Calibration of x-ray and gamma-ray measuring instruments

Abstract

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Scatter Corrections in X-Ray Computed Tomography: A Physics-Based Analysis

“…We chose a 150 kV tube spectrum with a 5 mm Al filter and a 0.25 mm Cu filter using TASMICS [26]. The filter was chosen to match the M150 beam quality that is used to calibrate X-ray detectors at NIST [27].…”

The Metrology of a Rastered Spot of X Rays used in Security Screening

“…By way of illustration, we report the incident air kerma for the Rapiscan Secure 1000 Single Pose scanner that employed an x-ray tube potential of 50 kV. Both the Radcal 10X5-1800 ionization chamber and an RTI R100B solid-state detector (sensitive area 1 cm 2 ) were calibrated using the NIST M50 standard beam quality [12]. The IC readings were also corrected for ambient temperature and pressure relative to standard environmental conditions.…”

“…The red data points were acquired using the same source (and therefore the same NIST M50 reference beam) that was used to calibrate the Radcal 10X5-1800 IC to the NIST M50 standard beam quality, a good proxy for the source represented with blue data points labeled Vendor B (Rapiscan Secure 1000 Single Pose scanner) [13]. The calibration data were recorded by the Ritz ionization chamber [12] positioned at the height of the fixed calibration source, as the stand off-distance is varied. The air kerma rate, and dose levels from the calibration source, exhibit the expected inverse square-law dependence with distance; these absolute rates have been scaled to the tube current (5 mA [6]) of Vendor B, and, in the absence of a direct measurement, the rates were multiplied by the pass-by time of the backscatter system of Table 2 (35 µs) to obtain the NIST air kerma values that are plotted.…”

“…The scanner data were acquired by a Radcal 10X5-1800 IC with the appropriate calibration factors applied. The M50 beam (HVL = 1.04 mm Al) was measured by the Ritz national standard ionization chamber [12] during calibration of the Radcal IC.…”

“…The curve is an inverse-square fit to measurements (circular plot symbols) acquired by the NIST Ritz free-air ionization chamber, a primary national standard for x-ray beams between 20 kV and 100 kV [12]. The data were acquired at 2 mA tube current, and normalized to 5 mA as a proxy for the Rapiscan Secure 1000 Single Pose scanner [6].…”