RESUMEN
A tissue equivalent proportional counter designed to measure the linear energy transfer spectra (LET) in the range 0.2-1250 keV/micrometer was flown in the Kvant module on the Mir orbital station during September 1994. The spacecraft was in a 51.65 degrees inclination, elliptical (390 x 402 km) orbit. This is nearly the lower limit of its flight altitude. The total absorbed dose rate measured was 411.3 +/- 4.41 microGy/day with an average quality factor of 2.44. The galactic cosmic radiation (GCR) dose rate was 133.6 microGy/day with a quality factor of 3.35. The trapped radiation belt dose rate was 277.7 microGy/day with an average quality factor of 1.94. The peak rate through the South Atlantic Anomaly was approximately 12 microGy/min and nearly constant from one pass to another. A detailed comparison of the measured LET spectra has been made with radiation transport models. The GCR results are in good agreement with model calculations; however, this is not the case for radiation belt particles and again points to the need for improving the AP8 omni-directional trapped proton models.
Asunto(s)
Radiación Cósmica , Transferencia Lineal de Energía , Modelos Teóricos , Protones , Actividad Solar , Vuelo Espacial/instrumentación , Brasil , Neutrones , Dosis de Radiación , Monitoreo de Radiación/instrumentación , Radiometría/instrumentaciónRESUMEN
Measurements of the energy spectra of secondary particles produced by galactic cosmic rays and trapped protons due to the nuclear interactions of these particles with the Shuttle shielding provide a powerful tool for validating radiation transport codes. A code validated in this way can be used to better estimate the dose and dose equivalent to body organs, measurements that cannot be made directly. The principal cause of single event upsets in electronic devices in the region of the South Atlantic Anomaly is secondary particles, and even in the region of galactic cosmic radiation a significant fraction is produced by secondary particles. In this paper, we describe the first direct measurements of the energy spectra of secondary protons, deuterons, tritons, 3He and 4He produced by galactic cosmic rays inside the Space Shuttle using a charged particle spectrometer. A comparison of these spectra with radiation transport code HZETRN showed reasonably good agreement for secondary protons. However, the code seriously underestimated the flux of all other light ions. The code has been modified to include pick-up and knock-on processes. The modified code leads to good agreement for deuterons and 3He but not for other light ions. This revised code leads to about 10% higher dose equivalent than the original code under moderate shielding, if we assume that higher charge ion fluxes are correctly predicted by the model.
Asunto(s)
Radiación Cósmica , Interacciones de Partículas Elementales , Monitoreo de Radiación/instrumentación , Actividad Solar , Vuelo Espacial/instrumentación , Nave Espacial/instrumentación , Océano Atlántico , Deuterio , Procesamiento Automatizado de Datos , Diseño de Equipo , Medio Ambiente Extraterrestre , Helio , Transferencia Lineal de Energía , Modelos Teóricos , Protones , América del SurRESUMEN
We have flown two new charged particle detectors in five recent Shuttle flights. In this paper we report on the dose rate, equivalent dose rate, and radiation quality factor for trapped protons and cosmic radiation separately. A comparison of the integral linear energy transfer (LET) spectra with recent transport code calculations show significant disagreement. Using the calculated dose rate from the omni-directional AP8MAX model with IGRF reference magnetic field epoch 1970, and observed dose rate as a function of (averaged over all geographic latitude) and longitude, we have determined the westward drift of the South Atlantic anomaly. We have also studied the east-west effect, and observed a 'second' radiation belt. A comparison of the galactic cosmic radiation lineal energy transfer spectra with model calculations shows disagreement comparable to those of the trapped protons.
Asunto(s)
Radiación Cósmica , Protones , Monitoreo de Radiación/instrumentación , Vuelo Espacial/instrumentación , Océano Atlántico , Transferencia Lineal de Energía , Dosis de Radiación , Monitoreo de Radiación/métodos , Monitoreo de Radiación/estadística & datos numéricos , Radiometría/instrumentación , América del Sur , Nave Espacial/instrumentaciónRESUMEN
Two new charged particle detectors have been flown in five recent Shuttle flights. The tissue-equivalent proportional counter measures the lineal energy spectrum of space radiation in the 0.26-300 keV micrometer-1 range. The charged particle spectrometer is a double dE/dx x E and dE/dx x Chrenekov detector system which provides a measurement of the differential energy spectrum of protons from 13 to 350 MeV and dose rate in silicon. In this paper the dose rate, equivalent dose rate, and radiation, quality factor for trapped protons and cosmic radiation are reported on separately. A comparison of the integral LET spectra with recent transport code calculations shows significant disagreement. Using the calculated dose rate from the omnidirectional AP8MAX model with IGRF reference magnetic field epoch 1970, and observed dose rate as a function of geographic latitude and longitude, the westward drift of the south Atlantic anomaly has been determined. The east-west effect has also been studied and a 'second' radiation belt observed. A comparison of the galactic cosmic radiation (GCR) lineal energy transfer spectra with model calculations shows disagreement comparable with those of the trapped protons.