Photonuclear reaction based high-energy x-ray spectrometer to cover from 2 MeV to 20 MeV.

A photonuclear-reaction-based hard x-ray spectrometer is developed to measure the number and energy spectrum of fast electrons generated by interactions between plasma and intense laser light. In this spectrometer, x-rays are converted to neutrons through photonuclear reactions, and the neutrons are counted with a bubble detector that is insensitive to x-rays. The spectrometer consists of a bundle of hard x-ray detectors that respond to different photon-energy ranges. Proof-of-principle experiment was performed on a linear accelerator facility. A quasi-monoenergetic electron bunch (Ne = 1.0 × 10(-6) C, Ee = 16 ± 0.32 MeV) was injected into a 5-mm-thick lead plate. Bremsstrahlung x-rays, which emanate from the lead plate, were measured with the spectrometer. The measured spectral shape and intensity agree fairly well with those computed with a Monte Carlo simulation code. The result shows that high-energy x-rays can be measured absolutely with a photon-counting accuracy of 50%-70% in the energy range from 2 MeV to 20 MeV with a spectral resolution (Δhν/hν) of about 15%. Quantum efficiency of this spectrometer was designed to be 10(-7), 10(-4), 10(-5), respectively, for 2-10, 11-15, and 15-25 MeV of photon energy ranges.

[A clinical study on patients detected Pasteurella multocida from sputum].

We reported ten cases, (four female and six male), whose sputum cultures positive for Pasteurella multocida from 1990 to 2000. In the past eleven years increasing numbers of cases have appeared in our hospital. The majority of the cases with P. multocida possessed some underlying pulmonary diseases (seven cases, 70%), inactive lung tuberculosis or bronchiectasis. There were compromised hosts such as high ages person, steroids dependent person and diabetes mellitus patients. P. multocida was almost susceptible to antibioticus (penicillin and cephalosporins), although some erythromycin resistant strains were identified. The cats' oral cavities in our two cases were cultured and P. multocida were isolated. In our survey the prevalence of this organism is as high as 85% in cats. Our data suggests that patients who are in the high infection risk category are easily infected to P. multocida.