A Ka-band linearizer TW accelerating structure for the Compact Light XLS project

Ultra-high gradient accelerating structures are in strong demand for the next generation of compact light sources. In the framework of the Compact Light XLS project, we have designed a higher harmonic RF accelerating structure in order to linearize the longitudinal space phase. We here present the design of a compact TW accelerating structure operating on the third harmonic with respect to the linac frequency (11.994 GHz) with a (100-125) MV/m accelerating gradient. Numerical electromagnetic simulations were carried out by using the numerical codes HFSS and CST

Initial electromagnetic and beam dynamics design of a Klystron amplifier for Ka-Band Accelerating Structures

In the framework of the Compact Light XLS project a compact third harmonic RF accelerating structure at 35.982 GHz with respect to the main Linac frequency 11.994 GHz, working with an ultra-high gradient accelerating field in order to linearize the longitudinal space phase is adopted. To this end an innovative high power Ka band klystron operating at about 35.982 GHz has to be designed for feeding the linearizer structure. In addition, we also are planning to design a Ka band klystron operating on the third harmonic of TM01 mode. The generation of a high density electron beam by using the Pierce type electron gun is also requested. The electron gun goal is to produce a converging high beam current that matches to a focusing magnetic field in such way to obtain about 100 MW beam power. This paper proposes a possible design of a electron gun to be used in millimetric waves vacuum tubes. We here report the preliminary studies of the electron gun and the related beam dynamic. Estimations have been obtained by using the numerical code CST and analytical approaches

A Novel Exact Analytical Expression for the Magnetic Field of a Solenoid

In this paper we present the analytical calculations to derive the magnetic field of a solenoid by solving exactly a fractional integral with the use of a novel method. Starting from the Biot-Savart law, we consider a coil of negligible thickness with a stationary electric current. We derive the expressions of the on and off-axes magnetic field components. The results have been compared to some simplified and known analytical formulae as well as to a commercial numerical code showing a good agreement

Nb superconductive thin film coating on flat Cu disks for high gradient applications

In this work we present the characterization of Nb superconductive films deposed on copper substrates with two different techniques: the PVD magnetron sputtering and the Pulsed Laser Ablation. In the first method Nb films ∼ 3µm thick were deposited with an average roughness of 160 nm. The superconductivity properties of these films were also determined with a 4-probe resistivity measurement. Data show a superconducting transition at 9.6K as expected from Nb films. With the second technique thick Nb films were deposited on copper substrates using the Pulsed Laser Ablation. In this case the Rutherford Backscattering was used to determine the thickness and the chemical state of these films that show different degrees of oxidation

Molybdenum oxides coatings for high demanding accelerator components

Large electric gradients are required for a variety of new applications, notably including the extreme high brightness electron sources for X-ray free electron lasers (FELs), radio-frequency (RF) photo-injectors, industrial and medical accelerators, and linear accelerators for particle physics colliders. In the framework of the INFN-LNF, SLAC (USA), KEK (Japan), UCLA (Los Angeles) collaboration, the Frascati National Laboratories (LNF) are involved in the modelling, development, and testing of RF structures devoted to particles acceleration by high gradient electric fields of particles through metal devices. In order to improve the maximum sustainable gradients in normal-conducting RF-accelerating structures, both the RF breakdown and dark current should be minimized. To this purpose, studying new materials as well as manufacturing techniques are mandatory to identify better solutions to such extremely requested applications. In this contribution, we discuss the possibility of using a dedicated coating on a solid copper sample (and other metals) with a relatively thick film to improve and optimize breakdown performances and to minimize the dark current. We present here the first characterization of MoO3 films deposited on copper by pulsed-laser deposition (PLD)

FLASH radiotherapy with electrons: issues related to the production, monitoring, and dosimetric characterization of the beam

Various in vivo experimental works carried out on different animals and organs have shown that it is possible to reduce the damage caused to healthy tissue still preserving the therapeutic efficacy on the tumor tissue, by drastically reducing the total time of dose delivery (<200 ms). This effect, called the FLASH effect, immediately attracted considerable attention within the radiotherapy community, due to the possibility of widening the therapeutic window and treating effectively tumors which appear radioresistant to conventional techniques. Despite the experimental evidence, the radiobiological mechanisms underlying the FLASH effect and the beam parameters contributing to its optimization are not yet known in details. In order to fully understand the FLASH effect, it might be worthy to investigate some alternatives which can further improve the tools adopted so far, in terms of both linac technology and dosimetric systems. This work investigates the problems and solutions concerning the realization of an electron accelerator dedicated to FLASH therapy and optimized for in vivo experiments. Moreover, the work discusses the saturation problems of the most common radiotherapy dosimeters when used in the very high dose-per-pulse FLASH conditions and provides some preliminary experimental data on their behavior

GeV-Class two-fold CW linac driven by an arc-compressor

We present a study of an innovative scheme to generate high repetition rate (MHz-class) GeV electron beams by adopting a two-pass two-way acceleration in a super-conducting Linac operated in Continuous Wave (CW) mode. The beam is accelerated twice in the Linac by being re-injected, after the first pass, in opposite direction of propagation. The task of recirculating the electron beam is performed by an arc compressor composed by 14 Double Bend Achromat (DBA). In this paper, we study the main issues of the two-fold acceleration scheme, the electron beam quality parameters preservation (emittance, energy spread), together with the bunch compression performance of the arc compressor, aiming to operate an X-ray Free Electron Laser. The requested power to supply the cryogenic plant and the RF sources is also significantly reduced w.r.t a conventional one-pass SC Linac for the same final energy