α-Particle Detection Systems Overview
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Questions and Answers

What gas was used in the detector for α-particle detection?

  • Argon
  • Isobutane (correct)
  • Nitrogen
  • Helium

    • What was the operating pressure of isobutane in the detector during the α-particle detection?

  • 4 Torr (correct)
  • 15 Torr
  • 1 Torr
  • 10 Torr

    • What is the position resolution observed for the α-particles?

  • 1.1 mm (correct)
  • 3.2 mm
  • 2.5 mm
  • 0.5 mm

    • Which two types of detectors are mentioned as part of the focal plane detector systems?

    <p>MWPCs and scintillation detectors</p> Signup and view all the answers

    What was the expected time resolution for the fission fragments?

    <p>1 ns</p> Signup and view all the answers

    What type of geometry does the HIRA focal plane detector use?

    <p>Five-electrode geometry</p> Signup and view all the answers

    What is the count rate that exceeded at forward angles during the experiments?

    <p>20 kHz</p> Signup and view all the answers

    What is the distance between adjacent wire frames in the HIRA focal plane detector?

    <p>3.2 mm</p> Signup and view all the answers

    What is the diameter of the wires used in the wire frames?

    <p>20 μm</p> Signup and view all the answers

    How far apart are the anode and cathode wires in the HYRA focal plane MWPC?

    <p>0.63 mm</p> Signup and view all the answers

    What material is the cylindrical housing for the electrode assembly made of?

    <p>Aluminum</p> Signup and view all the answers

    What gas is used in the operation of the MWPCs?

    <p>Isobutane</p> Signup and view all the answers

    What is the geometrical transmission efficiency of the MWPCs described?

    <p>92%</p> Signup and view all the answers

    What is the active area of the time-zero MWPC developed for measuring timing of fission fragments?

    <p>40 × 40 mm2</p> Signup and view all the answers

    What separates the adjacent wires in the multi-step design of the time-zero MWPC?

    <p>0.63 mm</p> Signup and view all the answers

    What type of detector follows the HYRA MWPC for energy measurement of the implanted ER?

    <p>Resistive anode detector</p> Signup and view all the answers

    What is the primary purpose of using isobutane gas in the detector system?

    <p>To reduce the straggling of low-energy heavy ions</p> Signup and view all the answers

    Which component of the detector system is responsible for reading the signal from the cathode?

    <p>Charge-sensitive preamplifier</p> Signup and view all the answers

    What was the applied bias voltage at the anode during detector operation?

    <p>+450 V</p> Signup and view all the answers

    What was the observed signal strength and rise time comparison of the new detector design versus MWPC?

    <p>300 mV strength with 3.5 ns rise time</p> Signup and view all the answers

    What is the intrinsic resolution time estimated for the time-zero MWPC?

    <p>400 ps</p> Signup and view all the answers

    What role does the large-area MWPC play in the experiments mentioned?

    <p>It operates as a stop detector</p> Signup and view all the answers

    Which radioactive sources were used to test the detector offline?

    <p>241 Am and 252 Cf</p> Signup and view all the answers

    At what pressure was the detector operated for alpha detection?

    <p>3 mbar</p> Signup and view all the answers

    Who is acknowledged for providing good quality beams?

    <p>Pelletron and LINAC group</p> Signup and view all the answers

    Which of the following collaborators does NOT belong to NPD-BARC?

    <p>B R Behera</p> Signup and view all the answers

    Which student is mentioned as part of the research team?

    <p>P Sharma</p> Signup and view all the answers

    What role did H J Wollersheim play in the research?

    <p>Provided technical support in detector instrumentation</p> Signup and view all the answers

    Which of the following is a method referenced in the materials?

    <p>Phys.Lett.B</p> Signup and view all the answers

    What is the primary focus of the acknowledgments section?

    <p>Collaborators and technical support</p> Signup and view all the answers

    Which collaborator is affiliated with Delhi University?

    <p>S K Mandal</p> Signup and view all the answers

    In which publication was this research acknowledged?

    <p>Pramana – J.Phys.</p> Signup and view all the answers

    What role does the time-zero detector play in time-of-flight (TOF) measurements?

    <p>It initiates timing signals for TOF calculations.</p> Signup and view all the answers

    What is a key feature of the hybrid telescopes used for heavy-ion detection?

    <p>They combine gas and silicon detectors for particle identification.</p> Signup and view all the answers

    How does the thickness of the E detector affect particle identification?

    <p>Thinner detectors allow for the detection of low-energy heavy ions.</p> Signup and view all the answers

    What is needed to adjust the active thickness of a gas detector in the hybrid telescope?

    <p>Adjusting the gas pressure within the detector.</p> Signup and view all the answers

    What is the purpose of using 1 m Mylar as the entrance foil in the ionization chamber?

    <p>To allow for the passage of certain ions while blocking others.</p> Signup and view all the answers

    What is the typical voltage used for the anode in the ionization chamber?

    <p>150 V</p> Signup and view all the answers

    What type of gain is experienced by the silicon detector in the hybrid telescope setup?

    <p>20 mV/MeV</p> Signup and view all the answers

    What is the purpose of having gold-plated tungsten wires in the wire frames of the ionization chamber?

    <p>To enhance electrical conductivity and prevent oxidation.</p> Signup and view all the answers

    Study Notes

    α-particle detection

    • The detector utilizes isobutane gas at a pressure of 4 Torr with an operating voltage of +540 V on the anode and −180 V on the cathode.
    • The detector consists of holes of 1 mm diameter placed 5.08 mm apart in a rectangular matrix.
    • Position resolution of ∼1.1 mm has been observed for α particles.
    • The detector system is used for studying the fission mass distribution and fission-gated neutron multiplicity for various systems.
    • The detector is operated at 1.5 Torr isobutane with an operating voltage of +400 V on the anode and −180 V on the cathode.
    • At forward angles the count rates exceed 20 kHz.
    • A timing resolution of ∼2.5 ns is observed for beam-like elastics.
    • Time resolutions are expected to be better (∼1 ns) for fission fragments due to higher amplitude pulse.

    HIRA and HYRA Focal Plane Detector Systems

    • HIRA (electromagnetic separator) and HYRA (gas-filled separator) are used to detect fusion evaporation products or evaporation residues (ER).
    • Multi-wire proportional chambers (MWPCs) are used at the focal plane of both spectrometers to detect ER's which focus the products and suppress primary beam-like particles.
    • HIRA focal plane detector has a five-electrode geometry.
    • HYRA focal plane MWPC uses four-electrode geometry by removing the last cathode.
    • Both MWPCs are operated with isobutane gas at pressures between 1 to 3 Torr.
    • The gas medium is isolated from the vacuum using a 0.5 μm Mylar entrance window, transparent to heavy recoils with A ∼200 and above.

    HYRA Focal Plane Detector System

    • A position-sensitive large-area silicon detector follows the HYRA MWPC.
    • The silicon detector provides the energy of the implanted ER.
    • The detectors can be stacked to create a larger detection area at the focal plane.
    • The position-sensitive large-area silicon detector can be either a strip detector or resistive anode detectors.
    • The Eurysis/Canberra resistive anode detectors are stacked to provide an active area of 15 × 5 cm2.

    Time-Zero MWPC

    • A transmission-type fast timing MWPC is used in combination with large-area position-sensitive MWPCs to obtain absolute timing of fission fragments and extract their mass-energy distributions.
    • The detector can be used as a trigger in multidetector setups for measuring neutrons and γ rays in coincidence with fission fragments.
    • The detector uses four electrodes made from wire frames, with a separation of 0.63 mm between adjacent wires.
    • The detector is operated with isobutane gas at 2–4 mbar pressure.
    • The anode is read using a fast timing amplifier and the cathode is read by a charge-sensitive preamplifier.
    • The detector was tested offline with radioactive sources 241Am and 252Cf.
    • The detector was operated with 3 mbar of isobutane gas pressure.
    • A bias voltage of +450 V and −180 V was applied at the anode and the cathode, respectively.
    • To evaluate the timing performance, TOF was set up between the time-zero and large-area MWPCs.
    • The large-area MWPC acts as a stop detector.
    • The distance between the two MWPCs is 15 cm.
    • A neutron detector is placed at a distance of 1 m from the source to collect coincident neutrons and γ rays.
    • The detector was used in an experiment to study the mass distribution for the 6,7Li + 238U system at 30–50 MeV energies.
    • The start MWPC was placed at a distance of 7.5 cm from the target on one of the GPSC arms followed by a large-area position-sensitive MWPC.
    • The second MWPC was placed on the other arm.
    • The time-zero detector provided a master trigger for all timing signals such as TOF for the two position-sensitive MWPCs and their position signals.
    • The electronic delay between the start and the stop detectors was determined using monoenergetic α particles from the 241Am source.

    Hybrid Telescopes for Heavy-Ion Detection

    • Hybrid telescopes, combining gas and silicon detectors, have been developed for heavy-ion detection and particle identification.
    • The detector system is used for studying the angular distributions of fission fragments and can be used to identify projectile-like fragments to study transfer reactions.
    • Silicon telescopes with very thin (10 μm) silicon detectors ( E) and thick (100–300 μm) (E) are used for particle identification.
    • The 10 μm-thick detectors are opaque to low-energy heavy ions such as fission fragments.
    • The telescope is composed of a gas ionization chamber, operating in the axial field geometry mode, which is followed by a silicon detector.
    • The ionization chamber (IC) is composed of three wire frames of 10 mm active diameter.
    • The wire frames consist of a cathode, a central anode frame and another cathode wire frame.
    • The distance between adjacent wire frames is 10 mm.
    • All wire frames are made from gold-plated tungsten wires of 20 μm diameter with 1 mm separation between adjacent wires.
    • The two cathodes are grounded whereas the anode operates in the ionization region at 150 V with a gas pressure of 100 mbar isobutane (2.5 μm Si equivalent).
    • The entrance foil is 1 μm Mylar (diameter 10 mm).
    • The anode is read using CSPA with a gain of 90 mV/MeV (Si equivalent) and the silicon detector has a CSPA of 20 mV/MeV gain.

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    Detector Instrumentation for Nuclear Fission Studies PDF

    Description

    This quiz explores the principles and configurations of α-particle detection systems, focusing on the use of isobutane gas and the performance characteristics of devices like HIRA and HYRA. It covers operational parameters, count rates, and timing resolutions essential for studying fission processes. Test your knowledge on the nuances of these detection technologies!

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