Документ взят из кэша поисковой машины. Адрес оригинального документа : http://xmm.vilspa.esa.es/external/xmm_sw_cal/icwg/presentations/HEXTE_cal_ROTHSCHILD.pdf Дата изменения: Mon Jun 19 18:34:29 2006 Дата индексирования: Sat Dec 22 15:18:12 2007 Кодировка: Поисковые слова: южная атлантическая аномалия

HEXTE Phoswich Detector

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HEXTE Features

Aperture Modulator

AGC Detector

"Mu Metal" Housing

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Calibration Workshop, Iceland 2006

Particle Monitor

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RXTE/HEXTE Design and Calibration

· Calibration begins with instrument design. · Instrument design begins with previous experience, "Oh, if I only could have ..." · and advances with a clear statement of top level requirements. "HEXTE will measure point-like X-ray sources within the intensity range 0.01 to 100 times background in the 15--250 keV range with 10 µs time resolution and better than 18% energy resolution" · Control of systematics allows for easier calibrations.

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HEXTE Features to Address Systematics

Problem
Source Confusion Magnetic Field Variations (>10 s) Phototube Aging Detector Interface Degradation Summing Data from Different Detectors Magnetic Field Variations (<1 minute) Cosmic Ray Induced Background Variations Knowledge of Observation Background Source Confusion in Background Region Magnetic Field Variations (<10 s) PMT Aging due to SAA Charged Particle Background 6/19/2006

Solution
Narrow Field of View Automatic Gain Control Automatic Gain Control Automatic Gain Control Automatic Gain Control Aperture Modulation Aperture Modulation Aperture Modulation Aperture Modulation Magnetic Shielding Particle Monitor Particle Shields 4

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HEXTE Aperture Modulation Pattern

Cen A

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HEXTE Calibration Spectrum The tagged
241

Am spectrum can be used beyond gain control.

1) Measurement of individual detector Energy Resolution 2) Measurement of HEXTE Energy Resolution (7 or 8 summed detectors) 3) Dead time measurement for intervals of >10 minutes

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HEXTE Ground Calibration -- Instrument Response

Synchrotron Source at Brookhaven National Lab plus laboratory fluorescent targets and sources were used to measure the HEXTE NaI response to X-rays. The response shape was spline fit for input to the response generator. Kescape fraction versus energy was also measured at Brookhaven.
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HEXTE Calibration -- Energy Resolution

All of the detectors could not be taken to the synchrotron beam for detailed calibration. Use the beam results to get general shape and then use lab sources to match each detector to the general shape. Laboratory fluorescent targets and sources gave the energy resolution vs energy, that was fit to a two parameter quadratic.

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HEXTE Collimator Response -- Ground Measurement

Measurements made in two orthogonal directions for the hexagonally shaped collimator elements -- point to point and flat to flat. With the 241Am source "only" 110 feet away, one must correct for dispersion in the point source "beam".

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HEXTE Calibration Efforts Once in Orbit · Scan across Crab Nebula at different offsets to measure true aperture response to parallel beam of X-rays. This yields open area per detector and mounting offsets · Measure phoswich efficiency for rejecting charged particle and multiple site events (I.e., Compton scattering or K-escape into CsI) · Measure Crab spectrum and "fudge" instrument response to get "universal value". · Measure Crab pulsar timing to determine offsets, if any, to universal time.

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HEXTE Crab Observations in AO1 and AO5 = 2.078±0.003 F20
-100 keV

= 2.088 ±0.003 F20
-100 keV

= 1.792±0.003

= 1.813±0.003

Bkd Correction=0.07±0.11% Livetime (src) = 23,465 s Livetime (bkg) = 17,644 s

Bkg Correction=0.58±0.10% Livetime (src) = 19,183 s Livetime (bkg) = 16,920 s

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