Proton beam commissioning of the SPIRAL2 Single Bunch Selector

Abstract

The single bunch selector of the SPIRAL2 accelerator allows reducing the bunch rate to the target of the Neutron For Science (NFS) facility in view of time of flight experiments. It involves two processes: a static dipole magnet deviates the beam on a 7.3 kW scraper, while the electric field of two high voltage travelling wave pulses maintains the selected bunch on axis at the required repetition rate. This original principle, named “inverted duty cycle”, was chosen to provide reasonable power requirement for the pulse generators, high rejection of the side bunches, and safe operation for the experimental target. This paper gives an overview of the whole system, recalls the main component design issues and performances and reports the successful commissioning results with the first 0.2 and 5 mA proton beams.

Design study of a single bunch selection method for neutron TOF experiment at RAON heavy ion accelerator

“…On the other hand, the beam energy of RAON is 10 keV/u, and the distance between the chopper and RFQ is approximately 4 m. Therefore, the length of the pulsed beam significantly increases throughout the transport line. The single bunch selector of GANIL uses compensation between the electric force from the high-voltage pulser and magnetic force from the dipole magnet [3,7]. The high voltage pulser must provide an electric kick to the beam bunch without affecting the neighboring bunches.…”

“…However, such a repetition time is too short for high-resolution neutron time-of-flight (TOF) experiments. To address this issue, several single bunch selection methods have been proposed [1][2][3][4][5][6][7]. The Soreq Applied Research Accelerator Facility (SARAF) proposed and tested a scheme based on a fast chopper [1,2].…”

“…When a specific beam bunch needs to be transported downstream, short electric pulses are applied to meander electrodes and cancel the magnetic force from the bending magnet. Recently, GANIL team reported the experiment results, and the rate of satellite bunch was under 10 −3 [3,7]. The Tokai Radioactive Accelerator Complex (TRIAC) tested a single bunch selection technique combining a multi-layer chopper and a double gap buncher (DGB).…”

Upgrade of the medium energy dump geometry for the SPIRAL2 single bunch selector

“…The corresponding bunch separation of ~11.3 ns being too short for experiments based on time-offlight measurement, a single bunch selection (SBS) system [2] is inserted in the medium energy beam transport (MEBT) to suppress most of the RFQ bunches and leave a lag ranging from 1 to 500 µs between the selected ones. The beam dump (SBS dump) is a key component of this system as it must stop more than 99% of the beam.…”

New trapezoid-shaped Frisch-grid ionization chamber for low-energy particle measurements

“…The emission time scale of isospindependent particles carries information about the isospin properties. Accelerator facilities such as SPIRAL2 at GANIL [1], SPES at LNLL [2], FAIR at GSI [3], FRIB at MSU [4], RIBF at RIKEN [5], FRIBS at LNS-Catania [6] and HIRFL at IMP [7], providing high-intensity radioactive beams, will cover a broad range of isospin (N /Z ) ratios; here N and Z are the neutron and atomic numbers, respectively. These measurements must be carried out with both good energy and angular resolution in order to investigate multi-particle correlations.…”