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This paper explores the transition between Compton Scattering and Inverse Compton Scattering (ICS), which is characterized by an equal exchange of energy and momentum between the colliding particles (electrons and photons). This regime has been called Symmetric Compton Scattering (SCS) and has the unique property of cancelling the energy-angle correlation of scattered photons, and, when the electron recoil is large, transferring mono-chromaticity from one colliding beam to the other, resulting in back-scattered photon beams that are intrinsically monochromatic. The paper suggests that large-recoil SCS or quasi-SCS can be used to design compact intrinsic monochromatic gamma-ray sources based on compact linacs, thus avoiding the use of GeV-class electron beams together with powerful laser/optical systems as those typically required for ICS sources.

This Document contains a complete technical description of the system devoted to the upgrade of the STAR Linear Accelerator (STAR Linac). According to the Contract signed between Universita della Calabria (UniCal) and Istituto Nazionale di Fisica Nucleare (INFN) on May 7th, 2021, INFN is committed to install, test and commission the upgrade of the STAR Linac denominated STAR-HE-Linac (STAR High Energy Linac), hereafter STAR-HEL. The technical components as well as the installation / test procedures and the ancillary equipment involved in such an upgrade are the object of this Document, named Complete Detailed Design Report. A technical offer was submitted by INFN in the frame of its participation to the tender issued by UniCal, describing a possible energy upgrade of the STAR Linac, with an electron beam energy boosted from 65 MeV up to 150 MeV by means of Radiofrequency (RF) accelerating sections and power stations based on S-band technology (ie, 2856 MHz RF frequency). Following the Contract signature, INFN conceived and conceptually designed a technology change that offers several advantages both on performances and on operational reliability of STAR-HEL, based on adopting C-band technology (ie, 5712 MHz RF frequency) for accelerating sections and RF power stations. Such a technology change was illustrated in a dedicated document named "improvement option for STAR-2 HE-Linac", addressed to UniCal STAR Management Board and tender R.U.P. for approval on June 9th, 2021. INFN received a formal letter of approval on June 16th, 2021.

The design of a future multi-TeV muon collider needs new ideas to overcome the technological challenges related to muon production, cooling, accumulation and acceleration. In this paper a layout of a positron driven muon source known as the Low EMittance Muon Accelerator (LEMMA) concept is presented. The positron beam, stored in a ring with high energy acceptance and low emittance, is extracted and driven to a multi-target system, to produce muon pairs at threshold. This solution alleviates the issues related to the power deposited and the integrated Peak Energy Density Deposition (PEDD) on the targets. Muons produced in the multi-target system will then be accumulated before acceleration and injection in the collider. A multi-target line lattice has been designed to cope with the focusing of both the positron and muon beams. Studies on the number, material and thickness of the targets have been carried out. A general layout of the overall scheme and a description is presented, as well as plans for future R&D., 18 pages, 32 figures

The capability of Free-Electron Lasers to generate photon beams with record performances in the domain of MeV-class photon energy for nuclear photonics applications is here analyzed. We discuss possible nuclear FEL working points. Some typical situations are presented and simulated by means of the three-dimensional code GENESIS 1.3. The losses by spontaneous emission and by wakefield induced energy spread are then evaluated. The calculations show the possibility of generating FEL radiation at 1-4 MeV with less than 300 eV of bandwidth with not prohibitive set up requirements, achieving therefore regimes where no other kind of gamma ray sources could arrive.

We present a simple and new scheme for producing multi colour Thomson/Compton radiation with the possibility of controlling separately their polarization, based on the interaction of one single electron beam with two and more laser pulses that can come from the same laser setup or from two different lasers system and that collide with the electrons at different angle inside one optical cavity. One of the most interesting cases for medical applications is to provide two X-ray pulses across the iodine K-edge at 33.2 keV. The iodine is used as contrast medium in various imaging techniques and the availability of two spectral lines accross the K-edge allows one to produce subtraction images with a great increase in accuracy., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The ELI-NP Gamma Beam System is an advanced gamma ray source based on the Compton back-scattering effect with unprecedented specifications of brilliance ( >10²¹), monochromaticity (0.5%) and energy tunability (0.2 - 19.5 MeV), presently under construction in Magurele-Bucharest (RO). Here the head-on collision is foreseen between an intense high power laser beam and a high brightness high quality electron beam with a maximum kinetic energy of 740 MeV. The electron beam dynamics analysis and control for the ELI-NP GBS Linac in the single and multi bunch mode have been investigated and are here illustrated., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

MOPWO004 - ISBN 978-3-95450-122-9; International audience; In this article are presented beam dynamics investiga- tions of a relativistic electron bunch in the compact storage ring ThomX (50 MeV), which is under construction at LAL to produce hard X-ray using Compton Back-Scattering (CBS). The effect of CBS has been implemented in a 6D tracking code. In addition to CBS, the influence of lattice non linearities and various collective effects on the flux of scattered Compton photons is investigated.

WEPFI005 - Work is supported by the French "Agence Nationale de la Recherche" as part of the program "investing in the future" under reference ANR-10-EQPX-51, and also by grants from Region Ile-de-France.; International audience; The RF system of the ThomX* storage ring will consist in a 500 MHz single cell copper cavity of the ELETTRA type, powered with a 50 kW CW solid state amplifier, and the associated Low Level RF feedback and control loops. The low operating energy of 50 - 100 MeV makes the impedances of the cavity higher order modes (HOMs) particularly critical for the beam stability. Their parasitic effects on the beam can be cured byHOMfrequency shifting techniques, based on a fine temperature tuning and a dedicated plunger. A typical cavity temperature stability of ± 0.05oC within a range from 35 up to 80 oC can be achieved by a precise control of its water cooling temperature. On the other hand, the tuning of the cavity fundamental mode is achieved by changing its axial length by means of a mechanical tuner. In order to insure a fine control of the HOM frequencies, a good knowledge of their characteristics is mandatory.The main parameters of the fundamental and of the HOMs up to 4 GHz have been calculated using the HFSS and CST MWS codes. Preliminary measurements results have been obtained and show a good agreement with the simulations.

NSC KIPT proposed to construct a new X‐ray and soft ultraviolet source NESTOR with a 40 – 225 MeV electron storage ring in Kharkov. NESTOR is a new type radiation source on the base of Compton scattering and a storage ring. Electrons are injected in the storage ring at 100 MeV and ramped up to final energy of 225 MeV. So, using interaction angle 10° and 150°, the facility covers operation energy range of radiation from soft ultraviolet trough synchrotron radiation from bending magnets up to hard X‐ray radiation through Compton scattering (∼1 eV ∼1 MeV). It is supposed that stored electron beam current will be of about 200 mA. Along with use of Nd:Yag laser of 10 W average power which was developed by High‐Q laser firm and optical resonator with accumulation gain of about 1000 it allows to provide X‐ray radiation flux up to 1011 phot/s. NESTOR is the cooperative facility and its development is supported by Ukrainian government and NATO SfP project ♯977982. It is supposed that NESTOR will be in operation by mid‐2007 year. The status of the project and main facility systems are described in the report.NSC KIPT proposed to construct a new X‐ray and soft ultraviolet source NESTOR with a 40 – 225 MeV electron storage ring in Kharkov. NESTOR is a new type radiation source on the base of Compton scattering and a storage ring. Electrons are injected in the storage ring at 100 MeV and ramped up to final energy of 225 MeV. So, using interaction angle 10° and 150°, the facility covers operation energy range of radiation from soft ultraviolet trough synchrotron radiation from bending magnets up to hard X‐ray radiation through Compton scattering (∼1 eV ∼1 MeV). It is supposed that stored electron beam current will be of about 200 mA. Along with use of Nd:Yag laser of 10 W average power which was developed by High‐Q laser firm and optical resonator with accumulation gain of about 1000 it allows to provide X‐ray radiation flux up to 1011 phot/s. NESTOR is the cooperative facility and its development is supported by Ukrainian government and NATO SfP project ♯977982. It is supposed that NESTOR will be in operation by...

Compton scattering of polarized photon beam by polarized relativistic electron beam is considered in the report. The numerical comparison of Compton scattering intensity and polarization intensity has been carried out for different directions of initial photon and electron polarization. It was shown that the use of polarized beam leads to considerable increasing of Compton scattering intensity in the range of high photon energy for initial electron beam energy beginning from 5 GeV. The effect of initial polarization of photon and electron beams to final polarization of scattered photon beam was considered. Розглянуто комптонівське розсіяння фотонного пучка на поляризованому релятивістському електроні. Розглянуто диференційний перетин комптонівського розсіяння з урахуванням ефектів поляризації. Доведено, що застосування поляризованих пучків призводить до значного зросту спектральної інтенсивності фотонів, в області високих енергій для початкової енергії електронного пучка від 5 ГеВ. Розглянуто вплив поляризації початкових фотонів на поляризацію комптонівських фотонів. Рассматривается комптоновское рассеяние поляризованного фотонного пучка на поляризованном релятивистском электроне. Рассмотрено дифференциальное сечение комптоновского рассеяния с учетом эффектов поляризации. Было сделано сравнение для различных поляризаций. Показано, что применение поляризованных пучков приводит к значительному увеличению спектральной интенсивности фотонов, в области высоких энергий, для начальной энергии электронного пучка от 5 ГэВ. Рассмотрено влияние поляризации начальных фотонов на поляризацию комптоновских фотонов.

WEPWA060 - ISBN 978-3-95450-122-9; International audience; The last few years the sources of the X-rays NESTOR based on a storage ring with low beam energy and Compton scattering of intense laser beam are under design and development in NSC KIPT. The main task of the project is to develop compact intense X-ray generator on the base of relatively cheap accelerator equipment and up-to-date laser technologies. The paper is devoted to description of the last results on construction and commissioning of the facility.

Work supported by the French Agence Nationale de la recherche as part of the program EQUIPEX under reference ANR-10-EQPX-51, the Ile de France region, CNRS-IN2P3 and Université Paris Sud XI - http://accelconf.web.cern.ch/AccelConf/IPAC2014/papers/wepro052.pdf; A collaboration of seven research institutes and an industry has been set up for the ThomX project, a compact Compton Backscattering Source (CBS) based in Orsay - France. After a period of study and definition of the machine performance, a full description of all the systems has been provided. The infrastructure work has been started and the main systems are in the call for tender phase. In this paper we will illustrate the definitive machine parameters and components characteristics. We will also update the results of the different technical and experimental activities on optical resonators, RF power supplies and on the electron gun.

Free-Electron Lasers are a rapidly growing field for advanced science and applications, and worldwide facilities for intense field generation, characterization and usage are becoming increasingly popular due to their peculiarities, including extremely bright, coherent, wide band tunable ultra-short pulses which are not achievable with other techniques up to now. In this review we give a thorough survey of the latest advances in the Free-Electron Laser-based field generation and detection methodologies and then present the main characteristics of a future THz/IR source, named TerRa@BriXSinO, based on a superconducting linear accelerator. The foreseen source is strongly monochromatic, with a bandwidth of 1% or smaller, highly coherent both transversally and longitudinally, with extreme versatility and high frequency tunability. After introducing the most recent and novel FEL-assisted scientific investigations, including fundamental explorations into complex systems and time-dependent interactions and material dynamics, we present our vision on the potential use of the TerRa facility and analyze some possible applications, ranging from non-linear physics under extreme conditions to polarization sensitive imaging and metamaterial-based sensing.

We present the design study of an innovative scheme to generate high repetition rate (multi-MHz-class) THz radiation pulses by using an Energy Recovered Super Conducting Linac operating in Continuous Wave mode driving a Free-Electron Laser Oscillator. The FEL performance is illustrated for one and two color operation. Start-to-end simulations are presented to assess the capability of this scheme for typical values of wavelengths of interest in the 10–50μm (6–30 THz) range.

Kilovoltage rotational radiotherapy of breast cancer has been proposed as an alternative procedure to the conventional breast radiotherapy with 6 MeV photon beams. The use of orthovoltage X-ray tubes rotating around the breast, instead of conventional medical linear accelerators, would allow for significant reduction of acquisition and management costs. However, the employment of an X-ray tube limits the maximum available photon flux: a synchrotron radiation source could provide a high dose rate, but its clinical use is prevented by the size of such a source. In this work, we propose the use of the BriXS twin Compton pulsed X-ray source as a compact alternative to the synchrotron radiation source, for kilovoltage radiotherapy of breast cancer. This proposed source presents a footprint of 40 m × 20 m, and the X-ray spectrum presents a mean energy of 88 keV with a suitable photon flux. The dose distribution in a simulated radiotherapy session was computed via a Monte Carlo software based on the Geant4 simulation toolkit. The study focused on the skin dose ratio, i.e. the percent ratio between the dose to the skin and that to the tumor volume in the modelled breast. A low skin dose allows for a suitable sparing of skin tissue during radiotherapy. For a cylindrical model breast with a diameter of 140 mm embedding a spherical simulated lesion with a diameter of 10 mm placed at the rotational axis of the cylinder, the calculated skin-to-tumor dose ratio was as low as 7%.

MariX is a research infrastructure conceived for multi-disciplinary studies, based on a cutting-edge system of combined electron accelerators at the forefront of the world-wide scenario of X-ray sources. The generation of X-rays over a large photon energy range will be enabled by two unique X-ray sources: a Free Electron Laser and an inverse Compton source, called BriXS (Bright compact X-ray Source). The X-ray beam provided by BriXS is expected to have an average energy tunable in the range 20–180 keV and intensities between 1011 and 1013 photon/s within a relative bandwidth Δ E / E = 1 –10 % . These characteristics, together with a very small source size ( ~ 20 μ m) and a good transverse coherence, will enable a wide range of applications in the bio-medical field. An additional unique feature of BriXS will be the possibility to make a quick switch of the X-ray energy between two values for dual-energy and K-edge subtraction imaging. In this paper, the expected characteristics of BriXS will be presented, with a particular focus on the features of interest to its possible medical applications.

We propose an innovative method to shift the transversal position of the focal point of an optical cavity keeping it actively frequency stabilized. Our cavity is a 4 mirrors bow-tie cavity and the spatial shift of the resonant mode is obtained by properly rotating the two curved mirrors by piezo actuators. This method allows us to move the transversal position of the cavity focal point of 135 µm in a time of 50 ms, keeping the resonance condition of the cavity by means of the Pound–Drever–Hall technique. We propose to use this technique for the generation of 2-color X-rays via Inverse Compton Scattering (ICS). This technique exploits the large average power stored in the high finesse cavity by shifting the laser beam with respect to the electron beam trajectory, hence controlling the spatial superposition of the electron and photon beams in the interaction region. Arranging two cavities assembled one on top of the other, with different collision angle with the electron beam, allows the generation of X-ray bursts of different energies just by swiftly moving the two cavities, switching the two focal points onto the electron beam trajectory, thus activating in sequence two different ICS spectral lines .

The need of a fs-scale pulsed, high repetition rate, X-ray source for time-resolved fine analysis of matter (spectroscopy and photon scattering) in the linear response regime is addressed by the conceptual design of a facility called MariX (Multi-disciplinary Advanced Research Infrastructure for the generation and application of X-rays) outperforming current X-ray sources for the declared scope. MariX is based on the original design of a two-pass two-way superconducting linear electron accelerator , equipped with an arc compressor, to be operated in CW mode (1 MHz). MariX provides FEL emission in the range 0.2–8 keV with 1 0 8 photons per pulse ideally suited for photoelectric effect and inelastic X-ray scattering experiments. The accelerator complex includes an early stage that supports an advanced inverse Compton source of very high-flux hard X-rays of energies up to 180 keV that is well adapted for large area radiological imaging, realizing a broad science programme and serving a multidisciplinary user community, covering fundamental science of matter and application to life sciences, including health at preclinical and clinical level.

We present the design of a photon–photon collider based on conventional Compton gamma sources for the observation of secondary γ γ production. Two symmetric electron beams, generated by photocathodes and accelerated in linacs, produce two primary gamma rays through Compton back scattering with two high energy lasers. Tuning the system energy to the energy of the photon–photon cross section maximum, a flux of secondary gamma photons is generated. The process is analyzed by start-to-end simulations from the photocathodes to the propagation of the QED photons towards the detector. The new Monte Carlo code ‘Rate Of Scattering Events’ (ROSE) has been developed ad hoc for the counting of the QED events. Realistic numbers of the secondary gamma yield, referring to existing or approved set-ups and a discussion of the feasibility of the experiment are presented.

We present the design of a photon-photon collider based on conventional Compton gamma sources for the observation of elastic $\ensuremath{\gamma}\ensuremath{\gamma}$ scattering. Two symmetric electron beams, generated by photocathodes and accelerated in linacs, produce two primary gamma rays through Compton backscattering with two high energy lasers. The elastic photon-photon scattering is analyzed by start-to-end simulations from the photocathodes to the detector. A new Monte Carlo code has been developed ad hoc for the counting of the QED events. Realistic numbers of the secondary gamma yield, obtained by using the parameters of existing or approved Compton devices, a discussion of the feasibility of the experiment and of the nature of the background are presented.