Thomson Parabola Spectrometer Research Articles

Evaluation of brightness of an intense pulsed ion beam by Thomson spectrometer

A method is proposed to evaluate the power brightness of an intense pulsed ion beam by using a Thomson parabola spectrometer (TPS). In the method, the time-dependent power brightness of each ion species can be determined independently from the density profile of ion tracks. The method is successfully utilized to evaluate the power brightness of ion beams produced in point pinch diode. The brightness of highly ionized carbons of 660 keV and oxygens of 880 keV, and singly ionized molecular ions of 400 keV, are evaluated independently. The total brightness is evaluated to be 3.2 GW/cm2/sr for highly ionized ions, and 1.9 GW/cm2/sr for molecular ions.

Stimulated acceleration and confinement of deuterons in focused discharges. II

For pt.I see ibid., vol.16, no.3, p.368-73, June 1988. Methods of increasing, by a factor greater than five, the neutron yield/short Y/sub n/ from D-D fusion reactions in a plasma focus (PF) enhance both the D/sup +/-ion acceleration to energy values E/sub d/>1-8 MeV and the ion confinement in the pinch region. Nuclear activation of C and N in the (doped) filling gas of the discharge chamber and of solid targets of C and BN bombarded by the ion beam in the direction of the electrode axis (0 degrees ) confirms earlier determination of the energy spectrum of the trapped ions (d phi /sub t//dE varies as phi /sub 0t/E/sup -m/) and of the ejected beam (d phi /sub b//dE varies as phi /sub 0b/E/sub d//sup -m/, m=2.5+or-0.5 for 0.1 MeV<or approximately=E<or approximately=3 MeV). A Thomson (parabola) spectrometer with nanosecond time resolution determines the time of emission t(E) of the beam at 0 degrees . Ion acceleration and trapping occur within the small (filamentary) elements of the magnetic fine structure of the pinch, which can be dispersed on a relatively large confinement volume after the pinch disintegration. It has been found that phi /sub t// phi /sub b/>or approximately=10-10/sup 3/ for E/sub d/>or approximately=1 MeV, depending on Y/sub n/.<<ETX>>

Investigation of a self-magnetically insulated Bθ-diode

An ion diode, where the insulating magnetic Bθ-field is produced by the diode current itself, has been investigated. Using a novel Thomson-parabola spectrometer that is capable of detecting up to 41 beam traces at a single shot and a carbon activation diagnostic the ion beam has been analyzed. The diode, operating at “KALIF”, delivers ion beams of 750 kA at energies of about 0·7 MeV. The focusing version of the diode shows a focus size of 1 cm2, the beam is neutralized to 98–99%, the proton content is about 60%.

Inductive postacceleration of charge- and current-neutralized, intense pulsed ion beam

An induction accelerator system has been successfully operated to postaccelerate an intense pulsed ion beam that is highly space-charge and current neutralized. An annular ion beam (energy 90 keV, current 5.7 kA, pulse width 750 nsec) extracted from an applied-${\mathrm{B}}_{\mathrm{r}}$ magnetically insulated diode is injected into the induction accelerator, where a short pulse (210 kV, 50 nsec) is applied. Measurements of beam energy by a Thomson-parabola spectrometer before and after the postacceleration have confirmed the increase in beam energy of ${\mathrm{H}}^{+}$ up to \ensuremath{\sim}240 keV after being postaccelerated.

Time-resolved measurement of energy and species of an intense pulsed ion beam

A time-resolvable Thomson-parabola spectrometer is developed employing a microchannel-plate image intensifier, which acts as a high-speed shutter (∼5 ns) by gating the applied voltage. Using such a spectrometer, we have achieved the measurement of temporal behavior of beam energy for various ion species of an intense pulsed ion beam extracted from a dual-current-feed magnetically insulated diode. The energy of protons is found to be in a good agreement with the diode voltage.

Velocity distributions of multi-ion species in an expanding plasma produced by a 1.05-μm laser

The fast-ion-velocity distributions for polyethylene plasmas produced by spherical laser illumination were observed by a Thomson parabola spectrometer. It has been found that the velocity distributions have undulations, sharp truncations, and broad shelf structure because of multi-ion-species effects. The spherical symmetric plasma expansions including multi-ion-species and two-electron temperature effects have been simulated by a newly developed computer code. The simulation results indicate that protons are accelerated near the front edge of carbon ions, and the maximum velocity is determined predominantly by the ions which run in the region ahead of the carbon-ion front. Consequently, the proton-expansion front has a structure slipped out from the carbon-ion front towards vacuum. Since such protons compensate the accelerating electric field, the maximum velocities of proton and carbon ions become higher and lower, respectively, than in the case of single-ion species. These expansion dynamics reduced by the simulation can explain well the detailed structure of the observed velocity distribution.