850 research outputs found
Feasibility study of techniques to protect mechanisms operating in space from malfunction. part i- survey and analysis final report, 28 jun. 1963 - 27 jun. 1964
Survey of lubrication devices for reducing friction in mechanisms operating in spac
Feasibility study of techniques to protect mechanisms operating in space from malfunction. part ii- experimental results and recommendations final report, 8 jun. 1963 - 27 jun. 1964
Various techniques used to protect mechanisms operating in space from malfunctions due to frictio
Development of space-syaple thermal-control coatings triannual report, jan. 20 - may 20, 1965
Development of stable thermal control coatings with low solar absorptance to infrared emittance rati
The time resolved measurement of ultrashort THz-band electric fields without an ultrashort probe
The time-resolved detection of ultrashort pulsed THz-band electric field
temporal profiles without an ultrashort laser probe is demonstrated. A
non-linear interaction between a narrow-bandwidth optical probe and the THz
pulse transposes the THz spectral intensity and phase information to the
optical region, thereby generating an optical pulse whose temporal electric
field envelope replicates the temporal profile of the real THz electric field.
This optical envelope is characterised via an autocorrelation based FROG
measurement, hence revealing the THz temporal profile. The combination of a
narrow-bandwidth, long duration, optical probe and self-referenced FROG makes
the technique inherently immune to timing jitter between the optical probe and
THz pulse, and may find particular application where the THz field is not
initially generated via ultrashort laser methods, such as the measurement of
longitudinal electron bunch profiles in particle accelerators.Comment: 7 pages, 3 figures, submitted to AP
The Finite Field Kakeya Problem
A Besicovitch set in AG(n,q) is a set of points containing a line in every
direction. The Kakeya problem is to determine the minimal size of such a set.
We solve the Kakeya problem in the plane, and substantially improve the known
bounds for n greater than 4.Comment: 13 page
Single shot longitudinal bunch profile measurements by temporally resolved electro-optical detection
For the high gain operation of a SASE FEL, extremely short electron bunches are essential to generate sufficiently high peak currents. At the superconducting linac of FLASH at DESY, we have installed an electro- optic measurement system to probe the time structure of the electric field of single ~100 fs electron bunches. In this technique, the field induced birefringence in an electro-optic crystal is encoded on a chirped picosecond laser pulse. The longitudinal electric field profile of the electron bunch is then obtained from the encoded optical pulse by a single shot cross correlation with a 35 fs laser pulse using a second harmonic crystal (temporal decoding). An electro-optical signal exhibiting a feature with 118 fs FWHM was observed, and this is close to the limit of resolution due to the material properties of the particular electro-optic crystal used. The measured electro-optic signals are compared to bunch shapes simultaneously measured with a transverse deflecting cavity
Benchmarking of electro-optic monitors for femtosecond electron bunches
The longitudinal profiles of ultrashort relativistic electron bunches at the soft x-ray free-electron laser FLASH have been investigated using two single-shot detection schemes: an electro-optic (EO) detector measuring the Coulomb field of the bunch and a radio-frequency structure transforming the charge distribution into a transverse streak. A comparison permits an absolute calibration of the EO technique. EO signals as short as 60 fs (rms) have been observed, which is a new record in the EO detection of single electron bunches and close to the limit given by the EO material properties
Single-shot longitudinal bunch profile measurements at FLASH using electro-optic detection:experiment, simulation, and validation
At the superconducting linac of FLASH at DESY, we have installed an electro-optic (EO) experiment for single- shot, non-destructive measurements of the longitudinal electric charge distribution of individual electron bunches. The time profile of the electric bunch field is electro- optically encoded onto a chirped titanium-sapphire laser pulse. In the decoding step, the profile is retrieved either from a cross-correlation of the encoded pulse with a 30 fs laser pulse, obtained from the same laser (electro- optic temporal decoding, EOTD), or from the spectral intensity of the transmitted probe pulse (electro-optic spectral decoding, EOSD). At FLASH, the longitudinally compressed electron bunches have been measured during FEL operation with a resolution of better than 50 fs. The electro-optic process in gallium phosphide was numerically simulated using as input data the bunch shapes determined with a transverse-deflecting RF structure. In this contribution, we present electro-optically measured bunch profiles and compare them with the simulation
Tilted Pulse-Front Phase-matching in Three Dimensions:Overcoming The Cherenkov Angle Restrictions
We consider the non-linear generation of THz with tilted pulse-fronts in three dimensions and show that, contrary to the widely held expectations, coherent phase matching can be obtained for pulse-front tilt angles other the Cherenkov angle
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