ABSTRACT
We report on the successful demonstration of second and third harmonic conversion of a high pulse energy, high average power 1030 nm diode pumped Yb-doped yttrium aluminum garnet (Yb:YAG) nanosecond pulsed laser in a large aperture lithium triborate (LBO) crystal. We demonstrated generation of 59.7 J at 10 Hz (597 W) at 515 nm (second harmonic) and of 65.0 J at 1 Hz (65 W) at 343 nm (third harmonic), with efficiencies of 66% and 68%, respectively. These results, to the best of our knowledge, represent the highest energy and power reported for frequency conversion to green and UV-A wavelengths.
ABSTRACT
We report on frequency doubling of high-energy, high-repetition-rate ns pulses from a cryogenically gas cooled, multi-slab Yb:YAG laser system, using a type-I phase-matched lithium triborate (LBO) crystal. Pulse energy of 4.3 J was extracted at 515 nm for a fundamental input of 5.4 J at 10 Hz (54 W), corresponding to a conversion efficiency of 77%. However, during long-term operation, a significant reduction of efficiency (more than 25%) was observed owing to the phase mismatch arising due to the temperature-dependent refractive index change in the crystal. This forced frequent angle tuning of the crystal to recover the second-harmonic generation (SHG) energy. More than a five-fold improvement in energy stability of SHG was observed when the LBO crystal was mounted in an oven, and its temperature was controlled at 27°C. Stable frequency doubling with 0.8% rms energy variation was achieved at a higher input power of 74 W when the LBO temperature was controlled at 50°C.
ABSTRACT
We report on type-I phase-matched second harmonic generation (SHG) in three nonlinear crystals: DKDP (98% deuteration), YCOB (XZ plane), and LBO (XY plane), of 8 J, 10 Hz cryogenic gas cooled Yb:YAG laser operating at 1029.5 nm. DKDP exhibited an efficiency of 45% at a peak fundamental intensity of 0.24 GW/cm2 for 10 Hz operation at 10 ns. At the same intensity and repetition rate, YCOB and LBO showed 50% and 65% conversion efficiencies, respectively. Significant improvement in conversion efficiency, to a maximum of 82%, was demonstrated in LBO at 0.7 GW/cm2 and 10 Hz, generating output energy of 5.6 J at 514.75 nm, without damage or degradation. However, no improvement in conversion efficiency was recorded for YCOB at this increased intensity. Additionally, we present theoretically calculated temperature maps for both 10 J and 100 J operation at 10 Hz, and discuss the suitability of these three crystals for frequency conversion of a 100 J, 10 Hz diode pumped solid state laser (DPSSL).
ABSTRACT
A small scale sample nuclear waste package, consisting of a 28mm diameter uranium penny encased in grout, was imaged by absorption contrast radiography using a single pulse exposure from an X-ray source driven by a high-power laser. The Vulcan laser was used to deliver a focused pulse of photons to a tantalum foil, in order to generate a bright burst of highly penetrating X-rays (with energy >500keV), with a source size of <0.5mm. BAS-TR and BAS-SR image plates were used for image capture, alongside a newly developed Thalium doped Caesium Iodide scintillator-based detector coupled to CCD chips. The uranium penny was clearly resolved to sub-mm accuracy over a 30cm(2) scan area from a single shot acquisition. In addition, neutron generation was demonstrated in situ with the X-ray beam, with a single shot, thus demonstrating the potential for multi-modal criticality testing of waste materials. This feasibility study successfully demonstrated non-destructive radiography of encapsulated, high density, nuclear material. With recent developments of high-power laser systems, to 10Hz operation, a laser-driven multi-modal beamline for waste monitoring applications is envisioned.
ABSTRACT
We report on the successful demonstration of a 100 J-level, diode pumped solid state laser based on cryogenic gas cooled, multi-slab ceramic Yb:YAG amplifier technology. When operated at 175 K, the system delivered a pulse energy of 107 J at a 1 Hz repetition rate and 10 ns pulse duration, pumped by 506 J of diode energy at 940 nm, corresponding to an optical-to-optical efficiency of 21%. To the best of our knowledge, this represents the highest energy obtained from a nanosecond pulsed diode pumped solid state laser. This demonstration confirms the energy scalability of the diode pumped optical laser for experiments laser architecture.
ABSTRACT
The Diode Pumped Optical Laser for Experiments (DiPOLE) project at the Central Laser Facility aims to develop a scalable, efficient high pulse energy diode pumped laser amplifier system based on cryogenic gas cooled, multi-slab ceramic Yb:YAG technology. We present recent results obtained from a scaled down prototype laser system designed for operation at 10 Hz pulse repetition rate. At 140 K, the system generated 10.8 J of energy in a 10 ns pulse at 1029.5 nm when pumped by 48 J of diode energy at 940 nm, corresponding to an optical to optical conversion efficiency of 22.5%. To our knowledge, this represents the highest pulse energy obtained from a cryo cooled Yb laser to date and the highest efficiency achieved by a multi-Joule diode pumped solid state laser system. Additionally, we demonstrated shot-to-shot energy stability of 0.85% rms for the system operated at 7 J, 10 Hz during several runs lasting up to 6 hours, with more than 50 hours in total. We also demonstrated pulse shaping capability and report on beam, wavefront and focal spot quality.
ABSTRACT
Siendo la Enfermería la profesión más numerosa en el campo de la salud, en continuo desarrollo y con un destacable avance científico, nos preguntamos si la imagen que tiene la sociedad de los enfermeros se corresponde con esta realidad. Los estudiantes de Periodismo serán los futuros comunicantes que influirán en la sociedad a través de la transmisión que realicen de su visión de la Enfermería. Objetivo: averiguar qué conocimientos tienen los actuales estudiantes de Periodismo acerca de la labor enfermera. Metodología: estudio descriptivo transversal de una cohorte de estudiantes de Grado de Periodismo de la Universidad Complutense de Madrid. Seleccionados estudiantes de los cursos 2º y 3º y cálculo probabilístico de tamaño muestral en 185 sujetos. La información se recogió mediante encuesta elaborada ad hoc y administrada por los investigadores, en la que se preguntaba por las actividades de la enfermera en el hospital, en el centro de salud y sobre los estudios requeridos para ejercer esta profesión. Resultados: se recogieron 179 encuestas válidas, 67% de mujeres y 21 años de media de edad. Respecto a las actuaciones enfermeras en el hospital, la "Realización de técnicas" fue marcada por un 98,9% de los encuestados, frente al 29,1% que marcó la "Educación sanitaria", las respuestas fueron similares en relación al centro de salud. Un 84,91% contestó que es necesario el grado universitario para ser enfermera. La palabra "cuidados" fue la más repetida (36 veces) como asociada con la Enfermería. Conclusiones: las funciones de las enfermeras, diferentes a la realización de técnicas, son todavía bastante desconocidas por los estudiantes de Periodismo
Nursing is the most numerous profession within the health area, with constant development and remarkable scientific advances; however, we wonder whether the image that society has of nurses coincides with this reality. Journalism students will be the future reporters who will have influence upon society through the transmission they make of their view of Nursing. Objective: to find out the level of knowledge by current Journalism students about nursing activities. Methodology: transversal descriptive study of a cohort of Journalism students from the Universidad Complutense de Madrid. Students of the 2nd and 3rd years were selected, and probabilistic estimation of sample size in 185 subjects. Information was collected through an ad hoc survey, and administered by researchers. Questions were asked about the activities of nurses at hospital and public outpatient centres, and about the studies required in order to practice this profession. Results: overall, 179 valid surveys were collected, 67% by women, and with a mean age of 21 years. Regarding nursing activities at hospital, "Technique Conduction" was marked by 98,9% of participants, vs. 29,1% who marked "Health Training"; answers were similar regarding the outpatient centre. An 84.91% answered that a University Degree is required to become a nurse. "Care" was the most repeated term (36 instances), in association with Nursing. Conclusions: nurse activities other than technique conduction are still quite unknown by Journalism students
Subject(s)
Humans , Social Perception , Professional Role , Nurses , Students/statistics & numerical data , Data Collection/methods , Professional Competence , Public OpinionABSTRACT
We report on the first demonstration of a diode-pumped, gas cooled, cryogenic multislab Yb:YAG amplifier. The performance was characterized over a temperature range from 88 to 175 K. A maximum small-signal single-pass longitudinal gain of 11.0 was measured at 88 K. When amplifying nanosecond pulses, recorded output energies were 10.1 J at 1 Hz in a four-pass extraction geometry and 6.4 J at 10 Hz in a three-pass setup, corresponding to optical to optical conversion efficiencies of 21% and 16%, respectively. To our knowledge, this represents the highest pulse energy so far obtained from a cryo-cooled Yb-laser and the highest efficiency from a multijoule diode pumped solid-state laser system.
ABSTRACT
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 100 fs pulses stretched to 3 ps pulses from 10 pJ 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.
ABSTRACT
We have developed a femtosecond high-intensity laser system that combines both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric CPA (OPCPA) techniques and produces more than 30 J broadband output energy, indicating the potential for achieving peak powers in excess of 500 TW. With a cleaned high-energy seeded OPCPA preamplifier as a front end in the system, for the compressed pulse without pumping the final amplifier, we found that the temporal contrast in this system exceeds 10(10) on the subnanosecond time scales, and is near 10(12) on the nanosecond time scale prior to the peak of the main femtosecond pulse. Using diffractive optical elements for beam homogenization of a 100 J level high-energy Nd:glass green pump laser in a Ti:sapphire final amplifier, we have successfully generated broadband high-energy output with a near-perfect top-hat-like intensity distribution.
Subject(s)
Lasers , Optics and Photonics , Aluminum Oxide/chemistry , Amplifiers, Electronic , Equipment Design , Risk , Signal Processing, Computer-Assisted/instrumentation , Time Factors , Titanium/chemistryABSTRACT
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.
