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A compact cost-effective beamline for a PET Cyclotron
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 261 (2007) 809–812 www.elsevier.com/locate/nimb
A compact cost-effective beamline for a PET Cyclotron M.P. Dehnel
a,*
, P. Jackle a, M. Roeder a, T. Stewart a, J. Theroux a, J.P. Brasile b, P. Sirot c, K.R. Buckley d, M. Bedue e
b
a D-Pace, P.O. Box 201, Nelson, B.C., Canada V1L 5P9 THALES Communications, 160 boulevard de Valmy – BP82, Colombes Cedex 92704, France c THALES Group, 1 boulevard Jean Moulin, Elancourt Cedex 78852, France d TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C., Canada V6T 2A3 e Laboratories CYCLOPHARMA, Biopole Clermont-Limagne, Saint-Beauzire 63360, France
Available online 2 April 2007
Abstract Most commercial PET Cyclotrons have targets mounted on or near the main cyclotron vacuum chamber. There is often little or no system capability for centering or focusing the extracted beam on target to achieve maximum production. This paper describes the ionoptics, design and development of a compact cost-effective beamline comprised of low activation and radiation resistant materials. The beamline, complete with suitable diagnostic devices, permits the extracted proton beam to be centered (X–Y steering magnet), and focused (quadrupole doublet) on target eliminating unnecessary beamspill and ensuring high production. 2007 Elsevier B.V. All rights reserved. PACS: 81.40.Wx; 87.58.Ji; 41.75.Ak; 41.85.p; 41.85.Lc; 87.58.Fg; 41.75.Ak; 41.75.Cn; 28.41.Qb Keywords: Beamline; Ion-optics; PET; Cyclotron; Radiation; Target; Shielding; Fluorine-18; Scintillator; Magnets; Quadrupole; Steering; Diagnostic; Proton; Focus; Bombardment; Beams; Radiopharmaceutical; Radioisotope
1. Introduction Most PET Cyclotrons mount targets at the periphery of the cyclotron vacuum chamber. This precludes the use of steering/focusing elements to adjust beam spot position/ shape on target. Such systems avoid the expense of beamline components, and, although radioisotope production may not be optimized, this situation is generally acceptable for low bombardment currents. THALES Communications is developing the AIMA PN PET H Cyclotron system to produce extracted beam currents in the few hundred micro-ampere range. In a PET radioisotope distribution centre this cyclotron can be configured with two identical compact beamlines that can be fitted with high-production targets [1,2] or standard
*
Corresponding author. Tel.: +1 250 352 5162; fax: +1 250 352 3864. E-mail address: [email protected] (M.P. Dehnel).
0168-583X/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.03.069
targets. The distance from the cyclotron to the beam strike location is 1.1 m. There are 7 beam current readback diagnostics, XY steering, a quadrupole doublet, a gate valve and vacuum system, a two-target selector, and radiation shielding around the targets. The beamline elements require little maintenance and incorporate low activation and radiation resistant materials following D-Pace’s philosophy [3–5]. The beamline provides the opportunity to centre and focus the beam in an instrumented and controlled manner. Maximization of radioisotope production is possible, and the chance of catastrophic beam loss on noncooled structures is minimized. This is of particular importance in the case of high power beams. It is also important that the primary source of residual radiation, the targets, are separated from the cyclotron and locally shielded. Thus, the cyclotron is less active, and dose to maintenance personnel working on the cyclotron is reduced. This paper describes the development, design, and features of this novel compact beamline for a PET Cyclotron.
810
M.P. Dehnel et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 809–812
Fig. 1. Experimental set-up for measuring beam spot images on quartz scintillators.
2. Beam measurements and ion-optics
3. Beamline system layout and features
Experiments were undertaken using the proto-type AIMA Cyclotron to characterize the extracted beam. Fig. 1 illustrates the experimental set-up. Measurements of the extracted 14 MeV proton beam on quartz scintillators were obtained at two locations. Fig. 2 gives an example of a beamspot image. Based on these images a conservative estimate of the beam half-divergences could be made. Beam half-size dimensions were estimated using the radius gain per turn for the horizontal, and the physical size of the extraction foil for the vertical. Fig. 3 illustrates the horizontal and vertical beam profiles. Based on TRIUMF PET group experience, a small percentage of the total beam current is spilled top/bottom/left/right at the target collimator so the beam is not over-focused risking foil rupture.
Fig. 4 shows an isometric view of the compact beamline system, and a description of items 1–10 follows.
Fig. 2. A 0.3 lA, 14 MeV beamspot at the Set-Up #1 location. The random white pixels are due to radiation damage of the CCD camera.
(1) The exit port flange and collimator connects the beamline to the cyclotron vacuum chamber. The bulk material is low activation aluminium, and regular maintenance items such as o-rings are avoided in the service connections where Atlas bi-metal AL/SS knife-edge flanges with metal seals are used [6]. The collimator provides beamspill protection for downstream enclosures, and through a beam current readback provides the operator with beam centering information. The water-cooled collimator is made from low activation, and low neutron producing graphite. Electrical isolation is provided through VespelTM insulators, and ceramic water breaks. The downstream face of the flange is recessed for the insertion of a VATTM valve. The valve is secured to the exit flange by the upstream bellows flange. All fasteners are non-magnetic SS316. (2) The aluminium VATTM valve provides vacuum isolation between the cyclotron chamber and the beamline. The valve has in/out limit switches and an ISO16 port to which the mechanical pump and gauges are attached. The beamline is short and offers high conductance, so the cyclotron pumping is sufficient to bring the beamline into the low 106 Torr range. (3) The XY steering magnet is 100 mm long and has an aperture of 82 mm square. It provides steering of ±5 mrad in the horizontal (X) and vertical (Y) planes. The magnet has a measured peak field in either plane
M.P. Dehnel et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 809–812
811
Fig. 3. The beam envelopes containing 50%, 90% and 99% of the beam intensity at 14 MeV are shown from cyclotron to target position (10 mm diameter). The quadrupole magnet settings are: VQ1 = 0.435 T, HQ2 = 0.49456 T.
(5)
(6)
(7)
Fig. 4. Isometric InventorTM model of the beamline.
(8) of 0.01664 T at an excitation of 6 A. It is constructed of C1010 steel, and heavy-build polyimide coated wire for radiation resistance. A KlixonTM thermalswitch provides an interlock signal should the magnet over-heat. This magnet is mounted on SS316 support bars fastened to the bellows upstream flange. (4) The bellows provides a vacuum envelope from the upstream valve to the quadrupole magnet beampipe, a means to accommodate any misalignment between the beamline and cyclotron, and a retraction function
facilitating equipment removal. The bellows are nonmagnetic SS316, and are located within the XY steering magnet aperture. The quadrupole magnets (doublet) each have a bore diameter of 75 mm and an effective length of 200 mm. The measured peak pole-tip field rises linearly as a function of excitation current to a maximum value of 0.5 T at 50.9 A. These water-cooled magnets are constructed of C1010 steel, and the coils are comprised of alternating layers of copper tape and mylar vacuum impregnated in epoxy. Thermal-switches mounted on each coil pancake provide an interlock signal in the event of over-heating. The quadrupole beampipe is fabricated from aluminium (low activation). The upstream seal to the bellows is through a double o-ring sliding seal. The downstream seal to the target selector is through an Atlas Technologies AL/SS weldneck to 4.62500 knife-edged ConflatTM flange [6]. The beamline support structures support the quadrupole doublet and the target selector, targets and shields. These low activation aluminium devices provide adjustment and alignment functions translationally and rotationally in XYZ. The target selector technology has been licensed from TRIUMF by D-Pace. It positions one of two targets on the beamline axis. The upstream portion is comprised of a bellows assembly that provides a vacuum envelope and the flexible linkage to permit a piston with mechanical stops and limit switches to position the targets. The downstream chamber of the device is fabricated from low activation aluminium and anodized for electrical isolation. The selector is water-cooled. It houses a low activation and low neutron generating graphite baffle with beam current readback, and four segment graphite collimators with
812
M.P. Dehnel et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 809–812
beam current readbacks upstream of each target. Beamspills reported to the control system by these diagnostic elements facilitate beam steering and focusing. (9) The proto-type beamline is configured with two standard TRIUMF water targets, licensed by D-Pace, for the irradiation of 18O enriched water with 30 lA of protons and subsequent production of 18F-fluoride [7] at 150 mCi/lA. High power targets are envisioned for future installations. The proton beam traverses a 0.025 mm low activation aluminium foil, which separates the beamline vacuum from atmosphere, a helium cooling channel, and then a 0.039 mm HavarTM foil prior to impinging on the water-volume (0.9 ml, ;12 mm · 8 mm deep) contained in a watercooled Niobium body with beam current readback. The water pressure remains below 500 psig. (10) Radiation shielding encloses the selector and targets. The shields attenuate the residual c intensity emanating from the targets by greater than a factor of 100. The left and right shields are removable (hoist on tracks in ceiling), and the support table upon which they sit is fixed. The shields are primarily composed of lead sheet housed in brushed aluminium containers with jogs, so that line of sight leakage is not permitted. The targets are located about 1.1 m from the cyclotron minimizing the activity in the cyclotron. The shields reduce exposure to maintenance when closed. 4. Conclusion A compact cost-effective well-instrumented beamline, comprised of low activation and radiation resistant materi-
als, capable of steering/focusing a beam onto a PET target for optimized radioisotope production has been described. This technology is particularly well suited to high current production machines, but may be applied more generally as well. Acknowledgements The authors wish to thank Philip Gardner and Ann Fong for fostering and facilitating this collaboration; THALES Communications, and Cyclopharma for the use of their respective facilities; the TRIUMF, Talvan, CMS alphatech, and Buckley’s machine shops; and (SICEAI) Western Economic Diversification Canada, and the BDC for financial support. References [1] T.J. Ruth, K.R. Buckley, K. Chun, S. Jivan, S.K. Zeisler, United States Patent, No. US 6,845,137 B2, 2005. [2] T. Stokely, G. Bida, M. Humphrey, J.M. Doster, B. Wieland, High Yield Thermosyphon Target for Production of 18F-Fluoride, WTTC11, Cambridge (in press). [3] M.P. Dehnel, A. Trudel, T.S. Duh, T. Stewart, Beamline developments in commercial cyclotron facilities, Nucl. Instr. and Meth. B 241 (2005) 655. [4] M.P. Dehnel, T. Stewart, T.S. Duh, Industrial Beamline Design for Radioisotope Production, CYC2004, Tokyo, 2004, p. 486. [5] M.P. Dehnel, R.J. Dawson, G.M. Stinson, R. Helmer, R. Keitel, D.J. Dale, E.W. Pattyn, A. Wilson, The design and operation of an industrial beam transport system for 15–30 MeV protons, IEEE Trans. Ind. Appl. 28 (6) (1992) 1384. [6] http://www.atlasuhv.com. [7] K.R. Buckley, TRIUMF Design Note, TRI-DN-06-7, 2006.
Nuclear Instruments and Methods in Physics Research B 261 (2007) 809–812 www.elsevier.com/locate/nimb
A compact cost-effective beamline for a PET Cyclotron M.P. Dehnel
a,*
, P. Jackle a, M. Roeder a, T. Stewart a, J. Theroux a, J.P. Brasile b, P. Sirot c, K.R. Buckley d, M. Bedue e
b
a D-Pace, P.O. Box 201, Nelson, B.C., Canada V1L 5P9 THALES Communications, 160 boulevard de Valmy – BP82, Colombes Cedex 92704, France c THALES Group, 1 boulevard Jean Moulin, Elancourt Cedex 78852, France d TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C., Canada V6T 2A3 e Laboratories CYCLOPHARMA, Biopole Clermont-Limagne, Saint-Beauzire 63360, France
Available online 2 April 2007
Abstract Most commercial PET Cyclotrons have targets mounted on or near the main cyclotron vacuum chamber. There is often little or no system capability for centering or focusing the extracted beam on target to achieve maximum production. This paper describes the ionoptics, design and development of a compact cost-effective beamline comprised of low activation and radiation resistant materials. The beamline, complete with suitable diagnostic devices, permits the extracted proton beam to be centered (X–Y steering magnet), and focused (quadrupole doublet) on target eliminating unnecessary beamspill and ensuring high production. 2007 Elsevier B.V. All rights reserved. PACS: 81.40.Wx; 87.58.Ji; 41.75.Ak; 41.85.p; 41.85.Lc; 87.58.Fg; 41.75.Ak; 41.75.Cn; 28.41.Qb Keywords: Beamline; Ion-optics; PET; Cyclotron; Radiation; Target; Shielding; Fluorine-18; Scintillator; Magnets; Quadrupole; Steering; Diagnostic; Proton; Focus; Bombardment; Beams; Radiopharmaceutical; Radioisotope
1. Introduction Most PET Cyclotrons mount targets at the periphery of the cyclotron vacuum chamber. This precludes the use of steering/focusing elements to adjust beam spot position/ shape on target. Such systems avoid the expense of beamline components, and, although radioisotope production may not be optimized, this situation is generally acceptable for low bombardment currents. THALES Communications is developing the AIMA PN PET H Cyclotron system to produce extracted beam currents in the few hundred micro-ampere range. In a PET radioisotope distribution centre this cyclotron can be configured with two identical compact beamlines that can be fitted with high-production targets [1,2] or standard
*
Corresponding author. Tel.: +1 250 352 5162; fax: +1 250 352 3864. E-mail address: [email protected] (M.P. Dehnel).
0168-583X/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.03.069
targets. The distance from the cyclotron to the beam strike location is 1.1 m. There are 7 beam current readback diagnostics, XY steering, a quadrupole doublet, a gate valve and vacuum system, a two-target selector, and radiation shielding around the targets. The beamline elements require little maintenance and incorporate low activation and radiation resistant materials following D-Pace’s philosophy [3–5]. The beamline provides the opportunity to centre and focus the beam in an instrumented and controlled manner. Maximization of radioisotope production is possible, and the chance of catastrophic beam loss on noncooled structures is minimized. This is of particular importance in the case of high power beams. It is also important that the primary source of residual radiation, the targets, are separated from the cyclotron and locally shielded. Thus, the cyclotron is less active, and dose to maintenance personnel working on the cyclotron is reduced. This paper describes the development, design, and features of this novel compact beamline for a PET Cyclotron.
810
M.P. Dehnel et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 809–812
Fig. 1. Experimental set-up for measuring beam spot images on quartz scintillators.
2. Beam measurements and ion-optics
3. Beamline system layout and features
Experiments were undertaken using the proto-type AIMA Cyclotron to characterize the extracted beam. Fig. 1 illustrates the experimental set-up. Measurements of the extracted 14 MeV proton beam on quartz scintillators were obtained at two locations. Fig. 2 gives an example of a beamspot image. Based on these images a conservative estimate of the beam half-divergences could be made. Beam half-size dimensions were estimated using the radius gain per turn for the horizontal, and the physical size of the extraction foil for the vertical. Fig. 3 illustrates the horizontal and vertical beam profiles. Based on TRIUMF PET group experience, a small percentage of the total beam current is spilled top/bottom/left/right at the target collimator so the beam is not over-focused risking foil rupture.
Fig. 4 shows an isometric view of the compact beamline system, and a description of items 1–10 follows.
Fig. 2. A 0.3 lA, 14 MeV beamspot at the Set-Up #1 location. The random white pixels are due to radiation damage of the CCD camera.
(1) The exit port flange and collimator connects the beamline to the cyclotron vacuum chamber. The bulk material is low activation aluminium, and regular maintenance items such as o-rings are avoided in the service connections where Atlas bi-metal AL/SS knife-edge flanges with metal seals are used [6]. The collimator provides beamspill protection for downstream enclosures, and through a beam current readback provides the operator with beam centering information. The water-cooled collimator is made from low activation, and low neutron producing graphite. Electrical isolation is provided through VespelTM insulators, and ceramic water breaks. The downstream face of the flange is recessed for the insertion of a VATTM valve. The valve is secured to the exit flange by the upstream bellows flange. All fasteners are non-magnetic SS316. (2) The aluminium VATTM valve provides vacuum isolation between the cyclotron chamber and the beamline. The valve has in/out limit switches and an ISO16 port to which the mechanical pump and gauges are attached. The beamline is short and offers high conductance, so the cyclotron pumping is sufficient to bring the beamline into the low 106 Torr range. (3) The XY steering magnet is 100 mm long and has an aperture of 82 mm square. It provides steering of ±5 mrad in the horizontal (X) and vertical (Y) planes. The magnet has a measured peak field in either plane
M.P. Dehnel et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 809–812
811
Fig. 3. The beam envelopes containing 50%, 90% and 99% of the beam intensity at 14 MeV are shown from cyclotron to target position (10 mm diameter). The quadrupole magnet settings are: VQ1 = 0.435 T, HQ2 = 0.49456 T.
(5)
(6)
(7)
Fig. 4. Isometric InventorTM model of the beamline.
(8) of 0.01664 T at an excitation of 6 A. It is constructed of C1010 steel, and heavy-build polyimide coated wire for radiation resistance. A KlixonTM thermalswitch provides an interlock signal should the magnet over-heat. This magnet is mounted on SS316 support bars fastened to the bellows upstream flange. (4) The bellows provides a vacuum envelope from the upstream valve to the quadrupole magnet beampipe, a means to accommodate any misalignment between the beamline and cyclotron, and a retraction function
facilitating equipment removal. The bellows are nonmagnetic SS316, and are located within the XY steering magnet aperture. The quadrupole magnets (doublet) each have a bore diameter of 75 mm and an effective length of 200 mm. The measured peak pole-tip field rises linearly as a function of excitation current to a maximum value of 0.5 T at 50.9 A. These water-cooled magnets are constructed of C1010 steel, and the coils are comprised of alternating layers of copper tape and mylar vacuum impregnated in epoxy. Thermal-switches mounted on each coil pancake provide an interlock signal in the event of over-heating. The quadrupole beampipe is fabricated from aluminium (low activation). The upstream seal to the bellows is through a double o-ring sliding seal. The downstream seal to the target selector is through an Atlas Technologies AL/SS weldneck to 4.62500 knife-edged ConflatTM flange [6]. The beamline support structures support the quadrupole doublet and the target selector, targets and shields. These low activation aluminium devices provide adjustment and alignment functions translationally and rotationally in XYZ. The target selector technology has been licensed from TRIUMF by D-Pace. It positions one of two targets on the beamline axis. The upstream portion is comprised of a bellows assembly that provides a vacuum envelope and the flexible linkage to permit a piston with mechanical stops and limit switches to position the targets. The downstream chamber of the device is fabricated from low activation aluminium and anodized for electrical isolation. The selector is water-cooled. It houses a low activation and low neutron generating graphite baffle with beam current readback, and four segment graphite collimators with
812
M.P. Dehnel et al. / Nucl. Instr. and Meth. in Phys. Res. B 261 (2007) 809–812
beam current readbacks upstream of each target. Beamspills reported to the control system by these diagnostic elements facilitate beam steering and focusing. (9) The proto-type beamline is configured with two standard TRIUMF water targets, licensed by D-Pace, for the irradiation of 18O enriched water with 30 lA of protons and subsequent production of 18F-fluoride [7] at 150 mCi/lA. High power targets are envisioned for future installations. The proton beam traverses a 0.025 mm low activation aluminium foil, which separates the beamline vacuum from atmosphere, a helium cooling channel, and then a 0.039 mm HavarTM foil prior to impinging on the water-volume (0.9 ml, ;12 mm · 8 mm deep) contained in a watercooled Niobium body with beam current readback. The water pressure remains below 500 psig. (10) Radiation shielding encloses the selector and targets. The shields attenuate the residual c intensity emanating from the targets by greater than a factor of 100. The left and right shields are removable (hoist on tracks in ceiling), and the support table upon which they sit is fixed. The shields are primarily composed of lead sheet housed in brushed aluminium containers with jogs, so that line of sight leakage is not permitted. The targets are located about 1.1 m from the cyclotron minimizing the activity in the cyclotron. The shields reduce exposure to maintenance when closed. 4. Conclusion A compact cost-effective well-instrumented beamline, comprised of low activation and radiation resistant materi-
als, capable of steering/focusing a beam onto a PET target for optimized radioisotope production has been described. This technology is particularly well suited to high current production machines, but may be applied more generally as well. Acknowledgements The authors wish to thank Philip Gardner and Ann Fong for fostering and facilitating this collaboration; THALES Communications, and Cyclopharma for the use of their respective facilities; the TRIUMF, Talvan, CMS alphatech, and Buckley’s machine shops; and (SICEAI) Western Economic Diversification Canada, and the BDC for financial support. References [1] T.J. Ruth, K.R. Buckley, K. Chun, S. Jivan, S.K. Zeisler, United States Patent, No. US 6,845,137 B2, 2005. [2] T. Stokely, G. Bida, M. Humphrey, J.M. Doster, B. Wieland, High Yield Thermosyphon Target for Production of 18F-Fluoride, WTTC11, Cambridge (in press). [3] M.P. Dehnel, A. Trudel, T.S. Duh, T. Stewart, Beamline developments in commercial cyclotron facilities, Nucl. Instr. and Meth. B 241 (2005) 655. [4] M.P. Dehnel, T. Stewart, T.S. Duh, Industrial Beamline Design for Radioisotope Production, CYC2004, Tokyo, 2004, p. 486. [5] M.P. Dehnel, R.J. Dawson, G.M. Stinson, R. Helmer, R. Keitel, D.J. Dale, E.W. Pattyn, A. Wilson, The design and operation of an industrial beam transport system for 15–30 MeV protons, IEEE Trans. Ind. Appl. 28 (6) (1992) 1384. [6] http://www.atlasuhv.com. [7] K.R. Buckley, TRIUMF Design Note, TRI-DN-06-7, 2006.