Measurements of the energy spectra of charged particles within the vertical-10 rocket experiment

On December 21-st, 1981, at 18.35 hours UT from the territory of the USSR (coordinates - 49°N/L 2/) in implementation of scientific objectives and in accordance with the ‘INTERCOSMOS’ Programme, there was launched the heavy geophysical rocket ‘VERTICAL-10’. The scientific payload included a low-energy two-channel spectrometer for measuring the differential flows of electrons and protons within the energy range 0.1 to 10 keV, covered by 15 exponentially distributed energy levels.     

Head and neck tumors after energetic proton irradiation in rats.

This is a two-year progress report on a life span dose-response study of brain tumor risk at moderate to high doses of energetic protons. It was initiated because a joint NASA/USAF life span study of rhesus monkeys that were irradiated with 55-MeV protons (average surface dose, 3.5 Gy) indicated that the incidence of brain tumors per unit surface absorbed dose was over 19 times that of the human tinea capitis patients whose heads were exposed to 100 kv x-rays. Examination of those rats that died in the two-year interval after irradiation of the head revealed a linear dose-response for total head and neck tumor incidence in the dose range of 0-8.5 Gy. The exposed rats had a greater incidence of pituitary chromophobe adenomas, epithelial and mesothelial cell tumors than the unexposed controls but the excessive occurrence of malignant gliomas that was observed in the monkeys was absent in the rats. The estimated dose required to double the number of all types of head and neck tumors was 5.2 Gy. The highest dose, 18 Gy, resulted in high mortality due to obstructive squamous metaplasia at less than 50 weeks, prompting a new study of the relative biological effectiveness of high energy protons in producing this lesion.     

HXMT卫星空间环境监测器及初步观测结果

硬X射线调制望远镜（HXMT）卫星是中国首个专门进行天文探测的空间科学实验卫星,运行于高度约550km、倾角约43°的低地球轨道.星载空间环境监测器为星上科学任务开展提供背景辐射实测资料.该监测器采用固体探测器望远镜系统和扇形阵列全新组合设计,可获取轨道空间高能质子和高能电子能谱、方向综合动态结果,给出更为全面的粒子辐射分布图像.初步探测结果显示,卫星运行轨道遭遇的带电粒子辐射集中分布在经度80°W-20°E,纬度0°-40°S的南大西洋异常区,粒子辐射在该区域表现出不同程度的方向差异分布,高能电子方向差异分布显著强于高能质子.2017年9月空间环境扰动期间,爆发的太阳质子事件并未对该轨道粒子辐射产生影响,而地磁活动导致该轨道穿越经度120°W-60°E,纬度40°-43°N的北美上空和经度60°-120°E,纬度43°-40°S的澳大利亚西南区域时遭遇增强粒子辐射影响,增强的粒子辐射表现出极强的方向分布.      

Depth dose measurements with the Liulin-5 experiment inside the spherical phantom of the MATROSHKA-R project onboard the International Space Station

The Liulin-5 experiment is a part of the international project MATROSHKA-R on the Russian segment of the ISS, which uses a tissue-equivalent spherical phantom equipped with a set of radiation detectors. The objective of the MATROSHKA-R project is to provide depth dose distribution of the radiation field inside the sphere in order to get more information on the distribution of dose in a human body. Liulin-5 is a charged particle telescope using three silicon detectors. It measures time resolved energy deposition spectra, linear energy transfer (LET) spectra, particle flux, and absorbed doses of electrons, protons and heavy ions, simultaneously at three depths along the radius of the phantom. Measurements during the minimum of the solar activity in cycle 23 show that the average absorbed daily doses at 40 mm depth in the phantom are between 180 μGy/day and 220 μGy/day. The absorbed doses at 165 mm depth in the phantom decrease by a factor of 1.6–1.8 compared to the doses at 40 mm depth due to the self-shielding of the phantom from trapped protons. The average dose equivalent at 40 mm depth is 590 ± 32 μSV/day and the galactic cosmic rays (GCR) contribute at least 70% of the total dose equivalent at that depth. Shown is that due to the South Atlantic Anomaly (SAA) trapped protons asymmetry and the direction of Liulin-5 lowest shielding zone the dose rates on ascending and descending nodes in SAA are different. The data obtained are compared to data from other radiation detectors on ISS.     

Occurrence of brain tumors in rhesus monkeys exposed to 55-MeV protons.

Twenty-year observation of monkeys exposed to single doses of high energy protons simulating solar particles revealed that the most prevalent fatal cancers were brain tumors in the group of animals exposed to 55-MeV protons. Of 72 animals (50 males and 22 females) receiving 0.25 to 8.0 Gy total body surface dose, nine developed fatal tumors classified as grade IV astrocytoma or glioblastoma multiforme. The latent period for tumor development ranged from 14 months to 20 years, with a median of 5 years. Doses associated with the tumors were 4.0 to 8.0 Gy. Eight males and one female were affected. Depth-dose determinations suggest that the high incidence of cerebral neoplasia is associated with the Bragg Peak energy distribution of the 55-MeV protons. Comparison of the tumor incidence with that in humans with brain exposures incidental to radiotherapy indicates a high biological effectiveness compared with gamma radiation. Studies are in progress to attempt to replicate the results in rodents and establish a dose-response curve for proton-induced brain tumors.     

Analysis of cytogenetic effects of the secondary radiation resulting from 70 GeV protons of Chinese hamster cells.

The cell culture of a Chinese hamster was irradiated on a Serpuchov proton synchrotron at a dose of 0.5-4 Gy and a dose rate of 1 Gy/min and by gamma-irradiation at dose 1-5 Gy and dose rate 1.2-1.4 Gy/min. The effect of radiation on the cell culture was judged from chromosomal aberrations in G2-stage of cell cycle and micronuclear test. The relative biological efficience of the secondary radiation was approximately 3. Modifying effect of caffeine on the cells irradiated by secondary radiation of synchrotron was not observed. In the presence of caffeine the effect of gamma-irradiation practically is increased up to the level observed upon secondary irradiation. This suggests that secondary radiation inhibits the repair of the cytogenetic damage.     

Characterization of the near Earth radiation environment by Liulin type spectrometers

Comprehensive study of the dose, flux and deposited energy spectra shape data obtained by Liulin type spectrometers on spacecraft (five different experiments) and aircraft since 2001 is performed with the aim of understanding how well these parameters can characterize the type of predominant particles and their energy in the near Earth radiation environment. Three different methods for characterisation of the incoming radiation from Liulin spectrometers are described. The results revealed that the most informative one is by the shape of the deposited energy spectra. Spectra generated by Galactic Cosmic Rays (GCR) protons and their secondaries are with linear falling shape in the coordinates deposited energy/deposited per channel dose rate. The position of the maximum of the deposited energy spectra inside the South Atlantic Anomaly (SAA) region depends on the incident energy of the incoming protons. Spectra generated by relativistic electrons in the outer radiation belt have a maximum in the first channels. For higher energy depositions these spectra are similar to the GCR spectra. Mixed radiation by protons and electrons and/or bremsstrahlung is characterized by spectra with 2 maxima. All type of spectra has a knee close to 6.2 MeV deposited energy, which correspond to the stopping energy of protons in the detector. Dose to flux ratio known also as specific dose is another high information parameter, which is given by experimentally obtained formulae [Heffner, J. Nuclear radiation and safety in space. M. Atomizdat. 115, 1971 (in Russian)] connecting the dose to flux ratio and the incident energy of the particles.     

In vivo and in vitro measurements of complex-type chromosomal exchanges induced by heavy ions.

Heavy ions are more efficient in producing complex-type chromosome exchanges than sparsely ionizing radiation, and this can potentially be used as a biomarker of radiation quality. We measured the induction of complex-type chromosomal aberrations in human peripheral blood lymphocytes exposed in vitro to accelerated H-, He-, C-, Ar-, Fe- and Au-ions in the LET range of approximately 0.4-1400 keV/micrometers. Chromosomes were analyzed either at the first post-irradiation mitosis, or in interphase, following premature condensation by phosphatase inhibitors. Selected chromosomes were then visualized after FISH-painting. The dose-response curve for the induction of complex-type exchanges by heavy ions was linear in the dose-range 0.2-1.5 Gy, while gamma-rays did not produce a significant increase in the yield of complex rearrangements in this dose range. The yield of complex aberrations after 1 Gy of heavy ions increased up to an LET around 100 keV/micrometers, and then declined at higher LET values. When mitotic cells were analyzed, the frequency of complex rearrangements after 1 Gy was about 10 times higher for Ar- or Fe- ions (the most effective ions, with LET around 100 keV/micrometers) than for 250 MeV protons, and values were about 35 times higher in prematurely condensed chromosomes. These results suggest that complex rearrangements may be detected in astronauts' blood lymphocytes after long-term space flight, because crews are exposed to HZE particles from galactic cosmic radiation. However, in a cytogenetic study of ten astronauts after long-term missions on the Mir or International Space Station, we found a very low frequency of complex rearrangements, and a significant post-flight increase was detected in only one out of the ten crewmembers. It appears that the use of complex-type exchanges as biomarker of radiation quality in vivo after low-dose chronic exposure in mixed radiation fields is hampered by statistical uncertainties.     

The effects of proton exposure on neurochemistry and behavior.

Future space missions will involve long-term travel beyond the magnetic field of the Earth, where astronauts will be exposed to radiation hazards such as those that arise from galactic cosmic rays. Galactic cosmic rays are composed of protons, alpha particles, and particles of high energy and charge (HZE particles). Research by our group has shown that exposure to HZE particles, primarily 600 MeV/n and 1 GeV/n 56Fe, can produce significant alterations in brain neurochemistry and behavior. However, given that protons can make up a significant portion of the radiation spectrum, it is important to study their effects on neural functioning and on related performance. Therefore, these studies examined the effects of exposure to proton irradiation on neurochemical and behavioral endpoints, including dopaminergic functioning, amphetamine-induced conditioned taste aversion learning, and spatial learning and memory as measured by the Morris water maze. Male Sprague-Dawley rats received a dose of 0, 1.5, 3.0 or 4.0 Gy of 250 MeV protons at Loma Linda University and were tested in the different behavioral tests at various times following exposure. Results showed that there was no effect of proton irradiation at any dose on any of the endpoints measured. Therefore, there is a contrast between the insignificant effects of high dose proton exposure and the dramatic effectiveness of low dose (<0.1 Gy) exposures to 56Fe particles on both neurochemical and behavioral endpoints.     

Long lasting energetic particle injection from a weak flare

A relatively weak solar cosmic ray event registered at the Earth orbit following the flare of December 17, 1976 is discussed. The main feature of the event is the existence of a prolonged unusually high proton and electron anisotropy; even at the end of the decay phase of the flare the motion of the particles were mainly directed away from the Sun. The durations of proton and electron anisotropies were different. If prolonged particle injection is neglected the value of the anisotropy considerable exceeds all diffusive estimates. Time-intensity and anisotropy profiles of electrons and protons are fitted by a diffusive model including prolonged particle injection at the Sun. The best agreement with the data is obtained if the duration of injection equals about 20 and 7 hours for protons and electrons, respectively.     

Radioprotection by metals: selenium.

The need exists for compounds that will protect individuals from high-dose acute radiation exposure in space and the agents that might be less protective but less toxic and longer acting. Metals and metal derivatives provide a small degree of radioprotection (dose reduction factor < or = 1.2 for animal survival after whole-body irradiation). Emphasis is placed here on the radioprotective potential of selenium (Se). Both the inorganic salt, sodium selenite, and the organic Se compound, selenomethionine, enhance the survival of irradiated mice (60Co, 0.2 Gy/min) when injected IP either before (-24 hr and -1 hr) or shortly after (+15 min) radiation exposure. When administered at equitoxic doses (one-fourth LD10; selenomethionine = 4.0 mg/kg Se, sodium selenite = 0.8 mg/kg Se), both drugs enhanced the 30-day survival of mice irradiated at 9 Gy. Survival after 10-Gy exposure was significantly increased only after selenomethionine treatment. An advantage of selenomethionine is lower lethal and behavioral toxicity (locomotor activity depression) compared to sodium selenite, when they are administered at equivalent doses of Se. Sodium selenite administered in combination with WR-2721, S-2-(3-aminopropylamino)ethylphosphorothioic acid, enhances the radioprotective effect and reduces the lethal toxicity, but not the behavioral toxicity, of WR-2721. Other studies on radioprotection and protection against chemical carcinogens by different forms of Se are reviewed. As additional animal data and results from human chemoprevention trials become available, consideration also can be given to prolonged administration of Se compounds for protection against long-term radiation effects in space.     

Overview on experience to date on human exposure to space radiations.

The human exposure in space depends on the three factors: the flight trajectory, its date and duration and the cyclogram of the cosmonaut's activities. In the near-Earth orbits the daily dose varies within the limits of (1.5-5.0) 10(-4) Gy day-1 and greatly increases if the altitude increases. The mean daily quality factor is 1.6-2.0. Strong solar proton events in the orbits with the inclination of < 52 degrees result in the dose rate increase up to 2-3 cGy day-1. On the surface of the orbital spacecrafts the daily dose reaches 2 Gy. The neutron dose depends on the shielding mass distribution varying within the limits of 6%-30% of the charged particles dose. In deep space the dose is mainly formed by the galactic and solar cosmic rays(GCR,SCR). Behind the shielding of 2-3 g cm-2 Al the GCR dose varies in the range of (20-30) 10(-5) Gy day-1. The SCR dose can reach hundreds of cSv.     

Low fluence.

The question of the appropriate extrapolation to low dose has long been a subject of controversy. A linear no-threshold model is favored by regulatory bodies as the basis of RBE assignments and estimates of radiation hazards to the general population. This model is largely supported by extensive application of the linear-quadratic survival formula "fitted" statistically to a wide variety of experimental data obtained at doses typically exceeding 1 Gy, and then extrapolated to mGy for practical applications, and even to the prediction of hazards from single electrons. Such extrapolations are questionable at best, and may even prove hazardous for risk evaluations. Fluence and geometry rather than dose based data are proposed as a basis for a limiting "threshold" for a "low dose" extrapolation. The proposed threshold is one where the fluence of particles is one per square micron, where on average only 2/3 of the 1 micrometers2 pixels covering an irradiated area are traversed by one or more particles. The corresponding dose threshold is determined by the LET of the bombarding radiation. For relativistic electrons this dose is about 0.032 Gy.     

Relativistic electron fluxes and dose rate variations during April–May 2010 geomagnetic disturbances in the R3DR data on ISS

Space radiation has been monitored successfully using the Radiation Risks Radiometer-Dosimeter (R3D) installed at the ESA EXPOSE-R (R3DR) facility outside of the Russian Zvezda module of the International Space Station (ISS) between March 2009 and January 2011. R3DR is a Liulin type spectrometer–dosimeter with a single Si PIN detector 2 cm² of area and 0.3 mm thick. The R3DR instrument accumulated about 2 million measurements of the absorbed dose rate and flux of 10 s resolution. The total external and internal shielding before the detector of R3DR device is 0.41 g cm⁻². The calculated stopping energy of normally incident particles to the detector is 0.78 MeV for electrons and 15.8 MeV for protons. After the Coronal Mass Ejection (CME) at 09:54 UTC on 3 April 2010, a shock was observed at the ACE spacecraft at 0756 UTC on 5 April, which led to a sudden impulse on Earth at 08:26 UTC. Nevertheless, while the magnetic substorms on 5 and 6 of April were moderate; the second largest in history of GOES fluence of electrons with energy >2 MeV was measured. The R3DR data show a relatively small amount of relativistic electrons on 5 April. The maximum dose rate of 2323 μGy day⁻¹ was reached on 7 April; by 9 April, a dose of 6600 μGy was accumulated. By the end of the period on 7 May 2010 a total dose of 11,587 μGy was absorbed. Our data were compared with AE-8 MIN, CRESS and ESA-SEE1 models using SPENVIS and with similar observations on American, Japanese and Russian satellites.     

FEM code simulation of the magnetospheric proton fluxes

We report a study of the numeric solution to the diffusive transport equation for energetic protons magnetically trapped in the Earth's equatorial magnetosphere. The analysis takes into account the pertinent physical processes in this region, including deceleration of protons by Coulomb collisional interactions with free and bound electrons, the charge exchange process, cosmic ray albedo neutron decay source, and electric and magnetic radial diffusion. These results were obtained using the Finite Element Method with magnetic moment and geomagnetic L-shell as free variables. Steady state boundary conditions were imposed at L=1 as zero distribution function and at L=7 with proton distribution function extracted from ATS 6 satellite observations. The FEM-code yields unidirectional proton flux in the energy range of 0.1–1000 MeV at the equatorial top of the geomagnetic lines, and the results are found to be in satisfactorily agreement with the empirical NASA AP-8 model proton flux within the energy range of 0.5–100 MeV. Below 500 keV, the empirical AP-8 model proton fluxes are several orders of magnitude greater than those computed with the FEM-code at L<3. This discrepancy is difficult to explain by uncertainties of boundary spectrum parameters or transport coefficients.     

Cataractogenesis from high-LET radiation and the Casarett model.

Space radiations, especially heavy ions, constitute significant hazards to astronauts. These hazards will increase as space missions lengthen. Moreover, the dangers to astronauts will be enhanced by the persistence, or even the progression, of biological damage throughout their subsequent life spans. To assist in the assessment of risks to astronauts, we are investigating the long-term effects of heavy ions on specific animal tissues. In one study, the eyes of rabbits of various ages were exposed to a single dose of Bragg plateau 20Ne ions (LET infinity approximately equals 30 keV/micrometer). The development of cataracts has shown a pronounced age-related response during the first year after irradiation, and will be followed for two more years. In other studies, mice were exposed to single or fractionated doses of 12C ions (4-cm spread-out Bragg peak; dose-averaged LET infinity = 70-80 keV/micrometer) or 60Co gamma-photons (LET infinity = 0.3 keV/micrometer). Measurements of the frequency of posterior lens opacification have shown that the tissue sparing observed with dose fractionation of gamma-photons was absent when 12C-ion doses were fractionated. Development of posterior lens cataracts was also followed for long periods (up to 21 months) in mice exposed to single doses of Bragg plateau HZE particles (40Ar, 20Ne and 12C ions: LET infinity approximately equals 100, 30 and 10 keV/micrometer, respectively) or 225 kVp X-rays. Based on average cataract levels at the different observation times, the RBE's (RBE = relative biological effectiveness) for the ions were circa 5, 3 and 1-2, respectively, over the range of doses used (0.05-0.9 Gy). Investigations of cataractogenesis are useful for exploring the model of radiation damage proposed by Casarett and by Rubin and Casarett with a tissue not connected directly to the vasculature.     

Late effects from particulate radiations in primate and rabbit tissues.

Optic tissues in groups of New Zealand white rabbits were irradiated locally at different stages throughout the median life span of the species with a single dose (9 Gy) of 425 MeV/amu Ne ions (LET infinity approximately 30 keV/micrometer) and then inspected routinely for the progression of radiation cataracts. The level of early cataracts was found to be highest in the youngest group of animals irradiated (8 weeks old), but both the onset of late cataracts and loss of vision occurred earlier when animals were irradiated during the second half of the median life span. This age response can have serious implications in terms of space radiation hazards to man. Rhesus monkeys that had been subjected to whole-body skin irradiation (2.8 and 5.6 Gy) by 32 MeV protons (range in tissue approximately 1 cm) some twenty years previously were analysed for radiation damage by the propagation of skin fibroblasts in primary cultures. Such propagation from skin biopsies in MEM-alpha medium (serial cultivation) or in supplemented Ham's F-10 medium (cultivation without dilution) revealed late damage in the stem (precursor) cells of the skins of the animals. The proton fluxes employed in this experiment are representative of those occurring in major solar flares.     

High energy charged particle experiment – A payload proposal to KuaFu-B mission

High Energy Charged Particle Experiment (HECPE) is to measure the fluxes of MeV electrons and tens of MeV protons. The two satellites of KuaFu-B are in the same polar orbit with apogee 7.0R_E, perigee 1.8R_E. They can sweep large L values and pass through the inner and outer radiation belts. The high energy electrons and protons in the radiation belts are principal sources for failures of satellites and spacecrafts in the Earth orbits. The enhancements of the high energy electrons and protons, so-called energetic particle events, are important phenomena of the Space Weather. The energy ranges monitored by HECPE are 0.3–0.5 MeV, 0.5–1.0 MeV, 1.0–2.0 MeV, and E > 2.0 MeV for electrons, 5–10 MeV, 10–20 MeV, 20–40 MeV, and 40–80 MeV for protons.     

Photoionization balance and ion composition model in the equatorial D-region over Thumba

Positive and negative ion profiles, together with the λ-profile (ratio of negative ions to electrons), have been derived for Thumba (8°54′N) for noon conditions and for the height range 50–90 km, using the latest available input parameters.