X-ray source and transmission window

Abstract

In at least one embodiment an X-ray source includes an electron source configured to emit electrons, an acceleration set-up configured to accelerate the emitted electrons and a transmission window downwards of the acceleration set-up, the transmission window configured to let through X-rays generated by the accelerated electrons, wherein the transmission window incudes a carbon carrier, and wherein the carbon carrier includes sp2-hybridized carbon.

Claims

1. An X-ray source comprising: an electron source configured to emit electrons; an acceleration set-up configured to accelerate the emitted electrons; and a transmission window downwards of the acceleration set-up, the transmission window configured to let through X-rays generated by the accelerated electrons, wherein the transmission window comprises: a carbon carrier, a target layer carried by the carbon carrier, the target layer being located on a side of the carbon carrier facing the electron source, and a bonding layer located between the target layer and the carbon carrier, the bonding layer being of at least one inorganic material and comprising at least one of an oxide or a nitride, and wherein the carbon carrier comprises sp2-hybridized carbon.

2. The X-ray source of claim 1, wherein a mass proportion of carbon of the carbon carrier is at least 95%.

3. The X-ray source of claim 2, wherein the carbon carrier is of pyrolytic carbon.

4. The X-ray source of claim 1, wherein the target layer is of at least one metal and is thinner than the carbon carrier.

5. The X-ray source of claim 1, wherein a thickness of the target layer is at most 5 m and a thickness of the carbon carrier is between 0.02 mm and 2 mm, inclusive.

6. The X-ray source of claim 1, wherein the target layer is of at least one of W, Rh, Ag, Au, Mo or Pd.

7. The X-ray source of claim 1, wherein a diameter of the carbon carrier is between 4 mm and 4 cm, inclusive, and wherein the X-ray source is free of any auxiliary structures supporting a central part of the transmission window, seen in top view, where a focal spot of the accelerated electrons is located.

8. The X-ray source of claim 1, wherein a focal spot of the accelerated electrons at the transmission window has a diameter of at least 0.1 mm and of at most 4 mm, and wherein the X-ray source is configured for X-ray fluorescence spectroscopy.

9. The X-ray source of claim 1, wherein a focal spot of the accelerated electrons at the transmission window has a diameter of at least 2 mm and of at most 20 mm, and wherein the X-ray source is configured for ion mobility spectroscopy.

10. The X-ray source of claim 1, wherein the X-ray source is an evacuated X-ray source between the electron source and the transmission window so that a pressure within the X-ray source is below 10.sup.3 mbar at 300 K, and wherein a side of the transmission window remote from the electron source is configured to be at a pressure of 1 bar at 300 K.

11. The X-ray source of claim 1, wherein an electric conductivity of the carbon carrier is at least 0.1 kS/m.

12. The X-ray source of claim 1, wherein the electric conductivities of the carbon carrier in different directions differ from one another by at least a factor of 2.

13. The X-ray source of claim 1, wherein the carbon carrier is optically non-transparent in a visible spectral range and has an absorption coefficient of at least 104 cm.sup.1 at a wavelength of 600 nm.

14. The X-ray source of claim 1, further comprising: a window frame, wherein the window frame carries the transmission window and is attached on the acceleration set-up.

15. A transmission window comprising: a carbon carrier comprising sp2-hybridized carbon; a target layer carried by the carbon carrier, the target layer being located on a side of the carbon carrier facing an electron source; and a bonding layer located between the target layer and the carbon carrier, the bonding layer being of at least one inorganic material and comprising at least one of an oxide or a nitride, wherein the target layer is of at least one metal and is thinner than the carbon carrier, and wherein the transmission window is configured for an X ray source.

16. An X-ray source comprising: an electron source configured to emit electrons; an acceleration set-up configured to accelerate the emitted electrons; and a transmission window downwards of the acceleration set-up, the transmission window configured to let through X-rays generated by the accelerated electrons, wherein the transmission window comprises a carbon carrier, wherein the carbon carrier consists of pyrolytic carbon so that the carbon of the carbon carrier is predominantly sp2-hybridized, wherein the carbon of the carbon carrier, in a deconvoluted Raman spectrum of the carbon carrier, has both a visible 2D-peak in a range between 2650 cm.sup.1 and 2750 cm.sup.1, inclusive and a visible sp3-peak in a range between 1250 cm.sup.1 and 1350 cm.sup.1, inclusive, and wherein the visible 2D-peak, when measured with laser excitation at 532 nm, has, by at least a factor of two, a larger area content than the visible sp3-peak.

17. The X-ray source of claim 16, wherein a thickness of the carbon carrier is between 0.02 mm and 2 mm, inclusive.

18. The X-ray source of claim 16, wherein a diameter of the carbon carrier is between 4 mm and 4 cm, inclusive, and wherein the X-ray source is free of any auxiliary structures supporting a central part of the transmission window, seen in top view, where a focal spot of the accelerated electrons is located.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An X-ray source and a transmission window described herein are explained in greater detail below by way of exemplary embodiments with reference to the drawings. Elements which are the same in the individual figures are indicated with the same reference numerals. The relationships between the elements are not shown to scale, however, but rather individual elements may be shown exaggeratedly large to assist in understanding.

(2) FIGS. 1 and 2 are schematic sectional views of exemplary embodiments of X-ray sources described herein;

(3) FIGS. 3 and 4 are schematic sectional views of exemplary embodiments of transmission windows for X-ray sources described herein; and

(4) FIG. 5 is a schematic representation of the G-peak and the D-peak of exemplary embodiments of transmission windows for X-ray sources described herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(5) FIG. 1 illustrates an exemplary embodiment of an X-ray source 1. The X-ray source 1 comprises a base plate 53 through which a pin 55 is led. The pin 55 carries an electron source 2 which is, for example, a filament that may be heated. The base plate 53 can be housed in a socket 54. Optionally, at the socket 54 there is an outer tube 52. It is possible that the socket 54 and the first electrode 31 are of one single piece.

(6) The electron source 2 is configured to emit electrons 22. Downstream of the electron source 2, there is a first electrode 31 of an acceleration set-up 3. The first electrode 31 may be in one piece with the socket 54. Further, downstream of the first electrode 31 there is a second electrode 32 of the acceleration set-up 3. The acceleration set-up 3 is configured to accelerate the emitted electrons 22 along a direction away from the electron source 2, for example. Thus, the electrons 22 run through the second electrode 32 so that the latter can be a transmission anode.

(7) A relative position between the electrodes 31, 32 is defined by an inner tube 51. Thus, the inner tube 51 may hold the second electrode 32.

(8) For example, within the inner tube 51 into which the first electrode 31 and the pin 55 carrying the electron source 2 protrude, there is an evacuated area 56 maintaining a pressure in the sub-mbar range. The outer tube 52 may reach beyond the first electrode 31, starting from the socket 54, but may not reach up to the second electrode 31 that also protrudes into the inner tube 51 but from an opposite direction. The second electrode 32 may cover end faces of the inner tube 51 remote from the base plate 53.

(9) Optionally, within an end portion of the second electrode 32 remote from the first electrode 31 there can be a window frame 6. The window frame 6 is configured to fix a transmission window 4 at an end of the inner tube 51. The window frame 6 may be a single piece, for example, like a half of a cylinder. Within the window frame 6, the transmission window 4 is arranged.

(10) For example, the transmission window 4 is glued, sintered, brazed, soldered or welded onto the window frame 6. As an option, hard-soldering, brazing, soft-soldering eutectic soldering or glass soldering may be used as well as laser welding, electron beam welding, friction welding, ultrasonic welding, electric resistance welding or the like. It is possible that at an edge part the window frame 6 and/or the transmission window 4 carries a ring-like connection layer, not shown, for providing adhesion between these two components. Further, there can be a geometric structuring, not shown, at least one of the transmission window 4 and the window frame 6 for mounting the transmission window 4.

(11) By means of the acceleration set-up 3, the electrons 22 are accelerated and optionally also focused onto the transmission window 4. Not shown, for focusing the electrons 22 there can be electron optics, realized, for example, by the shape of the electrodes 31, 32, like the shape of the second electrode 32. Upon impact of the electrons 22 onto the transmission window 4, X-rays are generated that are emitted by the X-ray source 1 through the transmission window 4. Thus, the X-ray source 1 may also be referred to as an X-ray tube.

(12) The transmission window 4 is not based on beryllium, but is bases as its mechanically supporting component on sp2-hybridized carbon as explained in more detail below in connection with FIGS. 3 and 4.

(13) For example, for x-ray fluorescence spectroscopy, the X-ray source 1 is configured for an operating power between 0.1 W and 15 W. Additionally, in ion mobility spectroscopy, operating powers down to 1 mW can be used. For example, an electron focal spot of the electrons 22 at the transmission window 4 has a diameter between 0.25 mm and 4 mm inclusive in case of serving for XRF, or may have a diameter between 5 mm and 20 mm inclusive in case of serving for IMS.

(14) In FIG. 1, the X-ray source 1 is of linear design, that is, for example, the electrons 22 and the generated X-rays X are led along a common straight axis. Otherwise, it is also possible that the X-ray source 1 is of angled design so that the electrons 22 and/or the X-rays X may be led along a kinked axis having, for example, a 90 angle. Accordingly, not only transmission anodes but also solid anodes with an additional separate transmission window can be used. The same applies for all other examples of the X-ray source 1.

(15) In the example of the X-ray source 1 of FIG. 2, the window frame 6 comprises an outer part 61 and an inner part 62. The transmission window 4 is placed between these two parts 61, 62 so that the edge part of the transmission window 4 is fixed in the window frame 6 and can adhesively be connected to both parts 61, 62. As in all other examples, it is possible that the transmission window 4 is of plane-parallel fashion.

(16) Otherwise, the same as to FIG. 1 may also apply to FIG. 2, and vice versa.

(17) In FIGS. 3 and 4, examples of transmission windows 4 are illustrated. In each case, the transmission windows 4 comprise a carbon carrier 41 which is based on sp2-hybridized carbon and which mechanically carries the transmission windows 4. For example, a thickness of the carbon carrier 41 is between 0.02 mm and 0.1 mm inclusive. For example, a diameter of the carbon carrier 41 is between 5 mm and 9 mm inclusive. Optionally, the carbon carrier 41 is of pyrolytic carbon.

(18) Optionally, the carbon carrier 41 carries a target layer 42. The target layer 42 is configured to generate the X-rays upon impact of the electrons 22. For example, the target layer 42 is of one of the following metals: W, Rh, Ag, Au, Mo, Pd. For example, a thickness of the target layer 42 is between 0.05 m and 5 m inclusive. The target layer 42 may be thinner than the carbon carrier 41 and may not be self-supporting so that the carbon carrier 41 is needed to mechanically support the target layer 42.

(19) As shown in FIG. 3, the target layer 42 is directly applied onto the carbon carrier 41, for example, by sputtering or evaporating. Contrary to that, according to FIG. 4 there is a bonding layer 43 between the carbon carrier 41 and the target layer 42. The bonding layer 43 can be thinner than the target layer 42. For example, the bonding layer 43 is of an oxide, a nitride or of Si.

(20) All the components 41, 42, 43 can be of single-layer fashion. However, as indicated in FIG. 4 by the dashed lines, one or a plurality of the carbon carrier 41, the target layer 42 and the optional bonding layer 43 can be of multi-layer fashion so that there is a plurality of sub-layers in the respective component. These sub-layers may differ from one another in material composition and/or in material configuration, like orientation or crystal lattice, and also in geometric properties, like thickness, lateral extend and/or shape. The same applies for all other examples.

(21) Otherwise, the same as to FIGS. 1 and 2 may also apply to FIGS. 3 and 4, and vice versa.

(22) In FIG. 5, a Raman shift S vs. a Raman Intensity I of a Raman spectrum of the carbon carrier 41 is schematically illustrated in the region of the 2D-peak and of the defect-peak, that is around 2700 cm-1 and around 1300 cm-1, respectively. The peaks are fitted by Gaussian curves so that an area content A2D of the 2D-peak and an area content Adef of the defect-peak are revealed. These area contents A2D, Adef are a measure of the proportions of sp2-hybridized carbon and sp3-hybridized carbon. As can be seen from the example in FIG. 5, the area content A2D is about a factor of three larger than the area content Adef, for example. Thus, the carbon carrier 41 is predominantly of sp2-hybridized carbon. This applies, for example, for laser excitation of the carbon carrier at 532 nm.

(23) Concerning Raman spectroscopy of sp2-hybridized carbon, reference is also made to document Isaac Childres et al., Raman spectroscopy of graphene and related materials, New developments in photon and materials research, 1, from 2013, as well as to Joe Hodkiewicz, Characterizing Carbon Materials with Raman Spectroscopy, Thermo Fisher Scientific, Madison, WI, USA, Application Note: 51901; concerning the Raman spectroscopy, the disclosure content of these documents is incorporated by reference.

(24) The invention described here is not restricted by the description on the basis of the exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which includes in particular any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.