Abstract:
An x-ray system with a tubehead that can be easily configured in the field for gas or liquid cooling of the x-ray tube anode so a user need not stock or carry more than one kind of tubehead to accommodate different cooling needs.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 60/547,713 filed Feb. 25, 2004, the entire contents of which are incorporated by reference herein. 
    
    
     FIELD 
     This patent specification is in the field of industrial x-ray systems that typically are used for non-destructive testing (NDT), for example of vehicles, pipes, and other objects. 
     BACKGROUND AND SUMMARY 
     Industrial x-ray systems have long been used in a number of fields, including NDT. Typically, they comprise several units: a tubehead that includes an x-ray tube, a cooling arrangement to remove heat from the x-ray tube, a source of electrical power, and a control unit. The x-ray tube typically includes a target that generates x-rays when bombarded with an electron beam accelerated between a cathode and an anode. The anode can be the target itself, or another material interposed between the anode and the cathode can be the target. (“Anode” here includes both an anode serving as the target and the combination of separate target material and the anode.) The anode gets heated in the process of generating x-rays, and typically needs to be cooled for practical operation. 
     One common type of cooling is gas cooling. Typically, a finned heat sink is thermally coupled with the anode and is cooled with gas such as air blown through the fins with a high capacity muffin fan. The gas cooling unit is affixed at the anode end of the tubehead. Another common type of cooling is liquid cooling. A fitting with an internal conduit is thermally coupled with the anode and liquid from an outside source is circulated through the fitting. In some cases, air cooling is preferable, as it does not require an outside source of liquid and a pump and thus fewer components need to be moved and set up. In other cases, liquid cooling is preferable, for example when operating the x-ray systems in volatile gas environments where there is a danger from possible sparking at the fan motor. In such environments, the outside source of liquid coolant and the pump can be spaced from the tubehead such that they are outside the volatile gas environment. 
     LORAD of Danbury Conn., a division of Hologic, Inc. of Bedford, Mass., has been selling x-ray systems for a number of years in this country with gas cooling as well as x-ray systems with liquid cooling. A number of other companies also have offered system with one type of cooling of the other type. For example, LORAD currently offers gas cooled tubeheads and also liquid cooled tubeheads under the commercial designation LORAD LPX series. However, to the inventors&#39; knowledge, x-ray tubeheads that can be conveniently configured in the field to use either type of cooling have not been commercially available. 
     The inventors believe that it would be desirable to provide a tubehead that can be easily configured in the field to be either liquid cooled or air cooled. For example, when it is not known ahead of time in what environment a tubehead will have to operate, currently a user may need to stock, or take on a trip, both a gas cooled x-ray system and a liquid cooling system. The inventors believe that cost savings and convenience can be achieved by providing a single tubehead that can operate with either type of cooling and is easily configured in the field to change from one type of cooling to another. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  illustrates a prior art gas cooled x-ray system, and 
         FIG. 2  illustrates a portion of the system. 
         FIG. 3  illustrates a prior art liquid cooled x-ray system, and 
         FIG. 4  illustrates a portion of the system. 
         FIG. 5  illustrates a new x-ray tubehead that can be easily configured in the field for gas or liquid cooling, and 
         FIG. 6  illustrates a sectional view thereof. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a prior art air cooled x-ray system comprising a tubehead  100  and a heat exchanger  102 . A control unit  104  communicates with tubehead  100  and gas heat exchanger  102  via cables  106  and  108  and is powered via cable  110  from a source such as an electric generator or a the power grid. 
       FIG. 2  illustrates a part of the interior of tubehead  100 , shrouded by a housing  202  around an x-ray tube  202  and an internal power supply  204  that generates the high voltage needed to operate the x-ray tube. A muffin fan inside gas heat exchanger is driven by an internal electric motor to blow gas (e.g. air) through a finned heat sink that also in inside heat exchanger  102 . 
       FIG. 3  illustrates a prior art system that uses liquid cooling rather than gas cooling. A liquid cooled tubehead  300  connects through twin hose  302  to a cooler unit  304  that houses a supply of cooling liquid and a pump to circulates the liquid through a conduit thermally coupled to the anode of the x-ray tube in tubehead  300 . A control unit  104  that can be the same as in  FIG. 1  (or specially adapted for liquid cooling) connects to  300  via a cable  106  and with cooler unit  304  via cable  108 , and to power via cable  110 . The cables can be the same as the cables in  FIG. 1  or can be specially adapted to liquid cooling. 
       FIG. 4  illustrates liquid cooled tubehead  300  in partial section, showing a housing  400  around x-ray tube that can be the same as in  FIG. 2  or can be specially adapted for liquid cooling. An anode (no visible in this FIG.) extends to the left in  FIG. 4  and a fitting  402 , made of a material such as brass, is secured in thermal contact with the anode to cool it with a liquid entering and exiting an internal conduit via tubes  404  and a manifold  406  with connectors  408  that couple to twin hose  302  and thus with cooler unit  304  ( FIG. 3 ). In operation, cooler unit  304  pumps liquid coolant though the internal conduit in fitting  402  to cool the anode. 
       FIG. 5  illustrates schematically a new arrangement in which tubehead  500  is easily field-configured for either gas or liquid cooling. Tubehead  500  cart use the same x-ray tube as in  FIGS. 2 and 4 , but has attached thereto a different heat exchanger  502  that selectively provides either gas cooling or liquid cooling. The x-ray tube has an anode  504  that extends to the left in  FIG. 5  and typically is made mainly of a metal such as copper (but includes a target of a different metal, such as tungsten). A finned heat sink  506  fits tightly over and is in good thermal contact with anode  504 . A fitting  508  that has an internal conduit for cooling liquid also is fits tightly over and is in good thermal contact with anode  504 . Inlet and outlet conduits  510  circulate cooling liquid through the internal conduit of fitting  508 , via manifold  512  that can connect through connectors  514  to twin hose  302  ( FIG. 3 ) and thus to cooler unit  304 . Heat sink  506  can be similar to the heat sink used in the gas cooled prior art heat exchangers offered by Lorad, except that it allows for conduits  510  to pass to fitting  508  and for also placing fitting  508  over anode  504 . Fitting  508  can he similar to fitting  402  ( FIG. 4 ) used in the prior art liquid cooled tubehead offered by Lorad, except for a different connection to conduits  510  (as illustrated in  FIG. 5 ) and for an allowance for placing heat sink  506  on the same anode  504 . To the left of fitting  508 , the new unit uses a muffin fan  516  driven by an internal electric motor that can be same or similar to the fan and motor used in the prior art Lorad gas heat exchanger  102  ( FIGS. 1 and 2 ). To simplify the drawing, details such inlets and outlets for air, cable connections, and details of how tubes  510  connect to manifold  512 , are not shows in FIG,  5 . 
       FIG. 6  illustrates a section of  FIG. 6  taken along lines  6 — 6 , and shows inlet and outlet tubes  510  (labeled  510   a  and  510   b ) connected to fitting  508  to circulate cooling liquid through its internal conduit, and also show several of the fins of heat sink  506 . Only two longer and two shorter fins are shown, although in fact the fins radiate symmetrically around the entire circumference of the heat sink. The two central fins are shorter to allow for passage of tubes  510 . 
     In operation, if the user elects to use gas heating, fan  516  is turned on and blows cooling gas (air) at finned heat sink  506  to cool the heat sink and thereby anode  504 . No liquid need circulate though fitting  508 , and there is no need for twin hose  302  to be connected to connectors  514  or for cooler unit  304  to be available. If the user elects to use liquid cooling, the motor inside fan  516  remains turned off. Twin hose  302  connect manifold  512  to cooler unit  304 , and the pump inside unit  304  circulates cooling liquid through the internal conduit of fitting  508 . Thus, a user need not change from one tubehead to another in order to change from one type of cooling to another, need not stock two types of tubeheads, and can easily configure the system in the field for one type of cooling to another. 
     Although there should be no need for it, as each type of cooling should be sufficient for normal operation, the new arrangement of  FIG. 5  can be used with both types of cooling simultaneously. 
     Thus, a portable industrial x-ray system is provided that that is conveniently field-configurable for gas or liquid cooling. The system comprises: (1) an elongated tubehead that at least partly encloses an x-ray tube having an anode emitting x-rays when energized; (2) a heat exchanger secured to the tubehead and comprising (a) a heat sink thermally coupled to the anode for heat exchange therewith and a fan which, when operating, supplies cooling gas to the heat radiating material to assist in cooling the anode and target, and (b) a fitting thermally coupled to the anode for heat exchange therewith and having an internal conduit in fluid flow communication with couplers for connection though a hose to an outside source of circulating liquid coolant; whereby a user configures the system for gas cooling only by operating the fan to cool the heat sink and thus the anode, or for liquid cooling only by keeping the fan off but operating the outside source to circulate liquid coolant through the internal conduit of the fitting and thereby cool the anode, or by operating both in gas cooled and liquid cooled modes. The improvement also includes the method of operating the same tubehead and heat exchanger either in only one of a gas heating mode and a liquid cooling mode, or in both modes.