A Study on the Performance of a Silicon Photodiode Sensor for a Particle Dosimeter and Spectrometer

A lunar vehicle radiation dosimeter (LVRAD) has been proposed for studying the radiation environment on the lunar surface and evaluating its impact on human health. The LVRAD payload comprises four systems: a particle dosimeter and spectrometer (PDS), a tissue-equivalent dosimeter, a fast neutron spectrometer, and an epithermal neutron spectrometer. A silicon photodiode sensor with compact readout electronics was proposed for the PDS. The PDS system aims to measure protons with 10–100 MeV of energy and assess dose in the lunar space environment. The manufactured silicon photodiode sensor has an effective area of 20 mm × 20 mm and thickness of 650 μm; the electronics consist of an amplifier, analog pulse processor, and a 12-bit analog-to-digital converter for signal readout. We studied the responses of silicon sensors which were manufactured with self-made electronics to gamma rays with a wide range of energies and proton beams.

Design and verification of a multi-layer single-sphere neutron spectrometer with water as the moderator

Measuring the neutron energy spectrum is important in nuclear radiation detection and protection. Common neutron spectrometers include the Bonner sphere spectrometer (BSS), time-of-flight neutron spectrometer, and plastic scintillation detector. Among them, the BSS is the most widely used for its wide measurement range and simple operation. A BSS usually occupies a large space because it contains several independent spheres working at the same time, leading to poor consistency. This paper proposes a multi-layer single-sphere spectrometer using water as the moderator. The spectrometer includes a multi-layered sphere that can be filled with water or air and a ^3He proportional counter placed in the center of the sphere. To verify the feasibility of this design, we use Geant4 to calculate the moderating ability of water and the response functions of the multi-layer single-sphere spectrometer. Additionally, several standard neutron energy spectra (from IAEA) are used to test the response characteristics of this spectrometer through simulation. The simulation results prove the feasibility of the design. This research provides a theoretical basis for a multi-layer single-sphere neutron spectrometer with water as the moderator.

Intensive Study of Ceria Microsphere Stabilized with Zirconia by The External Gelatin Method

One of the keys to success in the process of fuel synthesis for pebble type high temperature nuclear reactors is mastery in kernel synthesis technology which is the core of the fuel itself. In this paper, the results of a comprehensive study of the preparation of a kernel microsphere from ceria stabilized zirconia (CSZ) using the external gelatin method in BATAN will be discussed. Important parameters obtained from this experiment will be the basis for the actual manufacturing of nuclear fuel kernels. Analysis based on measurement data using the Small Angle Neutron Spectrometer (SANS) provides a deep understanding of the mechanism of CSZ microsphere formation, so that at the end it can provide an understanding of how to avoid possible cracks during heat treatment.

An innovative neutron spectrometer for soil moisture measurements

Soil moisture is a crucial variable in evaluating soil properties and its interaction with the atmosphere, yet none of the techniques currently employed is fully adequate for evaluating the water content in soil over an area of hectares and depth of tens of centimeters. In recent times, it has been shown how the water content over this volume can be accurately assessed measuring changes in the epithermal flux of cosmic neutrons, which is extremely sensitive to the moderation caused by hydrogen. The instruments employed for neutron flux measurements are usually neutron counters, covered with moderator coatings for enhancing their sensitivity in the epithermal energy range. On the other hand, the worldwide shortage of $${}^{3}$$ 3 He caused a considerable increase in the costs associated with the manufacturing of proportional counters based on this gas, which were widely employed for their great sensitivity and noise rejection capability. In this work, we developed a $${}^{3}$$ 3 He-free neutron spectrometer for performing these measurements, which detects neutrons in the energy range from 0.01 ev to 1 GeV. The reconstruction of the energy spectrum allows a more accurate evaluation of the epithermal neutron flux and provides other information which improves the quality of soil moisture measurements. Irradiations performed with neutron sources of $${}^{241}$$ 241 Am and AmBe allowed to evaluate the spectrometric capability of the instrument, whereas the measurements of cosmic neutrons were employed to assess its sensitivity to cosmic radiation. The sensitivity of the instrument is slightly less than the one of the neutron counters currently employed, yet the access to the spectrometric information should provide greater accuracy in the epithermal flux measurements.

Calculation of response functions for cylindrical nested neutron spectrometer

In a recent work, a new neutron spectrometer, namely Cylindrical Nested Neutron Spectrometer (CNNS). It works under the same principles as a Bonner Sphere Spectrometer (BSS), except that different amounts of moderator around a thermal neutron detector are configured by adding or removing cylindrical shells. The CNNS consists of a 4mm x 4mm 6LiI(Eu) scintillator crystal and nested cylindrical polyethylenemoderators. The objective of this paper is describing the use of MCNPX code for determining a optimal ratio between height and diameter of the moderators in order to remain isotropic angular response to neutrons like BSS and determining of response functions for moderators of different diameters at 104 energy points from 0.001 eV to 19.95 MeV.

The ESA-JAXA BepiColombo mission: status and first results

<p>BepiColombo was launched on 20 October 2018 from the European spaceport Kourou in French Guyana and is now on route to Mercury to unveil Mercury’s secrets. BepiColombo a joint project between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA) consists of two orbiters, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (Mio). It will perform measurements to increase our knowledge on the fundamental questions about Mercury’s evolution, composition, interior, magnetosphere, and exosphere.  </p><p>During its 7-year long journey to the innermost terrestrial planet Mio and MPO are connected to each on-top of the Mercury Transfer Module (MTM). The MTM contains a solar electric propulsion engine and will bring the two spacecraft to Mercury. In late 2025, this ‘stack’ configuration is abandoned, the MTM will be jettisoned and the individual elements spacecraft are brought in to their final Mercury orbit: 480x1500km for MPO, and 590x11640km for Mio.  </p><p>On its way BepiColombo with its state of the art and very comprehensive payload has several opportunities for scientific observations - during the cruise into the inner solar system and during its nine planetary flybys (one at Earth, two at Venus and six at Mercury). However, since the spacecraft is in a stacked configuration not all of the instruments can be operated during the cruise phase.</p><p>Some of the instruments have been already operated regularly or partially during the flybys in their “scientific” observation mode: e.g. the magnetometer (MPO-MAG), the accelerometer (ISA), the environmental sensor (BERM), the gamma-ray and neutron spectrometer (MGNS), the solar intensity x-ray and particle spectrometer (SIXS), the radio science experiment (MORE), using the X-band and the Ka-band, the thermal infrared spectrometer (MERTIS), the UV spectrometer (PHEBUS) and some sensors of the SERENA suite. Also, instruments or some parts of the instruments of the Japanese Mio spacecraft like the dust monitor (MDM), the plasma wave instrument (PWI), the particle and plasma experiments of MPPE and the magnetometer (MGF) were already successfully operated in their science modes. BepiColombo also took regular “selfie” images with their three monitoring cameras on the MTM. These cameras were also able to take a sequence of outreach images during the flybys at Earth and Venus in 2020. Other instruments such as cameras and NIR spectrometer (SIMBIO-SYS), the laser altimeter (BELA), the x-ray spectrometer (MIXS), and parts of the electron, neutron, and iron sensors of SERENA on MPO and MSASI and some dedicated sensors of PWI and MPPE are operational, but can only be used in their scientific modes after the Mercury in-orbit commissioning in early 2026 because their field of view is blocked by the underlying Transfer Module.</p><p>Despite the reduced instrument availability, scientific and engineering operations has been scheduled during the cruise phase, especially during the swing-bys. A status of the mission and instruments and a summary of first results from measurements taken during the first three years en route to Mercury will be given.</p>