Документ взят из кэша поисковой машины. Адрес оригинального документа : http://hea-www.harvard.edu/~bradw/home/xtej1118_xray.html
Дата изменения: Unknown
Дата индексирования: Sun Apr 10 09:06:01 2016
Кодировка:
Поисковые слова: п п п п п п п п п р п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п р п п п р п р п п р п р п п р п

Above is an image of a Chandra Low Energy Transmission Grating (LETG) spectrum of a very bright X-ray source, the nova XTE J1118+480, showing only the shortest wavelengths. The major features are:

Bright spot in center = the source (i.e., 0th order of the spectrum)
Bright diagonal line extending corner to corner = the main dispersed spectrum (1st and higher orders)
Bright line perpendicular to the main spectrum = cross-dispersion spectrum of 0th order, caused by the LETG fine-support structure
Faint six-pointed star pattern in the center = diffraction of 0th order by the triangle-pattern coarse-support structure
Faint fan of whiskers on either side = cross-dispersion orders caused by the fine-support structure. The main dispersed spectrum is 0th order of the cross-dispersion spectrum.

My primary job is to:

Calibrate the intensities of the various LETG diffraction components shown above
Calibrate the responses and efficiencies of the detectors (ACIS and HRC) used to record grating spectra
Monitor detector changes over time and adjust operating parameters when necessary
Develop methods to reduce detector background
Assist LETG observers in setting up their observations.

I also conduct my own research, often using Chandra data, mostly on solar wind charge exchange and stellar coronae. My graduate school research was on X-ray atomic physics using an Electron Beam Ion Trap (EBIT). After that I was hired by SAO to help build the system used to collect Chandra pre-flight ground calibration data (the HXDS) and then analyze those data. After launch I switched over to the CXC Calibration group to work on the LETG.