A single crystal chemical vapor deposition diamond-based microdosimeter prototype featuring an array of micro-sensitive volumes (μSVs) and surrounded by a so-called guard ring (GR) electrode has been ...fabricated using various microfabrication techniques available at Diamond Sensors Laboratory of CEA, Saclay. The GR microdosimeter was irradiated by a raster scanning method with 2 MeV proton microbeams. The charge transport properties of the GR sensor were determined with sub-micron spatial resolution by measuring the charge collection efficiency (CCE), the μSV geometry, and the pulse-height spectra. The response of the microdosimeter showed a well-defined and homogeneously active μSV. Appropriate biasing of the μSV structures led toward a full CCE for protons with lineal energies of ∼46 keV/μm. This shows the GR microdosimeter's great potential for applications in microdosimetry in clinical beam conditions.
Small diamond detectors are useful for the dosimetry of high-energy proton beams. However, linear energy transfer (LET) dependence has been observed in the literature with such solid state detectors. ...A novel synthetic diamond detector has recently become commercially available from the manufacturer PTW-Freiburg (PTW microDiamond type 60019). This study was designed to thoroughly characterize four microDiamond detectors in clinical proton beams, in order to investigate their response and their reproducibility in high LET regions. Very good dosimetric characteristics were observed for two of them, with good stability of their response (deviation less than 0.4% after a pre-irradiation dose of approximately 12 Gy), good repeatability (coefficient of variation of 0.06%) and a sensitivity of approximately 0.85 nC Gy(-1). A negligible dose rate dependence was also observed for these two microDiamonds with a deviation of the sensitivity less than 0.7% with respect to the one measured at the reference dose rate of 2.17 Gy min(-1), in the investigated dose rate range from 1.01 Gy min(-1) to 5.52 Gy min(-1). Lateral dose profile measurements showed the high spatial resolution of the microDiamond oriented with its stem perpendicular to the beam axis and with its small sensitive thickness of about 1 μm in the scanning profile direction. Finally, no significant LET dependence was found with these two diamond dosimeters in comparison to a reference ionization chamber (model IBA PPC05). These good results were in accordance to the literature. However, this study showed also a non reproducibility between the devices in terms of stability, sensitivity and LET dependence, since the two other microDiamonds characterized in this work showed different dosimetric characteristics making them not suitable for proton beam dosimetry with a maximum difference of the peak-to-plateau ratio of 6.7% relative to the reference ionization chamber in a clinical 138 MeV proton beam.
Using the advantage of the high spatial resolution of the Ruđer Bošković Institute (RBI) ion microprobe, small areas of a thin membrane single crystal chemical vapor deposition (scCVD) diamond ...detector were intentionally damaged with a high-intensity 26-MeV oxygen ion beam at various fluences, producing up to ∼1018 vacancies/cm3. The response of the detector was tested with the ion beam-induced charge technique (IBIC) using a 2-MeV proton beam as a probe. The signal amplitudes decreased down to approximately 50% of the original value at low electric fields (<10 V/μm) inside the detector. However, the increase of electric field to values of ∼100 V/μm completely recovers the signal amplitude. The results presented herein can facilitate the development of true radiation hard particle detectors.
The PICOSEC Micromegas detector can time the arrival of Minimum Ionizing Particles with a sub-25 ps precision. A very good timing resolution in detecting single photons is also demonstrated in laser ...beams. The PICOSEC timing resolution is determined mainly by the drift field. The arrival time of the signal and the timing resolution vary with the size of the pulse amplitude.
Detailed simulations based on GARFIELD++ reproduce the experimental PICOSEC timing characteristics. This agreement is exploited to identify the microscopic physical variables, which determine the observed timing properties. In these studies, several counter-intuitive observations are made for the behavior of such microscopic variables. In order to gain insight on the main physical mechanisms causing the observed behavior, a phenomenological model is constructed and presented. The model is based on a simple mechanism of “time-gain per interaction” and it employs a statistical description of the avalanche evolution. It describes quantitatively the dynamical and statistical properties of the microscopic quantities, which determine the PICOSEC timing characteristics, in excellent agreement with the simulations. In parallel, it offers phenomenological explanations for the behavior of these microscopic variables. The formulae expressing this model can be used as a tool for fast and reliable predictions, provided that the input parameter values (e.g. drift velocities) are known for the considered operating conditions.
The development of CVD grown single-crystal Diamond-on-Iridium (DOI) sensors for charged-particle detection in hadrons and nuclei physics research is reviewed. A variety of samples grown at the ...University of Augsburg has been investigated with α and β sources in the laboratory, swift ions from the heavy-ion synchrotron SIS in Darmstadt, and relativistic protons from the COoler-SYnchrotron COSY in Jülich. The results obtained by means of I-E(V) studies, transient-current techniques (TCT), α-spectroscopy, and heavy-ion time-of-flight (ToF) measurements are compared to those of commercially available polycrystalline and homoepitaxial single crystal CVD diamond sensors of electronic grade quality.
In many aspects, the performance of DOI sensors was found quite similar to that of homoepitaxial counters, and in any case far superior to that of polycrystalline detectors. Under single-carrier drift conditions, the CCE and energy resolution (δE/E) for holes reached levels CCEh > 95% and δE/Eh ~ 0.3%, respectively, which correspond to values of the Schubweg wh,e well above the detector thickness. In contrast, the CCEe for electrons was typically lower than ~40%, leading to appreciable reduction of the detection efficiency in the dual-carrier drift mode (CCE ~ 60%), which characterizes the experiments with swift heavy ions and high-energy particles. We measured transport parameters comparable to those of homoepitaxial devices: μ0h ~ 3080–1756 and μ0e ~ 2276–1150 cm2/Vs, vsath ~ (1.7–1.4) ∗ 107 and vsate ~ (1.5–1.0) ∗ 107 cm/s, as well as intrinsic time resolutions σi ~ 15 ps. It is shown, that substantial improvements have been achieved in recent years, albeit reproducibility and the understanding of the reduced electron collection remain challenging issues.
Prime novelty: Comprehensive electrical characterization of intrinsic single-crystal CVD Diamond-On-Iridium sensors produced at the University of Augsburg and their classification into the range of commercial electronic grade polycrystalline and homoepitaxial diamond sensors supplied by Element Six.
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•Comprehensive study exploring detector properties and perspectives of CVD Diamond-on-Iridium (DOI) produced in Augsburg.•DOI sensors are compared with commercial poly (PCD) and single-crystal CVD-diamond (SCD) samples supplied by Element Six.•The excellent drift and collection properties at h-drift enable particle timing and spectroscopy.•DOI sensors are clearly outperforming PCD counters.•The results indicate a high potential of heteroepitaxial diamond grown on Ir/YSZ/Si(001) for large-area detector systems.
We determine for the first time the magnetic dipole moment of a short-lived nucleus with part-per-million (ppm) accuracy. To achieve this 2-orders-of-magnitude improvement over previous studies, we ...implement a number of innovations into ourβ-detected nuclear magnetic resonance (β-NMR) setup at ISOLDE at CERN. Using liquid samples as hosts, we obtain narrow, subkilohertz-linewidth, resonances, while a simultaneous in situH1NMR measurement allows us to calibrate and stabilize the magnetic field to ppm precision, thus eliminating the need for additionalβ-NMR reference measurements. Furthermore, we use ab initio calculations of NMR shielding constants to improve the accuracy of the reference magnetic moment, thus removing a large systematic error. We demonstrate the potential of this combined approach with the 1.1 s half-life radioactive nucleusNa26, which is relevant for biochemical studies. Our technique can be readily extended to other isotopic chains, providing accurate magnetic moments for many short-lived nuclei. Furthermore, we discuss how our approach can open the path toward a wide range of applications of the ultrasensitiveβ-NMR in physics, chemistry, and biology.
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