Chirped pulse Raman amplification in plasma: high gain measurements

High power short pulse lasers are usually based on chirped pulse amplification (CPA), where a frequency chirped and temporarily stretched ``seed'' pulse is amplified by a broad-bandwidth solid state medium, which is usually pumped by a monochromatic ``pump'' laser. Here, we demonstrate the feasibility of using chirped pulse Raman amplification (CPRA) as a means of amplifying short pulses in plasma. In this scheme, a short seed pulse is amplified by a stretched and chirped pump pulse through Raman backscattering in a plasma channel. Unlike conventional CPA, each spectral component of the seed is amplified at different longitudinal positions determined by the resonance of the seed, pump and plasma wave, which excites a density echelon that acts as a "chirped'" mirror and simultaneously backscatters and compresses the pump. Experimental evidence shows that it has potential as an ultra-broad bandwidth linear amplifier which dispenses with the need for large compressor gratings

Chirped pulse Raman amplification in plasma

Raman amplification in plasma has been proposed to be a promising method of amplifying short radiation pulses. Here, we investigate chirped pulse Raman amplification (CPRA) where the pump pulse is chirped and leads to spatiotemporal distributed gain, which exhibits superradiant scaling in the linear regime, usually associated with the nonlinear pump depletion and Compton amplification regimes. CPRA has the potential to serve as a high-efficiency high-fidelity amplifier/compressor stage

Sunglass Filter Transmission and Its Operational Effect in Solar Protection for Civilian Pilots.

INTRODUCTION: The ocular effects of excess solar radiation exposure are well documented. Recent evidence suggests that ocular ultraviolet radiation (UVR) exposure to professional pilots may fall outside international guideline limits unless eye protection is used. Nonprescription sunglasses should be manufactured to meet either international or national standards. The mean increase in UVR and blue light hazards at altitude has been quantified and the aim of this research was to assess the effectiveness of typical pilot sunglasses in reducing UVR and blue light hazard exposure in flight. METHOD: A series of sunglass filter transmittance measurements were taken from personal sunglasses (N = 20) used by pilots together with a series of new sunglasses (N = 18). RESULTS: All nonprescription sunglasses measured conformed to international standards for UVR transmittance and offered sufficient UVR protection for pilots. There was no difference between right and left lenses or between new and used sunglasses. All sunglasses offered sufficient attenuation to counter the mean increase in blue light exposure that pilots experience at altitude, although used sunglasses with scratched lenses were marginally less effective. One pair of prescription sunglasses offered insufficient UVR attenuation for some flights, but would have met requirements of international and national standards for UV-A transmittance. This was likely due to insufficient UVR blocking properties of the lens material. CONCLUSIONS: Lenses manufactured to minimally comply with standards for UVR transmittance could result in excess UVR exposure to a pilot based on in-flight irradiance data; an additional requirement of less than 10% transmittance at 380 nm is recommended

Modification of a personal dosimetry device for logging melanopic irradiance

Performance characterisations were carried out before and after a modification to the optics of the Condor Instruments’ ActTrust light and activity data loggers to improve the spectral performance for measuring melanopic-weighted irradiance in non-visual studies. The results confirm the intended improvement, so that the device provides the best-known single-sensor match to the melanopic response. In addition, the device includes a separate sensor which remained well-matched for illuminance logging. </jats:p

Measurements of UV—A Exposure of Commercial Pilots Using Genesis-UV Dosimeters

A number of studies suggest that pilots are at twice the risk of melanoma and keratinocyte skin cancers than the general population, and that they have a raised mortality from melanoma. No conclusive links with in-flight exposure to ionising radiationor circadian rhythm disruption due to the pilots’ shift work were found. Possible over-exposure to ultraviolet radiation (UVR) may be implicated as pilots may be exposed to higher UV-A levels at cruise altitude compared with those at ground levels. The direct method of making in-flight spectral measurements has been carried out on a limited number of flights, but this technique is challenging; the use of small wearable sensors may be more appropriate but there are a few issues that should be addressed for their use in cockpit measurements. While the spectral response of sensors for erythema effective values usually closely matches the corresponding weighting function, the response of UV-A sensors may not be spectrally flat, which, if not corrected to account for the transmission of the aircraft windshield, could potentially result in large errors. In this paper, the spectral correction method was applied to the UV-A sensor of the Genesis-UV unit to measure UVR exposure of commercial pilots on 312 flights to a range of destinations from four UK airports from September 2016 to August 2017.</jats:p

Measurements of UV—A Exposure of Commercial Pilots Using Genesis-UV Dosimeters

A number of studies suggest that pilots are at twice the risk of melanoma and keratinocyte skin cancers than the general population, and that they have a raised mortality from melanoma. No conclusive links with in-flight exposure to ionising radiationor circadian rhythm disruption due to the pilots&rsquo; shift work were found. Possible over-exposure to ultraviolet radiation (UVR) may be implicated as pilots may be exposed to higher UV-A levels at cruise altitude compared with those at ground levels. The direct method of making in-flight spectral measurements has been carried out on a limited number of flights, but this technique is challenging; the use of small wearable sensors may be more appropriate but there are a few issues that should be addressed for their use in cockpit measurements. While the spectral response of sensors for erythema effective values usually closely matches the corresponding weighting function, the response of UV-A sensors may not be spectrally flat, which, if not corrected to account for the transmission of the aircraft windshield, could potentially result in large errors. In this paper, the spectral correction method was applied to the UV-A sensor of the Genesis-UV unit to measure UVR exposure of commercial pilots on 312 flights to a range of destinations from four UK airports from September 2016 to August 2017