121784430
Simple technique for determining the mean lifetime of the cosmic ray μ meson
A single scintillation counter is used for determining the lifetime of cosmic ray μ mesons. The experimental arrangement has a greater detection rate and a higher detection efficiency than the conventional multidetector delayed coincidence technique.
121844770
The age distribution of galactic cosmic rays
The general solution for the distribution of ages for primary galactic cosmic rays is given for a class of steady-state, bounded models of cosmic-ray diffusion in the Galaxy. Both one-and threedimensional models are considered, with point sources and distributed sources. In all models, the age distribution, is approximately exponential for ages longer than the average age, although for shorter ages the distribution depends on the details of the model. The leaky-box model, with an exponential age distribution, is thus a good approximation to most diffusive models. It is shown that one-dimensional (‘disk’) models are consistent with both age and anisotropy data for galactic cosmic rays regardless of whether production takes place near the galactic center or throughout the disk.
123383571
The interplanetary transport of solar cosmic rays
Numerical solutions are presented for the propagation of solar cosmic rays in interplanetary space, including the effects of pitch-angle scattering and adiabatic focusing. The intensity-time profiles can be well fitted by a simple radial spatial diffusion equation with scattering mean-free path lambda/sub fit/. The radial mean-free path so obtained is significantly larger than the true scattering mean-free path for low-rigidity particles due to both adiabatic focusing and the inapplicability of the diffusive approximation early in the event. The well-known discrepancy between lambda/sub fit/ and the theoretical predictions may be resolved by these calculations.
117706405
Two-component model for cosmic-ray fluctuations at neutron monitor energies
118212086
A Simple Model for Galactic Cosmic Rays which is Consistent with Age and Anisotropy Data
118987428
Camtrac - A high energy gamma-ray telescope utilizing a coded aperture mask and drift chambers
123408840
Effect of prolonged annealing on the performance of coaxial Ge gamma-ray detectors.
The effects of prolonged annealing at elevated temperatures have been investigated in a 53cm3 closed-end coaxial high purity germanium detector in the reverse electrode configuration. The detector was multiply annealed at 100°C in block periods of 7 days. After each anneal cycle it was cooled to 77 K and the relative efficiency, peak channel location and FWHM energy resolution measured at 6 gamma-ray energies. At the present time, the detector has completed 16 anneal cycles. It was found that above ~ 662 keV the photopeak efficiency decreased almost linearly at a rate of ~ 1.5% per anneal cycle, although the energy resolution and centroid (and therefore charge collection efficiency) remained unchanged. The change in detection efficiency is attributed to the expansion of the inner n+ contact due to the thermal drive-in of Li ions into the bulk. The rate is found to follow a power-law dependence in agreement with that expected from Fick's diffusion laws. Using these data, we have derived a simple 1-D phenomenological model in which the n+ contact thickness is simply related to the Li diffusion length. For annealing at 100°C, the thickness of the n+ contact, d, as a function of the annealing time, t, can be described semi-empirically by d(mm) = 0.231 × t(days)1/2.
122362177
Synchrotron light sources and radiation detector metrology
Abstract Synchrotron light sources are widely used in materials science, protein crystallography and biomicroscopy applications. They provide a unique stable source of high intensity photons, extending over a broad energy range from the far infrared to the γ-ray region. However, they have also proven invaluable for carrying out detailed metrology of radiation detectors by making available highly collimated and controllable monochromatized beams of synchrotron radiation. Light sources are only accessible at synchrotron research facilities and a number of specialized laboratories (for example, the Physikalisch-Technische Bundesanstalt (PTB), radiometry laboratories in Berlin, Germany) have been established specifically to be carry out photon metrology from the UV to the X-ray wavelengths using primary source standards in conjunction with primary detector standards. In this review, we discuss the use of synchrotron radiation for characterizing and calibrating X- and gamma-ray radiation detectors.
17797650
Iron line signatures in X-ray afterglows of GRB by BeppoSAX
We report the possible detection (99.3% of sta- tistical signicance) of redshifted Fe iron line emission in the X-ray afterglow of Gamma-ray burst GRB 970508 ob- served by BeppoSAX. Its energy is consistent with the redshift of the putative host galaxy determined from op- tical spectroscopy. In contrast to the fairly clean environ- ment expected in the merging of two neutron stars, the observed line properties would imply that the site of the burst is embedded in a large mass of material (> 0:5M), consistent with pre-explosion ejecta of a very massive star. This material could be related with the outburst observed in the afterglow 1 day after the GRB and with the spectral variations measured during this phase. We did not nd ev- idence of Fe line in two other GRB with known redshift (GRB 971214 and GRB 980613), but we note that the up- per limits are of the same order of the intensity measured in GRB 97508 and that none of these afterglows shows rebursting activity.
85524570
The X-Ray, Optical, and Infrared Counterpart to GRB 980703
We report on X-ray, optical, and infrared follow-up observations of GRB 980703. We detect a previously unknown X-ray source in the GRB error box; assuming a power-law decline, we find for its decay index α 1.3 × 1017 Hz. For this epoch we obtain an extinction of AV = 1.50 ± 0.11. From the X-ray data we estimate the optical extinction to be AV = 20.2+12.3-7.3, inconsistent with the former value. Our optical spectra confirm the redshift of z = 0.966. We compare the afterglow of GRB 980703 with that of GRB 970508 and find that the fraction of the energy in the magnetic field, B < 6 × 10-5, is much lower in the case of GRB 980703, as a consequence of the high frequency of the cooling break.
6164184
Evidence for a late-time outburst of the X-ray afterglow of GB970508 from BeppoSAX
The ray burst GB970508 was observed simulta- neously by the Gamma Ray Burst Monitor (GRBM) and one of the X-ray Wide Field Cameras (WFC) aboard BeppoSAX. The latter provided a position within 1:9 0 radius. A series of follow- up observations with the Narrow Field Intruments (NFI) was then performed in a period from 6 hours to 6 days after the main event. A previously unknown source, which we associate with the afterglow of the GRB, was discovered in the error box. Wendthat,aftertheinitialburst,X-rayemissionisstillpresent and decays as t 1:1 up to 6 10 4 s. This is followed by a burst of activity with a duration 10 5 s. The energy produced in this event is a substantial fraction of the total energy of the GRB, which means that the afterglow is not a remnant of the initial burst (the GRB) that fades away smoothly. Our results support the idea that the processes generating the GRB and its afterglow are the same.