Beam dynamics in a high brightness linac for short wavelength SASE-FEL experiments

Short wavelength SASE-FEL requires generation and transport up to the undulator entrance of low emittance (~1–2 mm mrad) high peak current (~1–3 kA) electron beams with energy higher than 1 GeV. The propagation of such a high brightness beam takes place in a transition regime from space charge to emittance dominated dynamics, as the beam energy increases. In addition, in downstream magnetic compressor devices where the peak current increases up to kA range, the transition may occur again. Under these conditions, the electron beam has to be properly matched to the linac accelerating sections in order to keep under control emittance oscillations driven by residual space charge effects. Generalized invariant envelope matching conditions are discussed in this paper, showing that an equilibrium between RF focusing forces and space charge/emittance defocusing forces can be attained without any additional external focusing along the linac (no quadrupoles), thus reducing alignment problems and mitigating emittance dilutions due to misalignments and beam parameter jitters

Photoluminescence of radiation-induced color centers in lithium fluoride thin films for advanced diagnostics of proton beams

Systematic irradiation of thermally evaporated 0.8 μm thick polycrystalline lithium fluoride films on glass was performed by proton beams of 3 and 7 MeV energies, produced by a linear accelerator, in a fluence range from 1011 to 1015 protons/cm2. The visible photoluminescence spectra of radiation-induced F2 and F3+ laser active color centers, which possess almost overlapping absorption bands at about 450 nm, were measured under laser pumping at 458 nm. On the basis of simulations of the linear energy transfer with proton penetration depth in LiF, it was possible to obtain the behavior of the measured integrated photoluminescence intensity of proton irradiated LiF films as a function of the deposited dose. The photoluminescence signal is linearly dependent on the deposited dose in the interval from 103 to about 106 Gy, independently from the used proton energies. This behavior is very encouraging for the development of advanced solid state radiation detectors based on optically transparent LiF thin films for proton beam diagnostics and two-dimensional dose mapping

Challenges in plasma and laser wakefield accelerated beams diagnostic

The new frontier in the particle beam accelerator is the so called plasma acceleration. Using the strong electric eld inside a plasma is possible to achieve accelerating gradients order of magnitude larger with respect to the actual technologies. Di erent schemes have been proposed and several already tested, producing beams of energy of several GeV. Mainly two approaches are followed: either the beam is directly produced by the interaction of a TW/PW class laser with a gas jet, or a preexisting particle beam is accelerated in a plasma channel. In both cases a precise determination of the emerging beam parameters is mandatory for the ne tuning of the devices. The measurement of these parameters, in particular the emittance, is not trivial, mainly due to the large energy spread and to the tight focusing of these beams or to the background noise produced in the plasma channel. We show the problems related to the diagnostic of this kind of beams and the proposed or already realized solutions

Beam commissioning of the 35 MeV section in an intensity modulated proton linear accelerator for proton therapy

This paper presents the experimental results on the Terapia Oncologica con Protoni-Intensity Modulated Proton Linear Accelerator (TOP-IMPLART) beam that is currently accelerated up to 35 MeV, with a final target of 150 MeV. The TOP-IMPLART project, funded by the Innovation Department of Regione Lazio (Italy), is led by Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) in collaboration with the Italian Institute of Health and the Oncological Hospital Regina Elena-IFO. The accelerator, under construction and test at ENEA-Frascati laboratories, employs a commercial 425 MHz, 7 MeV injector followed by a sequence of 3 GHz accelerating modules consisting of side coupled drift tube linac (SCDTL) structures up to 71 MeV and coupled cavity linac structures for higher energies. The section from 7 to 35 MeV, consisting on four SCDTL modules, is powered by a single 10 MW klystron and has been successfully commissioned. This result demonstrates the feasibility of a “fully linear” proton therapy accelerator operating at a high frequency and paves the way to a new class of machines in the field of cancer treatment

The THz Radiation Source at the SPARC Facility

The interest for Terahertz (THz) radiation is rapidly growing, both as it is a powerful tool for investigating the behavior of matter at low energy, and as it allows for a number of possible spectroscopic applications spanning from medical science to security. The linacdriven THz source at the SPARC facility can deliver broadband THz pulses with femtosecond shaping and can be used for electron beam diagnostics to fully reconstruct the longitudinal charge distribution. Beyond this application, the possibility to store much more energy in a single THz pulse than table-top sources renders the SPARC THz source very interesting for a spectroscopic use. In addition, taking advantage from electron beam manipulation techniques, high power, narrow-band THz radiation can be also generated. Those source characteristics provide a unique chance to realize THz-pump/THz-probe spectroscopy, a technique practically unexplored up to now

The THz radiation source at SPARC

The linac driven coherent THz radiation source at the SPARC facility is able to deliver broadband THz pulses with femtosecond shaping. In addition, high peak power, narrow-band THz radiation can be also generated, taking advantage from advanced electron beam manipulation techniques, able to generate a train of short electron bunches with THz repetition rate

The Top-Implart Proton Linear Accelerator: Interim Characteristics of the 35 Mev Beam

In the framework of the Italian TOP-IMPLART project (Regione Lazio), ENEA-Frascati, ISS and IFO are developing and constructing the first proton linear accelerator based on an actively scanned beam for tumor radiotherapy with final energy of 150 MeV. An important feature of this accelerator is modularity: an exploitable beam can be delivered at any stage of its construction, which allows for immediate characterization and virtually continuous improvement of its performance. Currently, a sequence of 3 GHz accelerating modules combined with a commercial injector operating at 425 MHz delivers protons up to 35 MeV. Several dosimetry systems were used to obtain preliminary characteristics of the 35-MeV beam in terms of stability and homogeneity. Short-term stability and homogeneity better than 3% and 2.6%, respectively, were demonstrated; for stability an improvement with respect to the respective value obtained for the previous 27 MeV beam

Lithium fluoride thin film detectors for low-energy proton beam diagnostics by photoluminescence of colour centres

Optically transparent LiF thin films thermally evaporated on glass and Si(100) substrates were used for advanced diagnostics of proton beams of energies from 1.4 to 7 MeV produced by a linear accelerator for protontheraphy under development at ENEA C.R. Frascati. The proton irradiation induces the formation of stable colour centres, among them the aggregate F2 and F3 + optically active defects. After exposure of LiF films grown on glass perpendicularly to the proton beams, their accumulated transversal spatial distributions were carefully measured by reading the latent two-dimensional (2-D) fluorescence images stored in the LiF thin layers by local formation of these broad-band visible light-emitting defects with an optical microscope under blue lamp excitation. Taking advantage from the low thickness of LiF thin films and from the linear behaviour of the integrated F2 and F3 + photoluminescence intensities up to the irradiation fluence of ~5x1015 p/cm2, placing a cleaved LiF film grown on Si substrate with the cutted edge perpendicular to the proton beam, the 2-D fluorescence image of the film surface could allow to obtain the depth profile of the energy released by protons, which mainly lose their energy at the end of the path

PRESENT AND PERSPECTIVES OF THE SPARC THz SOURCE

The development of radiation sources in the Terahertz (THz) spectral region has become more and more interesting because of the peculiar characteristics of this radiation: it is non ionizing, it penetrates dielectrics, it is highly absorbed by polar liquids, highly reflected by metals and reveals specific “fingerprint”absorption spectra arising from fundamentals physical processes. The THz source at SPARC is a linac-based source for both longitudinal beam diagnostics and research investigations. Its measured peak power is of the order of 108 W, very competitive with respect to other present sources. The status of the THz radiation source, in particular its generation and properties, is presented and future perspectives are discusse