Abstract
A position-sensitive twin Frisch-grid ionization chamber has been constructed for future photofission experiments using nearly monochromatic, linearly polarized gamma-ray beams. By exchanging the anode plates in the standard ionization chamber on both sides by an array of grid- and strip-anodes, which are rotated by 90° relative to each other and read out by means of resistive charge division, a position sensitivity is achieved that allows the azimuthal fragment emission angle and hence the fission axis orientation to be determined. The performance of this gaseous detector has been studied using the well-known 252Cf spontaneous fission process. The fission axis orientation could be determined relative to an arbitrary axis in space with a resolution better than 7° FWHM. Measured pre-neutron mass and total kinetic energy distributions are consistent with literature, which ensures that the mass and energy resolution for fission fragments is not affected by the position-sensitive structure.
Highlights
Twin Frisch-grid ionization chambers (FGIC) [1] for the study of fission-fragment properties have been established as accurate and reliable detectors in the last decades
By exchanging the anode plates in the standard chamber on both sides by an array of grid- and strip-anodes, which are rotated by 90◦ relative to each other and read out by means of resistive charge division [4], a position sensitivity is achieved that allows the azimuthal fragment emission angle to be determined, too
This manuscript reports on the investigation of a newly constructed position-sensitive twin FGIC chamber for future photofission experiments that may be used with nearly monochromatic, fully polarized gamma-ray beams from the HIγS facility at TUNL and ELI-NP
Summary
Twin Frisch-grid ionization chambers (FGIC) [1] for the study of fission-fragment properties have been established as accurate and reliable detectors in the last decades. By exchanging the anode plates in the standard chamber on both sides by an array of grid- and strip-anodes, which are rotated by 90◦ relative to each other and read out by means of resistive charge division [4], a position sensitivity is achieved that allows the azimuthal fragment emission angle to be determined, too. This manuscript reports on the investigation of a newly constructed position-sensitive twin FGIC chamber for future photofission experiments that may be used with nearly monochromatic, fully polarized gamma-ray beams from the HIγS facility at TUNL and ELI-NP. Since polarized photons are expected to yield strong azimuthal asymmetries in the fission fragment distribution, linked to the multipole character of the relevant excitations (see Ref. [5] for an example using polarized bremsstrahlung), the measurement of the azimuthal angle will allow us to gain in-
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