Introduction
The ISOTRACE™ Super-Conducting Cyclotron is PMB-Alcen’s redeveloped and modernized version of Oxford Instrument’s OSCAR superconducting cyclotron [1]. Its extracted 80+ mi-croamperes of 12 MeV protons are used for the production of PET radioisotopes. Following the philosophy of Dickie, Stevenson, Szlavik [2] for minimizing dose to personnel, and as developed by Dehnel et al [3,4], and Stokely et al [5], the ISOTRACE™ shall utilize an innovative, light-weight, integrated and self-supporting Mini-Beamline. This permits the relatively high residual radiation fields around PET targets to be moved ~1 metre away from the cyclotron, and facilitates the use of local shielding (around the targets) that limits prompt gammas and neutrons, but more importantly attenuates the residual target radiation, so that maintenance/research staff can work on the cyclotron in a relatively low activity environment. In addition, the mini-beamline for PET utilizes a compound quadrupole/steerer doublet that permits active and dynamic focusing/steering of the extracted proton beam for optimized production and minimized losses [3], so it improves on the successful work of Theroux et al [6]. The integrated beamline unit is extremely small, so that it is very unlike bulky traditional PET and SPECT beamlines that require substantial support structures, such as described by Dehnel in [7,8].
Material and Methods
The ISOTRACE™ cyclotron is pictured in FIG. 1. The exit port flange and gate valve to which the integrated mini-beamline for PET shall be mounted is shown. Immediately upstream of the exit port, hidden from view, is a 4 jaw collimator (called BPI for Beam Position Indicator) with spilled beam current readbacks to the control system. TABLE 1 shows the nominal beam emittance and Twiss parameter values at the exit port flange location. This ion-optical information is necessary to simulate ion beam transport, develop the mini-beamline, and determine a nominal tune (i.e. magnet settings).
Results and Conclusion
TABLE 2 shows the ion-optical system parameters. FIGS. 2 and 3 show the horizontal and vertical beam profiles. The Horizontally focusing Quadrupole magnet (HQ), and Vertically focusing Quadrupole magnet (VQ) aperture diameter, 33 mm, was chosen to give sufficient beam acceptance. The focusing strength is a function of BL, so the effective length, L = 150 mm, was chosen to ensure Bmax less than 0.3 Tesla, while keeping overall magnet mass down. The quad-rupole magnets are fitted with water-cooled compound coils in which the copper/mylar strip wound portion of each coil is a winding for the quadrupole focusing function, and the wire wound portion is for the steering function. To increase beam acceptance and provide additional section strength for the pipe support function, the internal aperture of the low-activation aluminium beam pipe and the external shape are in the shape of a cross. FIG. 4 shows the beam crosssection at the mid-point of the downstream quadrupole magnet, and illustrates the additional acceptance as compared to a round beampipe. In order to machine the interior profile, the pipe is comprised of two premachined pieces that are friction stirwelded together. FIG. 5 is an isometric of the mini-beamline for PET.
The four upstream HQ compound coils are excited with a 75A power supply for the horizontally focusing quadrupole magnet function, and a ± 10A power supply for a vertical steering function. The same power supplies are used for the four downstream VQ compound coils for the purpose of a vertically focusing quadrupole magnet function and horizontal steering function.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa.de:bsz:d120-qucosa-164794 |
| Date | 19 May 2015 |
| Creators | Dehnel, M. P., Jackle, P., Potkins, D., Stewart, T., Boudreault, G., Jones, T., Philpott, C. |
| Contributors | D-Pace, Inc.,, Helmholtz-Zentrum Dresden - Rossendorf,, PMB-Alcen,, Buckley Systems Ltd., |
| Publisher | Helmholtz-Zentrum Dresden - Rossendorf |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:conferenceObject |
| Format | application/pdf |
| Source | WTTC15 |
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