Average energy dissipated by mega-electron-volt hydrogen and helium ions per electron-hole pair generation in 4H-SiC

The pulse height response for He and H ions with energies between 1 and 6 MeV incident upon n-type 4H-SiC epitaxial Schottky diodes has been investigated. The average amount of energy, ε, given up by the incident radiation to form electron-hole pair in this material was obtained by comparison with the average energy loss per pair in silicon detectors and it was found to be (7.78±0.05)eV at room temperature. This value is smaller than that foreseen by Klein's semiempirical linear relationship between ε and the semiconductor band gap

Performances of 4H-SiC Schottky diodes as neutron detectors

Abstract Large area 4H-SiC Schottky diodes equipped with a 6LiF converter were tested as neutron detectors in the epithermal column realized for Boron Neutron Capture Therapy (BNCT) applications at the fast reactor TAPIRO (ENEA Casaccia Roma). The neutron spectra were assessed using the Monte Carlo code MCNP-4C. The performances of SiC detectors were evaluated with neutron fluences in the range of 109–1013 cm−2 which is typical for BNCT. Spectra of alpha and tritium particles generated by 6Li(n,α)3H reaction were collected at various neutron fluences and spectra obtained by interposing polyethylene moderators of different thickness. Only weak damaging effects primarily due to the alpha particles were observed; at neutron fluence of 1013 cm−2 the count rate decreased b

Photocurrent study of beta-ray priming in CVD diamond

Priming by X-rays or by beta-rays is generally needed in order to qualify CVD diamond for nuclear detection or for dosimetry. The priming effect is usually attributed in filling the hole traps, which are responsible for the charge collection efficiency of the detector. Emptying the filled traps can be easily detected by Thermoluminescence (TL), which is considered to be a measure of the absorbed dose. In this work, we prove that below-gap photocurrent (BGPC) can also be used in the same way and it is dominated by the optical detrapping of holes from the same centers. Time dependence of this beta-rays induced persistent photocurrent (PPC), which in fact, depends only on the total number of photons impinging onto the sample. In fact, at long times or for large number of photons, the photocurrent approaches to the same limit of PC for a null dose. The hole trapping centers distribution seems to extend from 1.25 to 2.5 eV valence band

Lateral IBIC analysis of GaAs Schottky diodes

Abstract Charge collection efficiency (CCE) profiles of a semi-insulating (SI) gallium arsenide LEC (Liquid Encapsulated Czochralski) Schottky diode have been investigated by lateral Ion Beam Induced Charge collection (IBIC) technique. A focussed 2.4 MeV proton microbeam was scanned over the cleaved surface of a SI-GaAs diode and the charge collection efficiency was evaluated as a function of the ion beam position at different bias voltages. By fitting the CCE profiles with the equations derived by the Shockley–Ramo–Gunn's theorem, drift lengths of electrons and holes were obtained. Experimental results are consistent with previous OBIC (Optical Beam Induced Current) and SP (Surface Potential) measurements and confirm the model based on the formation of a Mott barrier due to the enhanced electron capture cross section in high field conditions

Comparing Long-Acting Antipsychotic Discontinuation Rates Under Ordinary Clinical Circumstances: A Survival Analysis from an Observational, Pragmatic Study

Background: Recent guidelines suggested a wider use of long-acting injectable antipsychotics (LAI) than previously, but naturalistic data on the consequences of LAI use in terms of discontinuation rates and associated factors are still sparse, making it hard for clinicians to be informed on plausible treatment courses. Objective: Our objective was to assess, under real-world clinical circumstances, LAI discontinuation rates over a period of 12 months after a first prescription, reasons for discontinuation, and associated factors. Methods: The STAR Network ‘Depot Study’ was a naturalistic, multicentre, observational prospective study that enrolled subjects initiating a LAI without restrictions on diagnosis, clinical severity or setting. Participants from 32 Italian centres were assessed at baseline and at 6 and 12 months of follow-up. Psychopathology, drug attitude and treatment adherence were measured using the Brief Psychiatric Rating Scale, the Drug Attitude Inventory and the Kemp scale, respectively. Results: The study followed 394 participants for 12 months. The overall discontinuation rate at 12 months was 39.3% (95% confidence interval [CI] 34.4–44.3), with paliperidone LAI being the least discontinued LAI (33.9%; 95% CI 25.3–43.5) and olanzapine LAI the most discontinued (62.5%; 95% CI 35.4–84.8). The most frequent reason for discontinuation was onset of adverse events (32.9%; 95% CI 25.6–40.9) followed by participant refusal of the medication (20.6%; 95% CI 14.6–27.9). Medication adherence at baseline was negatively associated with discontinuation risk (hazard ratio [HR] 0.853; 95% CI 0.742–0.981; p = 0.026), whereas being prescribed olanzapine LAI was associated with increased discontinuation risk compared with being prescribed paliperidone LAI (HR 2.156; 95% CI 1.003–4.634; p = 0.049). Conclusions: Clinicians should be aware that LAI discontinuation is a frequent occurrence. LAI choice should be carefully discussed with the patient, taking into account individual characteristics and possible obstacles related to the practicalities of each formulation