WO1999067656A1 - Scintillation head - Google Patents

Scintillation head Download PDF

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Publication number
WO1999067656A1
WO1999067656A1 PCT/GB1999/001941 GB9901941W WO9967656A1 WO 1999067656 A1 WO1999067656 A1 WO 1999067656A1 GB 9901941 W GB9901941 W GB 9901941W WO 9967656 A1 WO9967656 A1 WO 9967656A1
Authority
WO
WIPO (PCT)
Prior art keywords
channel
scintillator
block
face
base
Prior art date
Application number
PCT/GB1999/001941
Other languages
French (fr)
Inventor
Alexander Serge Obolensky Ranicar
James Miller Gillies
Original Assignee
Imperial College Innovations Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Imperial College Innovations Ltd. filed Critical Imperial College Innovations Ltd.
Publication of WO1999067656A1 publication Critical patent/WO1999067656A1/en

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01TMEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/003Scintillation (flow) cells

Definitions

  • the present invention relates to the detection of radioactivity in fluids, and in particular relates to the design of scintillators suitable for use with a radiation detection system.
  • the scintillator design is applicable to capillary-based fluid delivery systems and the invention has particular application, though not exclusively so, to capillary electrophoresis, flow injection analysis and capillary liquid chromatography, incorporating the analysis of fluid based compounds labelled with positron-emitting radio-nuclides.
  • the radio-nuclides are of the ⁇ - or ⁇ -emitting variety.
  • a scintillator In conventional detection systems, a scintillator usually has a circular cylindrical geometry to conform to a photomultiplier tube detection head. A flat face of the cylinder provides an external surface of the scintillator for optically coupling to a light detection / amplification device such as the photomultiplier tube.
  • a scintillator In which detection of radiation from fluids in capillary feed systems is required, the prior art teaches a scintillator in which a small hole is drilled through a diameter of the cylindrical scintillator. Through this hole can be threaded a capillary for carrying fluids to be analysed by, for example, positron emission detection.
  • the prior art scintillator thereby provides a path for the capillary to traverse the photomultiplier head, and provides the requisite 4 ⁇ detection geometry over a substantial portion of the capillary within the scintillator.
  • This conventional design has a significant disadvantage in that a free end of the capillary must be available to thread through the hole in the scintillator. This is particularly disadvantageous in various chemical analysis systems for a number of reasons.
  • the present invention provides an improved scintillation head suitable for installation of a fluid feed capillary.
  • the present invention provides a scintillator for a photomultiplier tube, the scintillator comprising a block of scintillator material having a first face adapted for optically coupling to a photomultiplier tube and a body extending away from the first face, the body including a channel having a length extending across a full width of the block and having a depth extending into the block, the cross- sectional profile of the channel walls including a curved portion between the top of the channel and the base of the channel.
  • Figure 1 shows a perspective view of a scintillator element according to the invention with capillary installed
  • Figure 2 shows a cross-sectional view on line A— A of the scintillator element of figure 2;
  • Figure 3 shows a schematic side view of a photomultiplier and detector assembly incorporating the scintillator element of figure 2;
  • Figure 4 shows a schematic front view of a photomultiplier and detector assembly of figure 4;
  • Figure 5 shows a front view of a detector system and capillary feed using the scintillator element of figure 1 ;
  • Figure 6 shows a side view of the detector system of figure 5.
  • the scintillator element comprises a circular cylindrical block 2 which includes a lower face 3 which is adapted for optically coupling to a light detection and/or amplification device such as a photomultiplier tube.
  • a light detection and/or amplification device such as a photomultiplier tube.
  • the curved cylindrical form of block is preferred to correspond with the photomultiplier head, but other shapes may be used.
  • the block 2 defines a channel 4 into which a capillary may be inserted at the top 5 thereof.
  • the channel has a length which extends across a full width of the block so that ends of the capillary can emerge from both edges of the block when at any depth in the channel.
  • the channel 4 has a base 6 which extends through the centre of the block.
  • the base 6 of the channel extends diametrically across the block 2 and resides mid way between the lower face 3 and an upper face 7.
  • the capillary 9 can be drawn down to the base 6 of the channel from the top 5 without requiring a free end for threading through the scintillator element 1.
  • the cross-sectional profile of the channel 4 as defined by the channel walls 11, 12 particularly as viewed in figure 2 includes a curved portion between the top of the channel and the base of the channel.
  • the curved cross-sectional profile of the channel ensures that 4 ⁇ detection geometry is provided over a substantial proportion of the length of the channel in which a capillary resides.
  • the curvature is sufficient such that there is no line of sight from any part of the base 6 of the channel to the top 5 of the channel.
  • the scintillator element measures 9 mm in diameter and has a thickness of 5 mm.
  • the channel is a "J" shape and has a channel width of approximately 300 ⁇ m.
  • the base 6 of the channel 4 is preferably displaced laterally from the top of the channel (ie. from the plane defined by the initially straight sidewalls of the upper portion of the channel) by a distance which is at least several times the channel width, and typically 2 to 3 mm.
  • the scintillator is preferably formed of plastics material, such as Bicron 412, as supplied by Bicron, Newbury, Ohio, USA. Such scintillator materials can be very brittle and thus difficult to machine without damaging the material. Polished, highly reflective surfaces are required, without surface blemishes which scatter scintillated light. It has been found that stressing such materials during machining can cause stress fractures within the material which result in light scattering sites throughout the volume of scintillator material. This reduces the optical efficiency of the scintillation head.
  • the scintillator element is therefore preferably fabricated in two parts, 14 and 15.
  • the first of these parts 14 has a lateral face which essentially defines the right hand side wall 12 of the channel as viewed in figure 2, and this face extends down the channel and around to form an upper mating surface 16.
  • the second of the two parts 15 has a lateral face which essentially defines the left hand side wall 11 of the channel as viewed in figure 2, and this face extends down the channel and around to form a lower mating surface 17. Both faces are machined and polished to an appropriate optical quality and can then be assembled by engagement of the upper and lower mating surfaces 16, 17 using an appropriate optically conductive cement or adhesive, such as Bicron BC600.
  • the machining and polishing of the channel walls and mating surfaces is preferably carried out to a degree so as to substantially eliminate scattering of scintillated light from the surfaces thereof.
  • the transition from channel wall 11, 12 to respective mating surface 17, 16 may include a stepped or differently curved transition 18 where the channel walls come together so as to provide a rounded or rectangular cross-sectional profile of the base of the channel either to correspond to the capillary size and cross-sectional profile.
  • the transition from channel wall 11, 12 to respective mating surface 17, 16 may be smooth without significant deviation from the curvature of the channel, in which case the channel base 6 will be tapered.
  • the outer surfaces of the scintillator element are preferably coated with a silvered reflective covering to ensure that scintillated light is reflected back into the body of the scintillator and to reduce background light from the scintillator.
  • the scintillator is also coated with a radiation absorbing material such as lead to reduce background interference.
  • the scintillator and capillary fluid delivery system are preferably housed within a light tight and radiation absorbent housing to minimise noise arising from background light and background radiation.
  • a tufnel cover 21 an exemplary assembly of photomultiplier tube 20 and scintillator element 1 is shown, the scintillator element 1 being clamped to the photomultiplier head 20 by a tufnel cover 21.
  • the cover 21 is formed in two parts so as not to overlay the channel top 5 to allow ingress and egress of a capillary.
  • FIGS 6 and 7 show an exemplary detection system assembly 25 for use in capillary electrophoresis in which capillary 9 is fed through the scintillation head 1 and thence into a buffer outlet reservoir 26.
  • the photomultiplier tube 20 is secured to the back wall 27 of a light-tight chamber 28.
  • the 4 ⁇ geometry scintillator element as described above is found to provide an efficiency of the order of 88% for the detection of carbon 11, contrasted with a figures of between 40 and 80% for prior art 4 ⁇ scintillation elements.

Abstract

A scintillator for use with a photomultiplier or other light detection/amplification apparatus comprises a block of scintillator material (2) having a first face (7) adapted for optically coupling to the photomultiplier tube and a body extending away from the first face. The body includes a channel (5) having a length extending across a full width of the block and having a depth extending into the block. The cross-sectional profile (Fig. 2) of the channel walls includes a curve over at least a portion thereof. The scintillator allows insertion of a capillary (9) therein for conveyance of radioactive fluids therethrough and provides 4π detection geometry to optimise sensitivity.

Description

SCINTTT ATION HEAD
The present invention relates to the detection of radioactivity in fluids, and in particular relates to the design of scintillators suitable for use with a radiation detection system.
The scintillator design is applicable to capillary-based fluid delivery systems and the invention has particular application, though not exclusively so, to capillary electrophoresis, flow injection analysis and capillary liquid chromatography, incorporating the analysis of fluid based compounds labelled with positron-emitting radio-nuclides. Typically, the radio-nuclides are of the β- or γ-emitting variety.
In conventional detection systems, a scintillator usually has a circular cylindrical geometry to conform to a photomultiplier tube detection head. A flat face of the cylinder provides an external surface of the scintillator for optically coupling to a light detection / amplification device such as the photomultiplier tube. Where detection of radiation from fluids in capillary feed systems is required, the prior art teaches a scintillator in which a small hole is drilled through a diameter of the cylindrical scintillator. Through this hole can be threaded a capillary for carrying fluids to be analysed by, for example, positron emission detection.
The prior art scintillator thereby provides a path for the capillary to traverse the photomultiplier head, and provides the requisite 4π detection geometry over a substantial portion of the capillary within the scintillator. This conventional design has a significant disadvantage in that a free end of the capillary must be available to thread through the hole in the scintillator. This is particularly disadvantageous in various chemical analysis systems for a number of reasons.
Firstly, it is often necessary to maintain the ends of the capillary in particular chemical or electrolyte buffer reservoirs. Removal of the capillary from a reservoir to feed it through a scintillator head is inconvenient, time consuming and may result in a necessity to re-prime the fluid delivery system or re-initiate the experiment, and may easily result in damage to the capillary or detector.
Secondly, where hazardous substances, particularly those including radio-nuclides of high specific activity, are being passed through the capillary, it is most desirable to minimise occasions on which the "closed" system must be "opened" (eg. removal of a capillary end from a reservoir) simply to apply the detection system. Such an operation introduces a high risk of spillage of radioactive material and contamination of personnel and equipment.
A simple arrangement of a cylindrical scintillator with a diametric slot cut through it has been proposed. While this enables easy insertion and removal of the capillary without needing a free end available, and is readily machinable in a scintillator material, it is found that a significant loss of signal and reduction in detection efficiency occurs owing to the loss of full 4π detection geometry around the capillary.
The present invention provides an improved scintillation head suitable for installation of a fluid feed capillary. According to one aspect, the present invention provides a scintillator for a photomultiplier tube, the scintillator comprising a block of scintillator material having a first face adapted for optically coupling to a photomultiplier tube and a body extending away from the first face, the body including a channel having a length extending across a full width of the block and having a depth extending into the block, the cross- sectional profile of the channel walls including a curved portion between the top of the channel and the base of the channel.
Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which:
Figure 1 shows a perspective view of a scintillator element according to the invention with capillary installed;
Figure 2 shows a cross-sectional view on line A— A of the scintillator element of figure 2;
Figure 3 shows a schematic side view of a photomultiplier and detector assembly incorporating the scintillator element of figure 2; Figure 4 shows a schematic front view of a photomultiplier and detector assembly of figure 4;
Figure 5 shows a front view of a detector system and capillary feed using the scintillator element of figure 1 ;
Figure 6 shows a side view of the detector system of figure 5.
With reference to the figures, a presently preferred embodiment of a scintillator element 1 according to the invention will now be described. The scintillator element comprises a circular cylindrical block 2 which includes a lower face 3 which is adapted for optically coupling to a light detection and/or amplification device such as a photomultiplier tube. The curved cylindrical form of block is preferred to correspond with the photomultiplier head, but other shapes may be used.
The block 2 defines a channel 4 into which a capillary may be inserted at the top 5 thereof. The channel has a length which extends across a full width of the block so that ends of the capillary can emerge from both edges of the block when at any depth in the channel. The channel 4 has a base 6 which extends through the centre of the block. Thus in the preferred embodiment shown, the base 6 of the channel extends diametrically across the block 2 and resides mid way between the lower face 3 and an upper face 7. The capillary 9 can be drawn down to the base 6 of the channel from the top 5 without requiring a free end for threading through the scintillator element 1.
It will be seen that the cross-sectional profile of the channel 4 as defined by the channel walls 11, 12 particularly as viewed in figure 2 includes a curved portion between the top of the channel and the base of the channel. The curved cross-sectional profile of the channel ensures that 4π detection geometry is provided over a substantial proportion of the length of the channel in which a capillary resides. Preferably the curvature is sufficient such that there is no line of sight from any part of the base 6 of the channel to the top 5 of the channel.
In a preferred embodiment of the cylindrical configuration, for positron emission detection from fluids in capillaries of 50 μm internal diameter, the scintillator element measures 9 mm in diameter and has a thickness of 5 mm. The channel is a "J" shape and has a channel width of approximately 300 μm.
As seen in the drawings, the base 6 of the channel 4 is preferably displaced laterally from the top of the channel (ie. from the plane defined by the initially straight sidewalls of the upper portion of the channel) by a distance which is at least several times the channel width, and typically 2 to 3 mm.
The scintillator is preferably formed of plastics material, such as Bicron 412, as supplied by Bicron, Newbury, Ohio, USA. Such scintillator materials can be very brittle and thus difficult to machine without damaging the material. Polished, highly reflective surfaces are required, without surface blemishes which scatter scintillated light. It has been found that stressing such materials during machining can cause stress fractures within the material which result in light scattering sites throughout the volume of scintillator material. This reduces the optical efficiency of the scintillation head.
To achieve adequate optical qualities of the scintillator element, it is therefore preferably fabricated in two parts, 14 and 15. The first of these parts 14 has a lateral face which essentially defines the right hand side wall 12 of the channel as viewed in figure 2, and this face extends down the channel and around to form an upper mating surface 16. The second of the two parts 15 has a lateral face which essentially defines the left hand side wall 11 of the channel as viewed in figure 2, and this face extends down the channel and around to form a lower mating surface 17. Both faces are machined and polished to an appropriate optical quality and can then be assembled by engagement of the upper and lower mating surfaces 16, 17 using an appropriate optically conductive cement or adhesive, such as Bicron BC600.
The machining and polishing of the channel walls and mating surfaces is preferably carried out to a degree so as to substantially eliminate scattering of scintillated light from the surfaces thereof.
The transition from channel wall 11, 12 to respective mating surface 17, 16 may include a stepped or differently curved transition 18 where the channel walls come together so as to provide a rounded or rectangular cross-sectional profile of the base of the channel either to correspond to the capillary size and cross-sectional profile. Alternatively, the transition from channel wall 11, 12 to respective mating surface 17, 16 may be smooth without significant deviation from the curvature of the channel, in which case the channel base 6 will be tapered.
The outer surfaces of the scintillator element, with the exception of lower surface 3 are preferably coated with a silvered reflective covering to ensure that scintillated light is reflected back into the body of the scintillator and to reduce background light from the scintillator. Preferably, the scintillator is also coated with a radiation absorbing material such as lead to reduce background interference.
The scintillator and capillary fluid delivery system are preferably housed within a light tight and radiation absorbent housing to minimise noise arising from background light and background radiation. With reference to figures 4 and 5, an exemplary assembly of photomultiplier tube 20 and scintillator element 1 is shown, the scintillator element 1 being clamped to the photomultiplier head 20 by a tufnel cover 21. The cover 21 is formed in two parts so as not to overlay the channel top 5 to allow ingress and egress of a capillary.
Figures 6 and 7 show an exemplary detection system assembly 25 for use in capillary electrophoresis in which capillary 9 is fed through the scintillation head 1 and thence into a buffer outlet reservoir 26. The photomultiplier tube 20 is secured to the back wall 27 of a light-tight chamber 28.
The 4π geometry scintillator element as described above is found to provide an efficiency of the order of 88% for the detection of carbon 11, contrasted with a figures of between 40 and 80% for prior art 4π scintillation elements.

Claims

1. A scintillator for a photomultiplier tube comprising a block of scintillator material having a first face adapted for optically coupling to a photomultiplier tube and a body extending away from the first face, the body including a channel having a length extending across a full width of the block and having a depth extending into the block, the cross- sectional profile of the channel walls including a curved portion between the top of the channel and the base of the channel.
2. The scintillator of claim 1 in which the cross-sectional profile of the channel walls is such that there is no line of sight from any part of the base of the channel to the top of the channel.
3. The scintillator of claim 1 in which the base of the channel passes substantially centrally through the body of the scintillator.
4. The scintillator of claim 1 in which the scintillator has substantially circular cylindrical geometry, one flat face of the cylinder providing the first face for optically coupling and the opposing flat face including the top of the channel, the base of the channel lying approximately mid way between the two cylinder faces.
5. The scintillator of claim 1 in which the base of the channel is displaced sideways from the plane defined by a sidewall of the channel adjacent the top of the channel by a distance which is at least several times the channel width.
6. The scintillator of claim 1 in which the body is formed in two parts, a first part having a lateral face forming one side wall of the channel and an extension thereof, and a second part having a corresponding lateral face foπning the other side wall of the channel and an extension thereof, the two extensions providing corresponding mating surfaces for assembly of the block.
7. The scintillator of claim 6 in which the mating surfaces are substantially orthogonal to a portion of the channel sidewall immediately adjacent to the top of the channel.
8. The scintillator of claim 6 in which the block is assembled using an optically transmissive cement or adhesive between the corresponding mating surfaces.
9. The scintillator of claim 6 in which the two lateral faces are polished to substantially eliminate light scatter therefrom.
10. A scintillator substantially as described herein and with reference to the accompanying drawings.
PCT/GB1999/001941 1998-06-23 1999-06-18 Scintillation head WO1999067656A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9813421.6A GB9813421D0 (en) 1998-06-23 1998-06-23 Scintillation head
GB9813421.6 1998-06-23

Publications (1)

Publication Number Publication Date
WO1999067656A1 true WO1999067656A1 (en) 1999-12-29

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004097454A2 (en) * 2003-04-30 2004-11-11 Hammersmith Imanet Ltd Detector for measuring radioactive fluid
US7641860B2 (en) 2006-06-01 2010-01-05 Nanotek, Llc Modular and reconfigurable multi-stage microreactor cartridge apparatus
US7797988B2 (en) 2007-03-23 2010-09-21 Advion Biosystems, Inc. Liquid chromatography-mass spectrometry
US7854902B2 (en) 2006-08-23 2010-12-21 Nanotek, Llc Modular and reconfigurable multi-stage high temperature microreactor cartridge apparatus and system for using same
US7998418B1 (en) 2006-06-01 2011-08-16 Nanotek, Llc Evaporator and concentrator in reactor and loading system
WO2023213697A1 (en) * 2022-05-01 2023-11-09 Commissariat A L'energie Atomique Et Aux Energies Alternatives Device for estimating the activity of a radioactive liquid

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3035172A (en) * 1958-03-25 1962-05-15 Jr Clyde L Cowan Radiation counter
WO1995012825A1 (en) * 1993-11-03 1995-05-11 Packard Instrument Company, Inc. Flow cell for use in a flow scintillation analyzer
US5483070A (en) * 1994-08-02 1996-01-09 Packard Instrument Company Scintillation counter

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3035172A (en) * 1958-03-25 1962-05-15 Jr Clyde L Cowan Radiation counter
WO1995012825A1 (en) * 1993-11-03 1995-05-11 Packard Instrument Company, Inc. Flow cell for use in a flow scintillation analyzer
US5483070A (en) * 1994-08-02 1996-01-09 Packard Instrument Company Scintillation counter

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004097454A2 (en) * 2003-04-30 2004-11-11 Hammersmith Imanet Ltd Detector for measuring radioactive fluid
WO2004097454A3 (en) * 2003-04-30 2004-12-29 Hammersmith Imanet Ltd Detector for measuring radioactive fluid
US7641860B2 (en) 2006-06-01 2010-01-05 Nanotek, Llc Modular and reconfigurable multi-stage microreactor cartridge apparatus
US7790124B2 (en) 2006-06-01 2010-09-07 Nanotek, Llc Modular and reconfigurable multi-stage microreactor cartridge apparatus
US7998418B1 (en) 2006-06-01 2011-08-16 Nanotek, Llc Evaporator and concentrator in reactor and loading system
US7854902B2 (en) 2006-08-23 2010-12-21 Nanotek, Llc Modular and reconfigurable multi-stage high temperature microreactor cartridge apparatus and system for using same
US7797988B2 (en) 2007-03-23 2010-09-21 Advion Biosystems, Inc. Liquid chromatography-mass spectrometry
WO2023213697A1 (en) * 2022-05-01 2023-11-09 Commissariat A L'energie Atomique Et Aux Energies Alternatives Device for estimating the activity of a radioactive liquid

Also Published As

Publication number Publication date
GB9813421D0 (en) 1998-08-19

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