An RF beam sweeper for purifying in-flight produced secondary ion beams at ATLAS

Abstract

A new large-acceptance RF beam sweeper was designed, constructed and put into operation with the goal to remove the energy-degraded primary beams tails from radioactive beams (RIB) produced by inflight transfer or charge-exchange reactions. The system makes use of the velocity difference between the RIB beam of interest and the remaining tails of the primary beam after momentum selection by a bending magnet. The time-delayed primary beam components are deflected vertically out of the beam path by the RF sweeper, significantly reducing the stable beam background. Beam purity for the inflight radioactive ion beams as high as 96% has been achieved with this system.

In-flight production of an isomeric beam of $^{16}$N

“…In the present work, the gas cell was cooled to 90 K, filled to 1400 mbar with D 2 gas, and confined by HAVAR entrance and exit windows of thickness 1.9 mg/cm 2 . Downstream of the RAISOR focal plane and located throughout the transport beam line are two superconducting Radio-Frequency (RF) resonators and an RF Sweeper [33]. The RF resonators provide control of the longitudinal phase ellipse of the secondary beam in order to minimize either the energy-spread or time-spread of the beam through (re-)bunching.…”

“…[%] on an application of a transverse electric field oscillating at half the primary beam pulse frequency [33].…”

Reactions on the surface and inside of neutron stars

“…The beams were produced via the in-flight technique [9] by bombarding a hydrogen-or deuterium-filled production target with heaviermass stable ion beams. The radioactive beams are produced in the gas cell through reactions in inverse kinematics such as 1 o bending magnet and a RF-sweeper [10] located after the magnet. With these radioactive beams, nuclear reactions, which are relevant to the (α,p) process in type-I x-ray bursts and fusion reactions thought to be of importance in superbursts, have been investigated.…”

“…For experimental studies of these reactions it is easier to produce beams of 14 O, 17 F, 21 Na, 25 Al, 29 P, 33 Cl and 37 K, via inverse (p,n) or (d,n) reactions, when compared to beams of 18 Ne, 22 Mg, 26 Si, 30 S, 34 Ar which require two-particle transfer reactions, such as ( 3 He,n) or ( 12 C, 10 Be). For that reason many of the relevant (α,p) reactions mentioned above have been studied via the time-inverse (p,α) reaction using radioactive beams that are closer to the valley of stability.…”

“…Another advantage of the multi-sampling method is that the fusion measurement is self-normalizing, since the beam and the fusion events at the various energies are obtained from the same detector using the same number of incident particles without the need to change the energy or to use a monitor detector. The fusion cross sections for 10,12,13,14,15 C on 12 C converted into astrophysical S factors are shown by the solid points in Fig. 5 [26].…”