Backscattering Sources Research Articles

Progress in the energy upgrade of the Southern European Thomson back-scattering source (STAR)

The Southern European Thomson back-scattering source for Applied Research (STAR) is a high-energy photon facility located on the campus of the University of Calabria (UniCal). The facility was designed for its first phase to operate with an electron and photon energy up to 85 MeV and 140 keV respectively. For the second phase of the project the energy of the electrons, and thereby the photons, would be increased up to 150 MeV and 350 keV respectively. The Italian Institute for Nuclear Physics (INFN) was awarded the project for installing, testing, and commissioning the energy upgrade of the electron beamline. In this article, we will outline the progress of this upgrade. In particular the completion of the site acceptance test of the RF system and the IT infrastructure combined with the control system software.

Correlation relationship between the dissipative and conservative backscattering components in the ring resonator of a laser gyroscope

We report the results of measuring the complex coupling coefficients in ring He – Ne lasers with a radiation wavelength of 632.8 nm. It is found that in assembling ring resonators from mirrors of the same quality, there is no correlation between the dissipative and conservative backscattering components. The analysis of the measurement results shows that this behaviour is associated with the speckle structure of the backscattered field in the ring resonator. The presence of backscattering (BS) sources with a random phase on the mirrors’ surface leads to a spread in the values of the BS parameters, which is described by the Rayleigh distribution function. Ways to reduce the spread in the values of dissipative and conservative backscattering components in assembling the ring resonators are discussed.

Command and control system for the STAR X-ray source

The Southern Europe Thomson Backscattering Source for Applied Research (STAR) is a compact hard Xray source designed by INFN, for advanced applied materials-science research. It is funded by Progetto MaTeRiA, a partnership between the University of Calabria and CNISM (Consorzio Nazionale Interuniversitario per le Scienze fisiche della Materia).The machine has been installed at the University of Calabria (UNICAL); the X-ray beam is produced using the Thomson Back-scattering process, where relativistic electron bunches, accelerated by a 60 MeV Linear Accelerator (LINAC), interact with very short photon pulses, produced a by a 30 mJ@5 ps IR (Infrared) Pulsed Laser.The EPICS-based command/control system (ComConS) of the STAR machine has been designed and currently is under commissioning, using state of the art technologies and making extensive use of COTS hardware and software, assuring full control and supervision of the whole machine and all relevant subsystems: Beam diagnostics, Magnets power supplies, RF devices, Laser systems, Vacuum subsystem, Machine Protection System, Personnel Protection System and Trigger and Timing system.A growth potential has been considered since design phase, in order to take into account any future expansions of the control system during the lifecycle of the facility, without impact on the performance. Scalability of systems is also a crucial issue. The current design allows to generate tunable collimated monochromatic X-rays in the range between 10 and 200 keV. Possible future evolution will be to obtain a machine to generate higher energy X-ray beams, towards the MeV. The control system from both SW and HW points of view has to accommodate this need, as well as operating the machine for a long lifecycle.

Spectrum evolution of Rayleigh backscattering in one-dimensional waveguide

Despite the tremendous awareness of Rayleigh scattering characteristics and its considerable research interest for numerous fields, no report has been documented on the dynamic characteristics of spectrum evolution (SpE) and physical law for Rayleigh scattering from a micro perspective. Herein, the dynamic characteristics of the SpE of Rayleigh scattering in a one-dimensional waveguide (ODW) is investigated based on the quantum theory and a SpE-model of Rayleigh backscattering (RBS) source is established. By means of simulation, the evolution law which represents the dynamic process of the spectrum linewidth at a state of continuous scattering is revealed, which is consistent with our previous experimental observation. Moreover, an approximate theoretical prediction of the existing relationship between the spectrum linewidth of RBS source and the transmission length in ODW is proposed, which theoretically provides the feasibility of constructing functional devices suitable to ascertain laser linewidth compression. The designed experimental scheme can be implemented provided the assumptions are fulfilled. In addition, a theoretical model of the micro-cavity structure to realize the deep compression of laser linewidth is proposed.

OA192] Kilovoltage rotational radiotheraphy with the marix/brixs source for partial breast irradiation

Purpose The development of compact sources of high brilliance, mono-chromatic, tunable X-rays with energy in the range 30–150 keV is a topical research field; applications in radiodiagnostics are foreseen. The aim of this work is to propose the use of a compact source based on X-ray Compton back-scattering (also known as Inverse Compton Source, ICS) developed within the MariX/BriXS project [1] , for kilovoltage rotational radiotherapy dedicated to the breast. Methods The proposed source is based on a modified Tigner scheme of push-and-pull twin Super-Conducting Energy Recovery Linacs, just wrapped on itself in order to halve the overall length of the machine. The ICS source was simulated by using the code CAIN and the output X-ray photon beam was obtained. The anticipated performances are a flux up to 1013 photons/s within 5% bandwidth, coming in radiation pulses a few psec long at a repetition rate up to 100 MHz, fully tunable in the 20–150 keV energy range with full control of polarization and adjustable bandwidth in the range 0.5–10%. The simulated X-ray spectrum was used as an input of a previously validated Monte Carlo Geant4 code to calculate the dose distribution in a 50/50 breast phantom during a rotational radiotherapy scan. The pendant breast was modelled as a cylinder of 14 cm diameter and 9 cm height irradiated over 360 deg at 88 keV average energy and a 1-cm tumor was simulated at the isocenter. Results The dose distribution obtained with the kilovoltage beam generated by the ICS source shows that it is possible to perform a partial breast irradiation with dose levels to the target and to the skin, compatible with clinical treatments using conventional linacs. Conclusions We proposed the application of a Compton back-scattering X-ray source for kilovoltage rotational radiotherapy for breast cancer. The technique could be useful for partial breast irradiation with or without injection of a dose enhancement agent, for radiosurgery of small size breast tumors.

Practical Multichannel SAR Imaging in the Maritime Environment

The U.S. Naval Research Laboratory (NRL) recently developed an X-band airborne multichannel synthetic aperture radar (MSAR) test bed system that consists of 32 along-track phase centers. This system was deployed in September 2014 and again in October 2015 to perform extensive and systematic data collections on a variety of land and maritime scenes under different environmental conditions. This paper presents a detailed experimental analysis of imaging in the maritime domain using data captured by the NRL MSAR system. After presenting some of the important details of our NRL MSAR system, we demonstrate velocity-based imaging of a variety of moving backscatter sources including ships and shoaling ocean waves. Our analysis is based on the velocity SAR (VSAR) technique, which was originally conceived by Friedlander and Porat. Practical application of this algorithm in the maritime domain requires a number of pre- and postprocessing stages, which are described here in detail. Our results are then benchmarked against the traditional along-track interferometry, where it is demonstrated that VSAR processing is better able to correctly compensate motion-induced distortion.

Maritime Signature Correction With the NRL Multichannel SAR

This paper describes the Naval Research Laboratory Multichannel Synthetic Aperture Radar (NRL MSAR) and presents initial results from the first field deployment of this system. The NRL MSAR is an airborne test bed designed to investigate remote sensing and surveillance applications that exploit multiple along-track phase centers, particularly applications that require measurement of scene motion. The system operates at X-band and supports 32 along-track phase centers through the use of two transmit horns and 16 receive antennas. As illustrated in this paper, SAR images generated with these phase centers can be coherently combined to directly measure scene motion using the velocity SAR algorithm, and these measurements can then be used to correct the image distortion that the motion causes. In September 2014, this unique radar was deployed for the first time on an airborne platform. This paper presents a description of the system and results from its inaugural deployment, including the correction of distorted maritime signatures. These data were collected over an ocean inlet and contain a variety of moving backscatter sources, including automobiles, ships, shoaling ocean waves, and tidal currents.

Observations and diagnostics in high brightness beams

The brightness is a figure of merit largely used in the light sources, like FEL (Free Electron Lasers), but it is also fundamental in several other applications, as for instance Compton backscattering sources, beam driven plasma accelerators and THz sources. Advanced diagnostics are essential tools in the development of high brightness beams. 6D electron beam diagnostics will be reviewed with emphasis on emittance measurement.

High intensity X/γphoton beams for nuclear physics and photonics

In this manuscript we review the challenges of Compton backscattering sources in advancing photon beam performances in the 1 – 20 MeV energy range, underlining the design criteria bringing to maximum spectral luminosity and briefly describing the main achievements in conceiving and developing new devices (multi-bunch RF cavities and Laser recirculators) for the case of ELI-NP Gamma Beam System (ELI-NP-GBS).

Spectral characteristics of Compton backscattering sources. Linear and nonlinear modes

Compton backscattering (CBS) of laser photons by relativistic electrons is widely used to design X-ray and gamma sources with a bandwidth better than 1% using a tight collimation. In order to obtain a reasonable intensity of the resulting beam one has to increase power of a laser pulse simultaneously with narrowing of the waist in the interaction point. It can lead to nonlinearity of CBS process which is affected on spectral characteristics of the collimated gamma beam (so-called “red-shift” of the spectral line, emission of “soft” photons with energy much less than the spectral line energy). In this paper we have analyzed such an influence using Monte-Carlo technique and have shown that even weak nonlinearity should be taken into account if the gamma beam is formed by a narrow aperture.

Single Shot Radiography Using an All-optical Compton Backscattering Source

The development of compact laser-based synchrotron sources is a field of active research. Here we present recent results on an all-optical Compton backscattering source using laser-accelerated electrons and a plasma mirror, as introduced in [K. Ta Phuoc et al., Nature Photonics 6 (5) (2012) 308-311].Scattering of quasi-monoenergetic electrons of up to 200 MeV energy with their proper drive-beam leads to emission of femtosecond X-ray pulses, whose energies exceed 100 keV. We demonstrate that the photon yield from the source is sufficient to illuminate a centimeter-size sample placed 90 centimeters behind the source.

Unsupervised SAR Image Segmentation Based on a Hierarchical TMF Model in the Discrete Wavelet Domain for Sea Area Detection

Unsupervised synthetic aperture radar (SAR) image segmentation is a fundamental preliminary processing step required for sea area detection in military applications. The purpose of this step is to classify large image areas into different segments to assist with identification of the sea area and the ship target within the image. The recently proposed triplet Markov field (TMF) model has been successfully used for segmentation of nonstationary SAR images. This letter presents a hierarchical TMF model in the discrete wavelet domain of unsupervised SAR image segmentation for sea area detection, which we have named the wavelet hierarchical TMF (WHTMF) model. The WHTMF model can precisely capture the global and local image characteristics in the two-pass computation of posterior distribution. The multiscale likelihood and the multiscale energy function are constructed to capture the intrascale and intrascale dependencies in a random field (X,U). To model the SAR data related to radar backscattering sources, the Gaussian distribution is utilized. The effectiveness of the proposed model for SAR image segmentation is evaluated using synthesized and real SAR data.

Unsupervised SAR Image Segmentation Using a Hierarchical TMF Model

The triplet Markov field (TMF) model recently proposed is suitable for tackling the nonstationary image segmentation. In this letter, we propose a hierarchical TMF (HTMF) model for unsupervised synthetic aperture radar (SAR) image segmentation. In virtue of the Bayesian inference on the quadtree, the HTMF model captures the global and local image characteristics more precisely in the bottom-up and top-down probability computations. In this way, the underlying spatial structure information is effectively propagated. To model the SAR data related to radar backscattering sources, generalized Gamma distribution is utilized. The effectiveness of the proposed HTMF model is demonstrated by application to simulated data and real SAR image segmentation.

Recent developments on techniques for differential phase imaging at the medical beamline of ELETTRA

Over the last decade different phase contrast approaches have been exploited at the medical beamline SYRMEP of the synchrotron radiation facility Elettra in Trieste, Italy. In particular special focus has been drawn to analyzer based imaging and the associated imaging theory and processing. Analyzer based Imaging (ABI) and Diffraction Enhanced Imaging (DEI) techniques have been successfully applied in several biomedical applications. Recently it has been suggested to translate the acquired knowledge in this field towards a Thomson Backscattering Source (TBS), which is presently under development at the Frascati National Laboratories of INFN (Istituto Nazionale di Fisica Nucleare) in Rome, Italy. Such source is capable of producing intense and quasi-monochromatic hard X-ray beams. For the technical implementation of biomedical phase imaging at the TBS a grating interferometer for differential phase contrast imaging has been designed and successfully tested at SYRMEP beamline.

Electron Linac design to drive bright Compton back-scattering gamma-ray sources

The technological development in the field of high brightness linear accelerators and high energy/high quality lasers enables today designing high brilliance Compton-X and Gamma-photon beams suitable for a wide range of applications in the innovative field of nuclear photonics. The challenging requirements of this kind of source comprise: tunable energy (1–20 MeV), very narrow bandwidth (0.3%), and high spectral density (104 photons/s/eV). We present here a study focused on the design and the optimization of an electron Linac aimed to meet the source specifications of the European Extreme Light Infrastructure—Nuclear Physics project, currently funded and seeking for an innovative machine design in order to outperform state-of-the-art facilities. We show that the phase space density of the electron beam, at the collision point against the laser pulse, is the main quality factor characterizing the Linac.

Transport and scattering in inhomogeneous quantum wires

We consider scattering and transport in interacting quantum wires that are connected to leads. Such a setup can be represented by a minimal model of interacting fermions with inhomogeneities in the form of sudden changes in interaction strength and/or velocity. The inhomogeneities generally cause relevant backscattering, so it is a priori unclear if a perfectly ballistic quantum wire can exist in the low temperature limit. We are able to identify such a perfectly conducting fixed point even for large abrupt changes, which in the considered model corresponds to a velocity matching condition. The general position dependent Green's function is calculated in the presence of a sudden change, which is confirmed numerically with high accuracy. The exact form of the interference pattern in the form of density oscillations around inhomogeneities can be used to estimate the effective strength of local backscattering sources.

Unsupervised multi-class segmentation of SAR images using fuzzy triplet Markov fields model

Triplet Markov fields (TMF) model proposed recently is suitable for nonstationary image segmentation. For synthetic aperture radar (SAR) image segmentation, TMF model can adopt diverse statistical models for SAR data related to diverse radar backscattering sources. However, TMF model does not take into account the inherent imprecision associated with SAR images. In this paper, we propose a statistical fuzzy TMF (FTMF) model, which is a fuzzy clustering type treatment of TMF model, for unsupervised multi-class segmentation of SAR images. This paper contributes to SAR image segmentation in four aspects: (1) Nonstationarity of the statistical distribution of SAR intensity/amplitude data is taken into account to improve the spatial modeling capability of fuzzy TMF model. (2) Mean field theory is generalized to deal with planar variables to derive prior probability in fuzzy TMF model, which resolves the problem in Gibbs sampler in terms of computation cost. (3) A fuzzy objective function with regularization by Kullback–Leibler information of fuzzy TMF model is constructed for SAR image segmentation. The introduction of fuzziness for the belongingness of SAR image pixel makes fuzzy TMF model be able to retain more information from SAR image. (4) Fuzzy iterative conditional estimation (ICE) method, as an extension of the general ICE method is proposed to perform the model parameters estimation. The effectiveness of the proposed algorithm is demonstrated by application to simulated data and real SAR images.

Analyzing Tomographic SAR Data of a Forest With Respect to Frequency, Polarization, and Focusing Technique

Forest canopies are semitransparent to microwaves at both L- and P-bands. Thus, a number of scattering sources and different types of scattering mechanisms may contribute to a single range cell of a synthetic aperture radar (SAR) image. By appropriately combining the SAR data of multiple parallel flight paths, a large 2-D aperture is synthesized, which allows for tomographic imaging of the 3-D structure of such semitransparent media and the underlying ground. A separate paper deals with the actual tomographic imaging part that leads to the 3-D data cube. In particular, three focusing techniques are described and analyzed: multilook beamforming, robust Capon beamforming, and multiple signal classification beamforming. In this paper, the resulting data products obtained by tomographically focusing two airborne multibaseline SAR data sets of a partially forested area, one at L-band and another at P-band, are subject to a detailed analysis with respect to the location and the type of backscattering sources. In particular, the following aspects are investigated: 1) The forest structure, as obtained from the vertical profiles of intensities at sample plot locations within the forest, is compared to the height distribution of the top of the forest canopy, as derived from airborne laser scanning data, and profiles are presented for all polarimetric channels and focusing techniques, as well as at both frequencies; 2) the type and location of scattering mechanisms are analyzed as functions of height for the two frequencies, namely, L- and P-bands, and using the polarimetric channels, as well as the Pauli and CloudePottier decompositions thereof; and 3) the accuracy of the ground elevation estimation obtained from the different focusing techniques and the two frequencies is assessed with the help of a lidar-derived digital elevation model.

Status of the inverse Compton backscattering source at Daresbury Laboratory

Inverse Compton scattering is a promising method to implement a high-brightness, ultra-short, energy tuneable X-ray source at accelerator facilities and at laser facilities using laser wake-field acceleration. We have developed an inverse Compton X-ray source driven by the multi-10-TW laser installed at Daresbury Laboratory. Polarized X-ray pulses will be generated through the interaction of laser pulses with electron bunches delivered by the energy recovery linac commissioned at the ALICE facility with spectral peaks ranging from 0.4 to 12 Å, depending on the electron bunch energy and the scattering geometry. X-ray pulses containing up to 10 7 photons per pulse will be created from head-on collisions, with a pulse duration comparable to the incoming electron bunch length. For transverse collisions the laser pulse transit time defines the X-ray pulse duration. The peak spectral brightness is predicted to be up to 10 21 photon/(s mm 2 mrad 2 0.1% Δ λ/ λ). Called COBALD, this source will be initially used as a short-pulse diagnostic for the ALICE electron beam and will explore the extreme challenges of photon/electron beam synchronization, which is a fundamental requirement for all conventional accelerator and laser wake-field-acceleration-based sources.

Inverse Compton backscattering source driven by the multi-10 TW laser installed at Daresbury

AbstractInverse Compton scattering is a promising method to implement a high brightness, ultra-short, energy tunable X-ray source at accelerator facilities. We have developed an inverse Compton backscattering X-ray source driven by the multi-10 TW laser installed at Daresbury. Hard X-rays, with spectral peaks ranging from 15 to 30 keV, depending on the scattering geometry, will be generated through the interaction of laser pulses with electron bunches delivered by the energy recovery linac machine, initially known as energy recovery linac prototype and subsequently renamed accelerators and lasers in combined experiments. X-ray pulses containing 9 × 107 photons per pulse will be created from head-on collisions, with a pulse duration comparable to the incoming electron bunch length. For transverse collisions 8 × 106 photons per pulse will be generated, where the laser pulse transit time defines the X-ray pulse duration. The peak spectral brightness is predicted to be ~1021 photons/(s mm2 mrad2 0.1% Δλ/λ).