For utilizing silicon photomultipliers (SiPMs) in space experiments, we conducted irradiation experiments of SiPMs with protons and iron ions. In particular, the relationship between the leakage ...current and the radiation dose was investigated under various irradiation conditions to determine techniques of mitigating damage caused by radiation. The leakage current was approximately proportional to the dose; however, the proportionality constant did not significantly vary with the irradiation conditions. The effects of annealing after irradiation tests indicated no substantial decrease in the leakage current. Conversely, while the leakage current increased with the dose, the SiPMs continued to operate even after 5 krad of irradiation, which corresponds to several years of radiation exposure in space at altitudes of ~400 km to 500 km. The results obtained from these irradiation tests are used to characterize a hard X-ray (> 60 keV) detector for space-based applications. This detector couples an inorganic scintillator with a high light yield, such as CsI(Tl), to a SiPM.
We have developed a sensor head for a time-of-flight (TOF) PET scanner using plastic scintillators that have a very fast timing property. Given the very small cross section of photoelectric ...absorption in plastic scintillators at 511 keV, we use Compton scattering in order to compensate for detection efficiency. The detector will consist of two layers of scatterers and absorbers which are made of plastic and inorganic scintillators such as GAGG:Ce, respectively. Signals are read by monolithic Multi Pixel Photon Counters, and with energy deposits and interaction time stamps are being acquired. The scintillators are built to be capable of resolving interaction position in three dimensions, so that our system has also a function of depth-of-interaction (DOI) PET scanners. TOF resolution of ∼200 ps (FWHM) is achieved in both cases of using the leading-edge discriminator and time-walk correction and using a configuration sensitive to DOI. Both the position resolution and spectroscopy are demonstrated using the prototype data acquisition system, with Compton scattering events subsequently being obtained. We also demonstrated that the background rejection technique using the Compton cone constraint could be valid with our system.
Detection of low-intensity light relies on the conversion of photons to photoelectrons, which are then multiplied and detected as an electrical signal. To measure the actual intensity of the light, ...one must know the factor by which the photoelectrons have been multiplied. To obtain this amplification factor, we have developed a procedure for estimating precisely the signal caused by a single photoelectron. The method utilizes the fact that the photoelectrons conform to a Poisson distribution. The average signal produced by a single photoelectron can then be estimated from the number of noise events, without requiring analysis of the distribution of the signal produced by a single photoelectron. The signal produced by one or more photoelectrons can be estimated experimentally without any assumptions. This technique, and an example of the analysis of a signal from a photomultiplier tube, are described in this study.
Target materials were exposed to a muon beam with an energy of 160GeV/c at the COMPASS experiment line in CERN-SPS to measure the production cross-sections for muon-induced radionuclides. A muon ...imager containing four nickel plates, each measuring 100mm×100mm, exposed to the IP plate successfully detected the muon beam image during an irradiation period of 33 days. The contrasting density rate of the nickel plate was (5.2±0.7)×10–9 PSL/muon per one-day exposure to IP. The image measured 122mm and 174mm in horizontal and vertical lengths, respectively, in relation to the surface of the base, indicating that 50±6% of the muon beam flux is confined to an area of 18% of the whole muon beam. The number of muons estimated from the PSL value in the total beam image area (0.81±0.1)×1013 was comparable to the total muon counts of the ion-chamber at the M2 beam line in the CERN-SPS. The production cross-sections of Cr-51, Mn-54, Co-56, Co-57, and Co-58 in nickel were 0.19±0.08, 0.34±0.06, 0.5±0.05, 3.44±0.07, 0.4±0.03 in the unit of mb, respectively, reducing muon associated particles effects. They are approximately 10 times smaller than that a proceeding study by Heisinger et al.
Protons with energies up to ∼1015 eV are the main component of cosmic rays, but evidence for the specific locations where they could have been accelerated to these energies has been lacking. ...Electrons are known to be accelerated to cosmic-ray energies in supernova remnants, and the shock waves associated with such remnants, when they hit the surrounding interstellar medium, could also provide the energy to accelerate protons. The signature of such a process would be the decay of pions (π0), which are generated when the protons collide with atoms and molecules in an interstellar cloud: pion decay results in γ-rays with a particular spectral-energy distribution. Here we report the observation of cascade showers of optical photons resulting from γ-rays at energies of ∼1012 eV hitting Earth's upper atmosphere, in the direction of the supernova remnant RX J1713.7-3946. The spectrum is a good match to that predicted by pion decay, and cannot be explained by other mechanisms.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Imaging characteristics of glass capillary plate gas detector Tokanai, F.; Sugiyama, H.; Sumiyoshi, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2010, Letnik:
623, Številka:
1
Journal Article
Recenzirano
A glass capillary plate (CP) gas detector with gas mixtures of He, Ne, Ar, and Xe has been successfully operated as a visible and near-infrared (NIR) scintillation proportional counter. Gas gains of ...up to 104 can be achieved using these gas mixtures. The scintillation light emitted during the generation of electron avalanches can be observed using a photomultiplier tube (PMT) and a compact optical imaging system that consists of a CP gas detector and a cooled CCD camera coupled to lens optics. Using this optical imaging system, clearer X-ray images have been obtained with the above gas mixtures. The dependence of the imaging quality on the pressure in the range 0.25–1atm was also investigated for the Ar (90%)+CF4 (10%) gas mixture. The successful operations using these gas mixtures have allowed us to realize a novel imaging device with a CP gas detector for gaseous PMTs sensitive to visible light.
PDF
