Mini-X X-Ray Tube System for XRF – Amptek – X-Ray Detectors and Electronics

The Mini-X is the first of its kind; a self-contained, packaged, miniature X-ray tube system, which includes the X-ray tube, the power supply, the control electronics and the USB communication to the computer. It is designed to replace radioisotopes in X-ray fluorescence analysis applications.

It has been designed to simplify the XRF process by providing a grounded anode, variable current and voltage controlled via USB and ease of operation. It features a 50 kV/80 µA power supply, a silver (Ag) or gold (Au) transmission target, and a beryllium end window. It is designed for continuous operation in industrial environments.

To further simplify the use of Mini-X an AC adapter is provided to supply the 12 VDC needed to power the system. The only connections needed to operate the tube are a USB cable and AC adapter. A flashing red LED and a beeper warns the user when x-rays are present.

Features

50 kV/80 µA
Silver (Ag) or Gold (Au) Target
USB Controlled
Stable Output
Fast
Low Power
Small

Amptek Mini-XMini-X shown with X-123SDD

Figure 1a. Mini-X Silver (Ag) X-Ray Output Spectrum at 50 kV.

Figure 1b. Mini-X Gold (Au) X-ray Output spectrum at 50 kV.

The Mini-X is based on the Newton Scientific Inc. miniature X-ray source.

Specifications

Target Material	Silver (Ag) or Gold (Au)
Target Thickness	Ag = 0.75 µm (±0.1 µm) Au = 1.00 µm (±0.1 µm)
Tube voltage	10 to 50 kV
Tube current	5 µA min / 200 µA max See Figure 2 below
Approximate Dose Rate	Ag: 1 Sv/h (100 Rem/hr) @ 30 cm on axis, 50 kV and 80 µA Au: 2.2 Sv/h (220 Rem/hr) @ 30 cm on axis, 50 kV and 80 µA
Approximate Flux	Ag: 10⁶ counts per second/mm² on the axis at a distance of 30 cm (50 keV/1 µA) Au: 2.2 x 10⁶ counts per second/mm² on the axis at a distance of 30 cm (50 keV/1 µA)
Continuous Output Power	4 W max at 100% duty cycle See Figure 2 below
Window Material	Beryllium (Be); window at ground
Window Thickness	127 µm
Focal Spot Size	Approximately 2 mm
Output Cone Angle	120° (See figures 3 and 4 below)
Cooling	Air Cooled
High Voltage Stability	<0.1%
Leakage Radiation at 5 cm with safety plug installed	<5 µSv/h (0.5 mrem/h)
Power Consumption	9 W at 50 kV and 80 µA
Input Voltage	12 VDC (AC adapter included)
Control	USB, mini-USB connector (cable included)
Setting Time	Typical <1 s
Weight	360 grams
Humidity	30 to 90% noncondensing
Operating Temperature Range	-10 °C to +50 °C
Storage Temperature Range	-25 °C to +60 °C
Safety Controls and Indicators	1) External Hardware Interlock 2) Flashing LED 3) Beeper
Software	Mini-X Control software to control voltage and current. Mini-X API for custom programming applications.
Warranty	One year or 2000 hours, whichever comes first

Specifications, terms and pricing subject to change.

Figure 2. 4W Isopower curve.

Figure 3. Mini-X Angular Response, 120° cone.

Figure 4. Mini-X 120° cone.
NOTE: When using the 2 mm collimator, the X-ray cone is 5°.

Figure 5. Back panel connectors.

Figure 6. Mini-X software control panel.

Vacuum Application

The Mini-X can be configured with a standard conflat for vacuum applications.

Figure 7. Mini-X and X-123SDD with vacuum couplings.

Additional Information

Use of Mn secondary target to mimic ⁵⁵Fe source

How to chose the anode material for an X-Ray tube

Output Spectra

Figure 7. Mini-X Gold (Au) Output Spectrum at 10, 20, 30, 40, 50 kV.

Figure 8. Mini-X Silver (Ag) Output Spectrum at 10, 20, 30, 40, 50 kV.

Figure 9. Relative Output Spectra: Ag and Au Targets. Taken at a distance of 18 inches (45.7 cm),
with 2 mm diameter collimator on the Mini-X, a 1 mm diameter collimator on the detector, and 50 kV/1 µA.
Note that the Au tube gives more counts for the same current. This is because the bremsstrahlung increases for increasing Z.

Filters

Mini-X Silver (Ag) Output Spectra with Various Filters

Figure 10. Mini-X Ag Output Spectrum with 3 mil Cu Filter.	Figure 11. Mini-X Ag Output Spectrum with 2 mil Mo Filter.
Figure 12. Mini-X Ag Output Spectrum with 1 mil Ag Filter.	Figure 13. Mini-X Ag Output Spectrum with 1 mil W + 10 mil Al Filter.
Figure 14. Mini-X Ag Output Spectrum with 80 mil Al Filter.

Mini-X Gold (Au) Output Spectra with Various Filters

Figure 15. Mini-X Au Output Spectrum with 3 mil Cu Filter.	Figure 16. Mini-X Au Output Spectrum with 2 mil Mo Filter.
Figure 17. Mini-X Au Output Spectrum with 1 mil Ag Filter.	Figure 18. Mini-X Au Output Spectrum with 1 mil W + 10 mil Al Filter.
Figure 19. Mini-X Au Output Spectrum with 80 mil Al Filter.

The above spectra have not been normalized (i.e. not taken at the same current for the same time etc.). They have been provided only to show the shape of the spectrum and demonstrate how a filter can be used to obtain a beam specific to an application. Keep in mind that when any filter is used it reduces the flux coming out of the tube. An Al filter reduces the flux much less than a W or Ag filter. The higher the Z of the filter or the thicker the filter, the less flux will be available. It is therefore necessary to raise the current of the x-ray tube to compensate.

The above spectra were taken with the Amptek XR-100T-CdTe detector, a PX4 digital processor and power supply, and the silver (Ag) and gold (Au) versions of the Mini-X. In the spectra above there are notches observed at 26.7 and 31.8 keV. These are the Cd and Te K absorption edges. The XRS-FP software was used to correct the escape peaks generated in the detector. Please see application note ANCDTE1 for more information on the effects of the CdTe detector on the output spectrum.

The following filters are provided with the Mini-X:

Material	Thickness (µm/mils)	# Provided
Al	1016/40	5
Al	254/10	5
Cu	25.4/1	3
Mo	25.4/1	2
Ag	25.4/1	1
W	25.4/1	1

Why should I use a filter on the X-ray tube?

The primary beam filter, the filter on the X-ray tube, improves the signal to background ratio for the characteristic X-ray peaks one wants to measure. The tube produces X-rays over a wide range of energies, including many low energy brehmstrahlung X-rays and characteristic X-rays from the target. These scatter from the target, obscuring the peaks to be measured. The filter absorbs the lower energy X-rays, which do not excite the X-rays one wants to measure anyway, thus improving the signal to background ratio for the peaks of interest.
They can filter the characteristic lines of the tube’s target. For example, in figures 20 and 21 a filter is used which cleanly cuts low energy photons up to about 12-15 keV. This removes the gold (Au) L lines from the tube at 9.71 and 11.44 keV. Figure 15 above shows a Cu filter which cleans the low energy photons but also creates a clean region above 10 keV.

Figure 20. This figure shows the output spectrum of the Mini-X-Ag at 40 kV unfiltered, and filtered with 80 mils (2 mm) of aluminum (Al). In the unfiltered spectrum, a large fraction of brehmstrahlung counts are at low energy (between 5 and 15 keV), which are removed in the filtered spectrum.

Figure 21. Shows spectra measured from a lead target using the unfiltered and filtered tube. With no filter, the lead characteristic X-rays are superimposed on a large background of scattered X-rays. With a filter, the signal to background ratio is significantly improved. This will reduce the measurement uncertainty in these lines. Notice how the L-gamma line is much more visible in the filtered spectrum than in the un-filtered.

Filters on an X-Ray Tube Application Note in PDF

Collimator & Safety Plug

Collimator and Safety Plug

The Mini-X is provided with two collimators to facilitate its use in XRF applications. They consist of a brass collimator with aluminum (Al) inserts and a cover that screws into the Mini-X. The collimators have 1 and 2 mm diameter holes. A brass safety plug is also provided which, when installed, reduces the flux from an operating tube to less than 25 µSv/h (2.5 mrem/hr) at 5 cm away in accordance with requirement 5.2.2.2.2 of the NBS Handbook for Radiation Safety for X-Ray Diffraction and Fluorescence Analysis Equipment.

Figure 22. Mini-X collimator and safety plug.

Figure 23. Mini-X with safety plug installed.

Figure 24. Mini-X with collimator installed.

Figure 25. Screw-on Brass Cover Mechanical Dimensions.

Radiation Info

Caution

This device produces X-Rays when energized. To be operated only by qualified personnel.

Radiation Precautions

The Mini-X Is intended to generate x-ray radiation during normal operation. The Mini-X has been designed to focus radiation in the designated output direction, however radiation in other directions is possible and should be addressed with shielding and/or monitoring in the final application.

Radiation Levels

Radiation levels external to the X-ray tube housing with the brass safety plug ON do not exceed 25 µSv/h (2.5 mrem/h) measured 5 cm from the surface of the housing in accordance with Requirement 5.2.2.2.2 of the National Bureau of Standards (NBS) Handbook for Radiation Safety for X-Ray Diffraction and Fluorescence Analysis Equipment.

For more information please see the NBS Handbook.