26132013
Towards hard x-ray imaging at GHz frame rate.
Gigahertz (GHz) imaging using hard x-rays (> or approximately equal to 10 keV) can be useful to high-temperature plasma experiments, as well as research and applications using coherent photons from synchrotron radiation and x-ray free electron lasers. GHz framing rate can be achieved by using multiple cameras through multiplexing. The advantages and trade-offs of single-photon detection mode, when no more than one x-ray photon is detected per pixel, are given. Two possible paths towards x-ray imaging at GHz frame rates using a single camera are: (a) avalanche photodiode arrays of high-Z materials and (b) microchannel plate photomultipliers in conjunction with materials with large indices of refraction.
118530343
Tracking fast neutrons
Abstract Both neutron absorption and elastic scattering can be used to measure neutron momentum. Based on elastic collisions, the linear momentum of a fast neutron can be measured from as few as two consecutive recoil ion tracks plus the vertex position of the third collision, or ‘two and half’ ion tracks. If the time delay between the first two consecutive ion tracks is also measured, the number of ion tracks can be reduced to one and a half. The angular and magnitude resolutions are limited by ion range straggling to about 10%. Multi-wire proportional chambers and light-field imaging can be used for fast neutron tracking. Light-field imaging is free of charge-diffusion-induced image blur, but the limited number of photons available can be a challenge. 1 H, 2 H and 3 He could be used for the initial development of fast neutron trackers based on light-field imaging.
14349816
The Near-infrared Counterpart to the Anomalous X-ray Pulsar 1e 1048.1−5937
We report our discovery of the likely near-infrared counter part to the anomalous X-ray pulsar (AXP) 1E 1048.1−5937, using observations from the 6.5 m Baade (Magellan I) te lescope in Chile. We derived a precise position for the X-ray source using archival data from t heChandra X-Ray Observatory. Since this position is inconsistent with a position reported earlier from XMM-Newton, we conservatively considered eight optical and near-infrared sources within both error circles as cand id te counterparts, although we also show that the XMM-Newton observation likely suffered from attitude reconstruction problems. Two of the infrared objects have unusual colors, and one of these has colors consistent with t hose of the identified counterparts of two other AXPs. The latter object is the only source detected within the Chandra error circle, and we identify it as the counterpart to 1E 1048.1 −5937. This is the first AXP counterpart detected in multiple i nfrared bands, with magnitudes J=21.7(3),H=20.8(3), andK=19.4(3). There is marginal evidence for spectral flattenin g at longer wavelengths. Subject headings: pulsars: individual (1E 1048.1 −5937) — stars: neutron
119219005
Analysis of the doubly heavy baryons in the nuclear matter with the QCD sum rules
In this article, we study the doubly heavy baryon states Ξcc, Ωcc, Ξbb and Ωbb in the nuclear matter using the QCD sum rules, and derive three coupled QCD sum rules for the masses, vector self-energies and pole residues. The predictions for the mass-shifts in the nuclear matter $\Delta M_{\varXi_{cc}}=-1.11~\mbox{GeV}$, $\Delta M_{\varOmega_{cc}}=-0.33~\mbox{GeV}$, $\Delta M_{\varXi_{bb}}=-3.37~\mbox{GeV}$ and $\Delta M_{\varOmega_{bb}}=-1.05~\mbox{GeV}$ can be confronted with experimental data in the future.
27616584
Radial compression of protons and H3+ ions in a multiring trap for the production of ultralow energy antiproton beams.
Radial compression of a proton cloud was performed in a multiring trap which was designed to trap and cool a large number of antiprotons for the production of low-energy ( 10-1000 eV ) antiproton beams. The resonance frequency for the radial compression was almost constant from 3 x 10(5) to 3 x 10(6) protons. The collision process of the trapped protons was also investigated to estimate the energy of the protons inside the trap. This technique will be applied to the ASACUSA experiment at the antiproton decelerator, CERN, to extract ultraslow antiprotons with good emittance.
119548246
Subarcsecond Resolution Mid-Infrared Observations of Super Star Clusters in the Antennae (NGC 4038/4039)*
We present ground-based subarcsecond mid-infrared imaging and spectroscopy of young super star clusters in the overlap region of the merging galaxies NGC 4038/4039 (the Antennae) obtained with the VLT Imager and Spectrometer for mid-InfraRed (VISIR). With its unprecedented spatial resolution, VISIR begins for the first time to resolve the H II/photodissociation region complexes around the star-forming regions. In the N-band spectra of two young star clusters, unexpectedly low polycyclic aromatic hydrocarbon (PAH) emission is observed, compared to what is seen with the Infrared Space Observatory and with the Spitzer Space Telescope. We conclude that a large fraction of the PAH emission cannot be directly associated with the super star clusters but originates from an extended region of at least 215 pc radius around the clusters. In the distribution of [Ne II] 12.81 μm emission, a highly obscured cluster is discovered that does not have an optical or near-infrared counterpart.
13852548
Optical/Infrared Observations of the Anomalous X-Ray Pulsar 1E 1048.1-5937 During Its 2007 X-Ray Flare
We report on optical and infrared observations of the anomalous X-ray pulsar (AXP) 1E 1048.1–5937 made during its ongoing X-ray flare that started in 2007 March. We detected the source in the optical I and near-infrared Ks bands in two ground-based observations and obtained deep flux upper limits from four observations, including one with the Spitzer Space Telescope at 4.5 and 8.0 μm. The detections indicate that the source was approximately 1.3-1.6 mag brighter than in 2003-2006, when it was at the tail of a previous similar X-ray flare. Similar related flux variations have been seen in two other AXPs during their X-ray outbursts, suggesting common behavior for large X-ray flux variation events in AXPs. The Spitzer flux limits are sufficiently deep that we can exclude mid-infrared emission similar to that from the AXP 4U 0142+61, which has been interpreted as arising from a dust disk around the AXP. The optical/near-infrared emission from 1E 1048.1–5937 probably has a magnetospheric origin. The similarity in the flux spectra of 1E 1048.1–5937 and 4U 0142+61 challenges the dust disk model proposed for the latter.