Search

Nature photonics 14(6), 391 - 397 (2020). doi:10.1038/s41566-020-0607-z, The European XFEL is a hard X-ray free-electron laser (FEL) based on a high-electron-energy superconducting linear accelerator. The superconducting technology allows for the acceleration of many electron bunches within one radio-frequency pulse of the accelerating voltage and, in turn, for the generation of a large number of hard X-ray pulses. We report on the performance of the European XFEL accelerator with up to 5,000 electron bunches per second and demonstrating a full energy of 17.5 GeV. Feedback mechanisms enable stabilization of the electron beam delivery at the FEL undulator in space and time. The measured FEL gain curve at 9.3 keV is in good agreement with predictions for saturated FEL radiation. Hard X-ray lasing was achieved between 7 keV and 14 keV with pulse energies of up to 2.0 mJ. Using the high repetition rate, an FEL beam with 6 W average power was created., Published by Nature Publ. Group, London [u.a.]

Physical review accelerators and beams 20(4), 042005 (2017). doi:10.1103/PhysRevAccelBeams.20.042005, A full test of the cavity package concept under realistic operating condition was a necessary step before the assembly of the European XFEL (EXFEL) 3.9 GHz superconducting system and its installation in the accelerator. One cavity, equipped with magnetic shielding, power coupler and frequency tuner has been tested in a specially designed single cavity cryostat in one of the test benches of the DESY Accelerator Module Test Facility (AMTF). The cavity was operated at high pulsed power up to an accelerating field of 24 MV/m, above the quench accelerating field of 21 MV/m achieved during the continuous wave (CW) vertical qualification test and with a large margin with respect to the EXFEL maximum operating specification of 15 MV/m for the 3.9 GHz system. All subsystems under test—coupler, tuner, waveguide tuners, low level radio-frequency (LLRF) system—were qualified to their design performances., Published by American Physical Society, College Park, MD

The injector upgrade of LINAC II at DESY aims to improve its reliability and mitigate the radiological activation of components due to electron loss at relatively high energy of hundreds of MeV. Therefore, a 2.998 GHz hybrid buncher has been developed and will be installed in between an existing 2.998 GHz pre-buncher and LINAC II. It comprises a 1-cell standing-wave (SW) section for rapid electron acceleration and a 13-cells traveling-wave (TW) section for further beam bunching and acceleration. This paper focuses on its radio-frequency tuning procedure. The tuning strategy combines a non-resonant bead-pull measurement of complex electric field and a linear model for local reflection coefficient calculation. It is demonstrated that imaginary part of the local reflection coefficient represents the field distribution straightforwardly, based on which the structure can be tuned from cell to cell. During tuning, special attention has been paid to the field enhancement in the SW section to ensure its beam-capturing capability. Field amplitude and phase, global and local reflection coefficients have been analyzed for two different frequencies simultaneously, i.e. the intrinsic frequency of the structure and the target frequency, to avoid over-tuning. The tuning result is satisfying. For the target frequency, field unflatness of the TW section has been reduced from ±9% to ±4%, and field in the SW section has been enhanced significantly. Meanwhile, in the TW section, the deviation of phase advances between adjacent cells from the nominal value 120° has been reduced from the range ±5° to ±2°. By using ASTRA simulation, it has been verified that the residual detuning of the structure is acceptable in view of the beam dynamics performance.

Marked progress in neonatology changed care of very preterm infants (VLBW) over the last decades - but also the attitude towards family-centred care (FCC). With the directive of the German Federal Joined Committee (G-BA), politicians recognize the necessity of neonatal FCC.To evaluate time and personnel costs necessary at a centre of established FCC.Elternberatung "Frühstart" is a FCC programme for VLBW and seriously ill neonates from preganancy at risk to follow-up home-visits delivered by one interdisciplinary team. Analysis (2011-2014): 1.) Number of cases /participation in programme, 2.) resources of time, 3) and personnel, 4.) funding, 5) economic impact.1.1.2011-31.12.2014: 441 cases (total cases: 2 212) participated in the programme. Participation of VLBW: mean 92% (86.4-97,2%). Costs of time are highest in neonates with congenital malformations: median 13.8 h, VLBW: median 11,2 h. Transition to home is most time intensive: median 7,3 (0-42.5) h. In average of 3.1 full-time nurses (part-time workers) are able to counsel 48 families/quarter. In severe cases funding is partly provided by health care insurances for social medical aftercare: positive applications: mean 92.7% (79.6-97.7%).Participation in the FCC programme in neonatology is high and costs of time are manageable.

2nd European Advanced Accelerator Concepts Workshop, EAAC2015, La Biodola, Isola d'Elba, Italy, 13 Sep 2015 - 19 Sep 2015; Nuclear instruments & methods in physics research / A 829, 233-236 (2016). doi:10.1016/j.nima.2016.01.067, The SINBAD facility (Short INnovative Bunches and Accelerators at DESY) is a long-term dedicated accelerator research and development facility currently under construction at DESY. It will be located in the premises of the old DORIS accelerator complex and host multiple independent experiments cost-effectively accessing the same central infrastructure like a central high power laser. With the removal of the old DORIS accelerator being completed, the refurbishment of the technical infrastructure is currently starting up.The presently ongoing conversion of the area into the SINBAD facility and the currently foreseen layout is described. The first experiment will use a compact S-band linac for the production of ultra-short bunches at hundred MeV. Once established, one of the main usages will be to externally inject electrons into a laser-driven plasma wakefield accelerator to boost the energy to GeV-level while maintaining a usable beam quality, ultimately aiming to drive an FEL. The second experiment already under planning is the setup of an attosecond radiation source with advanced technology. Further usage of the available space and infrastructure is revised and national and international collaborations are being established., Published by North-Holland Publ. Co., Amsterdam

2nd European Advanced Accelerator Concepts Workshop, EAAC2015, La Biodola, Isola d'Elba, Italy, 13 Sep 2015 - 19 Sep 2015 ; Nuclear instruments & methods in physics research / A 829, 183 - 186(2016). doi:10.1016/j.nima.2016.01.038, Short, high-brightness relativistic electron bunches can drive ultra-high wakefields in the dielectric wakefield accelerators (DWFAs). This effect can be used to generate high power THz coherent Cherenkov radiation, accelerate a witness bunch with gradient two or three orders of magnitude larger than that in the conventional RF linear accelerators, introduce energy modulation within the driving bunch itself, etc. The paper studies potential applications of the DWFAs in the SINBAD facility at DESY. The simulations show that the ultra-short relativistic bunches from the SINBAD injector ARES can excite accelerating wakefields with peak amplitudes as high as GV/m at THz frequencies in proper DWFA structures. In addition, it illustrates that the DWFA structure can serve as a dechirper to compensate the correlated energy spread of the bunches accelerated by the laser plasma wakefield accelerator., Published by North-Holland Publ. Co., Amsterdam

We report on the development and application of robust, inexpensive bremsstrahlung detectors, so called Compton diodes, for a photon energy from 5 MeV to more than 130 MeV . The detector signal is estimated from a simple analytical model and compared with a more quantitative description of the detector behaviour obtained from numerical simulations and with experimental results for photon energies between 6 and 72 MeV . For the S-DALINAC, a beam loss monitoring system using Compton diodes as detectors has been designed and installed. The detectors were also used for other applications like the investigation of dark current emission from the superconducting cavities at the TESLA Test Facility (TTF) at DESY.

An experiment has been carried out at the TESLA Test Facility (TTF) linac to investigate the wake fields generated by picosecond electron bunches in narrow beam pipes with artificially roughened inner surface. Two methods were employed: (a) the energy structure imposed on the bunches by the wake fields was analysed with a magnetic spectrometer, and (b) the generated THz radiation was directly recorded in an interferometer equipped with Golay cell detectors. Both methods indicate the presence of strong wake field effects as expected from simulations in which the rough surface is modelled by a dielectric layer.

O presente trabalho constitui uma reflexão sobre o impacto que os pressupostos do Movimento Feminista têm causado na produção teórica da Psicologia, provocando uma revisão de suas metodologias e conceitos, e levando a uma nova abordagem científica preocupada agora com o desenvolvimento de formas alternativas de análise das relações entre as mulheres e os homens. Contestando o viés androcêntrico da ciência moderna o Movimento Feminista promoveu o desenvolvimento de formas alternativas de análise das relações entre homens e mulheres e provocou o que poderíamos chamar de uma virada epistemológica nas ciências sociais. Fez-se uma breve alusão ao enquadramento histórico subjacente à emergência da Psicologia, bem como aos princípios que estiveram na base de seu desenvolvimento como ciência. Em seguida aborda-se o modo como o questionamento desses princípios tem levado a Psicologia a compreender o enquadramento das pessoas (mulheres e homens) no mundo social envolvente, a tomada de perspectiva do ser humano com base em aspectos relacionais. Este trabalho pretende abordar os desafios propostos pelo Movimento Feminista à Psicologia e as repercussões de tais questionamentos em suas práticas.

It has been reproducibly observed that the energy distribution of the beam, when fully longitudinally compressed for SASE operation, breaks up into several peaks. In this paper a description of the experimental setup, beam operating conditions, and observations is presented to enable further theoretical studies of this effect.

It is not uncommon for the naive native speaker of English to confuse German and Dutch. One reason for this lies in the English names for the languages, but another reason is that Dutch and German sound similar to the anglophone ear. Many, perhaps even most, university students of Dutch in the United Kingdom and elsewhere in the anglophone world come to Dutch with a good knowledge of German and again, often draw parallels between their mother tongue, and Dutch and German. Of course, professional linguists know that English and German are neighbors of Dutch and members of the same Germanic language family. However, comments by naive native speakers serve to highlight questions about the typological contrasts between these three languages.

The wake fields generated by electron bunches of high charge density in an undulator vacuum chamber might become sufficiently large to affect the FEL amplification. Recent theoretical and numerical calculations show that, with decreasing the bunch length the dominant contribution to the wake fields comes from the surface roughness of the chamber. The excited radiation field should be detectable outside the vacuum chamber. At the TTF linac an experiment is in preparation to measure the radiation power spectrum excited in beam pipes with an artificially increased roughness on the inner surface. Particularly, the dependence on the radius of the pipe and the shape of the surface will be studied in this experiment. In this paper we describe the experimental setup, detection schemes for the radiation and estimates of systematic background.

Published online 16 November 2005 Groupe SERA; Many scientific disciplines ranging from physics, chemistry and biology to material sciences, geophysics and medical diagnostics need a powerful X-ray source with pulse lengths in the femtosecond range [1-4]. This would allow, for example, time-resolved observation of chemical reactions with atomic resolution. Such radiation of extreme intensity, and tunable over a wide range of wavelengths, can be accomplished using high-gain free-electron lasers (FEL) [5-10]. Here we present results of the first successful operation of an FEL at a wavelength of 32 nm, with ultra-short pulses (25 fs FWHM), a peak power at the Gigawatt level, and a high degree of transverse and longitudinal coherence. The experimental data are in full agreement with theory. This is the shortest wavelength achieved with an FEL to date and an important milestone towards a user facility designed for wavelengths down to 6 nm. With a peak brilliance exceeding the state-of-the-art of synchrotron radiation sources [4] by seven orders of magnitude, this device opens a new field of experiments, and it paves the way towards sources with even shorter wavelengths, such as the Linac Coherent Light Source [3] at Stanford, USA, and the European X-ray Free Electron Laser Facility [4] in Hamburg, Germany.

Because of the increasing interest on stimulating fracture healing, knowledge about the role and chronology of growth factors during the healing process is important. The purpose of this study was to quantify the protein concentration of IGF-I and TGF-beta1 during rat tibial fracture healing 5, 10, and 15 days after fracture using ELISA methods and to analyze the distribution of the proteins and the related mRNA expression in the fracture callus by immunohistochemistry and in situ hybridization. The following three groups were analyzed: Fractured tibiae intramedullary stabilized with K-wires coated with IGF-I and TGF-beta1 compared with fractures stabilized with uncoated K-wires and unfractured tibiae. The weight of the callus increased during the healing process in both experimental groups. The protein concentration of IGF-I and TGF-beta1 in the fracture callus showed significant changes between the investigated time points and treatment groups compared with the unfractured tibia. IGF-I increased with healing time whereas TGF-beta1 revealed a constantly elevated level at the investigated time points. Mesenchymal cells, osteoblasts, osteocytes, proliferating and immature chondrocytes, and osteoclasts expressed both growth factors. No differences in the expression and localization pattern of the growth factors were detectable among the groups. Using the different methods for quantification and visualization of the growth factors, no differences (except the increased IGF-I concentration at day 15 in the growth factor group) were seen between the normal and the growth factor-stimulated fracture healing as an indication for physiological healing after exogenous growth factor treatment.

A histomorphometrical analysis of a healing femur osteotomy in rats was performed in order to determine, whether local administration of GH and its mediator IGF-I leads to different callus stimulation. Using miniosmotic pumps, 8 animal’s received human GH (group III), 8 received IGF-I (group II) and 8 received phosphate buffer as placebo (group I). After 21 days, the callus area, callus diameter, mineralized callus area, callus bone density, cartilage area and the cartilaginous share of the callus area were histomorphometrically determined. In the group II and III a significantly higher callus area and mineralized callus area was detected. The cartilage area and the cartilaginous share of the callus was nearly doubled in the placebo group compared to group II and III. Our results demonstrate, that in the present model the local application of both, GH and IGF-I increases hard callus formation nearly to an equal amount. Similarly, both substances change the callus composition in the same way towards a lower share of cartilage. The results propose, that GH may exert a direct, non liver-mediated effect on fracture healing.

Zur Deckung von Hautdefekten werden haufig freie, autologe Spalt- oder Vollhauttransplantationen benotigt, bei denen eine Vielzahl ernstzunehmender und den Patienten belastender Probleme wie Wundheilungsstorungen, Keloidbildung, Sensibilitatsstorungen und Wundschmerzen auftreten. Ziel der hier vorgestellten Arbeit ist es eine Alternativmethode zu etablieren, die bei asthetisch ansprechendem Ergebnis die bekannten Komplikationen minimiert, sowie die Operationszeit und, durch die Moglichkeit zur ambulanten Behandlung, den stationaren Aufenthalt der Patienten verkurzt.

The 2001 Particle Accelerator Conference, PAC2001, Chicago, USA, 18 Jun 2001 - 22 Jun 2001; 3771-3773 (2001)., This paper reports on recent beam measurements of higher order modes in the TESLA Test Facility (TTF) accelerating modules. Using bunch trains of about 0.5 ms with 54MHz bunch repetition and up to 90% modulated intensity, transverse higher order modes are resonantly excited when the beam is offset and their frequency on resonance with the modulation frequency. With this method, the trapped modes can be excited and their counteraction on the beam observed on a wide-band BPM downstream of the module. Scanning the modulation frequency from 0 to 27MHz allows a systematic investigation of all possible dangerous modes in the modules.

An experiment has been carried out at the TESLA Test Facility linac to investigate the wake fields generated by picosecond electron bunches in narrow beam pipes with an artificially roughened inner surface. The energy structure imposed on the bunches by the wake fields has been analyzed with a magnetic spectrometer. Strong harmonic-wake-field effects are observed as expected from simulations in which the rough surface is modeled by a dielectric layer.

We present experimental evidence that the free-electron laser at the TESLA Test Facility has reached the maximum power gain of 107 in the vacuum ultraviolet (VUV) region at wavelengths between 80 and 120 nm. At saturation the FEL emits short pulses with GW peak power and a high degree of transverse coherence. The radiation pulse length can be adjusted between 30 fs and 100 fs. Radiation spectra and fluctuation properties agree with the theory of high gain, single-pass free-electron lasers starting from shot noise.

The conceptional design of the proposed linear electron-positron collider TESLA is based on 9-cell 1.3 GHz superconducting niobium cavities with an accelerating gradient of ${E}_{\mathrm{acc}}\ensuremath{\ge}25\mathrm{MV}/\mathrm{m}$ at a quality factor ${Q}_{0}\ensuremath{\ge}5\ifmmode\times\else\texttimes\fi{}{10}^{9}$. The design goal for the cavities of the TESLA Test Facility (TTF) linac was set to the more moderate value of ${E}_{\mathrm{acc}}\ensuremath{\ge}15\mathrm{MV}/\mathrm{m}$. In a first series of 27 industrially produced TTF cavities the average gradient at ${Q}_{0}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}5\ifmmode\times\else\texttimes\fi{}{10}^{9}$ was measured to be $20.1\ifmmode\pm\else\textpm\fi{}6.2\mathrm{MV}/\mathrm{m}$, excluding a few cavities suffering from serious fabrication or material defects. In the second production of 24 TTF cavities, additional quality control measures were introduced, in particular, an eddy-current scan to eliminate niobium sheets with foreign material inclusions and stringent prescriptions for carrying out the electron-beam welds. The average gradient of these cavities at ${Q}_{0}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}5\ifmmode\times\else\texttimes\fi{}{10}^{9}$ amounts to $25.0\ifmmode\pm\else\textpm\fi{}3.2\mathrm{MV}/\mathrm{m}$ with the exception of one cavity suffering from a weld defect. Hence only a moderate improvement in production and preparation techniques will be needed to meet the ambitious TESLA goal with an adequate safety margin. In this paper we present a detailed description of the design, fabrication, and preparation of the TESLA Test Facility cavities and their associated components and report on cavity performance in test cryostats and with electron beam in the TTF linac. The ongoing research and development towards higher gradients is briefly addressed.

We present the first observation of Self-Amplified Spontaneous Emission (SASE) in a free-electron laser (FEL) in the Vacuum Ultraviolet regime at 109 nm wavelength (11 eV). The observed free-electron laser gain (approx. 3000) and the radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width and intensity fluctuations all corroborate the existing models for SASE FELs., 6 pages including 6 figures; e-mail: joerg.rossbach@desy.de

Top of pageAbstract Background/aims: Since December 2002 we use ibuprofen to treat PDA. Success rates, however, were lower than expected. We therefore compared efficacy and side effects of ibuprofen in very low birth weight infants to a historical control group treated with indomethacin. Methods: Charts of all infants < 1500g admitted from 1.1.2000 to 1.3.2005 were reviewed. Infants mechanically ventilated on day 3 of life, with echocardiographically confirmed PDA received indomethacin (3 x 0.2 mg/kg in 12 hours intervals; time period 1: before 1.12.2002) or ibuprofen (10; 5; 5 mg/kg in 24 hours intervals; time period 2. after 1.12.2002), respectively. Results: Fifty-three (25%) of 214 infants born in time period 1 were treated with indomethacin. Median birth weight 830 g (380 - 1460), gestational age 26 wks (22 - 31). Fifty-six (36%) of 155 infants were treated with ibuprofen. Median birth weight 895 g (355 - 1430), gestational age 26 wks (23 - 30). Closure rates with first treatment cycle were 60% (indomethacin) and 34% (ibuprofen) (p=0.005). Surgical ligation was performed in 7% of infants during time period 1 versus 14% in time period 2 (p=0.02). Temporary oliguria/anuria occurred in 19% of infants in the indomethacin and in 11% in the ibuprofen treatment group. Focal intestinal perforation or NEC with perforation occurred during time period 1 in 4/53 infants treated with indomethacin and in 7/139 infants not treated, in time period 2 in 2/56 infants treated with ibuprofen and in no infant without treatment. Conclusion: Ibuprofen was less effective than indomethacin in closing the PDA in very low birth weight infants in our centre. Need for surgical ligation was twice as high following ibuprofen treatment. The difference to results of other centres may be explained by extreme prematurity of our population.

Physical review letters 88, 104802 (2002). doi:10.1103/PhysRevLett.88.104802, Published by APS, College Park, Md.