H. Kugler

Ion production by lasers using high-power densities in a near infrared region : Laser-Ion Sources

Results are presented of experiments on ion production from Ta targets using a short pulse (350-600 ps in focus) illumination with focal power densities exceeding 10 14 Wcm -2 at the wavelength of an iodine photodissociation laser (1.315 μm) and its harmonics. Strong evidence of the existence of tantalum ions with the charge state +45 near the target surface was obtained by X-ray spectroscopy methods. The particle diagnostics point to the existence of frozen high charge states ( 4 MeV) for the highest observed charge states. A tentative theoretical explanation of the observed anomalous charge state freezing phenomenon in the expanding plasma produced by a subnanosecond laser pulse is given.

The CERN laser–ion source

This paper describes the first results of a feasibility study undertaken at CERN to determine whether a laser-produced plasma can be used as a source of intense highly charged heavy ion beams. A variety of important measurements have been made, and the results are encouraging. Furthermore, a beam of highly charged light ions produced by the laser ion source has been accelerated successfully in a radio frequency quadrupole (RFQ) structure.

Laser ion source for heavy ion synchrotrons (invited)

A status overview of the development of laser ion sources suited to heavy ion synchrotrons is presented. The results of experimental and theoretical studies, recently obtained at a number of laboratories, for laser-produced highly charged heavy ions are summarized for plasmas heated by long wavelength lasers. Design of a powerful repetition rate CO2 laser, target interaction chamber, and extraction system suited for reliable long term operation mode with real accelerators is discussed. Requirements for the final performance of the laser ion sources for ion beam injectors at the ITEP-Moscow and CERN accelerator facilities are given.

Laser ion source for heavy ion synchrotrons

A status overview of the development of laser ion sources suited to heavy ion synchrotrons is presented. The results of experimental and theoretical studies, recently obtained at a number of laboratories, for laser-produced highly charged heavy ions are summarized for plasmas heated by long wavelength lasers. Design of a powerful repetition rate CO2 laser, target interaction chamber, and extraction system suited for reliable long term operation mode with real accelerators is discussed. Requirements for the final performance of the laser ion sources for ion beam injectors at the ITEP-Moscow and CERN accelerator facilities are given.

Status of the CO2 laser ion source at CERN

A laser ion source using a CO2 laser focused onto a solid target is under study at CERN for the production of high currents of highly charged heavy ions, for possible use in the preinjector for the large hadron collider. A new expansion and extraction layout was installed in this test facility, improving the alignment and making the target to extraction distance more flexible. A two solenoid beam transport system was studied for providing the matching of the beam to a radio-frequency quadrupole. An electrostatic beam transport using gridded electrostatic lenses was designed and constructed as an alternative to a magnetic system. Results show an increased overall current transmission for the electrostatic case. Investigation of the laser parameters required for the production of 1.4×1010 Pb25+ ions in a 5 μs pulse, has been performed using the TIR-1 laser facility at power densities up to 1014 W cm−2 for a focal spot size of 65 μm. The results of the latest scaling are presented.A laser ion source using a CO2 laser focused onto a solid target is under study at CERN for the production of high currents of highly charged heavy ions, for possible use in the preinjector for the large hadron collider. A new expansion and extraction layout was installed in this test facility, improving the alignment and making the target to extraction distance more flexible. A two solenoid beam transport system was studied for providing the matching of the beam to a radio-frequency quadrupole. An electrostatic beam transport using gridded electrostatic lenses was designed and constructed as an alternative to a magnetic system. Results show an increased overall current transmission for the electrostatic case. Investigation of the laser parameters required for the production of 1.4×1010 Pb25+ ions in a 5 μs pulse, has been performed using the TIR-1 laser facility at power densities up to 1014 W cm−2 for a focal spot size of 65 μm. The results of the latest scaling are presented.

Developments at the CERN laser ion source

The high current, high charge-state ion beam which can be extracted from a laser produced plasma is well suited, after initial acceleration, for injection into synchrotrons. At CERN, the production of a heavy ion beam using a CO2 laser ion source is studied. The latest results of experiments with a tantalum ion beam with charge states up to 23+ and accelerated by a radio frequency quadrupole from 6.9 to 100 keV/u, are presented along with simulations of the low energy beam transport. The ion yield at the desired charge state, the pulse to pulse stability of the ion beam, and the system reliability are all of major interest. Work is under way to replace the low repetition rate free-running laser oscillator by a master oscillator and power amplifier system. The master oscillator is operational and the first results of measurements of its beam quality and stability are presented.

Novel laser ion sources

Development in the field of high-power laser systems with repetition rates of several Hz and energies of few joules is highly active and opening, giving new possibilities for the design of laser ions sources. Preliminary investigations on the use of four different laser and target configurations are presented: (1) A small CO2 laser (100 mJ, 10.6 μm) focused onto a polyethylene target to produce C ions at 1 Hz repetition rate (CERN). (2) An excimer XeCl laser (6 J, 308 nm) focused onto solid targets (Frascati). (3) A femtosecond Ti: sapphire laser (250 mJ, 800 nm) directed onto a solid targets (Jena). (4) A picosecond Nd: yttrium–aluminum–garnet (0.3 J, 532 nm) focused into a dense medium of atomic clusters and onto solid targets (London). The preliminary experimental results and the most promising schemes will be discussed with respect to the scaling of the production of high numbers of highly charged ions. Different lasers are compared in terms of current density at 1 m distance for each charge state.

Laser ion source development at CERN

At CERN there is a demand for high currents of highly charged ions, presently for fixed target experiments at the SPS and in the future for the LHC project. The LHC, however, requires an intensity, which is an order of magnitude larger than the intensity presently achieved using an electron cyclotron resonance ion source. Laser ion sources have the potential to fulfill the LHC requirements, although a large number of technical problems have to be overcome. At CERN a project to investigate the feasibility of the application of laser ion sources was started in 1989 and a source capable of producing large currents of highly charged ions was constructed. The results of the investigations on this source, including charge state distributions, measurements of the energy distribution, measurements of ion currents, and emittance measurements will be presented. Furthermore a method to reduce the time‐dependent energy change is described.

High-Power CO2 Laser System with Repetition Rate Operation for High Current Multicharged Heavy Ion Generations

Experimental and numerical calculation results devoted to development of an optical system for an ion source based on a repetition rate CO2 laser are described. The laser chain consists of a master oscillator, gas absorber cells, and a four-pass amplifier. The optical system provides smooth laser pulses with variable duration and high spatial quality that ensures efficiency for plasma heating and ion generation. The parameters of the plasma ion component measured in the CERN laboratory are applied for a lead target illumination.

Laser ion source based on a 100 J/1 Hz CO2-laser system

The laser system is a key element of the laser ion source (LIS), significantly influencing source stability and reliability. A 100 J/1 Hz master oscillator-power amplifier CO2-laser system has been designed, built, and tested for a Pb25+ LIS, with the aim of producing the ion beam parameters compatible with an injection chain for the large hadron collider. The results obtained during commissioning of the laser at ITEP and CERN are presented. LIS parameters based on 100 J/1 Hz CO2-laser system and the use of such a source for the ITEP–TWAC project are discussed.