In situ 100 MeV proton and gamma radiation testing of 25 Gbaud balanced photoreceivers
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43 PARTICLE ACCELERATORS↗
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Mitigation of Beam Losses in LANSCE Linear Accelerator
Suppression of beam losses is essential for successful operation of high-intensity accelerator facility. The LANSCE accelerator started routine operation in 1972 as a 0.8 MW average proton beam power facility for meson physics research, and delivered highpower beam for a quarter century. The accelerator currently delivers 100 MeV proton beam to Isotope Production Facility (IPF) and 800 MeV H- beams to various experimental areas. The accelerator is equipped with two independent injectors for H + and H - beams, merging at the entrance of a 201.25 MHz Drift Tube Linac (DTL). The DTL performs acceleration up to the energy of 100 MeV. After the DTL, the Transition Region beamline directs a 100 MeV proton beam to the Isotope Production Facility, while the H - beam is accelerated up to the final energy of 800 MeV in an 805- MHz Coupled Cavity Linac. The H - beams, created with different time structure by a lowenergy chopper, are distributed in the Switch Yard (SY) to four experimental areas: the Lujan Neutron Scattering Center equipped with a Proton Storage Ring (PSR), the Weapons Neutron Research facility (WNR), the Proton Radiography facility (pRad), and the Ultra-Cold Neutron facility (UCN). Multi-beam operation requires careful control of accelerator tune to minimize beam losses. In this paper we review main effects affecting beam losses in LANSCE linear accelerator and discuss methods to reduce them.
43 PARTICLE ACCELERATORS↗
Results from the Helios galactic and solar cosmic ray experiment (E7)
Energy spectra, charge composition, and flow patterns of solar and galactic cosmic rays were investigated using three nuclear-particle telescopes on Helios to measure electrons (50 keV to 8 MeV) protons (100 eV to 800 MeV) alpha particles (to 600 MeV per nucleon) heavier elements up to neon, (to 200 MeV per nucleon). The experiment includes a proportional counter to monitor solar X-rays in the range 2 to 8 keV. A collection of solar flare associated particle events are observed whereby coronal effects and spatial distribution of flare particles are determined over almost a whole solar cycle; a typical solar particle events are also observed. Earlier explanations concerning corotating energetic particle streams in the inner and outer solar system are confirmed. Solar modulation of galactic cosmic rays is identified. Gamma ray bursts are detected and the sources in the sky are precisely determined, proving the suspected galactic origin.
Trainor, J. H.↗
Low-energy cosmic ray protons from nuclear interactions of cosmic rays with the interstellar medium.
The intensity of low-energy (less than 100 MeV) protons from nuclear interactions of higher-energy (above 100 MeV) cosmic rays with the interstellar medium is calculated. The resultant intensity in the 10- to 100-MeV range is larger by a factor of 3-5 than the observed proton intensity near earth. The calculated intensity from nuclear interactions constitutes a lower limit on the actual proton intensity in interstellar space.
Wang, H. T.↗
Ulysses particle observations of the March 1991 solar flare events
Observations of energetic ions from the COSPIN instrument on the Ulysses spacecraft at 2.5 AU during the March 1991 series of solar flare events arae presented. The intensity profiles observed during this sequence of events were affected both by the presence of interplanetary shocks and large-scale discontinuities in the magnetic field, the low-energy (about 1 MeV) protons being influenced mainly by the shocks and the discontinuities, and the high-energy (about 100 MeV) protons by the discontinuities. The first shock observed at Ulysses was followed by several discontinuities and a Coronal Mass Ejection (CME) which were probably moving with the shock. Particles following this shock were prevented from propagating freely into the heliosphere by the structure moving with the shock, and were carried along with it. A second shock was followed by a region containing bi-directional particle anisotropies. A subsequent enhancement of low-energy particles suggests the passage of another shock. This was followed by a slow intensity decay which coincided with a second CME and where bi-directional particle anisotropies were again observed.
Sanderson, T. R.↗
The effect of Jupiter's satellites on the diffusion of protons
Proton diffusion data are calculated for the Jovian satellites Amalthea, Io, Europa, Ganymede, and Callisto, assuming an equatorial magnetic field at Jupiter's surface of 10 gauss. The cyclotron radius, bounce period, and drift period are calculated for 1 MeV protons. These characteristics and the proton energy at the satellite, mean life near the satellite before impact, and diffusion time are also calculated for 100 MeV protons which conserve their first adiabatic invariant. The longitudinal distance between successive bounces is of the order of a few satellite radii.
Mead, G. D.↗
Radiation effects induced by the energetic protons in 8x8x32 mm3 CdZnTe detectors
We report CdZnTe (CZT) detectors have been used in the past and are being actively considered for future gamma-ray space telescopes. One of the challenges of operating CZT detectors in low Earth orbit is radiation damage caused by energetic protons. Previous studies concluded that fluences of 10 8 -10 9 p/cm 2 are sufficient to cause shifting of peak positions and degradations of energy resolution. Degradation of detectors after proton irradiation has been extensively investigated to determine their radiation resistance limits and performance recovering procedures for their applications in space and nuclear nonproliferation. Here we present the study of radiation effects induced by 100 MeV protons in 3-cm long CdZnTe detectors that we recently proposed for the gamma-ray telescope GECCO. The goal this study is to evaluate the feasibility of using such long CZT detectors in future space missions.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Direct observation of the exotic β – γ – α decay mode in the T z = – 1 nucleus Na 20
The exotic β – γ – α decay mode of 20 Na has been directly observed for the first time in the Day-one experiment at the Beijing Radioactive Ion-beam Facility. The 20 Na source was produced by using a 100-MeV proton beam bombarding a stack of microporous MgO thick target and delivered as an intense mass separated beam after online ionization. A high-efficiency simultaneous measurement of β, γ, and α transitions enables the β-delayed γ – γ and α – γ coincidence spectroscopy. Here three β – γ – α exotic decay sequences in 20 Na are discovered, which expands the rare decay modes observed in β decay. Moreover, a β – α –decay sequence to the 6130-keV 3 – state of 16 O is observed, which is likely through the 12367-keV 1 + state in 20 Ne. The experimentally deduced B(F) and B(GT) are compared to the shell-model calculation, the allowed β transition strengths can be well accounted for by using sd shell-model space interactions.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Radiation studies of optical and electronic components used in astronomical satellite studies
The synchronous orbit of the IUE carries the satellite through Earth's outer electron belt. A 40 mCi Sr90 source was used to simulate these electrons. A 5 mCi source of Co60 was used to simulate bremmstrahlung. A 10 MeV electron Linac and a 1.7 MeV electron Van de Graaf wer used to investigate the energy dependence of radiation effects and to perform radiations at a high flux rate. A 100 MeV proton cyclotron was used to simulate cosmic rays. Results are presented for three instrument systems of the IUE and measurements for specific components are reported. The three instrument systems were the ultraviolet converter, the fine error sensor (FES), and the SEC vidicon camera tube. The components were optical glasses, electronic components, silicon photodiodes, and UV window materials.
Becher, J.↗
Radiation Tests of the Extravehicular Mobility Unit Space Suit for the International Space Station Using Energetic Protons
Measurements using silicon detectors to characterize the radiation transmitted through the EMU space suit and a human phantom have been performed using 155 and 250 MeV proton beams at LLUMC. The beams simulate radiation encountered in space, where trapped protons having kinetic energies on the order of 100 MeV are copious. Protons with 100 MeV kinetic energy and above can penetrate many centimeters of water or other light materials, so that astronauts exposed to such energetic particles will receive doses to their internal organs. This dose can be enhanced or reduced by shielding - either from the space suit or the self-shielding of the body - but minimization of the risk depends on details of the incident particle flux (in particular the energy spectrum) and on the dose responses of the various critical organs. Data were taken to characterize the beams and to calibrate the detectors using the beam in a treatment room at LLUPTF, in preparation for an experiment with the same beams incident on detectors placed in a human phantom within the EMU suit. Nuclear interactions of high-energy protons in various materials produce a small flux of highly ionizing, low-energy secondary radiation. Secondaries are of interest for their biological effects, since they cause doses and especially dose-equivalents to increase relative to the values expected simply from ionization energy loss along the Bragg curve. Because many secondaries have very short ranges, they are best measured in passive track detectors such as CR-39. The silicon detector data presented here are intended to supplement the CR-39 data in regions where silicon has greater sensitivity, in particular the portion of the LET spectrum below 5 keV/micron. The results obtained in this study suggest that optimizing the radiation shielding properties of space suits is a formidable task. The naive assumption that adding mass can reduce risk is not supported by the data, which show that reducing the dose delivered at or near the skin by low-energy particles may increase the dose delivered by energetic particles to points deeper in the body.
Zeitlin, C.↗
Solar protons E greater than 100 Mev incident over Antarctica during January- February 1967.
Commencing at 0825 +a -1 UT on January 28, 1967, a large and prolonged increase in the intensity of penetrating charged particles was observed by balloon-borne instruments floating over Byrd Station, Antarctica. (80°S, 120°W). A peak intensity of approximately 50 protons per cm 2 -sec-steradian with E> 100 MeV occurred at about 1230 UT on the 28th. The event was under observation almost continuously over a period of about 100 hours until the intensity decayed below cosmic-ray background on February 1. The initial decay was rapid but, some 40 hours after onset, went over into a slow exponential decay characterized by a 20 hour time-constant. The decay phase of an additional, though considerably less intense, event was observed on February 3 and 4. Presumably both events had their origins in major disturbances on the far side of the sun since nether event has been definitely linked to any feature which existed on the visible disk within an appropriate time interval. Results pertaining to the time-intensity profile and to the energy spectrum for protons E> 100 MeV are presented for the January 29 event. Comparison of the balloon results with neutron-monitor and satellite measurements and with models of interplanetary diffusion has led to some conclusions regarding the role of small-angle scattering by irregularities and by the random walk of magnetic lines of force relative to the mean interplanetary field within the orbit of earth.
Energy spectrum↗
Quantification of rat retinal growth and vascular population changes after single and split doses of proton irradiation: translational study using stereology methods
This study quantified architectural and population changes in the rat retinal vasculature after proton irradiation using stereology. A 100 MeV conformal proton beam delivered 8, 14, 20 and 28 Gy as single and split doses to the whole eye. The vascular networks were prepared from retinal digests. Stereological methods were used to obtain the area of the retina and unbiased estimates of microvessel/artery/vein endothelial, pericyte and smooth muscle population, and vessel length. The retinal area increased progressively in the unirradiated, age-matched controls and in the retinas irradiated with 8 and 14 Gy, indicating uniform progressive retinal growth. No growth occurred after 20 and 28 Gy. Regression analysis of total endothelial cell number in all vessels (arteries, veins and capillaries) after irradiation documented a progressive time- and dose-dependent cell loss occurring over 15 to 24 months. The difference from controls was significant (P<0.01) after 28 Gy given in single and split doses and after 20 Gy given as a split dose (P<0.05). Total vessel length in microvessel was significantly shortened at 20 and 28 Gy compared to that of controls (P<0.05). No evident dose recovery was observed in the endothelial populations after split doses. At 10 Gy, the rate of endothelial cell loss, a dose parameter used to characterize the time- and dose-dependent loss of the endothelial population, was doubled.
NASA Discipline Radiation Health↗
SRF Resonators for a bi-directional Energy Ramping Upgrade of the Isotope Production Facility Beamline at LANL
The LANL Isotope Production Facility (IPF) is one of the two high-current proton linear accelerators operated under the auspices of the DOE Office of Nuclear Physics Isotope Development and Production for Research Applications Program. The IPF beamline operates with a fixed 100-MeV energy proton beam, diverted from the LANSCE accelerator and guided towards the isotope production target station. The fixed beam energy limits the number of isotopes that can be produced at IPF, and adversely affects the purity of isotopes produced at non-optimal energies. In particular, the IPF program is receiving increasing numbers of requests for high purity isotopes such as Np-236 (national security applications) and Re-186 (medical therapy). These are typically produced via (p,n) and (p,2n) nuclear reactions, requiring very tight control of the incident energies on the production targets to ensure an end product with a high radionuclidic purity. It is well known that this level of energy control cannot be achieved when a 100 MeV beam of mono-energetic protons is degraded to the required energies, typically below 30 MeV, as too much energy spread is acquired. Operating the IPF beamline at lower, mono-energetic beam energies such as at 40 MeV will allow the required tight energy control in target assemblies to ensure a high purity product. In addition, NP has requested a LANL/BNL/ORNL collaboration focus on establishing a national large-scale production capability for the therapy isotope Ac-225. Recent nuclear cross section measurements done at LANL show that due to a steep rise in production cross section towards higher proton energies (See Figure 2), proton beams at energies substantially greater than 100 MeV will be highly beneficial for Ac-225 production [AC255]. Such higher-energy beams cannot be delivered to IPF at present. Lower-energy beams (70 MeV and 40 MeV) can be delivered but only in sole-use mode; all other LANSCE users must be offline during 70 MeV or 40 MeV operation.
07 ISOTOPE AND RADIATION SOURCES↗
Investigating high-energy proton-induced reactions on spherical nuclei: Implications for the preequilibrium exciton model
A number of accelerator-based isotope production facilities utilize $100-200$ MeV proton beams due to the high production rates enabled by high-intensity beam capabilities and the greater diversity of isotope production brought on by the long range of high-energy protons. However, nuclear reaction modeling at these energies can be challenging because of the interplay between different reaction modes and a lack of existing guiding cross section data. A Tri-lab collaboration has been formed between the Lawrence Berkeley, Los Alamos, and Brookhaven National Laboratories to address these complexities by characterizing charged-particle nuclear reactions relevant to the production of established and novel radioisotopes. In the inaugural collaboration experiments, stacked-targets of niobium foils were irradiated at the Brookhaven Linac Isotope Producer ($E_p=200$ MeV) and the Los Alamos Isotope Production Facility ($E_p=100$ MeV) to measure $^{93}$Nb(p,x) cross sections between $50-200$ MeV. The results were compared with literature data as well as the default calculations of the nuclear model codes TALYS, CoH, EMPIRE, and ALICE. The default code predictions largely failed to reproduce the measurements. Therefore, we developed a standardized procedure, which determines the reaction model parameters that best reproduce the most prominent reaction channels in a physically justifiable manner. Overall, the primary focus of the procedure was to determine the best parameterization for the pre-equilibrium two-component exciton model. This modeling study revealed a trend towards a relative decrease for internal transition rates at intermediate proton energies ($E_p=20-60$ MeV) in the current exciton model as compared to the default values. The results of this work are instrumental for the planning, execution, and analysis essential to isotope production.
43 PARTICLE ACCELERATORS↗
Low energy cosmic ray protons from nuclear interactions of cosmic rays with the interstellar medium
The flux of secondary protons below 100 MeV in interstellar space is calculated using detailed cross sections and kinematics for proton-proton, and proton-alpha particle interactions.
Wang, H. T.↗
Predicting cutoff L-shells of solar protons using the GPPSn particle dataset
Solar energetic protons (SEPs) arriving at the Earth trigger severe radiation storms in the near-Earth space, directly impacting space missions operating at various altitudes. Therefore, monitoring SEP events and predicting the penetration depths of solar protons are critical for aerospace sectors. Building on previous efforts, here we demonstrate the feasibility of using proton measurements from the Global Prompt Proton Sensor network (GPPSn), enabled by Los Alamos National Laboratory developed combined X-ray dosimeters aboard GPS satellites, to characterize and predict the penetration of solar protons into the geomagnetic field. The inclined medium-Earth-orbits (MEOs) of the global GPS constellation offer a unique advantage of allowing simultaneous measurements of penetrating solar protons inside both open- and closed-field line regions. Therefore, the L-profiles of ∼10s–100 MeV solar protons and their associated cutoff L-shells can be determined from the GPPSn dataset, using predefined threshold proton flux values rather than traditional flux ratios. After examining a list of SEP event intervals across solar cycles 23, 24 and 25—including the 2024 Mother’s Day superstorm, we showcase how the latest GPPSn proton dataset (release v1.10), reprocessed and calibrated, can not only be used to monitor solar proton distributions inside the dynamic geomagnetic field for individual events, but also to derive a new empirical model linking cutoff L-shells with several key space weather parameters. This newly developed SEPCL-MEO model demonstrates high predictive performance; for example, predictions for > 30 MeV solar protons yield a correlation coefficient of 0.85 and performance efficiency of 0.67 when validated against GPPSn observations. Results from this pilot study underscores the scientific and operational value of the GPPSn dataset, and this dataset—when paired with machine-learning techniques—can play a critical role in observing and predicting the effects of future incoming SEP events, including extreme ones.
58 GEOSCIENCES↗
Displacement damage in silicon due to secondary neutrons, pions, deuterons, and alphas from proton interactions with materials
This paper examines the enhancement of displacement damage energy deposition due to secondary neutrons, pions, deuterons, and alphas resulting from high energy (100-1000MeV) proton interactions with aluminum and tungsten shielding.
displacement↗
Novel design and diagnostics improvements for increased production capacity and improved reliability at the Los Alamos Isotope Production Facility
The Isotope Production Facility (IPF) at Los Alamos National Laboratory (LANL) is used to produce an array of isotopes for medical, global security, and research applications with an intense beam of protons supplied by the linear accelerator at the Los Alamos Neutron Science Center (LANSCE). An Accelerator Improvement Project (AIP) was recently conducted at IPF to improve facility reliability and reduce programmatic risk while increasing general isotope production capacity and flexibility. This was accomplished through the installation of an improved beam window assembly, more robust beam diagnostics, an active and adjustable collimator, and a new beam rastering system. This paper will highlight the four exciting innovations and how they were designed, validated, and installed in parallel as well as the significant operational advantages they provide to IPF. Key experiments and the increased currents achieved in routine production runs demonstrating the enhanced capability from the AIP will be presented. As a result, the most notable capability enhancements include irradiations with beam currents ranging from 100 nA experimental runs up to 300 μA on routine production targets and utilization of a range of cylindrical target diameters.
100 MeV protons↗