To simulate the burst irradiation environment of Europa, single crystals of NaCl were irradiated by pulsed intense relativistic electron beams (PIREBs) with a peak energy of 6 MeV, a current of −800 A, and a pulse width of 70 ns. After irradiation, the optical absorption of the samples was measured, and results indicated that the irradiation induced F-and F 2 -centers. The density of F-centers was estimated to be 8.9 × 10 16 cm −3 from 1 shot of PIREB irradiation with 6 MeV. The absorbed energy to form F-centers by PIREB was comparable but slightly higher than those induced by conventional direct current accelerators. The effect of pulsed heating, which should be taken into account for the detection of NaCl on Europa, is discussed.
We developed a new type of dc-to-pulse converter, called FRAC (Fringing-RF-field-Activated dc-to-pulse Converter) for low-energy ion beams electrostatically accelerated from an ion source. FRAC is based on a radio-frequency quadrupole (RFQ) linear trap technique and works in principle under ultrahigh vacuum conditions. Ions continuously injected into FRAC are decelerated by an alternating longitudinal electric field produced in a distorted radio frequency field around the edge region of RFQ rods. These ions accumulate in FRAC for a significantly long time. This edge effect appears most notably when the energy of incoming ions exceeds the injection barrier potential by less than a few eV and the energy spread is quite small. The ions stacked during the FRAC operation period are ejected as a high intensity pulsed beam. We investigated the performance of FRAC and the capability of some FRAC operation methods developed to enhance the dc-to-pulse conversion efficiency. The maximum conversion efficiencies achieved were 22% and 5.6% at FRAC operation frequencies of 10 and 1 Hz, respectively. The number of ions contained in an output beam pulse with a duration of 500 μs was in practice 1.6 × 109 ions/pulse at an injected dc beam intensity of 4.6 nA and an operation frequency of 1 Hz.
We developed a new-type of dc-to-pule converter, called FRAC (Fringing-Rf-field-Activated dc-topule Converter), for low-energy ion beams. This is based on a RFQ linear trap technique and works under ultra-high vacuum conditions. Ions continuously injected into FRAC are decelerated by an alternating longitudinal electric field produced in a distorted RF field around the edge region of RFQ rods. These ions accumulate in FRAC for a significantly long time. They are stacked during the FRAC operation period and consequently ejected as a high intensity pulsed beam. This edge effect appears most notably when the energy of incoming ions is below several eV at the injection barrier and the energy spread is considerably small. The peak intensity of the output pulsed beam achieved in practice was 112-times larger than the dc-beam intensity at the FRAC operation frequency of 1 Hz.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.