Absolutely Calibrating an Absolutely Calibrating an Energy Dispersive DetectorEnergy Dispersive Detector

Patrick Ross

Spring Research Conference

Why?Why?

Absolute Calibration provides more Absolute Calibration provides more information.information.

Applications in Medical ResearchApplications in Medical Research

Materials ScienceMaterials Science Use in material analysis (X-Ray Diffraction/ Use in material analysis (X-Ray Diffraction/

X-Ray Florescence) X-Ray Florescence)

Our DetectorOur Detector

CCD: A spacially resolving detectorCCD: A spacially resolving detector

Methods of CalibrationMethods of Calibration

We are attempting to calibrate the detector We are attempting to calibrate the detector using a calibrated source (using a calibrated source (±5%).±5%).

We confirmed the source’s calibration with:We confirmed the source’s calibration with:

Proportional CounterProportional Counter

PIN DiodePIN Diode

Proportional CounterProportional Counter

Problems with the Proportional Problems with the Proportional CounterCounter

Obscure geometry of detectorObscure geometry of detector

Pressure problems (P-10 Gas)Pressure problems (P-10 Gas)

Solid angle problems (measuring the Solid angle problems (measuring the depth of the window)depth of the window)

PIN DiodePIN Diode

Calibrating the CCDCalibrating the CCD

X-ray source

Detector 1

Detector 2

So, how is a CCD an energy So, how is a CCD an energy dispersive detector?dispersive detector?

It isn’t, But…

Von Hamos SpectrometerVon Hamos Spectrometer

Von Hamos SpectrometerVon Hamos Spectrometer

Single Crystal

CCD

λ λ’

θ θ’

Increasing the Signal to NoiseIncreasing the Signal to Noise

Von Hamos spectrometer disperses Von Hamos spectrometer disperses according to wavelength.according to wavelength.

With the energy calibration, background With the energy calibration, background counts can be eliminated.counts can be eliminated.

Thanks to:Thanks to:

Dr. Larry KnightDr. Larry Knight

Sterling CornabySterling Cornaby

Arturo ReyesArturo Reyes

Quan WangQuan Wang

Moxtek, Inc.Moxtek, Inc.