Search

We present a scheme to generate synchronized THz and Soft X-ray radiation pulses by using a Free-Electron Laser Oscillator driven by a high repetition rate energy recovery linac. The backward THz radiation in the oscillator cavity produces naturally synchronized Soft/Hard X rays via Thomson back-scattering by interacting with a successive electron bunch. The performances of this dual source are illustrated by means of dedicated simulations assessing the capability of the scheme for typical wavelengths of interest, namely up to 50 µm for the short-THz radiation and close to the water window at 3 nm for the X-rays.

We present the conceptual design of a compact light source named BriXSinO. BriXSinO was born as demonstrator of the Marix project, but it is also a dual high flux radiation source Inverse Compton Source (ICS) of X-ray and Free-Electron Laser of THz spectral range radiation conceived for medical applications and general applied research. The accelerator is a push-pull CW-SC Energy Recovery Linac (ERL) based on superconducting cavities technology and allows to sustain MW-class beam power with almost just one hundred kW active power dissipation/consumption. ICS line produces 33 keV monochromatic X-Rays via Compton scattering of the electron beam with a laser system in Fabry-Pérot cavity at a repetition rate of 100 MHz. The THz FEL oscillator is based on an undulator imbedded in optical cavity and generates THz wavelengths from 15 to 50 micron., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

High order modes (HOMs) in multi-cell superconducting cavities are of particular concern in beam dynamics of linear accelerators, mainly those operating in CW mode with high current and high repetition rate. These undesired modes may invoke beam instabilities, beam breakup and increase the energy spread if not correctly pulled out and damped. The study reported in this paper is applied for damping the HOMs in the main Linac of BriXSinO, an ongoing project of an Energy Recovery Linac at LASA INFN laboratory. We developed a numerical model to study the interaction of monopole HOMs with the beam in long timescale. The presented model, named HOMEN (High Order Modes Evolution based on eNergy budget), allows the evaluation of the loss factor Kloss, crucial for evaluating the perturbing modes. At the same time, electromagnetic simulations of the standing wave multicell cavity, highlighted the dangerous modes and revealed a tolerable beam energy spread induced by HOMs. This method allows us to distinguish all dangerous modes of our interest for implementing the necessary damping mechanisms., Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK

In the framework of the preparatory activities to the BriXSino project, a test bench for testing Cs₂Te photocathode at 100 MHz laser repetition rate has been installed at INFN LASA. This high repetition operation mode is foreseen to be the base operation mode of BriXSino and a qualification of the Cs₂Te photocathodes is a key component. While we are not at full specification due to the limited HV of the present DC gun, we discuss the status of the test bench and the initial results., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

ACTIS (Arc Compressor Test In a Synchrotron) is an experiment aimed to demonstrate the reliability of arc compressors as lattices capable to increase peak current and brightness of an electron beam as it is bent at large angles. This kind of devices has been proposed at theoretical level in several works over the past decades and could be the key to achieve compact and sustainable Free Electron Lasers in the near future. The experiment has been developed since 2019 in the joint effort between INFN, Solaris National Synchrotron Radiation Center and Elettra - S.T. S.C.p.A. The experiment will take place at Solaris (Kraków). Solaris is a synchrotron whose ring is injected by a 550 MeV linac that will be used to prepare the beam with a proper chirp. ACTIS involves also the commissioning of two beam length detectors to be installed downstream of the linac and of the first ring lap. In addition, the low energy model of the machine was built to identify the optimal working point for the experiment and to foresee the longitudinal profile of the beam that will be measured. In this work we present the experiment and report first results obtained in the study phase., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

Spherical joints, or rod-ends, are critical components employed in flight control systems to connect the actuator to the aerodynamic surface and to the airframe. As any mechanical component, rod-ends are subjected to a wide range of failure modes, which can cause catastrophic effects at the actuator level and hence at the aircraft level. Despite this criticality, they are often overlooked in studies concerning the definition of new Prognostics and Health Management systems for flight control actuators, mainly due to the lack of sensors to monitor their behavior. The definition of a physics-based model of the rod-ends is hence a required preliminary step to pursue the definition of novel Health Monitoring schemes able to detect the fault inception in these components and track their evolution in time up to failure conditions. In this paper, a model working under few simplifying assumptions is proposed, complete with a Finite-Difference Method solution for the behavior of the lubricating film. The proposed model is then applied to a pre-existing, experimentally validated model of the flight control actuators of an in-service, wide-body commercial aircraft in presence of excessive backlash. Comments on the rod-end model are presented and further work is laid out.

Hollow core dielectric microstructures powered by lasers represent a new and promising area of accelerator research thanks to the higher damage threshold and accelerating gradients with respect to metals at optical wavelengths. In this paper we present the design of a dielectric Electromagnetic Band Gap (EBG) mode converter for high-power coupling of the accelerating mode in Dielectric Laser Accelerators (DLAs). The design is wavelength-independent, and here we propose an implementation operating at 90.505 GHz (wavelength 3.3 mm) based on a silicon woodpile structure. The coupler is composed by two perpendicularly coupled hollow-core waveguides: a TE-like mode waveguide (excited from RF/laser power) and a TM-like mode accelerating waveguide. The structure has been numerically designed and optimized, presenting Insertion Losses (IL) 0.3 dB and an efficient mode conversion in the operating bandwidth. The properties and effectiveness of the confined accelerating mode have been optimized in order to derive the needed accelerating gradient. The simulated electric field has been used as input for Astra beam-dynamics simulations in order to compute the beam properties., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

We present the conceptual designs of BriXS and BriXSino (a minimal test-bench demonstrator of proof of principle) for a compact X-ray Source based on innovative push-pull ERLs. BriXS, the first stage of the Marix project, is a Compton X-ray source based on superconducting cavity technology with energy recirculation and on a laser system in Fabry-Pérot cavity at a repetition rate of 100 MHz, producing 20-180 keV radiation for medical applications. The energy recovery scheme based on a modified folded push-pull CW-SC twin Linac ensemble allows to sustain MW-class beam power with almost just one hundred kW active power dissipation/consumption., Proceedings of the 63th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, ERL2019, Berlin, Germany

Summary In the neocortex, synaptic inhibition shapes all forms of spontaneous and sensory evoked activity. Importantly, inhibitory transmission is highly plastic, but the functional role of inhibitory synaptic plasticity is unknown. In the mouse barrel cortex, activation of layer (L) 2/3 pyramidal neurons (PNs) elicits strong feedforward inhibition (FFI) onto L5 PNs. We find that FFI involving parvalbumin (PV)-expressing cells is strongly potentiated by postsynaptic PN burst firing. FFI plasticity modifies the PN excitation-to-inhibition (E/I) ratio, strongly modulates PN gain, and alters information transfer across cortical layers. Moreover, our LTPi-inducing protocol modifies firing of L5 PNs and alters the temporal association of PN spikes to γ-oscillations both in vitro and in vivo. All of these effects are captured by unbalancing the E/I ratio in a feedforward inhibition circuit model. Altogether, our results indicate that activity-dependent modulation of perisomatic inhibitory strength effectively influences the participation of single principal cortical neurons to cognition-relevant network activity., Graphical Abstract, Highlights • Feedforward inhibition (FFI) of layer 5 pyramidal neurons (PNs) is highly plastic • Long-term potentiation of FFI modulates spiking activity of layer 5 PNs • LTPi affects information transfer across cortical layers • The strength of LTPi determines the phase locking of PN firing to γ-oscillations, Lourenço et al. demonstrate that burst firing of layer 5 pyramidal neurons (PNs) induces long-term potentiation of inhibition (LTPi). LTPi strongly affects PN input/output spikes, prevents transfer of information across cortical layers, and affects phase locking of PN firing to cognition-relevant rhythmic activity.

International audience; Exposure to stress during early life (infancy/childhood) has long-term effects on the structure and function of the prefrontal cortex (PFC), and increases the risk for adult depression and anxiety disorders. However, little is known about the molecular and cellular mechanisms of these effects. Here, we focused on changes induced by chronic maternal separation during the first 2 weeks of postnatal life. Unbiased mRNA expression profiling in the medial PFC (mPFC) of maternally separated (MS) pups identified an increased expression of myelin-related genes and a decreased expression of immediate early genes. Oligodendrocyte lineage markers and birthdating experiments indicated a precocious oligodendrocyte differentiation in the mPFC at P15, leading to a depletion of the oligodendrocyte progenitor pool in MS adults. We tested the role of neuronal activity in oligodendrogenesis, using designed receptors exclusively activated by designed drugs (DREADDs) techniques. hM4Di or hM3Dq constructs were transfected into mPFC neurons using fast-acting AAV8 viruses. Reduction of mPFC neuron excitability during the first 2 postnatal weeks caused a premature differentiation of oligodendrocytes similar to the MS pups, while chemogenetic activation normalised it in the MS animals. Bidirectional manipulation of neuron excitability in the mPFC during the P2-P14 period had long lasting effects on adult emotional behaviours and on temporal object recognition: hM4Di mimicked MS effects, while hM3Dq prevented the pro-depressive effects and short-term memory impairment of MS. Thus, our results identify neuronal activity as a critical target of early-life stress and demonstrate its function in controlling both postnatal oligodendrogenesis and adult mPFC-related behaviours.

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. The Low Emittance Muon Accelerator (LEMMA) concept *,** presents in this paper an upgraded layout of a positron driven muon source. The positron beam, stored in a ring with high energy acceptance and low emittance, is extracted and driven in a push-pull configuration to a multi-target system, to produce muon pairs at threshold on the target’s electrons. This solution alleviates the issues related to the power deposited and the integrated Peak Energy Density Deposition on the targets. Muons produced in the multi-target system will then be accumulated in many parallel rings before acceleration and injection in the collider. A special 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, Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Operation of modern particle accelerators require high qualitity beams and conseguently sensitive diagnostic system in order to monitories and characterize the beam during the acceleration and transport. A turn-key high level software BOLINA (Beam Orbit for Linear Accelerators) has been developed to fully characterise the 6D beam phase space in order to help operator during commissioning with an easily scalable suite for any high brightness LINAC. In this work will be presented the diagnostic toolkit is presented as designed for the ELI-NP Gamma Beam System (GBS) a radiation source based on the Compton back scattering effect able to provide tunable gamma rays in the 0.2-20 MeV range with narrow bandwidth (0.3% and a high spectral density (10⁴ photons/sec/eV) by the Compton backscattering effect. BOLINA suite is design to be machine independent, thanks to the file exchanges with the EPICS based control system. Simulation of raw data of the ELI-NP-GBS accelerator has been used to test the capabilities of the diagnostic toolkit., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

We present the study of the optimization of the optical cavity parameters, in order to maximise the flux of scattered photons in the Compton scattering process. In the optimisation, we compensate the losses of the photon number due to the elliptical shape of the laser pulse in optical cavity with a high focusing electron beam., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

MariX (Multidisciplinary advanced research infra-structure with X-rays) is a joint project of INFN and University of Milan, aiming at developing a twin X-ray Source of advanced characteristics for the future Sci-entific Campus of the University of Milan. Presently in its design study phase, it will be built in the post Expo area located in north-west Milan district. The first component of the X-source MariX is BriXS (Bright and compact X-ray Source), a Compton X-ray source based on superconducting cavities technology for the electron beam with energy recirculation and on a laser system in Fabry-Pérot cavity at a repetition rate of 100 MHz, producing 20-180 keV radiation for medical applications. The BriXS accelerator is also serving as injector of a 3.8 GeV superconductive linac, driving a X-ray FEL at 1 MHz, for providing coherent, moderate flux radiation at 0.3-10 KeV at 1 MHz. Scientific case, layout and typical parameters of MariX will be discussed., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada