Recoil Filter Detector (RFD) 

• Principle of operation: RFD detects radioactive ions produced in a nuclear reaction. At the same time, gamma radiation emitted in this reaction is recorded (e.g. by a set  of germanium or scintillation detectors). The time-of-flight (TOF)  technique and the position determination  allows the velocity  vector of each ion to be reconstructed. In this way, it is possible to distinguish between products of various reactions such as: elastic and inelastic scattering, fission or  fusion-evaporation.

• Ion detection technique: ions  produced in the reaction hit a thin film generating on its surface a cloud of secondary electrons (SE). These electrons are accelerated by an electric  field and form a collimated beam that induces a light pulse in a scintillator located at the end of the accelerating system. The electrical signal at the photomultiplier (PM)  output is proportional to the energy loss of the ion (dE/dx).
   

• Selection of gamma rays from evaporation residua: in fusion reactions leading to the formation of heavy nuclides, often the main mechanism is the fission  of a massive compound nucleus. Selection of  TOF  corresponding to a well-defined recoil velocity characteristic for the evaporation residuum  allows filtering the spectrum of gamma rays dominated by the fission background.
   

• Minimization of the Doppler broadening of a gamma line: fast  radioactive recoils emit gamma rays  exhibiting  the Doppler shift causing  a significant broadening  of the spectral lines observed in the measured gamma spectra. The reconstruction of the velocity vector for each recoiling  nucleus allows for correction of the Doppler shift and, in effect, reduction of the line broadening.
   

• RFD in the  GALILEO setup at LNL Legnaro (2018), 
• RFD, AGATA and  PARIS gamma ray  spektrometers  at the  SPES radioactive ion beam facility at  LNL Legnaro

• Separation  of heavy evaporation residua  (ER) from  fission fragments  (FF) by  velocity vector reconstruction (simulation)