Gas Ionization Chamber Research Articles

Performance of a gas flow ionization detector filled with He-iso-C4H10 mixtures for STIM-T

A cylindrical gas flow ionization chamber has been developed for measuring particle energy in Scanning Transmission Ion Microscopy Tomography (STIM-T) experiments due to its ability to withstand the direct beam. The response of a He-iso-C4H10 filled ionization detector to 2MeV H+ and He+ beams was studied. Different operating parameters, such as concentration of isobutane (in the range of 55–100%), anode voltage, amplifier shaping time, the geometry of the detector entrance canal and the solid angle of the detector, were investigated. The stable operating plateau and the anode voltage at which the best energy resolution is attained were also determined for every gas mixture. The best energy resolution achieved so far for 2MeV H+ and He+ static beams was ∼1.3%, which is comparable to that of Si PIN diode detectors (in the range of 15–30keV). Computed tomography (CT) was applied to a set of STIM projections acquired with the gas ionization chamber at the IST/CTN microprobe beam line in order to visualize the 3D-mass distribution in a test structure.

QXAFS Data Acquisition System Based on EPICS at SSRF

A Quick-scanning XAFS (QXAFS) data acquisition system based on EPICS is achieved at the Shanghai Synchrotron Radiation Facility (SSRF) XAFS beamline. The hardware and software system are introduced. Gas ionization chambers, current amplifiers and data acquisition card are utilized to obtain the X-ray intensity before and after the sample. Four fine QXAFS spectra with an energy range of 1.2 keV at the Cu K-edge have been collected in 5 seconds. The results indicate the good repeatability of the QXAFS data acquisition system. It makes a lot of sense for the researchers to carry out experimental study at SSRF.

Analysis of the Performances of Sealed Timing Resistive Plate Chambers (tRPCs)

Resistive Plate Chambers (RPCs) were introduced by R. Santonico and R. Cardarelli in 1981, are gas ionization chambers made with resistive electrodes separated by precision spacers. Typical gas gap ranges from a few hundred micrometers to several millimeters wide. Timing Resistive Plate Chambers (tRPCs) were introduced in 2000 by P.Fonte, A. Smirnitsky and M.C.S Williams and since then it has reached Time Resolutions better than 50 ps (σ) with efficiencies above 99% for Minimum Ionizing Particle (MIP). In this research paper, we described the main features of gas detectors and the different types of RPCs and their properties. We described the main results that we have got during the operating the sealed tRPCs built in the laboratory.

Time-of-flight ERD with a 200 mm2 Si3N4 window gas ionization chamber energy detector

Low energy heavy ion elastic recoil detection work has been carried out in Jyväskylä since 2009 using home made timing detectors, a silicon energy detector and a timestamping data acquisition setup forming a time-of-flight–energy telescope. In order to improve the mass resolution of the setup a new energy detector was designed to replace the silicon solid state detector, which suffered from radiation damage and had poor resolution for heavy recoils.In this paper the construction and operation of an isobutane filled gas ionization chamber with a 14×14mm2 100nm thick silicon nitride window are described. In addition to greatly improved energy resolution for heavy ions, the detector is also able to detect hydrogen recoils simultaneously in the energy range of 100–1000keV. Additionally the detector has position sensitivity by means of timing measurement, which can be performed without compromising the performance of the detector in any other way. The achieved position sensitivity improves the depth resolution near the surface.

Detector system for the study of low energy heavy ion reactions using kinematic coincidence technique

The characteristics and performance of a new detector system developed for the study of low energy heavy ion binary reactions using the kinematic coincidence technique are presented. The detector system has been developed to carry out experiments such as multi-nucleon transfer reactions using the General Purpose Scattering Chamber (GPSC) facility at IUAC [1,2]. The detector system consists of a pair of two-dimensional position sensitive multi wire proportional counter (MWPC) and a ΔE−E gas ionization chamber. Both MWPC have an active area of 5×5cm2, and provide position signals in horizontal (X) and vertical (Y) plane, and timing signal for time of flight measurements. The main design feature of MWPC is the reduced wire pitch of 0.025in. (0.635mm) in all electrodes, giving uniform field and faster charge collection, and usage of 10μm diameter in anode frame which gives higher gains. The position resolution of the detectors was determined to be 0.45mm FWHM and time resolution was estimated to be 400ps FWHM. The detector could handle heavy ion count rates exceeding 100kHz without any break down. The timing and position signals of the detectors are used for kinematic coincidence measurements and subsequent extraction of their mass and angular distributions. The ionization chamber has a conventional transverse field geometry with segmented anode providing multiple ΔE signals for nuclear charge (Z) identification. This article describes systematic study of these detectors in terms of efficiency, count rate handling capability, time, position and energy resolution.

10Be and 26Al low-energy AMS using He-stripping and background suppression via an absorber

The transmission of the ion beam through a tandem accelerator is a critical parameter for efficient detection of long-lived radionuclides by sensitive accelerator mass spectrometry (AMS). With beam energies at the accelerator terminal of less than 600keV, high transmissions are obtained using He as stripper gas. Here, we discuss Be, B, and Al transmissions in view of their application in the AMS determination of the long-lived radioisotopes 10Be and 26Al with compact facilities. The charge state 2+ of Al and Be shows a high yield, but in both cases an intense background from other nuclides has to be handled. The applicability of a combination of an absorber cell with a gas ionization chamber was tested for suppression of the main background for 10Be2+ (10B2+) and 26Al2+ (13C1+). Energy loss simulations of the involved nuclides confirm the performance observed in the experiments. The findings concerning He stripping and detection methods at low energies may allow the construction of very compact AMS setups for light isotopes.

The possibility of using a simple pulse mode parallel plate gas ionization chamber, without Frisch grid, both for energy estimation and Z-identification of moderate energy light heavy ions

This work explores theoretically the possibility of using a simple pulse mode parallel plate gas ionization chamber, having no Frisch grid, both for energy estimation and Z-identification of moderate energy light heavy ions. A mathematical expression for the energy of a heavy ion that enters into the ionization chamber through the cathode window and gets stopped in the sensitive volume is derived. An expression for a quantity similar to the range of the heavy ion is also derived. The plot of energy against this quantity is expected to give an opportunity to use a simple pulse mode parallel plate gas ionization chamber, without Frisch grid, as a light heavy Z-identifier. This work is based on the measurement of the electron collection pulse height and two other heights that the electron collection pulse reaches at two pre-calculated instants of time during the pulse rise time. A 'preset pulse clipper', the basic principle of which was proposed in a previous paper, may be used to measure the heights. Measuring heights - without using the 'preset pulse clipper' - by means of digital sampling and software based processing techniques may be possible if it be possible to determine the start time of the digitized pulse. One possible method for determining the start time of the digitized pulse is evaluated. The simulated plots, which represent the expected identification capability of this method, are made considering all the phenomena relevantly associated from physical point of view.

A Multi-detector NaI(Tl) Gamma-ray Spectrometry System for Investigation of Neutron Induced Capture and Fission Reactions

At the Joint Institute for Nuclear Research (JINR) Frank Laboratory of Neutron Physics (FLNP), a new multi-detector gamma-ray spectrometry system (MDGRSS) was constructed. It consists of 24 hexagonal NaI(Tl) detectors, arranged in two cylindrical arrays of variable diameter and distance between them. Test measurements with the MDGRSS are going on at one of the neutron beam-lines of the pulsed white-spectrum neutron source IREN. Some preliminary results from a measurement of the resonance-neutron flux density at IREN 60m flight-path station, using 181Ta(n,γ) reaction, are reported. In combination with a multi-section parallel-plate gas-ionization chamber as a fission fragment detector, positioned in the centre of the system, it is possible to investigate the neutron-induced capture and fission reactions on a number of heavy isotopes, important for fundamental and applied neutron and nuclear physics.

Energy resolution of gas ionization chamber for high-energy heavy ions

The energy resolution is reported for high-energy heavy ions with energies of nearly 340 MeV/nucleon and was measured using a gas ionization chamber filled with a 90%Ar/10%CH4 gas mixture. We observed that the energy resolution is proportional to the inverse of the atomic number of incident ions and to the inverse-square-root of the gas thickness. These results are consistent with the Bethe–Bloch formula for the energy loss of charged particles and the Bohr expression for heavy ion energy straggling. In addition, the influence of high-energy δ-rays generated in the detector on the energy deposition is discussed.

Measurement of photon flux with a miniature gas ionization chamber in a Material Testing Reactor

Nuclear heating measurements in Material Testing Reactors (MTR) are crucial for the design of the experimental devices and the prediction of the temperature of the hosted samples. Nuclear heating in MTR materials (except fuel) is mainly due to the energy deposition by the photon flux. Therefore, the photon flux is a key input parameter for the computer codes which simulate nuclear heating and temperature reached by samples/devices under irradiation. In the Jules Horowitz MTR under construction at the CEA Cadarache, the maximal expected nuclear heating levels will be about 15 to 18Wg−1 and it will be necessary to assess this parameter with the best accuracy. An experiment was performed at the OSIRIS reactor to combine neutron flux, photon flux and nuclear heating measurements to improve the knowledge of the nuclear heating in MTR. There are few appropriate sensors for selective measurement of the photon flux in MTR even if studies and developments are ongoing. An experiment, called CARMEN-1, was conducted at the OSIRIS MTR and we used in particular a gas ionization chamber based on miniature fission chamber design to measure the photon flux. In this paper, we detail Monte-Carlo simulations to analyze the photon fluxes with ionization chamber measurements and we compare the photon flux calculations to the nuclear heating measurements. These results show a good accordance between photon flux measurements and nuclear heating measurement and allow improving the knowledge of these parameters.

New gas detector setup for on-axis STIM tomography experiments

A gas flow ionization chamber for use with on-axis scanning transmission ion microscopy tomography (STIM-T) has been developed. The entrance window is composed of a square silicon nitride membrane 100nm thick and 1mm2 in area. The use of this type of window does not add significantly to the energy resolution with the MeV H+ or He+ particles used in STIM, and proved to be resistant to high proton fluence in the irradiated spot. The ability of such detector to withstand direct beam hit with acceptable energy resolution makes it suitable for on-axis STIM-T, in this respect outperforming the more standard Si PIN diodes, which performance is known to degrade above fluences of ∼1010–1012cm−2. The present in-line design while allowing easy mounting of the detector to the existing target chamber, has the peculiarity of providing a practical way of replacing the Si3N4 membrane in case it brakes while operating. The concept of gas ionization chamber under development is expected to become ideal for on-axis STIM-T experiments due to its low ageing during operation, and anticipated attainable speed and energy resolution.

A Simple Way to Upgrade a Compact Radiocarbon AMS Facility for 10Be

A simple way to upgrade the Peking University 500kV NEC radiocarbon facility (CAMS) for 10Be measurements is presented. In a first phase, a silicon nitride foil as passive boron degrader was mounted in front of the electrostatic deflector near the focal plane of 10Be. The Si detector at the end of the beam line was replaced with a high-resolution ΔE-Eres gas ionization chamber. In addition, a Faraday cup for the measurement of 9Be1+ was installed. Tests with this arrangement showed promising results: a 10Be/9Be background level of 3.4 × 10–14 and an overall transmission for 10Be of 2.2% were obtained. Measurements of standards showed very good stability and reproducibility. In the next step, it is planned to add a second magnet to reduce the background and to partly compensate losses due to energy and angular straggling in the degrader foil by the energy and angular refocusing effect of a magnetic sector field. With this final arrangement, a performance with 10Be/9Be background levels at 10−15 and 10Be overall transmission of 6–7% can be expected. The design proposed in this paper has the advantage that the modifications can be realized in a rather inexpensive way and that the measurement performance for 14C will not be affected.

Energy resolution measurement and application of the F series ORTEC SSB detector in TOF-ERDA spectrometry

In the Elastic Recoil Detection Analysis (ERDA) and Heavy Ion Rutherford Backscattering Spectrometry (HIRBS), silicon surface barrier (SSB) detectors as well as other types of Si charged particle detectors are conventionally used for measuring ion energy due to their simplicity and ease of use. Energy resolution of such detectors is a limiting factor for both, mass and depth resolution in the experiment. In the present work we have studied performance of the commercially available F series ORTEC SSB detector designed in particular for heavy ion spectroscopy (BF-023-300-60). Detector energy and mass resolution were measured for a wide range of ion masses (7Li, 16O, 28Si, 35Cl and 81Br) and energies (2–20MeV). Obtained results were compared with the already published data for a standard A series ORTEC SSB detector (BA-017-100-100) and gas ionization chambers. Possible application of the F series SSB detector in time-of-flight ERDA (TOF-ERDA) spectrometer was discussed.

Performance of the ETH gas ionization chamber at low energy

The performance of gas ionization chambers (GIC) for the detection of low energy ions has been considerably improved in the past years by the use of silicon nitride entrance windows and low noise preamplifiers. This has led to an increased use of high resolution GICs in the fields of accelerator mass spectrometry and ion beam analysis. This development and the underlying physical principles are reviewed and the latest technical status of such devices is summarized.A detailed study on energy resolution and pulse height defect is presented with projectiles covering a wide particle mass range (H, 9Be, 13C, 27Al, 35Cl, 127I, 232Th) with energies between 0.1 and 2.2MeV. The dependence of energy resolution and charge output per unit particle energy on the nuclear charge of the projectile is investigated and parametrized. SRIM calculations of ionizing energy loss considerably differ from these experimental findings. For 1MeV particles discrepancies up to 50% are observed.The performance of GICs and their practical use is compared to that of solid state detectors. The potential for further improvement of the technology and its fields of application are assessed.

Dosimetric Response of a REM-500 in Low Energy Neutron Fields Typical of Nuclear Power Plants

This study investigates the response of a REM-500 to assess neutron quality factor and dose equivalent in low energy neutron fields, which are commonly encountered in the workplace environment of nuclear power stations. The McMaster University 3 MV Van de Graaff accelerator facility was used to measure the response of the instrument in monoenergetic neutron fields in the energy range 51 to 727 keV by bombarding a thin LiF target with 1.93-2.50 MeV protons. The energy distribution of the neutron fields produced in the facility was measured by a (3)He filled gas ionization chamber. The MCA mode of the REM-500 instrument was used to collect lineal energy distributions at varying neutron energies and to calculate the frequency and dose-mean lineal energies. The effective quality factor, Q-, was also calculated using the values of Q(y)listed in the REM-500 operation manual and compared with those of ICRP 60. The authors observed a continuously increasing trend in y - F, y-D, and Q-with an increase in neutron energy. It is interesting to note that standard tissue equivalent proportional counters (TEPCs) filled with tissue equivalent(TE) gas give rise to a similar trend for these microdosimetric quantities of interest in the same energy range; however, the averages calculated in this study are larger by about 15%compared to a TEPC filled with propane-based TE gas probably because of the larger stopping power of protons in propane compared to TE gas. These somewhat larger event sizes did not result in any significant increase in the Q-compared to those obtained from a TEPC filled with TE gas and were found to be in good agreement with other measurements reported earlier at corresponding neutron energies. The instrument quality factor response, R(Q), defined as the ratio of measured quality factor to the calculated quality factor in an ICRU tissue sphere,was found to vary with neutron energy. The instrument response,R(Q), was ~0.6 at 727 keV, which deteriorates further to ~0.3 at 51 keV neutron energy. The counter response based on ICRP 60 was comparable to an ideal response of 1.0 above 600 keV, which dropped to ~0.8 at 159 keV and ~0.4 at 51 keV neutron energy. The decline in counter quality factor response based on ICRP 60 was found to be much steeper than that when using the instrument’s built-in function for quality factor.The REM-500 measures a dose equivalent at 727 keV,which is 60% of the ambient dose equivalent, 40% at 159 keV,and 15% at 51 keV. Two algorithms have been developed, one for real time measurement and another to be used post measurement,and their efficacy is demonstrated in determining the quality factor and the ambient dose equivalent in low energy neutron fields, which are typical for the workplace environment in CANDU® nuclear power generating stations.

Zr–Nb isobar separation experiments for future 93Zr AMS

AMS detection of the rare isotope 93Zr (t1/2=1.6Ma) has application potential in two fields of research: a better determination of the 92Zr(n,γ)93Zr cross section, which is relevant in astrophysical modeling of nucleosynthesis processes, and using this radionuclide as tracer in hydrological and radioactive waste studies. The biggest challenge in measuring 93Zr at natural concentrations is adequate separation from its stable isobar 93Nb. The Nuclear Science Laboratory at the University of Notre Dame is developing the capability to measure 93Zr by AMS. Results are reported of first experiments, featuring the combination of a gas-filled magnet with a position-sensitive Parallel Grid Avalanche Counter and a Gas Ionization chamber in this magnet’s focal-plane.

A first attempt to measure 92Nb/93Nb ratios with Accelerator Mass Spectrometry

An Accelerator Mass Spectrometry (AMS) method for the measurement of the long-lived radionuclide 92Nb has been established at the HI-13 Tandem Accelerator of the China Institute of Atomic Energy (CIAE). Niobium powder mixed with PbF2 by a ratio of 1:2 (in mass) was used as the cathode material. Atomic anions of Nb− were extracted from a Cs-beam sputter source. The terminal voltage of the tandem accelerator was 8.5MV. Nb13+ ions were selected after terminal foil stripping. A multi-anode gas ionization chamber was used for the particle detection. The total suppression factor of the two major interfering isobars, 92Zr and 92Mo, was about 103. A detection limit of about 10−11 was achieved for 92Nb/93Nb ratio measurements on a blank sample.

Design and fabrication of a miniaturized gas ionization chamber for production of high quality ion beams

A high performance electron impact gas ion source for use in high resolution focused ion beam (HR FIB) applications is currently being developed. For high source brightness and low ion energy distribution operations this ion source requires a gas ionization chamber with small dimensions. We have designed and fabricated prototype gas chambers using MEMS fabrication techniques. The gas chamber is a sandwich structure of two silicon substrate pieces, each holding a 100nm thick metal membrane, with a thin silicon nitride spacer in-between. Our first prototypes resulted in a gas chamber spacing of [email protected] caused by glue seepage and particle contaminations although our fabrication method is designed for 200nm. A further increase in the gas chamber spacing has been observed under a high gas load. However, our analysis suggests that the load deflection can be sufficiently minimized by reducing the metal membrane size to <[email protected]

Cryogenic Loss Monitors with FPGA TDC Signal Processing

Radiation hard helium gas ionization chambers capable of operating in vacuum at temperatures ranging from 5K to 350K have been designed, fabricated and tested and will be used inside the cryostats at Fermilab's Superconducting Radiofrequency beam test facility. The chamber vessels are made of stainless steel and all materials used including seals are known to be radiation hard and suitable for operation at 5K. The chambers are designed to measure radiation up to 30 kRad/hr with sensitivity of approximately 1.9 pA/(Rad/hr). The signal current is measured with a recycling integrator current-to-frequency converter to achieve a required measurement capability for low current and a wide dynamic range. A novel scheme of using an FPGA-based time-to-digital converter (TDC) to measure time intervals between pulses output from the recycling integrator is employed to ensure a fast beam loss response along with a current measurement resolution better than 10-bit. This paper will describe the results obtained and highlight the processing techniques used.

A new mini gas ionization chamber for IBA applications

Novel prototypes of high resolution gas ionization chambers ( GIC) were designed with increased compactness and simplicity of the setup. They have no Frisch-grid and a simple anode wire. Under certain operating conditions these mini detectors have an energy resolution comparable with that of state-of-the-art GICs of much higher complexity. They can be operated both under vacuum and atmospheric pressure. First measurements were made with protons in the energy range of 0.3–1.0 MeV. For protons at 0.3 MeV an energy resolution of about 12 keV was achieved. With a 72 MeV 129Xe beam a relative resolution of 1.4% was obtained. Due to their versatility and reduced size the detectors can easily be applied in the field of ion beam analysis ( IBA) and accelerator mass spectrometry ( AMS) . Since they are almost completely insensitive to radiation damage they are especially suited for use in high fluence applications such as scanning transmission ion microscopy ( STIM). A comparison of the radiation hardness of the mini GIC with a Si PIN diode was therefore performed. The GIC showed no peak shift or change in energy resolution at all after collecting 10 15 protons per cm 2 while the performance of the Si detector clearly started to degrade at 10 12 particles per cm 2.