Moxtek

Moxi™ X-ray source is calibrated to within ±250 V over all settings between 5 to 50 kV. This impressive accuracy and precision is achieved spectroscopically, by measuring an X-ray spectrum's bremsstrahlung edge and storing correction high voltage offset information on each source.

	One optimization desired by manufactures of X-ray fluorescent (XRF) instruments is X-ray sources that are spectroscopically identical. A spectroscopically identical X-ray source allows one to switch out an X-ray source in an instrument with no other changes to the instrument, for example, with minimal or no recalibration of the instrument. This benefit is desired by handheld XRF manufacturers, which reduces XRF calibration effort and service time for XRF instruments. Each Moxi™ X-ray source is calibrated to within ±250 V over all settings between 5 to 50 kV. This voltage accuracy is tight enough to allow for XRF equivalence for several XRF applications.

	In order to calibrate an X-ray source, two basic requirements are needed:

		A meaningful and accurate way to measure the high voltage.

		A way to store the high-voltage calibration information on each X-ray source, offsetting source-to-source differences due to variance in the source's electrical components.

	The X-ray source's high voltage is measured by collecting an X-ray spectrum from the tube's anode. The source is pointed directly at an energy-dispersive detector, with a pinhole in-between to limit the intensity from the X-ray source. The spectrum's bremsstrahlung edge is fit with a proprietary algorithm, giving the value of the bremsstrahlung edge in keV. This measurement provides the "spectroscopic" voltage in keV, while the electronic monitors on the X-ray source give an electronically measured voltage in kV. The difference between the two gives a correction factor, which can be used to tighten the accuracy and precision between these two values. This test is repeated over several tube voltage settings between 5 and 50 kV.

	The variance in the electronic components in aggregate is the major driving factor for the high-voltage inaccuracy of any particular X-ray source. The electronic components have a partially nonlinear relationship with high voltage. The Moxi™ X-ray source has an onboard memory which can hold a correction factor to correct for the nonlinear relationship.


	Figure 1: This graphic shows the offset between the tube's set voltage and bremsstrahlung edge over seven setting's precalibration, on over 100 separate X-ray sources. Precalibration, the high voltage is typically offset by 800 V, and can vary by up to ±1000 V (@35 kV).

	Comparing Figures 1 and 2 shows the accuracy and precision of the high voltage on the X-ray sources is drastically increased by the high-voltage calibrating procedure. These graphs are intentionally at the same scale to easily show the improvements.


	Figure 2: This graphic shows the offset between the tube's set voltage and bremsstrahlung edge over seven settings post-calibration, on over 100 separate x-ray sources. Post-calibration, the high voltage is typically offset by 100 V, and can vary by up to ±250 V (@35 kV).

	Moxi™ X-ray sources are an "XRF equivalent" X-ray source for XRF instrument manufacturers. The key aspect for achieving this source's spectral equivalence is the high-voltage calibration of the source. Each digital X-ray source is calibrated to within ±250 V over all settings between 4 to 50 kV. The high accuracy and precision is achieved spectroscopically by measuring the bremsstrahlung edge and storing high-voltage offset information on each source. This benefit is very much desired by handheld XRF manufacturers and reduces XRF calibration effort and service time for XRF instruments. This quantification has practical backing; it is working as intended in next-generation XRF handheld instruments sold today.


	452 West 1260 North, Orem, UT 84057
	tel. (801) 225-0930, fax (801) 221-1121
	Website: 

Articles

High Voltage Accuracy and Precision on Small Compact X-ray Sources

 maximum voltage was increased from 60 kV to 70 kV while maintaining the same size profile. This article highlights the advantages of 70 kV excitation of cadmium, an element of interest for the Restriction of Hazardous Substances Directive (RoHS), at parts per million (ppm) levels. 

	The MAGPRO 12 W miniature source is small and low power, which is an advantage for a number of applications. Our 12 W source has several anode materials available: a tungsten anode for either XRF or in X-ray imaging, as well as Rh, Ag, Cr, Cu, and Mo. The entire X-ray source (tube plus high voltage power supply) weights about 700 g (25.0 oz) and can be controlled by your choice of USB, digital, or analog control, and has an interlock connection for X-ray safety (Figure 1). The increase of high voltage from 60 kV to 70 kV for the MAGPRO was primarily motivated for use in handheld imaging applications. This increase in voltage also shows important benefits for spectroscopy applications as well. This article highlights the advantages of the 70 kV excitation for low levels of cadmium.


	Figure 1: Image of the 12 W X-ray source.

	Experimental Conditions and Results for XRF Detection of Cadmium

	Cadmium detection is of interest because it is a toxic metal that needs to be detected for RoHS/WEEE compliance. Detection of cadmium at low concentrations is particularly difficult because cadmium's 23.2 keV K

 emission line is much higher than that of other toxic elements of interest. An X-ray source with a higher voltage helps to increase the X-ray signal from cadmium. For this experiment, we used a typical XRF setup where the sample is placed at 45° to the tube and detector. The X-ray spot on the sample was 4×6 mm, achieved with a collimator and a tube-to-sample distance of 25 mm. A 200 µm molybdenum foil was placed between the tube and sample to suppress the Compton background scattering roughly between 20 to 30 keV; thereby suppressing the background under the cadmium K

 peak. Figure 2 shows four spectra taken from a polyvinyl chloride sample with 10 ppm of Cd, with the tube set at 40, 50, 60, and 70 kV. A 42 mm

 SDD collected the data with a 15 mm sample-to-detector distance over 180 s live time, with the input count rate ranging from 20 to 100 kcps. It is evident that increasing the voltage also increases the cadmium signal. In this set-up, 10 ppm of cadmium is detectable in a reasonable 3–5 min time frame.


	Figure 2: The cadmium line at about 23.2 keV gets larger as the voltage on the tube is increased. This is an advantage for cadmium detection in XRF systems looking for toxic metal at low concentrations.

	The MAGPRO source is meant for use in small benchtop systems where small size is valued. It has increased its high voltage range from 60 kV to 70 kV, which is an advantage in detecting higher atomic number elements such as the hazardous substance cadmium.


	452 West 1260 North, Orem, UT 84057
	tel. (800) 758-3110
	email: 

Miniature 70 kV, 12W X-ray Source

’s maximum voltage was increased from 60 kV to 70 kV while maintaining the same size profile. This article highlights the advantages of 70 kV excitation of cadmium, an element of interest for Restriction of Hazardous Substances Directive (RoHS), at parts per million (ppm) levels.

 12 W miniature source is small and low power, which is an advantage for a number of applications. Our 12 W source has several anode materials available; a tungsten anode for either XRF or in X-ray imaging, as well as Rh, Ag, Cr, Cu, and Mo. The entire X-ray source (tube plus high voltage power supply) weights about 700 g (25.0 oz) and can be controlled by your choice of USB, digital, or analog control and has an interlock connection for X-ray safety (Figure 1). The increase of high voltage from 60 kV to 70 kV for the 

 was primarily motivated for use in handheld imaging applications. This increase in voltage also shows important benefits for spectroscopy applications as well. This article highlights the advantages of the 70 kV excitation for low levels of cadmium.

	Cadmium detection is of interest because it is a toxic metal that needs to be detected under RoHS/WEEE compliance. Detection of cadmium at low levels is particularly difficult to detect at lower concentrations because cadmium’s 23.2 keV K

 emission line is much higher than other toxic elements of interest. An X-ray source with a higher voltage helps to increase the X-ray signal from cadmium. For this experiment, we used a typical XRF setup where the sample is placed at 45° to the tube and detector. The X-ray spot on the sample was 4x6 mm, achieved with a collimator and a tube-to-sample distance of 25 mm. A 200 μm molybdenum foil was placed between the tube and sample to suppress the Compton background scattering roughly between 20 to 30 keV; thereby suppressing the background under the cadmium K

 source is meant for use in small benchtop systems where small size is valued. It has increased its high voltage range from 60 kV to 70 kV, which is an advantage in detecting higher atomic number elements such as the hazardous substance cadmium.

Recently, the compact MAGPRO’s maximum voltage was increased from 60 kV to 70 kV while maintaining the same size profile. This article highlights the advantages of 70 kV excitation of cadmium, an element of interest for Restriction of Hazardous Substances Directive (RoHS), at parts per million (ppm) levels. 

Moxtek's MAGPRO miniature X-ray source is capable of up to 60 kV 200 µA and down to 4 kV and 1000 µA, and limited to an output power of 12 watts. The 12 W source is meant for use in small bench top systems where small size is valued.

	The 12 W miniature source has a higher voltage and a much higher emission current than our present miniature X-ray sources, which is an advantage for a number of applications. The initial release of the 12 W source, our MXDPP-50 electronics comes in two versions: The tungsten anode version, which can be used in either XRF or in X-ray imaging, and the Rh anode version, primarily meant for light element XRF detection (Figure 1). The entire X-ray source (tube plus high voltage power supply) weighs about 700 g (25.0 oz) and can be controlled by your choice of USB, digital, or analog control. It also has an interlock connection for X-ray safety.

	We will show the advantage of the rhodium anode source running at 4 kV 1000 µA for XRF of cement powders.

Experimental Conditions and Results for XRF Detection of Cement Powers

	Concentrations of sulfur (sulfate), silicon (silicon dioxide), and aluminum (aluminum oxide) are important for both identifying and controlling different blends of cement powder. XRF can be used to measure cement powder elemental concentrations. XRF for the desired "light" elements, with emission lines under about 4 keV is challenging because the characteristic X-rays are absorbed by air, thereby attenuating the signal from the sample. For this experiment, we used a typical XRF setup where the sample is placed at 45° to the tube, and 135° to the detector, and no filters on the 12 W X-ray source. For light element XRF, a rhodium anode is often used because it has L emission lines between 2.7 and 3.0 keV, which are used to excite elements with emission lines below 2.5 keV. For this test the 12 W X-ray source was set to the minimum of 4 kV, which is helpful in eliminating the calcium XRF signal from the cement. The calcium signal is unwanted in this application because it will overwhelm the detection of the other elements of interest. A high emission current X-ray source, such as 1000 µA from the 12 W source, is very helpful in increasing the signal.

	Figure 2 shows an XRF spectrum from a Portland cement sample with the 12 W source running at 1000 µA and 200 µA on a rhodium anode tube. The signal level is increased by a bit over fivefold for these light elements, which can be a huge advantage in any application which detection of light elements is needed.

	The new 12 W source is meant for use in small benchtop systems where small size is valued. It has as increased range up to 60 kV at high voltage and increased current to 1000 µA at low voltages; both of which are an advantage in XRF and imaging applications.


	452 West 1260 North, Orem, UT 84057
	tel. (800) 758-3110, email: 

Miniature 60 kV, 1000 μA 12 W X-ray Source

Moxtek's MAGPRO miniature X-ray source is capable of up to 60 kV 200 µA and down to 4 kV and 1000 µA, and limited to an output power of 12 watts. The 12 W source is meant for use in small bench top systems where small size is valued. 

	The 12 W miniature source has a higher voltage and a much higher emission current than our present miniature X-ray sources, which is an advantage for a number of applications. The initial release of the 12 W source, our MXDPP-50 electronics comes in two versions: the tungsten anode version, which can be used in either XRF or in X-ray imaging, and the Rh anode version, primarily meant for light element XRF detection (Figure 1). The entire X-ray source (tube plus high voltage power supply) weighs about 700 g (25.0 oz) and can be controlled by your choice of USB, digital, or analog control. It also has an interlock connection for X-ray safety.


	Figure 2: Running at 1000 µA, the 12 W source produces much more signal from the desired elements in the cement powder than running at 200 µA.

Moxtek's MAGPRO miniature X-ray source is capable of up to 60 kV 200 μA and down to 4 kV and 1000 μA, and limited to an output power of 12 Watts. The 12 W source is meant for use in small bench top systems where small size is valued.

	We will show the advantage of the rhodium anode source running at 4 kV 1000 μA for XRF of cement powders.


	Figure 1: Image of the 12W X-ray source.

	Concentrations of sulfur (sulfate), silicon (silicon dioxide), and aluminum (aluminum oxide) are important for both identifying and controlling different blends of cement powder. XRF can be used to measure cement powder elemental concentrations. XRF for the desired "light" elements, with emission lines under about 4 keV is challenging because the characteristic X-rays are absorbed by air, thereby attenuating the signal from the sample. For this experiment, we used a typical XRF setup where the sample is placed at 45° to the tube, and 135° to the detector, and no filters on the 12 W X-ray source. For light element XRF, a rhodium anode is often used because it has L emission lines between 2.7 and 3.0 keV, which are used to excite elements with emission lines below 2.5 keV. For this test the 12 W X-ray source was set to the minimum of 4 kV, which is helpful in eliminating the calcium XRF signal from the cement. The calcium signal is unwanted in this application because it will overwhelm the detection of the other elements of interest. A high emission current X-ray source, such as 1000 μA from the 12 W source, is very helpful in increasing the signal.

	Figure 2 shows an XRF spectrum from a Portland cement sample with the 12 W source running at 1000 μA and 200 μA on a rhodium anode tube. The signal level is increased by a bit over fivefold for these light elements, which can be a huge advantage in any application which detection of light elements is needed.


	Figure 2: Running at 1000 μA, the 12 W source produces much more signal from the desired elements in the cement powder than running at 200 μA.

	The new 12 W source is meant for use in small bench top systems where small size is valued. It has as increased range up to 60 kV at high voltage and increased current to 1000 μA at low voltages; both of which are an advantage in XRF and imaging applications.

The 12 W miniature source has a higher voltage and a much higher emission current than our present miniature X-ray sources, which is an advantage for a number of applications.

Moxtek’s MAGPRO miniature X-ray source  is capable of up to 60 kV 200 μA and down to 4 kV and 1000 μA, and limited to an output power of 12 W. The 12 W source is meant for use in small benchtop systems where small size is valued. 

	The 12 W miniature source has a higher voltage and a much higher emission current then our present miniature X-ray sources, which is an advantage for a number of applications. The initial release of the 12 W source, our MXDPP-50 electronics, come in two versions: the tungsten anode version which can be used in either XRF or in X-ray imaging, and the Rh anode version primarily meant for light element XRF detection (Figure 1). The entire X-ray source (tube plus high voltage power supply) weights about 700 g (25.0 oz) and can be controlled by your choice of USB, digital, or analog control. It also has an interlock connection for X-ray safety.

	
	We will show the advantage of the rhodium anode source running at 4 kV 1000 μA for XRF of cement powders.
	
	

Experimental Conditions and Results for XRF Detection of Cement Powers


	Concentrations of sulfur (sulfate), silicon (silicon dioxide), and aluminum (aluminum oxide) are important for both identifying and controlling different blends of cement powder. XRF can be used to measure cement powder elemental concentrations. XRF for the desired “light” elements, with emission lines under about 4 keV is challenging because the characteristic X-rays are absorbed by air, thereby attenuating the signal from the sample. For this experiment, we used a typical XRF setup where the sample is placed at 45° to the tube, and 135° to the detector, and no filters on the 12 W X-ray source.

	For light element XRF, a rhodium anode is often used because it has L emission lines between 2.7 and 3.0 keV, which are used to excite elements with emission lines below 2.5 keV. For this test, the 12 W X-ray source was set to the minimum of 4 kV, which is helpful in eliminating the calcium XRF signal from the cement. The calcium signal is unwanted in this application because it will overwhelm the detection of the other elements of interest. A high emission current X-ray source, such as 1000 μA from the 12 W source, is very helpful in increasing the signal.


	The new 12 W source is meant for use in small benchtop systems where small size is valued. It has as increased range up to 60 kV at high voltage and increased current to 1000 μA at low voltages; both of which are an advantage in XRF and imaging applications.

	Moxtek, Inc.
	452 West 1260 North, Orem, UT 84057
	tel. (800) 758-3110
	Website: 

Moxtek's ULTRA-LITE X-ray source is a very small self contained X-ray source (X-ray tube and high voltage power supply) for use in portable X-ray applications, such as the handheld X-ray fluorescence (XRF) spectrometers. This note demonstrates that this X-ray source has a stable and repeatable X-ray flux output over time, which is vital for the precision of the calibrated XRF measurements.

	Moxtek's ULTRA-LITE source has a high voltage range of 5–50 kV, an emission current range of 5–200 μA, and comes with an assortment of anode materials including tungsten and silver. The maximum output power on the X-ray tube is 4 Watts. With the X-ray tube running at full power, the source draws approximately 9 Watts. At full power the ULTRA-LITE X-ray source will run for over 3 h on a typical 12 V 2.4 mA-h batteries. It is very small in size, 25 mm × 46 mm × 148 mm, and weighs only 250 g, making it perfect for handheld and portable instruments.

	Two of the key metrics of the X-ray source for XRF applications, and many other applications as well, are X-ray flux and high voltage repeatability. Repeatability means that every time the source is turned on at a particular high voltage and current setting, the high voltage and the X-ray flux stays as constant over time.

	In development of the ULTRA-LITE X-ray source we performed a number of characterization tests on multiple units. One key test is a flux repeatability test, in which the source is turned on and off numerous times. For each on/off cycle we capture an image of the focal spot, record the X-ray energy spectra coming off the tube, the energy spectra coming off a secondary XRF target, as well as input and monitor voltages and currents over several hours to days at room temperature.

	From these tests we have seen that the ULTRA-LITE source has a very stable and repeatable X-ray flux and high voltage. The flux was measured directly from the source with an X-ray PIN diode, which measures the flux by counting X-ray photon events. Figure 1 shows the X-ray photon counts collected from an ULTRA-LITE source over 3.5 days of time. The PIN diode also records the energy spectra of the incoming photons, which contains the bremsstrahlung edge from the source. By tracking the bremsstrahlung edge the high voltage stability of the source was tracked over time.


	Figure 1: This shows the flux repeatability from one ULTRA-LITE source set at the maximum voltage of 50 kV and 80 μA, the full 4 Watts. The flux is stable to under 0.10% RSD (std/mean) over 3.5 days. The source was turned on for 120 s, then off for 10 s, and cycled on and off 2400 times for this test.

	The high voltage of the source does not vary more than ±100 V at 50 (0.2%) kV by measuring the bremsstrahlung edge, and the flux is stable and repeatable within 0.5% RSD or less over the time frame of days. The repeatability of this source will be an asset to any handheld or portable application where excellent flux repeatability is needed, such as XRF.


	452 West 1260 North, Orem, UT 84057
	tel. (800) 758-3110
	Email: 

Moxtek's ULTRA-LITE X-ray source is a very small self contained X-ray source (X-ray tube and high voltage power supply) for use in portable X-ray applications, such as the handheld X-ray fluorescence (XRF) spectrometers.

Moxtek’s ULTRA-LITE X-ray Source

A broadband polarizing beamsplitter (PBS) cube was developed using embedded Moxtek

 grid polarizer technology. The Moxtek ICE Cube

 PBS provides superior performance in broadband, low f/# spectroscopic applications where both high efficiency and excellent contrast are required.

	Cube beamsplitters are found in a variety of spectroscopic applications where matching path lengths, reduced ghosting, and limited beam shift are important. Polarizing beamsplitter cubes are found in phase-shifting laser interferometers, polarization sensitive optical coherence tomography, and polarization sensitive white light interferometry. PBS cubes are often used for applications that require compact designs and reduced mechanical vibration. Typically MacNeille cubes have been used for many PBS applications, but for low f/#'s (large cone angles), the color balance and the contrast ratio between passing and blocking state transmittance have been less than ideal. On the contrary, wire grid polarizers (WGP) are known for excellent broadband performance in low f/# applications. By incorporating a WGP along the hypotenuse of a cube beamsplitter, the Moxtek ICE Cube provides a superior PBS in low f/# applications.

	As depicted in Figure 1a, a white light LED source was collimated and passed through an iris followed by a high contrast pre-analyzer to select an input polarization state. The beam was then focused into Moxtek and MacNeille Cube beamsplitters and the blocking state transmittance (

) was minimized on a screen. The blocking state reflectance and transmittance were then imaged using a camera, as was the passing state transmittance and reflectance (after rotating pre-analyzers by 90°). In both cases the aperture was varied to change the f/#, and the images were taken at about f/1.2 cone angle.


	Figure 1: Low f/# performance comparison between polarizing beam splitter cubes. Measurement schematic (a) and results (b-c) showing blocking state transmittance (T

) for MacNeille Cube (b) and Moxtek ICE Cube (c).

	As shown in Figure 1, the ICE Cube (Figure 1c) has improved color balance and a reduced leakage in the blocking state (

) when compared to the MacNeille cube (Figure 1b). Both cubes were also characterized at variable angles with well collimated light from the UV to the SWIR. The Moxtek ICE Cube outperformed the MacNeille cube, accommodating angular deviations from normal incidence of ±20° in the azimuthal direction and ±10° in the polar (elevation) direction with minimal performance variation.

	The Moxtek ICE Cube beamsplitter with embedded nano-wire grid polarizer provides superior broadband performance over a wide angular aperture, with none of the dramatic color shifts and angular performance variations evident in MacNeille cube beamsplitters. While MacNeille cube designs can typically only tolerate a narrow angular aperture before performance deteriorates, the Moxtek ICE Cube accommodates a much larger angular field of view, allowing the optical designer to maintain system performance in broadband spectroscopic applications with demanding form factors.

The Moxtek ICE Cube Polarizing Beamsplitter

A broadband polarizing beamsplitter (PBS) cube was developed using embedded Moxtek® Nanowire® grid polarizer technology. The Moxtek ICE Cube™ PBS provides superior performance in broadband, low f/# spectroscopic applications where both high efficiency and excellent contrast are required.

Cube beamsplitters are found in a variety of spectroscopic applications where matching path lengths, reduced ghosting, and limited beam shift are important. Polarizing beamsplitter cubes are found in phase-shifting laser interferometers, polarization sensitive optical coherence tomography, and polarization sensitive white light interferometry. PBS cubes are often used for applications that require compact designs and reduced mechanical vibration. Typically MacNeille cubes have been used for many PBS applications, but for low f/#'s (large cone angles), the color balance and the contrast ratio between passing and blocking state transmittance have been less than ideal. On the contrary, wire grid polarizers (WGP) are known for excellent broadband performance in low f/# applications. By incorporating a WGP along the hypotenuse of a cube beamsplitter, the Moxtek ICE Cube provides a superior PBS in low f/# applications. 

As depicted in Figure 1a, a white light LED source was collimated and passed through an iris followed by a high contrast pre-analyzer to select an input polarization state. The beam was then focused into Moxtek and MacNeille Cube beamsplitters and the blocking state transmittance (

) was minimized on a screen. The blocking state reflectance and transmittance were then imaged using a camera, as was the passing state transmittance and reflectance (after rotating pre-analyzers by 90°). In both cases the aperture was varied to change the f/#, and the images were taken at about f/1.2 cone angle. 

 Figure 1: Low f/# performance comparison between polarizing beam splitter cubes. Measurement schematic (a) and results (bâc) showing blocking state transmittance (Ts) and reflectance (Rs) for MacNeille Cube (b) and Moxtek ICE Cube (c).

As shown in Figure 1, the ICE Cube (Figure 1c) has improved color balance and a reduced leakage in the blocking state (

) when compared to the MacNeille cube (Figure 1b). Both cubes were also characterized at variable angles with well collimated light from the UV to the SWIR. The Moxtek ICE Cube outperformed the MacNeille cube, accommodating angular deviations from normal incidence of ±20° in the azimuthal direction and ±10° in the polar (elevation) direction with minimal performance variation. 			

The Moxtek ICE Cube beamsplitter with embedded nanowire grid polarizer provides superior broadband performance over a wide angular aperture, with none of the dramatic color shifts and angular performance variations evident in MacNeille cube beamsplitters. While MacNeille cube designs can typically only tolerate a narrow angular aperture before performance deteriorates, the Moxtek ICE Cube accommodates a much larger angular field of view, allowing the optical designer to maintain system performance in broadband spectroscopic applications with demanding form factors. 

A broadband polarizing beamsplitter (PBS) cube was developed using embedded Moxtek Nanowire grid polarizer technology.