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Ultrathin (o 5 nm) self-supporting diamond-like carbon (DLC) foils are prepared by filtered cathodic vacuum arc (FCVA) deposition method as targets for laser-driven ion acceleration. The thickness and the morphology of these foils are characterized by atomic force microscope (AFM) and scanning electron microscope (SEM).

Electrons have been accelerated from ultra-thin diamond-like carbon (DLC) foils by an ultrahigh-intensity laser pulse. A distinct quasi-monoenergetic electron spectrum peaked at 30 MeV is observed at a target thickness as thin as 5 nm which is in contrast to the observations of wide spectral distributions for thicker targets. At the same time, a substantial drop in laser-accelerated ion energies is found. The experimental findings give first indication that relativistic electron sheets can be generated from ultra-thin foils which in future may be used to generate brilliant X-ray beams by the coherent reflection of a second laser.

Measurements of vacuum tightness and mechanical strength of diamond-like carbon (DLC) foils in the thickness range of 1–7 μg cm−2 have been performed with a purpose to evaluate suitability of foils as a gas barrier. Hydrogen and argon at pressures from 10−2 Pa to 20 kPa were used as test gases. The permeation rate specified as conductance density was found for the best sample of self-supporting foil to be around 1.5×10−3 l and 3.3×10−4 l s−1 cm−2 for H2 and Ar, respectively. Conductance density of the same foils mounted on the frames with a mesh along the apertures as support was about twice higher than that for the self-supporting ones, likely due to the mechanical imperfections of the foil assemblies of the first ones. On the other hand, mesh-supported foils as thin as 3 μg cm−2 and of 5 mm in diameter were withstanding the pressure of up to 18 kPa, while self-supporting foils of the same thickness ruptured at around 1.2 kPa. There was no observed relation between thickness of the foil and its mechanical properties and permeation rate. This suggests that rather tears and pinholes present in foils are the limiting factors of the foil–vacuum tightness and strength. Results obtained in the studies, presented in this work, demonstrate the ability of very thin DLC to isolate a high vacuum beam line from a gas cell in a variety of applications and ability to withstand the gas pressure relevant, in particular, to some gas-filled ionization chambers.

In our previous paper [V.Kh. Liechtenstein, N.V. Eremin, R. Golser, W. Kutschera, A.A. Paskhalov, A. Priller, P. Steier, Ch. Vockenhuber, S. Winkler, Nucl. Instr. and Meth. A 521 (2004) 203], first results on the evaluation of thin natural diamond-based detectors (NDDs) as an energy spectrometer for heavy ions in the energy range below 1 MeV/amu were presented. Although results were promising, the energy resolution of the detector was limited by an unexpected high-energy loss in the “dead layer” of the entrance window. In this paper, we report a significant improvement in the spectrometric properties of two highly selected and carefully treated NDDs with electrical contacts made of carbon and gold films as thin as about 10 and 20 μg/cm 2 , respectively, instead of much thicker aluminum contacts used before. In particular, for the NDD with thin carbon contact an energy resolution of 7.6% for 197 Au-ions at 20.6 MeV was obtained. The energy cut-off of the detectors was reduced to 0.9 and 1.5 MeV for carbon and gold contact, respectively. The measured data on energy cut-off for different projectiles are compared with calculations, which yields an estimate of the thickness of the dead layers. Long-term irradiation runs proved stable spectroscopic performance of the detectors, in spite of the inherent “pumping” effects and imperfections of pulse height distributions. Our data suggest that NDD-based spectrometers might outperform other detector types in applications where very fast detectors with high radiation tolerance are required.

Ultra-thin (⩽1 μg/cm2) diamond-like carbon (DLC) foils prepared by sputtering and supported by high-transmission meshes, have proven advantageous over standard carbon foils for timing and stripping of low-energy ions in many accelerator experiments. Specifically manufacture support mesh permits the use of much thinner, smoother and larger foils that can be accomplished without it. The main limitation of fine mesh as a mechanical support appears to be interaction of transmitting ions with the mesh that might affect both energy and angle distributions of primary ion beams under some irradiation conditions. As an alternative, collodion coatings can be used to support a foil during the mounting and handling, but later such coatings must be removed completely. In this work, process of removal of collodion coating from ultra-thin DLC foils by using ion beam bombardment in the energy range 6–15 MeV was investigated with the main emphasis given to determination of the minimal beam intensity sufficient to remove collodion, and to the measurement of the thickness of possible residual deposits. Removing of collodion was monitored online by measuring the energy of ions penetrating the foils. This was performed with high-resolution magnetic and electrostatic analyzers available at the beam lines of the Heidelberg MP-Tandem, and VERA-Tandem, respectively. In addition, preliminary results are presented of lifetime measurements for the collodion-reinforced very thin DLC foils in the thickness range of 0.6–5 μg/cm2. The results were obtained for a 20 MeV, 63Cu ion beam.

Diamond is an attractive alternative to silicon as a heavy ion detector owing to its exceptional radiation hardness and very fast timing. These remarkable properties of diamond allow one to expect that diamond detectors can outperform silicon detectors and ionization chambers for many applications, in particularly, for heavy ion accelerator mass spectrometry (AMS) measurements. However, most reported diamond particle detectors have been based on polycrystalline chemical-vapor-deposited diamond films and exhibited poor energy resolution (due to loss of charge carriers in the grain boundaries) resulting in limited applications, primarily for counting ions at hundreds of MeV/u. In this paper the evaluation of a thin single-crystal natural diamond detector as an energy spectrometer for 13C, 180Hf, and 238U ions in the energy range from 12 to 38 MeV is presented. The influence of “priming” and “polarization” effects is discussed. Initial measurements of energy resolution, stability and radiation hardness of the natural diamond detector have demonstrated its suitability for heavy ion AMS, in spite of some technical problems to be solved.

Thin and stable diamond-like carbon (DLC) foils, which were fabricated at the Kurchatov Institute by sputter deposition, have proved recently to be advantageous for stripping and secondary electron timing of high energy heavy ions in a number of accelerator experiments. This resulted in expanding applications of these DLC foils which necessitated further development efforts directed toward the following applications of DLC targetry: (i) thin stripper foils for lower energy tandem accelerators, (ii) enlarged (up to 66 mm. in diameter) stop foils for improved time-of-flight elastic recoil detection ion beam analysis, and (iii) ultra-thin (about 0.6 mug/cm(2)) DLC foils for some fundamental and applied physics experiments. Along with the fabrication of thin DLC stripper foils for tandem accelerators, much thicker (up to 200 mug/cm(2)) foils for post-stripping of heavy-ion beams in higher energy linacs, are within reach.

Thin diamond-like carbon (DLC) foils were tested as stripping targets for molecular structure studies using the Coulomb explosion imaging method. The multiple scattering of MeV atomic and molecular ion beams penetrating DLC foils was measured and compared to Formvar foils which have been used in CEI setups so far. The DLC targets were found to be of similar thickness (0.7–0.9 μg/cm2) as the Formvar foils but of higher efficiency for CEI measurements as they exhibit less pinholes. Other advantages of DLC foils are: smaller linear thickness due to their higher density, higher homogeneity and better control of the production process. The production of targets with even smaller thicknesses is anticipated.

The sputter preparation technique for thin diamond-like carbon (DLC) foils, advantageously used for ion-beam stripping and timing in accelerator experiments, has been optimized to improve the quality and the performance of the foils. Irradiation lifetimes of 5 μg/cm2 DLC foils prepared by this technique have been compared with those for foils of approximately the same thickness, prepared by laser plasma ablation and for ethylene cracked foils when bombarded by 11 MeV Cu− - and Au−-ion beams of ∼1 μA beam current at the Heidelberg MP-tandem. Standard carbon arc-evaporated foils were used as references. In these experiments, DLC stripper foils appeared to have a mean lifetime approximately two times longer than ethylene-cracked foils regardless of ion species, and compared favorably with foils prepared by laser ablation method. All these foils lasted at least, 10 times longer than standard carbon foils, when irradiated in the MP terminal. Approximately, the same improvement factor was confirmed with 3 μg/cm2 DLC stripper foils irradiated with 2.3 MeV Ni-beams at the Pelletron accelerator in Lund. Unlike standard carbon foils, most of the advanced lifetime foils exhibited thinning during long irradiation, under clean vacuum. This suggests that sputtering of the foil by the heavy-ion beam might be a dominant process, responsible for the observed failure of these long-lived strippers. Along with specifically corrugated self-supporting DLC beam strippers, we succeeded in the fabrication of very smooth and ultra thin (∼0.5 μg/cm2) DLC foils, mounted on grids and used as start foils for the ToF spectrometers applied in ion beam analysis.

The determinants of resolution of a time-of-flight spectrometer for medium energy ion beam analysis have been identified and analyzed. The primary determinants are uncertainty of ion path length, kinematic dispersion from the finite detector solid angle, straggling in the start foil and variability of the start foil thickness. The first three of these have been considered in previous studies of time-of-flight spectrometer resolution, but foil non-uniformity has not been examined in detail. Using backscattering analysis and atomic force microscopy, we have measured the thickness and roughness of carbon start foils and found them to be larger than suggested by their nominal specifications. As a result, energy uncertainty introduced by foil non-uniformity has been found to be a critical factor in determining resolution. Using measured values of foil parameters and known geometric characteristics of our spectrometer, Monte Carlo simulations of backscattering spectra of SiO 2 thin films on Si substrates have been computed and found to reproduce well the experimentally observed system resolution of 1350 eV for 104 keV He. Additional simulations show that spectrometer design changes could reduce this value to about 1 keV at which point it is, for all practical purposes, optimum.

Thin diamond-like carbon (DLC) foils in the thickness range of 0.6–15 μg/cm2 were produced and evaluated as heavy-ion strippers for tandem accelerators and as secondary-electron emitters for time-of-flight (TOF) spectrometers. The foils were produced by DC glow discharge sputter deposition of pure carbon with condensation of DLC films onto glass slides coated with a release agent. Irradiation lifetimes of 3 μg/cm2 DLC foils made by this technique were compared with lifetimes of standard vapor deposited carbon foils when bombarded with 14 MeV 197Au− ions at the terminal of the BNL MP7 Tandem Accelerator. Preliminary measurements have indicated that DLC strippers outlast the standard foils by a factor of at least three. The high tensile strength of DLC foils allowed reducing of the minimal thickness of start foil, for TOF spectrometer down to ≈ 0.6 μg/cm2, resulting in considerably improved energy resolution, due to lower ion energy straggling in the foil. Along with initially used special DC sputter deposition system, a commercially available diode RF sputtering technique was investigated as candidate method for large-scale production of DLC foils.

We have determined exit charge states and energy losses of slow, highly charged gold ions after transmission of thin (7 ± 3 nm) diamond like carbon foils. Average charge states of up to 37+ were observed for Th80+ at 8.2 keV/u (0.57 vBohr). The final charge state is populated through re-arrangement processes after the projectile has left the foil. High final charge states indicate that none of the M-shell vacancies in Th80+ could be filled inside the foil. The increase of the average exit charge state as a function of M-shell vacancies is a sign of strongly enhanced X-ray fluorescent yields for hollow atom decay in vacuum.

We report on the acceleration of ion beams from ultrathin diamondlike carbon foils of thickness 50, 30, and 10 nm irradiated by ultrahigh contrast laser pulses at intensities of $\ensuremath{\sim}7\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }\text{ }\mathrm{W}/{\mathrm{cm}}^{2}$. An unprecedented maximum energy of 185 MeV ($15\text{ }\text{ }\mathrm{MeV}/\mathrm{u}$) for fully ionized carbon atoms is observed at the optimum thickness of 30 nm. The enhanced acceleration is attributed to self-induced transparency, leading to strong volumetric heating of the classically overdense electron population in the bulk of the target. Our experimental results are supported by both particle-in-cell (PIC) simulations and an analytical model.

Compared to former laser ion acceleration schemes like target normal sheath acceleration (TNSA) [1], the laser acceleration from ultra-thin diamond-like carbon (DLC) foils is more efficient and for the high-power short-pulse laser ATLAS proton energies up to 100 MeV are expected [2]. Also for the generation of very dense relativistic electron bunches the use of ultra-thin diamond foils leads to much better results [3] than for laser bubble acceleration [4]. By reflection of coherent electromagnetic fields from these relativistic electron bunches it seems possible to generate brilliant, intense X-ray beams [5]. In the longer term we plan to use the laser-driven ion beams for cancer therapy and the X-ray beams in medical diagnostics.We describe the present status and the expected beam properties for the upgraded ATLAS laser at MPQ (Garching) and the setup of our medical beam line.

In previous experiments, diamond-like carbon (DLC) foils which are being produced at Kurchatov Institute, have proven well suited as long-lived stripper foils for high-energy heavy-ion tandem accelerators and ultra-thin secondary-electron (SE) emitting foils for TOF spectrometers. This paper presents the recent advances in DLC targetry with main emphasis given to development and applications of ultra thin foils (maximum diameter up to 70 mm) with high uniformity and minimal possible effective thickness, the latter has been evaluated by measurements of both energy loss and angular scattering of heavy ions transmitting through the foils. Comparative lifetimes of DLC stripper foils irradiated with high intensity (150 μA) He + beams at 2 MeV are reported, which demonstrate the favorable use of DLC foils as supplemental strippers at RFQ linacs. In conclusion, the attractive results of application of ultra-thin DLC foils to TOF detectors for heavy ion AMS as well as to compact tandem accelerators are presented.