Cherenkov Components Research Articles

Estimation of the air shower depth of the maximum development by the relative fraction of muons and the composition of cosmic rays in the energy region E0≥5 EeV by Yakutsk array data

The paper presents joint analysis of the characteristics of the electron-photon and Cherenkov components, and muons with a threshold ${ϵ}_{\mathrm{thr}}\ensuremath{\ge}1\text{ }\text{ }\mathrm{GeV}$ and zenith angles less than 60\ifmmode^\circ\else\textdegree\fi{}. The analysis is based on complex data of air shower registration. A quantitative estimation of muons at different distances from the shower axis and the ratio of muons and charged particles at a distance of 600 m are obtained. The empirical relationship found between ${\ensuremath{\rho}}_{\ensuremath{\mu}}(600)/{\ensuremath{\rho}}_{\ensuremath{\mu}+e}(600)$ and the depth of the maximum ${X}_{\mathrm{max}}$ estimated by Cherenkov light data. It allowed to estimate ${X}_{\mathrm{max}}$ in individual showers by fraction of muons ${\ensuremath{\rho}}_{\ensuremath{\mu}}(600)/{\ensuremath{\rho}}_{\ensuremath{\mu}+e}(600)$. From the set of such showers, the dependence of ${X}_{\mathrm{max}}$ on the energy ${E}_{0}$ was found. Mass composition of cosmic rays with highest energies is estimated by comparison of the experimental ${X}_{\mathrm{max}}$ and QGSJetII-04 simulation ${X}_{\mathrm{max}}$ for different primary nuclei. The composition of cosmic rays determined from the muon component of air showers, mainly consists of protons and helium nuclei in the energy range 5--10 EeV. At energies greater than 30 EeV the mass composition is becoming heavier due to CNO and iron nuclei.

Cherenkov Radiation–Based Coincidence Time Resolution Measurements in BGO Scintillators

Bismuth germanate oxide (BGO) scintillators can be re-introduced in time-of-flight positron emission tomography (TOF-PET) by exploiting the Cherenkov luminescence emitted as a result from 511 keV interactions. Accessing the timing information from the relatively few emitted Cherenkov photons is now possible due to the recent improvements in enhanced near-ultraviolet high-density (NUV-HD) silicon photomultiplier (SiPM) technology, fast and low noise readout electronics, and the development of efficient data post-processing methods. In this work, we aim to develop a scalable detector element able to achieve excellent coincidence time resolution (CTR) required for TOF-PET using BGO scintillator elements of various lengths. The proposed detector element is optically coupled to 3.14 × 3.14 mm2 NUV-sensitive SiPMs mounted on a custom design circuit board. In particular, we have evaluated the CTR performance of BGO crystal elements of dimensions 3 × 3 × 3 mm3, 3 × 3 × 5 mm3, 3 × 3 × 10 mm3, and 3 × 3 × 15 mm3, with chemically etched surfaces and wrapped in Teflon tape. To achieve excellent CTR performance, we apply state-of-the-art post-processing methods during data analysis. Best values of 156 ± 6 ps, 188 ± 5 ps, 228 ± 8 ps, and 297 ± 8 ps CTR FWHM have been achieved for the 3, 5, 10, and 15 mm length BGO crystals, respectively. These values improve to 105 ± 6 ps, 127 ± 8 ps, 133 ± 4 ps, and 189 ± 8 ps CTR FWHM, when only considering the Cherenkov component of the timing signal, which is extracted by considering the events with the fastest rise time (20% of the total data). The accurate classification of the events based on their rise time is possible; thanks to the implementation of a dual threshold approach that sets the lower threshold below one light photon equivalent level and the upper one above the signal amplitude of a single photon avalanche diode (SPAD).

Light Extraction Enhancement Techniques for Inorganic Scintillators

Scintillators play a key role in the detection chain of several applications which rely on the use of ionizing radiation, and it is often mandatory to extract and detect the generated scintillation light as efficiently as possible. Typical inorganic scintillators do however feature a high index of refraction, which impacts light extraction efficiency in a negative way. Furthermore, several applications such as preclinical Positron Emission Tomography (PET) rely on pixelated scintillators with small pitch. In this case, applying reflectors on the crystal pixel surface, as done conventionally, can have a dramatic impact of the packing fraction and thus the overall system sensitivity. This paper presents a study on light extraction techniques, as well as combinations thereof, for two of the most used inorganic scintillators (LYSO and BGO). Novel approaches, employing Distributed Bragg Reflectors (DBRs), metal coatings, and a modified Photonic Crystal (PhC) structure, are described in detail and compared with commonly used techniques. The nanostructure of the PhC is surrounded by a hybrid organic/inorganic silica sol-gel buffer layer which ensures robustness while maintaining its performance unchanged. We observed in particular a maximum light gain of about 41% on light extraction and 21% on energy resolution for BGO, a scintillator which has gained interest in the recent past due to its prompt Cherenkov component and lower cost.

Photoluminescence of Dy3+ and Dy2+ in NaMgF3:Dy: A potential infrared radiophotoluminescence dosimeter

Infrared-emitting radiophotoluminescence centres were observed in NaMgF3:Dy in the form of stable Dy2+ ions that formed only after exposure to ionising radiation. Prior to irradiation, only Dy3+ luminescence could be seen. During radiation exposure, energetic electrons were captured by Dy3+ to form Dy2+, and the Dy2+ electron trap was approximately 3 eV deep and stable at room temperature. The large trap depth allowed for non-destructive probing of the Dy2+ photoluminescence via excitation into the lowest energy 5d state at 640 nm. Exciting into higher energy states at 340 nm resulted in ionisation of the trapped electrons, restoring the radiation-induced Dy2+ to Dy3+, and demonstrated that the material can be optically reset. The intraconfigurational 4f10 transitions of Dy2+ were compared with those of the isoelectronic Ho3+ ion in similar host compounds and attributed to specific transitions in all cases. The infrared radiophotoluminescence can potentially be used for real-time fibre optic dosimetry, as the Cherenkov component is significantly lower in the infrared when compared to emissions in the visible region.

Results From a Prototype Combination TPC Cherenkov Detector With GEM Readout

A combination Time Projection Chamber-Cherenkov prototype detector has been developed as part of the Detector R&D Program for a future Electron Ion Collider. The prototype was tested at the Fermilab test beam facility to provide a proof of principle to demonstrate that the detector is able to measure particle tracks and provide particle identification information within a common detector volume. The TPC portion consists of a 10x10x10cm3 field cage, which delivers charge from tracks to a 10x10cm2 quadruple GEM readout. Tracks are reconstructed by interpolating the hit position of clusters on an array of 2x10mm2 zigzag pads The Cherenkov component consists of a 10x10cm2 readout plane segmented into 3x3 square pads, also coupled to a quadruple GEM. As tracks pass though the drift volume of the TPC, the generated Cherenkov light is able to escape through sparsely arranged wires making up one side of the field cage, facing the CsI photocathode of the Cherenkov detector. The Cherenkov detector is thus operated in a windowless, proximity focused configuration for high efficiency. Pure CF4 is used as the working gas for both detector components, mainly due to its transparency into the deep UV, as well as its high N0. Results from the beam test, as well as results on its particle id capabilities will be discussed.

CLASSiC: Cherenkov light detection with silicon carbide

We present the CLASSiC R&D for the development of a silicon carbide (SiC) based avalanche photodiode for the detection of Cherenkov light.SiC is a wide-bandgap semiconductor material, which can be used to make photodetectors that are insensitive to visible light. A SiC based light detection device has a peak sensitivity in the deep UV, making it ideal for Cherenkov light. Moreover, the visible blindness allows such a device to disentangle Cherenkov light and scintillation light in all those materials that scintillate above 400nm.Within CLASSiC, we aim at developing a device with single photon sensitivity, having in mind two main applications. One is the use of the SiC APD in a new generation ToF PET scanner concept, using the Cherenov light emitted by the electrons following 511keV gamma ray absorption as a time-stamp. Cherenkov is intrinsically faster than scintillation and could provide an unprecedentedly precise time-stamp. The second application concerns the use of SiC APD in a dual readout crystal based hadronic calorimeter, where the Cherenkov component is used to measure the electromagnetic fraction on an event by event basis.We will report on our progress towards the realization of the SiC APD devices, the strategies that are being pursued toward the realization of these devices and the preliminary results on prototypes in terms of spectral response, quantum efficiency, noise figures and multiplication.

On the geomagnetic mechanism of the radiation of an extensive air shower

The radiation field of the elementary particles of an extensive air shower in the geomagnetic field has been examined. According to the solutions of Maxwell’s equation for an electron (positron) taking into account ionization losses, the radiation of the shower is determined only by the bremsstrahlung and geomagnetic mechanism. The Cherenkov component of radiation is almost absent.

Polarization as a tool for dual-readout calorimetry

It is shown that the signals from a high- Z scintillating crystal (BSO) can be separated into a scintillation and a Cherenkov component, by making use of the fact that the latter component is polarized. These studies were carried out in view of the possible application of such crystals in dual-readout calorimeters.

Formula omitted] Cherenkov light contribution to Hamamatsu S8148 and zinc sulfide–silicon avalanche photodiodes signals

Scintillation crystal–avalanche photodiode (APD) system is an important radiation detection technique. The lead tungstate ( PbWO 4 ) is one of the scintillation crystal used in high-energy physics experiments. The light generated in the PbWO 4 crystal could be split into scintillation and Cherenkov components. GEANT4 simulation of the light generated by high-energy particles in the PbWO 4 crystal shows that up to 20% of the light generated in the crystals is a result of the Cherenkov mechanism. The mean signals of the APDs were simulated by Single Particle Monte Carlo technique for the incident light produced in the PbWO 4 crystal. The results show that the Cherenkov light contribution to the total signal is more than 20% for both the Hamamatsu S8148 and ZnS–Si APD structures placed at end of the crystal.

Effects of temperature dependence of the signals from Lead Tungstate

In recent papers [1] it has been demonstrated that Lead Tungstate signals contain both scintillation and Cherenkov components. In order to further assess and evaluate the relative contribution of the Cherenkov component, we performed measurements at different temperatures, ranging from 13°C to 45°C being only the scintillation component affected by the temperature change. Over this temperature range, the total light yield was measured to decrease by a factor of 2, while the relative Cherenkov contribution to the signals increased by the same factor. We also studied the decay time of the scintillation process and observed it to decrease as well.

Separation of crystal signals into scintillation and Cherenkov components

The signals from high- Z scintillating crystals such as PbWO 4 and BGO contain a significant Cherenkov component. We investigate methods to determine the contribution of Cherenkov light to the signals generated by high-energy electrons and pions (mips), both statistically and event-by-event. These methods are based on differences in the spectra, the time structure and/or the directionality of the two types of light. The electron signals, and their composition, are also analyzed as a function of the age (or depth) of the shower.

TU‐C‐AUD‐01: Visual Sensations During Megavoltage Radiotherapy to the Orbit Attributable to Cherenkov Radiation

Purpose: To compute and to verify experimentally Cherenkov radiation production inside the eye from direct and indirect high energy x‐ray irradiation of the orbit and that it exceeds detectability of Cherenkov radiation in scotopic vision. We show that the Cherenkov yield for direct and indirect irradiation exceeds the detection threshold of 6.4×107 photons/m2s. Methods: In photon and electron beam radiotherapy of intraorbital and periorbital tissues, patients commonly report having light sensations during treatment. The explanation usually offered is that ‘nerve stimulation’ is occurring. The radiotherapy literature reports the effect to be the result of ‘phosphenes’. Although phosphenes may play a role, we propose instead that patients are predominantly seeing Cherenkov radiation resulting from electrons inside the eye having kinetic energy exceeding the Cherenkov radiation threshold of 0.26 MeV. We consider calculations for direct irradiation of the eye from a portal image and indirect irradiation from treatment of peri‐orbital tissues and show that it exceeds threshold detection. Results: We calculate the Cherenkov yield using analytic methods and the measurements were in good agreement with our calculations. The Cherenkov radiation from a distilled water phantom, a square plastic phantom and an anthropomorphic plastic phantom were readily visible with a high quality CCD video camera. A digital camera captures the images from the console monitor. Threshold detection of Cherenkov radiation emanating from the water phantom through the video camera was determined and compared to a measurable source. The calculations for the water phantom match reasonably well with measurements and are roughly 1 lux and 3 lux respectively. Conclusion: We show images of Cherenkov radiation emanating from routine radiotherapy treatments and demonstrate that measurements corresponding to these images match well with calculations. We show that the Cherenkov component generated inside ocular media is sufficient to be detected by the patient.

Cherenkov light in electron-induced air showers

In this paper, we present the results of a comparative analysis of the Cherenkov light produced by electromagnetic air showers initiated by primary gamma-rays and electrons. It is shown that the lateral distribution functions of the Cherenkov light initiated by these showers are different. This fact is explained by the difference in the development of cascades from gamma-rays and electrons; electron-showers start to develop and produce light earlier than gamma-showers, but they attenuate rapidly. By propagating much farther into the atmosphere, the gamma-initiated shower carries a Cherenkov component much closer to the ground level than electron initiated showers do; this results in a more intense pool of light close to the shower axis. The difference in the altitudes of electron- and gamma-air showers maximums logarithmically decreases with the energy and is more significant for low energy showers with E ⩽ 20 GeV. This can be important for low energy threshold Cherenkov telescopes (below 10 GeV), in which case the background events are due to diffuse cosmic ray electrons only. The minimum energy of primary electrons required for their reliable detection by an imaging atmospheric telescope will be higher than that for primary gamma-rays. For the reasonable value of the geomagnetic field strength of B ⩾ 0.3 G and at the initial energies of E ⩽ 20 GeV, the pulse width of the Cherenkov light generated by electron-showers is considerably larger than that from gamma-showers. At higher energies the shapes of Cherenkov pulse from showers induced by both primaries become almost similar.

Separation of scintillation and Cherenkov light in an optical calorimeter

Simultaneous measurement of the scintillation and the Cherenkov light produced in hadronic shower development makes it possible to eliminate the effects of fluctuations in the electromagnetic shower fraction, which dominate and spoil the performance of non-compensating calorimeters. In this paper, we report on a study to separate the light signal produced by an optical calorimeter into its scintillation and Cherenkov components. To this effect, we use differences in the time structure of these two signals, as well as differences in the angular distribution of these two types of light. Both methods give useful results, especially when the numbers of scintillation and Cherenkov photons are comparable.

The contribution to Cherenkov radiation from knock-on-electrons

When a high-energy charged particle passes through a Cherenkov detector, it will produce knock-on electrons that may also have velocities greater than the Cherenkov threshold. These high-energy electrons will contribute to the total Cherenkov signal and to fluctuations in the signal. We present calculations of the mean and standard error of the added Cherenkov component from an equilibrium or nonequilibrium distribution of knock-on electrons for sample detectors with refractive indices ranging from n = 1.03 to n = 1.49. We derive expression suitable for numerical integration for the mean and standard error under the assumption of Gaussian statistics, and briefly discuss the conditions under which this assumption is valid.