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Characterization of barely visible impact damage (BVID) in polymer matrix composites (PMCs) is necessary to use slow crack growth damage tolerance models and evaluate remaining life of PMC components. Azimuthally scanned angled-beam pulse-echo ultrasound is investigated as a complimentary technique to normal incidence ultrasound inspection of BVID in PMCs to characterize delamination fields. It is found that there is a correlation between signals present in the azimuthally scanned angled-beam pulse-echo ultrasound C-scans and transverse cracks seen in X-ray computed tomography inspection. These transverse cracks are not readily identifiable as transverse cracks in normal incidence C-scan inspection.

PurposeIn advanced radiotherapy techniques such as intensity-modulated radiation therapy (IMRT), the quality assurance (QA) process is essential. The aim of the study was to assure the treatment planning dose delivered during delivery of complex treatment plans. The QA standard is to perform patient-specific comparisons between planned doses and doses measured in a phantom.Materials and methodThe Delta 4 phantom (Scandidos, Uppsala, Sweden) has been used in this study. This device consists of diode matrices in two orthogonal planes inserted in a cylindrical acrylic phantom. Each diode is sampled per beam pulse so that the dose distribution can be evaluated on segment-by-segment, beam-by-beam, or as a composite plan from a single set of measurements. Ninety-five simple and complex radiotherapy treatment plans for different pathologies, planned using a treatment planning system (TPS) were delivered to the QA device. The planned and measured dose distributions were then compared and analysed. The gamma index was determined for different pathologies.ResultsThe evaluation was performed in terms of dose deviation, distance to agreement and gamma index passing rate. The measurements were in excellent agreement between with the calculated dose of the TPS and the QA device. Overall, good agreement was observed between measured and calculated doses in most cases with gamma values above 1 in >95% of measured points. Plan results for each test met the recommended dose goals.ConclusionThe delivery of IMRT and volumetric-modulated arc therapy (VMAT) plans was verified to correspond well with calculated dose distributions for different pathologies. We found the Delta 4 device is accurate and reproducible. Although Delta4 appears to be a straightforward device for measuring dose and allows measure in real-time dosimetry QA, it is a complex device and careful quality control is required before its use.

하지만 ITO 는 기계적 강도 및 안정성에 대한 제한이 존재하여 현재 다양한 곡면 및 유연 투명 전도성 소재에 대한 적용에는 문제가 있다. 이러한 응용품의 요구에 따라 유연한 표면에 박막Key Words: Pulsed Laser(펄스레이저), Silver(은), Nanowire(나노와이어), Micro Fabricatio(미세가공) 초록: 펄스 레이저를 적용한 실버나노와이어의 접합 영향이 연구되었다. 조사된 레이저 펄스 에너지는 실버나노와이어 네트워크에서 실버나노와이어간에 접합을 유도하였으며 이로 인해 투명 기저위의 실버나노와이어 네트워크 박막에 전기 저항값을 조절할 수 있었다. 특히 이러한 나노네트워크에서의 접합은 개별 나노와이어의 접촉점의 형태로 발생되었고 접합의 효과는 전체 실버나노와이어 네트워크의 전기저항 변화 측정으로 평가하였다. 또한 레이저 빔 펄스폭 및 레이저 평균 출력이 나노와이어 접합 비율 평가에 적용되어 연구되었다. 실버나노와이어 네트워크의 광학 특성도 관찰되었으며 이에 레이저 공정 요소 대비 효과도 연구되었다. 최적화된 레이저빔 적용 재료처리는 특화된 국부 재료 특성 개선에 장점을 보였다. 펄스 레이저를 이용한 실버나노와이어의 재료처리의 적용과 그 효과에 대해서도 논의한다. Abstract: A direct pulsed laser process for welding and networking silver nanowires was developed. The welded nanowire network demonstrated modified electrical properties in a transparent substance. In particular, the welding points on the nanowires were investigated to measure the resistance at the connections. The level of networking in nanowires was explored with respect to various laser pulse widths and average power densities. In particular, the influence of laser beam density was investigated in detail. Selective laser treatment can be advantageous in imparting customized local property changes in transparent conducting materials. Various applications of the process are also discussed in this paper.

Long pulse operation of high power ion source is the requirement of fusion science research on neutral beam injector. A breakdown of accelerator column is drastically increased when operating with high beam energy and long beam duration. To extend the pulse length, which was stopped with every breakdown so far, the beam re-starting technology was developed and utilized. As a result, the voltage drop of every power supply due to breakdown was recovered within a time of 90 ms and beam pulse length was extended much longer than the case before this improvement. The details of the beam re-starting technology and the preliminary results were presented in this manuscript.

The experiment described in this paper is the first study of the response of a static tungsten powder sample to an impinging high energy proton beam pulse. The experiment was carried out at the HiRadMat facility at CERN. Observations include high speed videos of a proton beam induced perturbation of the powder sample as well as data from a laser Doppler vibrometer measuring the oscillations of the powder container. A comparison with a previous analogous experiment which studied a proton beam interaction with mercury is made. The experiment described in this paper is the first study of the response of a static tungsten powder sample to an impinging high energy proton beam pulse. The experiment was carried out at the HiRadMat facility at CERN. Observations include high speed videos of a proton beam induced perturbation of the powder sample as well as data from a laser Doppler vibrometer measuring the oscillations of the powder container. A comparison with a previous analogous experiment which studied a proton beam interaction with mercury is made

Because the nearspace slow-moving platform borne synthetic aperture radar (SAR) can realize high resolution imaging using low pulse repetition frequency (PRF), a full-aperture ScanSAR (FA-ScanSAR) operation, which switches the range beam pulse by pulse, was proposed for wide swath imaging. This operation separates the wide swath into several sub-swaths, and each of which can be illuminated by a narrow range beam. The SAR antenna switches the range beam to point at each of the sub-swaths in turn, transmits pulses and receives echoes pulse by pulse. The design method of main system parameters and the calculating expressions of the performance indexes are addressed in the paper. A design example is given to compare the performance of the conventional strip operation, ScanSAR and FA- ScanSAR operation. The results show that FA-ScanSAR operation can obtain high resolution by full aperture accumulation in wide swath and improve the signal-to-noise ratio of SAR images for the nearspace slow-moving platform borne SAR.

The Gun Test Facility (GTF) was built to test high-brightness sources for the proposed Linac Coherent Light Source (LCLS) at SLAC. The longitudinal emittance has been determined by measuring the energy spectrum after the linac as a function of the linac phase. The phase-space parameters defining the beam pulse width, correlated energy spread, and slice energy spread at the linac entrance (∼5 MeV beam energy) are fit to the measured energy spectra. A large, linear energy–time correlation is observed for bunch charges from 15 to 300 pC. Preliminary Parmela calculations show this correlation results from the strong longitudinal space charge forces in this short 2-ps long bunch.

The energy loss for an accelerated electron beam passing through a laser-driven RF gun has been studied. An analytical formula of the energy loss has been obtained using the time-dependent resonant modes of a cylindrical pill-box cavity. As an approximation, this formalism assumes a rigid beam pulse so the change of pulse shape dealing with space-charge force and wake field force is ignored.

A new type of beam-position monitor (BPM) has been developed in the KEKB accelerator. The BPM employs an I/Q (In-phase and Quadrature phase) demodulator operating at an acceleration frequency of 509 MHz without down converting. The peak value of a demodulated beam pulse is sampled every revolution period. Not only horizontal and vertical positions, but also the longitudinal position can be detected turn by turn. The performance of this four-dimensional BPM is described in detail. A monitor is indispensable for tuning a beam injected into the KEKB.

We outline the design concept for low-inductance high-current spark modules at a voltage level of 100 kV and a current of 1 MA. We present the results of an investigation of the switching and operating characteristics of multichannel, multigap spark modules as a function of the design and the shape and amplitude of the beam pulse. We give a description of the designs and parameters of the developed types of spark modules.

The design of a electronic beam pulse generator for industrial applications is described. The parameters of the electron beam are 700 kV, 25 kA, and 1 µsec. The design features of the magnetic circuits and the test bench used to test and inspect them are described.

The Australian Synchrotron AS is moving towards a continuous injection mode called top-up. During top-up the linac and booster synchrotron injection system will be in continuous operation rather than usedevery eight hours the way they are used at present. In order to monitor the performance of the injection system areal-time injection efficiency monitoring system has been developed. The system consists of several Fast CurrentTransformers [1] and matching digitisers [2] and is designed to count every beam pulse and measure the transmission efficiency through the whole accelerator complex. After calibrating the system using a properly matchedFaraday Cup at the electron gun, a transmission efficiency is then calculated at each stage of transferring the beamfrom 90 keV out of the gun to 3 GeV in the storage ring. The system is used to optimise the injection process inorder to maximise the injection efficiency and as an early warning system when equipment starts to fail and theinjection efficiency decreases.

With the methods of time-division multiplexing in Frontend and angle detuning in FOA, each beam pulse on SG-III prototype facility is controlled independently and so the systematic variations of power imbalance are eliminated entirely.

Some major system features are not stated but can be inferred. For example this is probably an engineering test facility, not a power plant driver, because the standoff from target to final magnet is only 5.0 m. The fusion target takes two-sided illumination with indirect drive using a total of 60 beam pulses: 10 pre-pulses (3.0 GeV) + 20 main pulses (4.0 GeV) from each side. On page 12 it's stated that the charge per beam pulse is 26.8 {micro}C, so we calculate pre-pulse: 20 x 3 GeV x 26.8 {micro}C = 1.608MJ, main pulse: 40 x 4 GeV x 26.8 {micro}C = 4.288MJ, total beam energy 5.896MJ. The beam ion mass ks 200 amu, so the species is Hg{sup +}. Therefore the mid-pulse velocities are: pre-pulse v = .1773c = 5.316 x 10{sup 7} m/s, main pulse v = .2040c = 6.114 x 10{sup 7} m/s, On page 12 it is stated that the pre-compression pulse length is L{sub 0} = 10.0m, and compression is by a 'factor of order 20'. They infer a final pulse length of about .5 m and final durations pre-pulse {tau} {approx} .5/5.316 x 10{sup 7} = 9.4 ns; main pulse {tau} {approx} .5/6.114more » x 10{sup 7} = 8.2 ms. The magnetic rigidity of the beam ions is [B{rho}] = {gamma}m v/e = {l_brace} 112.0 T-m - prepulse/129.5 T-m - mainpulse{r_brace}.« less

Electron induction linacs have been used for over four decades for a variety of applications. As discussed in Chap. 8, these include basic studies in magnetically confined fusion, transport of intense electron beams in various gases, the generation of electromagnetic radiation from free electron lasers, radiation processing of materials and food, and flash X-ray radiography sources.

A 10MW L-band Multi-Beam Klystron (MBK) has been developed and tested by Toshiba, Japan for the European XFEL and a future linear collider projects. The Toshiba MBK has six low-perveance beams operated at low voltage of 115 kV (for 10MW) and six ring-shaped cavities to enable a higher efficiency than a single-beam klystron for a similar power. After the successful acceptance testing at the Toshiba Nasu factory in March 2006, attended by a DESY stuff, the final acceptance test was done at DESY laboratory in June 2006. In these tests, the output power of 10.2MW, more than the design goal (10MW), has been demonstrated at the standard beam voltage of 115 kV at the RF pulse length of 1.5 ms and the beam pulse of 1.7 ms at 10 Hz. The efficiency was 66%. The robustness of the tube was also demonstrated by being operated continuously more than 24 hours above 10MW. Total time of operation on the test stand at DESY already exceeds 750 hours (up to date February 4, 2007). A horizontal version of the Toshiba MBK is now under construction.

Summary form only given. The rise- and fall-time behavior of a pulsed microwave oscillator is of importance to radar and other applications because it can be a transient source of unwanted oscillations and hence the cause of leading/trailing edge jitters during the pulse. Here we present a study of such behavior in the gyrotron backward-wave oscillator (gyro-BWO). The gyro-BWO interaction processes are distinctively different from those of the resonator-based gyrotron oscillator. For the latter device, the oscillation frequency is largely fixed by the resonator structure. Consequently, voltage and pitch-angle variations of the electron beam in the rise and fall portions of the pulse lead to transit angle variations for a number of modes, and each of these modes can be excited over a duration in which its transit angle transitions through the optimum value (~pi). For the gyro-BWO, however, there are no cold resonant modes. The oscillation frequency is free to assume any value over a continuous range and identities of the axial modes are determined entirely by the electron dynamics rather than by the interaction structure. As a result, it has been shown that the (hot) axial modes are linearly characterized by a discrete set of optimum transit angles Theta separated by ~2pi where Theta is the accumulated phase variation of the wave as observed by the electron in traversing the interaction space. The current study reveals theoretically that, during the rise and fall of the beam pulse, the frequency of a given gyro-BWO mode varies in such a way that the transit angle remains at the optimum value for the mode. However, mode competition and mode switching can still occur due to the characteristic asymmetry of the axial mode profiles. A Ka-band gyro-BWO experiment has been carried out to examine the rise/fall-time behavior. Time-frequency analyses of the output pulses show excellent agreement with theoretical predictions. These understandings are expected to provide a useful guide for the design of a stable gyro-BWO operating at a single mode throughout the pulse

The Spallation Neutron Source (SNS) accelerator systems will deliver a 1 GeV, 1.44 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The SNS diagnostics platform is mostly PC-based running Windows XP Embedded for its OS and LabVIEW as its programming language. Coordinating timing among the various diagnostics instruments with the generation of the beam pulse is a challenging task that we have chosen to divide into three phases. First, timing was derived from VME based systems. The second phase, described in this paper, timing pulses were generated by an in house designed, PCI timing card installed in ten diagnostics PCs. Because each timing card has up to four available triggers and we could duplicate triggers using a distribution fan out module, enough triggers were generated for all instruments. This paper describes how the Timing NAD (Network Attached Device) was rapidly developed using our NAD template, LabVIEW’s PCI driver wizard, and LabVIEW Channel Access test screens. The NAD was successfully commissioned and has reliably provided triggers to the instruments. This work supports the coming third phase where every NAD will have its own timing card.

3 pp. (2005)., ophisticated beam-based alignment is essential in future linear colliders to preserve the beam emittance during the transport through the main linac. One such method is dispersion free steering. In this paper different options to implement this method are discussed, based on the use of different accelerating gradients, RF phases and bunch particle types during a beam pulse.

Photothermal depth profiling is usually applied to inhomogeneous materials, and allows to localize the optical inhomogeneity or retrieve the thermal effusivity depth profile by simple monitoring the surface temperature or any related photothermal signal after the pump beam pulse absorption. In this article we want to discuss two different kind of inverse problems; the heat source depth profiling (1 st type), and the effusivity depth profiling (2 nd type). Finally we want to show the equivalence of the two problems, and provide some mathematical tools to get the solutions by the Thermal Wave Backscattering (TWBS).

For maximum utilization of the electron beam, the exposure dose should be tailored to match the geometric and density variations in the product. Such tailoring has already been demonstrated [1] with the spot scanner, which lays down a series of overlapping “spots” of controlled intensity across the product. The new IMPELA macroscanner sweeps every beam pulse across the entire width of the product, and can also be adjusted to provide a non-uniform surface dose. Experience with the spot scanner is summarized, and new experimental results with the macroscanner are presented. The experiments illustrate the flexibility in exposure-dose distribution that can be achieved by varying the beam pulse duration and timing relative to the scan waveform.

The plasma current decay time constant is predicted to be short compared to the pulse length and so self-focusing is predicted for most of the beam pulse. Four- pulse beam envelopes for a high dose case require mitigation, those for a low dose case do not. Methods of mitigation are summarized. Hose instability growth in the plume length is predicted to be minimal.

Summary form only given, as follows. The hard-tube MILO (magnetically insulated transmission line oscillator) is a multigigawatt cross-field microwave tube powered by a 500-kV, 60-kA electron beam. During the initial experiments with a 300-ns beam pulse, a simple velvet cathode configuration was used. However, after extending the beam pulse to 600 ns, problems mainly involving cathode flares compelled cathode design changes to be made. We report on modifications made to the velvet cathode as well as on recent results using a CsI-coated, graphite-fiber cathode. The performance characteristics and relative merits of each cathode are presented.

The phenomenon of beam pulse shortening phenomenon associated with the RF electron gun is reported. The author believes that the beam loading effect plays an important role. The interaction between the electron beam and the deflecting mode is another important factor. >

Improvement in focusing the proton beam onto the antiproton production target necessitates the development of a higher resolution beam profile monitor. Two designs for the construction of a multiwire profile monitor grid are presented. The first is a conventional strung and tensioned Ti wire design. The second is a photo etched Ti grid of wires bonded to a ceramic substrate. Both have a central wire spacing of 125 /spl mu/m. The completed beam profile monitors are designed to operate in a 120 GeV beam pulse of 5/spl times/10/sup 12/ protons with a 1.5 /spl mu/s duration and will be installed in late 1993. >

Two-stage autoacceleration was experimentally realized by passing an annular electron beam through a two-stage passive cavity structure. The kinetic energies of the last quarter part in the beam pulse were increased. Possibility of compression of an intense beam using multistage autoacceleration is discussed.

Brillouin amplifier was numerically simulated by using the theoretic model of transient stimulated Brillouin scattering. Wehave oblained the depleted pump energy extract efficiency, Stokes seed amplification factor, seed beam pulse\|width compression ratio and pump beam pulse\|width compression ratio versus the ratio of seed to pump energy. Experiment was done so as to verify the theory. The theoretical calculation was in good agreement with experimental results.

An analysis of errors connected with beam pulse width variation and instrument noise characteristics has been carried out for charge monitoring of a pulsed accelerator beam traversing an experimental target. The formulae necessary for the selection of optimum monitor and preamplifier parameters for a given range and required accuracy are presented.

A comparison of two advanced accelerator concepts, the plasma wakefield accelerator (PWA) and the dielectric wakefield accelerator (DWA), is presented. Emphasis focuses on the peak accelerating gradients and transformer ratios that can be achieved in these two devices. The effect of finite plasma size on the PWA is also analyzed. For the same cavity geometry and drive beam current, it is found that the dielectric wakefield accelerator can generate a peak field that is comparable to the field that can be generated in the plasma wakefield accelerator. Provided that ideal beam pulse shaping can be achieved, the transformer ratio for the PWA is ten times larger than that for the DWA. A change in this ideal pulse shape results in closer agreement for the transformer ratios. Given these encouraging preliminary results for the DWA it is concluded that the simplicity of employing a passive structure as an accelerating medium warrants further experimental testing of the dielectric wakefield accelerator.

A system for the reduction of the beam pulse repetition rate of the energy-variable Hamburg Isochronous Cyclotron comprising beam pulse supression in the cyclotron center and in the external beam is described.

A beam position and size monitor is described for use with pulsed beams with an intensity above 105 particles/(pulse cm2). It uses a standard multiwire chamber, but the current on each wire is integrated, digitized, and stored for each beam pulse. For optimum determination of beam size, the wire spacing in the chamber should be small compared to the beam size; the present system has 2-mm wire spacing.

A r.f. beam pulse stretcher has been applied successfully to the Carnegie Institute of Technology 450 MeV synchrocyclotron. The beam pulses are stretched completely. The duty factors are almost unity for the long time scale and less than two for the nanosecond time scale due to the phase bunch. The beam loss is 30–40 percent of the bunched beam.

Life-time measurements were carried out by using time to amplitude conversion methods, the information being classified in a two- or three-dimensional spectrum by means of an on-line IBM 360-50 computer. In the first case, the zero time corresponds to the compound nucleus formation and is defined by a fast coincidence between a prompt γ-ray and the beam pulse detected by a thin plastic foil. In this way, the time distributions of all the γ-rays associated with a given reaction are simultaneously measured and can be extracted from the resulting 1024 (Eγ) × 256 (time) channels spectrum. The random coincidence peaks shown by all the curves with the same repetition rate as that of the cyclotron frequency (150–200 ns) can be eliminated by computing the difference between the contributions of a γ-ray and of the continuous background. However, as it is rather difficult to resolve the components of a complex decay curve, when several half-lives of intermediate levels interfere, we turned to a three-dimensional analysis in order to estimate these components. The pulse starting the TAC is due to the same type of coincidence as before but the γ-rays taken into account are now delayed relative to the compound nucleus formation. The size of this delayed γ spectrum is limited by the computer memory and only eight energy regions can be selected (four peaks and the backgrounds nearby, for example). By treatinf the 8 (Eγ2) × 1024 (Eγ2) × 256 (time) channels spectrum obtained, we can derive the decay curves of all the γ-rays with respect to each of the delayed γ transitions.

Recent operating performance is reported and several features of the accelerator design are described. The pulse suppression is achieved using a deflection system in the internal region. It allows the suppression of up to 11 microscopic beam bursts with a suppression of satellite peaks better than 10−4. Also macroscopic pulsing has been made with the deflection system. An axial injection system including a buncher is under test. We are going to accelerate polarized protons and deuterons produced by an atomic beam ion source. An energy stabilization of the extracted beam is reached by a feedback signal derived from the monochromator system. A direct measurement of the energy spectrum of the analyzed beam has been performed in order to assure the assumed ion-optics.

The NBIS (Neutral Beam Injection Source) of a fusion energy reactor requires pulsed, high-energy dc input power. An electron tube pulse modulator, together with control, monitoring and protection equipment, comprise a system to regulate and switch this power. The design and development of salient components for this system are described in this paper.

MOS radiation detectors with memory have been used to time resolve a portion of an alectron beam pulse from a 704 Febetron. These detectors have the three functions of detection, memory, and readout all integrated into a single device so that time resolved detection can be performed without the requirement of realtime diagnostics. Good agreement was obtained between the waveshapes of the time resolved signal of the MOS radiation detector with memory and a real time MOS radiation detector used as a reference monitor of the Febetron's pulse. The time resolution of the detector system was 6.6 nsec. No effort was made to calibrate the output of the MOS detectors with radiation dose. (auth)

An accelerator timing signal and a logic signal derived from an accelerator-produced nuclear event are used to gate on and off, respectively, a train of crystal-controlled oscillator pulses. The frequency distribution of the number of gated oscillator pulses yields detailed information about the accelerator beam pulse shape.

A debuncher with half stochastic and half resonance acceleration has been applied to the INS 160 cm. synchro-cyclotron. The resulting beam intensity has been found to be almost unchangeable with time. The average beam current is 35% as large as it had been before the debuncher was installed.