Development of a projectile charge state analyzer and 10 kV bipolar power supply for MeV energy ion - atom/molecule collision experiments

TL;DR

Addressing the need to resolve projectile charge states after MeV-energy ion–atom and ion–molecule collisions, the authors designed a parallel-plate CSA integrated with a recoil ion momentum spectrometer and built a remote, bipolar 10 kV power supply. They validated the CSA with SIMION simulations and experimental calibration using 1.0 MeV H+ beams, achieving charge-state separation up to at least C2+ within a 1 m CSA and up to ±10 kV operation. Collision investigations with Ar and N2 targets demonstrated ionization and capture channels, enabling recoil-ion yield ratios and detailed kinetic energy release distributions that align with prior data, thereby confirming the apparatus’ capability to probe transfer ionization and fragmentation pathways. The setup, with remote control and potential anti-coincidence capabilities, provides a robust platform for high-energy collision studies in accelerator laboratories.

Abstract

We have developed a post-collision projectile charge state analyzer (CSA) for detecting the charge state of the projectile ion following ion-atom/molecule collision. The design of the analyzer, based on electrostatic parallel plate deflector was simulated using SIMION ion optics package. We have also developed a 10 kV bipolar programmable power supply to bias the CSA electrodes. The CSA and the power supply, both, were tested in collision studies using MeV energy ion beam of proton and carbon ions at the 1.7 MV tandetron accelerator facility at IIT Kanpur.

Figures (16)

• Figure 1: Schematic of the projectile charge state analyzer. The mounting stubs S1 are fabricated from Delrin® and S2 from Teflon®. All other parts are fabricated from non-magnetic stainless steel. Detectors D1 and D2 are either CEMs or SBDs, chosen based on the energy of the incident ion beam and resolution of the time of flight spectrum. The FC and the detectors D1 and D2 are electrically isolated from the detector plate.
• Figure 2: 3D CAD assembly drawing of the CSA with rotatable detector assembly.
• Figure 3: CAD rendering of the rotatable detector assembly (left) and photograph of the detector assembly mounted in the CSA chamber (right). Vertical positioning of the apertures in beam alignment plate coincides with the centres of the CEMs and SBDs in the CEM plate and SBD plate respectively. The rotary enables rotation of the mounting SS disk to bring the detector plates in line with the incident beam after alignment is done using the beam aliggnment plate.
• Figure 4: SIMION simulation of the CSA for an incident carbon beam with an energy of 4.5 MeV. The beam is a mixture of C$^{2+}$, C$^{+}$ ions and C neutral atoms with identical kinetic energy. Tolerances at the entry and exit of Region I are denoted as t$_i$ and t$_f$, respectively. Under the influence of the electric field applied between the deflecting plates, the composite beam separates into its constituent charge/neutral species.
• Figure 5: Measured beam current in FC as a function of applied potential difference between the electrodes. Energy of the incident projectile beam is 1.0 MeV