Microwave Discharge Ion Sources

This chapter describes the basic principles, design features and characteristics of microwave discharge ion sources. A suitable source for the production of intense beams for high-power accelerators must satisfy the requirements of high brightness, stability and reliability. The 2.45 GHz off-resonance microwave discharge sources are ideal devices to generate the required beams, as they produce multimilliampere beams of protons, deuterons and singly charged ions. A description of different technical designs will be given, analysing their performance, with particular attention being paid to the quality of the beam, especially in terms of its emittance.Comment: 21 pages, contribution to the CAS-CERN Accelerator School: Ion Sources, Senec, Slovakia, 29 May - 8 June 2012, edited by R. Baile

Conductor losses calculation in two-dimensional simulations of H-plane rectangular waveguides

This paper presents a novel numerical approach to simulate H-plane rectangular-waveguide microwave circuits considering a reduced quasi-2D simulation domain with benefits for computational cost and time. With the aim to evaluate the attenuation of the full height 3D component, we propose a modified expression for the waveguide top/bottom wall conductivity. Numerical 2D simulations are validated against results from full wave 3-D commercial electromagnetic simulator. After a benchmark on a simple straight waveguide model, the method has been successfully applied to an asymmetric un-balanced power splitter, where an accurate power loss prediction is mandatory. Simulation time and memory consumption can be reduced by a factor ten and seven respectively, in comparison with complete 3D geometries. Finally, we show that, also for quasi-2D E-bend waveguide, a case where the translational H-plane symmetry is broken, the error on conductor losses computation is mitigated by our approach since the method remains still valid in a first approximation

Study of charge state enhancement by means of the coupling of a Laser Ion Source to the ECR ion source SERSE

The possibility to produce intense ion beams from solid elements, by using a pulsed Laser ion source as the first stage of the superconducting ECR ion source SERSE is discussed in the following. The Laser ion source may be used to produce negative or positive ions and electrons that are injected into the plasma of SERSE. The design of the experimental setup and the study of the extraction of ions from a target by means of Nd:Yag laser irradiation are briefly described. This Laser ion source will be located in the plasma chamber of the source SERSE, in presence of its magnetic field. A simple evaluation of the charge state enhancement inside the ECR plasma is also presented in the following

Installation of ECR2 at LNS and Preliminary tests

The source ECR2 has been built in 1998 by Pantechnik, according to the design suggested by LNS Ion Source Group. This design entails some improvements with respect to a standard CAPRICE-type source: a) the magnetic field (up to 1.6 T axial, 1.1 T radial) allows to operate the source at 14 GHz in High B mode and at 18 GHz; b) two frequency heating can be used; c) an aluminum made plasma chamber is used in place of the stainless steel one. The main features of ECR2 along with a review of the preliminary tests will be outlined. Typical currents for fully stripped nitrogen are about 25 emA; for the heaviest ions, 1 emA of Kr28+ and 10 emA of Ta27+ have been measured. The installation at LNS has been completed recently and the details will be given

FIRST BEAM FROM THE TRASCO INTENSE PROTON SOURCE (TRIPS) AT INFN-LNS

Abstract The TRASCO intense proton source (TRIPS) has been installed at INFN-LNS THE SOURCE DESIGN The TRASCO Project is a R&D program which goal is the design of an Accelerator Driving System (ADS) for nuclear waste transmutation. The high current cw proton linear accelerator will drive a subcritical system to transmutate nuclear wastes. [1] The accelerator design is shared between different INFN laboratories and the LNS is in charge of the source design and construction. The proton source TRIPS is a high intensity microwave source, which goal is the injection of a minimum proton current of 35 mA in the following RFQ [2], with a rms normalized emittance lower than 0.2π⋅mm⋅mrad for an operating voltage of 80 kV. With respect to other sources for high intensity applications, some new features have been added, according to our experience with the high-intensity source SILHI • the microwave matching system has been improved; • a system to move the coils on-line has been realized; • the extraction system has been optimised with the aim to increase the source availability and reliability, in order to meet the requirement of a driver for an ADS system. The final design of TRIPS is shown in 2 The gaps, the voltage and the extraction holes have been designed in order to reduce the length of the extraction zone (where the beam is uncompensated) and to reduce the aperture-lens effect. Rms normalized emittance below 0.2π mm mrad (including the beam halo) have been calculated EXPERIMENTAL RESULTS CONCLUSION AND FUTURE DEVELOPMENTS In table 1 the status of the source is compared with the requirements of the TRASCO project. The requested reliability at 80 kV is not yet achieved, but the source performance are already good in terms of beam intensity, reproducibility and stability. The innovative solutions presented above have confirmed their validity. We are confident that in a few months a more significant reliability test at 80 3 kV (over two weeks) can be done. As this goal will be accomplished, the emittance measurements can be done with a similar emittance measuring device as the one described in ACKNOWLEDGEMENT

Low power RF test of a quadrupole-free X-Band mode launcher for high brightness applications

In this work we present the low power RF characterization of a novel TM01 X-band mode launcher for the new generation of high brightness RF photo-injectors. The proposed mode launcher exploits a fourfold symmetry which minimizes both the dipole and the quadrupole fields in order to mitigate the emittance growth in the early stages of the acceleration process. Two identical aluminum mode launchers have been assembled and measured in back-to-back configurations for three different central waveguide lengths. From the back-to-back results we infer the performance of each mode launcher. The low power RF test, performed at the Istituto Nazionale di Fisica Nucleare Laboratori Nazionali del Sud (INFN-LNS), validate both the numerical simulations and the quality of fabrication. An oxygen-free high-conductivity copper version of the device is being manufactured for high power and ultra high vacuum tests that are planned to be conducted at SLAC

The IsoDAR high intensity H2+ transport and injection tests

This technical report reviews the tests performed at the Best Cyclotron Systems, Inc. facility in regards to developing a cost effective ion source, beam line transport system, and acceleration system capable of high H[subscript 2][superscript +] current output for the IsoDAR (Isotope Decay At Rest) experiment. We begin by outlining the requirements for the IsoDAR experiment then provide overviews of the Versatile Ion Source (VIS), Low Energy Beam Transport (LEBT) system, spiral inflector, and cyclotron. The experimental measurements are then discussed and the results are compared with a thorough set of simulation studies. Of particular importance we note that the VIS proved to be a reliable ion source capable of generating a large amount of H[subscript 2][superscript +] current. The results suggest that with further upgrades, the VIS could potentially be a suitable candidate for IsoDAR. The conclusion outlines the key results from our tests and introduces the forthcoming work this technical report has motivated.National Science Foundation (U.S.) (PHY-1148134)Massachusetts Institute of Technology (Seed Fund)Massachusetts Institute of Technology (Bose Fellowship

Application of Ferroelectric Cathodes to Enhance the Ion Yield in the Caesar Source at LNS

With increasing RF power the electron concentration in the plasma of ECR ion sources is decreasing in comparison to the ion concentration, so that the plasma is charging up positively. Direct injection of electrons into the ECR plasma can increase the electron charge density and the ion current yield. We have used ferroelectric cathodes to inject electrons into the Argon plasma of the CAESAR ion source at INFN-LNS (Catania, Italy). The cathode was placed at about 10 cm from the hot plasma and a bipolar high voltage pulse of 1.6 kV was used to trigger the electron emission. No additional acceleration has been provided. The use of the ferroelectric cathode leads to an increase of about 30% of the Ar8+ intensity, which has been monitored during the test. In addition, magneto-hydrodynamic instabilities in the ECR source were damped during and after electron injection

The Flexible Plasma Trap (FPT) for the production of overdense plasmas

Electron Cyclotron Resonance Ion Sources are currently the most efficient ionsources among those used in facilities dedicated to nuclear physics. The needfor a more flexible magnetic field and RF injection system suggested to designand develop a different type of plasma trap, named Flexible Plasma Trap (FPT).The magnetic field of FPT is generated by means of three coils while microwavesin the range 4-7 GHz can be injected by three different inputs, one placedalong the axis and two placed radially. FPT can work in different plasmaheating schemes so it will be an ideal tool for studies of plasma andmultidisciplinary physics. Moreover, a microwave launcher has been designed andinstalled to the FPT for launching microwaves with a variable tilt angle withrespect to the magnetic field. This paper describes the characteristics of theFPT along with the preliminary results of plasma diagnostics