Operation Of Ion Source Research Articles

Ion beam stability prediction of ECR ion source based on TCN-DTW network

The Electron Cyclotron Resonance (ECR) ion source is an irreplaceable apparatus for producing high-intensity, highly charged heavy ion beams, representing a critical component for heavy ion accelerators. The operation of the ECR ion source is inherently influenced by various factors, leading to fluctuations in beam intensity. Such instability not only diminishes the efficacy of accelerator operations but also introduces distortions in terminal experimental data. Addressing these challenges, this study proposes the application of a Temporal Convolutional Network (TCN) based on a Dynamic Time Warping (DTW) loss function (TCN-DTW) for predicting the stability of the ion beams. Prior to constructing the prediction network, raw data undergoes preprocessing through an Interquartile Range (IQR) anomaly detection mechanism and the Savitzky-Golay (SG) filtering algorithm with an adaptive window. Experimental results demonstrate a substantial enhancement in prediction performance when employing the TCN network with the DTW loss function compared to traditional alternatives. This approach facilitates effective forecasting of the ion source beam current trend, offering a basis for the control and correction of long-term stability. Consequently, it provides valuable insights for optimizing the ECR ion source and enhancing overall accelerator operational performance.

Innovative Cesiation Deriving Incredible 145 mA Beam from J-PARC Cesiated RF-Driven H− Ion Source

In NIBS2022, the stable 8 hours operation of the J-PARC cesiated RF-driven H− ion source (IS) in a test-stand with a 69.9 keV 120 mA beam and a beam duty factor of 4 % (1 ms x 40 Hz) was reported. However, the Cesiation condition was produced after many times and rather large amount of Cs and H2Os injections. The fluctuation of the H− ion beam intensity (IH −) in a pulse and the transverse emittances were rather larger than those for the previous 65 keV 110 mA operation. The plasma electrode temperature (TPE) of 254 °C much higher than that not only for the usual J-PARC IS (about 70 °C) but also for the standard cesiated H− ion sources (180 ∼ 200 °C) suggested the existence of novel H2O mediated cesiation surviving against the high TPE. In this paper, the J-PARC IS improvements based upon a hypothesis of the best cesiation constituted of sub monolayer H2O (chemically bound with Mo) mediated cesiation and Cs half monolayer on remaining surface are presented. The innovative cesiation derived a 76.5 keV 145 mA beam stably with the small beam fluctuation and transverse emittances suitable for Radio Frequency Quadrupole LINACs of high energy LINACs. The measured results of the 145 mA / 83 mA beam, extraction electrode current and RF waveforms, parameter trends of an 8 hours 145 mA operation and the transverse emittances are presented. The optimum TPE was increased from 70 °C to 230 °C. Furthermore, the beam intensity for the J-PARC IS operation energy of 52.5 keV was increased from 72 mA to 83 mA, which was consistent with the 1.5 power perveance law on the beam energy compared with 145 mA for 76.5 keV.

Sample Injection for Real-Time Analysis (SIRTA) Using GC-MS with Cold EI.

There is a continual demand for advanced methods and instruments for real-time analysis (RTA). Most of the current RTA techniques based on MS involve ambient desorption ionization technology. However, flow injection of liquid extracted samples is another option without added modifications or cost to existing LC-MS instruments. In this work, we introduce a new RTA approach named sample injection for real-time analysis (SIRTA) using GC-MS with Cold EI. In SIRTA, the standard GC column is replaced with a 1 m long 0.1 mm I.D. fused silica capillary that connects the GC injector to the MS transfer-line of Cold EI. Thus, SIRTA with Cold EI imposes no need for any additional instrumentation; hence, it is characterized by zero added cost. Like in flow injection in MS of LC-MS, the sample is dissolved in ∼1 mL methanol or another solvent. Subsequently, the vial is placed in the GC-MS autosampler while using a standard syringe for injection without any GC separation. The analysis takes merely 0.2-0.7 min, ensuring rapid and consecutive analyses. Unlike standard EI, Cold EI enables SIRTA by taking advantage of its fly through open ion source to avoid overwhelming the ion source during the elution of solvents while still providing enhanced molecular ions for nearly all analytes. In this study, we demonstrated SIRTA Cold EI analysis of 12 compounds and 7 mixtures, including various prescription and illicit drugs, cannabis and petroleum samples, and other synthetic organic compounds including those with molecular weight up to 800 g/mol.

An experimental investigation of the proton fraction in a three electrode 2.45 GHz ECR ion source

The ion beam extracted from a proton ion source contains H+ ion along with H2 + and H3 + molecular ions. In this work, the ionic fractions in the extracted beam of ECR ion source were measured using an analyzing magnet. A computerized proton fraction measurement setup is described in detail with instrumentation and control for pulsed operation of the ECR ion source. A timing diagram has been incorporated for trigger synchronization illustrating the process of pulsing the plasma, controlling the analyzing magnet parameters and acquiring data about the magnetic field and beam current. The proton fraction was measured in two cases, in the first case using SS304 plasma chamber and in the second case incorporating aluminium (Al) cylinder and boron nitride (BN) plates inside the plasma chamber. In the first case, the proton fraction was found to be in the range of ∼60% and in the second case because of the presence of secondary electron donors it increased to 93%. In order to understand the enhancement of H+ fraction in the hydrogen plasma, plasma parameters (ne , Te and EEDF) and its dependence on microwave power and neutral gas pressure were investigated.

Discoloration of RF antenna coil surface after long-term operation of J-PARC ion source

In J-PARC (Japan Proton Accelerator Research Complex) center, the continuous operation period of the Radio Frequency (RF) negative hydrogen ion (H−) source equipped with the internal RF antenna coil is extended step by step in these 6–7 years for the goal to supply stable beam during the entire period of J-PARC user operation each year. In 2022, the continuous ion source operation for 4,001 hours (5.5 months) was achieved with 60 mA H− beam current at the ion source exit, 25 Hz repetition, mainly 500 μs beam pulse width, and 25 kW RF power injection. As the lifetime of the RF ion source is mainly limited by the deterioration of the enamel coating on the RF antenna coil, a detailed evaluation of the antenna surface is required to ensure the feasibility of the further extension of the operation period. In the present study, surface discoloration on the RF antenna coil observed after 5 months of operation is investigated by the application of a digital microscope and SEM/EDS analyses. The EDS analyses show that depositions of the sputtered stainless steel elements and the injected cesium are the most possible candidates for impurities on the enamel coating. The dimension measurements of the RF antenna thickness before and after the long-term operation also support the assumption that the discoloration is due to the deposited elements and hence insulation of the RF antenna coil by enamel coating is maintained. Possible mechanisms leading to antenna deterioration starting from element depositions on the antenna coating are also discussed in the summary part of this manuscript.

Sputter sample preparation for ion beam delivery of radium-223 at ATLAS.

A radium-223 ion beam was delivered to an experiment from the electron cyclotron resonance ion source, ECR2, at the Argonne Tandem Linac Accelerator System (ATLAS). The radium-223 material was in a nitrate salt form within a vial, prior to being converted to a usable sputter sample. The sputter sample was produced using a new sample preparation method, where the radium nitrate was dissolved into a solution and pipetted onto pressed aluminum powder. This sample was then allowed to dry, distributing the radium-223 material throughout the sputter sample. Ion source operation using the radium sputter sample is described with the operating parameters listed. The intensity and energy requirements for this ion beam were 1 × 106 particles/s and 1.07 GeV, respectively. Because the intensity is relatively low compared to most experiments at ATLAS, previously developed accelerator mass spectrometry methods were used Scott etal. [Rev. Sci. Instrum. 87, 02A732 (2016)] to avoid the need for tuning of the low-intensity beam of interest. Handling of the radium material, as well as loading and unloading of the sputter sample from ECR2, required collaboration with Health Physics. Procedures were used and dry runs were carried out before, during, and after the experiment to ensure the safety of the workers. The processes used and lessons learned are described within.

Heat loads on the accelerator grids of the ITER HNB prototype

Among the heating and current drive system which are being developed for the ITER experimental reactor, 2 neutral beam injectors with a power of 16.5 MW each will be based on the acceleration of H−/D− ions up to the energy of 870 keV / 1 MeV. Dealing with an accelerated beam power up to 40 MW, beam divergence, aiming and homogeneity have to be optimized to avoid damaging the beamline components or the grids of the accelerator. The design of the ITER HNB prototype, MITICA, was based on the coupling of several codes starting from experimental inputs available at that time. Heat loads, in particular, were estimated by the 2D version of the code Monte Carlo particle tracing code EAMCC. In the last years, a 3D version of the same code was developed and the operation of negative ion sources for fusion increased the knowledge concerning those parameters which are fundamental to estimate the expected heat loads. In this work, calculations are performed by EAMCC3D and the role of different source and accelerator parameters, such as the negative ion temperature and the beam halo, is highlighted.

Development of a novel Ultra Performance Liquid Chromatography Tandem-Mass Spectrometry (UPLC-MS/MS) method to measure l-arginine metabolites in plasma

IntroductionArginine metabolism is involved in the regulation of several biological processes. Many liquid chromatography tandem-mass spectrometry methods for the determination of arginine and its metabolites have been developed but they are time consuming and imply long pre-analytical procedures. The purpose of this study was to develop a rapid method for the simultaneous determination of arginine, citrulline, ornithine, symmetric and asymmetric dimethylarginine and monomethylarginine in human plasma. Materials and methodsThe pre-analytical procedure consisted in a simple deproteinization. The chromatographic separation was performed using hydrophilic interaction liquid chromatography. Analytes detection was performed with a triple quadrupole equipped with electrospray ion source operating in positive ion mode. Mass spectrometry experiments were conducted in multiple reaction monitoring mode. Results and conclusionsRecovery ranged from 92.2 to 108.0%. The within-run imprecision and between-run imprecision ranged from 1.5 to 6.8 % and 3.8 to 11.9%, respectively.Carry over and matrix effect did not affect quantitative analysis. Extraction recovery was between 95 and 105 %. Stability after pre-analytical procedure was tested and all the metabolites were stable after 48 h at 4 °C.In conclusion, our novel method allow a rapid and easy determination of arginine and its metabolites both for research and clinical routine use.

Comparison of pulse-modulated and continuous operation modes of a radio-frequency inductive ion source

The paper describes an experimental study of the characteristics of a pulse-modulated radio-frequency (RF) discharge sustained at low pressures, typical of the operating modes of RF gridded ion sources. The motivation for the study is the question of whether the RF pulse-modulated mode can increase the efficiency of the ion source. The ion current values extracted from an RF inductive ion source operating in continuous and pulse-modulated modes were compared. The experimental data were also compared with the parameter calculations based on a 0D numerical model of the discharge. The measurements showed that the pulse-modulated operation mode of the RF ion source had a noticeable advantage when the power of the RF generator was 140 W or lower. However, as the generator power increased, the advantage was lost because the pulse-modulated operation mode, having a higher RF power instant value, entered the region of existence sooner than the continuous mode, where the ion production cost begins to grow with RF power.

Foundations of plasmas as ion sources

An overview of low temperature, partially magnetized ion sources is presented. This class of devices is broadly characterized by plasma densities below 1019 m−3, electron temperatures below 100 eV, and magnetic field strength tailored such that electrons are magnetized whereas ions are not. The overarching approach is pedagogical, targeting an audience that does not necessarily have an expertise in low temperature devices. A tutorial is presented on the basic physics of operation of common ion sources including an overview of standard methods for plasma generation and acceleration. Typical diagnostics and common uses of these plasma sources are also reviewed. Special attention is given to applications in plasma propulsion and materials processing. This class of ion sources is then discussed in the context of the current state of the field, key technical and scientific challenges, and future prospects.

Insights into the effect of hollow cathode with external injection of fast ions in a sputter-type negative ion source

In sputter-type negative ion sources, the negative ion currents and ionization efficiencies are very dependent upon the creation of a sputter crater and formation of an intense plasma glow. This effect has many similarities with the well-known phenomena of hollow cathode discharges (HCDs). This paper discusses the phenomenological model related to conventional HCDs, including modes with injection of external energetic particles. We propose that HCDs play a major role in sputter-type negative ion sources. In this study, we evaluate the phenomenology of a discharge with a hollow cathode and derive an analytical formula that defines the neutral particle density inside the cathode cavity and substantiates how the classic HCD occurs in sputter-type negative ion sources. The cathode pit geometry was revealed by optical microscopy. Volt–ampere characteristics were investigated in order to compare it to typical discharges with hollow cathodes. In sputter-type negative ion sources, known as SNICS, discharge characteristics and observed light glow inside the cathode pit after its formation were very similar to data published on HCDs. The HCD phenomenon explains how the cathode current increases by orders of magnitude after creation of the cathode pit. The HCD effect in SNICS and similar sputter sources compliments existing mechanisms of negative ion production, especially ion pair production close to the cathode surface due to low energy ionization based on the collision–radiation model. The wealth of information accumulated over the last century on HCDs can be used to describe and explain the phenomenology of physics and operation of sputter negative ion sources.

Langmuir Probes as a Tool to Investigate Plasma Uniformity in a Large Negative Ion Source

The Source for the Production of Ions of Deuterium Extracted from an RF plasma (SPIDER) experiment is the full-size test-bed of the negative ion sources of ITER neutral beams. It aims to extract and accelerate more than 350 A/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{2}$ </tex-math></inline-formula> of negative hydrogen ions from 1280 apertures, distributed over a surface of approximately 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{2}$ </tex-math></inline-formula> . To assess plasma uniformity, SPIDER is equipped with bi-dimensional arrays of Langmuir probes, covering the plasma grid (PG) and the bias plate (BP) plasma-facing surfaces. These sets of diagnostics are routinely used during the ion source operation and allow to investigate the plasma properties in the so-called source expansion and extraction region. The dependencies of plasma parameters on source operation parameters such as RF power, pressure, magnetic filter field, PG, and BP biases are reported and used to evaluate the uniformity of the plasma, showing the presence of plasma drifts due to the magnetic field. Finally, the correlation between plasma and beam uniformity is assessed.

Oral fluid as a new investigative matrix for the determination of organic gunshot residue exposure

In recent years, increased use of ammunition without lead and heavy metals was observed, leading to a growing interest in the detection of organic gunshot residues (OGSR) as evidence of firearms related crimes. The wide range of compounds belonging to the OGSR class hinders their mass spectrometric detection as different ionization techniques may be needed to obtain good results for all compounds.The purpose of this work was the development of a reliable analytical method by means of UHPLC-HRMS for the determination in oral fluid (OF) of the most common explosives and the most used stabilizers, arising from fire discharge and post-deflagration residues.For this purpose, SPE was used for OF clean-up before UHPLC-HRMS analysis. All target analytes were chromatographically separated by means of a Polar-C18 column. A chlorinated compound was added to the mobile phases in order to promote the formation of chloride adduct ions in the electrospray ion source operating in polarity switching to allow the best conditions for each analyte. The detection was conducted by means of a high-resolution mass spectrometer equipped with Orbitrap technology working in data dependent acquisition mode, in order to detect both the precursor ions and/or the most intense fragments for stabilizers.To verify its potential, the method was tested on real samples: a shooting session was performed in an open shooting range; the shooters fired from 2 to 20 rounds with a 9x21 caliber, thereafter OF was sampled. Samples were analyzed confirming that explosives may be detected in OF; the use of this matrix may be of great interest for investigative purposes as it is less affected by secondary transfer when compared to other commonly sampled matrices. The developed method could be a useful tool for law enforcement authorities for the detection of explosives in forensic potential scenarios, including biological matrices.

Corticoids identification in a lipolytic product promoted by two influencers

Two influencers have consulted for abscesses requiring surgery on the faces and thighs which began, respectively, one month and ten days following injections by a Russian cosmetologist, of the so-called “Light Fit”, a lipolytic product. The “Light Fit” is made in South Korea and is available on the internet market. It claims that the composition includes different mineral salts and natural extracts of chestnut and walnut with exception of any other products. This product is frequently used in Russia for its indirect lipolytic action based on the promotion of “rapid breakdown of excessive fat”. Following the surgery of the two patients, the microbiological examination of the specimens allowed the identification of an atypical mycobacterium. We reported here the investigation of the chemical composition of this lipolytic product, which have led to side effects for two internet influencers promoting it, using both high-resolution targeted and untargeted approach. A saddled sample of the “Light Fit” product was furnished by the two influencers. Plasma and urine samples of the two patients were collected during the medical consultation, several weeks following the last injection of the lipolytic product. A sample preparation based on liquid-liquid extraction using acetonitrile and methyl tert-butyl ether was performed for each sample. Subsequently, extracts were analyzed by targeted and untargeted screening using liquid chromatography hyphenated to high-resolution tandem mass spectrometry with electrospray as ion source operating in polarity switching mode and a Q-Exactive Focus® Orbitrap mass spectrometer. The qualitative analysis of the lipolytic injection product allowed identifying glucocorticoids including triamcinolone acetonide and dexamethasone. The other detected chemicals were theophylline, lidocaine and tramadol using both targeted and untargeted approach. The “Light Fit” product was determined to be a normo-osmolar solution. Regarding the biological samples, triamcinolone acetonide was detected as trace amounts in the plasma of the two influencers. Furthermore, paracetamol was detected in urine samples as it was administered to the patients during medical consultation. The qualitative analysis of the lipolytic injection product invalidated the claim of a strictly natural composition. It is nevertheless known that theophylline and lidocaine are widely used as lipolytic agents. A conclusion of the natural or synthetic origin of theophylline, an alkaloid found in tealeaves, cannot be drawn. The synthetic glucocorticoid triamcinolone acetonide detected in the product is known to be a local anti-inflammatory steroid. The detection of trace amounts of triamcinolone acetonide in the plasma of the two patients may be related to the half-life of the compounds, which is higher than 20 days (Shen et al. Ophtalmology 2010;117:2375–2371; Schweitzer et al. Neth J Med 2000;56:12–16). Furthermore, the skin lesions observed at the injection site may be related to the infection by the atypical mycobacterium, highly favored by the local injection of triamcinolone acetonide, which, like other glucocorticoids, decreases immune response to pathogens. This study confirmed the usefulness of high-resolution screening to qualitatively characterize these types of products, a needed step prior to quantification. These two cases highlight the health risk of buying products on the internet with a falsified claim, even for people who promote these products like these two influencers.

Novel method for determination of methoxphenidine and its main metabolite in biological samples

Methoxphenidine (MXP) is new psychoactive substance belonging to the group of dissociative anesthetics. It appeared on the black market in 2013, and MXP intoxications have been reported with at least three deaths since then. To understanding the mechanism of toxicity and effects of MXP, it is important to know its pharmacological properties (e.g. toxicity, activity on receptors and ADME) and metabolism which may be further exploited to study its mechanism of action in vivo. Metabolism of such compound may be useful not only in toxicological screenings, but together with pharmacokinetic and pharmacodynamic data it enhances the knowledge how these substances may affect the living organism. It is still very little information on the MXP and a method for analysis of biological samples (e.g. brain, liver, lungs and serum) remain to be developed. Standards of MXP, main metabolite norMXP and internal standard of deuterated MXP (MXP-d3) was prepared in-house and used as external calibrators. For determination of MXP and norMXP in biological samples, UHPLC-MS was used. Quantitative analyses were performed using LC system Dionex Ultimate 3000 (Thermo-Fisher, MA, USA) and the chromatographic separation was performed using Poroshell 120, Phenyl Hexyl (2.1 × 100 mm, 2.7 μm) column (Agilent, CA, USA). Mobile phases consisted of 0.1% formic acid and 10mM ammonium formate in 5% methanol in water (v/v) (A) and in 5% acetonitrile in methanol (v/v) (B) and were used at a flow rate of 0.4mL/min. The analytes were detected in multiple reaction monitoring (MRM) mode using QTRAP 6500+ (AB Sciex, MA, USA) with a Turbo V Ion source operating in positive electrospray (ESI + ) mode. Wistar rats given 20 mg/kg MXP were used as real samples. At 0; 0.5; 1; 2; 4; 8 and 24 hours after administration, samples of livers, lungs, brain and 2 mL of blood serum were collected from rats. There were 8 samples from each tissue at each time point. To extract analytes from these complex biological matrices, protein precipitation and salting-out liquid-liquid extraction (SALLE) were used. Due to the complex matrix, it was important to develop an extraction method with sufficient yield and low matrix effect. Liquid-liquid extraction, SALLE and protein precipitation were tested for each type of biological sample separately. These methods were selected on the basis of a previous study of structurally similar substances. Protein precipitation was chosen as the best extraction method for processing blood serum samples and SALLE was chosen for preparation of three other tissues. All validation parameters met the guidelines from the US Food and Drug Administration (FDA). 8 samples of 4 biological samples were analyzed in 7-time intervals. Based on these data, MXP and norMXP concentration curves were generated. A quantification and extraction method for the determination of MXP and the major metabolite norMXP in blood serum, brain, liver and lung samples from Wistar rats was developed and optimized. Pharmacokinetic profiles for MXP and norMXP in all 4 types of biological material used, were established. This work was a part of the research project supported by the Ministry of Health of the Czech Republic (grant No. NU21-04-00307) and also it was supported from the grants of Specific university research–grant No. A2_FCHI_2022_003 and A2_FPBT_2022_023.

An experimental laboratory reactor for quantitative kinetic studies of disinfection byproduct formation using membrane inlet mass spectrometry.

RationaleThe type and quantity of environmentally problematic disinfection byproducts (DBPs) produced during chlorination of water depend on the natural organic matter and organic contaminants that raw water contains, and on the operational conditions of the drinking water treatment process. There is a need for a fast and quantitative method that determines which DBPs are produced and monitors the chemical dynamics during a drinking water treatment.MethodsA small experimental chemical reactor (50 mL) was mounted directly onto the membrane inlet interface of a membrane inlet mass spectrometer (MIMS). In this setup, the membrane was the only separation between the reaction mixture in the chemical reactor and the open ion source of the mass spectrometer 2 cm away. Water samples to be chlorinated were placed in the reactor and the chlorination reaction was initiated by injection of hypochlorite. The formation of intermediates and products was monitored using either full‐scan mass spectra or selected ion monitoring of relevant ions.ResultsAn algorithm for analyte quantification was successfully developed for analysis of the complex mixtures of phenol (a model for waterborne organic compounds), chlorinated intermediates and trihalomethane products which simultaneously pass the membrane into the mass spectrometer. The algorithm is based upon the combined use of standard addition and an internal standard, and all analytes could be quantified at nanomolar concentrations corresponding to realistic water treatment conditions. Experiments carried out in the temperature range 15–60°C showed that the reaction dynamics change with operational parameters, for example in tap versus deionized water.ConclusionsWe have successfully shown that an experimental laboratory reactor directly interfaced with a MIMS can be used for quantitative monitoring of the chemical dynamics during a water treatment. This technique could provide rapid assistance in the optimization of operating parameters for minimizing DBP production.

Conceptual Design of Control System for the Prototype RF-Driven Negative Ion Source at ASIPP

To explore the generation and extraction of negative ions for neutral beam injection, a prototype radio-frequency (RF)–driven negative ion source is designed at the test facility, which is under construction at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). The control system provides beam pulse set up, remote supervision, plant control, timing synchronization, data management, and interlock and protection for the RF negative ion source. It plays an important role in negative ion source operation. The negative ion source prototype is currently in the development phase, involving more than 20 plant units. To match the requirements of control, data acquisition, and protection for different plant units, the plant control loop time is designed within the range of 10 μs to 100 ms, timing synchronization accuracy is 1 μs, the maximum sampling interval for data acquisition is 10 ms, the volume of data storage is tens of terabytes/year, and the interlock and protection response time is designed within the range of 10 μs to 100 ms. This paper describes the conceptual design of the control system for the prototype RF-driven negative ion source at the ASIPP, discusses the system requirements and the specifications for the control system, and shows the present status of system integration.

A cold electron-impact ion source driven by a photo-cathode – New opportunities for the delivery of radioactive molecular beams?

The thick-target ISOL (Isotope mass Separation OnLine) method provides beams of more than 1000 radionuclides of 74 elements. The method is well established for elements with sufficiently high volatility at ca. 2000 °C. To extract non-volatile elements the formation of a volatile molecule is required. While successful in some cases (e.g. carbon or boron), most of these elements are not yet available as ISOL beam. A variety of volatile carrier molecules has been proposed for all elements produced in the target material, but their probability of survival during the extraction and ionization process is often limited by the high temperatures required for isotope diffusion in the thick targets and for ion source operation. While cold target concepts have already been proposed, the normal mode of operation of the typically used Versatile Arc Discharge Ion Source (VADIS) with a hot cathode is not well suited. Here, we report about first measurements with an electron-impact ion source operated at ambient temperature using electrons that were liberated via the photo-electric effect from a copper cathode.

Statistical analysis of operational data of the GTS-LHC ion source

The GTS-LHC ECR ion source delivers ion species for the physics programme of the CERN accelerator complex. Stability and reproducibility are key parameters for a successful operation. Therefore the source requires regularly intervention by an expert. The integrated functionality of data logging in the control system of the CERN accelerator complex allows to store all relevant control values and beam properties for the different machines. For the years 2015, 2016 and 2018, the data for the lead ion operation of the GTS-LHC ion source were extracted from the logging and treated with various statistical methods to identify recurring patterns in the operational settings of the source. If such patterns exist, they may be used in the future for the control of the source by semi-automatic feedback loops. The main study performed was based on a cluster analysis using the Optigrid algorithm, which is well suited for problems with a high number of parameters. The algorithm and selected results considering some operational aspects and ideas on further studies are presented.

Towards the optimization of the Cs evaporation configuration for long pulse operation of negative ion sources

Negative ion sources for neutral beam injection rely on surface production of negative ions on a caesiated low work-function surface (plasma grid). To maintain the low work function in long pulses (one hour) and the desired source performance (extracted H-/D- ions and limited co-extracted electrons), Cs needs to be constantly delivered onto the plasma grid. The CsFlow3D code was applied to the RF driven negative ion source ELISE to simulate the evaporation and the plasma-assisted redistribution of Cs. The Cs flux stability is investigated for consecutive one hour plasma pulses and compared with experiments. The effect of different positions of the Cs oven for the case of ELISE equipped with two racetrack shaped RF drivers was investigated: a considerable increase of the Cs flux occurs when evaporating where the plasma is in contact with surfaces, as confirmed also by the back-tracking of the Cs particles reaching the PG. Additionally, an alternative evaporation method close to the plasma grid was designed with the help of CsFlow3D and tested in BATMAN Upgrade, with the aim of increasing the Cs flux onto the PG and achieve a better control of caesiation in long pulses.