Proton-recoil detectors offer the possibility to unfold fast-neutron energy spectra of various sources. However, quantifying the confidence of the unfolding methodology is a complex task. In this ...paper, we present a comparative analysis of the maximum-likelihood, expectation-maximization (MLEM) method and one-step-late (OSL) method for neutron energy spectra unfolding. The analysis is performed on Monte Carlo simulated data for several monoenergetic neutron sources and continuous-in-energy 252Cf, 241Am–Be and 241Am–Li neutron sources. The results obtained for the monoenergetic neutron spectra show that both unfolding methods provide results that are in good agreement with the reference data. Very good agreement between the unfolded and the reference data is achieved for 252Cf, 241Am–Be, and 241Am–Li neutron spectra by using the OSL method. In the paper it is demonstrated that the MLEM and OSL methods can be applied to accurately unfold the simulated pulse-height distributions for organic liquid scintillation detectors. Comparative analysis between the two unfolding methods has shown that the OSL method has superior unfolding performance than the MLEM method.
► Proton-recoil detectors offer the possibility to unfold fast-neutron energy spectra. ► Pulse height distributions simulated by the MCNP-Polimi code. ► Maximum-Likelihood Expectation Maximization (MLEM), one-step-late (OSL) methods. ► Unfolding of monoenergetic and continuous-in-energy neutron sources. ► Study has shown the OSL method has superior unfolding performance to the MLEM method.
Compact source of narrowband and tunable X-rays for radiography Banerjee, Sudeep; Chen, Shouyuan; Powers, Nathan ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
05/2015, Letnik:
350, Številka:
C
Journal Article
Recenzirano
Odprti dostop
We discuss the development of a compact X-ray source based on inverse-Compton scattering with a laser-driven electron beam. This source produces a beam of high-energy X-rays in a narrow cone angle ...(5–10mrad), at a rate of 108photons-s−1. Tunable operation of the source over a large energy range, with energy spread of ∼50%, has also been demonstrated. Photon energies >10MeV have been obtained. The narrowband nature of the source is advantageous for radiography with low dose, low noise, and minimal shielding.
Typically, when neutron coincidence or multiplicity counting is performed, there are three unknowns: the sample mass, the leakage self-multiplication, and the ratio of the (α,n) rate of the source to ...the spontaneous fission rate. For a given counting time, the strength of the source or the detector efficiency must be sufficiently high for the singles, doubles, and triples count rates to represent statistically meaningful quantities. Often, the strength of the source and the allotted counting time are such that only the singles and doubles count rates are statistically meaningful. In this latter case, the ratio of (α,n) to the spontaneous fission must be estimated through some other means. With a simulated (α,n) rate, the two equations related to the singles and doubles count rates can be used to determine the sample mass. In order to determine the ratio of (α,n) to spontaneous fission rate of the source, the isotopic composition of the sample as well as the light element impurities inside the source must be known. Ideally, there would be a way to dynamically determine the (α,n) rate of the source from count rate information. In this paper, it is shown that the (α,n) rate of the source can be determined by using information about the ratio of the number of coincident neutrons at 180° to the number at 90°. By using this information, the three aforementioned unknowns can be dynamically determined through the sole use of singles and doubles count rates.
Purpose:
The primary objective of this work is to measure the secondary neutron field produced by an uncollimated proton pencil beam impinging on different tissue-equivalent phantom materials using ...organic scintillation detectors. Additionally, the Monte Carlo code mcnpx-PoliMi was used to simulate the detector response for comparison to the measured data. Comparison of the measured and simulated data will validate this approach for monitoring secondary neutron dose during proton therapy.
Methods:
Proton beams of 155- and 200-MeV were used to irradiate a variety of phantom materials and secondary particles were detected using organic liquid scintillators. These detectors are sensitive to fast neutrons and gamma rays: pulse shape discrimination was used to classify each detected pulse as either a neutron or a gamma ray. The mcnpx-PoliMi code was used to simulate the secondary neutron field produced during proton irradiation of the same tissue-equivalent phantom materials.
Results:
An experiment was performed at the Loma Linda University Medical Center proton therapy research beam line and corresponding models were created using the mcnpx-PoliMi code. The authors’ analysis showed agreement between the simulations and the measurements. The simulated detector response can be used to validate the simulations of neutron and gamma doses on a particular beam line with or without a phantom.
Conclusions:
The authors have demonstrated a method of monitoring the neutron component of the secondary radiation field produced by therapeutic protons. The method relies on direct detection of secondary neutrons and gamma rays using organic scintillation detectors. These detectors are sensitive over the full range of biologically relevant neutron energies above 0.5 MeV and allow effective discrimination between neutron and photon dose. Because the detector system is portable, the described system could be used in the future to evaluate secondary neutron and gamma doses on various clinical beam lines for commissioning and prospective data collection in pediatric patients treated with proton therapy.
RES-NOVA is a newly proposed experiment for detecting neutrinos from astrophysical sources, mainly Supernovae, using an array of cryogenic detectors made of PbWO
4
crystals produced from ...archaeological Pb. This unconventional material, characterized by intrinsic high radiopurity, enables low-background levels in the region of interest for the neutrino detection via Coherent Elastic neutrino-Nucleus Scattering (CE
ν
NS). This signal lies at the detector energy threshold,
O
(1 keV), and it is expected to be hidden by naturally occurring radioactive contaminants of the crystal absorber. Here, we present the results of a radiopurity assay on a 0.84 kg PbWO
4
crystal produced from archaeological Pb operated as a cryogenic detector. The crystal internal radioactive contaminations are:
232
Th <40
μ
Bq/kg,
238
U <30
μ
Bq/kg,
226
Ra 1.3 mBq/kg and
210
Pb 22.5 mBq/kg. We also present a background projection for the final experiment and possible mitigation strategies for further background suppression. The achieved results demonstrate the feasibility of realizing this new class of detectors.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The CUPID-Mo experiment to search for 0
ν
β
β
decay in
100
Mo has been recently completed after about 1.5 years of operation at Laboratoire Souterrain de Modane (France). It served as a demonstrator ...for CUPID, a next generation 0
ν
β
β
decay experiment. CUPID-Mo was comprised of 20 enriched
Li
2
100
MoO
4
scintillating calorimeters, each with a mass of
∼
0.2
kg, operated at
∼
20
mK. We present here the final analysis with the full exposure of CUPID-Mo (
100
Mo exposure of 1.47
kg
×
year
) used to search for lepton number violation via 0
ν
β
β
decay. We report on various analysis improvements since the previous result on a subset of data, reprocessing all data with these new techniques. We observe zero events in the region of interest and set a new limit on the
100
Mo 0
ν
β
β
decay half-life of
T
1
/
2
0
ν
>
1.8
×
10
24
year (stat. + syst.) at 90% CI. Under the light Majorana neutrino exchange mechanism this corresponds to an effective Majorana neutrino mass of
m
β
β
<
(
0.28
-
0.49
)
eV, dependent upon the nuclear matrix element utilized.
When simulating the response of a particle detector to an energy deposition, the pulse shape and the electronic noise are important features to be taken into account. In this work, we present a ...method to simulate a continuous stream of detector-like data, produced to mock the salient characteristics of the chosen setup. This technique allows the full reproduction of an experimental measurement, as well as providing a predictive tool to validate or train new analysis procedures. We present the algorithm used to produce these data, and we test its capabilities by reproducing the data output of an high-purity germanium detector.
Sterile neutrinos are a minimal extension of the standard model of particle physics. A promising model-independent way to search for sterile neutrinos is via high-precision β-spectroscopy. The ...Karlsruhe tritium neutrino (KATRIN) experiment, equipped with a novel multi-pixel silicon drift detector focal plane array and read-out system, named the TRISTAN detector, has the potential to supersede the sensitivity of previous laboratory-based searches. In this work we present the characterization of the first silicon drift detector prototypes with electrons and we investigate the impact of uncertainties of the detector's response to electrons on the final sterile neutrino sensitivity.
A total of 46 patients with primary myelofibrosis (PMF) (median age 51 years), underwent an allogeneic hemopoietic SCT (HSCT) after a thiotepa-based reduced-intensity conditioning regimen. The median ...follow-up for surviving patients is 3.8 years. In multivariate analysis, independent unfavorable factors for survival were RBC transfusions >20, a spleen size >22 cm and an alternative donor-24 patients had 0-1 unfavorable predictors (low risk) and 22 patients had 2 or more negative predictors (high risk). The overall actuarial 5-year survival of the 46 patients is 45%. The actuarial survival of low-risk and high-risk patients is, respectively, 77 and 8% (P<0.0001); this is because of a higher TRM for high-risk patients (RR, 6.0, P=0.006) and a higher relapse-related death (RR, 7.69; P=0.001). In multivariate Cox analysis, the score maintained its predictive value (P=0.0003), even after correcting for donor-patient age and gender, Dupriez score, IPSS (International Prognostic Scoring System) score pre-transplant and splenectomy. In conclusion, PMF patients undergoing an allogeneic HSCT may be scored according to the spleen size, transfusion history and donor type; this scoring system may be useful to discuss transplant strategies.
We have experimentally characterized the neutron light output response functions of a deuterated-xylene scintillator for neutron energies lower than 10 MeV. We then used the response matrix to unfold ...the energy distribution of neutrons produced via several reactions, i.e., spontaneous fission, d(d,n) 3 He, 27 Al(d,n) 28 Si, and 9 Be(alpha,n) 12 C. Organic scintillators based on deuterated compounds show a fast response and good gamma-neutron discrimination capability, similar to or better than proton-based scintillators. Deuterated scintillators can also effectively provide neutron energy spectra by unfolding measured data with the detector response matrix, without the need of timeof-flight. Deuteron recoils, produced by elastic collisions between deuterium and impinging neutrons, are preferentially forwardscattered. This non-isotropic reaction results in distinct peaks in the response functions to monoenergetic neutrons. In this work, we evaluated a custom-fabricated 7.62 cm ×7.62 cm deuteratedxylene (EJ301D) liquid scintillator. This liquid has a low volatility and higher flash point, compared to benzene-based deuterated detectors, e.g., EJ315 and NE230. We measured the EJ301D detector neutron response matrix (up to 6 MeV neutron energy) using an intense 252 Cf source and the time-of-flight technique. The number of response functions obtained using our method is only limited by counting statistics and by the experimentally achievable energy resolution. Multi-channel unfolding was then performed successfully for neutron sources with different energy spectra.
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