Position-sensitive Parallel Plate Avalanche Counter Research Articles

Parallel-plate avalanche counters for heavy-ion beam tracking: History and mysteries

Despite being an old detector concept, position-sensitive parallel-plate avalanche counters (PPACs) remain widely used today for heavy-ion position and timing measurements. In modern rare isotope beam facilities and large-acceptance fragment separators, PPACs are used to characterize beam properties (diagnostics), facilitate beam delivery (tuning), and provide event-by-event beam tracking for particle identification (PID). Most popular particle localization methods in PPAC detectors are based on strip electrodes electrically connected to resistive-chain circuits or delay lines. More exotic systems include optical readouts based on recording electroluminescence light with high-granularity photodetector arrays or high-resolution resistive anode electrodes. PPACs with conventional resistive-chain or delay-line readouts achieve typical position and time resolutions of below 1 mm (σ) and around 150 ps (σ), respectively. In addition, delay-line systems are capable of counting rates above several hundred kHz for beam areas of a few millimeters square, and around 1 MHz for larger beam sizes. Resistive-chain readouts have limited rates of a few tens of kHz. A review of the operation principles and performance of PPAC detectors is presented in this paper. We will discuss decades-long experience building and operating PPACs developed at the National Superconducting Cyclotron Laboratory, and then refined at the Facility for Rare Isotope Beams (FRIB), mostly focusing on the delay-line readout technique (DLPPAC). We will also discuss problems that arise due to electric discharges at high rates and briefly describe ongoing developments at FRIB. Published by the American Physical Society 2024

Fabrication and performance evaluation of parallel plate avalanche counters for RISP

We have fabricated and tested position-sensitive parallel plate avalanche counters (PPACs) for the Rare Isotope Science Project in Korea. These detectors have active areas of 10 cm × 10 cm with a stripped electrode structure. A delay line readout was employed to obtain the position information. Detector performance was tested with an 241Am alpha source. The detection efficiency, position, and time resolutions were studied with C3F8 gas pressures from 4 to 28 Torr and high voltages from 650 to 1100 V. Detection efficiency was greater than 99%. The position and time resolutions were measured to be 380 μm and 520 ps of full-width at half maximum (FWHM), respectively.

Development of Parallel Plate Avalanche Counter for heavy ion collision in radioactive ion beam

Abstract We have developed a position-sensitive Parallel Plate Avalanche Counter (PPAC) to detect the fission fragments and reconstruct the fission reaction plane in the experiment of studying nuclear equation of state (nEOS) by means of heavy ion collision (HIC). This experiment put forward high requirements for the performances of PPAC, such as the time resolution, efficiency and position resolution. According to these requirements we designed the PPAC with an active area of 240 mm × 280 mm working at low gas pressure. The results show that time resolution could be less than 300 ps. Position resolution is consistent with the theoretical calculation about 1.35 mm. Detection efficiency could be approaching 100% gradually with the voltage increasing in different gas pressures. The performances of PPAC have also been verified in beam experiment. Each set of anode wires can be accurately separated in the position spectrum. In the beam experiment, we also got the back-to-back correlation of fission fragments which is one of the direct signals characterizing binary decay.

The experimental set-up of the RIB in-flight facility EXOTIC

We describe the experimental set-up of the Radioactive Ion Beam (RIB) in-flight facility EXOTIC consisting of: (a) two position-sensitive Parallel Plate Avalanche Counters (PPACs), dedicated to the event-by-event tracking of the produced RIBs and to time of flight measurements and (b) the new high-granularity compact telescope array EXPADES (EXotic PArticle DEtection System), designed for nuclear physics and nuclear astrophysics experiments employing low-energy light RIBs. EXPADES consists of eight ΔE–Eres telescopes arranged in a cylindrical configuration around the target. Each telescope is made up of two Double Sided Silicon Strip Detectors (DSSSDs) with a thickness of 40/60μm and 300μm for the ΔE and Eres layer, respectively. Additionally, eight ionization chambers were constructed to be used as an alternative ΔE stage or, in conjunction with the entire DSSSD array, to build up more complex triple telescopes. New low-noise multi-channel charge-sensitive preamplifiers and spectroscopy amplifiers, associated with constant fraction discriminators, peak-and-hold and Time to Amplitude Converter circuits were developed for the electronic readout of the ΔE stage. Application Specific Integrated Circuit-based electronics was employed for the treatment of the Eres signals. An 8-channel, 12-bit multi-sampling 50MHz Analog to Digital Converter, a Trigger Supervisor Board for handling the trigger signals of the whole experimental set-up and an ad hoc data acquisition system were also developed. The performance of the PPACs, EXPADES and of the associated electronics was obtained offline with standard α calibration sources and in-beam by measuring the scattering process for the systems 17O+58Ni and 17O+208Pb at incident energies around their respective Coulomb barriers and, successively, during the first experimental runs with the RIBs of the EXOTIC facility.

Development of Parallel Plate Avalanche Counter (PPAC) for BigRIPS fragment separator

We have developed a position-sensitive Parallel Plate Avalanche Counter (PPAC), which has been used as a focal plane detector in the BigRIPS fragment separator and the subsequent RI-beam delivery lines at the RIKEN Nishina Center RI Beam Factory. The PPAC detector plays an important role not only in the tuning of the separator and delivery lines but also in the particle identification of rare isotope (RI) beams. The PPAC detector has a sensitive area of 240mm×150mm, and the position information is obtained by a delay-line readout method. Being called double PPAC, it is composed of two full PPACs, each measuring the particle locus in two dimensions. High detection efficiency has been made possible by the twofold measurement using the double PPAC detector. The sensitivity uniformity is also found to be excellent. The root-mean-square position resolution is measured to be 0.25mm using an α source, while the position linearity is as good as ±0.1mm for the detector size of 240mm. Characteristics, operating principles, specifications, performance and issues of the PPAC detector are presented, including its signal transmission system using optical fiber cables.

An Ion Beam Tracking System based on a Parallel Plate Avalanche Counter

A pair of twin position-sensitive parallel plate avalanche counters have been developed at the Australian National University as a tracking system to aid in the further rejection of unwanted beam particles from a 6.5 T super conducting solenoid separator named SOLEROO. Their function is to track and identify each beam particle passing through the detectors on an event-by-event basis. In-beam studies have been completed and the detectors are in successful operation, demonstrating the tracking capability. A high efficiency 512-pixelwide-angle silicon detector array will then be integrated with the tracking system for nuclear reactions studies of radioactive ions.

Potential and limitations of nucleon transfer experiments with radioactive beams at REX-ISOLDE

As a tool for studying the structure of nuclei far off stability the technique of gamma-ray spectroscopy after low-energy single-nucleon transfer reactions with radioactive nuclear beams in inverse kinematics was investigated. Modules of the MINIBALL germanium array and a thin position-sensitive parallel plate avalanche counter (PPAC) to be employed in future experiments at REX-ISOLDE were used in a test experiment performed with a stable 36S beam on deuteron and 9Be targets. It is demonstrated that the Doppler broadening of gamma lines detected by the MINIBALL modules is considerably reduced by exploiting their segmentation, and that for beam intensities up to 10^6 particles/s the PPAC positioned around zero degrees with respect to the beam axis allows not only to significantly reduce the gamma background by requiring coincidences with the transfer products but also to control the beam and its intensity by single particle counting. The predicted large neutron pickup cross sections of neutron-rich light nuclei on 2H and 9Be targets at REX-ISOLDE energies of 2.2 MeV A are confirmed.

Light charged particle release in252Cf spontaneous fission: Tripartition versus fragment de-excitation

Double-differential emission probabilities P (E, θ) in angle θ and energy E of protons, tritons, and α-particles were measured in the case of spontaneous fission of252Cf. A detector system consisting of position-sensitive parallel-plate avalanche counters (PPAC) and ΔE−E-telescopes allowed a coincidence measurement of fission fragments (FF) and light charged particles (LCP) in the whole region from 0 deg. to 180 deg. with respect to the light-fragment direction. Previous results for α-particle emission were confirmed. The background contributions for protons are discussed in detail. For proton emission the background arising from (n, p)-reactions was measured and compared with a corresponding Monte-Carlo simulation of elastic (n, p)-clusions. Unlike for tritons and a-particles the P (E, θ) distribution for protons does not show equatorial peaking in 0 between 80 deg. and 90 deg. and contradicts classical scission point emission. The proton distribution, however, agrees with fragment de-excitation calculations in the framework of the cascade evaporation model (CEM) whereas an analogous calculation forα-particles completely fails. Upper limits for an additional scission component of proton emission are given.

Segmented focal plane detector for light and heavy ions

A segmented focal plane detector for an Enge split-pole spectrograph has been developed for the study of breakup reactions at very low relative energies. It consists of a 61 cm long segmented position-sensitive parallel plate avalanche counter backed by a large Bragg curve detector. A segmented plastic scintillator is mounted behind the anode of the Bragg curve detector and is used for particle identification of low-ionizing particles. The dead space between the two sections of the focal plane detector is 2.5 mm. The intrinsic position resolution of the detector is 1 mm. The intrinsic energy resolution depends on the energy of the incident ion and can be as good as 0.55%. The nuclear charge and mass resolutions are 0.3 e and 0.3 u, respectively.

Charge-state distribution measurements of heavy ions

Charge-state distributions of Ar ions after single close collisions (impact parameter ∼1 × 10 −9 cm) with target gases of Ne, Ar, and Kr are measured. The impact parameters are selected so that the L-shell electrons of Ar ions play an important role in determining the resultant charge state. The experimental setup for the measurements of charge-state distributions of heavy ions consists of a magnet and a position-sensitive parallel-plate avalanche counter. Charge-state distributions of several kinds of ions (∼1 MeV/u) after passing through a carbon foil are also measured to test the experimental setup.

A position sensitive gas detector system for Coulomb excitation experiments

A position sensitive parallel-plate avalanche counter for detection of heavy ions, primarily from Coulomb excitation experiments, is presented. The angular region is 40° < θ < 140°, with a division in θ of 2°.

An investigation of two position-sensitive PPACs

Two different position-sensitive parallel plate avalanche counters have been investigated. One is the continuous charge-division read-out PPAC, which after some modifications has an improved timing-response. The other is a transmission-line PPAC, based on the idea of series delay-line read-out, but without external delay-lines resulting in less problems with impedance matching.

A detector system for angular correlation measurements by using parallel plate avalanche counters

A detector system for measurement of angular correlations in binary fission reactions, which are induced by 1 GeV protons, is described. A new type of parallel plate avalanche counsisting of two grids delivers the start signal for the time-of-flight measurement for the correlated fragments. With this detector we obtained an energy loss of 7.8 MeV and an intrinsic time resolution of τ=320 ps for spontaneous fission fragments from a 252Cf source. A large area position-sensitive parallel plate avalanche counter (3.5×18 cm 2) with delay-line read-out measures the coordinate of the complementary fragment within an accuracy of 4.3 mm (corresponding to 1.3°). The spatial resolution has been measured for α-particles and fission fragments under different conditions. The reliability of the developed detector system was checked experimentally with U and Bi targets, which were bombarded with 1 GeV protons.