in one of its aspects , the present invention relates to a radiation source assembly comprising : ( i ) an elongate radiation transparent protective sleeve ; ( ii ) an elongate radiation source disposed in the protective sleeve ; ( iii ) a positioning element connected to a proximal portion of the elongate radiation source ; ( iv ) a connecting portion secured to a proximal portion of the positioning element ; and ( v ) a support element configured to receive the connecting portion to maintain a distal portion of the elongate radiation source in a cantilevered position with respect to a distal portion of the protective sleeve . preferred embodiments of this radiation source assembly may include any one or a combination of any two or more of any of the following features : the connecting portion may be in a movable relationship with respect to the proximal portion of the elongate radiation source ; the connecting portion may be in a pivoting relationship with respect to the proximal portion of the elongate radiation source ; the connecting portion may be in a rotatable relationship with respect to the proximal portion of the elongate radiation source ; the protective sleeve may comprise a proximal open end and a distal closed end ; the protective sleeve may comprise a pair of open ends ; a distal end of the protective sleeve may comprise a sealing element to substantially prevent ingress of fluid to the interior of the protective sleeve ; the protective sleeve may be constructed of quartz ; the elongate radiation source may comprise at least one centering ring to maintain the elongate radiation source and the elongate protective sleeve in a spaced ( e . g ., substantially coaxial ) relationship with one another ; the elongate radiation source may comprise a plurality of centering rings to maintain the elongate radiation source and the elongate protective sleeve in a spaced ( e . g ., substantially coaxial ) relationship with one another ; the positioning element may comprise at least one loom portion to secure an electrical connecter from the elongate radiation source along a portion of the length of the positioning element ; the positioning element may comprise at least one loom portion to secure a plurality of electrical connecters from the elongate radiation source along a portion of the length of the positioning element ; the positioning element may comprise a plurality of loom portions to secure an electrical connecter from the elongate radiation source along a portion of the length of the positioning element ; the positioning element may comprise a plurality of loom portions to secure a plurality of electrical connecters from the elongate radiation source along a portion of the length of the positioning element ; the elongate radiation source may comprise a reservoir portion containing a metal amalgam composition ; the reservoir portion may be disposed at the distal portion of the elongate radiation source ; the distal portion of the elongate radiation source may comprise an amalgam base portion secured thereto , the amalgam base portion receiving at least a portion of the reservoir portion ; the amalgam base portion may comprise at least one aperture configured to allow heat dissipation from the reservoir portion ; the amalgam base portion may further comprise a flap portion moveable between a first position in which the flap portion at least partially obstructs the aperture and a second position in which the aperture is unobstructed by the flap portion ; the amalgam base portion may further comprise a flap portion moveable between a first position in which the flap portion obstructs the aperture and a second position in which the aperture is unobstructed by the flap portion . the flap portion may comprises a first metal and a second metal ( different from the first metal ); the first metal and the second metal may thermally expand at different rates ; the metal amalgam composition may comprise a mercury amalgam composition . the positioning element and the support element may be configured to have a single correct engagement position ; the elongate radiation source may be an ultraviolet radiation source ; the elongate radiation source may be a low pressure ultraviolet radiation source ; the elongate radiation source is a low pressure , high output ultraviolet radiation source ; the elongate radiation source is medium pressure ultraviolet radiation source ; another aspect of the present invention relates to radiation source module comprising a support element for securing the module in a fluid treatment system and at least one radiation source assembly ( preferably a plurality ) as defined above . another aspect of the present invention relates to a fluid treatment system comprising a fluid treatment zone for receiving a flow of fluid and at least one radiation source module defined in the previous paragraph , wherein the at least one radiation source module is configured such that the radiation source assembly is disposed in the fluid treatment zone . preferred embodiments of this fluid treatment system may include any one or a combination of any two or more of any of the following features : the fluid treatment zone may be comprised in an open channel for receiving the flow of fluid ; the fluid treatment zone may be comprised in a closed channel for receiving the flow of fluid ; the at least one radiation source assembly may have a longitudinal axis disposed transverse to the direction of fluid flow through the fluid treatment zone ; the at least one radiation source assembly may have a longitudinal axis disposed orthogonal to the direction of fluid flow through the fluid treatment zone ; the at least one radiation source assembly may be disposed substantially vertically in the fluid treatment zone . in one of its aspects , the present invention relates to a radiation source assembly comprising : ( i ) an elongate radiation source ; ( ii ) a positioning element connected to a proximal portion of the elongate radiation source ; and ( iii ) a connecting portion secured to a proximal portion of the positioning element and configured to engage a support element to maintain a distal portion of the elongate radiation source in a cantilevered position . preferred embodiments of this radiation source assembly may include any one or a combination of any two or more of any of the following features : the connecting portion may be in a movable relationship with respect to the proximal portion of the elongate radiation source ; the connecting portion may be in a pivoting relationship with respect to the proximal portion of the elongate radiation source ; the connecting portion may be in a rotatable relationship with respect to the proximal portion of the elongate radiation source ; the elongate radiation source may comprise at least one centering ring to maintain the elongate radiation source and the elongate protective sleeve in a spaced ( e . g ., substantially coaxial ) relationship with one another ; the elongate radiation source may comprise a plurality of centering rings to maintain the elongate radiation source and the elongate protective sleeve in a spaced ( e . g ., substantially coaxial ) relationship with one another ; the positioning element may comprise at least one loom portion to secure an electrical connecter from the elongate radiation source along a portion of the length of the positioning element ; the positioning element may comprise at least one loom portion to secure a plurality of electrical connecters from the elongate radiation source along a portion of the length of the positioning element ; the positioning element may comprise a plurality of loom portions to secure an electrical connecter from the elongate radiation source along a portion of the length of the positioning element ; the positioning element may comprise a plurality of loom portions to secure a plurality of electrical connecters from the elongate radiation source along a portion of the length of the positioning element ; the elongate radiation source may comprise a reservoir portion containing a metal amalgam composition ; the reservoir portion may be disposed at the distal portion of the elongate radiation source ; the distal portion of the elongate radiation source may comprise an amalgam base portion secured thereto , the amalgam base portion receiving at least a portion of the reservoir portion ; the amalgam base portion may comprise at least one aperture configured to allow heat dissipation from the reservoir portion ; the amalgam base portion may further comprise a flap portion moveable between a first position in which the flap portion at least partially obstructs the aperture and a second position in which the aperture is unobstructed by the flap portion ; the amalgam base portion may further comprise a flap portion moveable between a first position in which the flap portion obstructs the aperture and a second position in which the aperture is unobstructed by the flap portion ; the flap portion may comprise a first metal and a second metal ; the first metal and the second metal may thermally expand at different rates ; the metal amalgam composition may comprise a mercury amalgam composition ; the positioning element may be configured to have a single correct engagement position with the support element ; the elongate radiation source may be an ultraviolet radiation source ; the elongate radiation source may be a low pressure ultraviolet radiation source ; the elongate radiation source may be a low pressure , high output ultraviolet radiation source ; the elongate radiation source may be a medium pressure ultraviolet radiation source ; and the angled base portion provides physical protection for the lamp and the reservoir portion . with reference to fig1 - 9 and 14 - 16 , there is illustrated a radiation source assembly 100 . radiation source assembly 100 comprises a radiation source 105 which may be an ultraviolet lamp or any other radiation emitting lamp . disposed on radiation source 105 are a pair of centering rings 110 . centering rings 110 serve to position radiation source 105 spaced ( e . g ., substantially coaxially ) with respect to a protective sleeve ( not shown for clarity ). centering rings 110 may be made from a radiation resistant material such as teflon ™. disposed at the distal portion of radiation source 105 is an amalgam reservoir 115 which contains a metal - containing amalgam composition ( e . g ., a mercury - containing amalgam composition ). also disposed in the distal portion of radiation source 105 is an amalgam end base 120 . amalgam end base 120 is configured to have an aperture 125 which receives a portion of amalgam reservoir 115 . as shown particularly in fig3 , dimension a generally represents the exposed region of amalgam reservoir 115 with respect to amalgam end base 120 . dimension a may be varied appropriately to expose sufficient portion of amalgam reservoir 115 to the surrounding environment optimizing heat dissipation from amalgam reservoir 115 and proper operation of radiation source 105 . emanating from amalgam end base 120 are a pair of electrical leads 130 . with reference to fig7 and 8 , a modified version of amalgam end base 120 is illustrated . in this modification , a flap portion 135 is pivotally attached to amalgam end base 120 . flap portion 135 is movable between a closed position ( fig7 ) and an open position ( fig8 ). in a preferred embodiment , flap portion 135 has a bi - metal construction . in this embodiment , flap portion 135 would consist of two different metals , preferably in a laminate construction . each of the two metals would have a different thermal expansion property allowing flap portion 135 to open or close depending on the temperature of the surrounding environment . thus , when it would be desirable to allow heat to dissipate from amalgam end base 120 , flap portion 135 would open allowing heat to exit from aperture 125 . once the appropriate temperature of amalgam reservoir 115 is reached , flap portion 135 would then move to the closed position ( fig7 ). with reference to fig1 and 10 , it will be seen that the proximal portion of radiation source 105 has a fixed thereto an end base element 140 . a positioning rod 145 is connected to a pair of ears 150 on end base element 140 by a pair of pin elements 155 that are integrally formed with positioning rod 145 . with particular reference to fig1 , it will be seen that end base element 140 comprises a series of apertures 160 through with electrical leads ( not shown for clarity ) from radiation source 105 may emanate . typically , there will be one or two electrical leads 130 emanating from a distal portion or radiation source 105 and one or two electrical leads 165 emanating from a proximal portion of radiation source 105 . the number of electrical leads is not particularly restricted and will be depend on the nature of radiation source 105 . as will be understood , the connection of positioning rod 145 to end base element 140 allows for pivoting of these two elements with respect to one another . this facilitates placement and removal of radiation source assembly 100 in a protective sleeve thereby reducing the risk of increasing a bending moment on radiation source 105 and / or the protective sleeve minimizing the risk that either of these elements will be broken during servicing of radiation source 105 . with reference to fig1 , there is illustrated a small modification of the embodiment illustrated in fig9 . specifically , in fig1 , the connection of positioning rod 145 to end base element 140 is accomplished by use of a pivot pin 170 which is independent of positioning rod 145 . specifically , pivot pin 170 traverses through ears 150 and an aperture ( not shown ) in distal portion 175 of positioning rod 145 . with reference to fig1 and 13 , there is illustrated a modified form of end base element 140 which utilizes a so - called ball joint connected to positioning rod 145 . thus , end base element 140 comprises a ball portion 142 which is received in a complementary shaped base 147 on positioning rod 145 . with reference to fig1 and 15 , it can be seen that positioning rod 145 comprises a pair of looms 170 , 175 . as illustrated , electrical leads 130 are fed through loom 170 while electrical leads 160 are fed through loom 175 . looms 170 , 175 may be configured and oriented with respect to one another , for example to keep the electrical leads out of the field of view of optical radiation sensor ( not shown ) if present in the system . a second pair of looms 170 a , 175 a are provided near the proximal portion of positioning rod 145 to receive electrical leads 130 and 160 , respectively . as shown , electrical leads 130 and 160 are received in an electrical connector 180 which is conventional . the use of a conventional connector 180 allows for illumination of the need to use expensive molded - type connectors , for example , as shown in the maarschalkerweerd patents discussed above . positioning rod 145 further comprises a radiation block 185 which has a slot 190 for receiving electrical leads 130 and 160 . radiation block 185 serves to block radiation emanating upward and posing a potential occupation health risk to operators of the fluid treatment system . the proximal portion of positioning rod 145 comprises a handle 195 in the form of a cross piece connection to positioning rod 145 . with reference to fig1 and 18 , there is illustrated a cartridge element 200 which is of similar construction to the radiation source cartridge described in illustrated in u . s . provisional patent application ser . no . 61 / 193 , 686 [ penhale et al .] filed dec . 16 , 2008 . cartridge element 200 illustrated in fig1 and 18 includes a pair of support elements 205 , 210 which receive handle 195 of positioning rod 145 . preferably , handle 195 and support elements 205 , 210 are indexed or keyed so that handle 195 is engaged with support elements 205 , 210 in a singular correct position . this facilitates ensuring that electrical leads 130 and 160 do not obscure any optical radiation sensors that may be used in the fluid treatment system . with further reference to fig1 , it can be seen that electrical connector 180 is connected to a complementary connector on cartridge element 200 ( the electrical connections are omitted from fig1 for clarity ). the connection of the protective sleeve ( not shown ) in which radiation source 105 is disposed to cartridge element 200 is conventional — see , for example , the teachings of u . s . provisional patent application ser . no . 61 / 193 , 686 [ penhale et al . ], filed dec . 16 , 2008 . when it is desired to service radiation source 105 , electrical connector 180 is disengaged and handle 195 is lifted from support elements 205 , 210 thereby lifting radiation source 105 out of the protective sleeve ( not shown ). as end base element 140 emanates from cartridge element 200 , the pivoting movement of positioning rod 145 with respect to radiation source 105 allows simpler withdrawal of radiation source 105 from the protective sleeve . this avoids conferring a bending moment to radiation source 105 and / or the protective sleeve ( not shown ), thereby obviating or mitigating breakage of these components . of particular note , the protective sleeve may be left in place while radiation source 105 is being serviced . with reference to fig1 , there is illustrated a radiation source module 250 comprising a number ( 6 are shown in the exemplary embodiment ) of radiation source assemblies 100 — in this case , a protective sleeve 102 is shown for each radiation source assembly 100 . the specific details for connection of cartridge element 200 to the other elements of radiation source module 250 and the incorporation of radiation source module 250 in a fluid treatment system may be found in u . s . provisional patent application ser . no . 61 / 193 , 686 [ penhale et al . ], filed dec . 16 , 2008 and u . s . provisional patent application ser . no . 61 / 202 , 576 [ penhale et al . ], filed mar . 13 , 2009 . while this invention has been described with reference to illustrative embodiments and examples , the description is not intended to be construed in a limiting sense . thus , various modifications of the illustrative embodiments , as well as other embodiments of the invention , will be apparent to persons skilled in the art upon reference to this description . it is therefore contemplated that the appended claims will cover any such modifications or embodiments . all publications , patents and patent applications referred to herein are incorporated by reference in their entirety to the same extent as if each individual publication , patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety .