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Detailed Functions of Charged Particle Detectors in the SAMURAI Spectrometer#

The SAMURAI (Superconducting Analyzer for Multi-particles from RAdioIsotope beams) spectrometer is equipped with various charged particle detectors for precise measurement and analysis of particles produced in reactions with radioactive isotope beams. The main functions of each detector are as follows:

1. Beam Particle Tracking and Identification#

These detectors are located upstream of the target and are used to precisely measure the properties of the incident beam particles.

  • Beam Proportional Chamber (BPC)
  • Function: Mainly used for rigidity tagging of the beam at the F5 focal point, which is essential for determining the momentum of the incident beam.
  • Beam Drift Chambers 1 and 2 (BDC1, BDC2)
  • Function: Record the beam phase space information, enabling precise measurement of the two-dimensional position and direction of beam particles, and detailed reconstruction of the beam trajectory.
  • Ion Chamber for Beam (ICB)
  • Function: Measures the charge (Z) of the incident beam, helping to identify the particle species in the beam.

2. Reaction Product (Fragment) Analysis#

These detectors are located downstream of the target and are used to analyze the charged fragments produced in the reaction.

  • Forward Drift Chamber 1 (FDC1)
  • Function: Measures the scattering angle of the reaction fragments, which is important for understanding the reaction mechanism.
  • Forward Drift Chamber 2 (FDC2)
  • Function: Performs rigidity analysis of the reaction fragments. Combined with magnetic field information, this allows determination of the fragment momentum.
  • Ion Chamber for Fragments (ICF)
  • Function: Measures the charge (Z) of the fragments, aiding in fragment identification. Usually combined with other measurements (such as energy loss) to distinguish different nuclides.
  • Hodoscope for Fragments (HODF)
  • Function: Measures the time-of-flight (ToF) and charge (Z) of the fragments. ToF combined with path length gives the velocity, which can be used to determine mass if energy or momentum is known. Charge information also helps with particle identification.
  • Total Internal Reflection Cherenkov Detector (TIRC)
  • Function: Specially designed to measure the time-of-flight of fragments, enabling precise determination of their velocity. This is especially important for identifying high-energy fragments.
  • Total Energy Detector (TED)
  • Function: Measures the total energy of charged particles. This is typically used for heavy ions, helping to identify particles and determine their initial energy by measuring the total energy deposited in the detector.

3. Light Charged Particle (e.g., Proton) Analysis#

These detectors are dedicated to measuring light charged particles emitted in the reaction, such as protons from unbound state decay or knockout reactions.

  • Proton Drift Chambers 1 and 2 (PDC1, PDC2)
  • Function: Analyze the momentum of light charged particles such as protons. Usually placed after the analyzing magnet, they determine momentum by measuring the curvature of the particle trajectory in the magnetic field.
  • Hodoscope for Protons (HODP)
  • Function: Measures the time-of-flight and charge of protons. Similar to HODF, this helps determine the velocity of protons and aids in particle identification.

Sources:

https://ribf.riken.jp/SAMURAI/index.php?ChargedParticleDetector

https://www.nishina.riken.jp/ribf/SAMURAI/tecinfo.html

Last update: 2025-05-23
Created: 2025-05-23