Radioactive Ion Beam (7Be)
HIRA, operated in mass achromatic mode with important add-ons, has
been shown to deliver light radioactive ion beam of
excellent purity and moderate intensity using (p,n), (d,n)
type of reactions in inverse kinematics and in-flight technique. Primary
beams of stable, light nuclei from the 15 UD Pelletron accelerator
are used on hydrogenous target and the radioactive secondary particles are separated
in-flight and re-focused at a secondary target position using the existing recoil
mass spectrometer, HIRA, operated in a new ion-optical mode. To
satisfy the ion-optical requirement of a well defined beam spot-size,
polyethylene foil targets mounted on a rotary/linear motion device are
used. In the new optics, there is a momentum dispersed focal plane at
the center of the magnetic dipole. A slit system with in-vacuum transfer option is
installed at this focal plane, to selectively transmit secondary radioactive
particles of specific energy window to the final focal plane.
The large energy and momentum dispersion achieved till the centre of MD helps in
high selectivity of the secondary particles. The second half of HIRA cancels the
energy and momentum dispersion resulting in excellent secondary beam quality at the focal plane.
The four quadrupoles help in achieving good focus of selected particles at MD centre
and at the focal plane.
We have optimized the facility for production of 7Be beam
using the p(7Li,7Be)n reaction, with the
Beam energy: 16 - 22 MeV
Beam intensity: ~ 104 pps
Diameter of beam spot: 3 mm (FWHM) - depends on primary beam size
Purity of beam: > 99%
Energy spread: ± 0.5 MeV
Angular spread: ± 20 mrad
The focal plane chamber of HIRA acts as the scattering chamber for
reactions with secondary beam. It houses "triple axis movement" collimator
as well as the detector set-up. Since its commissioning, the facility has
been used to carry out a number of low energy nuclear reactions using
7Be secondary beam.