A study of low energy cosmic rays at 1 AU
IMP telescope data analysis for proton and alpha particle fluxes
Kinsey, J. H.↗
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A 200-MeV pi(+) induced nucleon removal from 24Mg
Nuclear gamma rays in coincidence with outgoing pions and/or protons following single nucleon removal from Mg24 by 200 MeV pi(+) were detected with Ge(Li) detectors. Differential cross sections are reported for gamma rays from the first excited mirror states of Na23 to Mg23 in coincidence with positive pions and/or protons detected in particle telescopes at 30, 60, 90, 120 and 150 deg; angle integrated absolute cross sections and cross section ratios sigma (Mg23/sigma (Na23) are calculated. These results are compared with the predictions of the one step quasifree (OSQF), the intranuclear cascade (INC), and the nucleon charge exchange (NCX) reaction models. The OSQF and the INC calculations generally agree with the experimental results, while the NCX calculations are in disagreement.
Joyce, D.↗
The cosmic ray interplanetary radial gradient from 1972 - 1985
It is now established that the solar modulation of cosmic rays is produced by turbulent magnetic fields propagated outward by the solar wind. Changes in cosmic ray intensity are not simultaneous throughout the modulation region, thus requiring time dependent theories for the cosmic ray modulation. Fundamental to an overall understanding of this observed time dependent cosmic ray modulation is the behavior of the radial intensity gradient with time and heliocentric distance over the course of a solar modulation cycle. The period from 1977 to 1985 when data are available from the cosmic ray telescopes on Pioneer (P) 10, Voyager (V) 1 and 2, and IMP 8 spacecraft is studied. Additional data from P10 and other IMP satellites for 1972 to 1977 can be used to determine the gradient at the minimum in the solar modulation cycle and as a function of heliocentric distance. All of these telescopes have thresholds for protons and helium nuclei of E 60 MeV/nucleon.
Webber, W. R.↗
The 200 MeV Pi+ induced single-nucleon removal from 24Mg
Nuclear gamma-rays in coincidence with outgoing pions or protons following single nucleon removal from Mg-24 by 200 MeV pions (+) were detected with Ge(Li) detectors. Differential cross sections are reported for gamma-rays from the first excited mirror states of Na-23 and Mg-23 in coincidence with positive pions or protons detected in particle telescopes at 30, 60, 90, 120, and 150 deg; angle-integrated absolute cross sections and cross section ratios are calculated. These results are compared with the predictions of a Pauli-blocked plane-wave impulse approximation (PWIA) and the intranuclear cascade (INC) and nucleon charge exchange (NCX) reaction models. The PWIA and the INC calculations generally agree with the angular dependence of the experimental results but not the absolute magnitude. The NCX calculation does not reproduce the observed cross section charge ratios.
Joyce, Donald↗
Managing radiation degradation of CCDs on the Chandra X-ray Observatory II
The CCDs on the Chandra X-ray Observatory are vulnerable to radiation damage from low-energy protons scattered off the telescope's mirrors onto the focal plane. Following unexpected damage incurred early in the mission, the Chandra Team developed, implemented, and maintains a radiation-protection program. This program - involving scheduled radiation safing during radiation-belt passes, intervention based upon real-time space-weather conditions and radiation-environment modeling, and on-board radiation monitoring with autonomous radiation safing - has successfully managed the radiation damage to the CCDs. Since implementing the program, the charge-transfer inefficiency (CTI) has increased at an average annual rate of only 2.9x10^-6 (2.3%) for the front- illuminated CCDs and 0.95x10^-6 (6.5%) for the back-illuminated CCDs. This paper describes the current status of Chandra radiation-management program.
O'Dell, Stephen L.↗
Managing Radiation Degradation of CCDs on the Chandra X-Ray Observatory--III
The CCDs on the Chandra X-ray Observatory are vulnerable to radiation damage from low-energy protons scattered off the telescope's mirrors onto the focal plane. Following unexpected damage incurred early in the mission, the Chandra team developed, implemented, and maintains a radiation-protection program. This program--involving scheduled radiation safing during radiation-belt passes, intervention based upon real-time space-weather conditions and radiation-environment modeling, and on-board radiation monitoring with autonomous radiation safing--has successfully managed the radiation damage to the CCDs. Since implementing the program, the charge-transfer inefficiency (CTI) has increased at an average annual rate of only 3.2x 10(exp -6) (2.3 percent) for the front-illuminated CCDs and 1.0x10(exp -6) (6.7 percent) for the back-illuminated CCDs. This paper describes the current status of the Chandra radiation-management program, emphasizing enhancements implemented since the previous papers.
O'Dell, Stephen L.↗
Signatures of Volatiles in the Lunar Proton Albedo
We find evidence for hydrated material in the lunar regolith using "albedo protons" measured with the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). Fluxes of these albedo protons, which are emitted from the regolith due to steady bombardment by high energy radiation (Galactic Cosmic Rays), are observed to peak near the poles, and are inconsistent with the latitude trends of heavy element enrichment (e.g., enhanced Fe abundance). The latitudinal distribution of albedo protons anti-correlates with that of epithermal or high energy neutrons. The high latitude enhancement may be due to the conversion of upward directed secondary neutrons from the lunar regolith into tertiary protons due to neutron-proton collisions in hydrated regolith that is more prevalent near the poles. The CRaTER instrument may thus provide important measurements of volatile distributions within regolith at the Moon and potentially, with similar sensors and observations, at other bodies within the Solar System.
surface↗
Proton-induced noise in digicons
The Space Telescope, which carries four Digicons, will pass several times per day through a low-altitude portion of the radiation belt called the South Atlantic Anomaly. This is expected to create interference in what is otherwise anticipated to be a noise-free device. Two essential components of the Digicon, the semiconductor diode array and the UV transmitting window, generate noise when subjected to medium-energy proton radiation, a primary component of the belt. These trapped protons, having energies ranging from 2 to 400 Mev and fluences at the Digicon up to 4,000 P+/sec-sq cm, pass through both the window and the diode array, depositing energy in each. In order to evaluate the effect of these protons, engineering test models of Digicon tubes to be flown on the High Resolution Spectrograph were irradiated with low-flux monoenergetic proton beams at the University of Maryland cyclotron. Electron-hole pairs produced by the protons passing through the diodes or the surrounding bulk caused a background count rate. This is the result of holes diffusing over a distance of many diode spacings, causing counts to be triggered simultaneously in the output circuits of several adjacent diodes. Pulse-height spectra of these proton-induced counts indicate that most of the bulk-related counts overlap the single photoelectron peak. A geometrical model will be presented of the charge collection characteristics of the diode array that accounts for most of the observed effects.
Smith, L. C.↗
High-energy proton, helium, and gamma-ray observations on OSO-III.
High energy protons, helium and gamma rays observed by particle telescope on board OSO-C, obtaining integral rigidity spectra of proton and helium nuclei
Kapion, M. F.↗
The High Energy Telescope for STEREO
The IMPACT investigation for the STEREO Mission includes a complement of Solar Energetic Particle instruments on each of the two STEREO spacecraft. Of these instruments, the High Energy Telescopes (HETs) provide the highest energy measurements. This paper describes the HETs in detail, including the scientific objectives, the sensors, the overall mechanical and electrical design, and the on-board software. The HETs are designed to measure the abundances and energy spectra of electrons, protons, He, and heavier nuclei up to Fe in interplanetary space. For protons and He that stop in the HET, the kinetic energy range corresponds to approx. 13 to 40 MeV/n. Protons that do not stop in the telescope (referred to as penetrating protons) are measured up to approx. 100 MeV/n, as are penetrating He. For stopping He, the individual isotopes He-3 and He-4 can be distinguished. Stopping electrons are measured in the energy range approx. 0.7 - 6 MeV.
vonRosenvinge, Tycho↗
A proton spectrometer for NASA's Apollo applications program
Particle spectrometer for Apollo measurements of trapped protons and electrons, using directional telescope composed of solid state and scintillation counters
Guenther, G. A.↗
Design of the Experimental Exposure Conditions to Simulate Ionizing Radiation Effects on Candidate Replacement Materials for the Hubble Space Telescope
In this effort, experimental exposure times for monoenergetic electrons and protons were determined to simulate the space radiation environment effects on Teflon components of the Hubble Space Telescope. Although the energy range of the available laboratory particle accelerators was limited, optimal exposure times for 50 keV, 220 keV, 350 keV, and 500 KeV electrons were calculated that produced a dose-versus-depth profile that approximated the full spectrum profile, and were realizable with existing equipment. For the case of proton exposure, the limited energy range of the laboratory accelerator restricted simulation of the dose to a depth of .5 mil. Also, while optimal exposure times were found for 200 keV, 500 keV and 700 keV protons that simulated the full spectrum dose-versus-depth profile to this depth, they were of such short duration that the existing laboratory could not be controlled to within the required accuracy. In addition to the obvious experimental issues, other areas exist in which the analytical work could be advanced. Improved computer codes for the dose prediction- along with improved methodology for data input and output- would accelerate and make more accurate the calculational aspects. This is particularly true in the case of proton fluxes where a paucity of available predictive software appears to exist. The dated nature of many of the existing Monte Carlo particle/radiation transport codes raises the issue as to whether existing codes are sufficient for this type of analysis. Other areas that would result in greater fidelity of laboratory exposure effects to the space environment is the use of a larger number of monoenergetic particle fluxes and improved optimization algorithms to determine the weighting values.
Smith, L. Montgomery↗
Charge-Sign Dependent Cosmic-Ray Modulation Observed with the Calorimetric Electron Telescope on the International Space Station
We present the observation of a charge-sign dependent solar modulation of galactic cosmic rays (GCRs) with the Calorimetric Electron Telescope onboard the International Space Station over 6 yr, corresponding to the positive polarity of the solar magnetic field. The observed variation of proton count rate is consistent with the neutron monitor count rate, validating our methods for determining the proton count rate. It is observed by the Calorimetric Electron Telescope that both GCR electron and proton count rates at the same average rigidity vary in anticorrelation with the tilt angle of the heliospheric current sheet, while the amplitude of the variation is significantly larger in the electron count rate than in the proton count rate. We show that this observed charge-sign dependence is reproduced by a numerical “drift model” of the GCR transport in the heliosphere. This is a clear signature of the drift effect on the long-term solar modulation observed with a single detector.
O. Adriani↗
Observations of energetic Jovian electrons and protons
The Goddard/University of New Hampshire experiment aboard Pioneers 10 and 11 used high and low energy telescopes to measure the nucleon and electron components of the Jupiter magnetosphere. Proton energy spectra are of the form E to the -4th in the outer region and become more complex in the inner region. Particle absorption by several of Jupiter's satellites is an important effect which clearly establishes that radial diffusion is the dominant acceleration process in this region. Observed electron bursts or increases were typically several hundred times the normal quiet-time electron flux, resulting in the quasi-continuous presence of these electrons in interplanetary space. It is suggested that Jupiter could be the source of most of the ambient low energy electrons in the heliosphere.
Mcdonald, F. B.↗
Proton Straggling in Thick Silicon Detectors
Straggling functions for protons in thick silicon radiation detectors are computed by Monte Carlo simulation. Mean energy loss is constrained by the silicon stopping power, providing higher straggling at low energy and probabilities for stopping within the detector volume. By matching the first four moments of simulated energy-loss distributions, straggling functions are approximated by a log-normal distribution that is accurate for Vavilov k is greater than or equal to 0:3. They are verified by comparison to experimental proton data from a charged particle telescope.
Selesnick, R. S.↗
Response of Silicon-Based Linear Energy Transfer Spectrometers: Implication for Radiation Risk Assessment in Space Flights
There is considerable interest in developing silicon-based telescopes because of their compactness and low power requirements. Three such telescopes have been flown on board the Space Shuttle to measure the linear energy transfer spectra of trapped, galactic cosmic ray, and solar energetic particles. Dosimeters based on single silicon detectors have also been flown on the Mir orbital station. A comparison of the absorbed dose and radiation quality factors calculated from these telescopes with that estimated from measurements made with a tissue equivalent proportional counter show differences which need to be fully understood if these telescopes are to be used for astronaut radiation risk assessments. Instrument performance is complicated by a variety of factors. A Monte Carlo-based technique was developed to model the behavior of both single element detectors in a proton beam, and the performance of a two-element, wide-angle telescope, in the trapped belt proton field inside the Space Shuttle. The technique is based on: (1) radiation transport intranuclear-evaporation model that takes into account the charge and angular distribution of target fragments, (2) Landau-Vavilov distribution of energy deposition allowing for electron escape, (3) true detector geometry of the telescope, (4) coincidence and discriminator settings, (5) spacecraft shielding geometry, and (6) the external space radiation environment, including albedo protons. The value of such detailed modeling and its implications in astronaut risk assessment is addressed. c2001 Elsevier Science B.V. All rights reserved.
manned↗
Spectral reflectance and albedo of Apollo 11 lunar samples - Effects of irradiation and vitrification and comparison with telescopic observations
Apollo 11 rocks spectral reflectance and albedo before/after proton irradiation and vitrification, investigating color differences for lunar surface dark and bright areas
Conel, J. E.↗
Energetic particles and coronal mass ejections in the high latitude heliosphere: Ulysses-LET observations
The COSPIN Low Energy Telescope (LET) onboard the Ulysses spacecraft measures protons, alphas and heavier ions at energies of approximately 1 to 50 MeV/n. Ulysses measurements offer favorable opportunities to study the effects of solar activity in the out-of-ecliptic regions of the heliosphere. Using LET data, we have investigated the properties of transient energetic ions at high heliographic latitudes when Ulysses was permanently immersed in high speed solar wind and magnetically connected to the Sun on open magnetic field lines. Recurrent increases in the fluxes of energetic ions at high heliographic latitudes at frequencies related to the solar rotation period were found to occur in association with co-rotating interaction regions (CIRs). Here we investigate fluxes of energetic particles that showed no relationship to ClRs. From the investigation of plasma and magnetic held data it is found that all of the transient high latitude particle events were associated with the passage of a coronal mass ejection (CME) over Ulysses. Enhancements in particle fluxes several days prior to the arrival of a CME, but with a significant time delay with respect to the estimated CME-onset at the Sun, were most probably associated with interplanetary shocks driven by fast CMEs. These particle events exhibit unusually high rho/alpha-ratios and are not observed for CMEs not driving a shock. However, not all CMEs that passed Ulysses were associated with a particle event. We find evidence that at high solar latitudes, solar flare particles cannot reach Ulysses on open magnetic field lines, but can reach the spacecraft if particles are injected into magnetic flux-ropes (CMEs) at the Sun. These findings are supported by soft X-ray observations from the Japanese Yohkoh-satellite.
Bothmer, V.↗