Introduction The expansion of our PET isotope production with a new TR-19 cyclotron necessitated a suitable solid target transport system. None of the known existing and proposed solid target transport systems (STTS) was able to meet the technical and budget requirements of the MIR cyclotron facility [5]. A unique carrier design allowed us to develop a fully automated 50.8 mm inner diameter pneumatic tube STTS with an in-hot-cell compact form factor receiving station. The cyclotron or vault side loading station is a mere vertically symmetric version of the in-hot-cell station. The carrier is able to accommodate any of our inhouse developed 86Y, 64Cu, 76Br, 89Zr and 99mTc target holders without further modifications. Material and Methods Technical constraints were imposed by the dimensions of the target holders (FIG. 1) and the overall station size (FIG. 3). A receiving station would be inside a hot cell and, up to three sending stations would be located in the confined vault space under the solid target irradiation units. In addition, safety and budget requirements demanded a fully automated, easy to maintain STTS. The target holders are of various geometries with the 99mTc having the maximum dimension of 46.65 mm along its diagonal. Pseudo carriers with diameters ranging from 41 to 49.5 mm (no wear band) and lengths from 50.8 to 102 mm were tested on 50.8 mm inner diameter Kuriyama Tigerflex™ and Goodyear Nutriflex™ tubing. Smaller diameter and length test samples became wobbly, slow, and were getting stuck on occasion. Lengths in the upper limits became stuck in turns with radii close to the minimum radius of the tubing. The necessary negative pressure was achieved by employing a 2.5pHP Ridgid WD06250 blower. The transparent Goodyear Nutriflex™ tubing was chosen for the further STTS development. A carrier capable of loading and unloading regardless of its axial orientation was constructed. This novel design allows for a relatively compact station W 112 × H 220 × L 300, which reduce the dependence on the location of the tube openings in the walls of the hot cell (BqSv, Taiwan). As a result the station can be conveniently placed in areas not typically occupied by processing modules or used by chemists, e.g. close to the upper left corner. To avoid reliance on expensive proprietary parts, all components were designed or chosen to insure reliability with minimal maintenance. The enclosure and opening mechanism are 3D-printable using ABS plastic, and can be made in-house on demand. “Platform sharing” between hot cell and vault stations further simplifies support and maintenance. As with the mechanical hardware, the electronic components and boards were selected to minimize the dependency on a single supplier. The main controller board is based on Atmel\'s AVR series of microcontrollers, which are known to be largely backward compatible, well documented and have an extensive user support base. A single “brick” controls up to three stations. Bricks can be daisy chained with one functioning as a master. The control software takes advantage of the rapid development capabilities of National Instrument\'s LabView graphical language. It is intended to work on Unix-like and Windows operating systems as well as to allow control from hand-held devices. Password security, interlocks and traceability follow the accepted safety standards for radioisotope handling. Results and Conclusion The Symmetric STTS has proven characteristics of reliability, ease of use and safety over hundreds of runs. Given that no convenient carting path exists, it is the ideal means for bringing solid target holders from the underground cyclotron vault to the chemistry processing hot cells at ground level. Transported activities are less than 37.0 GBq (1.0 Ci) for 64Cu and 3.7 GBq (100 mCi) for 89Zr. Carrier velocity is about 4.7m/s minimizing the time activity is present between cyclotron and hot cell. No human interaction with the irradiated target is needed during transport. The carrier does not need to be taken out of the STTS. Even though the BqSv hot cells are equipped with teletongs, they are not needed to recover the target when it arrives at the hot cell; the target is directly dropped into the processing module, e.g. the dissolution vessel for 64Cu processing. The software is engineered in a manner that gives the operator full control of the states of the sending and receiving stations. At the same time, it avoids graphically dense and overloaded GUI in order to reduce the probability of human error. Currently the control program runs on a PC/Laptop and communicates with the controller over USB. LabView provides add-ons that allow control with a tablet or other hand-held (under development). The fully automated symmetric STTS is ideal for isotope production facilities that are being envisioned, conceptualized or are in their planning stage. Its versatility, low initial and operating costs might even justify deployment in facilities which already employ a less optimal solid target transport. Invention application for the Symmetric STTS was filed with the Office of Technology Management of Washington University in Saint Louis, Missouri, USA.

Introduction The Comecer ALCEO Metal system is intended to be a comprehensive solid targetry system, capable of all steps necessary to produce copper isotopes (60Cu, 61Cu & 64Cu) from enriched nickel: plating, transfer to/from cyclotron, irradiation, and dissolution/purification. To develop plating and chemistry methods, we plate natural nickel, and irradiate with deuterons to produce 61Cu. This alleviates the need for expensive enriched nickel isotopes, but gives a lower activity yield. We report a few issues with the ALCEO system, and some of our modifications. Material and Methods BRIEF DESCRIPTION OF SYSTEM: The ALCEO system uses cylindrical shuttles (dia 28 mm, height 35 mm) comprised of an Al body with a Pt well, onto which the Ni is plated. Shuttles are transferred pneumatically from the hot cell to the irradiation module, on the end of the cyclotron beamline. The plating and dissolution are both done at the electrochemical cell, located in the hot cell. This cell is connected by capillary tubes to the electrolytic solution reservoir (for plating), or the acid reservoir (for dissolution). These tubes form a recirculation loop, through which the fluid is propelled by an inline micropump throughout plating and dissolution. The platinum well is 16 mm in diameter, while an O-ring is used to plate only the center (6 mm in diameter). A constant DC voltage is applied. PLATING: We dissolve natural nickel nitrate (99.999% pure) into an electrolytic solution comprised of deionized water, ammonium hydroxide and ammonium chloride (pH = 9.3). We use 30–100 mg of natNi in a 10mg/mL solution. We have varied the ALCEO electrochemical cell voltage between 2.25–3 VDC, and tried to maintain a low pump flow rate between 1–2 mL/min. The electrochemical cell uses a fixed metal tube as the anode (~3mm above the plating surface). This tube also delivers the electrolytic plating solution to the Pt surface, forming part of the recirculating loop. The Pt surface is in contact with a gold-plated cathode. Due to issues discussed below, we have built a custom plating rig for the ALCEO shuttles, which does not use the pump/recirculation loop, but leaves the reservoir of electrolytic solution in place, atop the plating surface. A graphite rod is used for the anode, rotating offcenter ~2mm above the plating surface. We use the same size O-ring to plate only the center 6 mm of the Pt surface, and apply a constant DC voltage. TRANSFER TO/FROM CYCLOTRON: The pneumatic transfer tube is 50 ft long between the hot cell and the cyclotron vault, and has a rise of 14 ft from under the floor to the ceiling of the cyclotron vault. IRRADIATION: The ALCEO irradiation module holds the plating surface orthogonal to the beam path. The module has a 10-mil-thick (0.010”) Al front foil, supported by a hex-grid. Once we realized the thickness, we replaced this with a 1-mil-thick Al foil, followed by a 1-mil-thick Havar foil. The foil is cooled by a flow of helium, while the shuttle and grid are cooled by a flow of water. The helium and water are cooled in heat ex-changers by chilled water. As initially plumbed, the chilled water flowed through the heat ex-changers in series, cooling the helium first, then the water. After initial runs, we plumbed the heat exchangers in parallel, teeing the chilled water to the supply of each heat exchanger, and teeing the returns together. Irradiation is performed with a PETtrace 800 accelerating deuterons to 8.4 MeV on target. The beam current limit is 20 μA for the ALCEO Metal target. A set point of 19 μA is used to avoid the system tripping off. DISSOLUTION/PURIFICATION: The ALCEO system circulates 5 mL of 6M HCl, while heating the shuttle to 100 ⁰C for 40 min. This solution is loaded onto a column containing 10 g of 200–400 mesh chromatographic resin in chloride form. A separation is performed yielding three solutions: The column is washed with 40 mL of 6M HCl to obtain the Recovered Nickel Solution, then 20 mL of 4M HCl to obtain the Cobalt Solution, then 10 mL of 0.5M HCl to obtain the Cop-per Product Solution. Results and Conclusion PLATING: Using the ALCEO method, the platings obtained had a tendency to mound, (up to 0.75 mm thick for 50 mg) giving a lower density of 3–4 g/cm3. This was attributed to the anode tube being fixed in place over the center of the plating surface. Using the custom rig, almost no mounding was observed, (0.25mm thick for 50 mg) giving a density of 7 g/cm3, closer to nickel’s nominal density of 8.9 g/cm3. FIGS. 1 and 2 attempt to show the mounding from the ALCEO method, and relative flatness from the custom rig. Both methods give a rough, or “fuzzy” plated surface. FIG. 2 shows that the custom rig exaggerates this “fuzziness”. Using the ALCEO method, a slower pump speed (~1 mL/min) gives a smoother plating surface, but the pump has a tendency to lock up at this lower set point, stalling the plating. Using the ALCEO method, slight increases in the voltage (2.65 V instead of 2.25 V), can form thin stalagmites of nickel, electrically connecting the anode and the plating surface, ending the chance for a useable plating. Using the custom rig, no stalagmites are seen, adjusting the voltage from 2.3 to 3.0 V. This leads to the potential for a faster plating. Both the ALCEO method and the custom rig have obtained plating efficiencies of 95 %. TRANSFER TO/FROM CYCLOTRON: The shuttle typically transfers without issue in < 15 seconds. Once or twice it has remained in the transfer tube, but been retrieved by cycling the com-pressed air/vacuum a couple of times. IRRADIATION: During initial testing, the temperature of the return water rose rapidly during irradiation. This was attributed to the chilled water already gaining heat from the helium heat exchanger. Once the parallel chilled water plumbing was implemented, the water temperature rose much more slowly. Initial testing with the 10-mil Al foils gave a very poor activity yield. The 1-mil Al foil ruptured under the 20 psi helium pressure before beam was applied. The 1-mil Havar foil produced 1.57 mCi of 61Cu at EOB, giving an activity yield of 0.308 mCi/μAh (results summarized in TABLE 1). This compares to yields of 1.4 obtained by [1], and 0.29 obtained by [2] for deuterons on natNi. DISSOLUTION/PURIFICATION: The dissolution in 6M HCl is close to 100% efficient by weight. After purification, the three solutions were assayed by dose calibrator as summarized in TABLE 2. The purification is very efficient at removing the starting material, and long-lived Co isotopes from the Copper Product Solution, as seen with the 57-hour EOB measurements. However, much of the desired 61Cu is removed as well, with only 32% remaining in the product. The lack of nuclide impurities in the Copper Product Solution was confirmed by gamma spectroscopy using a HP-Ge detector.

No description available.

Rhenium-186 has a half-life (t1/2 = 3.72 days) and emission of both gamma and beta particles that make it very attractive for use as a theranostic agent in targeted radionuclide therapy. 186Re can be readily prepared by the 185Re(n,γ)186Re reac-tion1. However, that reaction results in low specific activity, severely limiting the use of reactor produced 186Re in radiopharmaceuticals. It has previously been shown that high specific activity 186Re can be produced by cyclotron irradiations of 186W with protons and deuterons2,3. In this investigation we evaluated the 186W(d,2n)186Re reaction using thick target irradiations at higher incident deuteron energies and beam currents than previously reported. We elected not to use copper or aluminum foils in the preparation of our 186W targets due to their activation in the deuteron beam, so part of the investigation was an evaluation of an alternate method for preparing thick targets that withstand μA beam currents. Irradiation of 186W. Initial thick targets (~600-1100 mg) were prepared using 96.86% enriched 186W by hydraulic pressing (6.9 MPa) of tungsten metal powder into an aluminum target support. Those thick targets were irradiated for 10 minu-tes at 10 µA with nominal extracted deuteron energies of 15, 17, 20, 22, and 24 MeV. Isolation of 186Re. Irradiated targets were dissolved with H2O2 and basified with (NH4)2CO3 prior to separation using column(s) of ~100–300 mg Analig Tc-02 resin. Columns were washed with (NH4)2CO3 and the rhenium was eluted with ~80˚C H2O. Gamma-ray spectroscopy was per-formed to assess production yields, extraction yields, and radionuclidic byproducts. Recycling target material. When tested on a natural abundance W target, recovery of the oxidized WO4- target material from the resin was found to proceed rapidly with the addition of 4M HCl in the form of hydrated WO3. The excess water in the WO3 was then removed by calcination at 800 °C for 4 hours. This material was found to undergo reduction to metallic W at elevated temperatures (~1550 °C) in a tube furnace under an inert atmosphere (Ar). Quanti-fication of % reduction and composition analyses were accomplished with SEM, EDS, and XRD and were used to characterize and compare both the WO3 and reduced Wmetal products to a sample of commercially available material. Structural enhancement by surface annealing. In some experiments ~1 g WO3 pellets were prepared from Wmetal that had been chemically treated to simulate the target material recovery process described above. Following calcination, the WO3 was allowed to cool to ambient temperature, pulverized with a mortar and pestle and then uniaxially pressed at 13.8 MPa into 13 mm pellets. Conversion of the WO3 back to Wmetal in pellet form was accomplished in a tube furnace under flowing Ar at 1550 °C for 8 hours. Material characterization and product composition analyses were conducted with SEM, EDS, and XRD spectroscopy. Graphite-encased W targets. Irradiations were conducted at 20 μA with a nominal extracted deuteron energy of 17 MeV using thick targets (~750 mg) of natural abundance tungsten metal powder uniaxially pressed into an aluminum target support between layers of graphite pow-der (100 mg on top, 50 mg on the bottom). Targets were then dissolved as previously described and preliminary radiochemical isola-tion yields obtained by counting in a dose calibrator. Although irradiations of W targets were possible at 10 μA currents, difficulties were encountered in maintaining the structural integrity of the full-thickness pressed target pellets under higher beam currents. This led to further investigation of the target design for irradiations conducted at higher beam currents. Comprehensive target material characterization via analysis by SEM, EDS, XRD, and Raman Spectroscopy allowed for a complete redesign of the target maximizing the structural integrity of the pressed target pellet without impacting production or isolation. At the 10 A current, target mass loss following irradiation of an enriched 186W target was < 1 % and typical separation yields in excess of 70 % were observed. Saturated yields and percent of both 183Re (t½ = 70 days) and 184gRe (t½ = 35 days) relative to 186gRe (decay corrected to EOB) are reported in TABLE 1 below. The reason for the anomalously low yield at 24 MeV is unknown, but might be explained by poor beam alignment and/or rhenium volatility during irradiation. Under these irradiation conditions, recovery yields of the W target material from the recycling process were found to be in excess of 90% with no discernable differences noted when compared to commercially available Wmetal and WO3. Conceptually, increasing the structural integrity of pressed WO3 targets by high temperature heat treatment under an inert atmosphere is intriguing. However, the treated pellets lacked both density and structural stability resulting in disintegration upon manipulation , despite the initially encouraging energy dispersive X-ray spectroscopy (EDS) determination that 94.9% percent of the WO3 material in each pellet had been reduced to metallic W. The use of powdered graphite as a target stabi-lizing agent provided successful irradiation of natural abundance W under conditions where non-stabilized targets failed (20 µA at 17 MeV for 10 minutes). Target mass loss following irradiation of a natW target was < 1 % and a separation yield in excess of 97 % was obtained. In conclusion, the theranostic radionuclide 186Re was produced in thick targets via the 186W(d,2n) reaction. It was found that pressed W metal could be used for beam currents of 10 μA or less. For deuteron irradiations at higher beam currents, a method involving pressing W metal between two layers of graphite provides increased target stability. Both target configurations allow high recovery of radioactivity from the W target material, and a solid phase extraction method allows good recovery of 186Re. An effective approach to the recycling of enriched W has been developed using elevated temperature under an inert atmosphere. Further studies are underway with 186W targets sandwiched by graphite to assess 186Re production yields, levels of contaminant radiorhenium, power deposition, and enriched 186W material requirements under escalated irradiation conditions (20 µA and 17 MeV for up to 2 hours).

Introduction The COSTIS system is a commercially available target station for the irradiation of solid targets. Up to 3 targets can be provided for irradiation by a slot system. In standard setup the target can be ejected via a pneumatically driven piston system. The target is then allowed to drop down into an open lead container, which can be closed remotely afterwards. The described procedure is well established and reliable. But the concept is limited to low dose targets and environments. The required entering of the cyclotron vault for manual pick up of the container at the cyclotron and the light 18 mm Pb lead shielding of the container itself cause exposure risk for the personnel after long term irradiations with highly activated cyclotron parts and target. The purpose of this work was the design of an alternative for the pickup and the transport of irradiated targets to minimize the radiation dosage of the personnel during manual handling of the COSTIS-lead container. Principle The new designed transport system still uses the software controlled target ejection function of the COSTIS/IBA-system. With ejection the target capsule is allowed to fall into a PTFE-container. To assure a safe target drop into the PTFE container, the gap between the target guiding plate and the PTFE container is smaller than d/2 of the target capsule. After target ejection the PTFE-container can be transferred remotely from target ejection position (1) to the loading station (2) with a target slide. The loading station allows the transfer of the PTFE container remotely into a lead container (60 mm Pb). Now the vault door is used as carrier of the Pb-container. For this purpose a proper fixture for the Pb-container is mounted at the front side of the vault door and via opening the vault door the container is safely transported out of the vault. Outside the container will be finally closed with a lid and transferred to a trolley for further handling. Due to positioning of the container at a certain altitude together with the deep positioning of the target coin inside of the container, the subsequent closing of the container does not cause significant dosage, a more complicated automatic closing system is not mandatory. After replacement of the lead container further transfers can be executed without entering the vault. For this purpose the exchanged Pb-container is placed at the loading station by closing the vault door and a new PTFE-container will be transferred remotely from a magazine onto the target slide, which again can be re-motely positioned at target ejection position. The magazine of PTFE-Containers holds two replacements in accordance with the maximal capacity of the target slot system of the COSTIS station. The remote system of the transport unit uses redundant feedback signals for a reliable and safe operation. Results and Conclusion The newly implemented transport system allows a significant reduction of the radiation dose during pickup and transport of the irradiated solid targets. No entering of the vault is needed after irradiation. The system is highly reliable due to its redundant and straightforward design (2-fold position switches and photoelectric barriers). Due to fixed attachment points in the vault and at the BTL the mobile unit can be easily removed or mounted. The system is maintenance free and all parts easy accessible. For further handling of the targets lead containers were design to fit in the transfer locks of hot cells. The transfer can be carried out directly from the trolley. Container lid and PTFE container are suited for manipulator handling in hot cells.

The Bethe-Weizsäcker cycle consists of a set of nuclear reactions that convert hydrogen into helium and release energy in the stars. It determines the luminosity of low-metal stars at their turn-off from the main-sequence in the Hertzsprung-Russel diagram, so its rate enters the calculation of the globular clusters’ age, an independent lower limit on the age of the universe. The cycle contributes less than 1% to our Sun’s luminosity, but it produces neutrinos that can in principle be measured on Earth in underground experiments and bring direct information of the physical conditions in the solar core, provided that the nuclear reaction rate is known with sufficient precision. The 14N(p,γ)15O reaction is the slowest reaction of the Bethe-Weizs¨acker cycle and establishes its rate. Its cross section is the sum of the contributions by capture to different excited levels and to the ground state in 15O. Recent experiments studied the region of the resonance at Ep = 278 keV. Only one modern data set from an experiment performed in 1987 is available for the high-energy domain. Both energy ranges are needed to constrain the fit of the excitation function in the R-matrix framework and to obtain a reliable extrapolated S-factor at the very low astrophysical energies. The present research work studied the 14N(p,γ)15O reaction in the LUNA (Laboratory for Underground Nuclear Astrophysics) underground facility at three proton energies 0.36, 0.38, 0.40MeV, and in Dresden in the energy range Ep = 0.6 - 2MeV. In both cases, an intense proton beam was sent on solid titanium nitride sputtered targets, and the prompt photons emitted from the reaction were detected with germanium detectors. At LUNA, a composite germanium detector was used. This enabled a measurement with dramatically reduced summing corrections with respect to previous studies. The cross sections for capture to the ground state and to the excited states at 5181, 6172, and 6792 keV in 15O have been determined. An R-matrix fit was performed for capture to the ground state, that resolved the literature discrepancy of a factor two on the extrapolated S-factor. New precise branching ratios for the decay of the Ep = 278 keV resonance were measured. In Dresden, the strength of the Ep = 1058 keV resonance was measured relative to the well-known resonance at Ep = 278 keV, after checking the angular distribution. Its uncertainty is now half of the error quoted in literature. The branching ratios were also measured, showing that their recommended values should be updated. Preliminary data for the two most intense transitions off resonance are provided. The presence in the targets of the other stable nitrogen isotope 15N with its well- known isotopic abundance, allowed to measure the strength of two resonances at Ep = 430 and 897 keV of the 15N(p,αγ)12 C reaction, improving the precision for hydrogen depth profiling.

The Bethe-Weizsäcker cycle consists of a set of nuclear reactions that convert hydrogen into helium and release energy in the stars. It determines the luminosity of low-metal stars at their turn-off from the main-sequence in the Hertzsprung-Russel diagram, so its rate enters the calculation of the globular clusters’ age, an independent lower limit on the age of the universe. The cycle contributes less than 1% to our Sun’s luminosity, but it produces neutrinos that can in principle be measured on Earth in underground experiments and bring direct information of the physical conditions in the solar core, provided that the nuclear reaction rate is known with sufficient precision. The 14N(p,γ)15O reaction is the slowest reaction of the Bethe-Weizs¨acker cycle and establishes its rate. Its cross section is the sum of the contributions by capture to different excited levels and to the ground state in 15O. Recent experiments studied the region of the resonance at Ep = 278 keV. Only one modern data set from an experiment performed in 1987 is available for the high-energy domain. Both energy ranges are needed to constrain the fit of the excitation function in the R-matrix framework and to obtain a reliable extrapolated S-factor at the very low astrophysical energies. The present research work studied the 14N(p,γ)15O reaction in the LUNA (Laboratory for Underground Nuclear Astrophysics) underground facility at three proton energies 0.36, 0.38, 0.40MeV, and in Dresden in the energy range Ep = 0.6 - 2MeV. In both cases, an intense proton beam was sent on solid titanium nitride sputtered targets, and the prompt photons emitted from the reaction were detected with germanium detectors. At LUNA, a composite germanium detector was used. This enabled a measurement with dramatically reduced summing corrections with respect to previous studies. The cross sections for capture to the ground state and to the excited states at 5181, 6172, and 6792 keV in 15O have been determined. An R-matrix fit was performed for capture to the ground state, that resolved the literature discrepancy of a factor two on the extrapolated S-factor. New precise branching ratios for the decay of the Ep = 278 keV resonance were measured. In Dresden, the strength of the Ep = 1058 keV resonance was measured relative to the well-known resonance at Ep = 278 keV, after checking the angular distribution. Its uncertainty is now half of the error quoted in literature. The branching ratios were also measured, showing that their recommended values should be updated. Preliminary data for the two most intense transitions off resonance are provided. The presence in the targets of the other stable nitrogen isotope 15N with its well- known isotopic abundance, allowed to measure the strength of two resonances at Ep = 430 and 897 keV of the 15N(p,αγ)12 C reaction, improving the precision for hydrogen depth profiling.

Cette thèse expérimentale est consacrée à l’optimisation d’une source de rayons X Kalpha générée par interaction laser femtoseconde à fort contraste temporel avec une cible épaisse en molybdène. Ce travail vise à explorer l’effet du contraste temporel sur l’émission Kalpha sur une gamme d’intensité combinant les deux régimes relativiste et non-relativiste. La première étude est consacrée à l’évolution de l’émission Kalpha en fonction du contraste temporel et de l’intensité. L’étude a révélé différents comportements de l’émission Kalpha suivant la valeur du contraste et d’intensité. L’étude a aussi montré une émission Kalpha indépendante du contraste dans le régime relativiste. Au regard des travaux de la littérature, nous avons proposé une première interprétation des résultats obtenus. Il s’agit d’établir un lien entre l’émission Kalpha et les mécanismes d’absorption de l’énergie laser. Certains mécanismes sont dépendants de l’angle d’incidence. Afin d’appuyer notre interprétation, une deuxième étude du rendement de la source Kalpha en fonction de l’angle d’incidence a été réalisée. Ainsi les résultats obtenus sont en accord avec certaines de nos conclusions. En outre, Nous nous sommes intéressés à l’effet de l’étirement temporel de l’impulsion. Nous avons observé une sensibilité de l’émission suivant le signe du chirp. Enfin, nous avons étudié l’effet du contraste et de l’intensité sur la taille de la source X. Celle-ci est d’autant plus réduite que le contraste est plus fort et devient très proche de la tache focale laser à faible intensité laser. Le rendement de production en photon Kalpha atteint est de 2 × 10^−4, similaire au meilleur rendement reporté à ce jour. / This thesis is focused on the optimization of a Kalpha x-ray source induced by high contrast femtosecond laser molybdenum thick target interaction. The objective of this work is to explore the effect of the temporal contrast ratio on Kalpha emission in an intensity range including the non relativistic and relativistic regimes. The first study consists of the measurement of Kalpha emission as a function of contrast ratio and intensity. The study shows different behaviors of the emission depending on the contrast ratio and intensity range. Furthermore, it was found that in the relativistic regime Kalpha production is independant of the contrast ratio. According to published work in litterature, we proposed a first intepretation of the obtained results. In particular, we discuss the absorption mechanism of laser pulse energy for each contrast ratio and intensity condition. Some of the mechanisms are dependant on the angle of incidence of the pulse on target. Thus, to verify the validity of our interpretation, we study the Kalpha effciency as a function of the angle of incidence. Most of the results agree with our first conclusions. Furthermore, we investigate the effect of the chirped pulse of the Kalpha emission. It is shown that Kalpha emission is sensitive to the sign of the chirp. Finally, we performed a study on the effect of contrast ratio and intensity on the x-ray source size. It was observed that high contrast ratio decreases strongly the x-ray source size which aproaches the focal spot size at low laser intensity. High Kalpha efficiency is reached 2 × 10^−4 which is similar to the highest effciency reported to date in litterature for a thick molybdenum target.

Cette thèse porte sur la caractérisation des champs magnétiques générés par l'interaction entre un laser d'intensité de 1017 W/cm2 à 1018 W/cm2 et de cibles solides, et leurs effets sur le faisceau d'électrons chauds. En effet, les différents champs magnétiques créés lors de cette interaction ont un rôle fondamental sur les caractéristiques du faisceau d'électrons chauds : sa source et son transport dans la matière. Des diagnostics de polarimétrie et d'interférométrie croisée ont été développés lors de cette thèse pour observer le champ magnétique en surface de la cible irradiée par laser et en particulier leurs évolutions spatiale et temporelle. Deux différents régimes ont été observés selon le contraste en intensité de l'impulsion laser : un possédant une montée rapide de champ magnétique suivie d'une décroissance plus lente créées par le déplacement des électrons chauds dans la matière, et un possédant une croissance plus lente de forme logarithmique créée par la pré-impulsion du laser par effet thermoélectrique. L'interprétation de nos résultats obtenues par ces diagnostics ont permis d'évaluer la résistivité du plasma. Cette résistivité nommée anormale dans la littérature se comprend en estimant l'influence du champ magnétique sur l'anisotropie du transport des électrons et donc sur la résistivité. Le dernier diagnostic permettant l'estimation du champ magnétique détaillé dans cette thèse est la déflectométrie protonique. Elle permet d'observer la déviation d'un faisceau de protons lors de sa propagation sous l'effet de champs électrique et magnétique. D'autres expériences se sont focalisées sur la divergence de ce faisceau d'électrons. Deux diagnostics principaux ont été utilisés : l'imagerie K α et l'imagerie du rayonnement de transition cohérente (C.T.R.) en face arrière de cibles. / This thesis concerns magnetic fields, generated by the interaction between strong laser pulse (intensity up to1018 W/cm2) and solid target, and their effects on the fast electron beam. Indeed, the various magnetic fields created during this interaction can inuence the divergence of the fast electron beam. The magnetic field createdduring this interaction have a fundamental role on the fast electron beam characteristics : its source and its transportin the material. Diagnotics of polarimetry and crossed interferometry were developed during this thesis to observethe on-surface magnetic field of the target, and in particular, their spatial and temporal evolutions. Two types oftemporal evolution of the magnetic field were observed according to the contrast in intensity of the laser pulse : afast rise of magnetic field followed by a slower decrease created by the travel of the fast electrons in the material,and a slower growth of logarithmic form created by the pre-pulse of the laser by thermoelectric effect. The interpretation of our results obtained by these diagnotics allowed us to estimate the resistivity of the plasma.This resistivity named "anomalously high resistivity" in the literature can be explained by taking into account theinuence of the magnetic field on the electrons transport (creation of an anisotropy) and thus on the resitivity.The last diagnotic allowing the estimation of the magnetic field detailed in this thesis is the proton deectometry. itallows to observe the deviation of a proton beam during its propagation under the inuence of electric and magneticfields. Other experiments were focused on the fast electron beam divergence. Two main diagnotics were used : the K α imaging and the coherent transition radiation (C.T.R) imaging at the rear side of solid targets. These diagnoticsallowed to estimate the fast electron beam divergence for two distinct energetic electron populations. The differenceof divergence coming from characteristics of both diagnotics (electrons in charge of the emissions in different energies). The diagnotics of on-surface magnetic fields of target irradiated by intense laser, such as the technics of polarimetry and crossed interferometry developed in this thesis, are dedicated to be combined with diagnotics determining the evolution of the radial size of the fast electron beam generated by the laser-matter interaction. Their simultaneous use, and the correlation between their respective data, should allow to establish experimentally, in the short term, the inuence of the on-surface magnetic fields on the fast electron beam initial characteristics, in particular the angular and energy distributions. Our results of polarimetry on the spatio-temporal evolution of the magnetic fields of surface establish the state of the art for this type of measures. There are possible improvements, in particular as regards their use in conditions of irradiation by lasers of intensities > 1018 W/cm2. These perspectives are also the object of discussions in this manuscript.