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A spectrometer on chemical vapour deposition-diamond basis for the measurement of the charge-state distribution of heavy ions in a laser-generated plasma
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View: Figures


Image of FIG. 1.
FIG. 1.

Relative error (1σ) in the integrals of the measured signals from bunch to bunch, as a function of the number of ions impinging on a polycrystalline diamond detector per bunch, computed with a Monte-Carlo simulation. From about 100 particles per bunch on each detector, this error due to signal fluctuations becomes smaller than 5%, which is below the systematic experimental error bars.

Image of FIG. 2.
FIG. 2.

Z6 beamline within the UNILAC accelerator at GSI in the ion optical program MIRKO, with the transverse envelopes of the beam in x and y. The parameters of the beam and of the quadrupole and dipole magnets were tuned in order to optimize the size and position of the focal spots of the beam on the detector, for each charge state.

Image of FIG. 3.
FIG. 3.

Left: Metallization pattern of each diamond detector, composed of three electrodes on the front and one on the rear side. Right: one metallized diamond sample. The subdivision into three sectors makes it possible to further reduce the capacitance, resulting in a detector time constant of 4.5 ns when combined with 50 Ω broadband amplifiers.

Image of FIG. 4.
FIG. 4.

Left: one single detector ready for use. Right: positionment of the five detectors on a three-rail system, approximately 13 mm from one another in the transversal direction.

Image of FIG. 5.
FIG. 5.

Experimental setup for the testing of the spectrometer. Laser beams from both laser systems are simultaneously focused with a spot size of 1 mm on the target. The ion beam diameter is reduced to 500 μm by a pinhole. Following their interaction with the plasma, the ions bunches reach the spectrometer after a 12 m TOF distance, where the different charge states are spatially separated by a magnetic dipole.

Image of FIG. 6.
FIG. 6.

Compilation of the measured charge state distributions for 8 different experiments in a carbon plasma generated using a 100 μg/cm2 target foil. Circles show the proportions of the charge states 16+ to 20+ during the experiment, while the dotted lines represent the charge state reference proportions as measured in the solid foil. For clarity purposes, only a few error bars are shown. The temporal pulse profiles of the nhelix and Phelix lasers are also represented. From 0 ns the laser beams interact with the target and the plasma is created. A clear variation of the charge-state distribution due to the plasma formation and evolution can be seen from the start of the laser irradiation.

Image of FIG. 7.
FIG. 7.

Measured relative energy loss of from 8 different experiments in a plasma created using graphite target foils with a mass density of 100 μg/cm2. An energy loss of 100% corresponds to the solid foil. The temporal pulse profile of both lasers is shown at the bottom of the picture, and the temporal evolution of the normalized line density, characterizing the plasma expansion, is also plotted. For positive times the lasers heat the target to the plasma state. The increase in energy loss resulting from the increase in the free electron density as well as the subsequent decrease linked to the lowering of the line density of the plasma target can be observed.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: A spectrometer on chemical vapour deposition-diamond basis for the measurement of the charge-state distribution of heavy ions in a laser-generated plasma