S. Biri

On the characterisation of a Bragg spectrometer with X-rays from an ECR source

Narrow X-ray lines from helium-like argon emitted from a dedicated ECR source have been used to determine the response function of a Bragg crystal spectrometer equipped with large area spherically bent silicon (111) or quartz (10¯ crystals. The measured spectra are compared with simulated ones created by a ray-tracing code based on the expected theoretical crystal’s rocking curve and the geometry of the experimental set-up.

Production of multiply charged fullerene and carbon cluster beams by a 14.5 GHz ECR ion source

We report our first results on the study of normal and endohedral fullerene plasmas and beams produced by a 14.5 GHz electron cyclotron resonance (ECR) ion source (ECRIS). A mixed plasma of mainly N, N2, C, C2, and C60 was produced in the plasma chamber. Formation of caged nitrogens in the fullerene balls requires a careful, unusual tuning of the 14.5 GHz ECRIS. We deposited macroscopic quantities of the solid solution of N@C60 in C60 within the ECRIS. The N@C60/C60 ratio measured off-line using electron-spin-resonance spectroscopy may exceed typical values using conventional, non-ECR techniques. High intensities of C60Q+ ions (Q=1–5) were recorded in the extracted beam spectra. The highest measured C60+ beam current was 410 nA at 700 V extraction voltage. The method may be applied to produce carbon cluster beams from fullerenes, as well. We produced CnQ+ ions (n=2–15, Q=1,2) with intensities of 10–100 nA.

Imaging of ECR plasmas with a pinhole x-ray camera

X-ray plasma images were made at the 14.5 GHz electron cyclotron resonance ion source of ATOMKI using a pinhole and a high resolution CCD camera. This method has good spatial resolution as well as the capability of postprocessed energy filtering of the images. During the measurements low and high charge state Ar, Xe, and Fe plasmas were produced with simultaneous beam extraction. Full-size and selected region images were recorded and analyzed. Full-size x-ray images show the spatial positions of different sources of x rays (bremsstrahlung, characteristic lines of plasma and wall ions) within low-charged ECRIS plasmas. Images of selected plasma regions (extraction slit, magnet pole, magnet gap) offer a better understanding of the effect of important tuning parameters (bias disk voltage, gas mixing, microwave power, magnetic field strength, etc.) commonly used to produce highly charged plasmas and beams.

Production of highly charged ions in the RIKEN 18 GHz ECR ion source using an electrode in two modes

Abstract We placed an axially movable electrode into the plasma chamber of the 18 GHz RIKEN ECR ion source in order to produce higher intensity of multiply charged ions and to study how the electrode effects the highly charged ion (HCI) production. We found that the effect of the electrode strongly depends on the local plasma parameters, mainly on the electrode initial floating potential. At lower floating potential, we need to increase the plasma density by means of biasing the electrode and injecting electrons into the plasma. The electrode operates as an electron source (Electron Donor or ED mode). At higher floating potential, the electrode works by changing the plasma potential. The best result is obtained when the electrode remains at floating potential (Plasma Tuner or PT mode). These two modes were checked and successfully found both in the continuous and in the pulsed mode operation. In both (ED and PT) modes, we generated higher HCI currents than without the electrode. In the PT mode, we successfully obtained 300 eμA of Ar11+ at 15 kV extraction voltage.

Review on heavy ion radiotherapy facilities and related ion sources (invited)

Heavy ion radiotherapy awakens worldwide interest recently. The clinical results obtained by the Heavy Ion Medical Accelerator in Chiba at the National Institute of Radiological Sciences in Japan have clearly demonstrated the advantages of carbon ion radiotherapy. Presently, there are four facilities for heavy ion radiotherapy in operation, and several new facilities are under construction or being planned. The most common requests for ion sources are a long lifetime and good stability and reproducibility. Sufficient intensity has been achieved by electron cyclotron resonance ion sources at the present facilities.

Bio-Nano ECRIS: an electron cyclotron resonance ion source for new materials production.

We developed an electron cyclotron resonance ion source (ECRIS) for new materials production on nanoscale. Our main target is the endohedral fullerenes, which have potential in medical care, biotechnology, and nanotechnology. In particular, iron-encapsulated fullerene can be applied as a contrast material for magnetic resonance imaging or microwave heat therapy. Thus, our new ECRIS is named the Bio-Nano ECRIS. In this article, the recent progress of the development of the Bio-Nano ECRIS is reported: (i) iron ion beam production using induction heating oven and (ii) optimization of singly charged C(60) ion beam production.

Electron cyclotron resonance ion trap: A hybrid magnetic system with very high mirror ratio for highly charged ion production and trapping

In the Paul Scherrer Institute [PSI Switzerland] an experimental program was started to measure the ground state shift and width of pionic hydrogen. To calibrate the crystal spectrometer x-ray transitions in hydrogen-like heavy ions (e.g., Ar17+), produced by electron cyclotron resonance (ECR) ion sources, are necessary. In PSI a superconducting cyclotron trap magnet, originally developed for particle physics experiments, will be transformed into an ECR ion trap (ECRIT). The SC magnet can deliver more than 4 T magnetic fields with a mirror ratio of 2. A careful calculation showed this mirror ratio can be increased upto 10 and the trap can operate with frequencies between 5 and 20 GHz. To form a closed resonance zone an open structure NdFeB hexapole will be applied. The first tests will be performed at 6.4 GHz. Later higher frequencies and the two-frequency heating (6.4+10, 6.4+14.5, or 10+14.5 GHz) are planned to be applied to get enough quantity of H-like heavy ions. The ECRIT will operate at ground pote...

ECR plasma photographs as a plasma diagnostic

Low, medium or highly charged ions delivered by electron cyclotron resonance (ECR) ion sources all are produced in the ECR plasma. In order to study such plasmas, high-resolution visible light plasma photographs were taken at the ATOMKI ECR ion source. An 8 megapixel digital camera was used to photograph plasmas made from He, methane, N, O, Ne, Ar, Kr, Xe gases and from their mixtures. The analysis of the photo series gave many qualitative and some valuable physical information on the nature of ECR plasmas. A comparison was made between the plasma photos and computer simulations, and conclusions were drawn regarding the cold electron component of the plasma. The warm electron component of similar simulation was compared with x-ray photos emitted by plasma ions. While the simulations are in good agreement with the photos, a significant difference was found between the spatial distribution of the cold and warm electrons.

Influence of the biased electrode on the plasma potential in ECRIS

Dedicated experiments have been carried out at the Frankfurt 14 GHz electron cyclotron resonance ion source (ECRIS) by using a special double biased-electrode assembly, which consists of a conventional disk electrode and a separately biased ring electrode installed in front of it. In this assembly, the ring can be used to modulate the fluxes to the disk and allows a detailed study of the role of secondary electron fluxes in ECRIS operation. It was found that these fluxes contribute more than 50% to the total disk currents. However, blocking them did not result in a drop in the extracted ion currents. Instead, it was observed that, under certain operational conditions, the injection of secondary electrons results in a decrease in the extracted currents by up to 20%. Parallel to the double disk measurements, Langmuir probe measurements have been performed close to the position of Bmax. From the probe characteristics, plasma potentials were determined to be about +30 V at the conditions of the experiment. Ap...

The new ECR ion source of the ATOMKI: A tool to generate highly charged heavy ion plasma and beam

Abstract Between 1993 and 1996 a 14 GHz electron cyclotron resonance (ECR) ion source has been designed and built in the ATOMKI. The ion source is aimed for the production of highly charged heavy ion beams from a wide range of the elements. One of the most important planned applications in the near future is its usage for low energy ion-atom collisions. This ion source is the first ECR ion source in Hungary and in Middle-Eastern Europe as well. The first plasma was successfully generated in February 1996 and the first extracted beam is expected in the fall of the year. This paper briefly reviews the history and progress of the ECR program and shows the ECR ion source itself. The results of some indirect plasma measurements (X-ray spectra) are shown and discussed.