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Instrumental developments

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  • Involved people : L. Adoui, A. Cassimi, J.-Y. Chesnel, A. Domaracka, B. A. Huber, A. Méry, J.-C. Poully, J. Rangama, P. Rousseau, V. Vizcaino (permanent researchers) ; M. Abdelmouleh, R. Delaunay, S. Indrajith, M. Lalande, M. Liu, A. P. Mika, C. Nicolafrancesco, L. Schwob, N. Sens (PhD students) ; V. Toivanen, M. Ryzska (postdoc)

Unique tools to investigate systems of increasing complexity have been developped by the AMA team within the last 5 years. The developments of the FRAPA-MAGIC, PIBALE, and FISIC-selector devices are presented in the following subsections.

- PIBALE (Plateforme d’Irradiation de Biomolécules et d’Agrégats Libres ou Environnés, ANR Blanc) led by A. Méry (since 2013) :

The PIBALE set-up is devoted to the study of ion-ion collisions between very low energy biomolecular species and keV atomic ions in a crossed beam configuration. The biomolecular target is produced by an electrospray ion source (ESI) and accumulated in a Paul trap to increase beam density before irradiation. Molecular ion bunches are then transferred to the interaction point at very low energy (15 eV typically). Following interaction with the keV atomic ion beam, the positively charged fragments are analyzed in a linear time of flight (TOF) mass spectrometer. This unique crossed beam configuration should has been designed for coincidence detection of the produced fragments.
The very first experimental results have been obtained in 2018 in the interaction between a 7 keV He+ ion beam and protonated leucine-enkephalin [1]. After irradiation of such a model pentapeptide, several fragments corresponding to immonium ions of the tyrosine and phenylalanine amino acids have been identified (fig. 1).

Irradiation of a collagen model peptides by He+ ions has also been performed during the PhD thesis of Mathieu Lalande and have shown the existence of the intact ionised peptide.
Currently the whole setup is being optimized to run in a negative mode using multi-deprotonated peptides as a target (thesis of Min Liu). The negative operation mode should allow an efficient reduction of background events detection.

[1] L. Schwob et al., Rev. Sci. Instrum. 89, 043104 (2018)

- FRAPA & MAGIC (Formation and Reactivity of carbonaceous Aerosols in Planetary Atmospheres, ANR JCJC & MoleculAr Growth of carbon-containing molecular clusters induced by Ion Collisions, RIN Emergent MAGIC project) led by A. Domaracka

- FISIC-selector (Fast Ion – Slow Ion Collisions, ANR internationale) led by E. Lamour (Paris) :
Knowledge of the fundamental mechanisms at stake in fast ion – slow ion collision in atomic physics can provide a real breakthrough in the understanding of energy transfers in various plasmas such as inertial confinement fusion plasmas or stellar/interstellar plasmas. Measurements and reliable theoretical predictions are completely lacking for fast ion-slow ion collisions, a regime in which ion stopping power is maximum, and all the primary electronic processes (electron capture, loss and excitation) reach their optimum. It corresponds to a real “terra incognita” for atomic physics. The forthcoming availability of intense and stable ion beams of high optical quality on French Large Scale Accelerator Facilitiy opens new challenging opportunities to probe a variety of systems of prime importance for applications and basic research. Besides the stringent test of theories provided by these fundamental studies, we can anticipate that such kind of experiments will lead to valuable upstream information relevant for societal issues. With the Fit-FISIC (for First steps towards Fast Ion - Slow Ion Collisions) experimental program, we will explore not only the possibility to reach the pure three-body problem (bare ion on hydrogenic target) as a benchmark but also the role of additional electrons bounded to the target and/or to the projectile –one by one- to quantify several effects. The FISIC program which is mainly the investigation of a wide variety of ion-ion collision systems over a large range of ion charge states, is part of the S3 (Super Separator Spectrometer, an experimental facility for nuclear and atomic physics at SPIRAL2). In this context the AMA team, is in charge of the preparation of the low energy ion beam, the collision chamber and the detection after the collision. For the preparation of the low energy ion beam, a simple and compact electrostatic charge state purification system was simulated, built, and tested (see figure 1). Its large acceptance allows 100% transmission of the primary charge state within the experimental uncertainty for high emittance (≤60π mm mrad) low energy (≤30 qkeV) ion beams.

Figure 1 : Side view and schematic cut through the purification system. The cylindrical detectors are enclosed between Matsuda electrodes. The polarity of the detector electrodes for positive ion beams is indicated by plus and minus signs. The black beam resembles the primary ion beam which transits the structure at the effective radius. Beams with lower (capture, dark orange) or higher (ionization, light orange) charge state are sorted out by hitting the wall of the detector.

By utilizing two additional einzel lenses and Matsuda electrodes, we are able to deliver a narrow beam at different focal points. By altering the voltages on the deflector electrodes, an energy scan of the incoming monoenergetic beam can be carried out, effectively resulting in a scan of the charge state. Experiments were performed with different primary charge states at the ARIBE facility at GANIL. The resolution of the purifier was measured to be 10.5. Due to the non-Gaussian peak shape in the energy scans, separation is possible for higher charge states than predicted by the measured resolution. The measured results are in good qualitative agreement with our expectations according to numerical beam trajectory calculations. The achieved performance fully satisfies the requirements of the FISIC experiments for ion beams up to Ar18+.

Figure 2 : Cut view of the low energy product separation and detection system, shown in the detection mode for ionisation products.

The detection chamber has already been constructed and assembled and has to be tested. It consists on a stack of two microchannel plates coupled with a delay-line detector in order to detect the different charge states of the low energy ions (the target) after the collision.

Figure 3 : Schematic overview of the installation of the FISIC experiment at CryRing in experiment section YR09
As the perspective, we plan to perform the first campaign of experiments at CryRing by coupling the whole setup on the ring as shown on figure 3 xx until the availability of the SPIRAL 2 beam in the S3 area.