L. Celona

Results and interpretation of high frequency experiments at 28 GHz in ECR ion sources, future prospects

For the needs of future heavy ion accelerators, electron cyclotron resonance ion sources (ECRISs) should be able to deliver higher intensities and higher charge states. The 1e mA level intensity has already been reached by room temperature ECRIS for medium charge states of light elements (O6+, Ar8+). However, such level of intensity for heavy elements (like Pb27+ for CERN/LHC and GSI) requires more powerful ECRIS with higher electron densities (up to 1013 cm−3). On the other hand, an optimized magnetic configuration system has to be used in order to obtain the suitable compromise between the electron confinement and the high flux ion losses. Before the design of the future “high intensity ECRIS,” experiments have been performed with the superconducting SERSE source both at 18 and 28 GHz. After an overview of major results recently obtained, some scaling laws will be presented. Our results show that much larger intensities and charges can be reached with ECRIS. Then, we will show how the next ECRIS generat...

Operation of the SERSE superconducting electron cyclotron resonance ion source at 28 GHz

The SERSE source [P. Ludwig et al., Rev. Sci. Instrum. 69, 4082 (1998), and references therein] is a superconducting electron cyclotron resonance (ECR) ion source, operating at the Laboratori Nazionali del Sud in Catania since 1998; it is currently used as the main injector for the K-800 superconducting cyclotron. Its high magnetic field provides a high plasma confinement and large currents of highly charged ions, as compared to conventional sources. It can efficiently operate at the microwave frequency of 14 and 18 GHz [S. Gammino and G. Ciavola, Rev. Sci. Instrum. 71, 631 (2000); S. Gammino et al., ibid.70, 3577 (1999)] and has been used as a test bench for injection at 28 GHz. High-frequency operation is expected to create a higher plasma density, thus resulting in larger currents of multiply charged ions. In this article, we report the first operation of an ECR ion source at 28 GHz by using a gyrotron. The gyrotron itself and the waveguide line are described, along with the operational results (in xen...

Observations of the frequency tuning effect in the 14 GHz CAPRICE ion source

A set of measurements with the CAPRICE ion source at the GSI test bench has been carried out to investigate its behavior in terms of intensity and shape of the extracted beam when the microwaves generating the plasma sweep in a narrow range of frequency (+/-40 MHz) around the klystron center frequency (14.5 GHz). Remarkable variations have been observed depending on the source and the beamline operating parameters, confirming that a frequency dependent electromagnetic distribution is preserved even in the presence of plasma inside the source. Moreover, these observations confirm that the frequency tuning is a powerful method to optimize the electron cyclotron resonance ion source performances. A description of the experimental setup and of the obtained results is given in the following.

Review on high current 2.45 GHz electron cyclotron resonance sources (invited)

The suitable source for the production of intense beams for high power accelerators must obey to the request of high brightness, stability, and reliability. The 2.45 GHz off-resonance microwave discharge sources are the ideal device to generate the requested beams, as they produce multimilliampere beams of protons, deuterons, and monocharged ions, remaining stable for several weeks without maintenance. A description of different technical designs will be given, analyzing their strength, and weakness, with regard to the extraction system and low energy beam transport line, as the presence of beam halo is detrimental for the accelerator.

Production of low energy, high intensity metal ion beams by means of a laser ion source

The ECLISSE (ECR coupled to Laser Ion Source for charge State Enhancement) project started in 1999 with the aim to obtain an intense beam of highly charged ions (pulsed mode) by means of the coupling between a laser ion source (LIS) and an electron cyclotron resonance (ECR) ion source. The major points to be investigated appeared to be the coupling efficiency between the ion beam produced by the LIS and the ECR plasma, as well as the possibility to enhance the available charge state by an ECRIS with respect to the standard methods which are used to produce ion beams from solid samples (e.g., evaporation, sputtering). The calculations have confirmed that this concept may be effective, provided that the ion energy from the LIS is lower than a few hundred eV. The main features of the calculations will be shown, along with the results obtained in the off-line test facility at laser power densities below 1011 W/cm2.

Preliminary tests for the electron cyclotron resonance ion source coupled to a laser ion source for charge state enhancement experiment

At the Laboratori Nazionali del Sud we have designed a hybrid ion source, consisting of a laser ion source as first stage, which gives intense currents of electrons and of multiply charged ions, followed by an electron cyclotron resonance (ECR) ion source as a second stage, which should act as a charge state multiplier. The ECR ion source coupled to a laser ion source for charge state enhancement (ECLISSE) experiment has been funded by INFN and preliminary experiments have been carried out at IPPLM in Warsaw, in order to confirm the beneficial effects of the axial magnetic field of the ECR ion source on the extraction of the ions from the LIS, as foreseen by calculations. The description of the ECLISSE experiment and of the results of the preliminary tests will be reported.

18 GHz upgrading of the superconducting electron cyclotron resonance ion source SERSE

The superconducting electron cyclotron resonance ion source SERSE of INFN-Laboratori Nazionali del Sud has been recently upgraded with an 18 GHz generator which takes the place of the 14.5 GHz generator, used up to now. In order to further extend the validation of high B mode to higher frequency, some comparative tests have also been carried out, aimed at understanding the role of the magnetic field and frequency on the ion yield at higher levels than were ever done before. The results at the frequencies of 14.5 and 18 GHz are compared and the trend already observed elsewhere is here confirmed. Preliminary observations of the “two frequency heating” have contributed to increase further the currents of the highest charge states.The superconducting electron cyclotron resonance ion source SERSE of INFN-Laboratori Nazionali del Sud has been recently upgraded with an 18 GHz generator which takes the place of the 14.5 GHz generator, used up to now. In order to further extend the validation of high B mode to higher frequency, some comparative tests have also been carried out, aimed at understanding the role of the magnetic field and frequency on the ion yield at higher levels than were ever done before. The results at the frequencies of 14.5 and 18 GHz are compared and the trend already observed elsewhere is here confirmed. Preliminary observations of the “two frequency heating” have contributed to increase further the currents of the highest charge states.

Status and new developments of the high intensity electron cyclotron resonance source light ion continuous wave, and pulsed mode (invited)

The high intensity light ion source (SILHI) is the electron cyclotron resonance (ECR) source constructed and tested at CEA-Saclay. The first aim is to produce up to 100 mA cw proton beams at 95 keV for the proton injection high intensity (IPHI) beams [5 MeV radio frequency quadrupole (RFQ) and 10 MeV drift tube linac (DTL)]. This prototype is developed by a CEA–CNRS-IN2P3 collaboration for applications such as accelerator driven systems for nuclear waste transmutation, production of radioactive ion beams or secondary particles. SILHI is also used to study the production of deuteron and H− beams for the International Fusion Material Irradiation Facility and European spallation source projects, respectively. The present status of SILHI and the experiments planned for the near future in both cw and pulsed modes are presented in this article. 80 mA cw proton beams are now currently produced at 95 keV with a high availability (∼1 spark/day). The proton fraction is around 90% and the typical r–r′ rms normalized...

TRIPS: The high intensity proton source for the TRASCO project

The TRASCO project (trasmutazione scorie) is a R&D program whose goal is the design of an accelerator driving system for nuclear waste transmutation. The high current continuous wave proton linear accelerator will drive a subcritical system to transmutate nuclear wastes, while producing energy. The proton source TRIPS is a high intensity microwave source, which should be highly reliable and that should provide a minimum proton current of 50 mA with a r−r′ root mean square normalized emittance lower than 0.2 π mm mrad. A program of cooperation has been entered into with CEA-Saclay, where the IPHI project is in progress and the proton source SILHI has been designed and built using goals close to those of TRIPS. The construction of TRIPS is underway and the first beam is scheduled for the first half of 2000. The main features of this source and the results of the optics calculations are presented.

Improvement of beam emittance of the CEA high intensity proton source SILHI

The emittance of the intense proton beam extracted by the source SILHI at Commisariat a l’Energie Atomique (CEA)-Saclay is a key parameter for the design of the IPHI Project RFQ. This parameter has a relevant role even for the design of an intense proton source for the TRASCO project of Istituto Nazionale di Fisica Nucleare (INFN). The tests performed in the framework of CEA-INFN collaboration have been mainly devoted to a 75 mA beam emittance investigation injecting different gases in the beam line. The results show that the rms normalized emittance decreases up to a factor 3 while the beam losses induced by recombination are contained within 5%. Normalized emittance in r-r′ plane of about 0.1 π min mrad have been obtained using Ar and Kr.