Abstract
A method for protecting an X-ray source including: a liquid jet generator configured to form a liquid jet moving along a flow axis; an electron source configured to provide an electron beam interacting with the liquid jet to generate X-ray radiation; the method including: generating the liquid jet: monitoring a quality measure indicating a performance of the liquid jet; identifying, based on the quality measure, a malperformance of the liquid jet; and if said malperformance is identified, causing the X-ray source to enter a safe mode for protecting the X ray source. Further, to corresponding devices.
Claims
1. A method for protecting an X-ray source comprising: a liquid jet generator configured to form a liquid jet moving along a flow axis; an electron source configured to provide an electron beam interacting with the liquid jet to generate X-ray radiation; a monitoring arrangement configured to monitor, directly or indirectly, a quality measure indicating a performance of the liquid jet; wherein the quality measure comprises at least one of a shape of the liquid jet; a width of the liquid jet; a speed of the liquid jet along the flow axis; a pressure within the liquid jet generator; and a movement of the liquid jet perpendicular to the flow axis; a processing unit operatively connected to the liquid jet generator, the electron source, and the monitoring arrangement; wherein the method comprises, by means of the processing unit: generating the liquid jet; monitoring the quality measure; identifying a malperformance of the liquid jet if the quality measure exceeds a quality measure threshold; and if said malperformance is identified, causing the X-ray source to enter a safe mode for protecting the X-ray source.
2. The method according to claim 1, further comprising establishing a nominal trend for the quality measure, and wherein the step of identifying the malperformance comprises detecting a deviation in the quality measure from the nominal trend.
3. The method according to claim 2, wherein the malperformance is identified if the deviation exceeds two standard deviations of the nominal trend.
4. The method according to claim 1, wherein entering the safe mode comprises at least one of: reducing a speed of the liquid jet along the flow axis; reducing a power output of the electron source; terminating generation of the liquid jet; shielding at least part of the X-ray source from contamination created by the malperformance of the liquid jet; and changing a filter of the liquid jet generator.
5. An X-ray source comprising: a liquid jet generator configured to form a liquid jet moving along a flow axis; an electron source configured to provide an electron beam interacting with the liquid jet to generate X-ray radiation; a monitoring arrangement configured to monitor, directly or indirectly, a quality measure indicating a performance of the liquid jet; said quality measure comprising at least one of a shape of the liquid jet; a width of the liquid jet; a speed of the liquid jet along the flow axis; a pressure within the liquid jet generator; and a movement of the liquid jet perpendicular to the flow axis; and a processing unit configured to identify a malperformance of the liquid jet if the quality measure exceeds a quality measure threshold; wherein the X-ray source is configured to enter a safe mode for protecting the X-ray source if said malperformance is identified.
6. The X-ray source according to claim 5, wherein the monitoring arrangement comprises an acoustic sensor configured to detect acoustic emissions created by the liquid jet, and/or the generation of the liquid jet.
7. The X-ray source according to claim 5, wherein the monitoring arrangement comprises an accelerometer configured to detect vibrations created by the liquid jet, and/or by the generation of the liquid jet.
8. The X-ray source according to claim 5, wherein the monitoring arrangement comprises an optic sensor.
9. The X-ray source according to claim 5, wherein the monitoring arrangement comprises an electron detector configured to receive at least part of the electron beam passing the liquid jet.
10. The X-ray source according to claim 5, wherein the monitoring arrangement comprises an X-ray detector configured to detect X-rays generated by an interaction between the electron beam and the liquid jet.
11. The X-ray source according to claim 5, wherein the monitoring arrangement comprises an inductive coil arrangement comprising a transmitter coil and a receiver coil configured to utilize the liquid jet as an inductive coupling between the transmitter coil and the receiver coil, wherein the transmitter coil is configured to pass a current and wherein the receiver coil is configured to receive an induced current.
12. The X-ray source according to claim 5, further comprising a shield arrangement, and wherein the processing unit is configured to, when the X-ray source is in the safe mode, position the shield arrangement such that at least part of the X-ray source is shielded from contamination created by the malperformance of the liquid jet.
13. The X-ray source according to claim 5, further comprising a filter exchange tool, and wherein the processing unit is configured to, when the X-ray source is in the safe mode, operate the filter exchange tool in order to change a filter of the liquid jet generator.
14. The X-ray source according to claim 5, wherein the X-ray source is configured to enter a safe mode by at least one of: reducing a speed of the liquid jet along the flow axis; reducing a power output of the electron source; terminating generation of the liquid jet; shielding at least part of the X-ray source from contamination created by the malperformance of the liquid jet; and changing a filter of the liquid jet generator.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The above, as well as additional objects, features and advantages of the present inventive concept, will be better understood through the following illustrative and non-limiting detailed description of different embodiments of the present inventive concept, with reference to the appended drawings, wherein:
(2) FIG. 1 schematically illustrates an X-ray source in a perspective view;
(3) FIGS. 2a-2b schematically illustrate an example of an inductive coil arrangement in a side view;
(4) FIG. 3a-3c schematically illustrate an example of an inductive coil arrangement in a transverse cross-sectional view;
(5) FIGS. 4a-4c schematically illustrate an example of a shield arrangement in a side view;
(6) FIG. 5 is a flow chart diagram of a method for protecting an X-ray source.
(7) The figures are not necessarily to scale, and generally only show parts that are necessary in order to elucidate the inventive concept, wherein other parts may be omitted or merely suggested;
(8) FIGS. 6a-6b schematically illustrate a filter and a filter exchange tool.
DETAILED DESCRIPTION
(9) An X-ray source 100 according to the inventive concept will now be described with reference to FIG. 1.
(10) As indicated in FIG. 1, a low pressure chamber, or vacuum chamber, 102 may be defined by an enclosure 104 and an X-ray transparent window 106 which separates the low pressure chamber 102 from the ambient atmosphere. The X-ray source 100 comprises a liquid jet generator 108 configured to form a liquid jet 110 moving along a flow axis F. The liquid jet generator 110 may comprise a nozzle through which liquid, such as e.g. liquid metal may be ejected to form the liquid jet 110 propagating towards and through an interaction region 112. The liquid jet 110 propagates through the interaction region 112, towards a collecting arrangement 113 arranged below the liquid jet generator 108 with respect to the flow direction. The X-ray source 100 further comprises an electron source 114 configured to provide an electron beam 116 directed towards the interaction region 112. The electron source 114 may comprise a cathode for the generation of the electron beam 116. In the interaction region 112, the electron beam 116 interacts with the liquid jet 110 to generate X-ray radiation 118, which is transmitted out of the X-ray source 100 via the X-ray transparent window 106. The X-ray radiation 118 is here directed out of the X-ray source 100 substantially perpendicular to the direction of the electron beam 116.
(11) The liquid forming the liquid jet is collected by the collecting arrangement 113, and is subsequently recirculated by a pump 120 via a recirculating path 122 to the liquid jet generator 108, where the liquid may be reused to continuously generate the liquid jet 110.
(12) A monitoring arrangement 124 is here illustrated as part of the X-ray source 100. It should be noted that the illustration is merely a schematic representation of the inventive concept, and other possible locations of the monitoring arrangement 124 are possible within the scope of the inventive concept. The monitoring arrangement 124 is configured to monitor a quality measure indicating a performance of the liquid jet 110. Further, it is to be understood that the monitoring arrangement may comprise several individual components, such as e.g. at least one of an acoustic sensor, an accelerometer, an optic sensor, an electron detector, an x-ray detector, and an inductive coil arrangement. Such individual components are for the sake of clarity not illustrated in FIG. 1.
(13) A processing unit 126 is here also illustrated as part of the X-ray source 100. Similarly to the monitoring arrangement, the processing unit 126 is here arbitrarily placed in the low pressure chamber 102, and the person skilled in the art appreciates that other possible arrangements of the processing unit 126 are possible within the scope of the inventive concept.
(14) Still referring to FIG. 1, the X-ray source 100 here comprises an electron detector 128 configured to receive at least part of the electron beam 116 passing the liquid jet 110. The electron detector 128 is here arranged behind the interaction region 112 as seen from a viewpoint of the electron source 114. In case the liquid jet 110 moves or changes shape, at least part of the electron beam 116 may pass the liquid jet 110 and interact with the electron detector 128. Thus, the electron detector 128 may monitor a quality measure indicating a performance of the liquid jet 110. It is to be understood that the shape of the electron detector 128 is here merely schematically illustrated, and that other shapes of the electron detector 128 may be possible within the scope of the inventive concept.
(15) Still referring to FIG. 1, the X-ray source may comprise a shield arrangement 130. The shield arrangement 130 is here arranged in conjunction to the X-ray transparent window 106. However, the shield arrangement 130 may also be arranged in conjunction to e.g. the liquid jet 110, the electron source 114, and/or the electron detector 128, as described earlier in the present disclosure. The shield arrangement 130 may be configured to slide and/or move such that the X-ray transparent window 106, and/or other parts of the X-ray source, is shielded from contamination when the X-ray source is in the safe mode.
(16) Referring now to FIGS. 2a-2b, an inductive coil arrangement 232 is illustrated. The inductive coil arrangement 232 comprises a transmitter coil 234 and a receiver coil 236 configured to utilize the liquid jet 210, ejected from a nozzle 238 of a liquid jet generator 208, as an inductive coupling between the transmitter coil 234 and the receiver coil 236. The transmitter coil 234 and receiver coil 236 are here displaced along the flow axis F with respect to each other, with the transmitter coil 234 being arranged upstream of the receiver coil 236. However, the location of the transmitter coil 234 and receiver coil 236 may be interchanged while maintaining the function of the inductive coil arrangement 232. Further, it may also be possible to arrange the transmitter coil 234 and/or the receiver coil 236 such that the liquid jet is enclosed by the coils of the transmitter coil 234 and/or the receiver coil 236.
(17) A current may be passed through the transmitter coil 234, e.g. by means of a current generator such as a DC-generator (not shown). The liquid jet 210 may then act as an inductive coupling, thus inducing a current in the receiver coil 236. The current induced in the receiver coil 236 may be seen as a signal associated with a quality measure of the liquid jet 210. It may also be possible to define a signal associated with a quality measure of the liquid jet 210 as a difference and/or ratio between the current induced in the receiver coil 236, and a current passed through the transmitter coil 234. As can be seen in FIG. 2a, the liquid jet 210 has a substantially uniform shape along the flow axis, which may give rise to a first signal in the receiver coil 236. In FIG. 2b, a portion 242 of the liquid jet 210 has a larger transverse cross section compared to the liquid jet shown in FIG. 2a. Such an enlargement of the transverse cross section of the liquid jet 210 may be seen as a malperformance of the liquid jet 210, and may be caused by a variety of factors pertaining to e.g. the nozzle 238, the liquid jet generator 208, and/or the liquid jet 210. As the liquid jet 210 propagates along the flow axis F, the portion 242 having a deviant transverse cross section passes the transmitter coil 234 and the receiver coil 236, giving rise to a signal in the receiver coil 236, the signal may be utilized in order to determine a quality measure of the liquid jet 210. In the illustrated example, the quality measure may be associated with a shape and/or size of the liquid jet 210.
(18) A possible arrangement of an inductive coil arrangement will now be described with reference to FIGS. 3a-3c.
(19) Referring first to FIG. 3a, an inductive coil arrangement 332 is illustrated in a transverse cross-sectional view. The inductive coil arrangement 332 comprises a first transmitter coil 344 and a first receiver coil 346 which together form a first pair of coils. The first transmitter coil 344 and the first receiver coil 346 are arranged along one and the same axis, here the x-axis, in the transverse plane on opposite sides of the liquid jet 310. Hereby, the first pair of coils may be capable of detecting a movement of the liquid jet 310 having a vector component along the x-axis. More specifically, a current may be passed through the first transmitter coil 344, and the liquid jet 310 may act as an inductive coupling between the first transmitter coil 344 and the first receiver coil 346, thus inducing a current in the first receiver coil 346. The relative position of the liquid jet 310, and/or the shape of the liquid jet 310 and/or the cross-sectional size of the liquid jet 310, may cause a change of the current induced in the first receiver coil 346.
(20) Still referring to FIG. 3a, the inductive coil arrangement 332 may further comprise a second transmitter coil 348 and a second receiver coil 350 which together form a second pair of coils. The second transmitter coil 348 and the second receiver coil 350 arranged along one and the same axis, here the y-axis, in the transverse plane on opposite sides of the liquid jet 310. It may be noted that the second pair of coils are arranged along an axis being substantially perpendicular to the axis along which the first pair of coils are arranged. Hereby, the second pair of coils may be capable of detecting a movement of the liquid jet 310 having a vector component along the y-axis. More specifically, a current may be passed through the second transmitter coil 348, and the liquid jet 310 may act as an inductive coupling between the second transmitter coil 348 and the second receiver coil 350, thus inducing a current in the second receiver coil 348. The relative position of the liquid jet 310, and/or the shape of the liquid jet 310 and/or the cross-sectional size of the liquid jet 310, may cause a change of the current induced in the second receiver coil 350.
(21) The two pair of coils may together form an inductive coil arrangement capable of detecting a movement, and/or change of shape and/or change of size of the liquid jet 310.
(22) Referring now to FIG. 3b, the liquid jet 310 has moved relative the initial position of the liquid jet as illustrated in FIG. 3a. Here, the liquid jet 310 has moved in a direction having a vector component along both the x-axis and the y-axis. Consequently, the movement may be detected via the first pair of coils comprising the first transmitter coil 344 and the first receiver coil 346, as well as via the second pair of coils comprising the second transmitter coil 348 and the second receiver coil 350.
(23) Referring now to FIG. 3c, the liquid jet 310 has a different cross-sectional shape and size relative its cross-sectional shape and size as illustrated in FIG. 3a. The change of cross-sectional shape and size may be detected via the first pair of coils comprising the first transmitter coil 344 and the first receiver coil 346, as well as via the second pair of coils comprising the second transmitter coil 348 and the second receiver coil 350.
(24) With reference to FIGS. 4a-4c, a shield arrangement will now be described.
(25) Referring first to FIG. 4a, a liquid jet 410 is illustrated during normal operating conditions and performance of an X-ray source. The liquid jet 410 propagates along a flow axis F through an interaction region 412. An electron beam 416, generated by an electron source (not shown), is directed towards the interaction region 412, where the electron beam 416 interacts with the liquid target 410 to generate X-ray radiation.
(26) Referring now to FIG. 4b, a malperformance of the liquid jet 410 has been identified, and the X-ray source has been caused to enter a safe mode. A shield arrangement 452b has been positioned such that it may capture at least part of any contamination caused by the generation of the liquid jet 410. The shield arrangement 452b may be a tube as illustrated, having a diameter being greater than a diameter of the liquid jet 410. The diameter of the tube is preferably chosen to allow movement and enlargement of the liquid jet 410 without allowing contact between the tube and the liquid jet 410. An inner wall of the shield arrangement may comprise a phobic surface thus decreasing the ability for the material in the liquid jet to wet on the inner wall. In the illustrated arrangement, the electron source is preferably caused to cease generation of the electron beam. Consequently, X-ray radiation is no longer generated. The shield arrangement 452b may stay deployed until the malperformance of the liquid jet 410 has been corrected.
(27) Referring now to FIG. 4c, a malperformance of the liquid jet 410 has been identified, and the X-ray source has been caused to enter a safe mode. A shield arrangement 452c has been positioned such that it may capture at least part of any contamination caused by the generation of the liquid jet 410. The shield arrangement 452c may be a tube as illustrated, having a diameter being greater than a diameter of the liquid jet 410. The shield arrangement 452c comprises an opening 454 allowing the electron beam 416 to interact with the liquid jet 410 in the interaction region 412 in order to generate X-ray radiation 418. Thus, the X-ray source may continue to operate, i.e. generate X-ray radiation, while being in the safe mode.
(28) The shield arrangement may be stored upstream of the nozzle and/or downstream of the collecting arrangement when the X-ray source is not in the safe mode. Upon entering the safe mode, the shield arrangement may be moved into position by sliding the shield arrangement along the flow axis F.
(29) The shield arrangements disclosed in conjunction with FIGS. 4b-4c are illustrated as tubes. However, it may also be possible to utilize a shield arrangement comprising one or several screens or plates. The one or several screens or plates may be concave in order to form a tube enclosing the liquid jet. Such a shield arrangement may be stored in the low pressure chamber of the X-ray source, and upon entering the safe mode, the one or several screens or plates may be moved into position to shield at least part of the X-ray source from contamination caused by the generation of the liquid jet. An advantage with such an arrangement is that the one or several screens or plates may be moved into position in a direction being substantially perpendicular to the flow axis F.
(30) A method for protecting an X-ray source will now be described with reference to FIG. 5. For clarity and simplicity, the method will be described in terms of ‘steps’. It is emphasized that steps are not necessarily processes that are delimited in time or separate from each other, and more than one ‘step’ may be performed at the same time in a parallel fashion.
(31) The X-ray source comprises a liquid jet generator configured to form a liquid jet moving along a flow axis; and an electron source configured to provide an electron beam interacting with the liquid jet to generate X-ray radiation. In step 556, a liquid jet is generated. In step 558, a quality measure indicating a performance of the liquid jet is monitored. In step 560, a malperformance of the liquid jet is identified based on the quality measure. In step 562 the X-ray source is caused to enter a safe mode for protecting the X-ray source, if said malperformance is identified.
(32) Referring now to FIG. 6a, a liquid jet generator 608 is schematically illustrated in a process flow diagram. Liquid metal here pass a filter 610 arranged in conjunction with a nozzle 638. The filter 610 may be configured to remove particulate contaminants from the liquid metal, such that particulate contaminants are removed before the liquid metal reach the nozzle 638. Hence, the filter 610 is arranged upstream of the nozzle 638. A filter exchange tool 612 may be arranged in conjunction with the filter 610. The filter exchange tool 612 may be operated in order to, automatically, change the filter 610 of the liquid jet generator 608.
(33) Referring now to FIG. 6b, another example of a liquid jet generator 608 is schematically illustrated in a process flow diagram. Liquid metal may here be redirected into a filter by-pass path 640 via a three-way valve 630. A filter 645 configured to remove particulate contaminants from the liquid metal is arranged in the filter by-pass path 640. During normal operation the three-way valve 630 directs liquid metal pumped from a pump 620 towards the filter 610 and nozzle 638. However, when entering a safe mode, or as a part of maintenece procedures, the valve directs the liquid metal into the filter by-pass path 640 where it flows through filter 645 back to an inlet port of pump 620. Liquid metal may thus pass the filter 645 several times before being re-directed to the nozzle 638 via three-way valve 630. In this way an excess of particulate matter that might have formed e.g. during an episode of increased pressure within the vacuum chamber may be removed from the liquid metal without risk of clogging the filter 610 or the nozzle 638. A filter exchange tool (not shown) may be operated in order to, automatically, change the filter 610 and/or the filter 645 of the liquid jet generator 608.
(34) The person skilled in the art by no means is limited to the example embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. In particular, X-ray sources and systems comprising more than one liquid jet or more than one electron beam are conceivable within the scope of the present inventive concept. Furthermore, X-ray sources of the type described herein may advantageously be combined with X-ray optics and/or detectors tailored to specific applications exemplified by but not limited to medical diagnosis, non-destructive testing, lithography, crystal analysis, microscopy, materials science, microscopy surface physics, protein structure determination by X-ray diffraction, X-ray photo spectroscopy (XPS), critical dimension small angle X-ray scattering (CD-SAXS), and X-ray fluorescence (XRF). Additionally, variation to the disclosed examples can be understood and effected by the skilled person in practising the claimed invention, from a study of the drawings, the disclosure, and the appended claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
LIST OF REFERENCE SIGNS
(35) 100 X-ray source 102 Low pressure chamber 104 Enclosure 106 X-ray transparent window 108 Liquid jet generator 110 Liquid jet 112 Interaction region 114 Electron source 116 Electron beam 118 X-ray radiation 120 Pump 122 Recirculating path 124 Monitoring arrangement 126 Processing unit 128 Electron detector 130 Shield arrangement 208 Liquid jet generator 210 Liquid jet 232 Inductive coil arrangement 234 Transmitter coil 236 Receiver coil 238 Nozzle 332 Inductive coil arrangement 344 First transmitter coil 346 First receiving coil 348 Second transmitter coil 350 Second receiver coil 410 Liquid jet 412 Interaction region 416 Electron beam 418 X-ray radiation 452b Shield arrangement 452c Shield arrangement 454 Opening 556 Step of generating liquid jet 558 Step of monitoring quality measure 560 Step of identifying malperformance 562 Step of entering safe mode 608 Liquid jet generator 610 Filter 612 Filter exchange tool 620 Pump 630 Three-way valve 638 Nozzle 640 Filter by-pass path 645 Filter
