Anticoincidence Measurements Research Articles

Activity measurements of the radionuclides 18F, 64Cu, 99mTc and 11C for the NRC, Canada, in the ongoing comparisons BIPM.RI(II)-K4 series and KCRV update in the corresponding BIPM.RI(II)-K1 comparison

Main textIn 2017, comparisons of activity measurements of 18F, 64Cu, 99mTc and 11C using the Transfer Instrument of the International Reference System (SIRTI) took place at the National Research Council of Canada (NRC, Canada). Ampoules containing 18F, 64Cu, 99mTc and 11C solutions were measured in the SIRTI for about three half-lives (10 half-lives for 11C). The NRC standardized the activity in the ampoules by 4π(PC)β−γ anti-coincidence measurements (CIEMAT/NIST liquid scintillation counting for 11C). The comparisons, identifiers BIPM.RI(II)-K4.F-18, BIPM.RI(II)-K4.Cu-64 and BIPM.RI(II)-K4.Tc-99m are linked to the corresponding BIPM.RI(II)-K1.F-18, BIPM.RI(II)-K1.Cu-64 and BIPM.RI(II)-K1.Tc-99m comparisons. The BIPM.RI(II)-K1 18F and 99mTc key comparison reference values have been updated to include the latest BIPM.RI(II)-K4 linked results and degrees of equivalence for those three comparisons have been evaluated.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Design of a Time Discriminator in a Low-background, Anti- Compton Spectrometer

Compton scattering leads to the incomplete deposition of particle energy and produces a Compton scattering background, which decreases the measurement accuracy of low-energy rays. The low-background, anti-Compton spectrometer outputs 7-channel time signals through coincidence detector. The Compton events can be identified and reduced by the inverse coincidence of these time signals with the energy signals coming from the High Purity Germanium (HPGe) Detector. The precise-time measurement circuit can pulse shape the signal from the coincidence detector and accurately draw the arrival time of the signal. This is the key for a low-background, Compton-suppressed spectrometer to realize accurate anticoincidence measurements. In this study, a constant fraction discriminator (CFD) circuit was designed to replace the traditional leading-edge timer. A constant fraction discriminator-based all-pass filter without a delay line was used as the delay module. The advantages of the proposed method include the integration of circuits, low power consumption, and low cost. The simulation nuclear signals with different amplitudes, which were measured using the proposed CFD design, were outputted using the signal generator. The maximum deviation of the circuit triggering ratio was 2.5% and time jitter was 1.6 ns. The anti-Compton spectrometer with constant fraction discriminator has good Compton suppression effect. The peak-to-Compton ratio of the Compton-suppressed spectra is 1333:1 and the Compton-suppressed coefficient is 6.3.

Standardization of 59Fe by efficiency extrapolation 4πβ-γ anticoincidence method

A solution of 59Fe was standardized in the frame of a Bureau International des Poids et Mesures (BIPM) international key-comparison piloted by Asian Pacific Metrology Program (APMP) regional metrology organization. The method used was the live-timed 4πβ-γ anticoincidence counting with extended dead-time with efficiency extrapolation method. The confirmation of these results was performed by conventional 4πβ-γ coincidence counting with efficiency extrapolation and CIEMAT/NIST liquid scintillation counting methods. The value of the evaluated anticoincidence measurement was used to calibrate the LNMRI second standard ionization chambers for providing 59Fe solutions to nuclear medicine canters in the procedures of anaemia diagnosis. Besides this value was adopted as the comparison value of LNMRI and sent to APMP organization. The half-life of 59Fe was determined following the decay of one ampoule sample with 59Fe solution in an ionization chamber (Centronic model IG12).

Activity measurements of the radionuclides 18F and 64Cu for the NIST, USA in the ongoing comparisons BIPM.RI(II)-K4.F-18 and BIPM.RI(II)-K4.Cu-64

In 2016, comparisons of activity measurements of 18F and 64Cu using the Transfer Instrument of the International Reference System (SIRTI) took place at the National Institute of Standards and Technology (NIST, USA). This is the first SIRTI comparison for 64Cu. Ampoules containing about 27 kBq of 18F and 100 kBq of 64Cu solutions were measured in the SIRTI for about 5 and 1.5 half-lives, respectively. The NIST standardized the activity in the ampoules by ionization chamber measurements traceable to 4π(LS)β−γ anticoincidence measurements. The comparisons, identifiers BIPM.RI(II)-K4.F-18 and BIPM.RI(II)-K4.Cu-64, are linked to the corresponding BIPM.RI(II)-K1.F-18 and BIPM.RI(II)-K1.Cu-64 comparisons and degrees of equivalence with the respective key comparison reference values have been evaluated. The NIST replaces its earlier degree of equivalence for 18F obtained in the frame of the CCRI(II)-K3.F-18 comparison in 2001.Main textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

A novel natural environment background model for Monte Carlo simulation and its application in the simulation of anticoincidence measurement

This study proposes a novel natural environment background model by modeling brief environment conditions. It uses Geant4 program to simulate decays of 238U, 232Th, and 40K in soil and obtains compositions of different-energy gamma rays in the natural environment background. The simulated gamma spectrum of the natural environment background agrees well with the experimental spectrum, particularly above 250keV. The model is used in the simulation of anticoincidence measurement, indicating that the natural environment background can be decreased by approximately 88%, and the Compton attenuation factor is 2.22. The simulation of anticoincidence measurement can improve the minimum detectable activity (MDA) of the detection system.

A Reconfigurable Instrument System for Nuclear and Particle Physics Experiments

We developed a reconfigurable nuclear instrument system (RNIS) that could satisfy the requirements of diverse nuclear and particle physics experiments, and the inertial confinement fusion diagnostic. Benefiting from the reconfigurable hardware structure and digital pulse processing technology, RNIS shakes off the restrictions of cumbersome crates and miscellaneous modules. It retains all the advantages of conventional nuclear instruments and is more flexible and portable. RNIS is primarily composed of a field programmable hardware board and relevant PC software. Separate analog channels are designed to provide different functions, such as amplifiers, ADC, fast discriminators and Schmitt discriminators for diverse experimental purposes. The high-performance field programmable gate array could complete high-precision time interval measurement, histogram accumulation, counting, and coincidence anticoincidence measurement. To illustrate the prospects of RNIS, a series of applications to the experiments are described in this paper. The first, for which RNIS was originally developed, involves nuclear energy spectrum measurement with a scintillation detector and photomultiplier. The second experiment applies RNIS to a G-M tube counting experiment, and in the third, it is applied to a quantum communication experiment through reconfiguration.

Anticoincidence measurement of 57Fe Mössbauer spectra obtained after 57Mn implantation: application to Fe in α-Al2O3

A new detection system was developed using a gas-filled resonance counter operated in anticoincidence with a plastic scintillation detector for 57Fe Mossbauer spectroscopy using a short-lived 57Mn (T1/2 = 1.45 min) beam. We have succeeded in measuring 57Fe Mossbauer spectra obtained after 57Mn implantation into single-crystalline α-Al2O3 at 92, 193, and 298 K, with an adequate ratio of the resonance peak against the background by applying this detection system, in spite of the extremely low implantation dose. Final positions of Fe atoms in α-Al2O3 are discussed and compared with the results of the ab initio density functional calculations.

Statistical analysis of testing of an entangled state based on the Poisson distribution framework

A hypothesis testing scheme for entanglement has been formulated based on the Poisson distribution framework instead of the positive operator valued measure (POVM) framework. Three designs were proposed to test the entangled states in this framework. The designs were evaluated in terms of the asymptotic variance. It has been shown that the optimal time allocation between the coincidence and anti-coincidence measurement bases improves the conventional testing method. The test can be further improved by optimizing the time allocation between the anti-coincidence bases.

Simplified slow anti-coincidence circuit for Compton suppression systems

Slow coincidence circuits for the anti-coincidence measurements have been considered for use in Compton suppression technique. The simplified version of the slow circuit has been found to be fast enough, satisfactory and allows an easy system setup, particularly with the advantage of the automatic threshold setting of the low-level discrimination. A well-type NaI detector as the main detector surrounded by plastic guard detector has been arranged to investigate the performance of the Compton suppression spectrometer using the simplified slow circuit. The system has been tested to observe the improvement in the energy spectra for medium to high-energy gamma-ray photons from terrestrial and environmental samples.

Hypothesis testing for an entangled state produced by spontaneous parametric down-conversion

Generation and characterization of entanglement are crucial tasks in quantum information processing. A hypothesis testing scheme for entanglement has been formulated. Three designs were proposed to test the entangled photon states created by the spontaneous parametric down conversion. The time allocations between the measurement vectors were designed to consider the anisotropic deviation of the generated photon states from the maximally entangled states. The designs were evaluated in terms of the p-value based on the observed data. It has been experimentally demonstrated that the optimal time allocation between the coincidence and anti-coincidence measurement vectors improves the entanglement test. A further improvement is also experimentally demonstrated by optimizing the time allocation between the anti-coincidence vectors. Analysis on the data obtained in the experiment verified the advantage of the entanglement test designed by the optimal time allocation.

Absolute radioactivity measurement of 60Co, 134Cs and 166mHo by 4 πβ− γ anti-coincidence method

A 4 πβ− γ anti-coincidence system has been developed for absolute radioactivity measurements with a HPGe γ-spectrometer used as the γ-ray detector and a 4 πβ proportional counter as the β detector. The activity of 60Co, 134Cs and 166mHo have been measured with the combined standard uncertainties of 0.24%, 0.33% and 0.44%, respectively. Compared with the results of the National Institute of Metrology and 4 πβ− γ coincidence counting system of the China Institute of Atomic Energy, the agreement of the results of 60Co and 134Cs is satisfactory. For 166mHo, the results obtained using other methods by most national and international labs lack sufficient accuracy due to the complex decay scheme of this radio-nuclide. It is also concluded that the result of anti-coincidence measurement is independent of β efficiency.

Coincidence and anti-coincidence measurements in prompt gamma neutron activation analysis with pulsed cold neutron beams

A novel approach is implemented to alleviate some persistent problems in neutron capture prompt gamma activation analysis (PGAA). Detection sensitivities of PGAA are often restricted by the following factors: poor signal to noise ratios, interferences from background signals, and, in some cases, overlapping energy lines from different origins, namely ultra short-lived decay lines interfering with prompt decay. Timing the gamma-ray acquisition with the actual capture events using a pulsed beam of cold neutrons allows discrimination between prompt and delayed emissions from a sample source as well as against background events. Coincidence gating selects the prompt gamma-ray emissions. Contributions of background capture gamma-rays are suppressed because of different flight times of neutrons to the sources of background radiation, providing a reduction in direct gamma-ray interferences. Anti-coincidence gating allows measurement of only decay radiation that originates from short-lived activated states of the nuclides after capture. Spectra of decaying nuclides are free of interfering prompt activities, as well as have lower continuum background from Compton scattering of high-energy prompt gamma-rays in the detector. The measurements provide the opportunity to use ultra-short half-life nuclides for analytical purposes, no sample transfer times are lost, and repetitive activation and counting cycles are achieved with the use of pulsed neutron beams.

Some comments on the two prism tunnelling experiment

We show that the two prism tunnelling experiment of Mizobuchi and Ohtake [Phys. Lett. A 168 (1992) 1] does not verify the quantum optical prediction due to insufficient statistical precision in the anticoincidence measurement. We reanalyze their data and show that the observed number of coincidences is actually even larger than what is expected from a classical coherent light source.

High amplitude events in microchannel plates

Measurements have been made to determine the characteristics of high-amplitude events in microchannel plates (MCPs). The background-pulse-amplitude spectrum is found to extend to >30x to MCP modal gain. The majority of the background events are initiated by /sup 40/K beta decay in the MCP glass. However, up to 40% of the events are due to cosmic rays. Comparison of background pulse-amplitude spectra for horizontal and vertical MCP orientations suggests that the largest events are predominantly cosmic-ray-induced. Anticoincidence measurements confirm this result. A model describing the /sup 40/K beta decay and cosmic-ray interactions in the MCP predicts spectra in accord with these observations. The response of MCPs subjected to simultaneous multiphoton input was also determined, showing that pulse amplitudes many times the modal gain are possible event though the response becomes nonlinear at high amplitudes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Background events in microchannel plates

Measurements have been made to assess the characteristics and origins of background events in microchannel plates (MCPs). An overall background rate of approximately 0.4 events cm/sup -3/-s/sup -1/ has been achieved consistently for MCPs that have been baked and scrubbed. The temperature and gain of the MCPs are found to have no significant effect on the background rate. Detection of 1.46-MeV gamma rays from the MCP glass confirms the presence of /sup 40/K, with a concentration of 0.0007%, in MCP glass. It is shown that beta decay from /sup 40/K is sufficient to cause the background rate and spectrum observed. Anticoincidence measurements indicate the background rate caused by cosmic ray interactions is small ( >

Nuclear Structure Study of 150Sm. II. Decay of 150Pm

Energies and relative intensities of gamma transitions following the decay of 150 Pm were measured with Ge(Li) detectors and 94 gamma rays were observed. The half-life of 150 Pm was determined to be 161.9±0.9 min. Gamma-gamma coincidence and gamma-gamma anticoincidence measurements were performed. From these measurements the 1670 keV, 2371 keV and 2700 keV levels are proposed and the 2679 keV level is excluded. From beta-gamma coincidence measurements the beta-ray feeding to the ground state was found. By using a \(\sqrt{2}\pi\) beta-ray spectrometer, the beta-ray maximum energy of the transition to the first excited state was determined to be 3120±20 keV and the intensity ratio of the ground-state transition to this transition was 0.0858±0.0043. From gamma-gamma angular correlation measurements E2/M1 or M2/E1 mixing ratios of several gamma rays were obtained.

Decay of 1.65-hRu95to Levels inTc95

The level structure of $^{95}\mathrm{Tc}$ has been investigated from the decay of 1.65-h $^{95}\mathrm{Ru}$. Singles $\ensuremath{\gamma}$-ray energy and intensity measurements were taken with a 42-${\mathrm{cm}}^{3}$ high-resolution Ge(Li) detector in an anti-Compton arrangement which employed a large NaI(Tl) annular detector. Energies and intensities have been determined for 81 $\ensuremath{\gamma}$ rays which have been observed to decay with the half-life of the $^{95}\mathrm{Ru}$ isotope. Extensive $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence Ge(Li)-Ge(Li) measurements have been utilized to establish $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence relationships. The transitions to the ground and metastable state were identified from Ge(Li)-NaI(Tl) anticoincidence measurements. A decay scheme accommodating 71 transitions between 21 levels is proposed. The levels at 2168.2, 2189.0, 2267.5, and 2382.0 keV have not previously been reported. From deduced $log\mathrm{ft}$ values and measured $\ensuremath{\gamma}$-ray branching ratios definite ${J}^{\ensuremath{\pi}}$ assignments were made to a number of levels and limits for the ${J}^{\ensuremath{\pi}}$ values were placed for the rest of the levels in $^{95}\mathrm{Tc}$. The level structure of the $^{95}\mathrm{Tc}$ isotope is examined and compared with spectra derived on the basis of extended pairing-plus-quadrupole and shell-model calculations.