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Silicon photomultipliers (SiPMs) from various manufacturers are shown to be sensitive to gamma-ray ionizing radiation without being coupled to a scintillator. Survey measurements of units from Hamamatsu, SENSL, and KETEK are shown, followed by detailed measurements of units from SENSL. Pulseheight spectroscopy of gamma-ray-induced signals reveals large pulses in excess of 16 microcells excited per event and as large as ~100 excited microcells. We review other examples of direct excitation by ionizing radiation found in the literature and surmise the effect that is related to the scattered charged particles (electrons) passing through the SiPM. We demonstrate that this direct sensitivity extends to cosmic-ray secondaries by a triple-coincidence experiment. The precise signal producing mechanism is unclear. The signal may be due to light producing processes, such as Čerenkov or scintillation in the optical windows, or charged particle ionization in the microcell layer, which may induce avalanches in microcells along the particle track. Possible applications and avenues for future study are suggested. [ABSTRACT FROM AUTHOR]

We present the results of experiments applying a large area tiled array of silicon photomultipliers (SiPM) to gamma ray spectroscopy with 50.8 mm diameter NaI(Tl) and CsI(Tl) scintillators and 25.4 mm diameter CeBr3. These scintillators are many times larger than an individual SiPM, the largest of which are 36 mm2 at present. This work compares two methods of summing 64 SiPMs into a single output signal for use with standard charge integration electronics. The methods are a straightforward passive method, which simply combines all anode and cathodes together, and an active method, which employs high bandwidth op-amps in a summing topology. Comparisons are also made to a high quantum efficiency photomultiplier tube (PMT) for both resolution and pulse shape. Resolution and noise floor are satisfactorily comparable to the PMT from 21 keV to 2614 keV. The passive method provides the most straightforward approach, and slightly better energy resolution than the active method. The active method shows a substantially faster pulse rise time and undistorted fall time compared to the passive method. [ABSTRACT FROM AUTHOR]

We review a simple gamma ray spectrometer constructed on a solderless breadboard. The spectrometer's detector consists of a CsI(Tl) scintillator and silicon photomultiplier (SiPM) and its readout is facilitated by an Arduino UNO. The system is low cost and utilizes a minimum of components while still achieving satisfactory charge linearity and noise levels. This instrument can be used in instructional laboratories to introduce both radiation detection and analog signal processing concepts. We also expect it will be of interest to those seeking to introduce gamma spectroscopy to the expanding ecosystem of Arduino hardware. [ABSTRACT FROM AUTHOR]

We present results demonstrating neutron detection via a closely spaced converter structure coupled to low pressure noble gas scintillation instrumented by a single photo-multiplier tube (PMT). The converter is dispersed throughout the gas volume using a reticulated vitreous carbon foam coated with boron carbide (B4C). A calibrated cold neutron beam is used to measure the neutron detection properties, using a thin film of enriched 10B as a reference standard. Monte Carlo computations of the ion energy deposition are discussed, including treatment of the foam random network. Results from this study indicate that the foam shadows a significant portion of the scintillation light from the PMT. The high scintillation yield of Xe appears to overcome the light loss, facilitating neutron detection and presenting interesting opportunities for neutron detector design. [ABSTRACT FROM AUTHOR]

There is interest in developing the ability to rapidly compute the energy dependent neutron flux within a complex geometry for a variety of applications. Coupled with sensor response function information, this capability would allow direct estimation of sensor behavior in multitude of operational scenarios. In situations where detailed simulation is not warranted or affordable, it is desirable to possess reliable estimates of the neutron field in practical scenarios which do not require intense computation. A tool set of this kind would provide quantitative means to address the development of operational concepts, inform asset allocation decisions, and exercise planning. [ABSTRACT FROM PUBLISHER]

It is generally accepted that the main cause of ultracold neutron (UCN) losses in storage traps is upscattering to the thermal energy range by hydrogen adsorbed on the surface of the trap walls. However, the data on which this conclusion is based are poor and contradictory. Here we report a measurement, performed at the Los Alamos National Laboratory UCN source, of the average energy of the flux of upscattered neutrons after the interaction of UCN with hydrogen bound in the semicrystalline polymer PMP (trade name TPX), [C6H4]n, Our analysis, performed with the MCNP code which applies the neutron-scattering law to UCN upscattered by bound hydrogen in semicrystalline polyethylene, [C2H4]n, leads us to a flux average energy value of 26 ± 3 meV, in contradiction to previously reported experimental values of 10 to 13 meV and in agreement with the theoretical models of neutron heating implemented in MCNP. [ABSTRACT FROM AUTHOR]

We describe the observation of the isospin violating and charge symmetry breaking reaction dd→απ0 just above threshold. Measurements using a magnetic channel (gated by two photons) of the 4He scattering angle and momentum (from time of flight) permitted reconstruction of the π0 "missing mass," the quantity used to separate distributions of 4He+π0 events from a continuum containing 4He+γ+γ and 4He+π0+γ events. A review has been completed of the apparatus, relevant geant simulations, various corrections, and the d+p scattering cross section used as a luminosity calibration. The new values of the total cross section for neutral pion production are 14.3±2.2(stat)±1.6(sys) pb at 228.5 MeV and 17.3±3.4(stat)±2.4(sys) pb at 231.8 MeV. The uncertainty remains dominated by statistical errors. These cross sections arise from the down-up quark mass difference and quark electromagnetic effects. [ABSTRACT FROM AUTHOR]