Multiwire Proportional Chamber Detector Research Articles

Dielectronic recombination experiment of Na-like Kr<sup>25+</sup> at heavy ion storage ring CSRe

The experimental study of precision spectroscopy of dielectronic recombination (DR) of highly charged ions is not only important for astronomical plasma and fusion plasma, but also can be used as a new precision spectroscopy to test the strong-field quantum electrodynamic effect, measure isotope shift, and extract the radius of atomic nuclei. An specially designed electron beam energy detuning system for electron-ion recombination precision spectroscopy experiments has been installed on the heavy ion storage ring CSRe in Lanzhou, China, where the electron-ion collision energy in the center-of-mass system can be detuned to 1 keV, and an independently-developed plastic scintillator detector and multiwire proportional chamber detector have been installed downstream of the electron cooler of the CSRe for detecting recombined ions. The multiwire proportional chamber detector has the ability to non-destructively monitor the profile of the ion beam in real-time while acquiring the recombined ion counts, providing guidance for optimizing the ion beam. On this basis, the first test experiment on dielectronic recombination of Kr<sup>25+</sup> ions is carried out at the CSRe, and the dielectronic recombination rate coefficients in a range of 0–70 eV in the frame of center-of-mass are measured. In order to fully understand the experimental results, we calculate the dielectronic recombination rate coefficient of the Kr<sup>25+</sup> ion by using the flexible atomic code (FAC) and make a detailed comparison with the experimental result, showing that they are in good agreement with each other, and only the resonance energy values of the two resonance peaks at 1.695 eV and 2.573 eV are significantly different. In addition, the DR resonance energy values and intensities are obtained by fitting the experimental results in a range of 0–35 eV, and we find that the transition 3s→4l (∆<i>n</i> = 1) contributes significantly to the experimental spectral lines. Furthermore, we compare the plasma rate coefficients derived from the DR rate coefficients with those derived from the AUTOSTRUCTURE and FAC theories, which differ by 20 percent in a temperature range less than 10<sup>6</sup> K. The experimental results show that the DR experimental platform of the CSRe has very good stability and reproducibility, and can provide support for the future DR experiments of highly charged ion, i.e. for testing strong-field quantum electrodynamics effect and measuring the properties of atomic nuclei.

A two-dimensional neutron detector assembly at the China Mianyang Research Reactor

A two-dimensional neutron detector consisting of 96 3He position-sensitive proportional counters was assembled at the China Mianyang Research Reactor. With a count rate limit that is higher than that of the initial multi-wire proportional chamber detector at CMRR, it will be used for the small-angle neutron scattering spectrometer Suanni. The problems caused by low air pressure and γ radiation in the working environment are pretreated, and detector performance is evaluated and compared with that of the initial proportional chamber. Now the new detector is ready to be used for Suanni.

Evaluation of the readout electronics based on the center of gravity method for position sensitive radiation detection.

In the application of position sensitive radiation detection, the center of gravity method is often used to obtain better spatial resolution. In order to obtain the resolution degradation caused by the readout electronics, an evaluation method is put forward in this paper. The principle of the method is to simulate the signal distribution on sense wires of the MWPC (Multiwire Proportional Chamber) detector. The evaluation software quantizes the simulated data and drives the digital to analog converter to generate test signals. The readout electronics is evaluated with these stimulus signals according to the readout scale. An evaluation board based on this method is implemented. Tests are carried out in the laboratory to evaluate a readout circuit for the MWPC detector. The position resolution contributed by the electronics is better than 15 μm when the swtiching frenquency of the switch array is 12.5 MHz. The test results proved that the evaluation method is correct and practical. It can greatly simplify the evaluation of the readout electronics.

Multiplexing readout method based on switch arrays for position sensitive thermal neutron detectors

To address complexities arising from the increased number of readout channels in large scale neutron detection or imaging systems, a multiplexing readout method is introduced. The proposed method can greatly reduce the scale and cost of the readout electronics. To evaluate the readout method, a prototype involving a front-end circuit and a signal multiplexed circuit for detectors such as multiwire proportional chamber (MWPC), gaseous electron multipliers (GEM) and micro-channel plates (MCP) is evaluated in the laboratory. The multiplexing circuit consists of a switch array and a high speed analog to digital converter (ADC). By controlling the switch timing, multi-channel signals can be readout through only one ADC channel, thereby reducing the number of channels required for readout. Furthermore, the readout speed can be adjusted by changing the switching frequency. The results show that the multiplexing readout method is feasible, and the position resolution for thermal neutron detectors is good. The evaluation board is used to simulate the MWPC detector with 2 mm spacing and a position resolution of 35 μm is obtained with event rate up to 2 MHz. Besides, joint test with a thick gaseous electron multipliers (TGEM) detector with 0.8 mm spacing yields a position resolution of about 400 μm.

Status of the two-dimensional, multi-wire proportional chamber detector for the China Spallation Neutron Source

The re-designed two-dimensional, multi-wire proportional chamber (MWPC) detector based on the [Formula: see text]He operation gas has been developed for the multifunctional reflection spectrum detection requirements in China Spallation Neutron Source (CSNS), which is under construction in Guangdong province, China. This efficient thermal neutron detector with large area (200 mm [Formula: see text] 200 mm active area), two-dimensional position sensitive (<2 mm of position resolution), high detection efficiency (>65% in the wavelength of 1.8Å) and good n/[Formula: see text] discrimination would meet some requirements in CSNS The neutron detector consists of a MWPC detector and a high-pressure gas vessel. The wire readout structures of the detector and the gas purity device have been optimized based on previous design and testing. The re-designed MWPC detector with an absorber thickness of 10 mm and 8.5 atm operating gas mixture of [Formula: see text]He and C[Formula: see text]H[Formula: see text] was constructed. Using the non-return valve manufactured by Swagelok, the gas purity device was developed to clean the water and remove gas impurities. The effective cycle time can be up to 50 min per sequence. The performance of the position resolution and the two-dimensional imaging accuracy by the traditional center of gravity readout method was studied with an X-ray radiation source and the neutron source. At the end of this year, the detector will be mounted at CSNS and studied using the neutron source.

Small three-layer multiwire-based detector for cosmic ray muon variation studies at high geomagnetic rigidity cutoff

Different types of ground-based detectors have been developed and deployed around the world to monitor and study cosmic ray (CR) variations. We have designed, constructed, and operated a small (20×20 cm2) three-layer multiwire proportional chamber detector for CR muon observations. The technical aspects of this detector will be briefly discussed. The ability of the detector to detect high-energy CR muons was established. The detector performed well in this sense and showed comparable results to our existing 1-m2 scintillator detector. The influence of atmospheric effects, mainly pressure and temperature, on the detected muons was determined. The corresponding coefficients were calculated and used to eliminate the pressure and temperature effects from the measured data.

Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering Determined by the OLYMPUS Experiment

The OLYMPUS Collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, R_{2γ}, a direct measure of the contribution of hard two-photon exchange to the elastic cross section. In the OLYMPUS measurement, 2.01GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight scintillators detected elastically scattered leptons in coincidence with recoiling protons over a scattering angle range of ≈20° to 80°. The relative luminosity between the two beam species was monitored using tracking telescopes of interleaved gas electron multiplier and multiwire proportional chamber detectors at 12°, as well as symmetric Møller or Bhabha calorimeters at 1.29°. A total integrated luminosity of 4.5 fb^{-1} was collected. In the extraction of R_{2γ}, radiative effects were taken into account using a MonteCarlo generator to simulate the convolutions of internal bremsstrahlung with experiment-specific conditions such as detector acceptance and reconstruction efficiency. The resulting values of R_{2γ}, presented here for a wide range of virtual photon polarization 0.456<ε<0.978, are smaller than some hadronic two-photon exchange calculations predict, but are in reasonable agreement with a subtracted dispersion model and a phenomenological fit to the form factor data.

Readout method for two-dimensional multi-wire proportional chamber

A two-dimensional multi-wire proportional chamber detector based on 3He gas is developed for meeting the multifunctional reflection spectrum detection requirements of China Spallation Neutron Source (CSNS). Based on the previous researches in our laboratory, three different wire structures are studied for optimizing the wire readout structure of the two-dimensional multi-wire proportional chamber detector, and the performances of the detectors are measured by two readout methods:the center of gravity readout method and the digital readout method in this paper. The selected method could satisfy the requirement of multifunctional reflection spectrum instrument. Finally, the results indicate that the position resolution and the imaging capability obtained by using the center of gravity readout method should be better than by using the digital readout method. The position resolution could reach to about 160 m by using the center of gravity readout method. While the position resolution of the detector could be obtained to be about 400 m by using the digital readout method. Re-designed and compared with each other are the three different wire structures:1.5 mm of the anode wire pitch and 4 mm of the readout strip pitch with the center of gravity readout method, 1.5 mm of the anode wire pitch and 2 mm of the readout strip pitch with the digital readout method. Both of the optimized designs of the wire structure could meet the requirement of the position resolution for the reflection spectrum device.

Development of a portable and fast wire tension measurement system for MWPC construction**Supported by National Natural Science Foundation of China (A050506), State Key Laboratory of Particle Detection and Electronics and Key Laboratory of China Academy of Engineering Physics (Y490KF40HD)

In a multi-wire proportional chamber detector (MWPC), the anode and signal wires must maintain suitable tension, which is very important for the detector’s stable and accurate performance. As a result, wire tension control and measurement is essential in MWPC construction. A high pressure 3He MWPC detector is to be used as the thermal neutron detector of the multi-functional reflectometer at China Spallation Neutron Source, and in the construction of the detector, we have developed a wire tension measurement system. This system is accurate, portable and time-saving. With it, the wire tension on an anode wire plane has been tested. The measurement results show that the wire tension control techniques used in detector manufacture are reliable.

Towards Quantitative Image Reconstruction Using Monte-Carlo Simulations in Multi-Wire Proportional Chamber-Based Small Animal PET

The quadHIDAC is a dedicated high resolution small animal PET scanner based on multi-wire proportional chamber detectors. It provides very high spatial resolution, good sensitivity, and a large field-of-view allowing the examination of more than one animal in a single scan or a whole body scan of larger species in a single bed position. Excellent image quality has been obtained through list-mode-based EM reconstruction using resolution recovery. However, quantitative results on local uptake are still missing due to both (1) lack of energy discrimination and (2) inaccurate characterization of random events recorded by the scanner. In this work we describe how quantification can be achieved through the use of an appropriate Monte Carlo simulation of the quadHIDAC. The complex structure of the quadHIDAC has been completely implemented in a Geant4 simulation. Point sources, line sources, cylindrical phantoms, and voxelized image data have been successfully simulated and compared to real measurements. The magnitude and spatial distribution of scattered and random events could be quantitatively characterized for the different phantom geometries. The simulation provides access to information on single hit distributions resulting in appropriate randoms corrections in image reconstruction. Both randoms and scatter correction is demonstrated to improve quantification. Their accuracy and performance was tested on simulated and measured data. Using simulation-based correction techniques for quantitative image reconstruction, multi-wire proportional chamber-based PET technology may be attractive for future high resolution PET scanners.

A PCI DAQ board for MWPC detectors with high-rate 2D delay line position readout

For high rate thermal neutron (and e.g. also synchrotron radiation) detection a PCI data acquisition (DAQ) board for readout of two-dimensional position-sensitive multi-wire proportional chamber (MWPC) detectors with delay line position encoding was developed, and a first series of boards was produced and tested. The MWPC board comprises a deadtime-less 8-channel multihit TDC chip of the F1 type with ∼120 ps LSB, a 40 MHz flash ADC, a FPGA, a FIFO, a 0.9 GFLOP DSP chip TMS320C6711 and a 256 MB histogram memory. For position encoding a position-independent start and four position-dependent stop signals are recorded from the MWPC anode and from either end of X and Y delay lines connected to the MWPC cathodes, respectively. Time-of-flight (TOF) can be measured with reference to a pulsed beam or chopper signal either with ⩾25 ns bin size for TOF ranges of up to ∼420 ms or alternatively with ∼120 ps LSB for ranges ⩽16 ms . The pulse height of the MWPC anode signal is digitized in the flash ADC for neutron-gamma and background discrimination. Hardware event filtering in the FPGA allows event rates up to 1 Mevents/s by disentangling of two events occurring within the delay line time length of e.g. 250 ns . Whilst list mode data are recorded with full rate and full resolution on the host PC disk, 1D–3D histograms can be accumulated online in the on-board HM for a fraction of the data and with reduced resolution.

Charge Amplification of GEM-Based Gas Deiedors

The operation of a gas electron multiplier (GEM) detector equipped with a multiwire proportional chamber (MWPC) or a micro strip gas chamber (MSGC) was examined. The additional gain provided by the GEM permitted the operation of the combined detector at substantially reduced voltages, thus increasing its reliability. The GEM + MWPC detector showed a very good gain uniformity of 2% variation throughout the active detector area. The single GEM detector achieved effective gains of above 3 000 with pure Ar by the effect of avalanche confinement.

Investigations of cerebral glucose utilization into the newborn brain: A [18F]-FDG positron emission tomography study using a high resolution multiwire proportional chamber detector device

An experimental approach is presented, where for the first time positron emission tomography (PET, the most important method for in vivo measuring the key functions of brain physiology and metabolism) was applied together with other techniques for quantitative-topological estimation of key parameters such as rCMRGlu in normal and disturbed brain function states in the newborn period.

Development of calorimeters using thin chambers operating in a high gain mode

A new type of thin multiwire proportional chamber detector operating in a high gain mode has been developed. Its characteristics have been optimized for calorimetric use. Two setups consisting of ten such detectors (electromagnetic calorimeter) interlaced with lead plates of 6 mm thickness and with iron plates of 8 cm thickness (hadron calorimeter) were tested. The characteristics of these detectors operating in calorimetric environments have been investigated and compared with theoretical expectations.

Production of cobalt-55, a short-lived, positron emitting radiolabel for bleomycin

The production and radiochemical separation of 55Co from deuteron irradiation of enriched 54Fe target is described. Methods used for the recovery and reuse of the target material ( 54Fe) are also described. The yield of 55Co at 12 MeV incident deuteron energy is 1.7 mCi per μAh at end of bombardment and the contamination with 57Co is 0.016%. The 55Co produced is chelated to bleomycin and used for tumour imaging with a positron emission tomographic camera based on multi-wire proportional chamber detectors.

A memory-level decision for a 50 000-wire proportional-chamber detector

A memory-level decision logic used at the CERN-ISR Split Field Magnet Detector is described. 50000 wires of the multi-wire proportional chamber detector are grouped into 32-wire memory OR levels, corresponding to 64 mm space resolution. From their pattern, the topology of specific events is defined. The rejection power for wrong events is of the order of 10 2 to 10 3. The decision time is about 1 μs.

Operation system for a 50 000-wire proportional chamber detector

A multiparticle spectrometer at the CERN Intersecting Storage Rings is equipped with a multiwire proportional chamber detector. In this paper we describe trigger, data acquisition, and monitor system of the detector.

Coded Aperture Imaging of Gamma-Rays Using Multiple Pinhole Arrays and Multiwire Proportional Chamber Detector

Coded shadows of gamma-ray distributions have been made using both random pinhole and non-redundant pinhole coded apertures with a multiwire proportional chamber as detector. Image reconstruction is done optically with incoherent light. Lateral and depth resolution results are presented and calculations of background and signal to noise ratios for the nonredundant aperture are made and compared with the single pinhole collimator.

Measurements ofdpbackward elastic scattering at 3.43, 4.50, 5.75, and 6.60GeVcincident deuteron momentum

Differential cross sections for $\mathrm{dp}$ elastic scattering from 60\ifmmode^\circ\else\textdegree\fi{} to 175\ifmmode^\circ\else\textdegree\fi{} center of momentum (c.m.) were measured at 3.43, 4.50, 5.75, and 6.60 $\frac{\mathrm{GeV}}{c}$ incident deuteron momentum. The measurements were made with a two-arm magnetic spectrometer, making use of multiwire proportional chamber detectors. The deuterons were accelerated at the Bevatron of the Lawrence Berkeley Laboratory. Data are compared with predictions of the baryon-pickup model and the one-pion-exchange model. The backward dip at 180\ifmmode^\circ\else\textdegree\fi{} c.m. for 4.5 $\frac{\mathrm{GeV}}{c}$, predicted by Craigie and Wilkin using the one-pion-exchange model, is not observed, but reasonable fits to the momentum variation and angular distributions are found. When the data are plotted against the variable $\ensuremath{\Delta}$ of the baryon-pickup model, the $s$ dependence is greatly reduced.