is thinner than the Bragg peak region on the Bragg curve that characterizes the loss of kinetic energy as a function of the particle penetration depth in the detector material. The relevance of this method for space radiation characterization and cybersecurity insurance is highlighted.

The first ionisation profile monitor ([PM) at DESY was installed at the end of 1988 shortly before the first run of the DESY III proton synchrotron. Extended versions of the IPM with amplifications from micro channel plates (MCP) were installed in PETRA II in 1989 and in HERA in 1991. These nondestructive monitors are working in vacuum conditions better than 10m8 mbar. Profiles are aquired at beam energies between 50 MeV and 480 GeV and current from 0.01 PA to 70 mA. The spatial resolution has been studied and is described in detail in this report. Readout is performed using phosphor screens viewed by various video cameras. The continuous video display at the operator console is very useful for beam studies and emittance measurements.

Purpose: Raman Scattering Spectra can be thought of as the "fingerprints" of the investigated material. The purpose of this work was to link the absorbed doses of irradiated radiochromic film at the micrometer level with changes in their Raman spectra.

Thesis status report - Oliver Deppert

In the context of the successful scientific break-even of the Inertial Confinement Fusion (ICF) campaigns demonstrated by the National Ignition Facility (NIF) future and alternative ignition concepts raises the intention of the laser-fusion community more then ever.

One promising candidate to achieve ignition during an early stage of the compression phase of the imploding fuel capsule is the so called proton Fast Ignition approach. In order to investigate this ignition scheme in more detail and to pave the way for future, high power kilojoule laser-target experiments fundamental scaling laws, especially for the proposed cone-guided hemispherical target geometry with scope on laser-to-proton conversion efficiency are needed.

In the scope of our work we have proposed an experimental campaign at the PHELIX laser-system at the Helmholtzzentrum für Schwerionenforschung, GSI in Darmstadt. The campaign aims at an better understanding of the conversion of laser energy in “usable” proton spectra. This is one important aspect to achieve highest proton flux in future high energy laser experiments. During the preparation phase of the experiment key diagnostics to complementary resolve proton spectra as well as the spatial proton distribution have been developed and fully characterized.

In the present work, we extend results of a previous paper [Peter et al., Phys. Plasmas 20, 12 3104 (2013)] and develop a semi-analytical model to account for thermal effects on the nonlinear dynamics of the electron beam in free-electron lasers. We relax the condition of a cold electron beam but still use the concept of compressibility, now associated with a warm beam model, to evaluate the time scale for saturation and the peak laser intensity in high-gain regimes. Although vanishing compressibilites and the associated divergent densities are absent in warm models, a series of discontinuities in the electron density precede the saturation process. We show that full wave-particle simulations agree well with the predictions of the model.

Charged particle therapy (CPT) is an advanced modality of radiation therapy which has grown rapidly worldwide, driven by recent developments in technology and methods of delivery. To ensure safe and high quality treatments, various instruments are used for a range of different measurements such as for quality assurance, monitoring and dosimetry purposes. With the emergence of new and enhanced delivery techniques, systems with improved capabilities are needed to exceed existing performance limitations of conventional tools. The Medipix3 is a hybrid pixel detector able to count individual protons with millisecond time resolution at clinical flux with near instant readout and count rate linearity. The system has previously demonstrated use in medical and other applications, showing wide versatility and potential for particle therapy. In this work we present measurements of the Medipix3 detector in the 60 MeV ocular proton therapy beamline at the Clatterbridge Cancer Centre, U.K. The be...

We present a study of the under-response of the new Gafchromic EBT3 films and a procedure to accurately perform 2D and 3D proton dosimetry measurements for both pristine and spread out Bragg peaks (SOBP) of any energy. These new films differ from the previous EBT2 generation by a slightly different active layer composition, which we show has not effected appreciably their response. The procedure and the beam quality correction factor curve have been benchmarked using 29 MeV modulated proton beams. In order to show the correction to apply when EBT3 films are used as treatment verification tools in anthropomorphic phantoms, two simulation studies involving clinical energies are presented: a SOBP for eye treatments and a SOBP to treat 20 cm deep and 5 cm thick tumours. We find maximum underresponses of 37%, 30% and 7.7% for the modulated 29 MeV beam, eye and deep tumour treatment, respectively, which were attained close to the end of the peak tails, due to a higher proportion of very low energy protons. The maximum deviations between corrected and uncorrected doses were for the three cases, respectively, 20.7%, 8.3% and 2.1% of the average dose across flat region of the SOBP. These values were obtained close to the distal edge of the SOBPs, where the proportion of low energy protons was not as high as on the tail, but there still was a number of protons high enough to deposit a reasonable amount of dose in the films.

Solid-state radiation detectors based on the photoluminescence of stable point defects in lithium fluoride crystals have been used for advanced diagnostics during the commissioning of the segment up to 27 MeV of the TOP-IMPLART proton linear accelerator for proton therapy applications, under development at ENEA C.R. Frascati, Italy. The LiF detectors high intrinsic spatial resolution and wide dynamic range allow obtaining twodimensional images of the beam transverse intensity distribution and also identifying the Bragg peak position with micrometric precision by using a conventional optical fluorescence microscope. Results of the proton beam characterization, among which, the estimation of beam energy components and dynamics, are reported and discussed for different operating conditions of the accelerator.

The energy distribution of electrons and ions emerging from the interaction of a few-cycle Gaussian laser pulse with spherical nanoclusters is investigated with the aim of determining prospects for accelerating ions in this regime. It is found that the direct conversion of laser energy into dense attosecond electron nanobunches results in rapid charge separation and early onset of Coulomb-explosion-dominated ion dynamics. The ion core of the cluster starts to expand soon after the laser has crossed the droplet, the fastest ions attaining 10 s of MeV at relativistic intensities. The current investigation should serve as a guide for contemporary experiments, i.e., using state-of-the-art few-cycle ultraintense lasers and nanoclusters of solid density. V

The Bragg Peak is a unique characteristic of ion beams which makes their use beneficial in cancer treatment as it allows the majority of dose deposition to be localised in a precise volume. The use of a laser system for particle acceleration is currently investigated as a potential alternative to the conventional RF accelerators currently used for hadrontherapy. The biological response of cells irradiated by high dose-rate laser-driven ions is currently being explored in this context. The experiment reported here was carried out as part of the A-SAIL project, a UK-wide collaboration aiming to develop innovative techniques for accelerating ions for future clinical applications. In this contest, a radiobiological experiment was carried out on the pico2000 laser beamline at LULI-École Polytechnique using an energetically spread, laseraccelerated proton beam. This paper will discuss the arrangement used in the experiment, and the techniques employed for an accurate estimation of the dose deposited, supported by Monte Carlo simulations of the particle propagation through the irradiation system.

The LILIA (Laser Induced Light Ions Acceleration) experiment is now running at the SPARCLAB facility of the Frascati INFN laboratories. The aim of LILIA is to study, design and verify a scheme which foresees the production, the characterization and the transport of a proton beam toward a stage of post acceleration (high frequency compact linac). A description of the experimental set up is given in this paper together with the first evidence of proton acceleration with the laser FLAME.

Heavy-ion induced nuclear reactions in materials exposed to energetic ions produced from highintensity (5 10 19 W=cm 2) laser-solid interactions have been experimentally investigated for the first time. Many of the radionuclides produced result from the creation of ''compound nuclei'' with the subsequent evaporation of proton, neutron, and alpha particles. Results are compared with previous measurements with monochromatic ion beams from a conventional accelerator. Measured nuclide yields are used to diagnose the acceleration of ions from laser-ablated plasma to energies greater than 100 MeV.

The study of the effects of the radiation dose on devices and materials is a topic of high interest in several fields, including radiobiology, space missions, microelectronics, and high energy physics. In this paper, a new method, based on radiochromic film dosimetry, is proposed for real-time dose assessment in radiation hardness assurance tests. This method allows for correlating the radiation dose at which devices are exposed to the radiation effects (malfunctioning and/or breakdown). In previous studies, it has already been demonstrated that a system, based on optical fibers and a spectrometer, allows for the real-time dose assessment of radiochromic films. The current study not only validates our previous results, but shows that it is possible to apply the new method to an actual radiation environment for the real-time measurement of the dose delivered to a device in radiation hardness assurance tests. This new dosimeter can be used in different radiation environments for a wid...

We present a systematic study of the ultrashort pulse laser driven acceleration of protons from thin targets of finite lateral size, so-called reduced mass targets (RMTs). Reproducible series of targets varying in size, thickness, and mounting geometry were manufactured with lithographic techniques. Irradiating these targets at the 150 TW Draco Laser facility of the Helmhotz-Zentrum Dresden-Rossendorf with ultrashort (30 fs) laser pulses of intensities of about 8×10 20 W/cm 2 , a robust maximum energy enhancement of almost a factor of two was found when compared to reference irradiations of plain foils of the same thickness and material. Furthermore, these targets exhibit a reduced performance dependence on target thickness compared to standard foils, which, based on detailed PIC simulations can be explained by the influence of the RMT geometry on the electron sheath. The performance gain was, however, restricted to lateral target sizes of about 50 μm which was attributed to edge and mounting structure influences. The contribution of the large electric fields at the target edges to the proton acceleration performance was investigated with measurements of the proton beam profile as well as optical pump and probe experiments.

A large fluence of ions (protons) was produced by using a single arm of the Aurora in a reversed polarity from its typical operation (4-5 MeV,8k Joules). A spatially and temporally homogeneous proton current density was produced over more than 300 cm 2. Electrons emitted from a tubular cathode impinged on a 2-rnil polyethylene foil producing the protons, whose depth-dose deposition could be controlled by the A-K spacing. A varietyofmeasurementtechniques; (1) electromagnetic, (2) radiachromic-depth-dose, (3) diamond PCD, (4) calorimetric, and (5) proton time-of-flight were used to verify these results. These techniques are described and the results discussed and compared.

The results of experiments devoted to studying the generation of MeV photons and protons in picosecond laser plasmas at a laser beam intensity of 10 18 W/cm 2 on Be, Ta, LiF and H 7 Li targets are presented. Nuclear reactions (γ, n) and (p, n) were used to detect MeV photons and protons. The number of MeV photons and protons generated in laser plasmas was found from the measured neutron yield. Possibilities of particle acceleration due to the formation of pinch structures in laser plasmas are discussed. Calculated and experimental results are compared.

The results of experiments devoted to studying the generation of MeV photons and protons in picosecond laser plasmas at a laser beam intensity of 10 18 W/cm 2 on Be, Ta, LiF and H 7 Li targets are presented. Nuclear reactions (γ, n) and (p, n) were used to detect MeV photons and protons. The number of MeV photons and protons generated in laser plasmas was found from the measured neutron yield. Possibilities of particle acceleration due to the formation of pinch structures in laser plasmas are discussed. Calculated and experimental results are compared.

Suitable instrumentation for laser-accelerated proton (ion) beams is critical for development of integrated, laser-driven ion accelerator systems. Instrumentation aimed at beam diagnostics and control must be applied to the driving laser pulse, the lasereplasma that forms at the target and the emergent proton (ion) bunch in a correlated way to develop these novel accelerators. This report is a brief overview of established diagnostic techniques and new developments based on material presented at the first workshop on 'Instrumentation for Diagnostics and Control of Laser-accelerated Proton (Ion) Beams' in Abingdon, UK. It includes radiochromic film (RCF), image plates (IP), micro-channel plates (MCP), Thomson spectrometers, prompt inline scintillators, time and space-resolved interferometry (TASRI) and nuclear activation schemes. Repetition-rated instrumentation requirements for target metrology are also addressed.

As a leading facility in laser-driven nuclear physics, ELI-NP will develop innovative research in the fields of materials behavior in extreme environments and radiobiology, with applications in the development of accelerator components, new materials for next generation fusion and fission reactors, shielding solutions for equipment and human crew in long term space missions and new biomedical technologies. The specific properties of the laser-driven radiation produced with two lasers of 1 PW at a pulse repetition rate of 1 Hz each are an ultra-short time scale, a relatively broadband spectrum and the possibility to provide simultaneously several types of radiation. Complex, cosmic-like radiation will be produced in a ground-based laboratory allowing comprehensive investigations of their effects on materials and biological systems. The expected maximum energy and intensity of the radiation beams are 19 MeV with 10 photon/pulse for photon radiation, 2 GeV with 10 electron/pulse for el...

Here we investigate how inserts of various densities (0.001 − 2.2 g/cm3) affect the dose distribution properties of VHEE beams at ∼150 MeV. A range variation comparison was also made with clinical proton beams using TOPAS/GEANT4 Monte Carlo simulations. In addition, we assess the viability of scattering foils for optimizing the size of VHEE beams for radiotherapy purposes. The experiments were conducted at CERN’s CLEAR user facility.

Here we investigate how inserts of various densities (0.001 − 2.2 g/cm3) affect the dose distribution properties of VHEE beams at ∼150 MeV. A range variation comparison was also made with clinical proton beams using TOPAS/GEANT4 Monte Carlo simulations. In addition, we assess the viability of scattering foils for optimizing the size of VHEE beams for radiotherapy purposes. The experiments were conducted at CERN’s CLEAR user facility.

A growing interest of the scientific community towards multidisciplinary applications of laser-driven beams has led to the development of several projects aiming to demonstrate the possible use of these beams for therapeutic purposes. Nevertheless, laser-accelerated particles differ from the conventional beams typically used for multiscipilinary and medical applications, due to the wide energy spread, the angular divergence and the extremely intense pulses. The peculiarities of optically accelerated beams led to develop new strategies and advanced techniques for transport, diagnostics and dosimetry of the accelerated particles. In this framework, the realization of the ELIMED (ELI-Beamlines MEDical and multidisciplinary applications) beamline, developed by INFN-LNS (Catania, Italy) and that will be installed in 2017 as a part of the ELIMAIA beamline at the ELI-Beamlines (Extreme Light Infrastructure Beamlines) facility in Prague, has the aim to investigate the feasibility of using laser-driven ion beams for multidisciplinary applications. In this contribution, an overview of the beamline along with a detailed description of the main transport elements as well as the detectors composing the final section of the beamline will be presented.

ELI-Beamlines is one of the four pillars of the ELI (Extreme Light Infrastructure) pan-European project. It will be an ultrahigh-intensity, high repetition-rate, femtosecond laser facility whose main goal is to generate and apply high-brightness X-ray sources and accelerated charged particles. In particular, medical applications are treated by the ELIMED task force, which has been launched by collaboration between ELI and INFN researchers. ELIMED aims to demonstrate the clinical applicability of laser accelerated ions. In this article, the state of the ELIMED project and the first scientific results are reported. The design and realisation of a preliminary beam handling system and of an advanced spectrometer for diagnostics of high energy (multi-MeV) laser-accelerated ion beams will also be briefly presented.

The Clatterbridge Cancer Centre (CCC) in the UK is a particle therapy facility providing treatment for ocular cancers using a 60 MeV passively scattered proton therapy beam. A model of the beamline using the Monte Carlo Simulation toolkit Geant4 has been developed for accurate characterisation of the beam. In order to validate the simulation, a study of the beam profiles along the delivery system is necessary. Beam profile measurements have been performed at multiple positions in the CCC beam line using both EBT3 GAFchromic film and Medipix3, a single quantum counting chip developed specifically for medical applications, typically used for x-ray detection. This is the first time its performance has been tested within a clinical, high proton flux environment. EBT3 is the current standard for conventional radiotherapy film dosimetry and was used to determine the dose and for correlation to fluence measured by Medipix3. The count rate linearity and doses recorded with Medipix3 were eva...

The Clatterbridge Cancer Centre (CCC) in the UK is a particle therapy facility providing treatment for ocular cancers using a 60 MeV passively scattered proton therapy beam. A model of the beamline using the Monte Carlo Simulation toolkit Geant4 has been developed for accurate characterisation of the beam. In order to validate the simulation, a study of the beam profiles along the delivery system is necessary. Beam profile measurements have been performed at multiple positions in the CCC beam line using both EBT3 GAFchromic film and Medipix3, a single quantum counting chip developed specifically for medical applications, typically used for x-ray detection. This is the first time its performance has been tested within a clinical, high proton flux environment. EBT3 is the current standard for conventional radiotherapy film dosimetry and was used to determine the dose and for correlation to fluence measured by Medipix3. The count rate linearity and doses recorded with Medipix3 were eva...

In-beam dose measurements are paramount for any application seeking to harness the effects of the radiation beam, so all the future applications of the laser accelerated beams (as generated in the ELI and CETAL projects) will need such measurements. With a very long history in measuring doses in charged particle beams, the medical and industrial applications setup a number of methods that could be also used for the dosimetry of the beams generated by laser pulses. Dose measurements rely heavily on what is seen as the gold standard in dose measurement: the ion chambers. Ion chambers have both limitations and advantages, and in our case the disadvantage could be the large number of corrections to be applied in order to calculate a correct dose from the measured charge. The ELIDOSE project tries to address these problems by proposing an array detector that would allow the simultaneous measurement of the recombination and polarity corrections, and of the dose. The detector consists of f...

As a leading facility in laser-driven nuclear physics, ELI-NP will develop innovative research in the fields of materials behavior in extreme environments and radiobiology, with applications in the development of accelerator components, new materials for next generation fusion and fission reactors, shielding solutions for equipment and human crew in long term space missions and new biomedical technologies. The specific properties of the laser-driven radiation produced with two lasers of 1 PW at a pulse repetition rate of 1 Hz each are an ultra-short time scale, a relatively broadband spectrum and the possibility to provide simultaneously several types of radiation. Complex, cosmic-like radiation will be produced in a ground-based laboratory allowing comprehensive investigations of their effects on materials and biological systems. The expected maximum energy and intensity of the radiation beams are 19 MeV with 10 photon/pulse for photon radiation, 2 GeV with 10 electron/pulse for el...

This contribution describes the first results obtained within the iMPACT project, which aims to build a novel proton computed-tomography (pCT) scanner for protons of energy up to 230 MeV, as used in hadron therapy. The iMPACT pCT scanner will improve the current state-of-the-art in proton tracking at all levels: speed, spatial resolution, material budget, and cost. We will first describe the design of the iMPACT scanner, which is composed by a tracker and a range calorimeter. We will then illustrate the results of a test with the ALPIDE sensor, a monolithic active pixels sensor, developed by the ALICE collaboration, which will equip the iMPACT tracker in this first phase. We finally detail the characterization building elements of the prototype of the range calorimeter, which is composed of segmented scintillator fingers readout by SiPMs. Reported beam-test data will highlight how the technological choices we made well address the performances of a state-of-the-art pCT system.

Fast electron injection and transport in solid foils irradiated by sub-picosecond-duration laser pulses with peak intensity equal to 4 Â 10 20 W=cm 2 is investigated experimentally and via 3D simulations. The simulations are performed using a hybrid-particle-in-cell (PIC) code for a range of fast electron beam injection conditions, with and without inclusion of self-generated resistive magnetic fields. The resulting fast electron beam transport properties are used in rear-surface plasma expansion calculations to compare with measurements of proton acceleration, as a function of target thickness. An injection half-angle of $50 À 70 is inferred, which is significantly larger than that derived from previous experiments under similar conditions. V

The main direction proposed by the community of experts in the field of laser-driven ion acceleration is to improve particle beam features (maximum energy, charge, emittance, divergence, monochromaticity, shot-to-shot stability) in order to demonstrate reliable and compact approaches to be used for multidisciplinary applications, thus, in principle, reducing the overall cost of a laser-based facility compared to a conventional accelerator one and, at the same time, demonstrating innovative and more effective sample irradiation geometries. The mission of the laser-driven ion target area at ELI-Beamlines (Extreme Light Infrastructure) in Dolní Břežany, Czech Republic, called ELI Multidisciplinary Applications of laser-Ion Acceleration (ELIMAIA) , is to provide stable, fully characterized and tuneable beams of particles accelerated by Petawatt-class lasers and to offer them to the user community for multidisciplinary applications. The ELIMAIA beamline has been

We show efficient laser driven proton acceleration up to 14 MeV from a 50 µm thick cryogenic hydrogen ribbon. Pulses of the short pulse laser ELFIE at LULI with a pulse length of ≈ 350 fs at an energy of 8 J per pulse are directed onto the target. The results are compared to proton spectra from metal and plastic foils with different thicknesses and show a similar good performance both in maximum energy as well as in proton number. Thus, this target type is a promising candidate for experiments with high repetition rate laser systems.

Suitable instrumentation for laser-accelerated proton (ion) beams is critical for development of integrated, laser-driven ion accelerator systems. Instrumentation aimed at beam diagnostics and control must be applied to the driving laser pulse, the lasereplasma that forms at the target and the emergent proton (ion) bunch in a correlated way to develop these novel accelerators. This report is a brief overview of established diagnostic techniques and new developments based on material presented at the first workshop on 'Instrumentation for Diagnostics and Control of Laser-accelerated Proton (Ion) Beams' in Abingdon, UK. It includes radiochromic film (RCF), image plates (IP), micro-channel plates (MCP), Thomson spectrometers, prompt inline scintillators, time and space-resolved interferometry (TASRI) and nuclear activation schemes. Repetition-rated instrumentation requirements for target metrology are also addressed.

The electron beam emitted from the back of Plasma Focus devices is being studied as a radiation source for IORT (IntraOperative Radiation Therapy) applications. A Plasma Focus device is being developed to this aim, to be utilized as an X-ray source. The electron beam is driven to impinge on 50 µm brass foil, where conversion X-rays are generated. Measurements with gafchromic film are performed to analyse the attenuation of the X-rays beam and to predict the dose given to the culture cell in radiobiological experiments to follow.