Room Temperature Electron Cyclotron Resonance Research Articles

A new 18 GHz room temperature electron cyclotron resonance ion source for highly charged ion beams.

An innovative 18 GHz HIISI (Heavy Ion Ion Source Injector) room temperature Electron Cyclotron Resonance (ECR) ion source (ECRIS) has been designed and constructed at the Department of Physics, University of Jyväskylä (JYFL), for the nuclear physics program of the JYFL Accelerator Laboratory. The primary objective of HIISI is to increase the intensities of medium charge states (M/Q ≅ 5) by a factor of 10 in comparison with the JYFL 14 GHz ECRIS and to increase the maximum usable xenon charge state from 35+ to 44+ to serve the space electronics irradiation testing program. HIISI is equipped with a refrigerated permanent magnet hexapole and a noncylindrical plasma chamber to achieve very strong radial magnetic confinement with Brad = 1.42 T. The commissioning of HIISI began in Fall 2017, and in Spring 2019, it has met the main objectives. As an example, the intensity of the Xe27+ ion beam has improved from 20 μA to 230 μA. In addition, the beam intensity of the Xe44+ ion beam has exceeded the requirement set by the irradiation testing program. The performance of HIISI is comparable to superconducting ECR ion sources with the same maximum microwave frequency of 18 GHz and a total power of 3 kW. For example, Ar16+ and Xe30+ ion beam intensities of 130 μA and 106 μA, respectively, have been obtained with a total microwave power of 3 kW distributed between 18, 17.4, and 14.5 GHz frequencies. The ion beams have been extracted through an 8 mm plasma electrode aperture using 15-17 kV extraction voltage. The latest development work, extracted ion beam intensities, special features, and future prospects of HIISI are presented in this paper.

A new room temperature LECR5 ion source for the SESRI project.

The Space Environment Simulation and Research Infrastructure project, which uses various ion beams as irradiated materials in life science research, is being built at the Harbin Institute of Technology. A new room temperature electron cyclotron resonance ion source, the Lanzhou Electron Cyclotron Resonance Ion Source No. 5 (LECR5), has been designed and constructed. It is an intense, highly charged, heavy ion beam injector which generates ion beams from H to Bi, typically ∼50 eμA 209Bi32+. The LECR5 is designed to operate at microwave frequencies in the range of 14.5-18 GHz. The typical magnetic parameters are designed based on those optimized for SECRAL, which operates at 18 GHz. This paper presents the LECR5 ion source, its test bench, and the preliminary beam results.

SESRI 300MeV Proton and Heavy Ion Accelerator

The SESRI (Space Environment Simulation and Research Infrastructure) is the new national research infrastructure under construction at Harbin Institute of Technology (HIT) in China. This infrastructure is specifically built to simulate the space environment on the ground. The SESRI has kinds of accelerators, and the 300MeV proton and heavy ion accelerator is a major radiation source, which will supply 100-300MeV protons and 7-85MeV/u heavy ions for studying the interaction of high energy space particle radiation with material, device, module and biological entity. To meet above requirements, the facility adopts the combination of room temperature ECR (Electron Cyclotron Resonance) ion source, linac injector and synchrotron. The ion source is required to provide all stable nuclide beams from H+2 to Bi. The linac injector supplies 1MeV/u heavy ion beams and 5MeV proton beam by using RFQ (Radio Frequency Quadrupole) and IH-DTL (Interdigital H-mode type Drift Tube Linac) linac structures. The synchrotron accelerates heavy ions up to 85MeV/u and proton beam 300MeV. And the 3rd integer resonance and RF-KO (RF-Knock-Out) method are adopted for slow extraction. The status of 300MeV proton and heavy ion accelerator design and construction works are briefly described below.

High intensity high charge state ion beam production with an evaporative cooling magnet ECRIS.

LECR4 (Lanzhou ECR ion source No. 4) is a room temperature electron cyclotron resonance ion source, designed to produce high current, high charge state ion beams for the SSC-LINAC injector (a new injector for sector separated cyclotron) at the Institute of Modern Physics. LECR4 also serves as a PoP machine for the application of evaporative cooling technology in accelerator field. To achieve those goals, LECR4 ECR ion source has been optimized for the operation at 18 GHz. During 2014, LECR4 ion source was commissioned at 18 GHz microwave of 1.6 kW. To further study the influence of injection stage to the production of medium and high charge state ion beams, in March 2015, the injection stage with pumping system was installed, and some optimum results were produced, such as 560 eμA of O(7+), 620 eμA of Ar(11+), 430 eμA of Ar(12+), 430 eμA of Xe(20+), and so on. The comparison will be discussed in the paper.

The development of a room temperature electron cyclotron resonance ion source (Lanzhou electron cyclotron resonance ion source No. 4) with evaporative cooling technology at Institute of Modern Physics.

LECR4 (Lanzhou electron cyclotron resonance ion source No. 4) has been successfully constructed at IMP and has also been connected with the Low Energy Beam Transport (LEBT) and Radio Frequency Quadrupole (RFQ) systems. These source magnet coils are cooled through evaporative cooling technology, which is the first attempt with an ECR ion source in the world. The maximum mirror field is 2.5 T (with iron plug) and the effective plasma chamber volume is 1.2 l. It was designed to be operated at 18 GHz and aimed to produce intense multiple charge state heavy ion beams for the linear injector project SSC-Linac at IMP. In February 2014, the first analyzed beam at 18 GHz was extracted. During about three months' commissioning, some outstanding results have been achieved, such as 1.97 emA of O(6+), 1.7 emA of Ar(8+), 1.07 emA of Ar(9+), and 118 euA of Bi(28+). The source has also successfully delivered O(5+) and Ar(8+) ion beams for RFQ commissioning in April 2014. This paper will give a brief overview of the design of LECR4. Then, the latest results of this source at 18 GHz will be presented.

Progress of a room temperature electron cyclotron resonance ion source using evaporative cooling technology at Institute of Modern Physics

A new room temperature ECR ion source, Lanzhou Electron Cyclotron Resonance ion source No. 4 (LECR4, previously named DRAGON), is under intense construction at Institute of Modern Physics. LECR4 is designed to operate with 18 GHz microwave frequency. The maximum axial magnetic fields are 2.3 T at injection and 1.3 T at extraction, and the radial field at the plasma chamber wall of 76 mm inner diameter is 1.0-1.2 T. One of the unique features for LECR4 is that its axial solenoids are winded with solid square copper wires which are immersed in a kind of special evaporative cooling medium for cooling purpose. Till now, a prototype of the cooling system has been successfully constructed and tested, which has demonstrated that the cooling efficiency of the designed system could meet the requirements of LECR4 under the routine operation conditions. All the main components of the ion source have been completed. Assembly and commissioning is ongoing. The latest developments and test results will be presented in this paper.

Development of DRAGON electron cyclotron resonance ion source at Institute of Modern Physics

A new room temperature electron cyclotron resonance (ECR) ion source, DRAGON, is under construction at IMP. DRAGON is designed to operate at microwaves of frequencies of 14.5-18 GHz. Its axial solenoid coils are cooled with evaporative medium to provide an axial magnetic mirror field of 2.5 T at the injection and 1.4 T at the extraction, respectively. In comparison to other conventional room temperature ECR ion sources, DRAGON has so far the largest bore plasma chamber of inner diameter of 126 mm with maximum radial fields of 1.4-1.5 T produced by a non-Halbach permanent sextupole magnet.

ARTEMIS-B: A room-temperature test electron cyclotron resonance ion source for the National Superconducting Cyclotron Laboratory at Michigan State University

The current scheme for ion-beam injection into the coupled cyclotron accelerator at the NSCL involves the use of two electron cyclotron resonance (ECR) ion sources. The first one is a 6.4GHz fully superconducting that will be replaced within two years by SUSI, a third generation 18GHz superconducting ECR ion source. The other source, ARTEMIS, is a room-temperature source based on the AECR-U design and built in collaboration with the University of Jyväskylä in 1999. Due to cyclotron operation constraint, very little time can be allowed to ion source development and optics studies of the cyclotron injection beam line. In this context, NSCL has decided to build ARTEMIS-B an exact replica of its room-temperature ECR ion source. The goal of this project is threefold. One is to improve the overall reliability of cyclotron operation through tests and studies of various ion source parameters that could benefit beam stability, tuning reproducibility, and of course overall extracted currents performance. Second is to implement and test modifications or upgrade made to the ion source: extraction geometry, new resistive or rf oven design, dual frequency use, liner, etc. Finally, this test source will be used to study various ion optics schemes such as electrostatic quadrupole doublet or triplet at the source extraction or the use of a correction sextupole and assess their effect on the ion beam through the use of an emittance scanner and imaging viewer that will be incorporated into ARTEMIS-B beam line. This article reviews the design and construction of ARTEMIS-B along with some initial commissioning results.

Production of highly charged ion beams with the Grenoble test electron cyclotron resonance ion source (plenary)

Grenoble Test Source (GTS) is a room temperature electron cyclotron resonance ion source whose purpose is to deepen the knowledge of this type of device. GTS was designed according to magnetic scaling laws determined with the SERSE source [Hitz et al., Rev. Sci. Instrum. 73, 509 (2002); Gammino et al., ibid. 72, 4090 (2001)] while keeping enough flexibility in terms of magnetic confinement and rf heating to determine best conditions for the production of intense beams of any charge state. First results were presented 1 year ago [Hitz et al., 8th European Particle Accelerator Conference, 2002; 15th International Workshop on ECR Ion Sources, 2002]. Since then, some improvements have been performed mostly in the magnetic confinement, beam extraction and analysis. Updated ion beam intensities are presented: e.g., 0.5 mA of Ar11+ at 18 GHz, 20 μA of Ar16+ and 1.8 μA of Ar17+ when GTS is operated at 14.5 GHz. On the other hand, charge coupled device imagers have been installed to diagnose and monitor the ion beam and some beam images are shown.

Ion sources at the KVI (abstract)

At the KVI there are presently four ion sources available: POLIS, for polarized protons and deuterons, to be injected in the new superconducting cyclotron AGOR ECRIS3, to produce highly charged ions for AGOR, ECRIS4, to produce highly charged ions for the Atomic and Surface Physics research facility (essentially a copy of ECRIS3), and CUSP, for high intensity AGOR beams of protons, deuteron, or alpha particles. We will report here on the performance and status of POLIS and ECRIS3. POLIS is an atomic beam type polarized ion source, according to the well known scheme with a cryo cooled dissociator, watercooled hexapole magnets, “strong field” and “weak field” radio frequency (rf) transitions for hydrogen and deuterium, and a 2.45 GHz electron cyclotron resonance (ECR) type ionizer. The source was constructed in a joint effort with the Forschungszentrum Karlsruhe, Cyclotron department. The ionizer section was modified and can be operated up to 40 kV. Following successful tests and deuteron polarization measurements at low energies, POLIS was connected to AGOR in November 1996. Most parts are now adapted to the AGOR-KVI control system. The first experiments with proton beams (190 MeV) from AGOR were done with polarized beams. As a consequence, the first measurement of proton polarization could be done only during these experiments, and all efforts to improve the polarization had to take place also during experiments. Efforts to get the weak field transition in operation have given a present best value of polarization of 70%±0.5% of the theoretical value. This value is deduced from an assumed analyzing power of the applied reaction. The strong field unit is not perfect; the best value which has been observed is 56%±0.5%. However, the difference between the given polarizations could be the result of a systematic error in the measurement of polarization “zero.” The output of POLIS is in the order of 50 μÅ. The running time is usually 1–2 weeks (with nozzle at 53 K) until the dissociator and nozzle become contaminated; with a nitrogen layer (nozzle at 35 K) the polarization degree tends to be higher, but the running time is reduced to 3–5 days. POLIS has been in operation during more than 70% of the 33 weeks scheduled for experiments with AGOR since November 1996. Present activities concentrate on the improvement of the strong field unit, increasing the ionizer efficiency and the running time. ECRIS3 is a room temperature ECR ion source, with rf and gas feed according to the CAPRICE scheme. Its performance has been reported earlier (RIKEN 95). Gas mixing is important for the production of highly charged ions. Like in other sources, the anomaly for oxygen isotopes has also been measured. One new observation concerning gas mixing, in particular for the production of argon beams, is the following: For medium charge states, e.g., Ar8+, there is a slight preference for helium as a mixing gas, as compared to pure argon. In fact, oxygen is not good here. On the contrary, for high charge states like Ar14+, oxygen is a very good mixing gas, helium has only a small effect, but the best results have been obtained with isotopic O18 as a mixing gas. Recently, the same has been observed with CAPRICE 10 GHz at CEN-Grenoble, and to some extent with ECRIS4.

Formation of dry etched gratings in GaN and InGaN

Sub-micron periodic gratings with pitch ~3,000A were formed in GaN and InGaN using holographic lithography and room temperature electron cyclotron resonance (ECR) BClg3/N2 dry etching at moderate microwave (500 W) and radio frequency (100 W) powers. The process produces uniform gratings without the need for elevated sample temperatures during the etch step.

Superconducting ECR sources

The need for a higher confining field in the Electron Cyclotron Resonance (ECR) ion source traps has pushed towards the use of superconducting magnets. Now many ECR sources work in the High B mode, i.e. with confining field up to 3 B ECR or higher, which for frequency of 14 GHz or higher makes it necessary to use superconducting magnets. A comparison of superconducting ECR sources and room temperature ECR sources will be presented and particular attention will be paid to the results obtained on 6.4 GHz SC-ECRIS at MSU-NSCL and to the project of the 14.5 GHz SERSE, a superconducting ECR source which will be used at Laboratorio Nazionale del Sud (LNS) as injector for the K-800 Superconducting Cyclotron. The original project of its magnetic system has been upgraded by taking into account the results of the High B mode operation of the SC-ECRIS at MSU and now the mirror field may achieve 2.7 T. The magnet design will allow us to operate in a wide range of magnetic configuration and this should make the tuning of the source easy. The prospects for the future will be outlined, along with the two next projects of superconducting ECR sources to be developed at LNS and at Lawrence Berkeley Laboratory.

Room temperature electron cyclotron resonance chemical vapor deposition of high quality TiN

High quality, gold-colored TiN was deposited at room temperature by decomposing TiCl4 in the downstream of an N2/H2 electron cyclotron resonance (ECR) plasma. The morphology of the as-deposited films was investigated by scanning electron microscopy, and the resistivity was measured using the four point probe technique. The films were uniform over 2 in. wafers, with resistivities of 100–150 μΩ cm. Auger electron spectroscopy was used for the determination of the Ti/N ratio and for the detection of contaminants, and shows that the as-deposited films were stoichiometric and chlorine free. The present results represent a major improvement in lowering the deposition temperature of TiN using ECR plasma-enhanced chemical vapor deposition with TiCl4 as reactant.

The effect of space charge on beams extracted from the room temperature electron cyclotron resonance ion source

We have obtained excellent agreement between BEAM-3D calculations and beam profile and emittance measurements of the total extracted beam from the room temperature electron cyclotron resonance (RTECR), when a low degree of beam neutralization is assumed in the calculations, as will be presented in this paper. The beam envelope has approximately a quadratic dependence on drift distance, and space-charge effects dominate the early beam formation and beamline optics matching process.

The effect of space charge on beams extracted from the room temperature electron cyclotron resonance ion source (abstract)

We have obtained excellent agreement between BEAM-3D calculations and beam profile and emittance measurements of the total extracted beam from the room temperature electron cyclotron resonance (RTECR), when a low degree of beam neutralization is assumed in the calculations, as will be presented in this paper. The beam envelope has approximately a quadratic dependence on drift distance, and space-charge effects dominate the early beam formation and beamline optics matching process.

Electron cyclotron resonance plasma stream source for plasma enhanced chemical vapor deposition

An electron cyclotron resonance (ECR) plasma stream source at a frequency of 2.45 GHz was explored and utilized for SiO2 film chemical vapor deposition (CVD). It was found that for high and uniform plasma stream density the large limiting ring and magnetic fields higher than 930 G are required in the ECR plasma chamber. Plasma densities of(4–6)×1010 cm−3 in nitrogen and (6–8)×1011 cm−3 in argon with uniformities of ±5% over an area of 12 cm in diameter were achieved at distances of 30 to 50 cm from the source limiting ring at a microwave power range of 500 to 600 W. The etch of thermal silicon dioxide and polysilicon with CF4 showed uniformity better than ±1% over 5-in. wafers at a distance of 19 cm. SiO2 films were deposited in a mixture of 15% SiH4/N2 and O2 at substrate temperatures of 30 to 200 °C. Room-temperature ECR films had characteristics better than those obtained in conventional plasma enhanced CVD films deposited at 300 °C. ECR films deposited at 200 °C had properties which approach those of thermal silicon oxide.