Pulse Duration

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Real Time Analysis
of FEL Radiation Spectra
for the Estimation of Photon Pulse Duration

Real Time Analysis of FEL Radiation Spectra for the Estimation of Photon Pulse Duration

As mentioned earlier, one of the most outstanding advantages of this method for photon pulse length determination is the quick availability of the required data in form of the ra- diation spectra. The photon pulse duration is a very important parameter in many other experiments and is often required before or during the experiment, requiring the evalu- ation to be fast. At the flash facility, all measurements are send to a Data AcQuisition system (DAQ), which pre-processes the measurement data in so called middle layer servers 2 and then stores them to a central file storage system. Usually, experiment eval- uation is done by downloading the records from the file storage and evaluating them locally. This has many advantages, as the original data is not lost and is available to any number of scientists for a long time. For the evaluation of these recorded data, the
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Electron pulse control with terahertz fields

Electron pulse control with terahertz fields

The laser system is a Yb:YAG regenerative amplifier [ 153 ] which generates 1 ps, ∼ 350 µJ pulses with a central wavelength of 1030 nm and at a repetition rate of 50 kHz. A small fraction of the laser output power is frequency doubled to obtain pulses at 515 nm for photocathode excitation. The cathode consists of a 20 nm gold film on a sapphire substrate, which is illuminated from behind. Electrons are emitted via two-photon photoemission. < 100 µW are used for photocathode excitation, the electron source size is ∼ 5 µm rms (fitting the spot size on the camera as a function of magnetic lens parameters). The electron gun has a cathode-anode spacing of 25 mm, resulting in fields of 3.6 MV/m and 2.8 MV/m at 90 keV and 70 keV operating volt- ages, respectively. From the measured, uncompressed pulse durations of 780 fs at 90 keV and 930 fs at 70 keV and assuming an initial pulse duration of ∼ 500 fs (from the two consecutive two-photon processes), we infer a longitudinal energy spread of 0.6 eV on emission. This is consistent with the measured 4.26 eV work function of similar thin-film gold cathodes [ 110 ]. Terahertz fields were generated by optical rectification in lithium niobate; at 7 W pump power, both generation stages produce ∼ 30–40 nJ single-cycle pulses at a frequency of ∼ 0.3 THz. The streaking terahertz was generated using tilted-pulse-front pumping [ 88 ] (for details of the experimental setup, see [ 153 ]). For streaking with the butterfly aperture, the THz was focused from inside the vacuum chamber and collinearly with the electron beam, using an off-axis parabolic mirror with a central hole of ∼ 3 mm diameter. The compression terahertz
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Optical parametric chirped pulse amplifiers for seeding, pulse metrology and science at free-electron lasers

Optical parametric chirped pulse amplifiers for seeding, pulse metrology and science at free-electron lasers

The time structure of FEL pulses is an extremely relevant parameter in the study of ultrafast and nonlinear processes and in general, a difficult parameter to address, independently of the lasing method. In Part II, I improved the single-shot pulse duration monitor based on a solid- state cross-correlator (SSCC) by including a wavelength-tunable NOPA, which reduced the pulse duration of the Ti:saphhire pump-probe laser of FERMI FEL from 120 fs to 32 fs and thereby improved the temporal resolution of the SSCC (Section 10.1.1). Further improvements were discussed, which are necessary to make the method robust against pointing fluctuations of the SASE pulses and to increase the temporal resolution beyond the current limitations. This SSCC was applied to characterize the temporal pulse profile properties and the arrival time of the seeded FEL FERMI for various machine conditions, such as single pulse and double pulse mode (Section 11). These results were compared to the theoretical expectations (Section 9.1) and are in good agreement. This experimental campaign, which I performed in collaboration with the FERMI machine group and the scientists of the DiproI endstation, is not only important for experimental users of FERMI, but also give machine operators a tool to tune the FEL to particular conditions and provide feedback to avoid slow drifts. Currently, a permanent SSCC-NOPA setup is in development which is foreseen to be implemented at a downstream position of the CAMP experimental station of FLASH. This online pulse duration monitor will allow pulse duration and time-of-arrival measurements of the SASE pulses in parallel to the molecular studies of the CAMP station and can improve the significance of the acquired CAMP data. Additionally, it is projected to replace the existing burst-mode pump-probe laser of FLASH with a similar OPCPA system as described in Part I supporting sub-20 fs pulses. This would allow the study of the general functionality of the SSCC concept at high repetition rates and the intra-bunch stability of the pulse train of FLASH. However, the average FEL power in the burst-mode may exceed the damage threshold of suitable target materials and has to be investigated in terms of heat accumulation, structural modification and thermal damage in individual studies.
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Short-pulse lasers in photometry and radiometry

Short-pulse lasers in photometry and radiometry

In the literature, a few experiments regarding the influence of pulsed radiation on de- tectors are known. All these investigations have been carried out using a photodiode or a photodiode assembly like a trap detector as DUT. Gentile et. al. [GC96] found no influence on the linearity of the NIST-trap detector when measuring the power re- sponsivity with a mode-locked laser at 532 nm with a repetition rate of 100 MHz and a pulse duration of 5 ps. Investigations from Stuik et. al. [SB02] on the responsivity of a photodiode at pulse durations between 170 ns and 1,2 ms yielded no influence on pulse duration within the uncertainty of their experiment of 2 %. The same results can be found at pulse durations of 600 ps and 68 ps according to Seely et al. [SBHW02]. For the investigation of pulsed radiation of the spectral power responsivity of a trap detec- tor, Hartree et al. [HHF98] carried out an experiment with an Ar + -laser with a pulse duration of 100 ps and a repetition rate of 100 MHz at 514 nm. No influence could be detected. However, measurements of the same trap detector below 450 nm carried out with a frequency doubled mode-locked Ti:Sa laser with a pulse duration of 5 ps against a cryogenic radiometer and an uncertainty of 0,02 % showed a slight reduction of the responsivity of 0,06 %. No investigations could be found for the influence of lasers with even shorter pulse durations like the 120 fs used in the SRPL setup.
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Ultrashort pulse damage of semiconductors

Ultrashort pulse damage of semiconductors

We have discussed two different approaches, the rate equation and a system of coupled differential equations, respec - tively, for the determination of the melting threshold of semiconductors. It was shown that the simple rate equation model works only well for wide band gap semiconductors. This is mainly caused by the fact that the band gap shrinkage is not taken into account. A reduction of the pulse duration is accompanied by a rise of the production rate of conduction band electrons leading to a decrease of the band gap. Obviously, such an effect is much more important to semiconduc- tors like silicon than for wide band gap semiconductors as silica.
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Fs-laser pulse damage of semiconductors

Fs-laser pulse damage of semiconductors

There is extensive literature devoted to the fundamental processes that are related to the kinetics of high-density plasmas generated in semiconductors by ultrashort laser pulses. To this very day, however, we are not able to calculate the values of melting or damage thresholds with certainty. In the both theoretical and the experimental results a large scattering still exists. From a theoretical point of view this is partly related to a lack of the knowledge of accurate input parameters for the models but also, as we believe, to the more fundamental question of the true criterion for melting induced by ultra- short laser pulses. For longer pulses there is a local thermal equilibrium and for this reason a clear thermal criterion say - ing melting appears if the phonon temperature becomes equal to the melting one. In the case of fs pulses, however, the situation can significantly be different. Such short pulses are capable exciting into the conduction band during the pulse duration an extremely high electron density of up to and even above the order of the critical density. As a result of this highly nonequilibrium process, an electronically induced solid-to-liquid phase transition takes place leading to a band structure collapse and to an ultrafast disordering of the crystal. The crucial and controversially discussed question is, however, at which electron density does this happen. Some authors prefer the critical plasma density related to the laser wavelength 1 others favor smaller ones 2 . By contrast, molecular dynamics calculations suggest a much higher value 3 . It
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Unemployment benefit duration and startup success

Unemployment benefit duration and startup success

4 Results We begin by presenting OLS baseline estimates of the effect of our main explanatory variable, potential benefit duration ( PBD ), on the actual unemployment duration, on the motivation for starting a business, and on subsequent firm outcomes (see Table 8 ). In all regressions, we control for education, previous labor market experience, individual characteristics (gender, nationality), industry, and year-fixed effects. We also include dummy variables indicating whether founders received subsidies from the Federal Employment Agency and/or the KfW bank to control for any unobserved heterogeneity related to startup subsidies (see also Appendix C.2 ). The OLS results indicate that a one month increase in PBD comes with an increase in actual unemployment duration of 0.47 months. Hence, we estimate a duration elasticity of about 0.5. Moreover, one month of additional PBD is associated with an increase in the probability of starting a business out of necessity by about two percentage points. Concerning firm outcomes, more PBD leads to fewer sales and FTE employment in the first two years after starting up. Turning to the coefficients of the control variables, more highly educated individuals tend to be less likely to start a business out of self-reported necessity. Previous managerial experience contributes to better performance in terms of sales and employment growth. Being female or a foreigner does not have any differential effect concerning actual unemployment duration or the motivation for starting a business. If at all, these two characteristics may be associated with lower sales growth. We generally present results for all sectors, as well as results for just non-manufacturing sectors in this section (e.g. OLS baseline estimates for non-manufacturing firms are shown in
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The use of pulse oximeter in hemodynamic assessment

The use of pulse oximeter in hemodynamic assessment

Literature review Non-invasive techniques, along with the advances made in the diagnosis and hemodynamic monitoring of patients, such as pulse oximetry, electrocardiogram, ultrasound, echocardiography, transthoracic bioimpedance, and spectroscopy, indicate a potential revolution in emergency services to explore the control of autonomic nervous system, cardiovascular function and, by extension, the initial phases of compensation in cases of disease and injury.

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Accuracy of pulse oximetry during neonatal resuscitation

Accuracy of pulse oximetry during neonatal resuscitation

The use of recent technology in pulse oximetry enabled the new Masimo SET pulse oximeter (Masimo Corporation, Irvine, CA) to use the variations of the photoplethysmogram during monitoring for developing indices for hemodynamic monitoring and to guide fluid therapy. Perfusion index (PI), the infrared pulsatile signal indexed against the nonpulsatile signal and reflects the amplitude of the pulse oximeter waveform. PI has been shown to be sensitive sympathetic block (Sebastiani et al., 2012), proximal arterial clamping (Moxey et al., 2006), and neonatal left heart obstruction (Granelli and Ostman-Smith, 2007). Other indices retrieved from pulse oximetry like plethysmography variability index (PVI) and pulse contour analysis derived stroke volume variation (SVV) have been also used to monitor hemodynamic variations in ventilated patients and to predict the response to fluid therapy (Marik et al., 2011; Yin and Ho, 2012).
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The Duration of Unemployment Benefits in Europe

The Duration of Unemployment Benefits in Europe

The reduction of the period of granting benefits will shift Germany to a middle position among European countries. The longest periods of unem- ployment benefit are granted in Belgium (unlimit- ed) and Denmark (four years). France, the Netherlands and Norway also grant long benefit periods, but make eligibility dependent on the applicant’s age and duration of employment. At the other end of the spectrum are Great Britain and Italy. Great Britain grants unemployment ben- efit for only six months. In Italy, unemployed per- sons from the age of 50 can draw another three months of benefit on top of the standard six months (see diagram).
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Pulse modulation techniques for switched-mode transmitter

Pulse modulation techniques for switched-mode transmitter

For a replacement of a PA in the analog transmitter by a class-S implementation, the direct conversion pulse encoding techniques can be employed. In case of non-periodic pulse trains (e.g. PWM, DSM ) in a class-S PA system only VSCD or CSCD PA can be used. At such driving conditions, both SMPA architectures suffer from losses associated with finite switch impedance and non-zero output capacitance. For a CSCD based class-S PA, the reconstruction filter is more complex because it has not only to provide proper termination but also transform a differential signal to an unbalanced one. In VSCD PA case, the filter is a two port network. Although, in the VSCD PA a more complex driver circuitry is required, the anti-parallel diodes can be omitted [58] enabling a better PA efficiency as in the CSCD case. Thus, for processing of non-periodic driving pulses, the VSCD PA seems to be the more promising solution.
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79 GHz Pulse Radar / Alexander Leibetseder, BSc

79 GHz Pulse Radar / Alexander Leibetseder, BSc

The thesis presented here deals with the design and the characterization of a sequential sampling pulse radar, where some building blocks partly existed at the institute. The radio frequency part of a conven- tional continuous wave radar system is on for the whole duration of the measurement. In contrast to that, a pulse radar system transmits only short pulses, where the pulse width is in the range of several nano seconds. Thus, the high frequency part of a sequential sampling pulse radar can be switched off in between the pulses. Hence, the power consumption of a sequential sampling pulse radar can be significantly lower than the power consumption of a CW radar system with the same transmit power. During the preparation of this work, the function of each component of the existing system has been verified by simulation and ideas for improvements have been collected. Because the greatest poten- tial for improvement is in the receive section, this section has been completely redesigned. The im- provements have been verified by simulation first. Then each component of the radar system has been characterized by measurements. Especially it could be shown, that the most crucial component of the sequential sampling pulse radar, the pulse oscillator, works. It was the first time, as far as the author knows, that the 77- GHz output signal of a periodically switched pulse oscillator was made visible in time domain. Beside the hardware, this thesis also covers the derivation of a signal model for the se- quential sampling pulse radar, which is then used to estimate the output signal of the system based on the data from the simulation. Of special interest is the signal-to-noise ratio at the output, because this limits the range of the system.
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Optical Properties of Pulse Laser Heated Soot

Optical Properties of Pulse Laser Heated Soot

emission signals.  Whereas the previous studies have used pulse averaged extinction measurements, in  the present study extinction coefficient of a soot aerosol were monitored as a function of time while  simultaneously heating the aerosol with laser pulse fluences typical of LII.  Continuous measurements  (cw)  were  made  of  the  extinction  coefficient  at  wavelengths  of  405  and  830  nm  and  for  a  range  of  (pulsed) laser fluences.  Scattering of the 1064 nm heating pulse by the soot was also monitored at 90  degrees to the laser propagation axis.  The variation of the extinction and scattering coefficients during  and after laser heating was used to explore the interplay of soot particle size variation with heating,  elastic and plastic variation of the soot refractive index absorption function, desorption and dissipation  of  adsorbed  species,  and  sublimation  and  ultimately  to  determine  whether  variation  of  soot  optical  properties  during  the  time  window  of  LII  emission  must  be  accounted  for  when  interpreting  the  measurement.  While  TEM  measurements  of  laser‐heated  soot  as  available  in  literature  give  a  qualitative impression of morphological changes upon varying laser fluence, extinction and scattering  measurements allow for better quantification and real‐time understanding of optical changes induce  by the LII laser pulse
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Relaxation Processes in NQR Multiple-Pulse Spin-Locking 

Relaxation Processes in NQR Multiple-Pulse Spin-Locking 

was found experim entally; for the pulse sequence used and tim es ^ T 2 the signal decay was observed w ith a tim e constant T \ e > T 2, w hich is co n sid ered to confirm the su pposition in question. U sing the sam e substances, som e m ore experim ents w ere done aim ed at the study o f the tim e constant T i e and th e initial value M eq (7^) o f the q u a s i-e q u ilib riu m m agnetization in d ependence on r and the resonance offset A = coq — co, and at a com parison o f r !e and the tim e constant T \ g characterizing th e co n tin u o u s spin locking situation.
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Self-employment duration in urban and rural locations

Self-employment duration in urban and rural locations

Turning now to our main question, the effect of environment on self-employment duration, the results of the first model specification show that the site (urban vs. rural) does not seem to have a universal effect on exit rates. As regards local unemployment, we do not find evidence that a high unemployment in the region forces self-employed individuals to continue. Instead, we find that a rise in the local unemployment rate increases exits from self-employment. The preceding descriptive analysis based on follow-up life tables showed that hazard rates might be lower in rural areas compared with urban areas in the beginning of the spell, but higher in later intervals. The second specification allows us to study whether this still holds after other factors have been controlled for. The estimation results are in line with the descriptive analysis. Figure 1 shows predicted hazard rates for a typical self-employed (median observation). 8 We can see that in urban areas the hazard rates continue to drop with
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Self-employment duration in urban and rural locations

Self-employment duration in urban and rural locations

Secondly, the proportions of self-employed individuals surviving to the end of the next year are presented. On average, around 76 percent of those who entered self-employment in 1988–2001 were still self-employed at the end of the following year. The average survival rate is very similar in both rural and urban areas. The survival rates vary more substantially from year to year. The rates dropped during the deep recession, but have increased markedly in recent years. For example, the survival rate was around 71 percent for spells starting in 1992, whereas it was over 85 percent for spells starting in 2001. Finally, survival rates to the end of 2002 are given for spells originating in 1988–2001. We can see that of the self- employment spells starting in urban (rural) areas in 1988 only 18.2 (17.3) percent survived to the end of 2002. Since 1996, these survival rates have been higher in rural than in urban areas. Table 3 presents the life-table estimates of self-employment survival and hazard rates for urban and rural areas. The hazard rate is defined as the probability that a self-employed individual who has survived to the beginning of an interval will experience a terminal event in an interval of one year. We can see that the hazard rate is around 24 percent in the first year of self-employment spell in both areas. Over the next two years, the hazard rate drops more in rural than urban areas. Hazard rates continue to decrease as spells get longer, falling to only 3–5 percent during the last interval (so called negative duration dependence). Interestingly, it seems that hazard rates are considerably lower in rural areas compared with urban areas at the
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Load Duration Distribution based on SCADA history

Load Duration Distribution based on SCADA history

For the simulation a 5 MW wind turbine model with a rotor diameter of 126 m is used. Compared to the paper from 2017 [ROS17] the generator torque characteristic is changed so that the wind turbine operates at 5 MW. The simulation data is sampled with 50 Hz because of the eigenfrequencies of the simulation model. To use the data a low- pass Butterworth filter is used to reduce the frequency to 1 Hz. With this 1 Hz data the mean, max, min and standard deviation is calculated and a load duration distribution is determined. With this information a normal distribution is assumed to fit to the data set.
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Effects of sensory feedback on duration reproduction

Effects of sensory feedback on duration reproduction

As mentioned before, researchers have argued for distributed, modality-specific timing mechanisms in the brain as subjective time has been found to depend on the sensory modality a temporal duration is presented in. In general, a temporal interval is perceived longer if the duration is conveyed by auditory signals than visual signals, even though physically it has the same duration (Walker & Scott, 1981; Wearden et al., 1998). There is also similar evidence that physically same length durations are judged longer if they are presented as auditory tones than as tactile durations (Jones, Poliakoff, & Wells, 2009). The subjective bias (i.e. the estimated difference from the actual physical duration) as well as the variability of a temporal estimate, therefore, can vary quite dramatically dependent on the modality. Further, multiple durations can be easily kept in the memory, if the durations are presented in different modalities (Gamache & Grondin, 2010). It seems reasonable to assume that this improvement in memory is caused by the fact that the temporal intervals are stored as different memory representations dependent on the modality they are presented in (Bueti, 2011). In the brain, modality-specific temporal processing has also been demonstrated in several imaging studies (for a review see, Bueti, 2011). One study, for example, using transcranial magnetic stimulation could show that the disruption of the visual area V5/MT+ affects the estimation of visual durations, but not of auditory intervals (Bueti, Bahrami, & Walsh, 2008). All these findings rather speak for modality-specific temporal encoding, than for an amodal internal clock, and highlight the perceptual differences and variability of subjective time perception.
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Duration of export relationships of Philippine MSMEs

Duration of export relationships of Philippine MSMEs

Box 2: Highlighting of products with the survivability of fewer than three years Table 4 presented below highlight the top 25 Philippine firms that export products to ASEAN countries with trade relations less than three years with at least $ 50,000 in export value. The industry categories among the top products are the following; 1. Products of the chemical or allied industries; 2. Machinery and mechanical appliances; 3. Base metals and articles of base metal; 4. Mineral products; 5. Vehicles, aircraft, vessels and associated; 6.The pulp of wood or other fibrous cellulosic material; 7. Prepared foodstuffs; 8. Animal or vegetable fats and oils and their cleavage; 9. Textiles and textile articles; 10. Plastics and articles thereof. Regarding categories based on firm sizes; Medium-sized businesses account for the largest share in the top 25 with 14 number of products, followed by Small-sized companies with 8 items. Large Enterprise had the least amount of firm sizes with 3. The list highlights the products that have reasonably sized export values ( greater than $50,000) but have short durations i.e. fewer than three years. Concerned government agencies can then investigate the causes for the short duration observed for this group of products.
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Methods of estimating the mean duration of enterprises and the mean additional duration of enterprises in Lodzkie Voivodship

Methods of estimating the mean duration of enterprises and the mean additional duration of enterprises in Lodzkie Voivodship

The aim of this paper is to present theoretical and practical aspects of determining: mean duration and mean additional duration of enterprises based on annual cohort tables. The theoretical considerations will be illustrated with calculations for the established enterprises (including the liquidated ones) in Lodzkie Voivodship in the years 2001-2015; with a special focus on three cities with the rights of a county (the ‘powiat’ status): Lodz, Piotrkow Trybunalski and Skierniewice. The results of the analyses may contribute to implementing a more effective regional policy which would in turn foster the development of entrepreneurship.
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