Fission Studies with VAMOS++ and FALSTAFF spectrometers

by Indu Jangid, 1st year PhD student at GANIL

Historically, the experimental investigation of fission was focused on neutron-induced fission, in which flux of neutrons is sent to a stable heavy target where the fission process takes place. In this direct kinematics, because of the fission fragments’ low velocity, only the full identification of mass distribution of the fragments was possible.

In 1994, K.-H. Schmidt introduced a new technique, inverse kinematics, in which a heavy nuclei beam will be sent to a light target. In this manner, the fission process takes place in flight. In VAMOS at GANIL, inverse kinematics technique is using to access the nuclear charge information and high-resolution fragment mass. VAMOS is a large solid-angle, ray-tracing magnetic spectrometer that comprises one magnetic dipole, two magnetic quadruples, and a detection setup composed of 4 multiwires detectors and one ionization chamber. With the VAMOS++ magnetic spectrometer, only one fission fragment can be identified at a time. In experiment e826 (which took place in March 2022), the FALSTAFF spectrometer had used to detect the second fission fragment. FALSTAFF Spectrometer is a new setup based on low-pressure gaseous detectors and offers a new opportunity to identify fission fragments in terms of mass, nuclear charge and velocity vector. With the help of both spectrometers, both fission fragments can be measured simultaneously. In this experiment, a 238U beam was used as a projectile impinging into a Al and a Be target.

The objective of my thesis is: First do the data analysis for VAMOS++ spectrometer and determine the mass and charge state as well as the atomic number of fission fragments. Second, I will do the full characterization of the FALSTAFF spectrometer, and the determination of isotopic fission-fragment yields and the scission configuration of exotic minor actinides. In this seminar, I will present the Analysis of VAMOS Spectrometer, whatever I have done so far.