Sensitive Parallel Plate Avalanche Counters Research Articles

Large area PPAC development at the Rare Isotope Science Project

Large area position sensitive parallel plate avalanche counters (PPACs) have been fabricated for the Rare Isotope Science Project. These detectors have active areas of 20 × 20 cm2 and 40 × 20 cm2, and utilize a stripped electrode structure, together with a delay-line readout, to extract position information. The 20 × 20 cm2 detector performance was tested with 3 MeV/u 12C and 16O beams. A position resolution better than 1 mm, full width at half maximum, and a detection efficiency of 94% were measured with an incident beam intensity of 2 × 106 particles per second. A new production technique, using photolithography, that makes the fabrication of stripped PPAC electrodes larger in area than was previously possible, is also presented.

Construction and performance test of prototype parallel plate avalanche counters at RAON

Two prototype position sensitive parallel plate avalanche counters (PPACs) have been fabricated at the Rare Isotope Science Project (RISP). Both detectors have active areas of 10 × 10 cm2 and utilize a stripped electrode structure, together with a delay line readout, to extract position information. Testing was conducted with an 241Am α source, and 2-dimensional position information was obtained. A position resolution of 0.55 mm full width at half maximum (FWHM), together with a position linearity of ±55 μm over a 67-mm detection range, were measured. A time resolution of 450 ps (FWHM) was also measured.

SOLEROO: A solenoidal exotic rare isotope separator at the Australian National University

A low-mass radioactive ion beam capability in Australia has been developed using a 6.5 T superconducting solenoid as the separator element. The separator, called SOLEROO, separates the large background of primary-beam particles from the radioactive species of interest. A further rejection of remnant unwanted nuclear species leaving the solenoid is achieved by tracking each emerging particle and identifying them event-by-event using a pair of position sensitive parallel plate avalanche counters. With primary 7Li beam current of 1 e μ A , a 6He production rate of 1.2 × 10 5 s − 1 has been achieved. The tagged secondary beam will be combined with a high efficiency 512 pixel silicon detector array for nuclear experiments.

Evolution of the prompt dipoleγ-ray emission with incident energy in fusion reactions

MeV/nucleon, with the aim to probe its evolution with incident energy. These reactions populate, through entrance channels having different charge asymmetries, the 132 Ce compound nucleus at an excitation energy of 117 MeV with identical spin distribution. Fusion events were selected by detecting high-energy γ-rays in coincidence with evaporation residues. The present results can be compared directly with those related to the same reactions at Elab � 9 MeV/nucleon where the compound nucleus excitation energy was equal to 173.5 MeV [1]. This study could be of aid in the formation of superheavy elements. In fact, the emission of pre-equilibrium dipole photons could represent an efficient new cooling mechanism of the composite system in charge asymmetric ”hot” fusion reactions, increasing thus its survival probability against fission [2]. EXPERIMENTAL SET-UP The experiment was performed by using the pulsed beams of 32 S and 36 S provided by the heavy-ion 15 MV Tandem-XTU accelerator of the Laboratori Nazionali di Legnaro (Italy) at Elab = 196 MeV and 214.2 MeV, respectively, impinging on 550 � g/cm 2 thick 100 Mo ( 97.42%) and 96 Mo ( 95.9%) self-supporting targets. The beam consisted of � 2 ns wide bunches with a 400 ns separation and it was measured in a Faraday cup shielded with lead and paraffin to reduce the background due to γ-rays and neutrons. Beam current was about 10 nA. The γ-rays were detected by using six seven-pack clusters of BaF2 scintillators situated at 28 cm from the target at different θ angles with respect to the beam direction. The total solid angle covered by all the clusters was 1.6 sr. Each cluster was surrounded by a 3 mm thick lead shield which reduced the counting rate due to the low energy γ-rays to 50% and stopped the charged particles. The evaporation residues were detected by means of four position sensitive Parallel Plate Avalanche Counters (PPAC’s) located at θ = 7 ◦ symmetrically around the beam direction at 70 cm from the target. The total solid angle covered by the PPAC’s was 0.089 sr. They provided the time of flight (TOF) with respect to the radiofrequency signal of the accelerator, the energy loss (�E) and the position of the reaction products. The energy calibration of the γ-ray detectors was obtained by using the sources 60 Co, 88 Y, the composite source of 241 Am+ 9 Be and the 15.1 MeV γ-rays from the p+ 12 C reaction. Down-scaled single events together with coincidence events between a PPAC and at least one fired BaF2 scintillator were collected during the experiment. A coincidence event was accepted if the deposited energy in a BaF2 cluster was greater than � 5 MeV. The threshold of each BaF2 scintillator was set at � 100 keV. The coincidence request eliminated any cosmic ray contamination of the γ-ray spectra.

Efficiency of position sensitive PPAC for various ions

The detection efficiencies of a position sensitive parallel plate avalanche counter, measured with 40 MeV/u 17N beam bombarding on a 621 mg/cm 2 197Au target, were observed to be significantly different for different ions from helium to oxygen. Furthermore, for a given type of ion, the efficiency decreases with the increase of the incident energy.

A position sensitive parallel plate avalanche counter for single particle and current readout

A parallel plate avalanche counter (PPAC) has been developed to serve as a radioactive beam monitor detector for the REX-ISOLDE project at CERN. The PPAC has a compact design with an active diameter of 4 cm , a low effective thickness of ∼1 mg/ cm 2 , a spatial resolution in the x and y directions of 1.6 mm , an applicability for all heavy ions with Z≥2, and a large dynamical range in counting rates of up to 10 9 s −1 due to single particle or current readout, respectively.

SCORPION: A system for coincidences between recoil and projectile ions at NSC, New Delhi

An on-line facility to measure coincidences between the recoil ions and the scattered projectiles (SCORPION) has been designed, fabricated and commissioned at Nuclear Science Centre (NSC), New Delhi. The facility consists of a four jaw slit assembly, a time of flight (TOF) spectrometer, a parallel plate electrostatic charge analyser and a one dimensional position sensitive parallel plate avalanche counter (PPAC). Details of the design and working principles of various components and the test results obtained for the Si q+-Ar collision system are presented to highlight the performance of the system. A multiple loss of up to four electrons has been observed for 60 MeV Si4+ ions colliding with argon atoms in a single collision condition. Spectra of recoil ions detected in coincidence with a particular charge state of the scattered projectile show a bell shaped distribution as a function of the recoil charge state (r) for the electron loss events. However, the yield of recoil ions drops asr increases for the direct ionization channel. Also for electron loss, the peak of the recoil ion distribution is seen to shift to a higher recoil charge state as the number of lost electrons from the projectile increases.

Study of the beta-delayed alpha-particle emission ofN16

The beta-delayed alpha-particle emission of $^{16}\mathrm{N}$ has been studied, with $^{16}\mathrm{N}$ nuclei produced using 80 MeV/nucleon $^{18}\mathrm{O}$ beams on $^{9}\mathrm{Be}$ targets. The $^{16}\mathrm{N}$ secondary nuclei were mass analyzed and separated from the reaction products using the Michigan State University A1200 isotope separator. A detector array, including four thin surface barrier detectors, a p-i-n diode, a Ge gamma-ray detector, and a two-dimensional position sensitive parallel plate avalanche counter, was used for implantation and study of the separated nuclei. A beta-decay branching ratio of (1.3\ifmmode\pm\else\textpm\fi{}0.3)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$ to the ${1}^{\mathrm{\ensuremath{-}}}$ state at 9.6 MeV and a centroid of 2.35\ifmmode\pm\else\textpm\fi{}0.05 MeV for the beta-delayed alpha-particle emission were measured. These results are essential for the analysis of a high sensitivity measurement at Yale University of the low-energy beta-delayed alpha-particle emission of $^{16}\mathrm{N}$, and for understanding the $^{12}\mathrm{C}$(\ensuremath{\alpha},\ensuremath{\gamma}${)}^{16}$O reaction in the helium burning process in massive stars.

A focal plane detector for reactions with medium weight projectiles

Abstract A new focal plane detector for an Enge split pole spectrograph has been developed which is able to resolve individual elements and isotopes up to the mass 100 region. It consists of a 60 cm long position sensitive parallel plate avalanche counter backed by a large Bragg curve detector. Compared with other position sensitive focal plane counters the new detector system has a very good time resolution (less than 300 ps) and can be operated at much higher counting rates (up to 25 kHz). The intrinsic resolution of the position detector is less than 1 mm. In addition to the energy and the nuclear charge signal obtained from the Bragg curve detector the angle of incidence into the detector can be measured with an accuracy of better than 1°. The detector has already been used in a variety of experiments where good timing, counting rate behavior, and excellent mass resolution over a large energy range were essential.

Measurement of high momentum transfer reactions by recoil detection

A method is described for studying reactions at medium energies by measuring the magnetic rigidity, time of flight, and energy loss of the resulting recoil products. The method works best for reactions with two-body final states where one of the outgoing particles is relatively light. A magnetic spectrometer with a special focal plane detector has been used. The detector consists of two position sensitive parallel plate avalanche counters and two proportional counters. Differential cross sections for the 12C(p, π+13C reaction at recoil angles which correspond to the pion being emitted at a backward angle in the center of mass have been measured at bombarding energies of 166 and 186 MeV. Data were also obtained for previously unobserved 12C(p, π0)13N reaction. Several advantages of the method are discussed.

Report on a Position Sensitive Parallel Plate Avalanche Counter with a Distributed Constants Delay-Line-Cathode

A position sensitive parallel plate (PSPP) stop detector for heavy ions with an active area of 70×76 mm2 has been developed. The cathode is a printed circuit board with parallel strips which form a distri buted constant delay-line. The position resolution is better than 1 mm in the x direction (orthogonal to the strips) and 2 cm in the y direction (along the strips). The anode time resolution is about 300 psec fwhm.

Preliminary results on a position sensitive parallel plate avalanche counter with a distributed constants delay-line cathode

A position sensitive parallel plate (PSPP) stop detector for heavy ions with an active area of 70 × 76 mm 2 has been developed. The cathode is a printed circuit board with parallel strips which form a delay-line. The position resolution is better than 1 mm in the x direction (orthogonal to the strips) and better than 2 cm in the y direction (along the strips). The anode time resolution is about 300 ps fwhm.

Test and performance of position sensitive parallel plate avalanche detectors in heavy-ion kinematic coincidence measurements

Two-dimensional position sensitive parallel plate avalanche counters (PPAC) with an active area of 6 × 16 cm 2 were built and used in particle-particle-gamma coincidence experiments with heavy ions. The performance of the detector and of a kinematical coincidence set-up with two detectors is described. The position resolution in the x and y coordinates is Δx=1 mm and Δy=5 mm. A time resolution of Δt=150 ps has been achieved in the case of elastic scattering of 5–10 MeV/u 86Kr from different targets.

Precise angular distribution measurements for high energetic ions

The reliability of a position sensitive parallel plate avalanche counter as a start detector at the entrance of a magnetic spectrometer is demonstrated. Implications for experiments with high energetic heavy ions are drawn from the results.